Preparation and characterization of acetylsalicylic acid/chitosan nanoparticles and its antithrombotic effects

Chitosan (CS)-acetylsalicylic acid (ASA) nanoparticles, which are well dispersed and stable in aqueous solution, have been prepared by interpolymer complexation of ASA in CS solution. The physicochemical properties of nanoparticles were investigated by using FT-IR, (1)H NMR, scanning electron microscope（SEM）, dynamic light scattering, and UV spectrophotometer. It was found that the carboxyl group of the ASA had firmly integrated on the amino group of CS and the ASA-CS nanoparticles were almost spherical in shape with an average diameter of less than (79.3 ± 24.6) nm in high reproducibility and showed high chemical stability against environmental changes. It was also found that the prepared nanoparticles carried a positive charge and showed the size in the range from 700 to 150 nm. The surface structure and zeta potential of nanoparticles can be controlled by different preparation processes. The factor experiment results indicated that the ASA-CS nanoparticles had satisfactory loading capacity (LC) and encapsulation efficiency (EE), 27.27% and 46.88% (data not shown), respectively. The experiments of in vitro ASA release showed that these nanoparticles provided a sustained and pH-dependent drug release manner, and the release behavior was influenced by the pH value of the medium. Preliminary pharmacology experiment exhibited prolonged circulation and higher bioavailability than that of ASA. All the results indicated that ASA/CS nanoparticles may have promising pharmaceutical application, and further pharmacological research is needed to confirm these beneficial effects.