Week #7 Novel Pharmaceutical Particles Chi-Hwa Wang Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering

Week #7 Novel Pharmaceutical Particles

Chi-Hwa WangDepartment of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117576,

Singapore. E-mail: [email protected].

Advanced Drug Delivery Advanced Drug Delivery SystemsSystems

Optimized Strategy for Cancer Therapy

Computation Simulation and Optimization

Patient Specific Treatment

Novel Fabrication of Nano-/Micro-particles

NUS Presentation Title 2001

Novel Fabrication of Pharmaceutical Particles

Electrohydrodynamic atomization applications Micro- and nanofibers.

Thin films.

Micro- and nanoparticles.

Microencapsulation of living cells, DNA etc.

Paclitaxel Chemotherapy & radiotherapy for brain tumors.

Penetrates the blood-brain barrier poorly.

Ijsebaert J. C., K. B. Geerse, J. C. M. Marijnissen, J. J. Lammers, P. Zanen. Electro-hydrodynamic atomization of drug solutions for inhalation purposes, J. Appl. Physiol. (2001) 91: 2735-2741.Loscertales I. G., A. Barrero, I. Guerrero, R. Cortijo, M. Marquez, A. M. Ganan-Calvo. Micro/nano encapsulation via electrified coaxial liquid jets, Science (2002) 295: 1695-1698. Ding L. N., T. Lee, C. H. Wang. Fabrication of monodispersed Taxol-loaded particles using electrohydrodynamic atomization, J. Control. Rel. (2005) 102(2):.395-413. Xie J., C.M.M Jan, C.H. Wang. Microparticles developed by electrohydrodynamic atomization for the local delivery of anticancer drug to treat C6 glioma in vitro. Biomaterials (2006) 27: 3321-3332Xie J., C.H. Wang, “Electrospun micro- and nanofibers for sustained delivery of paclitaxel to treat C6 glioma in vitro” Pharmaceutical Research , (2006) 23, 1817-1826.Xie J., L.K. Lim, Y. Phua, J. Hua, C.H. Wang “Electrohydrodynamic atomization for biodegradable polymeric particle production” J. Colloid & Interface Sci., 302, 103–112 (2006).


: the trace of protective Nitrogen;: solvent with polymer & drugs;: volatilized solvent;: collected polymer & drug particles;

Vn : high voltage used to break liquid drops; Vr : high voltage applied to metal hoop;

Syringe

Using electric field to break liquid drops into fine droplets

Vn

Vr

Vacuum pump

Filter

Particles

2N

Electro-hydrodynamic Atomization Process

NUS Presentation Title 2001Electrohydrodynamic atomization process

0gV

Electrohydrodynamic atomization is an atomization method based on the application of an electrical stress on the fluid that emerges from the tip of the nozzle. A Taylor cone, which is formed due to the acceleration of the fluid by the applied electrical stress, reduces the diameter of the jet, so that a thin jet is formed at the tip of the Taylor cone. Depending on the solution properties, either discrete particles or strands of fibers can be formed using the same equipment.

0

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n n g n n

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Droplet Size Variation with Different Ring Electrical Potential (Vr)

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1.5 3.5 5.5 7.5 9.5Vr (kV)

Dro

ple

t S

ize (

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ron)

Vn=5kV, 3ml/h

Vn=8kV, 3ml/h

Linear (Vn=5kV, 3ml/h)

Linear (Vn=8kV, 3ml/h)

I: changes in droplet size when Vn is kept at 5kV. II: changes in droplet size when Vn is kept at 8kV.

II

I

Particle Size Droplet Size Varying VrMass balance Modulation

Taylor Cone, jet and droplet formation processTaylor Cone, jet and droplet formation process

320 micron

Taylor Cone

Jet

Droplet Formation

Nozzle Wall

The Front Tracking/Finite Difference CFD simulation was able to replicate all observable phenomenon of the EHDA process, including the Taylor Cone, Jet and the droplet formation process.Since the electrical charge resides on the surface of the liquid, the electrical field accelerates the surface of the liquid, and results in the formation of the circulating fluid inside the Taylor cone.

