Reactive Oxygen Species (ROS)-Degradable Polymeric Nanoplatform for Hypoxia-Targeted Gene Delivery: Unpacking DNA and Reducing Toxicity

Smart polymers as ideal gene carriers have drawn increasing attentions due to the effective DNA release once triggered by intrinsic stimuli, as well as reduced cytotoxicity. Herein, a stimulus-responsive, positively charged and water-soluble polymer (OEI-TKx) was facilely engineered by cross-linking low molecular weight oligoethylenimine (OEI) via thioketal (TK) linkages that would cleave selectively in reactive oxygen species (ROS)-rich environments induced by hypoxia. Agarose gel electrophoresis assay demonstrated that the threshold N/P ratios for complete retardation of negatively charged DNA migration were above 5 for OEI-TKx. The reduction in DNA-condensing capability and the changes in particle size, size distribution and particle morphology all illustrated that OEI-TKx possessed excellent ROS responsiveness. OEI-TKx/DNA polyplexes showed lower toxicity and higher gene transfection efficiency compared with PEI/DNA polyplexes. The optimum formulation, OEI-TKx/DNA polyplexes (N/P = 40), showed a little better performance than PEI/DNA polyplexes in cellular uptake profile. Furthermore, OEI-TKx/DNA polyplexes could escape from endosomes to the cytosol as efficiently as PEI/DNA polyplexes. Confocal images confirmed that OEI-TKx/DNA polyplexes could more effectively release DNA than PEI/DNA polyplexes, mainly owing to the valid cleavage of thioketal linkages induced by characteristic rich-ROS in Hela cells. These results suggested that OEI-TKx could represent an on-demand stimulus-responsive gene delivery platform.