Degradation of poly(lactide-co-glycolide) (PLGA) and poly(L-lactide) (PLLA) by electron beam radiation.

This paper seeks to examine the effects of electron beam (e-beam) radiation on biodegradable polymers (PLGA and PLLA), and to understand their radiation-induced degradation mechanisms. PLGA (80:20) and PLLA polymer films were e-beam irradiated at doses from 2.5 to 50 Mrad and the degradation of these films were studied by measuring the changes in their molecular weights, FTIR spectra, thermal and morphological properties. The dominant effect of e-beam irradiation on both PLGA and PLLA is chain scission. Chain scission occurs first through scission of the polymer main chain, followed by hydrogen abstraction. Chain scission, though responsible for the reduction in the average molecular weight, Tc, Tg and Tm of both polymers, encourages crystallization in PLGA. PLLA also undergoes chain scission upon irradiation but to a lesser degree compared to PLGA. The higher crystallinity of PLLA is the key factor in its greater stability to e-beam radiation compared to PLGA. A linear relationship is also established between the decrease in molecular weight with respect to radiation dose.

[1]  M. Alonso,et al.  Novel Approaches to Controlled-Release Antigen Delivery , 1994, International Journal of Technology Assessment in Health Care.

[2]  Shalaby W. Shalaby,et al.  Radiation effects on polymers , 1991 .

[3]  E. Rabinowitsch,et al.  Some remarks about free radicals and the photochemistry of solutions , 1934 .

[4]  O. Güven,et al.  Radiation induced crystallinity damage in poly(L-lactic acid) , 2002 .

[5]  G. Scott.  Mechanisms of polymer degradation and stabilisation , 1991 .

[6]  S. Sosnowski.  Poly(L-lactide) microspheres with controlled crystallinity , 2001 .

[7]  L. Pruitt,et al.  The effects of gamma radiation sterilization and ageing on the structure and morphology of medical grade ultra high molecular weight polyethylene , 1996 .

[8]  D. Wise,et al.  Poly(lactic/glycolic acid) biodegradable drug-polymer matrix systems. , 1985, Methods in enzymology.

[9]  Mool C. Gupta,et al.  Radiation effects on poly(lactic acid) , 1983 .

[10]  R. Jalil,et al.  Biodegradable poly(lactic acid) and poly(lactide-co-glycolide) microcapsules: problems associated with preparative techniques and release properties. , 1990, Journal of microencapsulation.

[11]  N. Peppas,et al.  Physicochemical foundations and structural design of hydrogels in medicine and biology. , 2000, Annual review of biomedical engineering.

[12]  R. Langer,et al.  Biodegradable polymers as drug delivery systems , 1990 .

[13]  J. Williams.  Stability of Polypropylene to Gamma Irradiation , 1991 .

[14]  H. Mark,et al.  Encyclopedia of polymer science and engineering, Vol. 10, 2nd ed. : Nonwoven fabrics to photopolymerization , 1987 .

[15]  Lawrence L. Lapin.  Probability and Statistics for Modern Engineering , 1983 .

[16]  J. Pionteck,et al.  Characterisation of radiation behaviour of polyethylene/polymethacrylates interpenetrating polymer networks , 2000 .

[17]  T. Lee,et al.  On the determination of polymer crystallinity for a thermoplastic PPS composite by thermal analysis , 1995 .

[18]  Vincent P. Calkins,et al.  Radiation Chemistry of Polymeric Systems , 1963 .

[19]  M. Šen,et al.  Effect of gamma irradiation conditions on the radiation-induced degradation of isobutylene–isoprene rubber , 2003 .

[20]  H. Mark,et al.  Encyclopedia of polymer science and engineering , 1985 .

[21]  R. A. Jain,et al.  The manufacturing techniques of various drug loaded biodegradable poly(lactide-co-glycolide) (PLGA) devices. , 2000, Biomaterials.

[22]  A. Buttafava,et al.  Gamma irradiation effects on stability of poly(lactide-co-glycolide) microspheres containing clonazepam. , 2001, Journal of controlled release : official journal of the Controlled Release Society.