Fluid: Dichloromethane; Flowrate: 6ml/h; Vn=8kV, Vr=8.9kVNozzle inner radius: 110 micron; Nozzle outer radius: 170 micronNozzle to Ring: 10mm; Nozzle to Ground: 100mm; Ring Diameter: 40mm

Taylor Cone, jet and droplet formation process

Nozzle Diameter ~ 340micron Droplet Diameter ~ 50micron

A: Eggers, J. Fluid. Mech., 262, 205, 1994;B: CFD simulation results;C: Chaudhary, J. Fluid. Mech., 96, 275, 1980

A B CA transient CFD simulation was done, so that the formation of the Taylor Cone, jet and droplet was captured with time. Droplet formation was also simulated and the simulated droplet size can be obtained directly from the simulation data.

Fluid: Dichloromethane; Flowrate: 6ml/h; Vn=8kV, Vr=8.9kVNozzle inner radius: 110 micron; Nozzle outer radius: 170 micronNozzle to Ring: 10mm; Nozzle to Ground: 100mm;Ring Diameter: 40mm

Closer look of Taylor Cone formation

CFD simulation Experimental

Fluid flow field

Fluid: Dichloromethane; Flowrate: 6ml/h; Vn=8kV, Vr=8.9kVNozzle inner radius: 110 micron; Nozzle outer radius: 170 micronNozzle to Ring: 10mm; Nozzle to Ground: 100mm;Ring Diameter: 40mm

The Taylor Cone is an important phenomenon in the EHDA process, enabling the formation of thin jet that is at least one order of magnitude smaller than the inner diameter of the nozzle, resulting in droplets that is smaller than the inner diameter of the nozzle. The Taylor cone angle is also a useful parameter for comparison between the experimental and the simulation results.


Taylor cone

Jet

Charged droplets

J. Xie, J. C. M. Marijnissen, C. H. Wang. Biomaterials. 27: 3321-3332 (2006). J. Xie, L. K. Lim, Y. Y. Phua, J. Hua, C. H. Wang. Journal of Colloids and Interface Science. 302, 103–112 (2006).

Electrohydrodynamic Atomization


Different polymer solution flow rates.

a: 3.0 ml/h size: 11±0.8μm;

b: 1.0 ml/h size: 6.5±0.8μm;

c: 0.5 ml/h size: 4.9±0.8μm.

d: 3ml/h size 17μm;

e: 10ml/h size 26μm;

f: 15ml/h size 32μm.

(a)

(b)

(c)

(d)

(e)

(f)

2/16

1

2

40 QI

Qcd

21

KQI

EHDA Microparticles

K: Conductivity

Q: flow rate

d: diameter of droplets

γ: surface tension I: current

Xie J, Jan CMM, Wang CH. Microparticles developed by electrohydrodynamic atomization for the local delivery of anticancer drug to treat C6 glioma in vitro. Biomaterials 2006; 27: 3321-3332


c d

e f

a b

g

SEM images microparticles (a, b: S1; c, d: S2; e, f: S3; g, h: S4)

Operating Polymer Polymer Polymer solution Air flow The voltage The voltage Nozzleparameters concentration flow rate rate of nozzle of ring size

Samples S1 PCL 6% 3ml/h 25L/min 9.8kV 7.1kV 0.91mm S2 PLGA 8% 5ml/h 25L/min 10.0kV 9.0kV 0.91mm S3 PLGA 8% 5ml/h 25L/min 10.0kV 9.0kV 0.91mm S4 PLGA 8% 5ml/h 25L/min 10.0kV 9.0kV 0.91mm

Variation of operating parameters results in controllable size and morphology of microparticles.

EHDA Microparticles

h

Xie J, Jan CMM, Wang CH. Microparticles developed by electrohydrodynamic atomization for the local delivery of anticancer drug to treat C6 glioma in vitro. Biomaterials 2006; 27: 3321-3332.


