| Chitosan (CTS) is a naturally occurring polycationic polysaccharide, and has good biocompatibility, biodegradable and non-toxic. Meanwhile, CTS also has various pharmacological activaty, such as decreasing blood glucose and cholesterol, antibacterial activity, antitumor effect, immunologic enhancement and anti-thrombotic effect, which make it as a drug carrier has broad application prospects. Nanoparticle is prepared by chitosan which can prolong the drug action time, control drug delivery rate and reduce or eliminate side effects. So in this paper, the aromatic acid/chitosan nanoparticles are prepared by the polyelectrolyte complexation. And the chareteristics of the nanoparticles are evaluated, and preparation conditions are optimized.The different molecular weight of CTS are prepared by the acetic acid hydrolysis method. Their molecular weight respectively are1200KDa、320KDa、38KDa. The aromatic acid/chitosan nanoparticles (CTS-SA) through the polyelectrolyte complexation prepared by CTS and aromatic acids (like salicylic acid SA). The FTIR spectrum and lH NMR characteristic absorption peaks of CTS-SA suggest that SA is grafted into the CTS moleculars. In FTIR of CTS-SA, benzene ring stretching vibration appears at1593cm’1and1487cm-1;1458cm-1,1487cm-1and860cm-1’757cm-1appears benzene ring C=C absorption and ortho-substituted phenyl=C=H absorption peak. SA carboxyl absorption peaks of SA at1659cm"1and chitosan amino characteristic peak at1654cm"1disappeared, and amide bond characteristic absorption peak1628cm-1appears at CTS-SA spectrum. The1H NMR spectrum suggest, between6:6.85and7.75has4aromatic hydrogen signal which are4hydrogen,This is proof of chitosan-NH substituting by salicylic acyl. a:7.749and7.733is salicylic acid acyl ortho hydrogen; a:7.396,7.381and7.365is on bits of salicylic acid acyl hydrogen; a:6.897and6.851is hydroxyl ortho hydrogen;6:6.882and6.867hydroxy on position hydrogen. In short, SA carboxyl and CTS amino formed ionic bonds which means SA successfully grafted onto CTS. The optimum condition of preparing chitosan nanoparticles is as follows:the molar reactant ration n(SA):n(CTS)=0.75; reaction temperature is55-60℃; reaction time(t)=4h, while CTS molecular weight less than320KDa the CTS-SA’s drug loading is basically the same. Detected by electron microscopy, CTS-SA nanoparticles have an almost spherical and particle size distribution is normal distribution and a relatively narrow range, the mean diameters are237.8nm.CTS-SA nanoparticles in vitro release rate is relatively slow, and this behavior corresponds to Higuchi model, which shows the CTS-SA nanoparticles having a sustained and controlled release. We detected the solubility, viscosity and hygroscopicity of the CTS-SA nanoparticles. The CTS-SA exhibited good solubility than CTS in water, and pH dependence of water solubility of CTS-SA and chitosan are almost the same that these are not soluble at alkali pH. The viscosity of CTS-SA slow increases with the increase of concentration. The viscosity of CTS-SA decreases with increasing temperature. And the viscosity in HAc is larger than in HCI. The hygroscopicity of CTS-SA is good, and better than CTS and increased with the increase of ambient humidity. As for, the introducing-OH increases the hydrogen bonds between water and hydrophilic. |
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