Synthesis and characterization of PEGylated carboxymethylchitosan nanoparticles

Two types of novel biodegradable nanoparticles, mPEG (monomethoxypoly(ethylene glycol)) grafted with carboxymethylchitosan (mPEG-g-CMCTS) and PEG cross-linked with carboxymethylchitosan (PEG-CMCTS), were prepared. Both carboxymethylchitosan derivatives were synthesized by grafting or cross-linking reaction of carboxymethylchitosan with mPEG-aldehyde or PEG-bisaldehydes to form Schiff base. The structure of the products was determined by FTIR and NMR measurement. These two copolymers could self-assemble into nanoparticles in aqueous solution. Particle size of mPEG-g-CMCTS measured by TEM varied in the range of 300 nm to 1.1 μm depending on the graft volume of mPEG−2000. The average size of PEG-CMCTS measured by DLS was in the range of 122–500 nm depending on the molecular weight of PEG. A typical TEM micrograph indicated that nearly spherical nanoparticles can be obtained, the diameter depending on the length and flexibility of the cross-linking and grafting agent. Micelles can remain stable in aqueous solution for more than a month.