a) 2D or 3D imaging using a linear or planar array ...proximity they undergo (partial) intramolecular charge transfer upon excitation).1,3 The integration of a metal center to the

Supplementary Figure 1

Different photoacoustic tomography detection geometries using widefield excitation.

(a) 2D or 3D imaging using a linear or planar array respectively. (b) 3D imaging using hemi-spherical array. (c) 2D or 3D imaging using a circular or cylindrical array.

Nature Methods doi:10.1038/nmeth.3929


Physiological barriers encountered during molecular imaging.

Design of contrast agents for molecular PAI must consider both circulatory and cellular barriers, as well as the active targeting of cell surface receptors, transporters, metabolic enzymes or biochemical processes to provide the molecular readout.



Normalized absorption spectra of near-infrared dyes.

Methylene Blue, ATTO740, AlexaFluor750 (pH 7.2) and IRDye800CW (in PBS). Spectral data from http://www.spectra.arizona.edu/



The origin of the optical properties of graphene and carbon nanodiamonds.

(a) Schematic honeycomb structure of a single layer graphene and grapheme oxide sheet. (b) Schematic illustration of the density of electronic states (DOS) with respect to energy for graphene (k = wavevector). (c) Absorption spectra of monolayer graphene and bilayer graphene.1 (d) Schematic illustration of the nanodiamond structure and its nitrogen-vacancies (NV). The NV centers are characterized by electrons (six or five) in dangling orbitals on the three carbon atoms and the nitrogen atom neighboring the vacancy and can be either negatively charged (six electrons) or neutral (five electrons). The combinations and transformation of these orbitals leads to different electronic states which allow strong optical absorption at higher wavelengths. The diamond surface is terminated by functional groups and sp2 carbons to stabilize the particle. (e) Schematic illustration of the energy levels and related absorptions of negatively charged and neutral NV centers (solid lines: electronic energy levels, dashed lines: vibrational energy levels).2 (f) Absorption spectrum of radiation-damaged nanodiamonds suspended in DI water (O.D. = optical density).3

References: 1. Sun, Z. et al. Growth of graphene from solid carbon sources. Nature 468, 549–552 (2010). 2. Manson, N. B. & Harrison, J. P. Photo-ionization of the nitrogen-vacancy center in diamond. Diam. Relat. Mater. 14, 1705–1710 (2005). 3. Zhang, T. et al. Photoacoustic contrast imaging of biological tissues with nanodiamonds fabricated for high near-infrared absorbance. J. Biomed. Opt. 18(2), 026018–1 – 026018–6 (2013).



Absorption spectra of graphene oxide and single-walled carbon nanotubes modified with near-infrared dyes.

(a) Absorption spectra of unmodified graphene oxide (red line) and ICG-graphene oxide.1 (b) Absorption spectra of plain SWNT and with dyes (ICG and QSY) modified SWNT.2

References: 1. Wang, Y.-W. et al. Dye-enhanced graphene oxide for photothermal therapy and photoacoustic imaging. J. Mater. Chem. B 1, 5762 (2013). 2. De La Zerda, A. et al. Family of enhanced photoacoustic imaging agents for high-sensitivity and multiplexing studies in living mice. ACS Nano 6, 4694–4701 (2012).



Optical properties of polymer nanoparticles.

(a) Schematic illustration of the components of polymer nanoparticles and the different methods of formulation. In green are the units that allow us to influence the optical properties of the polymer nanoparticles. (b) The effect of the conjugation length, attachment or incorporation of donor and acceptor units, metal complexation and aggregations during PNP formation on the optical properties. HOMO and LUMO stand for the highest occupied and lowest unoccupied molecule orbital. The extension of the conjugation length causes a bathochromic (red) shift. Not shown: sterically hindering substituents influence planarity of the backbone and thus decrease pi-overlap leading to blue shift.1,2 Donor/acceptor interaction leads to a decrease in the band gap yielding in a red shift (especially in close proximity they undergo (partial) intramolecular charge transfer upon excitation).1,3 The integration of a metal center to the porphyrin system influences the optical properties4 mainly due to the interactions of the d-orbitals of the metal with the molecular orbitals of the ligand. This enables ligand-to-metal transitions (LMCT), metal-to-ligand transitions (MLCT), metal-centered (MC) transitions and ligand-centered (LT) transitions. Electrostatic interactions between the conjugated cores lead to superstructures, known as more or less deformed H- or J-aggregates. In respect to the monomers, H-aggregation leads to a blue-shift (hypsochromic) and J-aggregation to a red-shift (bathochromic) of the pi-pi* transition.5

References: 1. Meier, H. Conjugated oligomers with terminal donor-acceptor substitution. Angew. Chemie - Int. Ed. 44, 2482–2506 (2005). 2. Ajayaghosh, A. Donor-acceptor type low band gap polymers: polysquaraines and related systems. Chem. Soc. Rev. 32, 181–191 (2003). 3. Slama-Schwok, a., Blanchard-Desce, M. & Lehn, J. M. Intramolecular charge transfer in donor-acceptor molecules. J. Phys. Chem. 94, 3894–3902 (1990). 4. Ho, I.-T., Sessler, J. L., Gambhir, S. S. & Jokerst, J. V. Parts per billion detection of uranium with a porphyrinoid-containing nanoparticle and in vivo photoacoustic imaging. Analyst 140, 3731–3737 (2015). 5. Pescitelli, G., Di Bari, L. & Berova, N. Application of electronic circular dichroism in the study of supramolecular systems. Chem. Soc. Rev. 43, 5211–33 (2014).


1

Supplementary Information

Contrast agents for molecular photoacoustic imaging.

Judith Weber1,2, Paul C Beard3* and Sarah E Bohndiek1,2*

Supplementary Notes

Supplementary Note 1: Key steps for image formation

Photoacoustic imaging (PAI) relies upon the generation of ultrasound waves via the absorption of modulated laser light by optically absorbing molecules or chromophores1. Recording of these waves at the tissue surface enables reconstruction of an image from the detected signals.

The signal generation process comprises several distinct processes. Initially, incident photons are absorbed by endogenous tissue chromophores or an exogenous contrast agent. Fast non-radiative conversion to heat then occurs resulting in a small temperature rise, typically <0.1K. The thermalization depends on the absorbing medium: for endogenous tissue chromophores or small molecule based contrast agents, it is by vibrational and collisional relaxation, whereas for metallic nanostructures it is via a series of electron-phonon interactions. If the laser pulse duration is less than a few tens of nanoseconds, the optical energy is deposited before significant thermal diffusion or acoustic propagation can occur and an isochoric initial pressure distribution is produced throughout the irradiated tissue volume. This initial pressure distribution P0 subsequently relaxes resulting in the emission of weak, broadband ultrasonic waves at MHz frequencies that travel to the tissue surface where they are detected. The detected photoacoustic signals provide an image of P0 and with some assumptions, this image can be taken to represent the distribution of absorbed optical energy. Photoacoustic image contrast is therefore said to be absorption based. This is why for example, photoacoustic imaging is well suited to visualizing vascular anatomy; the strong optical absorption of hemoglobin compared to other biomolecules enables blood vessels to be visualized with high contrast relative to the surrounding tissues.

Understanding the optical and thermodynamic interactions underlying the signal transduction mechanism is key to the design and selection of an effective contrast agent. The critical requirement is that the contrast agent signal is sufficiently large relative to the background signal provided by endogenous molecules to be unambiguously detected. Both optical and acoustic factors contribute to the final signal-to-noise ratio.

The magnitude and spectral profile of the specific extinction coefficient are the criteria that determine the level of optical absorption at a given wavelength. Ideally, a contrast agent should have a high specific extinction coefficient within the so-called ‘near-infrared window’ (620 - 950 nm), where absorption due to endogenous molecules (see Fig. 1) is relatively low. The spectral profile of the extinction coefficient should be sharply peaked to enable unambiguous identification of the presence and concentration of the contrast agent. An important attribute of PA molecular imaging is the ability to achieve this by acquiring data at multiple wavelengths to sample the spectral profile, followed by image processing to retrieve a signal that is specific for the contrast agent of interest. The simplest approach is to compare images acquired at the peak wavelength of the contrast agent before and after


2

injection. More sophisticated approaches often apply multivariate statistical methods referred to generally as ‘spectral unmixing’ (for example, linear regression) to improve discrimination.2 Nonetheless, those agents with broad spectra are often difficult to identify even with multivariate approaches since they often overlap with the spectrum of hemoglobin and can also be erroneously fitted to systematic noise.2

Following the absorption of photons by the contrast agent, the photoacoustic generation efficiency (conversion of the absorbed optical energy to pressure) then determines the magnitude of the acoustic emission. To achieve this, absorbed photons must be thermalized without significant radiative decay and the resulting thermal energy should be efficiently converted to pressure. The former is characterized by the quantum yield and the latter by the photoacoustic efficiency Γ. Γ depends on the absorber and the propagation medium. If both have the same thermodynamic properties (a reasonable assumption for endogenous tissue chromophores and organic dye-based contrast agents), Γ is represented simply by the Grueneisen coefficient, which is a function of the bulk modulus, specific heat and sound speed. When the absorber is a nanoparticle based contrast agent the light is absorbed by the particles and the heat conducted to the surrounding tissue. The efficiency is then no longer defined by the Grueneisen coefficient alone with the interfacial thermal resistance becoming an important contributing factor.

A photoacoustic image can be formed in several ways3,1. The most flexible approach is referred to as photoacoustic tomography (PAT). In PAT, a relatively large tissue volume (cm3) is flood illuminated using a wide-field laser beam using wavelengths within the near infrared (NIR) window. Light is scattered within the tissue, bathing it in diffuse light and generating PA waves wherever the light is absorbed. These waves are then detected over the surface using either an array of ultrasound receivers or a single mechanically scanned detector; Supplementary Fig. 1 illustrates several common preclinical PAT detection geometries. Based on the distribution of the PA waves across the surface and their time-of-arrival, a computer algorithm (e.g. based on backprojection principles) is used to reconstruct an image. The penetration depth of PAT is typically limited to <4cm in vivo by optical and acoustic attenuation. Spatial resolution is ultimately defined by frequency-dependent acoustic attenuation and is therefore depth dependent, ranging from a few tens of microns for mm depths to several hundred microns for cm depths. Optical resolution photoacoustic microscopy (OR-PAM) employs a different approach, whereby a focused excitation beam is scanned across the tissue target. Lateral resolution is defined by the spot size of the beam, which can be of the order of a few microns, but penetration depth is limited to less than 1mm due to optical scattering. Ongoing research will seek to push the boundaries of penetration depth and acoustic limits (including mitigating interference from air and bone) with more advanced instrumentation and image reconstruction algorithms.

