Novel nanogels with both thermoresponsive and hydrolytically degradable properties

A series of novel nanogels with both thermoresponsive and hydrolytically degradable properties were synthesized by emulsion polymerization of N-isopropylacrylamide (NIPAAm) and dextran-lactate-2-hydroxyethyl methacrylate (DEXlactateHEMA), a hydrolytically degradable and cross-linkable dextran derivative, without using low molar mass surfactants. Various lengths of degradable oligolactate units and different precursor feeding ratios between NIPAAm and DEXlactateHEMA were used to synthesize the nanogels. FTIR measurements confirmed the chemical compositions and hydrolytic degradation of the synthesized nanogels. Dynamic light scattering measurements of the hydrodynamic radii of the nanogels in phosphate buffer saline (PBS, pH 7.4) against temperature and angle revealed that the nanogels were thermoresponsive with a lower critical solution temperature (LCST) of ∼32 °C. The size and morphology changes of the nanogels with degradation were investigated by using transmission electron microscopy, atomic force microscopy, and static light scattering techniques. AFM image analysis and Holtzer plots revealed that the nanogels became more rigid with degradation in water solutions.