Characterization for samples S1 – S5.

Samples Drug loading (%) Encapsulation Efficiency (%) Particle size (μm) ± SD

S1 8.1 81.3 11.4 ± 0.9 S2 7.9 82.3 15.2 ± 1.7S3 8.4 84.1 14.2 ± 2.2S4 15.8 78.1 15.1 ± 0.7 S5 0 - 12.6 ± 0.8

S1 - Paclitaxel-loaded PCL microspheresS2 - Paclitaxel-loaded PLGA microspheresS3 - Paclitaxel-loaded PLGA particles of biconcave shapeS4 – Paclitaxel-loaded PLGA microspheres S5 – Blank PLGA microspheres

EHDA Microparticles



In vitro release

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Cu

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%) S1

S2

S3

S4

S1: 10% PCL Microspheres

S2: 10% PLGA Microspheres

S3: 10% PLGA Biconcave

S4: 20% PLGA Microspheres

EHDA Microparticles

Paclitaxel-loaded PLGA microparticles could release faster than paclitaxel-loaded PCL microparticles. Biconcave-shaped PLGA microparticles may release slightly faster than PLGA microspheres. 20% paclitaxel-loaded PLGA microparticles could release slightly

faster than 10% paclitaxel-loaded samples. The total amount of paclitaxel released seemed to be less than 60% of the total amount of drug in the microparticles.

Initial burst due to dissolution and diffusion of paclitaxel on the surface layer of the microspheres proved by XPS results.


NUS Presentation Title 2001(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

Representative optical images of C6 glioma cells after being treated by paclitaxel-loaded PLGA microparticles ( 50μm). a, b, c: 250μg/ml 1, 2, 5 day; d, e, f: 1250μg/ml 1, 2, 5day; g, h, i: 2000μg/ml 1, 2, 5 day.

EHDA Microparticles

Optical microscope


Cell viability

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120%

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Taxol concentration

Cell

via

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%)

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0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750

Paclitaxel-loaded PLGA microparticle concentration

Cell

via

bil

ity (

%)

1day

2days

3days

4days

5days

EHDA Microparticles

The values of IC50 for Taxol and paclitaxel-loaded microspheres after 5days are around 14μg/ml and 160μg/ml, respectively. (Actual amount of paclitaxel: 160×10%*0.8=12.8

μg/ml). IC50 (inhibitory concentration 50%) represents the concentration of a drug that is required for 50% inhibition in vitro.

(μg/ml) (μg/ml)



Electrospinning

Taylor cone

Jet

Fibers

Representative image of electrospinning jet with the exposure time of 10ms. Schematic of electrospinning setup


0mM 1mM 5mM

0mM 10mM 15mM

0mM 1mM 5mM

1mM 5mM 15mM

15%

10%

2%

110±16nm 100±14nm

82±11nm

45±7nm 31±5nm

Tetrabutylammonium tetraphenylborate (TATPB)

Ionic surfactant

Increasing conductivity

Polymer concentration

5%


SEM images of paclitaxel-loaded PLGA Fibers

before release

Electrospun Micro- and Nano-fibers

10% paclitaxel-loaded

PLGA microfiber

10% paclitaxel-loaded

PLGA nanofiber

Diameter: 14.5mm

Thickness: 1mm

http://www.drugs.com/PDR/Gliadel_Wafer.html

Samples Fibers mean diameter Drug loading (%) Encapsulation efficiency (%)

PLGA MF (s1) 2.5±0.32 µm 9.9±0.1 99.0±1.0

PLGA NF (s2) 770±13 nm 9.2±0.03 92.0±0.3

Characterization of paclitaxel-loaded fibers

Cross section


Results and discussion

Laser scanning confocal microscopy images

Cell morphology after 72h incubation with different formulations

Blank PLGA nanofibers 10% Paclitaxel-loaded PLGA nanofibers 500µg/ml

10% Paclitaxel-loaded PLGA nanofibers 1000µg/ml

10% Paclitaxel-loaded PLGA nanofibers 2000µg/ml

10× green colour indicates living cells stained with FDA

Electrospinning Micro- and Nano-fibersJ. Xie, C.H. Wang, “Electrospun Micro- and Nanofibers for Sustained Delivery of Paclitaxel to Treat C6 Glioma In Vitro” Pharmaceutical Research , 23, 1817-1826 (2006).


