plga for drug delivery huang juan huang junlian saskia huijser rob duchateau
TRANSCRIPT
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 !