Amphiphilic chitosan nanosphere: Studies on formation, toxicity, and guest molecule incorporation

Amphiphilic chitosan developed by conjugating hydrophobic plithalimido groups and hydrophilic poly (ethylene glycol) chains gives a well-dispersed colloidal solution in polar solvents and shows a regular nano-sized spherical structure (similar to 200 nm) with negatively charged surface (similar to 31.24 +/- 4.85 mV). An in vivo acute oral toxicity test confirms the non-toxicity of the chitosan nanosphere with LD50 higher than 2000 mg/kg body weight. A success of incorporating amine molecules into the nanosphere declares that the heterogeneous incorporation system is more effective than the homogeneous ones. The study on guest molecule incorporation using alkylamines and carboxylic acid as models suggests requirements that the guest be hydrophobic and positively charged. TGA study clarifies that the weight loss at 250-300 degrees C relating to the amount of guest incorporation via heterogeneous system is as high as 42.3%, whereas those of homogeneous systems are about 16.86-28.27%. The nanosphere size is significantly changed after guest incorporation, that is, from 200 rim, to approximately 500-1000 nm. (C) 2007 Elsevier Ltd. All rights reserved.