Fabrication of core–shell PLGA/PLA–pNIPAM nanocomposites for improved entrapment and release kinetics of antihypertensive drugs

Abstract Polylactic acid (PLA) and poly(lactic-co-glycolic) acid (PLGA) are two commonly applied biodegradable polymers for the preparation of nanocomposites used in drug-delivery systems. However, these polymers lack desirable attributes such as resistance to aggregation during long-term storage due to lyophilisation. To improve their efficacy, in this work, PLA and PLGA were encapsulated within a shell of poly(N-isopropylacrylamide) (pNIPAM) using a single emulsion technique followed by an aqueous free radical precipitation polymerisation process, yielding core–shell PLA/PLGA–pNIPAM nanocomposites. The nanocomposites were characterised using zeta potential, dynamic light scattering, and transmission electron microscopy analyses and were further applied as a delivery system for ramipril, an antihypertensive drug. The drug-loaded PLGA–pNIPAM core–shell nanoparticles exhibited a higher drug content (91%) and entrapment efficiency (78%) than their PLA counterparts. An in vitro release study of the formulations at pH 7.3 in phosphate-buffered saline indicated that PLGA was more efficient than PLA with a sustained release of 86% of ramipril from the polymer matrix within 24 h. Furthermore, to determine the release kinetics, the data were fitted to Korsmeyer–Peppas and Higuchi models; the release of ramipril from the polymer matrix followed zero-order rate kinetics and an anomalous (non-Fickian) diffusion mechanism.