Supplementary Note 2: Contrast agent synthesis routes and methods to tailor optical absorption properties for PAI Given that nanostructures are not often available as commercial products, we review here the common synthesis routes and functionalization chemistry for attachment of targeting moieties.


3

Gold nanoparticles (GNPs)

A simple and reproducible method to generate solid gold nanoparticles (GNPs) with controlled shapes and morphologies is the seed-mediated synthesis, whereby rapid reduction of a precursor metal ion solution, leading to spherical seed particles of 1-5 nm, is followed by controlled combination with a growth solution. For spherical GNPs, this often results in particle diameters >100 nm with uneven surfaces, which limits their biomedical applications. However, the size of the gold seeds and the molar ratio addition of stabilizer in the growth solution can tailor the shape and size of the final NP into various geometries. 4–6

Uncapped and unstabilized GNPs tend towards: aggregation; in vivo accumulation by the reticuloendothelial system; and non-specific binding to biomolecules (due to their charged surface), which can cause cytotoxic effects. Fortunately, gold forms strong gold-thiolate bonds (Au-S, binding energy ~50 kcal/mol) that enable covalent surface modification.7 Thiol-terminated poly(ethylene glycol) (PEG) improves the biocompatibility7 and enables further functionalization, such as encapsulation by silica to enhance photostability and increase PA signal.8,9

The localized surface plasmon resonance (LSPR) frequency of GNPs can be tuned based on: size (surface-to-volume ratio); polarization modes; edge / vertex number; and ‘sharpness’ of the GNP. Anisotropic and branched gold nanostructures including stars, tripods, plates and prism shapes have been synthesized (Supplementary Table 2) to tune these parameters, again mostly by seed mediated methods.10 A key example of LSPR tuning for PAI is found in gold nanorods (GNRs) (see Fig. 5a, longitudinal LSPR). A two-step seed-mediated Ag+- and cetyltrimethylammonium bromide (CTAB)-assisted method gives precise and well controlled production of GNRs. Based on the reaction conditions, shape (via CTAB), size, yield (by Ag+) and monodispersity (also Ag+) can be tailored.11 CTAB is crucial for colloidal stability4,12 but is toxic in vivo13–16. For biocompatibility, CTAB has to be removed while maintaining stability, often achieved with PEG or amphiphilic ligands.17,18

Gold nanoshells (GNSs) are thin metallic gold shells (< 150 nm) grown on a silica core.19,20 The larger size is a limitation for biocompatibility of GNSs. Alternative core materials including semiconductor quantum dots, metal oxides and liposomes can be used to produce smaller (15 – 60 nm), monodisperse and multifunctional GNSs, but the syntheses tend not to scale to large quantities.21–23 Gold nanocages (GNCs) are cubic NPs (< 50 nm) with porous walls, which can be produced in large quantities with high accuracy.24,25 Hence for theranostic applications (delivering pharmaceutical payloads upon diagnosis) using gold, GNCs appear most promising.

Carbon nanoparticles (CNPs)

Graphene is a two-dimensional sheet of sp2-carbon atoms packed in a hexagonal crystal lattice (Supplementary Fig. 5a) forming an extended conjugated system. The electronic properties of ideal single-layer graphene behave as a zero band gap semiconductor, which means that the distance between the highest occupied and lowest unoccupied energy band overlap at a so called Dirac point. The properties of the electronic states close to the Dirac point (Supplementary Fig. 5b) lead to a relatively broad featureless spectrum in the NIR (Supplementary Fig. 5c).26,27


4

Graphene is produced by mechanical or physico-chemical exfoliation of bulk graphite28–30 or reduction of graphene oxide31 (obtained by Hummers method) but this often results in a mixture of differently layered nano-structures containing structural or chemical defects, with limited reproducibility. The highest quality graphene is currently obtained by chemical vapor deposition,32 which at present is not suitable for large scale synthesis. Also, microwave-assisted synthesis appears promising for in vivo PAI as it produces more uniform graphene sheets.33

Single-walled carbon nanotubes (SWNT) can be synthesized based on graphite by arc-discharge34 or laser ablation35 in the presence of metallic catalysts (Fe, Co or Ni). An alternative method utilizes hydrocarbon gases and metal catalysts as seeds for the nanotube growth. The growth direction and the pattern growth of the nanotubes can be controlled by van der Waals interactions with substrates (e.g. silicon pots) or by an applied electric field to form more homogenous materials.36 However, none of the three synthesis methods yields pure, homogenous and chiral (described by twist angle along the tube axis, Fig. 6a) materials36 complex purification and separation procedures are required, representing a major challenge.37,38

Carbon nanodiamonds (ND) are composed of sp3 hybridized carbon atoms forming a rigid diamond structure with tetrahedral symmetry (Supplementary Fig. 5d). In a pure diamond lattice, all four valence electrons are involved in σ-bonds producing a large electronic band gap, which does not allow NIR absorption. By introducing vacancies into the diamond crystal lattice (e.g. a substitutional nitrogen atom next to a missing carbon atom) additional energy levels can be created (Supplementary Fig. 5e) to enable absorption in the NIR range (Supplementary Fig. 5f) and improve resistance to photobleaching.39,40,41 Zhang et al created ND with a high concentration of neutral vacancies giving absorption in the NIR with up to 99% non-radiative decay and PA maxima at 700 nm and 820 nm.42 The high thermal conductivity provides a PAI signal in vivo that surpasses GNR and SWNT (on a per atom basis).42 Fluorescent ND (mostly with negatively charged NV centers) have also been conjugated to gold nanoparticles that quench their fluorescence and yield high PAI signal.43

Carbon nanodiamonds (ND) are commonly synthesized by detonation44, chemical vapor deposition45 and high pressure high temperature (HPHT) processes46 and in general entail nitrogen impurities. For example, high-energy particle irradiation and vacuum annealing yields in neutral and negatively charged nitrogen-vacancies (NV).

Covalent functionalizations47–50 offer an extensive toolkit for modifying the stability and conjugation properties of CNPs. While they are usually stable, covalent modifications often interfere with the physical properties; introducing branched species can minimize the effect on the carbon framework.51 NDs have a distinct advantage compared to SWNT and graphitic NP in this regard, since the sp3 carbons allow covalent attachment of many functional groups without changing the intrinsic properties of the core.52 CNPs can also be functionalized in a non-covalent manner by means of π-π-stacking, hydrophobic and Van der Waals’ interactions. Common agents used for non-covalent modifications are small molecules (dyes53, drugs54, surfactants55), polymers53 and biomolecules56. These modifications can increase solubility and stability57, form micelles57 or function as anchor point for targeting53, signaling58 or therapeutic59 moieties. However, non-covalent modifications often suffer insufficient stability, requiring a trade-off between structural integrity and stability in making modifications to carbon NPs.


5

Polymers and Encapsulations

The synthesis of conjugated polymer NPs (CPNP) can be divided into two parts: polymerization (by oxidative polymerization, Suzuki-, Heck-, Sonogashira-coupling) and NP formation (by self-assembly, emulsion and nano-precipitation (Supplementary Fig. 7).60,61 Polypyrrole NPs can be prepared through aqueous phase oxidative polymerization in the presence of polyvinyl alcohol as a stabilizing agent and FeCl3 as catalyst. Porphyrins derive from naturally occurring heme or chlorophylls but can also be produced by synthetic routes.62

The optical properties, strongly dependent on the transition between the highest occupied and lowest unoccupied molecule orbital of the conjugated core, can be tuned by adopting different backbone structures, combining different conjugated polymers and controlling aggregation and surface functionalization (Supplementary Fig. 7b).63–65 For porphyrins the optical properties may be tuned through the size and degree of conjugation of the π-system, the metal center (complexation causes structural and electronic changes and enables metal-ligand charge transfer) and the nature of substituents (donor-acceptor properties) at the periphery of the macrocycle (Supplementary Fig. 7a,b).66

The inherent hydrophobicity of the conjugated system requires functionalization of CPNPs to obtain biocompatibility, but this must be traded against stability, which is strongly based on hydrophobic forces. A simple, fast and effective option is encapsulating the CPNPs with water-soluble, biocompatible polymers (Supplementary Fig. 7a). Photostability and absorption efficiency depends on the concentration ratio of matrix to CP, the amphiphilicity and the molecular weight of the matrix.67,68

Polymers without intrinsic PA contrast but favorable biocompatibility can incorporate signaling compounds. The signaling compound can be incorporated into the shell structure69,70,71, encapsulated by the shell72,73 or chemically integrated into the polymer74–80. The synthesis of micelles and vesicles is usually based on self-assembly81 while the PA contrast is dependent on the integrated signaling compound.

Supplementary Note 3: Emerging contrast agents for PAI

The exploration of new materials for PAI is a rapidly expanding field, particularly focused on achieving smart and multi-modality contrast agents, further described in the main manuscript. Some novel contrast agent classes are emerging.

Perfluorocarbon (PFC)

Perfuorocarbon (PFC) nanodroplets contain a liquid perfuorocarbon core, usually perfluoropentane or perfluorohexane, enriched with a signaling compound (and optionally therapeutics) and surrounded by a stabilizing shell of proteins, lipids, polymers or plasmonic nanoparticles, which can be further modified. The three-step production process begins with synthesis of the signaling compound followed by resuspension in liquid PFC and finally encapsulation with the stabilizing material. During PAI, the pulsed laser irradiation nucleates the liquid-to-gas transition of PFC (vaporization), which generates a photoacoustic transient with a significant higher PA signal amplitude (non-linear) than that associated with thermal expansion. Signaling compounds with high molar extinction coefficient in the NIR range are needed to lower the energy for initiate the vaporisation.82–88 The gaseous phase of the PFC


6

also provides ultrasound contrast. However, the evaporation process is irreversible and fast, which restricts application to short-term imaging – only the PA signal provided by added signaling compounds can remain for longer (dependent on photostability). Furthermore, their relatively large size (> 200 nm) at present limits their biomedical application to intravascular targets.

