Synthesis Of N,O-carboxylchitosan-doxorubicin Conjugates And Research Of Their Properties

The transfer of tumor cells is not only an important symbol of malignant tumors, but also the main cause of cancer deaths. The long-term clinical and pathological tests show that lymphatic transfer of tumor cells is the most common way to many cancers. Accord-ing to references, malignant tumors occurred with the transfer of 60-62.5%, so research of tumors transfer is an important task.At present, although small molecular chemotherapy drugs has high efficacy, but the vast majority of species exist strong drug side effects. In the short time they have entered the body, blood drug concentrations far exceeding the required treatment volume. At the same time, there are fast metabolic speed, short half-life, easy excretion. Therefore, as time delays, lower concentrations of a drug will affect efficacy. On the other hand, small molecular drugs have poor selectivity to tumor tissue or tumor cells, which is one of the major reasons increasing medicine need, low efficacy and great side effects. For these reasons, drug release system has become a hot topic in recent years, and the area of research in which macromolecules prodrugs have occupied very important position.Chitosan, the deacetylated derivative of chitin, is the second most abundant polysaccharide found on earth next to cellulose. As a natural renewable resource, chitosan has a number of unique properties such as antimicrobial activity, biological compatibility, and biodegradability, which attract scientific and industrial interest in such fields as biotechnology, pharmaceutics, wastewater treatment, cosmetics, agriculture, food science, textiles and drug carriers. Doxorubicin(DOX), a well known anticancer drug, is a member of the anthracycline ring antibiotics, with a broad spectrum of antitumor activity, including a variety of human and animal solid tumor. However, the myelosuppression, acute cardiotoxicity, multidrug resistence and short plasma half-life limited it's extensively usage in clinical. Workers have covalently linked DOX with polymer to prolong the pharmacological activity, minimize unfavourable side effects and toxicity, decrease the required dose, alter the body distribution and ensure adequate drug delivery to target cells or tissues.This paper firstly displays a method to prepare water-insoluble N,O-carboxylchitosan-doxorubicin conjugates.Firstly, the effect of swelling time, NaOH consumption, reaction temperature, reaction time and chloroactic acid consumption to carboxylation for chitosan were examined. The optimum reaction terms were explored to obtain N,O-carboxylchitosan with big molecular mass and high carboxyl content. The results of FT-IR spectra and ¹H NMR spectra show that the carboxyl methylation mainly accrued on the—NH₂ of C₂ site.Secondly, the mixture of formamide and pyridine was used as reaction medium. Doxorubicin was covalently linked with N,O-carboxylchitosan under N,N-dicyclohexylcarbodiimide(DCC) and 4-Dimethylaminopyridine(DMAP). The drug content of water-insoluble conjugate is 3.4% and the structure of it was analyzed by FT-IR.The nanoparticles suspension of the conjugate was prepared with vibration mill and the effect of the quantity of PVP and the time of milling to particles size were learned. Nanoparticles suspension with 162 mean diameters was obtained and the character of the suspension targeting lymph nodes was investgated.The properties of the conjugate were studied in vitro and in vivo.1. The results of in vitro stability indicate that the water-insoluble conjugate can slowly release doxorubicin under the hydrolysis of enzyme in the serum. After 11 h cultivation, the drug was released completely. However, the conjugates can not release doxorubicin in the phosphate buffer solution(pH=7.4).2. The results of character of drug targeting lymph nodes reveal that the conjugate can targeted into lymph nodes through subcutaneous injection. High performance liquid chromatography(HPLC) analysis suggests that the concentration of doxorubicin in the inguinal lymph node is 6 higher than that in the blood after 30 min.