Multiphase Mixed Material Derived From Calcite and Diammonium Hydrogen Phosphate Coated With Tetraethyl Orthosilicate: A Potential Implant Coating Material

A multiphase mixed material (M‐PMM) made from calcite and diammonium hydrogen phosphate was prepared using the wet chemical method. To improve its bioactivity, the M‐PMM was coated with tetraethyl orthosilicate (TEOS) at varying mass percentages of 5% and 10% producing 5%_TEOS‐M‐PMM and 10%_TEOS‐M‐PMM, respectively. In vitro mineralization studies were conducted by immersing the uncoated M‐PMM, 5%_TEOS‐M‐PMM, and 10%_TEOS‐M‐PMM in simulated body fluid (SBF) for days 7, 14, and 21. Characterization of the uncoated and coated M‐PMM was performed using X‐ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersion X‐ray spectroscopy (EDS), X‐ray fluorescence (XRF), and scanning electron microscopy (SEM). The uncoated M‐PMM was confirmed to consist of multiple phases, including calcite, mixed type‐AB carbonate hydroxyapatite, and hydroxyapatite monoclinic2 by XRD and FTIR. EDS also confirmed the presence of silicon at the surface of the coated M‐PMM, whereas XRD showed a decrease in crystallinity and crystallite size. The crystallinity and crystallite size were 81% and 20.88 ± 5.12 nm for uncoated M‐PMM, respectively. The coated M‐PMM had values of 79% and 17.27 ± 9.06 nm and 78% and 19.83 ± 9.91 nm for 5%_TEOS‐M‐PMM and 10%_TEOS‐M‐PMM, respectively. The larger surface area of the coated M‐PMM in the SBF gave a better resorption of calcium and phosphate minerals, which was confirmed by XRF. Apatite‐like bundles in the uncoated M‐PMM and coated M‐PMM after immersion in SBF from day 7 to day 21 were revealed by SEM. However, additional cuboid structures were seen in the coated M‐PMM, which enhanced its cell viability and will aid in better osteointegration with biological tissues.