Iron oxide

Iron oxide nanocrystals have unique superparamagnetic properties and play an important role as contrast agents for MRI. For this use, the size of the iron oxide particles ranges from 60 to 180 nm and they are FDA approved (ferumoxides provided by Feridex in USA, Endorem in Europe).89 Although PAI has been performed with these larger agents90, most iron oxide based contrast agents for PAI are smaller than 40 nm.91 Iron oxide (magnetite) is a Fe2+-Fe3+ mixed-valence metal with intervalence charge transference allowing thermally induced electronic transition and a broad absorption spectrum in the visible and NIR region.92 However, the absorption of bare iron oxide decreases to a flat spectrum in the NIR range.93 Silica coating can improve this to some extent but further studies are needed to quantify the optimal ratio between core size and shell-thickness.94 Iron oxide can be encapsulated by a polymer shell to form NPs and conjugated to both targeting moieties95–97 and additional signaling compounds such as graphene oxide98 to increase the PA signal. Taking advantage of the superparamagnetic properties and the PA signal, iron oxide NPs have been used for multi-modality imaging with MRI and US 98,99 as well as in magnetomotive PAI, used to reduce background22,97.

Copper

Copper sulphide (CuS) NPs are semiconductors exhibiting quantum size confinement phenomenon, which leads to a good absorption in the NIR range (extinction coefficient at 1,064 nm around 2.6 × 107 M-1 cm-1).100 They can be most simply synthesized out of CuCl2 and Na2S in the presence of sodium citrate yielding small citrate-coated CuS NPs (< 20 nm).100,101 By adjusting the stoichiometric ratio between CuCl2 and Na2S the absorption peak can be tuned towards longer wavelengths. In comparison to most of the other plasmonic NPs, this allows PAI at wavelengths over 1,000 nm (1,064 nm) with promising depth penetration in vitro and in vivo.100 The potential of molecular imaging with CuS has been demonstrated via a smart probes for PAI101. Since the radioactive isotope 64Cu or Ni ions102 can be integrated into the CuS core103 multi-modal imaging with PET or MRI is possible. While copper appears to have high potential, only a few in vivo studies of CuS NPs have been reported and thus information about biocompatibility are limited.


7

Supplementary Tables Table S1: Small molecule dyes reported for use in PAI. SLN = sentinel lymph node, GLUT = glucose transporter, RGD = arginylglycylaspartic acid, NMDA = N-methyl-D-aspartate, NPR-1 = natriuretic peptide receptor 1, HER2 = human epidermal growth factor receptor 2, EGFR = epidermal growth factor receptor, GRPR = gastrin releasing peptide receptor. Type Dye λ

(nm) Conjugation to

Target Cell line/ Tumor type Ref

Heptamethine cyanine dyes

Indocyanine green (ICG)

780 /

SLN

Sprague-Dawley rat 104

CDnir7 806 / Macro-phages

RAW 264.7 cells/inflam. mice, 4T1 tumors

105

IRDye800cw 774 2-deoxy glucose

GLUT A421 cells/tumor 106,10

7

IRDye800 792 Peptide (c(KRGDf))

Integrin αvβ3 U87 cells/tumor 108

IC-5-T 830 / Tumor accumulation

HeLa cells/tumor 109

IC7-1-Bu 823 / Tumor accumulation

HeLa cells/tumor 110

IR780 780 Caspase inhibitor

Caspase-9 DU145 cells/ MDA-1986 tumor

111

L1, L2 776 NMDAR antagonists

NMDA receptor

NSC-34 cells 112

Azo dyes

Methylene blue

664 / /

pO2 Sprague-Dawley rat hind limb tumor

113–

116

Evans blue 620 / Hsd:Athymic nude mice, Sprague-Dawley rat

117

Others e.g. Naphthalo-cyanine dyes

Alexa Fluor 750 (Structure not available)

750 / Peptide Peptide with

NPR-1 receptor Matrix-

Balb/c mice MCF-7, VEGF165 tumor FTC133 tumor

119 120 121

Na+

N+

N

SO

O-O

Indocyanine green

SO

O O

S

N

NCl

Methylene blue


8

118

black hole quencher Herceptin Peptide

metallo-proteases HER2 pH changes

MCF-7, BT-474, MCF-7-PC-DMA, MDA-MB-231 cell S2VP10(L), S2013(Q) cells/tumor

122 123

SNARF-5F carboxylic acid (Fluorone dye)

564 532

/ H+ Chicken breast 124,12

5

CF-750 (Structure not available)

755 EGF EGFR S2VP10, S2CP9 cells/S2VP10L tumor

126

ATTO740 (Structure not available)

740 Peptide Peptide Peptide

GRPR Furin Integrin αvβ6

PC3, LNCaP cells/PC3 tumor MDA-MB-231 cells/tumor, LoVo tumor A431 cells/tumor

127 128 129

SiNc (Naphthalo-cyanine dye)

770 / / HT29 tumor 118

Octabutoxy Naphthalocyanine

900 PEG, Sn(IV) chloride

/ ICR mice 130


9

Table S2: GNPs reported for use in PAI. Passive refers to the use of an untargeted contrast agent. N.s. = Not specified. EGFR = epidermal growth factor receptor, GSH = glutathione, PEG = polyethylene glycol, PLGA = poly(lactic-co-glycolic acid), ICAM-1 = intercellular adhesion molecule 1, HER2 = human epidermal growth factor receptor 2, TNF-α = tumor necrosis factor α, RGD = arginylglycylaspartic acid, MSH = Melanocyte-stimulating hormone, PSS = polystyrene sulfonate. Structure of GNP

λ (nm) Modification/ Comments

Target Cell line/Tumor type Ref.

Nano-sphere

131

720/ 532+ 680 multi-λ 520+620 765 532 680 – 860 700 680

anti-EGFR, PEG / Prussian Blue PEG Anti-EGFR, PEG Polyphosphazane Citraconic amide linker

EGFR GSH Passive Passive EGFR Passive Passive / pH

A431 cells/tumor / HT-29 cells/tumor BT474(ATCC) tumor FaDu cells/tumor C57BL/6J mice NIH 3T3, HeLa cells/ HeLa tumor

132,133

,134 135 136 137 138 139 140

Nanorod

131

multi-λ n.s. n.s. 800 808, 876 700 - 800 680 756 715, 800 780, 830 760 800, 1064 680 – 800 730-830 695 740

PEG, poly-glycerolsulfate PLGA-b-PEG, Cltx, Cy5.5 Bombesin, PEG Silica, PEG PNIPAAmMA, Fe3O4-NP anti-EGFR, PEG Silica / anti-ICAM-1, anti-E-selectin, PAA anti-HER2/EGFR, Silica, PEG anti-TNF-α, 125I anti-HER2/EGFR, PEG reduced graphene oxide amine polymer, anti-EGFR PEG, anti-MMP2 PEG, protein G, anti-HSP27, sec. antibody-FITC

L- + P-selectin Glioblastoma GRP receptor Passive Passive EGFR / Passive ICAM-1, E-selectin HER2, EGFR TNF-α HER2, EGFR / EGFR MMP2 HSP27

HUVEC/arthritis CIA mouse model U87-MG cells/tumor T47D cells A431 tumor C6 cells/tumor A431 cells MSC/MSC in female nu/nu mice MDA-435S xenograft HUVECs A431 cells, MCF7 cells Rat tail joints OECM1, Cal27 cells/tumor Matrigel mixture in female Balb/C mice MCF-7 cells/tumors Rabbit atherosclerosis model Sprague-Dawley rats

141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156

Nanostar

5

800 767 720

c(RGDyK), PEG / anti-CD44/CD44v6, PEG

Integrin αvβ3 SLN CD44/CD44v6

U87MG cells/tumor Sprague-Dawley rats MKN-45 cells/tumor

157 158 159

Nanotripod 700 c(RGDfC), PEG, Integrin αvβ3 U87MG cells/tumor 160


10

160

NOTA

Nanoprism

830 PEG Passive HT-29 cells/tumor 161

Nanocube

808 / Passive HepG2/S180 tumor 162

Nanoplate

1064 Silica, PEG SLN L3.6pl/Nu/Nu female mice – not tumor bearing

163

Nanocage

164

665, 685 770 638 730, 760 770 778 755

HPPH, PEG c(RGDyK), PEG / PEG Dye-cleavable peptide MSH /

Passive Integrin αvβ3 / SLN MMP MSH-receptor SLN

Colon-26 cells/tumor U87MG cells/tumor hMSC/U87-MG tumor Sprague-Dawley rats / B16 cells/melanoma Sprague-Dawley rats

165 166 167 164 168 169 170

Nanoshell

19

750 671 808

Iron oxide core Ce6 (inside), PEG c(KRGDf), PEG

Magneto-motive PAI ROS Integrin αvβ3

PVA phantom MDA-MB-435 cells/tumor U87-TGL tumor

22 171 172

Nanotubes

800 PSS coating / SW480+RAW 264.7/ HCT116 tumor

173


11

Table S3: CNPs reported for use in PAI. SLN = sentinel lymph node, RGD = arginylglycylaspartic acid, FA = folic acid, PEG = polyethylene glycol, LYVE1 = lymphatic vessel endothelial hyaluronan receptor 1, Carbon nanotube ring = CNTR. Structure of CNP


Target Cell line/ tumor type Ref.

