Bioactive Surface Modification of Hydroxyapatite

Abstract

The purpose of this study was to establish an acid-etching procedure for altering the Ca/P ratio of the nanostructured surface of hydroxyapatite (HAP) by using surface chemical and morphological analyses (XPS, XRD, SEM, surface roughness, and wettability) and to evaluate the in vitro response of osteoblast-like cells (MC3T3-E1 cells) to the modified surfaces. This study utilized HAP and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid solution for 10 minutes at 25°C, followed by rinsing 3 times with ultrapure water. The 30% phosphoric acid etching process that provided a Ca/P ratio of 1.50, without destruction of the grain boundary of HAP, was selected as a surface-modification procedure. Additionally, HAP treated by the 30% phosphoric acid etching process was stored under dry conditions at 25°C for 12 hours, and the Ca/P ratio approximated to 1.00 accidentally. The initial adhesion, proliferation, and differentiation (alkaline phosphatase (ALP) activity and relative mRNA level for ALP) of MC3T3-E1 cells on the modified surfaces were significantly promoted (P < 0.05 and 0.01). These findings show that the 30% phosphoric acid etching process for the nanostructured HAP surface can alter the Ca/P ratio effectively and may accelerate the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells.

Preparation, characterization, and in vitro osteoblast functions of a nano-hydroxyapatite/polyetheretherketone biocomposite as orthopedic implant material

“…Contact angle depends on many factors, for instance, surface roughness, surface chemistry, and grain size. 27 Because nHA is more hydrophilic as an inorganic material than PEEK, and the nHA/ PEEK composite is rougher than PEEK, the improvement in hydrophilicity seen with the nHA/PEEK composite may stem from changes in the surface roughness and chemistry, 27,28 which may have affected the functions of the osteoblasts in this study.…”

Osteoclast Response to Bioactive Surface Modification of Hydroxyapatite

“…Therefore, we hypothesized that an acid-etching procedure with phosphoric acid could be used to alter the Ca/P ratio of the HAP surface directly in order to achieve a bioactive surface that best mimics the initial phases proposed by Bertazzo et al [7]. In our previous study, we found that the Ca/P ratio of a nanostructured HAP surface could be effectively altered using a 30% phosphoric acid-etching process, which was further found to enhance the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells [10].…”

“…The HAP plates were treated with 30% phosphoric acid [H 3 PO 4 ] (lot no. T1949; Sigma-Aldrich Japan; Tokyo, Japan) solution for 10 minutes at 25˚C, followed by rinsing 3 times with ultrapure water (MilliQ water: >18 MΩcm) to achieve the modified HAP surface, HAP-30% PA [10]. The surface characteristics of HAP-30% PA were then compared to the untreated HAP surface as a control using the methods described below.…”

“…Hydroxyapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] (HAP) shows great potential as a scaffolding material for bone tissue engineering because of its bioactive and osteoconductive properties in vivo [1]. HAP is bioactive but is not as bioresorbable as β-tricalcium phosphate [β-Ca 3 (PO 4 ) 2 ] (β-TCP), and is most thermodynamically stable at a physiological pH (7.4) [2].…”

“…Therefore, the aim of this study was to evaluate the in vitro response of osteoclast-like cells to the bioactive HAP surface modified by the 30% phosphoric acid-etching procedure [10].…”