Synthesis of PLA Using Novel Clay Modified Catalyst and its Characterization, Degradation and application in sustained drug release

Balaji Selukar1, Sharad Parwe1, Kavita Mohite1, Swapnali Jadhav1, Santosh Tupe2, B. Garnaik1*1Polymer Sciences Division, National Chemical Laboratory, Pune ‐ 4110082Biochemical Sciences Division, National Chemical Laboratory, Pune ‐ 411008

Introduction

Poly L‐lactic acid (PLLA) has been recently

recognized as a suitable material for resorbable

materials in medical practice, packaging and

consumer goods due to its several preferable

properties, such as mechanical strength,

transparency, safety and biodegradability .

PolymerTemp

(0C)

Mn

(SEC)

Mw

(SEC)

Tm

(0C)

ΔH

(J/g)

Tg

(0C)

To synthesize novel cloisite modified catalystPreparation of high molecular weight PLA by ROPTo study antibacterial behavior and degradation 

PLA

l

Starch

PCL Others

Objectives

Degradation study

Specifically the biodegradability feature

makes it a promising alternative to existing

polymers from the environmental viewpoint.

In order to prepare polymers with tailor‐

made properties a good understanding of the

polymerization mechanism is necessary.

Direct condensation polymerization of L‐

Lactic acid (L‐LA) to PLLA would be a feasible

process, if we can overcome the problems of

PLA‐1 200 46000 75000 167 66 41

PLA‐2 200 38000 63000 162 29 50

PDLA‐3 200 93000 185000 167 34 51

PDLA‐4 200 27000 44000 163 31 45

copolymer

Mechanism0 50 100 150 200

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Mw = 75000 (by GPC)   Mw = 22400 ( by GPC)  

Tm 1670C Tm 1630C

B D h d l d ti

kinetic control, efficient removal of water and

suppression of depolymerization.

Synthesis of high molecular weight PLLA

depends on the purity of monomer, catalyst

concentration and nonionic nature of catalyst

0 50 100 150 200

Fig. DSC Thermogram at 10˚C/min Fig. Surface Morphology 

By DehydropolycondensationBy Ring opening polymerization

Electrospinning

Catalyst Antibacterial Study

Results and Discussion

Conclusions

1) Novel solid cloisite catalyst was prepared and highest molecular weightPLA (75000) and PDLA(185,000) were obtained respectively.

2) Antibacterial study indicated usefulness of PLA nanofiber matrix for sustained or controlled release of drug

3) PLA synthesized  in the study is biodegradable.

1) Stannous Octoate is widely used as a conventional catalyst for ROP of lactones. However stannous octoate allows formation of Octanoic acid and Stannous Oxide during storage. Therefore, Modified solid cloisite catalyst was prepared and characterized using FTIR,1H‐NMR,119 Sn‐NMR etc.The catalyst is hydrophobic in nature and easy to handle for further polymerization. 2) Highest mol. wt. of PDLA (Mw=185,000) was obtained using modified catalyst where as PDLA  (Mw=75,000) obtained in the presence of Stannous Octoate identical conditions.3) Electrospun nano fiber matrices of PLA and Azithromycin conjugated PLA were fabricated.4) Azithromycin conjugated PLA showed complete inhibition (>99%) of S. aureus and E. coli in Luria‐Bertani broth even after 72h.5) GPC and DSC results indicated that the PLA synthesized in the study is partially degraded in compost after 48 days

References

1)Wm. J. Considine J Organomet Chem 5(1966) 263‐2662) E. S. Lipinsky and R. G. Sinclair, Chem Eng. Prog. 1986, 82, 26.3) Otera J. Transesterification Chem. Rev. 1993, 93, 1449.4) J.otera, Accounts of Chemical Research. 2003, 1470.

B. Selukar thanks CSIR for SRF. The authors gratefully acknowledge Dr. M. V. Deshpande, Biochemical Sciences Division, for providing laboratory facilities for antimicrobial studies.