Regulation of biodegradability and drug release behavior of aliphatic polyesters by blending

Abstract

Polyester blending of poly(epsilon-caprolactone) (PCL) with poly(D, L-lactide) (PLA) and their random copolymers (R(CL/LA)) was found to be a convenient approach to regulate the degradation and drug release behaviors of the polyesters. The blend composition and compatibility both affected its degradation and drug release behavior. A DSC study showed that PCL was compatible with 50:50 poly(CL-CO-D,L-LA) (R(50/50)) but incompatible with 25:75 poly(CL-CO-LA) (R(25/75)) and PLA homopolymer. The hydrolysis experiments indicated that with the same CL/LA segment proportion, compatible blends (PCL/R(50/50)) had higher water content and faster weight loss than incompatible blends (PCL/PLA, PCL/R(25/75)). In the compatible blends the PCL degradation rate was increased while that of R(50/50) was decreased. The controlled release kinetics, diffusion constants, and permeation coefficients of the polymer blends were measured by using northindrone (NTD) as a model. The NTD release rates from the polyester blends increased as the CL unit fraction increased but decreased with increasing the LA unit fraction in the blends. With the same CL/LA unit ratios, the NTD release rate from the compatible blend was slower than that from the incompatible blend. The NTD release from the polyester blend was controlled by the diffusion process in the early stage, but the degradation-caused NTD release was later involved. By tailoring the blend composition to such an extent that the degradation-caused release compensated the decline of the diffusion-caused release, a zero-order NTD release was achieved.

Poly(d,l-lactide-ran-ε-caprolactone)-poly(ethylene glycol)-poly(d,l-lactide-ran-ε-caprolactone) as parenteral drug-delivery systems

“…This is consistent with the higher drug permeability of poly(d,llactide) than poly(e-caprolactone) [23]. The same trend was observed in the blend of aliphatic polyester blending [25]. In this report, as the d,l-lactyl unit fraction in the poly(e-caprolactone)/poly(d,l-lactide-ran-e-caprolactone) blend is increased, the drug release rate becomes faster for over 40 days.…”

Poly(Lactic Acid) Blends

“…The thermally induced phase separation at the critical and off-critical compositions proceeded via spinodal decomposition (resulting in a cocontinuous structure) and nucleation and growth mechanisms (resulting in a dispersed particle-matrix structure), respectively [121,123]. Phase separation or immiscibility of high molecular weight PLA/PCL blends was also reported by other authors [65,114,117,[124][125][126][127].…”

“…Therefore, the use of PCL in biomedical fields is limited to long-term implant applications [81,110]. PCL has also good drug permeability [114]. Blending of PLA with PCL to achieve different performance properties (i.e., thermal, mechanical, permeability, and/or drug release) and biodegradability is useful to toughen PLA and broaden both polymer applications [15,78,[115][116][117][118][119].…”

Preparation of self-solidifying polymeric depots from PLEC-PEG-PLEC triblock copolymers as an injectable drug delivery system

“…Synthesis and characterization PCL is a hydrophobic polymer and has low degradation rate [19,20]. These properties can be improved by introduction of D,L-lactide and poly(ethylene glycol) which provides the new copolymer so-called PLECs or D,L-lactide-random-ε-caprolactone-block-poly(ethylene glycol)-block-D,L-lactide-random-ε-caprolactone.…”