Cell viability after 72h incubation with different formulations.

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Control Blank PLGA NF PLGA NF 500 PLGA NF 1000 PLGA NF 2000

Different formulations

Cel

l v

iab

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y (

%)

PLGA NF500: 500µg/ml; PLGA NF 1000: 1000µg/ml; PLGA NF 2000: 2000µg/ml.

Results and discussion

The IC50 value of paclitaxel-loaded PLGA nanofibers was around 1200µg/well.

IC50 of paclitaxel of this formulation was about 36µg/ml, which was comparable to the commercial paclitaxel formulation Taxol® (30µg/ml).

Electrospinning Micro- and Nano-fibers

J. Xie, C.H. Wang, “Electrospun Micro- and Nanofibers for Sustained Delivery of Paclitaxel to Treat C6 Glioma In Vitro” Pharmaceutical Research , 23, 1817-1826 (2006).


In-Vovo Experiment Overview: Tumor Volume Response

Subcutaneous Inoculation with 1x 106 C6 giloma cells

After period of tumor growth, Microparticles, Discs or Microspheres are implanted

Disc (Surgical Implantation)

Microspheres (Surgical Implantation)

Microparticles(Intra-tumor injection)

Balb/c Nude mice

2

6

1_ abVolTumor

b

a

Representative pictures of Representative pictures of tumours tumours after 21days of C6 glioma cells after 21days of C6 glioma cells implantationimplantationBlank

Microspheres

Taxol®

10% Taxol loading EHDA Microparticles

20% Taxol loading EHDA Microparticles



Tumor volume response: Paclitaxel EHDA Microparticles

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(%

)

10% PLGA EHDA Microparticles

20% PLGA EHDA Microparticles

EHDA Microparticles in

vitro release profile

Tumor was allowed to grow for a period of 14 days before 1st injection of microparticles and commercial taxol (for control were administered) directly into the tumor mass.

20% Taxol Loading group had 1 mg taxol administered in two doses of 0.5 mg as injection directly into the tumor on Day 14 & 21.

Significant tumor growth suppression for at least 7 days after first injection (30 % in vitro release reached).

Tumor volume is among lowest of treatment (see next slide).

No significant variation of animal weight from controls were observed. Indicating minimal or no systemic toxicity effects.

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Blank Microparticles

Commercial Taxol - 1 mg Taxol

Microparticle 20% Taxol Loading - 1 mg Taxol


Weight loss observed in control group over first seven days.

No weight loss observed for EHDA group.

Control group showed Paclitaxel cleared from Plasma after 10 days.

Sustained delivery observed for Experimental group for up to 28 days.

In vivo release profile of EHDA microparticles

In vivo release profile for 14.8% Drug Loaded EHDA Microparticles

0.00

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Days after Implantation

ng P

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a

EHDA Microparticles

Control

23.6 ± 6.5 ng/ml

EHDA microparticles

Control

Days after implantation

14% drug loaded EHDA microparticles


The research efforts of this project are to develop various biomedical devices for applications in controlled release of bioactive materials using electrohydrodynamic atomization techniques. Through investigation of the processing parameters during the EHDA process, controllable size and morphology of particles, controllable diameters of fibers and controllable thicknesses of films were successfully achieved.

