In this work, the preparation of chitosan-poly(acrylic acid)-calcium phosphate hybrid nanoparticles (CS-PAA-CaP NP) based on the mineralization of calcium phosphate (CaP) on the surface of chito-san-poly (acrylic acid) nanoparticles (CS-PAA NPs) was reported. CS-PAA-CaP NPs were achieved by directly adding ammonia to the aqueous solution of CS-PAA nanoparticles or by thermal decomposi-tion of urea in the aqueous solution of CS-PAA nanoparticles, resulting in the mineralization of CaP on the surface of CS-PAA NPs. Through these two routes, especially using urea as a pH-regulator, the precipitation of CS-PAA NPs, a common occurrence in basic environment, was avoided. The size, morphology and ingredient of CS-PAA-CaP hybrid nanoparticles were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), scanning electron microscope (SEM), thermogravimetry analysis (TGA) and X-ray diffractometer (XRD). When urea was used as the pH regulator to facilitate the mineralization during the thermal urea decomposition procedure, regular CS-PAA-CaP hybrid nanoparticles with a porosity-structural CaP shells and 400―600 nm size were obtained. TGA result revealed that the hybrid NPs contained approximately 23% inorganic component, which was consistent with the ratio of starting materials. The XRD spectra of hybrid nanoparticles in-dicated that dicalcium phosphate (DCP: CaHPO4) crystal was a dominant component of mineralization. The porous structure of the CS-PAA-CaP hybrid NPs might be greatly useful in pharmaceutical and other medical applications.
