Preparation and evaluation of poly(D, L-lactic acid)/poly(L-lactide-co-ε-caprolactone) blends for tunable sirolimus release

Biodegradable materials are widely used in drug delivery at present. Blending polymers with complementary properties has become a promising strategy to tune drug release. In this study, the effects of poly(D, L-lactic acid) (PDLLA) and poly(L-lactide-co-epsilon-caprolactone) (PLCL) blend films on the in vitro release kinetics of sirolimus were investigated. Herein, a series of PDLLA/PLCL blend films with different ratios were prepared by the ultrasonic spray technology and in vitro release tests of these polymer films were carried out in phosphate buffered saline (PBS). Release profiles showed biphasic release pattern: the initial rapid release (phase I) and stable release (phase II) and more PLCL resulted in earlier and faster sirolimus release, with more cumulative drug release observed. The release rate could be tuned by adjusting the ratio of PLCL to PDLLA in blend films, but they may not be a simple linear proportional relationship. Moreover, in vitro sirolimus release kinetics from these blend films were analyzed using mathematical models. This work can provide a feasible way for tuning drug release in polymer matrices under a blend strategy and improve the design of coating films in drug delivery systems.