Graphene (oxide) NP

174

650 532,675+ 753 808 720 780

Carbon NP, org. macromolecules on surface RhB, Cy5, Cy7, αvβ3-mAb ICG, FA Fluorination ICG, polydopamine

SLN Integrin αvβ3

FA-receptor / Passive

Adult nude mice U87-MG cells/tumor HeLa cells MCF-7 cells BEAS-2B, 4T1 cells/ 4T1-tumor

175 176 177 178 179

SWNTs

180

1064 Multi-λ 820 785,780 850 639,900 680-900 808

/ ICG, QSY21, c(RGDfC), PEG ICG, PEG ICG, c(RGD), PEG Gold layer, anti-LYVE-1 Gold layer, FA, PEG C(RGDyK), PEG CNTR, GNP-coating

/ Integrin αvβ3

SLN Integrin αvβ3

LYVE-1 FA receptor Integrin αvβ3

Passive

Athymic nude-Foxn1nu mice U87-MG cells/tumor Sprague-Dawley rats U87-MG cells/tumor T98G cells/nu/nu mice MDA-MB-231 cells/ nu/nu mice U87-MG cells/tumor U87MG cells/tumor

181 53 182 183 184 91 185 186

MWNTs

680-950 RGD-gold nanorods Integrin αvβ3

MGC803, GES-1 cells/ MGC803 tumor

187

Nanodiamonds

188

820 530,565 820 820

/ GNP anti-HER2, PEG anti-HER2

/ / HER2 HER2

Balb/c mice / Female BALB/c mice 4T1.2, 4T1.2 neu cells/ tumor

42 43 188 189

Others 808

Glucose-derived carbonaceous nanospheres

PC-3M-IE8, 4T1 cells/ 4T1 tumor

190


12

Table S4: Polymer nanostructures reported for use in PAI n.s. = not specified. DSPE-PEG = 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)], PEG = polyethylene glycol, FA = folic acid, TaOx = tantalum oxide, RGD = arginylglycylaspartic acid, DPPC = 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, MUC-1 = mucin 1, HSA = human serum albumin.

Structure of NP


Target Cell line/ tumor type Ref.

Conjugated Polymers

191

Multi- λ 706 808 680 800 700,735,820 808 750 808

DSPE-PEG, FA Linear melanin, polydopamin TaOx-NPs 64Cu2+, Fe3+, c(RGDfC), PEG DSPE-PEG DPPC, IR775S / DSPE-PEG DSPE-PEG, FA

FA receptor / / Integrin αvβ3

Vasculature ONOO-, ClO- Vasculature Passive FA receptor

MCF-7 cells/tumor L929 cells HeLa cells/U87-MG tumor NIH3T3, U87MG cells/ U87MG-tumour NIH/3T3 cells/ Sprague-Dawley rats RAW264.7/nu/nu mice (±zymostan) HUVEC/Kunming mice HeLa tumor HeLa cells/tumor

192 193 194 195 196 197 191 198 199

Porphyrin-(lipid) based NP

200

980 824 704 760 680,824 707,860 824 680-900

64Cu, PEG, core shell upconversion NP Perfluoropropane gas Perfluoropropane gas FA, PEG, cholesterol / / / Perfluorobutane

SLN Passive Passive FA receptor Temperature change SLN, LV LN /

BALB/c mice KB cells/tumor KB cells/tumor KB cells/tumor KB tumor Sprague-Dawley rats, Balb/c hairless mice VX2 tumor (rabbit) HT1080 tumor (chicken embryo)

201 202 203 200 204 205 206 207

Encapsulations

77

780 Multi- λ 790 Multi- λ Multi- λ n.s. n.s.

Dyes: DiD, DiR, SiNc Dye: DiR ICG, PEG ICG, PEG hCTM01 Ab, ICG, PEG, DOX Cy5.5, CuS Ce6, Gd3+, IR825,

/ / Cell adhesion molecules Passive MUC-1 Cell adhesion molecules Passive

BALB/c nude mice CD-1 mice Colon 26 cells/tumor HT-29 + 4T1 cells/tumor HT-29 + 4T1 cells/tumor NIH3T3, SCC7 cells/SCC7 tumor 4T1 cells/tumor

77 208 209 71 70 78 73


13

Multi- λ 680 800 700-800 750 590 800 Multi- λ 1064 808 800 680,810 760

PEG Squaraine dye Ce6, Cypate, PEG ICG, FA ICG, HSA, F3-Cys ADS-832-WS, Fumagillin Coomassie Blue, F3-Cys peptide GNR, Fe3O4-NP ICG IR5/IR26 IR820 Lipo-ICG Dye: Croc, HAS Bis-styryl BODIPY, DSPE-PEG

Passive Passive FA receptor Nucleolin SLN Nucleolin Magnetic trapping / / / / pH Lysosome

MCF-7 cells/tumor 4T1 cells/tumor MCF-7 cells/tumors 9L + MCF-7 cells Sprague-Dawley rats 9L + MCF-7 cells/9L tumor ex vivo A431 tumor / HepG2, Vero cells 4T1 cells/tumor 4T1 tumor 4T1 tumor A549 cells/tumor

69 210 76 75 72 74 211 212 80 213 214 215 216

Others

217

700 Multi- λ Multi- λ 680,825

Cellulose NPs Squaraine-Albumin aggregate Dendritic polyglycerol sulfate IR825-Benzo[a]phenoxazine-Albumin NP

/ / P- + L-selectin pH

OV2008 cells/tumor 4T1 tumor C57BL/6 mice with transmural infarct 4T1 tumor

217 218 79 219


14

References

1. Placeholder citation for complementary review. 2. Cox, B., Laufer, J. G., Arridge, S. R. & Beard, P. C. Quantitative spectroscopic

photoacoustic imaging: a review. J. Biomed. Opt. 17, 061202 (2012). 3. Beard, P. Biomedical photoacoustic imaging. Interface Focus 1, 602–631 (2011). 4. Grzelczak, M., Pérez-Juste, J., Mulvaney, P. & Liz-Marzán, L. M. Shape control in

gold nanoparticle synthesis. Chem. Soc. Rev. 37, 1783–1791 (2008). 5. Senthil Kumar, P., Pastoriza-Santos, I., Rodríguez-González, B., Javier García de

Abajo, F. & Liz-Marzán, L. M. High-yield synthesis and optical response of gold nanostars. Nanotechnology 19, 015606 (2008).

6. Sau, T. K. & Murphy, C. Room Temperature, High-Yield Synthesis of Multiple Shapes of Gold Nanoparticles in Aqueous Solution. J. Am. Chem. Soc. 126, 8648–8649 (2004).

7. Daniel, M. C. & Astruc, D. Gold Nanoparticles: Assembly, Supramolecular Chemistry, Quantum-Size-Related Properties, and Applications Toward Biology, Catalysis, and Nanotechnology. Chem. Rev. 104, 293–346 (2004).

8. Chen, Y.-S. et al. Enhanced thermal stability of silica-coated gold nanorods for photoacoustic imaging and image-guided therapy. Opt. Express 18, 8867–8878 (2010).

9. Chen, Y. S. et al. Silica-coated gold nanorods as photoacoustic signal nanoamplifiers. Nano Lett. 11, 348–354 (2011).

10. Petryayeva, E. & Krull, U. J. Localized surface plasmon resonance: Nanostructures, bioassays and biosensing-A review. Anal. Chim. Acta 706, 8–24 (2011).

11. Murphy, C. J. et al. Anisotropic metal nanoparticles: Synthesis, assembly, and optical applications. J. Phys. Chem. B 109, 13857–13870 (2005).

12. Ratto, F., Matteini, P., Rossi, F. & Pini, R. Size and shape control in the overgrowth of gold nanorods. J. Nanoparticle Res. 12, 2029–2036 (2010).

13. Leonov, A. P. et al. Detoxification of gold nanorods by treatment with polystyrenesulfonate. ACS Nano 2, 2481–2488 (2008).

14. De Paoli Lacerda, S. H. et al. Interaction of gold nanoparticles with common human blood proteins. ACS Nano 4, 365–379 (2010).

15. Owens, D. E. & Peppas, N. a. Opsonization, biodistribution, and pharmacokinetics of polymeric nanoparticles. Int. J. Pharm. 307, 93–102 (2006).

16. Khlebtsov, N. & Dykman, L. Biodistribution and toxicity of engineered gold nanoparticles: a review of in vitro and in vivo studies. Chem. Soc. Rev. 40, 1647–1671 (2011).

17. Rayavarapu, R. G. et al. In vitro toxicity studies of polymer-coated gold nanorods. Nanotechnology 21, 145101 (2010).

18. Kah, J. C. Y., Zubieta, A., Saavedra, R. a. & Hamad-Schifferli, K. Stability of gold nanorods passivated with amphiphilic ligands. Langmuir 28, 8834–8844 (2012).

19. Preston, T. C. & Signorell, R. Growth and optical properties of gold nanoshells prior to the formation of a continuous metallic layer. ACS Nano 3, 3696–3706 (2009).

20. Oldenburg, S. ., Averitt, R. ., Westcott, S. . & Halas, N. . Nanoengineering of optical resonances. Chem. Phys. Lett. 288, 243–247 (1998).

21. Jin, Y. & Gao, X. Plasmonic fluorescent quantum dots. Nat. Nanotechnol. 4, 571–576 (2009).


15

22. Jin, Y., Jia, C., Huang, S.-W., O’Donnell, M. & Gao, X. Multifunctional nanoparticles as coupled contrast agents. Nat. Commun. 1, 41 (2010).

23. Jin, Y. & Gao, X. Spectrally tunable leakage-free gold nanocontainers. J. Am. Chem. Soc. 131, 17774–17776 (2009).

24. Y. Sun, Y. X. Shape-controlled synthesis of gold and silver nanoparticles. Science (80-. ). 298, 2176–2179 (2002).

25. Skrabalak, S. E. et al. Gold Nanocages: Synthesis, Properties and Applications. Acc. Chem. Res. 41, 1587–1595 (2008).

26. Wang, F. et al. Gate-variable optical transitions in graphene. Science 320, 206–209 (2008).

27. Bonaccorso, F., Sun, Z., Hasan, T. & Ferrari, a. C. Graphene Photonics and Optoelectronics. Nat. Photonics 4, 611–622 (2010).

28. Novoselov, K. S. et al. Two-dimensional atomic crystals. Proc. Natl. Acad. Sci. U. S. A. 102, 10451–10453 (2005).

29. Hernandez, Y. et al. High-yield production of graphene by liquid-phase exfoliation of graphite. Nat. Nanotechnol. 3, 563–568 (2008).

