Abstract:Nanogels are nano-scaled three-dimensional networks, generally with good hydrophilicity and structural stability. Chitosan, as a natural macromolecular polysaccharide, has a great of advantages such as its non-toxicity and good biodegradability which has aroused wide attention. In this research, utilizing chitosan (CS) as the main building block, the free radical graft copolymerization was initiated at the hydroxyl carbon of chitosan and the nano-scaled aggregates were induced by the self-assembly of the hydrophobic poly(methyl acrylate) (PMA) graft chains. By introducing the redox-responsive cross-linker - diallyl disulfide (DADS) to lock the structure, the tumor sensitive chitosan-poly(methyl acrylate) (CS-PMA) nanogels were obtained at high efficiency. We named this strategy as “Graft copolymerization Induced Self-Assembly (GPISA)”. The size, morphology and structure of the nanogels were characterized by transmission electron microscopy (TEM), dynamic laser light scattering (DLS), FT-IR. Study on this facile GPISA method has proved that the sizes of the nanogels can be controlled via adjusting synthetic parameters. Furthermore, the nanogels were modified by near infrared (NIR) fluorescence molecules-Cy5.5-NHS ester and magnetic resonance imaging (MRI) enhancement molecules - Gd-DTPA to synthesize the fluorescent / MRI dual-functional nanogels. Characterization results of MRI and fluorescence imaging demonstrated that the nanogels are with great cell-labelling capability. The cell toxicity study by MTT assay confirmed the low cytotoxicity of the nanogels to lymphatic endothelial cells (LECs) and breast cancer cells (MCF-7). All these results indicated that the bio-functional nanogels had great potential as NIR/MRI probe for the diagnosis and therapy of tumor.