The Preparation And Properties Of Betulinic Acid/CS Drug Loaded Microspheres

Chitosan(CS) is the unique alkaline polysaccharide in nature, because of its perfect biocompatibility and degradability, it is widely used in medicine, soft release and control release. When the CS is used for drug carrier, it can prolong the application time of the medicine, reduce the adverse effect, increase the stability of the medicine and increase the permeability of cell membrane, it is a widely studied pharmaceutical excipient. The betulinic acid is the derivative of betulin, at first, it is extracted from birch bark by physical methods, then, with the development of the study, many other chemical methods were found to synthesis the betulinic acid at a high rate. As a result, the betulin acid has become a widely source. It not only has many pharmacological activities, such as anti-inflammatory, antitumor, anti-malaria and anti-HIV, but also low toxicity and with high safety index, so it is widely studied in the area of antitumor and anti-HIV.Because the microspheres particle size homogeneous degree will directly affect the loading of betulinic acid/CS microspheres, so we have to achieve a relatively uniform levels of the bland microspheres of CS. In this paper, the Span-80and Twen-80were used as emulsifiers, the formaldehyde and glutaraldehyde were used as crosslinker. With the method of orthogonal experiment, the preparation technology of betulinic acid/CS microspheres was optimized. Above all, we prepared the microspheres of CS with uniform particle size, then we prepared the microspheres of betulinic acid and CS. We characterized the microspheres with the use of FT-IR, SEM and the test of the degree of crosslinking, we tested the drug-loading rate and encapsulation efficiency at the same time.We studied the factors which will have an influence on the microspheres, such as the dosage of emulsifier and crosslinker, the dosing ratio of betulinic acid and CS. Then, we determined the optimum technological conditions:the molecular weight of the CS is a million, the dosage of Span-80is1mL, the dosage of glutaraldehyde is4mL and the release time is16h.