30. Lotya, M. et al. Liquid Phase Production of Graphene by Exfoliation of Graphite in Surfactant / Water Solutions Liquid Phase Production of Graphene by Exfoliation of Graphite in Surfactant / Water Solutions. 3611–3620 (2009). doi:10.1021/ja807449u

31. Robinson, J. T. et al. Ultrasmall reduced graphene oxide with high near-infrared absorbance for photothermal therapy. J. Am. Chem. Soc. 133, 6825–6831 (2011).

32. Zhang, Y., Zhang, L. & Zhou, C. Review of chemical vapor deposition of graphene and related applications. Acc. Chem. Res. 46, 2329–2339 (2013).

33. Patel, M. a. et al. Direct production of graphene nanosheets for near infrared photoacoustic imaging. ACS Nano 7, 8147–8157 (2013).

34. Iijima, S. Helical microtubules of graphitic carbon. Nature 354, 56–58 (1991). 35. Guo, T. et al. Catalytic growth of single -walled nanotubes by laser vaporization.

Chem. Phys. Lett 243, 49–54 (1995). 36. Dai, H. Carbon Nanotubes  : Synthesis , Integration , and Properties. Acc. Chem. Res.

35, 1035–1044 (2002). 37. Hu, H., Zhao, B., Itkis, M. E. & Haddon, R. C. Nitric Acid Purification of Single-Walled

Carbon Nanotubes. J. Phys. Chem. B 107, 13838–13842 (2003). 38. Flavin, K. et al. Controlled carboxylic acid introduction: a route to highly purified

oxidised single-walled carbon nanotubes. J. Mater. Chem. 21, 17881 (2011). 39. Felton, S. et al. Electron paramagnetic resonance studies of the neutral nitrogen

vacancy in diamond. Phys. Rev. B - Condens. Matter Mater. Phys. 77, 1–4 (2008). 40. Davies, G., Lawson, S. & Collins, A. Vacancy related centers in diamond. Phys. Rev.

B 46, 157–170 (1992). 41. Kaur, R. & Badea, I. Nanodiamonds as novel nanomaterials for biomedical

applications: Drug delivery and imaging systems. Int. J. Nanomedicine 8, 203–220 (2013).

42. Zhang, T. et al. Photoacoustic contrast imaging of biological tissues with nanodiamonds fabricated for high near-infrared absorbance. J. Biomed. Opt. 18(2), 026018–1 – 026018–6 (2013).

43. Zhang, B. et al. Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles. Biomed. Opt. Express 3, 1662 (2012).


16

44. Viecelli, J. a., Bastea, S., Glosli, J. N. & Ree, F. H. Phase transformations of nanometer size carbon particles in shocked hydrocarbons and explosives. J. Chem. Phys. 115, 2730–2736 (2001).

45. Richley, J. C., Harvey, J. N. & Ashfold, M. N. R. On the role of carbon radical insertion reactions in the growth of diamond by chemical vapor deposition methods. J. Phys. Chem. A 113, 11416–11422 (2009).

46. Boudou, J.-P. et al. High yield fabrication of fluorescent nanodiamonds. Nanotechnology 20, 235602 (2009).

47. Zhang, M., Yudasaka, M., Ajima, K., Miyawaki, J. & Iijima, S. Light-assisted oxidation of single-wall carbon nanohorns for abundant creation of oxygenated groups that enable Chemical modifications with proteins to enhance biocompatibility. ACS Nano 1, 265–272 (2007).

48. Krueger, A. & Lang, D. Functionality is key: Recent progress in the surface modification of nanodiamond. Adv. Funct. Mater. 22, 890–906 (2012).

49. He, H. & Gao, C. General approach to individually dispersed, highly soluble, and conductive graphene nanosheets functionalized by nitrene chemistry. Chem. Mater. 22, 5054–5064 (2010).

50. Bahr, J. L. et al. Functionalization of carbon nanotubes by electrochemical reduction of aryl diazonium salts: A bucky paper electrode. J. Am. Chem. Soc. 123, 6536–6542 (2001).

51. Hodge, S. a., Bayazit, M. K., Coleman, K. S. & Shaffer, M. S. P. Unweaving the rainbow: a review of the relationship between single-walled carbon nanotube molecular structures and their chemical reactivity. Chem. Soc. Rev. 41, 4409 (2012).

52. Mochalin, V. N., Shenderova, O., Ho, D. & Gogotsi, Y. The properties and applications of nanodiamonds. Nat. Nanotechnol. 7, 11–23 (2011).

53. De La Zerda, A. et al. Family of enhanced photoacoustic imaging agents for high-sensitivity and multiplexing studies in living mice. ACS Nano 6, 4694–4701 (2012).

54. Liu, Z., Robinson, J. T., Sun, X. & Dai, H. PEGylated Nano-Graphene Oxide for Delivery of Water Insoluble Cancer Drugs (b). J Am Chem Soc 130, 10876–10877 (2008).

55. O’Connell, M. J. et al. Band gap fluorescence from individual single-walled carbon nanotubes. Science 297, 593–596 (2002).

56. Shao, Y. et al. Graphene based electrochemical sensors and biosensors: A review. Electroanalysis 22, 1027–1036 (2010).

57. Swierczewska, M. et al. A Facile, One-Step Nanocarbon Functionalization for Biomedical Applications. Nano Lett. 12, 3613–3620 (2012).

58. Vial, S. et al. Peptide-grafted nanodiamonds: Preparation, cytotoxicity and uptake in cells. ChemBioChem 9, 2113–2119 (2008).

59. Shi, J. et al. A tumoral acidic pH-responsive drug delivery system based on a novel photosensitizer (fullerene) for in vitro and in vivo chemo-photodynamic therapy. Acta Biomater. 10, 1280–1291 (2014).

60. Pecher, J. & Mecking, S. Nanoparticles of conjugated polymers. Chem. Rev. 110, 6260–6279 (2010).

61. Tuncel, D. & Demir, H. V. Conjugated polymer nanoparticles. Nanoscale 2, 484–494 (2010).

62. Kadish, K. M., Smith, K. M. & Guilard, R. Handbook of Porphyrin Science: With Applications to Chemistry, Physics, Materials Science, Engineering, Biology and Medicine, Volumes 16-20. (World Scientific, 2011).


17

63. Nguyen, T.-Q., Martini, I. B., Liu, J. & Schwartz, B. J. Controlling Interchain Interactions in Conjugated Polymers: The Effects of Chain Morphology on Exciton−Exciton Annihilation and Aggregation in MEH−PPV Films. J. Phys. Chem. B 104, 237–255 (2000).

64. Feng, L. et al. Conjugated polymer nanoparticles: preparation, properties, functionalization and biological applications. Chem. Soc. Rev. 42, 6620–33 (2013).

65. Wu, C. et al. Bioconjugation of ultrabright semiconducting polymer dots for specific cellular targeting. J. Am. Chem. Soc. 132, 15410–15417 (2010).

66. Senge, M. O. et al. Nonlinear Optical Properties of Porphyrins. Adv. Mater. 19, 2737–2774 (2007).

67. Zhang, X. et al. Importance of having low-density functional groups for generating high-performance semiconducting polymer dots. ACS Nano 6, 5429–5439 (2012).

68. Li, K. & Liu, B. Polymer-encapsulated organic nanoparticles for fluorescence and photoacoustic imaging. Chem. Soc. Rev. 43, 6570–97 (2014).

69. Zhang, D. et al. Nano-Confined Squaraine Dye Assemblies: New Photoacoustic and Near-Infrared Fluorescence Dual-Modular Imaging Probes in Vivo. Bioconjug. Chem. 25, 2021 – 2029 (2014).

70. Lozano, N., Al-ahmady, Z. S., Beziere, N. S., Ntziachristos, V. & Kostarelos, K. Monoclonal antibody-targeted PEGylated liposome-ICG encapsulating doxorubicin as a potential theranostic agent. Int. J. Pharm. (2014). doi:10.1016/j.ijpharm.2014.10.045

71. Beziere, N. et al. Biomaterials Dynamic imaging of PEGylated indocyanine green ( ICG ) liposomes within the tumor microenvironment using multi-spectral optoacoustic tomography ( MSOT ). Biomaterials 37, 415–424 (2015).

72. Pan, D. et al. Rapid synthesis of near infrared polymeric micelles for real-time sentinel lymph node imaging. Adv. Healthc. Mater. 1, 582–589 (2012).

73. Gong, H. et al. Engineering of multifunctional nano-micelles for combined photothermal and photodynamic therapy under the guidance of multimodal imaging. Adv. Funct. Mater. 1–11 (2014). doi:10.1002/adfm.201401451

74. Ray, A. et al. Targeted blue nanoparticles as photoacoustic contrast agent for brain tumor delineation. Nano Res. 4, 1163–1173 (2011).

75. Yoon, H. K. et al. Polymer–protein hydrogel nanomatrix for stabilization of indocyanine green towards targeted fluorescence and photoacoustic bio-imaging. J. Mater. Chem. B 1, 5611–5619 (2013).

76. Wang, H. et al. In vivo photoacoustic molecular imaging of breast carcinoma with folate receptor-targeted indocyanine green nanoprobes. Nanoscale 6, 14270–14279 (2014).

77. Aoki, H., Nojiri, M., Mukai, R. & Ito, S. Near-infrared absorbing polymer nano-particle as a sensitive contrast agent for photo-acoustic imaging. Nanoscale 7, 337–343 (2015).

78. Zhang, L. et al. Activatable Hyaluronic Acid Nanoparticle as a Theranostic Agent for Optical / Photoacoustic Imaging-Guided Photothermal Therapy. ACS Nano 8, 12250–12258 (2014).

79. Taruttis, A. et al. Multispectral optoacoustic tomography of myocardial infarction. Photoacoustics 1, 3–8 (2013).

80. Kohl, Y. et al. Preparation and biological evaluation of multifunctional PLGA-nanoparticles designed for photoacoustic imaging. Nanomedicine Nanotechnology, Biol. Med. 7, 228–237 (2011).

81. Tyrrell, Z. L., Shen, Y. & Radosz, M. Fabrication of micellar nanoparticles for drug


18

delivery through the self-assembly of block copolymers. Prog. Polym. Sci. 35, 1128–1143 (2010).

