Antithrombogenicinterfaces based on the phospholipid

Biomaterials Laboratory, The University of Tokyo

Antithrombogenic interfaces based on the phospholipid polymers

Kazuhiko ISHIHARA

Department of Materials EngineeringThe University of Tokyo


Bioinspired concept

Homogeneous polymer systemHydrophobic polymer(PTFE, PDMS)

Hydrophilic polymer(PVA, PHEMA, cellulose)

Water-soluble polymergrafted substrate

Hybridization of biomolecules with polymers

Heparinized polymer substrateUrokinase immobilized substrateThrombomodulin immobilized substrate

Segmented polyurethane

Hydrophilic-hydrophobic block-type polymerPolyion complex

Crystalline/amorphous block-type polymer

MPC polymers

Synthetic polymer system

Biomimetic approach

Multi-phase polymer system

Zwitterionic polymersMixed charge polymers

Design of (Bio)blood compatible polymers

K. Ishihara, J. Biomed. Mater. Res. (2019)

1970s

1980s

1970s-1990s

1990s

2000s


2-Methacryloyloxyethyl phosphorylcholine (MPC) polymer - PC surface technology

2-Methacryloyloxyethyl phosphorylcholine (MPC)

CH2 C

CH3

C O

OCH2CH2OPOCH2CH2N(CH3)3O

O

Phosphorylcholine group

Bioinspired design

Ishihara K. et al. Polym.J., 22, 355, 1990

MPC is designed by inspiration from cell membrane surface. It is highly hydrophilic monomer and can polymerize with other vinyl monomers.MPC polymers provide the biocompatible surface.(PC surface technology:PCST)

Cell membrane structure

Highly organized phospholipidassembly


Molecular design of bioinspired MPC polymers

CH2 CCH3

OCH2CH2OPOCH2CH2N(CH3)3

C O

O

O+

-

( CH2 C )b

CH3

OCH2CH2CH2CH3

C O( CH2 C )a

CH3


C O

O

O+

-

( CH2 C )n

CH3


C O

O

O+

-

MPC Poly(MPC)

Poly(MPC-random-BMA) (PMB)

BMA

K. Ishihara et al., Polym J 1990T. Ueda, K. Ishihara et al., Polym J 1992

Water-soluble polymer

Water-solubility depends on the composition, chemical structure, and molecular weight.


Characteristics of bioinspired MPC polymers1. Super-hydrophilic character

2. Electrically neutral

3. Easily applicable for surface modification on any substrateDip coating(Solution casting), reacting, blending, grafting etc.

4. Stable in biological conditions (pH 7.4, 37°C, and high ionic strength)

5. No degradation occurs both by hydrolysis and enzymatic reaction

6. Stable even under sterilization conditions (-ray, EOG, thermally)

7. Excellent lubrication at the water-contact interface

Contact angle by water in air is below 10°Oil detachment occurs easily by immersion in water

Hexadecane/water

Water/air Air/water

K. Ishihara and K. Fukazawa 2014

-potential(mV): Glass = -60, Plastics = -40, Metal = -40, MPC polymer ≈ 0


Ti alloy

Polyurethane

Silicone

SUS

Hard contact lenses

A. Lewis, Colloid Surf B: Biointerface 2000

Surface treatment with MPC polymer

MPC polymer can cover on every materials by easy process, such as solution casting, grafting, reaction.Original surface Original surfaceAfter modification After modification

Fluorescence-image of the MPC polymer layer after staining.


Biological response on the biomedical devices

Protein Adsorption Layer

Substrate (Metal, Ceramics, Polymers, Composites)

Blood Coagulation(Thrombus formation)

Cellular reactionImmunological reaction

Inflammatory reactionPhagocytosis

Complement system activation



Biological response on the biomedical devices

Substrate (Metal, Ceramics, Polymers, Composites)

Blood Coagulation(Thrombus formation)

Cellular reactionImmunological reaction

Inflammatory reactionPhagocytosis

Complement system activation

MPC polymer



Protein adsorption to the surfaces should be completely understoodand regulated for developing safer medical devices.

