Effect of drying and loading methods on the release behavior of ciprofloxacin from starch nanoparticles

Drug loading into and release from starch nanoparticles (StNPs), one kind of novel biological macromolecule, were investigated. Two drying methods (spray and vacuum freeze drying) and drug loading methods (coating and adsorption) were used for evaluation. 40% (w/w) of ciprofloxacin was loaded using coating method while only 7% for adsorption method. Glass transition temperature (Tg) and melting point temperature (Tmp) of ciprofloxacin loaded starch nanoparticles varied from 40°C to 55°C and 125°C to 175°C. Particles using adsorption method had lower loading rate of ciprofloxacin, higher Tg, Tmp and release rate compared to using coating method. Tg and Tmp were not affected by these two drying methods. Release rate of ciprofloxacin was higher from freeze dried particles than from spray dried particles using coating method. For adsorption method, drying methods had not effect on the release rate. A double decay exponential model was able to fit the release data suitably well with coefficient of determination (R(2))>0.97.