Comparison of the Effect of the Amino Acids on Spontaneous Formation and Transformation of Calcium Phosphates

Ina Erceg,Maja Dutour Sikirić,Marija Ćurlin,Borna Radatović,Darija Domazet Jurašin,Vida Strasser,Nives Matijaković Mlinarić,Damir Kralj,Daniel Mark Lyons,Nadica Maltar-Strmečki

doi:10.3390/cryst11070792

Ina Erceg, Maja Dutour Sikirić + Show 8 more

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https://doi.org/10.3390/cryst11070792

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Journal: Crystals	Publication Date: Jul 7, 2021
Citations: 15	License type: CC BY 4.0

Affiliation: Rudjer Boskovic Institute, University of Zagreb

Abstract

Understanding the effect that specific amino acids (AA) exert on calcium phosphate (CaPs) formation is proposed as a way of providing deeper insight into CaPs’ biomineralization and enabling the design of tailored-made additives for the synthesis of functional materials. Despite a number of investigations, the role of specific AA is still unclear, mostly because markedly different experimental conditions have been employed in different studies. The aim of this paper was to compare the influence of different classes of amino acids, charged (aspartic acid, Asp and lysine, Lys), polar (asparagine, Asn and serine, Ser) and non-polar (phenylalanine, Phe) on CaPs formation and transformation in conditions similar to physiological conditions. The precipitation process was followed potentiometrically, while Fourier transform infrared spectroscopy, powder X-ray diffraction, electron paramagnetic spectroscopy (EPR), scanning and transmission electron microscopy were used for the characterization of precipitates. Except for Phe, all investigated AAs inhibited amorphous calcium phosphate (ACP) transformation, with Ser being the most efficient inhibitor. In all systems, ACP transformed in calcium-deficient hydroxyapatite (CaDHA). However, the size of crystalline domains was affected, as well as CaDHA morphology. In EPR spectra, the contribution of different radical species with different proportions in diverse surroundings, depending on the type of AA present, was observed. The obtained results are of interest for the preparation of functionalized CaPs’, as well as for the understanding of their formation in vivo.

Highlights

The biomimetic approach in the development and synthesis of novel materials, especially hard tissue regeneration biomaterials, is constantly gaining in importance due to the superior properties of natural biomaterials, which have not been achieved by any engineered material to date [1,2,3,4]
The precipitation process was followed potentiometrically, while Fourier transform infrared spectroscopy, powder X-ray diffraction, electron paramagnetic spectroscopy (EPR), scanning and transmission electron microscopy were used for the characterization of precipitates
The first step is the formation of amorphous calcium phosphate (CaxHy(PO4)z·n H2O (3 < n < 4.5), ACP)

Summary

Introduction

The biomimetic approach in the development and synthesis of novel materials, especially hard tissue regeneration biomaterials, is constantly gaining in importance due to the superior properties of natural biomaterials, which have not been achieved by any engineered material to date [1,2,3,4]. It enables a more environmentally friendly approach to advanced material production [5]. The similarity with the bone mineral makes other CaPs interesting for potential application as bone regeneration materials [14], e.g., octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4·5H2O), calcium hydrogen phosphate dihydrate (DCPD, CaHPO4·2H2O) and β – tricalcium phosphate (β-TCP, Ca3(PO4)2) [15]

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