The Interaction Between Hydroxyapatite and Citric Acid

Abstract

Hydroxyapatite (HAp) [Ca10(PO4)6(OH)2] is an inorganic compound which has similar chemical composition as bone and citric acid (CA) [C6H8O7 ] is an weak organic acid. In this work the complex (HAp-CA) formed by their interaction is characterized by X-ray diffraction (XRD) analysis and Zeta potential (ZP) measurement as a function of pH of the complex solution. The results of XRD analysis have revealed a monoclinic pattern of the HAp-CA complex with the most pronounced diffraction line, observed at a 2θ of 32.179°. In ZP measurement experiments, the isoelectric point (IEP) for the complex was found to be 1.6 which is well shifted from that of HAp alone (IEP for HAp = 6.5, measured in several previous studies). Also the measured values of ZP in acid medium was found to be higher than that in alkaline medium due to particle size reduction of HAp with increased concentration of CA. The present study can be potentially applied in cancer therapies and drug deliveries.