Synthesis of chitosan-based polymer carbon dots fluorescent materials and application of self-assembled drug-loading

Fluorescent carbon dots have the advantages of good chemical stability, low toxicity, and surface functionalization, which has caused concern. In recent years, polymer carbon dots synthesize by polymer polysaccharides have become a new research hotspot. In this paper, a chitosan-based fluorescent polymer carbon dot material is synthesized by hydrothermal method and used for drug-loading research. We choose chitosan-graft-polyethylene glycol monomethyl ether and citric acid derivatives as the carbon sources for the carbon dots, because chitosan and polyethylene glycol are both a carbon source for carbon dots and a passivation reagent for carbon dots. Then the quantum yield of the polymeric carbon dots is increased. Polymer carbon dots can also retain the molecular structure of polyethylene glycol and chitosan, providing favorable conditions for its application in drug loading. The structural characterization is performed on P(CS-g-mPEG-CA)CDs by IR, UV, X-ray diffraction, photoelectron spectroscopy, transmission electron microscopy and photoluminescence spectra and pH stability test is carried out. The results show that the synthesized P(CS-g-mPEG-CA)CDs has higher fluorescence quantum yield(66.81%), longer fluorescence lifetime(15.247 ns), and better pH stability. Using Doxorubicin as a model drug, a load study was conducted using this polymer carbon dot. The results show that if the degree of substitution of mPEG is 11.9%, the maximum loading rate of polymer carbon dots is 51.3% and the maximum drug release rate is 28.7%. In addition, we also found that drug loading and release could be controlled by the grafting rate of mPEG. In addition, the cytotoxicity of polymer carbon dots on nasopharyngeal carcinoma cells(CNE-2) is evaluated using an MTT assay. The study shows that there is no obvious cytotoxicity of blank P(CS-g-mPEG-CA)CDs, and that the survival rate of CNE-2 cells decreases with the increase of drug-loaded micelles. The results show that the P(CS-g-mPEG-CA)CDs have a certain application prospect in the aspects of fluorescence labeling, drug delivery, fluorescent tracer system and controlled release.