82. Jian, J. et al. India Ink Incorporated Multifunctional Phase-transition Nanodroplets for Photoacoustic/Ultrasound Dual-modality Imaging and Photoacoustic Effect Based Tumor Therapy. Theranostics 4, 1026–1038 (2014).

83. Hannah, A., Luke, G., Wilson, K., Homan, K. & Emelianov, S. Indocyanine green-loaded photoacoustic nanodroplets: Dual contrast nanoconstructs for enhanced photoacoustic and ultrasound imaging. ACS Nano 8, 250–259 (2014).

84. Akers, W. J. et al. Noninvasive photoacoustic and fluorescence sentinel lymph node identification using dye-loaded perfluorocarbon nanoparticles. ACS Nano 5, 173–182 (2011).

85. Hannah, A. S., VanderLaan, D., Chen, Y.-S. & Emelianov, S. Y. Photoacoustic and ultrasound imaging using dual contrast perfluorocarbon nanodroplets triggered by laser pulses at 1064 nm. Biomed. Opt. Express 5, 3042 – 3052 (2014).

86. Strohm, E. M. Acoustic and photoacoustic characterization of micron-sized perfluorocarbon emulsions. J. Biomed. Opt. 17, 096016 (2012).

87. Wilson, K., Homan, K. & Emelianov, S. Biomedical photoacoustics beyond thermal expansion using triggered nanodroplet vaporization for contrast-enhanced imaging. Nat. Commun. 3, 618 (2012).

88. Jeon, M. et al. Methylene blue microbubbles as a model dual-modality contrast agent for ultrasound and activatable photoacoustic imaging. J. Biomed. Opt. 19, 16005–8 (2014).

89. Motomura, K. et al. SPIO-Enhanced Magnetic Resonance Imaging for the Detection of Metastases in Sentinel Nodes Localized by Computed Tomography Lymphography in Patients with Breast Cancer. Ann. Surg. Oncol. 18, 3422–3429 (2011).

90. Grootendorst, D. et al. Evaluation of a super paragmagnetic iron oxide nanoparticle ( Endorem R ) as a photoacoustic contrast agent for nodal enhancement. Contrast Media Mol. Imaging 8, 83–99 (2013).

91. Galanzha, E. I. et al. In vivo magnetic enrichment and multiplex photoacoustic detection of circulating tumour cells. Nat. Nanotechnol. 4, 855–860 (2009).

92. Tang, J., Myers, M., Bosnick, K. a & Brus, L. E. Magnetite Fe3O4 Nanocrystals: Spectroscopic Observation of Aqueous Oxidation Kinetics. J. Phys. Chem. B 107, 7501–7506 (2003).

93. Grootendorst, D. J. et al. Intra-operative ex vivo photoacoustic nodal staging in a rat model using a clinical superparamagnetic iron oxide nanoparticle dispersion. J. Biophotonics 6, 493–504 (2013).

94. Alwi, R. et al. Silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biocompatible contrast agent in biomedical photoacoustics. Biomed. Opt. Express 3, 2500 (2012).

95. Xi, L. et al. HER-2/neu targeted delivery of a nanoprobe enables dual photoacoustic and fluorescence tomography of ovarian cancer. Nanomedicine Nanotechnology, Biol. Med. 10, 669–677 (2014).

96. Xi, L. et al. Molecular photoacoustic tomography of breast cancer using receptor targeted magnetic iron oxide nanoparticles as contrast agents. J. Biophotonics 7, 401–409 (2014).

97. Photoacoustic, C. M. Magneto-Optical Nanoparticles for Imaging. (2015). 98. Li, X.-D. et al. Imaging guided photothermal therapy using iron oxide loaded

poly(lactic acid) microcapsules coated with graphene oxide. J. Mater. Chem. B 2,


19

217–223 (2014). 99. Wang, C., Chen, J., Talavage, T. & Irudayaraj, J. Gold Nanorod/Fe3O4 nanoparticle

‘nano-pearl- necklaces’ for simultaneous targeting, dual-mode imaging, and photothermal ablation of cancer cells. Angew. Chemie - Int. Ed. 48, 2759–2763 (2009).

100. Ku, G. et al. Copper sulfide nanoparticles as a new class of photoacoustic contrast agent for deep tissue imaging at 1064 nm. ACS Nano 6, 7489–7496 (2012).

101. Yang, K. et al. Visualization of protease activity in vivo using an activatable photo-acoustic imaging probe based on CuS nanoparticles. Theranostics 4, 134–141 (2014).

102. Gao, D. et al. Compact chelator-free Ni-integrated CuS nanoparticles with tunable near-infrared absorption and enhanced relaxivity for in vivo dual-modal photoacoustic/MR imaging. Nanoscale (2015). doi:10.1039/C5NR05237H

103. Zhou, M. et al. A chelator-free multifunctional [64Cu]CuS nanoparticle platform for simultaneous micro-PET/CT imaging and photothermal ablation therapy. J. Am. Chem. Soc. 132, 15351–15358 (2010).

104. Kim, C., Song, K. H., Gao, F. & Wang, L. V. Sentinel Lymph Nodes and Lymphatic Vessels  : Noninvasive Dual-Modality in Vivo Mapping by Using Indocyanine Green in Rats — Volumetric Spectroscopic Photoacoustic Imaging and Planar Fluorescence Imaging. Radiology 255, 442–450 (2010).

105. Kang, N.-Y. et al. A macrophage uptaking near-infrared chemical probe for in vivo imaging of inflammation. Chem. Commun. (Camb). 50, 6589–91 (2014).

106. Kovar, J. L., Volcheck, W., Sevick-Muraca, E., Simpson, M. a. & Olive, D. M. Characterization and performance of a near-infrared 2-deoxyglucose optical imaging agent for mouse cancer models. Anal. Biochem. 384, 254–262 (2009).

107. Chatni, M. R. et al. Tumor glucose metabolism imaged in vivo in small animals with whole-body photoacoustic computed tomography. J. Biomed. Opt. 17, 076012 (2012).

108. Li, M. L. et al. Simultaneous molecular and hypoxia imaging of brain tumors in vivo using spectroscopic photoacoustic tomography. Proc. Ieee 96, 481–489 (2008).

109. Onoe, S., Temma, T., Kanazaki, K., Ono, M. & Saji, H. Development of photostabilized asymmetrical cyanine dyes for in vivo photoacoustic imaging of tumors Development of photostabilized asymmetrical cyanine dyes for in vivo photoacoustic imaging of tumors. J. Biomed. Opt. 20, 096006 (2015).

110. Temma, T., Onoes, S., Kanazaki, K., Ono, M. & Saji, H. Preclinical evaluation of a novel cyanine dye for tumor imaging with in vivo photoacoustic imaging a novel cyanine dye for. J. Biomed. Opt. 19, 090501 (2014).

111. Yang, Q., Cui, H., Cai, S., Yang, X. & Forrest, M. L. In vivo photoacoustic imaging of chemotherapy-induced apoptosis in squamous cell carcinoma using a near-infrared caspase-9 probe. J. Biomed. Opt. 16, 116026 (2011).

112. Sim, N. et al. Wavelength-dependent optoacoustci imaging probes for NMDA receptor visualisation. Chem. Commun. 51, 15149–15152 (2015).

113. Song, K. H., Stein, E. W., Margenthaler, J. a & Wang, L. V. Noninvasive photoacoustic identification of sentinel lymph nodes containing methylene blue in vivo in a rat model. J. Biomed. Opt. 13, 054033 (2008).

114. Kim, C., Erpelding, T. N., Jankovic, L. & Wang, L. V. Performance benchmarks of an array-based hand-held photoacoustic probe adapted from a clinical ultrasound system for non-invasive sentinel lymph node imaging. Philos. Trans. R. Soc. A Math. Phys. Eng. Sci. 369, 4644–4650 (2011).


20

115. Shao, Q. et al. In vivo photoacoustic lifetime imaging of tumor hypoxia in small animals. Biomed. Opt. 18, 076019 (2013).

116. Ashkenazi, S. Photoacoustic lifetime imaging of dissolved oxygen using methylene blue. J. Biomed. Opt. 15, 040501 (2010).

117. Song, L., Kim, C., Maslov, K., Shung, K. K. & Wang, L. V. High-speed dynamic 3D photoacoustic imaging of sentinel lymph node in a murine model using an ultrasound array. Med. Phys. 36, 3724–3729 (2009).

118. Beziere, N. & Ntziachristos, V. Optoacoustic Imaging of Naphthalocyanine: Potential for Contrast Enhancement and Therapy Monitoring. J. Nucl. Med. 56, 323–328 (2014).

119. Razansky, D., Vinegoni, C. & Ntziachristos, V. Multispectral photoacoustic imaging of fluorochromes in small animals. Opt. Lett. 32, 2891–2893 (2007).

120. Stantz, K. M., Cao, M., Liu, B., Miller, K. D. & Guo, L. Molecular Imaging of Neutropilin-1 Receptor Using Photoacoustic Spectroscopy in Breast Tumors. Spie 7564, 75641O–75641O–7 (2010).

121. Levi, J. et al. Molecular Photoacoustic Imaging of Follicular Thyroid Carcinoma. Clin. Cancer Res. 19, 1494–1502 (2013).

122. Bhattacharyya, S. et al. Synthesis and evaluation of near-infrared (NIR) dye-herceptin conjugates as photoacoustic computed tomography (PCT) probes for HER2 expression in breast cancer. Bioconjug. Chem. 19, 1186–1193 (2008).

123. Kimbrough, C. W. et al. Targeting Acidity in Pancreatic Adenocarcinoma  : Multispectral Optoacoustic Tomography Detects pH-Low Insertion Peptide Probes In Vivo. 21, 4576–4586 (2015).

124. Chatni, M. R. et al. Functional photoacoustic microscopy of pH. J. Biomed. Opt. 16, 100503 (2011).

125. Horvath, T. D., Kim, G., Kopelman, R. & Ashkenazi, S. Ratiometric photoacoustic sensing of pH using a ‘sonophore’. Analyst 133, 747–749 (2008).

126. Hudson, S. V. et al. Targeted Noninvasive Imaging of EGFR-Expressing Orthotopic Pancreatic Cancer Using Multispectral Optoacoustic Tomography. Cancer Res. 74, 6271–6279 (2014).

