In situ preparation of gold nanoparticle-loaded lysozyme-dextran nanogels and applications for cell imaging and drug delivery

An effective, green, and facile approach to synthesize gold nanoparticle-loaded protein-polysaccharide nanogels was developed in this study. Biocompatible gold nanoparticle-loaded lysozyme-dextran (Au@Lys-Dex) nanogels were produced using lysozyme-dextran nanogels as reducing and stabilizing agents. Lysozyme-dextran nanogels have a size of about 200 nm and a structure of lysozyme core and dextran shell. At pH around 4, AuCl4- ions are attracted and locally enriched by lysozyme due to the electrostatic and coordination interactions. When the solution is under UV irradiation, the AuCl4- ions are reduced to gold nanoparticles in situ by solvated electrons and reactive radicals produced from aromatic amino acid residues in the lysozyme. The produced gold nanoparticles with a size of about 8 nm are trapped inside the nanogels and the Au@Lys-Dex nanogels are well dispersible by virtue of the dextran shell. Antitumor drug, doxorubicin, can be loaded effectively inside Au@Lys-Dex nanogels via diffusion. In vitro study demonstrates the doxorubicin loaded Au@Lys-Dex nanogels have the same antitumor activity as free doxorubicin. The nanogels can be used as a contrasting agent in optical cell imaging, in which direct visual images of the subcellular distributions of the gold nanoparticles and the released doxorubicin are presented synchronously. The dual functional drug loaded Au@Lys-Dex nanogels are a promising system for simultaneous drug delivery and biomedical imaging.