Cell adhesion Undesirable reactionProtein adsorption

Initial event

Multilayer adsorption

ApproachDetachment

Conformation change

Protein-proteininteraction

× Clot formation× Inflammation

Protein adsorption mechanism on the surface

Biomaterials Laboratory, The University of Tokyo K. Ishihara et al., J Biomed Mater Res 1998

0.00 0.40 0.60 0.80 1.000.00

1.00

2.00

3.00

4.00

1.7 g/cm2

0.9 g/cm2

Protein adsorption depends on water structure

Free water fraction in hydrated polymerAm

ount

of p

rote

in a

dsor

bed (g/cm

2 )

Conventional hydrophilic polymers

MPC polymers

Fibrinogen adsorption

Albumin adsorption

Amount ofadsorbed proteins with monolayer


Free water fraction in hydrated polymerAm

ount

of p

rote

in a

dsor

bed (g/cm

2 )

Amount of protein adsorbed on hydrophilic polymer surface depends on the free water fraction in the hydrated polymer.

0.00 0.40 0.60 0.80 1.000.00

1.00

2.00

3.00

4.00Conventional hydrophilic polymers

MPC polymers

Fibrinogen adsorption

Albumin adsorption


1.7 g/cm2

0.9 g/cm2

K. Ishihara et al., J Biomed Mater Res 1998

Amount ofadsorbed proteins with monolayer


Hydrophobic hydration

Weak interaction between water molecules and polymer

Promotion of clustering of water molecules

Detachment of protein

Free water structure as bulk water

Entropy driven

MPC polymer

Free water (bulk water like water state) content is large compared to conventional hydrophilic polymers.

For prone to exchange reaction of water molecules, elimination of contact with protein is facilitated.


K. Ishihara, et al., J Biomater Sci Polym Ed (2018)


Whitesides Hypothesis

He says that surfaces that resist the adsorption of proteins, in the set incorporate groups, exhibit four molecular level characteristics: (i) They are hydrophilic. (ii) They include hydrogen-bond acceptors.

-O-, -N=(iii) They do not include hydrogen-bond donors.

-OH, -NH2, -COOH, -CONH-, (iv) Their overall electrical charge is neutral.

K. Ishihara, Langmuir 2019

Whitesides, G. M. et al. J. Am. Chem. Soc. 2000, 122, 8303−8304.Whitesides, G. M. et al. Langmuir 2001, 17, 2841−2850.

Prof. George M Whiteside

The hypothesis for protein adsorption resistance at an interface has been proposed by Prof. Whitesides.



















poly(MPC)


Protein adsorption form human plasmaAlbFibIgGXIIVIII

HMWK C5 FN Alpha fetoprotein PBS (control)

GlassPoly(MPC-co-BMA) Composition of MPC unit (%)

0 (poly(BMA)) 20 30

20

10

0

MPC units provide excellent protein adsorption resistance property.

Am

ount

of a

dsor

bed

prot

eins

CPM

x 1

0-3

per 2

cm

2

K. Ishihara, et al., J Biomed Mater Res (1991) 25, 1397


Glass Poly(BMA)

Poly(MPC-co-BMA) : MPC unit: 0.20 Poly(MPC-co-BMA) : MPC unit: 0.30

Y YYY YY

The gold colloid was enhanced to100-200 nm with silver and the surface was observed by SEM.

K. Ishihara, et al., J Biomed Mater Res (1991) 25, 1397

Protein adsorption form human plasma


Validation of an MPC Polymer Coating to Attenuate Surface-Induced Crosstalk between the Complement and Coagulation Systems in Whole Blood in In Vitro and In Vivo Models

Surface‐induced activation of whole blood in tubing loops. Blood (with 0.5 IU heparin mL−1) was circulated in the loops at 37°C for 1 or 4 h.

