Pluronic decorated-nanogels with temperature-responsive volume transitions, cytotoxicities, and transfection efficiencies

DNA nanogels were prepared by chemically conjugating Pluronic to the surface of cationic polymer/DNA complex in order to prepare thermo-responsive nanogels with endosomal disrupting abilities. Amine-reactive Pluronic was prepared by activating hydroxyl groups of Pluronic and subsequently reacted with pre-formed PEI/DNA complex. The conjugation process was monitored by measuring liberated nitrophenyl groups during the conjugation reaction. The properties of the nanogels (size and ζ-potential) changed significantly when temperature was increased from 20 to 37 °C. The multimodal size distribution of the nanogel also confirmed the variable sizes and distribution of the nanogel upon changing temperatures. Electron microscopy and atomic force microscopy also confirmed the modulated morphologies and sizes of the thermo-responsive nanogel. Confocal microscopy revealed that the nanogel disrupted lysosomes and endosomes at low temperatures, thus confirming endosomal disrupting abilities. The survival rates results showed that the cytotoxicities of the nanogel increased as the temperature decreased from 37 to 20 °C, showing that collapsed Pluronic chain played a role in modulating cytotoxicities. In vitro transfection efficiencies of the nanogel were also measured in NIH3T3 cells. Transfection efficiencies increased as the temperature decreased to 20 °C, thus confirming that endosomal disruptions played a significant role in increasing transfection efficiencies.