Surface potential and osteoblast attraction to calcium phosphate compounds is affected by selected alkaline hydrolysis processing

Abstract

This study examines the link(s) between the suspension behavior of calcium deficient apatites (CDAs) and biphasic calcium phosphate (BCP), as measured by the ζ-potential, with respect to both whole bone and osteoblasts. CDA is fabricated by hydrolyzing an acidic CaP such as dicalcium diphosphate dihydrate (DCPD; CaHPO₄·2H₂O) and has a structure and composition close to bone apatite. Sintering CDA results in the formation of BCP ceramics consisting of mixtures of hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP), with the HA/β-TCP weight ratio proportional to the Ca/P ratio of CDA. The choice of the base for the DCPD hydrolysis allows various ionic partial substitution of the formed CDA. Na for Ca partial substitution is of interest because of the resulting improvement in mechanical properties of the resulting BCP ceramics and NH₄OH was used as a negative control. The ζ-potential was measured for these materials and the stability of the ceramic to bone interaction calculated. ζ-potential values decrease for CDA(NH₄OH) versus CDA(NaOH) and increase for BCP(NH₄OH) versus BCP(NaOH). While results of these analyses indicate that NH₄OH and NaOH processed CDA and BCP will likely yield osteoblast attachment in vivo, differences in the ζ-potentials may explain varying degrees of cell attachment.