Interplay between surface chemistry and osteogenic behaviour of sulphate substituted nano-hydroxyapatite.

Surface potential and chemical compositions of the bioceramics are the core of therapeutic effect and are key factors to trigger the interfacial interactions with surrounding hard and soft tissues to repair and regeneration. Ionic substitution in hydroxyapatite (Hap) lattice significantly influences the zeta potential from -16.46 ± 0.66 mV to -6.01 ± 0.68 mV as well as an average nano-rod length from ~40 nm to ~26 nm with respect to SO42- ion content. Moreover, the surface chemistry of Hap is mainly inter-related to SO42- substitution rate at PO42- site. Specifically, nano-sized feature with lowered negative surface potential influences the protein adsorption via their weak repulsive or attractive forces. Bovine serum albumin (BSA) and lysozyme (LSZ) adsorption studies confirmed the increased affinity to active binding sites of Hap's surface. Further, SO42- ion substituted Hap (SNHA) showed improved in vitro biomineralization activity and alkaline phosphatase activity. Expression of osteogenic biomarkers such as collagen I, V, osteopontin and osteocalcin were evaluated in Saos-2 and MC3T3-E1 cells. Gene expression of these markers was influenced by SO42- ion content in Hap (maximum with 10SNHA). Altogether, these data emphasizes that chemical composition and surface properties are dominant aspect in bioceramic development towards bone regeneration.

A novel nano-hydroxyapatite - PMMA hybrid scaffolds adopted by conjugated thermal induced phase separation (TIPS) and wet-chemical approach: Analysis of its mechanical and biological properties.

In this study, we report the preparation of nano-hydroxyapatite (nHAp) incorporated poly(methyl methacrylate) (PMMA) scaffolds by conjugated thermal induced phase separation (TIPS) and wet-chemical approach, which essentially facilitates the enhancement of both mechanical as well as biological properties of the scaffolds. The dissolution of PMMA was accomplished by acetone (Ace scaffold), ethanol-water (E-W scaffold) and isopropanol-water (I-W scaffold) mixtures as solvents. The existence of nHAp in PMMA matrix was investigated systematically. The higher degree of porous architecture was achieved from Ace scaffolds compared to both I-W and E-W scaffolds. On the other hand, the dense porous architecture of the I-W scaffold exhibited superior hardness and compressive strength than that of the Ace and E-W scaffolds. All the fabricated samples demonstrated enhanced in vitro bioactivity with respect to increasing immersion period as a result of flower-like in vitro apatite layer formation. The MTT assay was carried out for 1day and 3day culture using Saos-2 osteoblast-like cells, which showed better cell proliferation with increasing culture period owing to the interconnected pore architecture of scaffolds and the rational hemocompatibility as per the ASTM standard F756-00.

WITHDRAWN: A novel nano-hydroxyapatite - PMMA hybrid scaffolds adopted by conjugated thermal induced phase separation (TIPS) and wet-chemical approach: Analysis of its mechanical and biological properties.

The Publisher regrets that this article is an accidental duplication of an article that has already been published in Mater. Sci. Eng.: C, 73 (2017) 164­172, 10.1016/http://dx.doi.org/j.msec.2016.12.133. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.