Electrohydrodynamic atomization (EHDA) is a process, also called electrospray, where a liquid Electrohydrodynamic atomization (EHDA) is a process, also called electrospray, where a liquid jet breaks up into fine droplets under the influence of electrical forces. With increasing electric jet breaks up into fine droplets under the influence of electrical forces. With increasing electric forces, different spray modes can be obtained from dripping mode, single cone-jet mode to forces, different spray modes can be obtained from dripping mode, single cone-jet mode to multiple-cone mode. After the solvent evaporates, polymeric particles can be obtained.multiple-cone mode. After the solvent evaporates, polymeric particles can be obtained.

Electrospinning of liquids involves the introduction of electrostatic charges to a stream of Electrospinning of liquids involves the introduction of electrostatic charges to a stream of polymeric fluid in the presence of strong electric field. After the fluid evaporates, fibers can be polymeric fluid in the presence of strong electric field. After the fluid evaporates, fibers can be formed.formed.

Typical biomedical devices including gel microbeads, microparticles, films and Typical biomedical devices including gel microbeads, microparticles, films and fibers.fibers.

Representative optical images of C6 glioma cells after being treated by different concentrations of

paclitaxel-loaded PLGA microparticles

Typical jet of electrospray and electrospinningTypical jet of electrospray and electrospinning

Tumor volume variation with timeTumor volume variation with time

Biomedical Devices Developed by Electrohydrodynamic Atomization (EHDA) TechniqueBiomedical Devices Developed by Electrohydrodynamic Atomization (EHDA) Technique

Particle Fabrication Techniques for Pharmaceutical Applications

Singapore-MIT Alliance

Nanoparticle fabrication of biodegradable polymers using supercritical antisolvent: Effects of mixing and thermodynamic properties

Nanoparticle fabricationMethods of FabricationMethods of Fabrication

Emulsion methods (O/W; W1/O/W2)Emulsion methods (O/W; W1/O/W2)

Electrohydrodynamic atomization (EHDA)(Micro and nanopartices)

Electrohydrodynamic atomization (EHDA)(Micro and nanopartices)

Dialysis (nanoparticles)Dialysis (nanoparticles)

Spray drying (Microparticles)Spray drying (Microparticles)

Supercritical fluid techniques

(Micro and nanoparticles)

Supercritical fluid techniques

(Micro and nanoparticles)

RESS Rapid Expansion of Supercritical Solutions(Debenedetti et al. (1993) Fluid Phase Equilibria 82, 311-321)

ASES Aerosol Solvent Extraction System(Bleich et al. (1993) Int. J. Pharma., 97, 111-117)

SEDS Solution Enhanced Dispersion by Supercritical Fluids

(Ghaderi et al. (1999) Pharma. Res., 16(5), 676 – 681)

SAS Supercritical AntiSolvent(Reverchon et al. (2003) Ind. Eng, Chem. Res., 42, 6405 – 6414)

SASEM Supercritical Antisolvent with Enhanced Mass Transfer

(Chattopadhyay et al. (2002) Ind Eng Chem Res., 41, 6049 – 6058)

RESS Rapid Expansion of Supercritical Solutions(Debenedetti et al. (1993) Fluid Phase Equilibria 82, 311-321)

ASES Aerosol Solvent Extraction System(Bleich et al. (1993) Int. J. Pharma., 97, 111-117)

SEDS Solution Enhanced Dispersion by Supercritical Fluids

(Ghaderi et al. (1999) Pharma. Res., 16(5), 676 – 681)

SAS Supercritical AntiSolvent(Reverchon et al. (2003) Ind. Eng, Chem. Res., 42, 6405 – 6414)

SASEM Supercritical Antisolvent with Enhanced Mass Transfer

(Chattopadhyay et al. (2002) Ind Eng Chem Res., 41, 6049 – 6058)

Advantages of CO2

•“green” solvent, environmentally benign•Readily available and inexpensive

•Low critical pressure and temperatures

Advantages of CO2

•“green” solvent, environmentally benign•Readily available and inexpensive

•Low critical pressure and temperatures

Supercritical antisolventMost organic solvents are soluble in supercritical CO2

Low critical temperature (31.1 deg C)Suitable for processing thermally labile pharmaceuticals

