Theoretical study of the HAP crystal growth inhibition potency of pyrophosphate, etidronate, citrate and phytate. Deciphered the adsorbed conformation of phytate on the HAP (001) surface

The study of hydroxyapatite (HAP) crystal growth inhibitors has become an important field of research since HAP was identified as the main mineral component involved in pathological calcifications of soft tissues. In this work we performed a theoretical study of the deposition and the adsorption of a series of the most important HAP crystal inhibitors, such as pyrophosphate, etidronate, citrate and phytate, by means the Density Functional Theory. We showed that the adsorption energies of the inhibitors increased in the sequence: pyrophosphate < etidronate < citrate ≪ phytate, which correlated with the increase of functional groups of the molecules that interact with the HAP surface, and the total molecular negative charge. The study highlights phytate as the best inhibitor of pathological calcifications of the series, but also opened the door to further structural modifications of citrate that will match the inhibition potency of phytate.