The bioactivity of poled piezoelectric PLLA membrane was investigated by studying the
calcium phosphate formation in vitro using a biomimetic method. Samples (φ10mm) were poled
under DC electric field of 8~l0kV/cm at 70°C for 30 min followed by cooling under the electric field.
Surface chemistry of the samples before and after poling treatment was studied by X-ray
photoelectron spectroscopy (XPS). Poled/unpoled samples were immersed in supersaturated
calcification solution (SCS) for periods up to 24 h (36.5°C). The surface morphology and composition
of the soaked samples were evaluated by using scanning electron microscope (SEM) and X-ray
diffraction analysis (XRD). Poled samples showed two different charged surfaces, negatively-charged
surface (N-PLLA) and positively-charged surface (P-PLLA). On the N-PLLA surfaces, SEM together
with XRD showed a gradually formed calcium phosphate (Ca-P), while no obvious Ca-P on either
P-PLLA or unpoled samples was observed. This study demonstrated that poled piezoelectric PLLA
substrates induce substantially higher level of Ca-P formation than electrically neutral substrates and
only N-PLLA, however, can improve Ca-P formation after immersion in SCS.
In Vitro Mineralization Property of Borosilicate Bioactive Glass under DC Electric Field
