Microwave synthesis of functionally graded tricalcium phosphate for osteoconduction

Abstract

Porosity is an important parameter of biomaterials used to replace bone. Crystalline tricalcium phosphate (TCP) is a common ceramic used to substitute bone in small quantities and coat medical devices. Using microwave combustion synthesis (MCS) to provide volumetric heating of the reactant materials, along with varied urea to calcium phosphate concentration ratios, a porosity structure is synthesized. The microwave power provided 145W and the reactants are exposed for 5min. Results from in-situ IR thermal analysis show heating in two phases: initially (i.e., first 30s) thermal energy is localized along the surface of the sample followed by (i.e., remaining 5min) volumetric heating and MCS. The product material is confirmed to be tricalcium phosphate via FTIR analysis. Scanning electron microscopy (SEM) images show increased porosity with increased urea concentration. By controlling the concentration gradient in the reactant sample, the product material produced a tailored porosity gradient. Moreover, the MCS tricalcium phosphate is demonstrated to be biocompatible and does not affect cell proliferation by crystal violet tests. This study provides a new perspective on volumetric combustion synthesis by using weak microwave energy to facilitate the formation of a tailored TCP structure.