Surface and adsorption properties of α-tricalcium phosphate

Abstract

The interaction between bone replacement bioceramic materials and the body will take place at the surface of the material. In the present ab initio study, we have investigated surfaces of biologically important alpha-tricalcium phosphate (TCP) and adsorption of biological species including a Ca atom, an H2O molecule, and a SiO2 fragment on the surfaces. The results show that all these species adsorb on the surfaces. The Ca atoms are strongly chemisorbed with newly created Ca-O bonds similar to those in alpha-TCP bulk in bond length; a water molecule is adsorbed and in some cases also dissociated on the surfaces with the dissociative adsorption, the predominant process; a SiO2 fragment initially linear, strongly interacted with two oxygens of different PO4 groups and eventually forms a tetrahedral SiO4-like species which might be a precursor of the silicate present in Si-TCP materials.

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…The structure of a-TCP is well described in literature Liang et al 2010), while the surface and adsorption properties are available in Ref. (Yin and Stott 2006). Similar to b-TCP, a-TCP of a technical grade might be used slow release fertilizer for acidic soils (Budavari et al 1996).…”

Calcium Orthophosphates as Bioceramics: State of the Art

“…From the chemical point of view, the vast majority of calcium orthophosphate bioceramics is based on HA, β-TCP, α-TCP and/or biphasic calcium phosphate (BCP, which is an intimate mixture of either β-TCP + HA [118,119,120,121,122,123,124,125,126,127,128,129,130] or α-TCP + HA [7,8,9,10,11]) [131,132,133,134,135,136,137,138,139]. One should note that recently the concept of BCP has been extended by preparation and characterization of biphasic TCP, consisting of α-TCP and β-TCP phases [140,141,142,143,144].…”

“…As implants made of calcined HA are found in bone defects for many years after implantation, bioceramics made of more soluble calcium orthophosphates [7,8,9,10,11,118,119,120,121,122,123,124,125,126,127,128,129,130,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147] are preferable for biomedical purposes. Furthermore, experimental results showed that BCP had a higher ability to adsorb fibrinogen, insulin or type I collagen than HA [148].…”

Mechanical properties, electronic structure and bonding of α- and β-tricalcium phosphates with surface characterization

“…Yin et al [26] presented density functional studies of bulk TCP showing the density of states (DOS) and energy gap, and of silicon stabilized a-TCP showing bond length changes compared with undoped crystals [27] using the SIESTA code [28,29]. They also calculated the surface adsorption properties of a single Ca atom or H 2 O molecule at specific sites on a-TCP surfaces created from a one-third-sized sub-cell [30]. To the authors' knowledge, the mechanical properties of crystalline TCP based on highly accurate ab initio methods have not been reported.…”