The maleoyl chitosan (MCS) was prepared at room temperature by using sodium carbonate as catalyst. The effect of reactant feed ratio on the degree of substitution and water-solubility of acylated product was studied. FT-IR show that the maleic anhydride is successfully grafted onto chitosan molecule

X-ray diffractometry(XRD) results indicate that maleic anhydride acylating destructed the hydrogen bonds within and between molecules of chitosan

which greatly improved water-solubility. The particle size and zeta potential at different pH values were determined by using Nano-ZS90 Malvern Instruments. The isoelectric point is pH = 3. 01. Three different maleoyl Chitosan nanoparticles in acetic acid

formic acid

lactic acid solution were prepared by self-assembly approach for the first time

which were characterized by scanning electron microscopy(SEM). Dynamic light scattering(DLS) tests show that three kinds of nanoparticles swelled from tens of nanometers to hundreds of nanometers when the pH value increased

which displays the pH-responsive property.