(79a) pH-Sensitive Hydrogel Nanoparticles As Probes Of Endosomal Escape Mechanisms For Intracellular Drug Delivery

The cytosolic delivery of membrane-impermeable molecules is of great interest because of its potential as intracellular therapeutics delivery. Current research suffers low delivery efficiency caused mainly by endosomal trap and degradation of drug molecules and noticeable cytotoxicity by synthetic materials. Our study designed a novel delivery chaperon to facilitate the endosomal escaping thus to enhance delivery efficiency. Two-stage surfactant-free emulsion polymerization of 2-diethylamino ethyl metharylate (DEAEMA) (core) and 2-amino ethyl methacrylate (AEMA) (shell) with the presence of crosslinker formed monodisperse core-shell hydrogel nanoparticles of 200 nm in diameter. The protonation of tertiary amine groups on polyDEAEMA core at endosomal pH resulted in the reversible swelling of nanoparticles to 2.8-fold diameter change compare to that at physiological pH. The pH sensitivity of particles thus has potential to disrupt endosomal membrane and facilitate molecules escape to cytosol. This hypothesis was proven by the cytosolic delivery of calcein with ~95% efficiency and ovalbumin with ~30% efficiency to dendritic (DC2.4) cells, which has notoriously low delivery efficiency with most synthetic delivery system. Negligible cytotoxicity was caused by the treatment of core-shell nanoparticles evaluating by cell metabolic rate via MTT assay up to 24 hrs and cell viability via colony forming assay up to three days. The primary amine rich shell, which is physically and compositionally segregated from pH responsive-core and easily to be tuned, was found to facilitate cell and drug binding and to decrease cytotoxicity. Preliminary study showed promising results of siRNA delivery to epithelial cells. Future work has been performed to make the nanoparticles degradable in cytosol.