Hydroxyapatite surface charge investigated by scanning probe microscopy

It is well known that electrical properties such as local electrostatic charge distribution at biomaterial surface plays a significant role in biological interactions. The methods currently employed in measuring surface charge in biomaterials such as zeta potential or potentiostatic titration, however, can only measure global charge distribution in macroscopic and colloidal state of biomaterials. By using scanning probe microscopy techniques we investigated the surface charge domains placed on the hydroxyapatite surface. Scattering near field optical microscopy (s-SNOM) was used to image electrostatic charge trapped at pre-existing and irradiation induced defects within these domains, while phase imaging in atomic force microscopy was used to image the carbon contamination. The two techniques can be used for nanoscale imaging.