Preparation And Biodistribution Of Low-molecular-weight Chitosan Nanoparticles

The biocompatibility and biodegrability of the drug carriers are very important in parenteral use of drug delivery systems because those properties are critically related to the safety. Several drug delivery systems using macromolecules as drug carriers have been developed for parenteral administration. Chitosan (CS) has been tried out as drug carriers because of their biocompatibiiity and biodegrability. However, it has been found that the biodegrability of chitosan in vivo is very slow and incomplete, which arosed a problem on the possibility of accumulation in the body. Furthermore, recent reports indicated that chitosan had problems on blood compatibility and cell viability, and such drawbacks of chitosan seem to relate with chemical and physical characteristics such as the N-acetylation degree and molecular weight. So low-molecular-weight chitosan (LMWC) has become the focus of investigation.In this study, LMWC was chosen as parenteral delivery system material. LMWCs with different molecular weight determined by viscometry and gel permeation chromatography (GPC) were prepared by enzymatic degraDaltontion and ultrafiltration separation. Through pH-sensitivity experiment, LMWC whichcan dissolve in tumour cell cytoplasm pH environment but can not dissolve in physiological pH environment was selected as carrier material. Chitosan nanoparticles (CS-NPs) were prepared by ionotropic gelation with tripolyphosphate(TPP) anions. Transmission Electron Microscopey (TEM) and Zetasizer instrument were used to estimate the prescription and technique. The compound called FITC-labeled CS (FITC-CS) was prepared by chitosan grafted on fluorescein isothiocyanate (FITC) by chemical bond. The biodistribution of FITC-CS nanoparticles were investigated through determining Fluorescence intensity of each tissue after tail iv injection to mice. The entrapment efficiency of methotrexate(MTX) nanoparticles prepared with LMWC were investigated. The biodistribution of MTX solution and MTX CS-NPs in mice were investigated after the tail iv injection.LMWCs with different molecular weights were obtained through controlled the condition of enzymatic degraDaltontion and separated by ultrafiltration. The molecular weight of LMWCs determined by GPC were 91000, 72000, 41500^ 21000 and 10300Dalton, respectively. After pH sensitivity experiment, LMWC with molecular weight of 21000Dalton was chosen to prepare nanoparticles by ionotropic gelation with TPP anions. A narrow particle size distribution CS-NPs with spheric shape was prepared by controlling the concentration of TPP, the added volume of TPP and concentration of LMWC. As the concentration, added volume of TPP and concentration of LMWC decreased, the particle size of LMWC nanoparticles became smaller, but the zeta potentials value was slightly affected. The average size and zeta potentials value of MTX CS-NPs prepared under the optimal conditions were 223.5 +121.0nm and 45.2+ 1.6mv respectively. The average entrapment efficiency of MTX was 31.46 + 0.86%(n=3 )by treatmentof high speed centrifugation and filtration.The results of biodistribution of FITC-CS nanoparticles showed that nanoparticles were readily cleaned from blood, but can accumulate in liver, kidney, spleen and lung, especially in liver. Compared with MIX solution, the 11/2 of MTX entrapped by CS-NPs was prolonged from 1.06h to 1.89h after iv to mice, and the content of MTX in tissues was increased as well as action time elongated.