Removal of organic solvent from productOrganicsolvent

Polymer Drug

Capillary nozzleSmall orifice

Coaxial nozzlesAssisted jet breakupEnhanced mixing

Ultrasonic nozzlesUniform atomizationEnhanced mass transfer in vessel

Capillary nozzleSmall orifice

Coaxial nozzlesAssisted jet breakupEnhanced mixing

Ultrasonic nozzlesUniform atomizationEnhanced mass transfer in vessel

Hydrodynamics and thermodynamics

Both hydrodynamics and thermodynamics play a role in influencing the Supercritical antisolvent process for polymer particle formationDiego and coworkers (2005) identified the two regimes of particle formation for precipitation of polymers in the PCA process

Below mixture critical pressure, the solution droplets were obtained and mass transfer takes place between the solution droplets and CO2

Initial size of droplets influences the particle sizeAbove mixture critical pressure, solution enters the supercritical CO2 as a gaseous plume

Turbulent mixing of solution and CO2

Mass transfer and mixing influence the particle sizeFibers or discrete particle may be obtained

Diego et al. (2005) Operating regimes and mechanism of particle formation during the precipitation of polymers using the PCA process. J. Supercritical fluids, 35, 147 - 156

HydrodynamicsCarretier and coworkers (2003) investigated the hydrodynamics of the SAS process for precipitation of PLA particles from methylene chloride (DCM) solutionJet formation and breakup at supercritical pressures

Varying liquid flow rates (0.25 – 3 ml/min)Jet breakup length dependent on the spray Reynolds numberFibers or microparticles were obtained depending on liquid flow rates

Chattopadhyay and Gupta (2001) developed the supercritical antisolvent with enhanced mass transfer (SASEM) for production of uniform sized nanoparticles

Ultrasonic assisted atomization of jetEnhanced mass transfer between organic solution and supercritical CO2 phases

E. Carretier et al. (2003) Hydrodynamics of Supercritical Antisolvent Precipitation: Characterization and influence on particle morphology. Ind. Eng, Chem, Res, 42, 331 – 338

P. Chattopadhyay and R. B. Gupta, Production of griseofulvin nanoparticles using supercritical CO2 antisolvent with enhanced mass transfer. Int. J. Pharma. 228 (2001) 19 – 31

ObjectivesFabrication of nanoparticles of biodegradable polymers

Controlled release purposesModel drug: Paclitaxel (hydrophobic)Polymer studied: Poly L lactide (PLA)Organic solvent used: Methylene chloride (DCM)

1. Effect of thermodynamic conditions on particle propertiesConstant operating temperature

35 deg CVarying operating pressure

73.8 bar – 95 bar

2. Effect of hydrodynamicsJet formation in supercritical fluid

Jet flow rate

3. Effect of mixing on particle formationSupercritical antisolvent (SAS) processUltrasonication for mixing with the high pressure vessel

SAS setup

P1

P2 TC

PI

V2

V1

V3F2

F1

C2

CO2

C1

Modified SASEM setup

U1

P1

P2 TC

PI

V2

V1

V3F2

F1

C2

CO2

C1

U1: Ultrasonic system; Branson sonifier and converter, Sonics and Materials probe (3/8” probe tip diameter)

Particle fabrication1. Pressurization (CO2)

High pressure pump was used to deliver liquefied CO2 to high pressure vesselTemperature in high pressure vessel was maintained using circulating water bath

2. Spraying (Organic solution jet)High pressure liquid pump was used to deliver organic solution (Solvent + pharmaceutical) into the high pressure vessel via a capillary nozzle

Vertical jet (SAS)Horizontal jet (modified SASEM with ultrasonication)

Flowrate may be controlled by HPLC pump3. Venting

Organic solvent – CO2 mixture was vented off to a fume cupboard from the bottom of the vesselFilter frit (0.22m) was placed at bottom of the vessel to collect particles

