In the present study, wool fibers were hydrolyzed in the acidic environment The pH value of wool hydrolyzed solution was adjusted based on the principle of isoelectric precipitation. Two kinds of keratin polypeptide precipitates were collected at pH 322 and pH 5.55, respectively. The keratin suspensions were spray-dried and denoted as KP3 and KP5. Both of KP3 and KP5 particles possessed smooth, round and uniform surfaces by scanning electron microscope (SEM). Compared with pristine wool fibers, KP3 and KP5 had higher glass transition temperature (1003 degrees C, 78.2 degrees C) and lower decomposition temperature (1793 degrees C, 187.0 degrees C) examined by thermogravimetry and differential scanning calorimetry (TG/DSC). Fourier transform infrared spectroscopy (FTIR) revealed that the disulphide bond (S-S) of the wool keratin was broken down thoroughly in the process of acidic hydrolysis. X-ray diffraction (XRD) analysis identified an amorphous form of these two kinds keratin polypeptides. The nontoxicity and biocompatibility of KP3 and KP5 were examined by the cell morphology and cell viability test The Alamar Blue assay illustrated that 0.1 mg/ml KP3-PBS medium and 1 mg/ml KP5-PBS medium possessed beneficial impacts on cell viability. All these results demonstrated that both KP3 and KP5 with different amino acids compositions could be tailored from wool hydrolyzed solution based on isoelectric-point precipitation and have potential application future as biomaterials for wound healing, drug delivery, and so on. (C) 2013 Elsevier B.V. All rights reserved.