Endosomal release and intracellular delivery of anticancer drugs using pH-sensitive PEGylated nanogels

摘要

A pH-sensitive PEGylated nanogel was prepared by emulsion copolymerization of 2-(N,N-diethylamino)ethyl methacrylate (EAMA) with heterobifunctional poly(ethylene glycol) bearing a 4-vinylbenzyl group at the alpha-end and a carboxylic acid group at the m-end (CH2=CH-Ph-PEG COOH;M_n=8000) in the presence of potassium persulfate and ethylene glycol dimethacrylate (1.0 mol%) as cross-linker.The loading of the anticancer drug doxorubicin (DOX) into the pH-sensitive PEGylated nanogel was carried out by means of a solvent evaporation method,and the amount of DOX loaded into the PEAMA core was found to be 26 wt%.Furthermore,the DOX-loaded,pH-sensitive PEGylated nanogel showed almost no initial burst release of the DOX under physiological pH,whereas significant release of DOX from the pH-sensitive PEGylated nanogel was observed at the endosomal pH.The antitumor activity of the DOX-loaded,pH-sensitive,PEGylated nanogel against the human breast cancer cell line MCF-7 was lower than that of free DOX.On the other hand,the antitumor activity of the DOX-loaded,pH-sensitive,PEGylated nanogel against the human hepatoma cell line HuH-7,which is a natural drug-resistant tumor line,was superior to that of both free DOX and the DOX-loaded,pH-insensitive,PEGylated nanogel.Using fluorescence microscopy,pH-sensitive PEGylated nanogel in HuH-7 cells was found to be initially localized within the endosome and/or lysosome,with subsequent release of DOX from the nanogel in response to the endosomal pH,and ultimately,diffusion via the cytoplasm into the cell nucleus.These findings suggest that the pH-sensitive PEGylated nanogel represents a promising nano-sized carrier for anticancer drug delivery systems in vivo.