Effect of Thermal Processing on the Dynamic/Isothermal Crystallization and Cytocompatibility of Polylactic Acid for Biomedical Applications

Abstract

Polylactic acid (PLA) is a semi-crystalline biopolymer with numerous applications in tissue engineering and regenerative medicine. PLA biodegradable devices are usually manufactured by extrusion or injection molding. The crystalline-amorphous structure that PLA acquires during processing is relevant for its applications as it determines the biodegradation rate as well as the mechanical properties of the final device. This work focuses on the effect of processing and the effect of crystallization conditions over the crystallization kinetics of two PLAs: poly-l-lactic acid (PLLA) and poly-l,d-lactic acid (PLDA). The cytocompatibility of PLLA and PLDA as a function of processing and crystalline degree has also been studied. It is observed that processing affects crystallization kinetics of PLA increasing the crystallization rate of PLLA and PLDA. Finally, crystallinity influenced cytocompatibility of polymeric surfaces, as the viability of human progenitor cells increased on surfaces with higher crystalline fraction.

Review on the Degradation of Poly(lactic acid) during Melt Processing

“…In this work, a decrease in M v of 22% was reported after five reprocessing cycles of PLA. Other researchers [18,38,65,67] found similar results, showing that [η] and M v can be used to measure process-induced degradation of PLA.…”

“…Multiple researchers investigated how the selected melt processing technique affects degradation. In the works of Carrasco et al [43], Cifuentes et al [67], and Pantani et al [92], the degradation due to SSE and IM was compared. Cifuentes et al [67] concluded a decrease in molecular weight of 8% PLDA via IM, whereas a decrease of 6% was observed for PLLA after SSE.…”

“…In the works of Carrasco et al [43], Cifuentes et al [67], and Pantani et al [92], the degradation due to SSE and IM was compared. Cifuentes et al [67] concluded a decrease in molecular weight of 8% PLDA via IM, whereas a decrease of 6% was observed for PLLA after SSE. It should be noted that a clear comparison between IM and SSE was obstructed in this work by the use of two different PLA-grades and processing variables being selected differently.…”

Effect of oligolactic acid stereocomplex microplates as rapid crystallization nucleating agents on the properties of poly(L‐lactic acid)

“…4 Unfortunately, the slow crystallization rate and poor heat resistance of PLLA limit its large-scale application. 5 PLLA is a semi-crystalline polymer, 6,7 and the low crystallinity of PLLA after actual processing led to poor heat resistance. Current research has focused on improving the crystalline properties of PLLA by both adding nucleating agents to it and by post-molding heat treatment.…”