4. PurgingVessel was purged using fresh CO2 to remove any remaining organic solvent

SAS setupJet breakup after

entering high pressure CO2

Jet breakup after entering high pressure CO2

Jet breakup length is

dependent on spray Reynolds

number

Jet breakup length is

dependent on spray Reynolds

number

No external mixing in the high pressure vessel during precipitation

No external mixing in the high pressure vessel during precipitation

Flow rate = 4ml/minReynolds number = 292

Effect of varying pressureExperimental conditions

Solution flow rate was kept constant at 4ml/min

System temperature was maintained at 35 deg C

2% polymer loading in DCM

Pressure varied from 73.8 to 95 bars

73.8 bars 80 bars

Effect of varying pressure

90 bars 95 bars

Smoother surface morphology particles obtainedParticle sizes were highly polydispersed

Smoother surface morphology particles obtainedParticle sizes were highly polydispersed

Effect of varying pressure

Results obtainedParticle sizes of 5 – 10 m were obtainedAt 73.8 bars, particles obtained were agglomerated and surfaces were very roughAt 80 bars and above, spherical particles with little agglomeration were achievedAs supercritical pressure increases, particle morphology improves

For particles obtained at 90 and 95 bars, smooth surface morphology were obtained

This suggests that as pressure increases, better mass transfer between CO2 and DCM during the spraying process

More rapid precipitationLess agglomeration

Effect of varying solution flowrateTemperature: 35 deg CPressure: 90 bars2% polymer loading in DCMSolution flowrate of 2, 4, 6 ml/min

2 ml/min

4 ml/min

6 ml/min

Effect of varying solution flowrate

Mean Size: 3.03 mSD: 2.25 mMean Size: 3.03 mSD: 2.25 m

Mean Size: 2.05 mSD: 1.21 mMean Size: 2.05 mSD: 1.21 m

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Effect of varying flowrate

Results obtainedAt 90 bar and 35 deg C, powdery particles with little/no agglomeration were obtainedParticles obtained have similar surface morphologies Polydispersed particles

Clusters of small particles (< 2 m)Larger particles (2-10 m)

Higher liquid flowrate generally decreases the particle size for the larger particles

Shorter jet breakup lengthBetter mass transfer between the organic solvent and supercritical CO2

Modified SASEM setupJet breakup is not due to liquid film

disintegration from ultrasonic

vibrating surface

Jet breakup is not due to liquid film

disintegration from ultrasonic

vibrating surface

Jet break up Turbulence and mixing

Enhanced turbulence and mixing of jet in

the high pressure cell due to ultrasonic vibration

Enhanced turbulence and mixing of jet in

the high pressure cell due to ultrasonic vibration

Effect of ultrasonicationComparison of SAS (No external mixing) and modified SASEM10w/w% paclitaxel loaded PLA particles 2% polymer loading in DCM

No ultrasonication

Polydispersed particles obtained

Mean Size: 4.13 mSD: 1.98 m

Polydispersed particles obtained

Mean Size: 4.13 mSD: 1.98 m

Effect of ultrasonicationParticles obtained with ultrasonication

30 m vibration amplitude 10% of maximum vibration


Effect of ultrasonicationParticles obtained with ultrasonication


120 m vibration amplitude

40% of maximum vibration

Particle propertiesParticle size and size distribution tends to decrease as vibration amplitude increasesRecovery yield was comparable to conventional spray drying methodsDifferential scanning calorimetry was performed to determine the crystalline state of particles fabricated using the SAS/ modified SASEM setupEncapsulation efficiency and in vitro release profile of the particles were determined

EE% of as high as 80% were obtained

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Encapsulatution efficiency (%)

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Differential scanning calorimetry analysis

Thermogram analysis is an useful tool to determine whether paclitaxel is molecularly dispersed in the polymer matrix or phase separated as paclitaxel crystals

