PLGA for drug delivery

Huang Juan

Huang Junlian

Saskia Huijser

Rob Duchateau

Introduction

Aliphatic polyesters have been extensively used as important biodegradable biomaterials for a wide variety of drug delivery carriers and biomedical devices.

They have biodegradability, versatile mechanical properties and proven biocompatibility.

Poly(L-lactide)(PLA) and poly(glycolide)(PGA) and poly(lactide-co-glycolide)(PLGA) are the most commonly used biodegradable and biocompatible polymers.

Synthesis of PLGA

1.Melt polycondensation: step growth

Lactic acid Glycolic acid PLGA: poly(lactic acid-co-glycolic acid)

O

HO

OH

+

O

HO OH

Ti(OBu)4

1500C-1800C

*O

O

O

O

*m n + H2O

Synthesis of PLGA

2. Ring opening polymerization: chain growth

O

C

CH

O

CH3

O

C

CH

O

CH3

O

C

O

CH2

O

C

O

CH2

n m

O

O O

O CH3

CH3

a 100 0C, 7 d / b 180 0C, 6 h

a PS lipase / b SnOct2

O

OO

O

Lactide Glycolide PLGA: poly(lactide-co-glycolide)

a) Enzyme catalystb) Metal catalyst

Enzymatic polymerization of PLGA

An increase in interest in enzyme-catalyzed organic reactions

Several advantages: Catalysis under mild reaction conditions (Temperature,

pH, Pressure) Nontoxic natural catalyst Have the ability to be used in bulk reaction media avoiding

organic solvents Several disadvantages: Long reaction time Low molecular weight

Enzyme of lipase PS

HO OH

OH2N

Red site: Histidine

Yellow site: Aspartic acid

Green site: Serine

Serine

Postulated Mechanism

OO

Lipase+ E OH

Lipase-cyclic compoundComplex

H R C

O

O E

Acyl-Enzyme Intermediate

(Enzyme-Activated Monomer,EM)Cyclic ester

Initiation

EM + R'OH HORCOR'

O

+ E(R'=H, Akyl)

Propagation

EM + H ORC OR'n

OE OH

OH

H ORC OR'n+1

O

+

R

Results and discussion

Sample EnzymeTime(d)

Conversion(%)

Mw

(kDa)PDI

PLLA PS 7 92 15.0 1.7

PLLA PS-DI 7 97 9.2 2.2

PLLA - 7 10 - -

PGA PS 2 96 13.0 2.4

PGA PS-DI 2 100 9.1 1.7

PGA - 2 0 - -

The results of PLLA and PGA with/without lipase

Reaction in bulk in 100 0C and using 8 wt % lipase

PLGA prepared by lipase at 100 0C for 7 d

Entry Samples

Feed ratio(L/G)

Polymer ratio (L/G)

EnzymeL

Conv.(%)

GConv.(%)

Mw(kDa)

PDITg

(0C)

ΔTg

(0C)

1a PLLGA 90/10 88/12 PS 89 100 13.9 1.9 50.2 3.6

2 PLLGA 80/20 77/23 PS 94 100 11.7 1.8 47.5 3.4

3 PLLGA 70/30 70/30 PS 96 100 14.6 1.9 46.4 3.8

4 PLLGA 90/10 82/18 PS-DI 74 100 6.4 1.4 45.7 4.2

5 PLLGA 80/20 69/31 PS-DI 76 100 8.7 1.5 44.7 4.0

6 PLLGA 70/30 64/36 PS-DI 86 100 7.9 1.6 44.0 3.9

7 PDLLGA 80/20 75/25 PS 85 100 10.5 2.4 36.3 5.4

8 PDLLGA 80/20 58/42 PS-DI 78 100 7.4 1.6 35.7 5.0

9b PLLGA 80/20 79/21 PS 97 100 17.8 2.2 48.3 3.9

10c PLLGA 80/20 58/42 - 19 57 1.9 1.3 n.d. n.d.

0 2 4 6 80

2000

4000

6000

8000

10000

Day

Mw

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Mw /M

n

PLLGA L/G=80/20 using 8 wt% lipase PS at 100 0C

The decrease in polymerization rate may be due to the low concentration of monomers and the high viscosity of the system.

0 2 4 6 80

20

40

60

80

100

Lactide Glycolide Lactide content (%)

Time (d)M

on

om

er

con

vers

ion

(%

)

0

20

40

60

80

100

La

ctide

con

ten

t (%)

0 2 4 6 80

1000

2000

3000

4000

5000

6000

Day

Mw

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Mw /M

n

PLLGA L/G=80/20 using 8 wt% lipase PS-DI at 100 0C

Both Mw and polydispersity increase during the reaction time. The reaction

rate of glycolide is faster than lactide.

