week #7 novel pharmaceutical particles · nus presentation title 2001 novel fabrication of...

Week #7 Novel Pharmaceutical

ParticlesChi-Hwa Wang

Department of Chemical and Biomolecular Engineering, National

University of Singapore, 4 Engineering Drive 4, Singapore, 117576,

Singapore. E-mail: [email protected].

Advanced Drug Delivery Systems

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: 3321-3332

Xie 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

0

n n g n n

r r g r r

V V V V V

V V V V V

Droplet Size Variation with Different Ring

Electrical Potential (Vr)

0

20

40

60

80

100

120

140

1.5 3.5 5.5 7.5 9.5Vr (kV)

Dro

ple

t S

ize (

mic

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 process

320 micron

Taylor Cone

Jet

Droplet

Formation

Nozzle Wall

The Front Tracking/Finite Difference CFD simulation wasable to replicate all observable phenomenon of the EHDAprocess, including the Taylor Cone, Jet and the dropletformation process.Since the electrical charge resides on the surface of theliquid, the electrical field accelerates the surface of theliquid, and results in the formation of the circulating fluidinside the Taylor cone.

Fluid: Dichloromethane; Flowrate: 6ml/h; Vn=8kV, Vr=8.9kV

Nozzle inner radius: 110 micron; Nozzle outer radius: 170 micron

Nozzle 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.



Nozzle to Ring: 10mm; Nozzle to Ground: 100mm;

Ring Diameter: 40mm

Closer look of Taylor Cone formation

CFD simulation Experimental

Fluid flow field



Nozzle 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 Nozzle

parameters 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



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 ± 1.7

S3 8.4 84.1 14.2 ± 2.2

S4 15.8 78.1 15.1 ± 0.7

S5 0 - 12.6 ± 0.8

S1 - Paclitaxel-loaded PCL microspheres

S2 - Paclitaxel-loaded PLGA microspheres

S3 - Paclitaxel-loaded PLGA particles of biconcave shape

S4 – Paclitaxel-loaded PLGA microspheres

S5 – Blank PLGA microspheres

EHDA Microparticles

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.


In vitro release

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

Time (day)

Cu

mu

lati

ve r

elea

se (

%)

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.

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.

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

0%

20%

40%

60%

80%

100%

120%

0 20 40 60 80 100 120 140 160

Taxol concentration

Cell

via

bil

ity (

%)

1day

2days

3days

4days

5days

0%

20%

40%

60%

80%

100%

120%

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)

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.


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-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).


Cell viability after 72h incubation with different formulations.

0

20

40

60

80

100

120

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

Different formulations

Cel

l v

iab

ilit

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 tumours after 21days of C6 glioma cells implantation

Blank

Microspheres

Taxol®

10% Taxol

loading EHDA

Microparticles

20% Taxol

loading EHDA

Microparticles



Tumor volume response: Paclitaxel EHDA Microparticles

0

10

20

30

40

50

60

70

0 5 10 15 20 25 30 35 40

Time (day)

Cum

ulat

ive

rele

ase

(%)

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.

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20 25 30 35 40Time (days)

Tu

mo

re v

olu

me (

mm

3)

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

0.50

1.00

1.50

2.00

2.50

3.00

3.50

2 7 10 14 17 21 28

Days after Implantation

ng

Paclita

xel/ m

l P

lasm

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 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 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

polymeric fluid in the presence of strong electric field. After the fluid evaporates, fibers can be

formed.

Typical biomedical devices including gel microbeads, microparticles, films and

fibers.

Representative optical images of C6 glioma cells after

being treated by different concentrations of

paclitaxel-loaded PLGA microparticles

Typical jet of electrospray and electrospinning

Tumor volume variation with time

Biomedical 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 Fabrication

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

Electrohydrodynamic atomization (EHDA)(Micro and nanopartices)

Dialysis (nanoparticles)

Spray drying (Microparticles)

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)

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 productOrganic

solvent

Polymer Drug

Capillary nozzle

Small orifice

Coaxial nozzles

Assisted jet breakup

Enhanced mixing

Ultrasonic nozzles

Uniform atomization

Enhanced mass transfer in vessel

Hydrodynamics and thermodynamics

Both hydrodynamics and thermodynamics play a role in influencing the Supercritical antisolvent process for polymer particle formation

Diego 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 size

Above 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 size

Fibers 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 C

Varying operating pressure73.8 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 pump

3. VentingOrganic solvent – CO2 mixture was vented off to a fume cupboard from the bottom of the vesselFilter frit (0.22mm) 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 length is dependent on spray Reynolds

number

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

Effect of varying pressure

Results obtainedParticle sizes of 5 – 10 mm 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 mmSD: 2.25 mm


0

2

4

6

8

10

12

14

16

18

0.6 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 6 6.6 7.2 7.8 8.4 9 9.6

Particle size (mm)

Coun

t int

ensi

ty (%

)

6ml/min

0

2

4

6

8

10

12

0.6 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 6 6.6 7.2 7.8 8.4 9 9.6

Particle size (mm)

Coun

t int

ensit

y (%

)4ml/min

Effect of varying flowrate

Results obtainedAt 90 bar and 35 deg C, powdery particles with little/no agglomeration were obtained

Particles obtained have similar surface morphologies

Polydispersed particlesClusters of small particles (< 2 mm)

Larger particles (2-10 mm)

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

Shorter jet breakup length

Better mass transfer between the organic solvent and supercritical CO2

Modified SASEM setup

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

Effect of ultrasonicationComparison of SAS (No external mixing) and modified SASEM

10w/w% paclitaxel loaded PLA particles

2% polymer loading in DCM

No ultrasonication

Polydispersed particles obtained


Effect of ultrasonication

Particles obtained with ultrasonication

30 mm vibration amplitude 10% of maximum vibration


Effect of ultrasonication

Particles obtained with ultrasonication



Particle propertiesParticle size and size distribution tends to decrease as vibration amplitude increases

Recovery yield was comparable to conventional spray drying methods

Differential scanning calorimetry was performed to determine the crystalline state of particles fabricated using the SAS/ modified SASEM setup

Encapsulation efficiency and in vitro release profile of the particles were determined

EE% of as high as 80% were obtained

0

10

20

30

40

50

60

70

80

90

0 30 60 90 120

Ultrasonic vibration amplitude (micron)

(%)

Recovery yield (%)

Encapsulatution efficiency (%)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 30 60 90 120

Ultrasonic vibration amplitude (micron)

Part

icle

siz

e (

nm

)

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 C

PLLAMelting point @ 172-178 deg C

Thermogram properties

-20

-15

-10

-5

0

5

10

15

20

0 50 100 150 200 250 300

Temperature (oC)

Ex

oth

erm

(m

W)

Raw paclitaxel

raw PLA (before SAS process)

Paclitaxel loaded PLA withultrasonication

Blank PLA with ultrasonication

In vitro release profiles

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40

Release time (days)

Cu

mu

lati

ve

re

lea

se (

%)

S1

S2

S3

Particles suspended in phosphate buffered saline (PBS)

Placed in shaker bath (120 rpm, 37 deg C)

Removed at predetermined time intervalsSolution was centrifuged and buffer solution was removed

Fresh 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 (mm)

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

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

Time (days)

Cum

ulat

ive

rele

ase

(%)

S3A

S5A

S1A

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: 6516-5079

E-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

week #7 novel pharmaceutical particles · nus presentation title 2001 novel fabrication of...

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