Investigation of adsorptive orientation state change of anionic porphyrin with the hydrolysis reaction of α-tricalcium phosphate

Abstract

We herein investigated the interfacial interactions between α,β,γ,δ-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and the hydroxyapatite (HA) crystallite converted via hydrolysis reaction from α-tricalcium phosphate. Photoabsorption spectroscopy of the TCPP adsorbed on the HA surfaces revealed that TCPP was favorably vertically arranged on the HA nuclei surface, and then its orientation was changed to be horizontal as the hydrolysis reaction progressed. The TCPP molecular orientation was sensitively associated with elution, nucleation, and crystal growth processes of HA and thus was controllable by the hydrolysis reaction time. The present study is the first report for further understanding of the interfacial behavior of the calcium phosphate–porphyrin interactive changes and also proposes a new concept to organize a well-arranged molecular assembly on bioceramic surfaces.