0 2 4 6 80

10

20

30

40

50

60

70

80

90

100

110

Lactide Glycolide Lactide content

Time (d)M

on

ome

r co

nve

rsio

n (

%)

0

10

20

30

40

50

60

70

80

90

100

110

Lactid

e con

ten

t (%)

ppm (t1)4.804.905.005.105.205.30

1 2

3

45

6 7

8

1. GLGGGG or GGGGLG2. LGGGLG or GLGGL3. GGGGG4. GGGGL + LGGGG5. LLGGG + GGGLL6. LLGLL + GLGLL + LLGLG7. GGGLG + GLGGG8. Lactydyl region

1H NMR spectrum (400 MHz, DMSO-d6) of PLLGA (with 8 wt% lipase PS at 100 0C for 7 d)

a

b

ppm (f1)166.50167.00167.50168.00168.50169.00169.50

LL

LL

LG

LG

GG

GG

GL

GL

13C{1H} NMR spectra (125MHz, CDCl3) of PLLGA (carbonyl region), a) PLLGA with lipase PS-DI at 100 0C for 7 d. b) PLLGA with lipase PS at 100 0C for 7 d

LL = (ILL+ILG)/ILG

LG = (IGG+IGL)/IGL

NMR CNMR H 13

L

G1

L

G

L

L

n

n

(nL and nG are lactide and glycolide molar fraction in copolymers respectively )

EntryGlycolide (%)

in polymer [nL/(nL+nG)]LL LG

LG/(LG+LL)

(%)

a 31 7.7 3.4 30.6

b 23 10.1 3.2 24.1

13C{1H} NMR sequence analysis of PLLGA copolymers

A random copolymer would have an average glycolyl sequence length, LG equal to 2.

Mass (m/z) = Mend group + mMla + nMga + MK+ (where Mend group = 18 or 0, Mla = 72, Mga = 58, MK+ = 39)

MALDI-ToF MS spectra of PLLGA with lipase PS at 100 0C.

1773.0 1785.2 1797.4 1809.6 1821.8 1834.0

Mass (m/z)

0

132.0

0

10

20

30

40

50

60

70

80

90

100

% In

tens

ity

Voyager Spec #1[BP = 1214.6, 773]

1783.7300

1784.7348

1785.72031825.6414

1828.6338

1827.68261797.6875

1826.67051813.66661786.70881821.65341781.7152 1829.63631814.65761798.6515

1823.63691809.6728 1815.6427

1787.73051777.9642 1789.9164

1500 1933 2366 2799 3232 3665

Mass (m/z)

0

174.3

0

10

20

30

40

50

60

70

80

90

100

% I

nte

ns

ity

Voyager Spec #1[BP = 1214.6, 773]

Mass(m/z)

Series A Series B Series C

m nm

n m n

1783 - - 17 8 21 4

1785 24 0 13 13 17 9

1797 0 30 18 7 22 3

1799 - - 14 12 18 8

1811 1 29 19 6 23 2

1813 - - 15 11 19 7

1821 10 18 - - 3 27

1825 2 28 20 5 24 1

1827 - - 16 10 20 6

Main ion series determined by MALDI-ToF spectrum of PLLGA using lipase

HO

O

O

O

OH, K+m n O

O

O

O

m nK+

KO

O

O

O

OH, K+m n

Series A Series B Series C

PLGA prepared by lipase at 130 0C for 7 d

Entry Samples

Feedratio(L/G)

Polymer ratio (L/G)

EnzymeL

Conv.(%)

GConv.(%)

Mw(kDa)

PDITg

(0C)

ΔTg

(0C)

1a PLLGA 90/10 90/10 PS 98 100 19.8 2.3 46.9 4.0

2 PLLGA 80/20 79/21 PS 96 100 20.2 2.7 45.6 3.5

3 PLLGA 70/30 69/31 PS 97 100 18.7 4.6 36.2 6.2

4 PLLGA 90/10 89/11 PS-DI 99 100 11.9 1.5 43.3 4.9

5 PLLGA 80/20 79/21 PS-DI 97 100 11.2 1.6 45.6 3.5

6 PLLGA 70/30 69/31 PS-DI 97 100 10.2 1.6 42.7 4.0

7 PDLLGA 80/20 79/21 PS 97 100 11.5 3.1 43.7 3.8

8 PDLLGA 80/20 79/21 PS-DI 97 100 11.6 1.7 39.2 4.8

9b PLLGA 80/20 72/28 - 74 100 7.7 1.3 42.9 4.4

0 2 4 6 80

5000

10000

15000

20000

Day

Mw

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Mw /M

n

PLLGA L/G=80/20 using

8 wt% lipase PS at 1300C

Mw decreases after the second day. High temperature increases chain depolymerization. Lipase PS may be denatured at this temperature.

0 2 4 60

1000

2000

3000

4000

5000

6000

7000

Day

Mw

0

2

4

6

Mw /M

n

PLLGA L/G=80/20

without catalyst at 1300C

0 2 4 6 80

20

40

60

80

100

Lactide Glycolide Lactide content

Time (d)

Mon

omer

con

vers

ion

(%)

0

20

40

60

80

100

Lactide content (%)

0 2 4 6 8-10

0

10

20

30

40

50

60

70

80

90

100

110

Lactide Glycolide Lactide content

Time (d)

Mon

omer

con

vers

ion

(%)

-10

0

10

20

30

40

50

60

70

Lactide content (%)

PLLGA L/G=80/20 using8 wt% lipase PS at 1300C

PLLGA L/G=80/20 without catalyst at 1300C

High temperature at 1300C increases the polymerization rate.

4.Conclusion

Lipase PS works as catalyst to synthesize of PLGA and the conversion gets to 96%.

Transesterfication has occurred during the reaction.

PLGA copolymers obtained by lipase PS and lipase PS-DI at 100 0C are block copolymers.

A higher temperature increases the polymerization rate but also increases the depolymerization rate.

The PLGA copolymers from lipase might contain both linear and cyclic chains.

Acknowledgement

Prof. J.L. Huang Ir. S. Huijser Dr. R. Sablong Dr. R. Duchateau Prof. C.E. Koning Dr. F.G. Karssenberg Prof. P. J. Lemstra

Everybody who contributed to my project

Thank you for your attention !