Quaternized chitosan (QCS)/alginate (AL) nanoparticles (QCS/AL) were successfully prepared in neutral condition for the oral delivery of protein. The physicochemical structure of the QCS/AL nanoparticles was characterized by IR spectroscopy and transmission electron microscopy. The diameter of the nanoparticles with a positive surface charge was about 200 nm. The load of bovine serum albumin (BSA) was affected by the concentration and the molecular parameters, i.e. degree of substitution (DS) and weight-average molecular weight (Mw) of QCS, as well as the concentration of BSA. The release of BSA from nanoparticles was pH-dependent. Quick release occurred in 0.1M phosphate buffer solution (PBS, pH=7.4), while the release was slow in 0.1M HCl (pH=1.2). The DS and Mw of QCS play important roles in the release of BSA in vitro. QCS with high Mw accelerated the release of BSA in acid, while high DS retarded the release of BSA in both 0.1M HCl and 0.1M PBS.
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