Impact of Side Chain Polarity on Non-Stoichiometric Nano-Hydroxyapatite Surface Functionalization with Amino Acids

Abstract

In this study the affinity of three amino acids for the surface of non-stoichiometric hydroxyapatite nanoparticles (ns-nHA) was investigated under different reaction conditions. The amino acids investigated were chosen based on their differences in side chain polarity and potential impact on this surface affinity. While calcium pre-saturation of the calcium-deficient ns-nHA was not found to improve attachment of any of the amino acids studied, the polarity and fraction of ionized functional side groups was found to have a significant impact on this attachment. Overall, amino acid attachment to ns-nHA was not solely reliant on carboxyl groups. In fact, it seems that amine groups also notably interacted with the negative ns-nHA surface and increased the degree of surface binding achieved. As a result, glycine and lysine had greater attachment to ns-nHA than aspartic acid under the reaction conditions studied. Lastly, our results suggest that a layer of each amino acid forms at the surface of ns-nHA, with aspartic acid attachment the most stable and its surface coverage the least of the three amino acids studied.

Multidimensional Population Balance Modeling for Pathological Calcium Pyrophosphate Dihydrate Crystals in the Presence of Amino Acids

“…It is concluded that the amino acids predominantly bind to negatively charged P regions in consequence of the strong hydrogen bonds. However, it has been suggested that C sites can significantly increase or decrease the amino acid adsorption through electrostatic interactions [23][24][25][26]. In addition, it has been asserted that the side chains of the amino acids are highly effective in these binding preferences, hence the inhibition of the crystal growth [27][28][29][30][31].…”

An Alternative Approach to the Surface Methacrylation of Non-stoichiometric Hydroxyapatite Nanoparticles for Use in Bone-Inspired Composites

“…All other reagents were purchased from Sigma-Aldrich Canada. We have previously reported on the characteristics of this nHA (Comeau and Willett, 2018). The nHA powder has been found to have a crystallinity of 66%, a Ca/P of 1.52 and is rod shaped with a ∼120 nm length and 20-30 nm width on average (Comeau and Willett, 2018).…”

“…The nHA powder has been found to have a crystallinity of 66%, a Ca/P of 1.52 and is rod shaped with a ∼120 nm length and 20-30 nm width on average (Comeau and Willett, 2018). In addition, ATR-FTIR spectroscopy of the raw native nHA has confirmed its carbonated nature (Comeau and Willett, 2018).…”

<p>Electrospun Poly (Aspartic Acid)-Modified Zein Nanofibers for Promoting Bone Regeneration</p>

“…Chu et al39 revealed that Asp plays an important role in optimizing the efficacy of active sites (carboxylate-rich domains) and significantly decreases the interfacial energy barrier, inducing hydrated phase (HP) formation. However, a recent study by Patricia et al48 revealed that the interactions between ASP and hydroxyapatite are notably mediated by side chains, indicating that both the carboxyl and amine groups contribute significantly to the interaction. Whereas a high content of Asp residues may be effective for collagen binding,47 incorporation of Asp affects the degree of crystallinity of the apatitic phase, and the crystallinity decreases as the Asp content increases.…”

“…Asp is highly expressed in the small integrin-binding ligand, N-linked glycoproteins (SIBLINGs) protein family, and members of this family play important roles in hydroxyapatite mineralization in the body 47. Asp can be used as a crystal growth catalyst to modulate biomineralization effectively,40 and it controls hydroxyapatite mineralization in vivo 48…”