127. Levi, J., Sathirachinda, A. & Gambhir, S. S. A high-affinity, high-stability photoacoustic agent for imaging gastrin-releasing peptide receptor in prostate cancer. Clin. Cancer Res. 20, 3721–3729 (2014).

128. Dragulescu-Andrasi, A., Kothapalli, S. R., Tikhomirov, G. a., Rao, J. & Gambhir, S. S. Activatable oligomerizable imaging agents for photoacoustic imaging of furin-like activity in living subjects. J. Am. Chem. Soc. 135, 11015–11022 (2013).

129. C, Z. et al. A Cystine Knot Peptide Targeting Integrin αvβ6 for Photoacoustic and Fluorescence Imaging of Tumors in Living Subjects. J Nucl Med. jnumed.115, (2016).

130. Huang, H. et al. Axial PEGylation of Tin Octabutoxy Naphthalocyanine Extends Blood Circulation for Photoacoustic Vascular Imaging. Bioconjug. Chem. acs.bioconjchem.6b00280 (2016). doi:10.1021/acs.bioconjchem.6b00280

131. Cho, E. C., Liu, Y. & Xia, Y. A simple spectroscopic method for differentiating cellular uptakes of gold nanospheres and nanorods from their mixtures. Angew. Chemie - Int. Ed. 49, 1976–1980 (2010).

132. Mallidi, S., Joshi, P. P., Sokolov, K. & Emelianov, S. On sensitivity of molecular specific photoacoustic imaging using plasmonic gold nanoparticles. Conf Proc IEEE Eng Med Biol Soc 2009 6338–6340 (2009). doi:10.1109/IEMBS.2009.5333161

133. Mallidi, S., Larson, T., Aaron, J., Sokolov, K. & Emelianov, S. Molecular specific


21

optoacoustic imaging with plasmonic nanoparticles. Opt. Express 15, 6583–6588 (2007).

134. Mallidi, S. et al. Multiwavelength photoacoustic imaging and plasmon resonance coupling of gold nanoparticles for selective detection of cancer. Nano Lett. 9, 2825–2831 (2009).

135. Yasmin, Z. et al. In vitro monitoring of oxidative processes with self-aggregating gold nanoparticles using all-optical photoacoustic spectroscopy. Biosens. Bioelectron. 64, 676–682 (2015).

136. Jing, L. et al. Prussian blue coated gold nanoparticles for simultaneous photoacoustic/CT bimodal imaging and photothermal ablation of cancer. Biomaterials 35, 5814–5821 (2014).

137. Zhang, Q. et al. Gold nanoparticles as a contrast agent for in vivo tumor imaging with photoacoustic tomography. Nanotechnology 20, 395102 (2009).

138. Luke, G. P., Myers, J. N., Emelianov, S. Y. & Sokolov, K. V. Sentinel lymph node biopsy revisited: Ultrasound-guided photoacoustic detection of micrometastases using molecularly targeted plasmonic nanosensors. Cancer Res. 74, 5397–5408 (2014).

139. Cheheltani, R. et al. Tunable, biodegradable gold nanoparticles as contrast agents for computed tomography and photoacoustic imaging. Biomaterials 102, 87–97 (2016).

140. Song, J. et al. ‘Smart’ gold nanoparticles for photoacoustic imaging: an imaging contrast agent responsive to the cancer microenvironment and signal amplification via pH-induced aggregation. Chem. Commun. (2016). doi:10.1039/C6CC03100E

141. Vonnemann, J. et al. Polyglycerolsulfate functionalized gold nanorods as optoacoustic signal nanoamplifiers for in vivo bioimaging of rheumatoid arthritis. Theranostics 4, 629–641 (2014).

142. Locatelli, E. et al. Targeted polymeric nanoparticles containing gold nanorods: A therapeutic approach against glioblastoma. J. Nanoparticle Res. 16, (2014).

143. Heidari, Z., Sariri, R. & Salouti, M. Gold nanorods-bombesin conjugate as a potential targeted imaging agent for detection of breast cancer. J. Photochem. Photobiol. B Biol. 130, 40–46 (2014).

144. Kim, S., Chen, Y.-S., Luke, G. P. & Emelianov, S. Y. In-vivo ultrasound and photoacoustic image- guided photothermal cancer therapy using silica-coated gold nanorods. IEEE Trans. Ultrason. Ferroelectr. Freq. Control 61, 891–7 (2014).

145. Yang, H. W. et al. Magnetic gold-nanorod/ PNIPAAmMA nanoparticles for dual magnetic resonance and photoacoustic imaging and targeted photothermal therapy. Biomaterials 34, 5651–5660 (2013).

146. Joshi, P. P., Yoon, S. J., Hardin, W. G., Emelianov, S. & Sokolov, K. V. Conjugation of antibodies to gold nanorods through fc portion: Synthesis and molecular specific imaging. Bioconjug. Chem. 24, 878–888 (2013).

147. Jokerst, J. V, Thangaraj, M., Kempen, P. J., Sinclair, R. & Gambhir, S. S. Photoacoustic Imaging of Mesenchymal Stem Cells in Living Mice via Silica-Coated Gold Nanorods. ACS Nano 6, 5920–5930 (2012).

148. Jokerst, J. V., Cole, A. J., Van De Sompel, D. & Gambhir, S. S. Gold nanorods for ovarian cancer detection with photoacoustic imaging and resection guidance via Raman imaging in living mice. ACS Nano 6, 10366–10377 (2012).

149. Ha, S., Carson, A., Agarwal, A., Kotov, N. a & Kim, K. Detection and monitoring of the multiple inflammatory responses by photoacoustic molecular imaging using selectively targeted gold nanorods. Biomed. Opt. Express 2, 645–657 (2011).

150. Bayer, C. L. et al. Multiplex photoacoustic molecular imaging using targeted silica-


22

coated gold nanorods. Biomed. Opt. Express 2, 1828–1835 (2011). 151. Agarwal, A. et al. Dual-mode imaging with radiolabeled gold nanorods. J. Biomed.

Opt. 16, 051307 (2011). 152. Li, P.-C. et al. In vivo photoacoustic molecular imaging with simultaneous multiple

selective targeting using antibody-conjugated gold nanorods. Opt. Express 16, 18605–18615 (2008).

153. Moon, H. et al. Amplified photoacoustic performance and enhanced photothermal stability of reduced graphene oxide coated gold nanorods for sensitive photoacoustic imaging. ACS Nano 9, 2711–2719 (2015).

154. Zhang, M., Kim, H. S., Jin, T., Yi, A. & Moon, W. K. Ultrasound-guided photoacoustic imaging for the selective detection of EGFR-expressing breast cancer and lymph node metastases. Biomed. Opt. Express 7, 1920 (2016).

155. Qin, H. et al. Inflammation-targeted gold nanorods for intravascular photoacoustic imaging detection of matrix metalloproteinase-2 (MMP2) in atherosclerotic plaques. Nanomedicine Nanotechnology, Biol. Med. 2, 1765–1774 (2016).

156. Chen, H. et al. Synthesis and characterization of an HSP27-targeted nanoprobe for in vivo photoacoustic imaging of early nerve injury. Nanomedicine Nanotechnology, Biol. Med. 12, 1453–1462 (2016).

157. Nie, L. et al. In vivo volumetric photoacoustic molecular angiography and therapeutic monitoring with targeted plasmonic nanostars. Small 10, 1585–1593 (2014).

158. Kim, C. et al. In vivo photoacoustic mapping of lymphatic systems with plasmon-resonant nanostars. J. Mater. Chem. 21, 2841 (2011).

159. Liang, S. et al. CD44v6 Monoclonal Antibody-Conjugated Gold Nanostars for Targeted Photoacoustic Imaging and Plasmonic Photothermal Therapy of Gastric Cancer. Theranostics 5, 970–984 (2015).

160. Cheng, K. et al. Construction and validation of nano gold tripods for molecular imaging of living subjects. J. Am. Chem. Soc. 136, 3560–3571 (2014).

161. Bao, C. et al. Gold nanoprisms as optoacoustic signal nanoamplifiers for in vivo bioimaging of gastrointestinal cancers. Small 9, 68–74 (2013).

162. Hu, J. et al. Theranostic Au cubic nano-aggregates as potential photoacoustic contrast and photothermal therapeutic agents. Theranostics 4, 534–545 (2014).

163. Luke, G. P. et al. Silica-coated gold nanoplates as stable photoacoustic contrast agents for sentinel lymph node imaging. Nanotechnology 24, 455101 (2013).

164. Cai, X. et al. In vivo quantitative evaluation of the transport kinetics of gold nanocages in a lymphatic system by noninvasive photoacoustic tomography. ACS Nano 5, 9658–9667 (2011).

165. Srivatsan, A. et al. Gold nanocage-photosensitizer conjugates for dual-modal image-guided enhanced photodynamic therapy. Theranostics 4, 163–174 (2014).

166. Cho, E. C. et al. Quantitative analysis of the fate of gold nanocages in vitro and in vivo after uptake by U87-MG tumor cells. Angew. Chemie - Int. Ed. 52, 1152–1155 (2013).

167. Zhang, Y. S. et al. Labeling human mesenchymal stem cells with gold nanocages for in vitro and in vivo tracking by two-photon microscopy and photoacoustic microscopy. Theranostics 3, 532–543 (2013).

168. Xia, X. et al. An enzyme-sensitive probe for photoacoustic imaging and fluorescence detection of protease activity. Nanoscale 3, 950–953 (2011).

169. Kim, C. et al. In vivo molecular photoacoustic tomography of melanomas targeted by bio-conjugated gold nanocages. ACS Nano 4, 4559–4564 (2010).


23

170. Song, K. H., Kim, C., Cobley, C. M., Xia, Y. & Wang, L. V. Near-Infrared Gold Nanocages as a New Class of Tracers for Photoacoustic Sentinel Lymph Node Mapping on a Rat Model. Nano Lett. 9, 183–188 (2009).

171. Lin, J. et al. Photosensitizer-loaded gold vesicles with strong plasmonic coupling effect for imaging-guided photothermal/photodynamic therapy. ACS Nano 7, 5320–5329 (2013).

