Gan Zhihua

BIOMINERALIZATION ON COPOLYMERIC MICROSPHERES SURFACE WITH DIFFERENT FUNCTIONAL GROUPS AND COMPOSITION: BIOMINERALIZATION ON COPOLYMERIC MICROSPHERES SURFACE WITH DIFFERENT FUNCTIONAL GROUPS AND COMPOSITION

PCL-b-PEG with different composition and functional groups were used to prepare microspheres with different surface properties by means of the double emulsion solvent evaporation method. Then, the biomineralization of microspheres was performed in the 1. 5 simulated body fluid (1. 5SBF). The effects of the hydrophilicity,, roughness and functional groups of microsphere surface on the formation of apatite were studied. It was found that the higher molar ratio of PEG to PCL leads to rougher and more hydrophilic microsphere surface, which results in the formation of more apatite. The functional groups were found to have great influence on the formation and distribution of apatite on the surface of microspheres. Apatite was distributed homogeneously on the surface of PCL20k-b-PEG(1k)-COOH microspheres. Moreover, the amount of apatite on microsphere surface increased with the mineralization time. The biomineralization had an initial period of ca. 4 days for apatite nucleation, followed by normal gradual growth. The results of this work indicate that the surface properties of microspheres such as hydrophilicity,, roughness and functional groups as well as the biomineralizaiton time could be used to control the apatite formation on microsphere surface. These results are expected to be used in the construction of tissue engineering scaffolds.

Functionalized microgels with acid-cleavable hydrophobic pendant moiety for controlled drug release

Thermosensitive microgels with acid cleavable pendant t -butoxycarbonyl (Boc) groups were prepared through precipitation copolymerization of N -isopropylacrylamide (NIPAAm) and N -( N -Boc-ethylenediamine) methacryloylglycylglycylamide (BEMAGG) with pendent Boc group. The physicochemical characteristics and the drug release behavior from the microgels were greatly influenced by the structural changes upon the removal of Boc groups in acid condition. The size, zeta potentials and the cloud point gradually increased with the acid-triggered removal of the pendant Boc groups from the microgels, which resulted in a much faster drug release of doxorubicin hydrochloride from these microgels in acid condition. These results indicated the great potentials of these functional microgels in the drug delivery systems.