Lipoyl Ester Terminated Star PLGA as a Simple and Smart Material for Controlled Drug Delivery Application.

PLGA, a copolymer of lactide and glycolide, is one of the most used biodegradable polymers that find a wide range of biomedical applications including drug delivery and tissue engineering. However, in spite of remarkable advancement, nanotherapeutics based on PLGA might have drawbacks of inadequate stability, drug leakage, and slow drug release at the tumor site, which reduces its targeting ability and therapeutic efficacy. Here, we report that direct modification of star PLGA ends with lipoic acid, a natural antioxidant present in our human body, affords a smart material (sPLGA-LA) that forms reversibly crosslinked and bioresponsive multifunctional nanoparticles (sPLGA XNPs). Interestingly, sPLGA XNPs obtained in the presence of 23.0 wt % PEG-PDLLA displayed a small hydrodynamic size of 73 ± 1.2 nm, high stability against dilution and 10% serum, while fast destabilization under a reductive environment. Moreover, sPLGA XNPs achieved efficient loading of lipophilic anticancer drug model, doxorubicin (DOX), at a theoretical drug loading content of 13.3 wt %, giving DOX-loaded sPLGA XNPs with reduced drug leakage under physiological conditions as well as significantly accelerated drug release under 10 mM glutathione condition compared with both linear and star PLGA controls (denoted as lPLGA NPs and sPLGA NPs, respectively). Confocal microscopy and flow cytometry displayed obviously stronger DOX fluorescence in B16F10 melanoma cells treated with DOX-loaded sPLGA XNPs than with lPLGA and sPLGA counterparts. MTT assays revealed that DOX-sPLGA XNPs caused 2.4- and 4.2-fold higher antitumor activity toward B16F10 cells than DOX-sPLGA NPs and DOX-lPLGA NPs, respectively. Notably, in vivo pharmacokinetics studies showed prolonged circulation time and significantly improved AUC for DOX-sPLGA XNPs over lPLGA NPs control. Hence, lipoyl ester terminated star PLGA emerges as a simple and smart material for better-controlled anticancer drug delivery.