DSC analysisTemperature range = 20 – 280 deg CTemperature ramp speed = 10 deg C/minNitrogen flow rate = 5ml/min

Literature valuesPure paclitaxel

Endothermic peak @ 223.0 deg CPLLA

Melting point @ 172-178 deg C

Thermogram properties

-20

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raw PLA (before SAS process)

Paclitaxel loaded PLA withultrasonication

Blank PLA with ultrasonication

In vitro release profiles

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Release time (days)

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S2

S3

Particles suspended in phosphate buffered saline (PBS)Placed in shaker bath (120 rpm, 37 deg C)Removed at predetermined time intervals

Solution was centrifuged and buffer solution was removedFresh PBS was added

Paclitaxel content in PBS was extracted and analysed using HPLC

Particles suspended in phosphate buffered saline (PBS)Placed in shaker bath (120 rpm, 37 deg C)Removed at predetermined time intervals

Solution was centrifuged and buffer solution was removedFresh PBS was added

Paclitaxel content in PBS was extracted and analysed using HPLC

Paclitaxel loaded PLA samples obtained using modified SASEM process

Sample Ultrasonic vibration

amplitude (m)

Recovery Yield (%)

Encapsulation efficiency (%)

Size (nm)

S1 0 21.1 70.0 ±3.5 4130 ± 198 S2 30 18.1 67.7 ± 1.4 769 ± 210

S3 60 14.6 56.4 ± 14.4 506 ± 163 S4 90 12.8 83.5 ± 0.8 486 ± 134

ConclusionsWe have successfully fabricated micro and nanoparticles of PLA for potential application in controlled release purposesThe effect of thermodynamic properties and hydrodynamics on particle formation was investigated in SAS process

Varying the operating pressure from 73.8 bar (critical pressure) to 95 bar significantly alters the surface morphology of microparticles obtained Increasing liquid flowrate reduces particle size and size distribution

The effect of ultrasonic vibration amplitude on particle size and properties was investigated

Nanoparticles were obtained using the modified SASEM setupParticle size may be altered by applying different ultrasonic vibration amplitude

The research efforts of our group are to develop controlled-release drug delivery devices using supercritical fluid techniques for

chemotherapy to treat brain and liver cancers. Through investigation of the operating parameters of the SAS and Foaming process,

controllable particle size with anticancer drug encapsulation and foams with tailored pore size have been achieved respectively. As

such, the drug release profile may be modulated.

60 bars 70 bars 80 bars

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0 5 10 15 20 25 30 35

Time (days)

Cu

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SEM images of different morphology particles obtained using SAS technique

Phase diagram for carbon dioxide

In vitro release of paclitaxel from PLA microparticlesInvestigation of Various flow regimes of

organic solution entering supercritical CO2

PLGA foams with different mean pore sizes achieved using Supercritical gas foaming technique

Contact:Prof. Wang, Chi-Hwa

Tel: 6516-5079E-mail: [email protected]

A supercritical fluid is any substance at a temperature and pressure above its thermodynamic

critical point. Supercritical fluids offer favourable gas-like transport properties and liquid-like

solubility. Supercritical CO2 is used to fabricate biodegradable polymeric controlled release

devices using Poly L lactide (PLA) and Poly DL lactide-co-glycolide (PLGA). CO2 was chosen

as it has accessible critical temperature (31.1 deg C) and pressure (73.8 Bars), tunable properties

near the critical region, is inexpensive, non-flammable, and generally environmentally benign.

The supercritical fluid fabrication techniques employed in our research group include fabrication

of microparticles using supercritical antisolvent (SAS) process, and the fabrication of micro-

porous polymeric foams using supercritical gas foaming technique. In the supercritical

antisolvent process, the jet disintegration process at near critical conditions was investigated. In

vitro release profiles and other properties of the controlled release devices were also

characterized.

Drug Delivery Devices Developed by Supercritical Fluid Technique

Documents

Week #7 Novel Pharmaceutical Particles Chi-Hwa Wang Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering