Synthesis and Properties of New pH Sensitive Chitosan Fluorescent Nanoparticles
A new naphthalimide kind of carboxyl-containing fluorophore was synthesized,and then the fluorescent polymer naphthalimide-modified carboxymethyl chitosan(CMCS3N) was developed by the way of chemical bonding of the synthesized naphthalimide fluorophore into carboxymethyl chitosan(CMCS),a water-soluble polymer with good biocompatibility.The structures and morphology of CMCS3N have been characterized by the methods of infrared spectroscopy,ultraviolet-visible spectroscopy and transmission electron microscopy.The results showed that the fluorescent polymer has nanostructure with diameters of about 40 nm.The fluorescence microscopy images illustrated CMCS3N could give yellow-green fluorescence under UV-light.The excitation and emission wavelengths of the nanoparticles have been obtained by fluorescent spectroscopy with 409 nm and 534 nm,respectively.The fluorescence of CMCS3N was sensitive to pH in the range from pH 5 to 8 and 1.0×10-5 mol/L of common metal cations had no obvious effect on the fluorescence intensity.The results indicated CMCS3N could be used as pH sensitive fluorescent probes in vivo imaging.