Abstract:

Objective To prepare urokinase water soluble chitosan (WSC) nanoparticles, and investigate its activity. Methods Urokinase WSC nanoparticles were prepared by ionic crosslinking method, and the encapsulation efficiency of urokinase nanoparticles was measured. The effects of quality ratio of WSC to tripolyphosphate, concentration of urokinase, time and velocity of magnetic stirring, and time and power of ultrasound on encapsulation efficiency were determined, and the conditions for the highest encapsulation efficiency were obtained. The diameters of urokinase nanoparticles were measured by particle size instrument. Urokinase nanoparticles were purified by centrifugal ultrafiltration, and were injected into New Zealand rabbits (urokinase nanoparticles group). Blood samples were taken from rabbits at different time points, and the activity of urokinase nanoparticles was examined. Rabbits injected with single urokinase were served as control group. Results Under room temperature, when tripolyphosphate solution (0.6 g/L) was dropped into WSC solution (1.0 g/L) containing urokinase (1 mg/10 mL), urokinase nanoparticles with the highest encapsulation efficiency (94.8%) were obtained with the time and velocity of stirring of 60 min and 800 r/min respectively, and the time and power of ultrasound in ice bath of 30 s and 10 W respectively. The serum activity of urokinase gradually decreased with time after reaching the peak in control group, while that maintained at a higher level after reaching the peak in urokinase nanoparticles group. Conclusion Urokinase WSC nanoparticles have been successfully prepared, which possess not only sustained-release function, but also activity of urokinase.

Key words: water soluble chitosan, urokinase nanoparticles, encapsulation efficiency, ionic crosslinking method