Is there a relationship between solubility and resorbability of different calcium phosphate phases in vitro?

Abstract

Background: Does chemistry govern biology or it is the other way around - that is a broad connotation of the question that this study attempted to answer.

Method: Comparison was made between the solubility and osteoclastic resorbability of four fundamentally different monophasic calcium phosphate (CP) powders with monodisperse particle size distributions: alkaline hydroxyapatite (HAP), acidic monetite (DCP), β-calcium pyrophosphate (CPP), and amorphous CP (ACP). Results With the exception of CPP, the difference in solubility between different CP phases became neither mitigated nor reversed, but augmented in the resorptive osteoclastic milieu. Thus, DCP, a phase with the highest solubility, was also resorbed more intensely than any other CP phase, whereas HAP, a phase with the lowest solubility, was resorbed least. CPP becomes retained inside the cells for the longest period of time, indicating hindered digestion of only this particular type of CP. Osteoclastogenesis was mildly hindered in the presence of HAP, ACP and DCP, but not in the presence of CPP. The most viable CP powder with respect to the mitochondrial succinic dehydrogenase activity was the one present in natural biological bone tissues: HAP.

Conclusion: Chemistry in this case does have a direct effect on biology. Biology neither overrides nor reverses the chemical propensities of inorganics with which it interacts, but rather augments and takes a direct advantage of them.

Significance: These findings set the fundamental basis for designing the chemical makeup of CP and other biosoluble components of tissue engineering constructs for their most optimal resorption and tissue regeneration response.

Keywords: Calcium phosphate; Nanoparticles; RAW264.7; Resorbability; Solubility.