Platelets remained TAT

C3a sC5b-9

Stained with rhodamine 6G to visualize the MPC polymer layer

The catheters were observed after 1h-contact with whole blood

Blood compatibility on MPC polymers

Y. Teramura et al., Macromol Biosci (2019) 19, 1800485

PMB30Hep

ControlPMB30


Artificial hearts with MPC polymer surface

Takatani, et al., Artif Organs (2011)

Abe, et al., Artif Organs (2015)

Ishihara, et al., J Congestive Heart Failure Circulatory Support (2001)


Chest X‐ray photoimage

More than 160 patients have been operated in Japan and most longest implantation period is around 14 years

Implantable blood pump (Artificial Heart: EVAHEART)

Dr. Kenji YamazakiHokkaido Cardiovascular Hospital


Second patient successfully moved to heart transplantation. Implantation period: 1165 days

No clot formation was observed at any part of the device.

Inflow cannula

Pump casing

Implantable blood pump (Artificial Heart)

impeller


MPC polymer-modified medical devices


Medical device Product name Manufacturer Clinical introduction year

Guide wire Hunter® Biocompatible 1997 (FDA approval: K970938)

Stent BiodivYsioTM Biocompatible 2000

TriMaxx® Abbott Laboratories 2007Drug eluting

stent DexametTM Biocompatible 2001

Endeavor® Medtronic 2008

Artificial lung(Oxygenator) Physio® Sorin Biomedica 2006

(FDA approval: K061031)Oxia ICN® (Legacoat) JMS 2015

Microcatheter Londis® Clinical Supply/Termo MHLW approval

Catheter Eliminate® Clinical Supply/Termo MHLW approvalArtificial heart

(LVAD) Evaheart® Sun Medical 2011


MPC polymer-modified medical devices

CNT

Drug eluting stent Artificial lung

Artificial heart

Contact lenses

Artificial joint CH3

C)n

C O


(CH2

O

O

MPC polymer


Biomaterials Laboratory, The University of Tokyo Y. Iwasaki, K. Ishihara, J Artif Organs (2003) 6, 260

PMPU

Antithrombogenic hollow fibers

Hollow fiberOuter coagulant

(water)

Wet processing 18% PSf and 3% PVPyin DMAcInner coagulant

(40 % DMAc aq. orPMPU in 40 % DMAc aq.)

PMPU

Double injection nozzle

PVPy-alloyed hollow fiber PMPU-coated hollow fiber


MinihemodialyzerMembrane area: 100 cm2


2.5 cm

PSf APS(Asahi Med.) PVPy-alloyed PMPU-coated


PSf

APS(Asahi Med.)

PVPy-alloyed

PMPU-coated



Permeation ability for cytochrome C (Mw=1.23kDa) in 10% bovine serum.

APS(Asahi Med.) PVPy-alloyed

PMPU-coated

APS(Asahi Med.) PVPy-alloyed PMPU-coatedTEM image of membrane interface. Dark layer corresponded to protein adsorption layer.


Permeation time (min)


PVPy-alloyed PMPU-coated

Macroscopic observation

SEM observation

Non‐heparin

A-V shunt for 60 min

Ex vivo whole blood contacting test was carried out for 1 h without anticoagulant.


Y. Iwasaki, K. Ishihara, J Artif Organs (2003) 6, 260

No cell adhesion and coagulation was observed on the PMPU-coated follow fibers.


Bioinspired phospholipid polymer, MPC polymer shows excellent performance to prevent thrombus formation.

The MPC polymer can conjugate with medical devices by convenient process.

This performance strongly depends on the nature of water at the MPC surface.

Conclusion


http://www.mpc.t.u-tokyo.ac.jp

Acknowledgements

Documents

Antithrombogenicinterfaces based on the phospholipid