172. Lu, W. et al. Effects of photoacoustic imaging and photothermal ablation therapy mediated by targeted hollow gold nanospheres in an orthotopic mouse xenograft model of glioma. Cancer Res. 71, 6116–6121 (2011).

173. Ye, S. et al. Engineering Gold Nanotubes with Controlled Length and Near-Infrared Absorption for Theranostic Applications. Adv. Funct. Mater. n/a–n/a (2015). doi:10.1002/adfm.201404358

174. Lu, X., Yu, M., Huang, H. & Ruoff, R. S. Tailoring graphite with the goal of achieving single sheets. Nanotechnology 10, 269 (1999).

175. Wu, L. et al. A Green Synthesis of Carbon Nanoparticle from Honey for Real-Time Photoacoustic Imaging. Nano Res. 6, 312–325 (2013).

176. Qin, H., Zhou, T., Yang, S. & Xing, D. Fluorescence Quenching Nanoprobes Dedicated to In Vivo Photoacoustic Imaging and High-Efficient Tumor Therapy in Deep-Seated Tissue. Small n/a–n/a (2015). doi:10.1002/smll.201403395

177. Wang, Y.-W. et al. Dye-enhanced graphene oxide for photothermal therapy and photoacoustic imaging. J. Mater. Chem. B 1, 5762 (2013).

178. Romero-Aburto, R. et al. Fluorinated graphene oxide; A new multimodal material for biological applications. Adv. Mater. 25, 5632–5637 (2013).

179. Hu, D. et al. Indocyanine Green-Loaded Polydopamine-Reduced Graphene Oxide Nanocomposites with Amplifying Photoacoustic and Photothermal Effects for Cancer Theranostics. Theranostics 6, 1043–1052 (2016).

180. Wang, C. et al. Protamine functionalized single-walled carbon nanotubes for stem cell labeling and in vivo Raman/magnetic resonance/photoacoustic triple-modal imaging. Adv. Funct. Mater. 22, 2363–2375 (2012).

181. Tsyboulski, D. a. et al. Enabling in vivo measurements of nanoparticle concentrations with three-dimensional optoacoustic tomography. J. Biophotonics 7, 581–588 (2014).

182. Koo, J. et al. In vivo non-ionizing photoacoustic mapping of sentinel lymph nodes and bladders with ICG-enhanced carbon nanotubes. Phys. Med. Biol. 57, 7853–62 (2012).

183. Zerda, A. D. La et al. Ultrahigh sensitivity carbon nanotube agents for photoacoustic molecular imaging in living mice. Nano Lett. 10, 2168–2172 (2010).

184. Kim, J., Galanzha, E. I., Shashkov, E. V, Moon, H. & Zharov, V. P. Golden carbon nanotubes as multimodal photoacoustic and photothermal high-contrast molecular agents. Nat. Nanotechnol. 4, 688–694 (2009).

185. De la Zerda, A. et al. Carbon nanotubes as photoacoustic molecular imaging agents in living mice. Nat. Nanotechnol. 3, 557–562 (2008).

186. Song, J. et al. Gold Nanoparticle Coated Carbon Nanotube Ring with Enhanced Raman Scattering and Photothermal Conversion Property for Theranostic Applications. J. Am. Chem. Soc. jacs.5b13475 (2016). doi:10.1021/jacs.5b13475

187. Wang, C. et al. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer. Nanoscale Reserach Lett. 9, 1–10 (2014).

188. Zhang, T. et al. Targeted nanodiamonds as phenotype-specific photoacoustic contrast agents for breast cancer. Nanomedicine 10, 573–587 (2015).


24

189. Zhang, T. et al. In vivo photoacoustic imaging of breast cancer tumor with HER2-targeted nanodiamonds. Proc. SPIE 8815, (2013).

190. Miao, Z.-H. et al. Glucose-Derived Carbonaceous Nanospheres for Photoacoustic Imaging and Photothermal Therapy. ACS Appl. Mater. Interfaces acsami.6b03652 (2016). doi:10.1021/acsami.6b03652

191. Zha, Z. et al. Biocompatible polypyrrole nanoparticles as a novel organic photoacoustic contrast agent for deep tissue imaging. Nanoscale 5, 4462–7 (2013).

192. Balasundaram, G. et al. Molecular photoacoustic imaging of breast cancer using an actively targeted conjugated polymer. Int. J. Nanomedicine 10, 387–397 (2015).

193. Repenko, T. et al. Water-soluble dopamine-based polymers for photoacoustic imaging. Chem. Commun. (2015). doi:10.1039/C5CC00039D

194. Jin, Y. et al. Encapsulating tantalum oxide into polypyrrole nanoparticles for X-ray CT/photoacoustic bimodal imaging-guided photothermal ablation of cancer. Biomaterials 35, 5795–5804 (2014).

195. Fan, Q. et al. Transferring Biomarker into Molecular Probe: Melanin Nanoparticle as a Naturally Active Platform for Multimodality Imaging. J. Am. Chem. Soc. 15185–15194 (2014).

196. Liu, J. et al. Conjugated polymer nanoparticles for photoacoustic vascular imaging. Polym. Chem. 5, 2854 (2014).

197. Pu, K. et al. Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes in living mice. Nat. Nanotechnol. 9, 233–9 (2014).

198. Pu, K. et al. Diketopyrrolopyrrole-Based Semiconducting Polymer Nanoparticles for In Vivo Photoacoustic Imaging. Adv. Mater. n/a–n/a (2015). doi:10.1002/adma.201502285

199. Wang, J. et al. Targeted lipid–polyaniline hybrid nanoparticles for photoacoustic imaging guided photothermal therapy of cancer. Nanotechnology 27, 285102 (2016).

200. Lovell, J. F. et al. Porphysome nanovesicles generated by porphyrin bilayers for use as multimodal biophotonic contrast agents. Nat. Mater. 10, 324–332 (2011).

201. Rieffel, J. et al. Hexamodal Imaging with Porphyrin-Phospholipid-Coated Upconversion Nanoparticles. Adv. Mater. (2015). doi:10.1002/adma.201404739

202. Huynh, E. et al. In situ conversion of porphyrin microbubbles to nanoparticles for multimodality imaging. Nat. Nanotechnol. 10, 325–332 (2015).

203. Huynh, E., Jin, C. S., Wilson, B. C. & Zheng, G. Aggregate enhanced trimodal porphyrin shell microbubbles for ultrasound, photoacoustic, and fluorescence imaging. Bioconjug. Chem. 25, 796–801 (2014).

204. Ng, K. K. et al. Stimuli-Responsive Photoacoustic Nanoswitch for In Vivo Sensing Applications. ACS Nano 8, 8363–8373 (2014).

205. Lee, C. et al. Biomaterials Dual-color photoacoustic lymph node imaging using nanoformulated naphthalocyanines. Biomaterials 73, 142–148 (2015).

206. Shakiba, M. et al. Stable J-aggregation enabled dual photoacoustic and fluorescence nanoparticles for intraoperative cancer imaging. Nanoscale (2015). doi:10.1039/C5NR08165C

207. Paproski, R. J. et al. Porphyrin Nanodroplets: Sub-micrometer Ultrasound and Photoacoustic Contrast Imaging Agents. Small 12, 371–380 (2016).

208. Egusquiaguirre, S. P. et al. Optoacoustic imaging enabled biodistribution study of cationic polymeric biodegradable nanoparticles. Contrast Media Mol. Imaging n/a–n/a (2015). doi:10.1002/cmmi.1644


25

209. Miki, K. et al. Near-Infrared Dye-Conjugated Amphiphilic Hyaluronic Acid Derivatives as a Dual Contrast Agent for In Vivo Optical and Photoacoustic Tumor Imaging. Biomacromolecules 16, 219–227 (2015).

210. Guo, M. et al. Dual imaging-guided photothermal/photodynamic therapy using micelles. Biomaterials 35, 4656–4666 (2014).

211. Qu, M. et al. Contrast-enhanced magneto-photo-acoustic imaging in vivo using dual-contrast nanoparticles. Photoacoustics 2, 55–62 (2014).

212. Gupta, S. et al. Virus-mimicking nano-constructs as a contrast agent for near infrared photoacoustic imaging. Nanoscale 5, 1772–6 (2013).

213. Huang, P. et al. Dye-loaded ferritin nanocages for multimodal imaging and photothermal therapy. Adv. Mater. 26, 6401–6408 (2014).

214. Ermolayev, V., Dean-ben, X. L., Mandal, S., Ntziachristos, V. & Razansky, D. Simultaneous visualization of tumour oxygenation , neovascularization and contrast agent perfusion by real-time three-dimensional optoacoustic tomography. (2015). doi:10.1007/s00330-015-3980-0

215. Chen, Q., Liu, X., Zeng, J., Cheng, Z. & Liu, Z. Albumin-NIR dye self-assembled nanoparticles for photoacoustic pH imaging and pH-responsive photothermal therapy effective for large tumors. Biomaterials 98, 23–30 (2016).

216. Hu, W. et al. Engineering Lysosome-Targeting BODIPY Nanoparticles for Photoacoustic Imaging and Photodynamic Therapy under Near-Infrared Light. ACS Appl. Mater. Interfaces 8, 12039–12047 (2016).

217. Jokerst, J. V., Van de Sompel, D., Bohndiek, S. E. & Gambhir, S. S. Cellulose nanoparticles are a biodegradable photoacoustic contrast agent for use in living mice. Photoacoustics 2, 119–127 (2014).

218. An, F. et al. Aggregation-Induced Near-Infrared Absorption of Squaraine Dye in an Albumin Nanocomplex for Photoacoustic Tomography in Vivo. Appl. Mater. Interfaces (2014).

219. Chen, Q., Liu, X., Chen, J., Zeng, J. & Cheng, Z. A Self-Assembled Albumin-Based Nanoprobe for In Vivo Ratiometric Photoacoustic pH Imaging. 1–8 (2015). doi:10.1002/adma.201503194


Documents

a) 2D or 3D imaging using a linear or planar array ...proximity they undergo (partial) intramolecular charge transfer upon excitation).1,3 The integration of a metal center to the