Preparation and Characterization of the Fluorescent Chitosan Nanoparticle Probe

The chitosan (CS) nanoparticles were prepared by crosslinking low-molecular weight chitosan with polyanion sodium tripolyphosphate (TPP). The fluorescent chitosan nanoparticles (FCNP) could be obtained by the reaction between the isothiocyanate group of fluorescein isothiocyanate and the primary amine group of the D-glucosamine residue. Results show that the molecular weight of chitosan, as well as, the ratio of CS and TPP has significant effects on the diameter of the nanoparticles. When the molecular weight of chitosan was controlled at around 50000, and the ratio of CS and TPP was at 6:1, the spherical shaped particles with an average diameter of 40 ± 3 nm were obtained, which was detected by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Fluorescent imaging proved that the fluorescein isothiocyanate (FITC) was attached to the chitosan nanoparticles. The maximal excitation and emission wavelength of FCNP was almost the same as the free FITC. In comparison with free FITC, the particle probes are more stable against photobleaching.