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Surface modification, encompassing both chemical and physical features, plays a crucial role in fulfilling the requirements of biomaterial applications and also improves their performance. Due to that, this study focuses on the optimization of morphology and functionalization of hydroxyapatite (HAP). For this purpose, hydrothermal growth of HAP on (fluorine tin oxide) FTO is carried out in the presence of calcium and phosphate precursors with Ca/P molar ratio of 1.67:1 in the solution. Trisodium nitrilotriacetic acid (NTA) is used as a chelating additive for the first time during hydrothermal process at temperature between 120 and 180 °C for 16–24 h. Further studies on the effect of NTA concentration on HAP formation indicate that hierarchical structures are formed in the presence of NTA with NTA/Ca molar ratio of 1:1 at temperature between 150 and 180 °C for 24 h, improving crystallinity as temperature increasing. To facilitate the functionalization of HAP, the layer deposited at 180 °C with NTA/Ca molar ratio of 1:1 is peeled using two different reagents, Fluoromount™ and polyvinyl alcohol (PVA). The HAP peeled with PVA shows no relevant morphological changes in SEM images, indicating a successful peeling process using PVA. After that, the HAP powders are functionalized with alendronate (AL) molecules and studied using ATR-FTIR, XPS and BET techniques. Chemical shift of PO 4 3− vibrations and appearance of the new peaks assigned to the –NH 2 group demonstrate successful AL-functionalization. The AL-HAP hierarchical structures fabricated with the aid of NTA can be introduced as multifunctional biomaterials for future bio-applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Micro/nanostructures of hydroxyapatite (HAP) were electrochemically grown in an optimized electrolytic bath containing Ca(NO 3) 2 and NH 4 H 2 PO 4 with Ca/P molar ratio of 1.67. To increase the local pH around the substrate and conductivity of the solution, H 2 O 2 and NaNO 3 were added to the electrolytic solution. Voltammetric analysis of the reagents disclosed the electroactive working potential range. The potentiostatic technique was selected as a suitable deposition method to obtain homogenous coatings of HAP by applying a potential of around -1.05 V in the presence of peroxide. Surface modification and functionalization of the as-deposited HAP coatings were carried out using alendronate (AL) solution in different concentrations via soaking and drop-casting methods. Successful chemical binding of AL molecules onto the HAP surface was demonstrated by the appearance of new peaks assigned to the -CH 2 vibrations and shift of PO 4 3− vibrations in the Fourier transform infrared (FTIR) spectra. The AL-functionalized HAP coatings treated by fluorescein isothiocyanate (FITC) allowed to confirm the homogeneous distribution of AL molecules on the HAP surface. The surface-activated HAP coatings by AL can be introduced as multifunctional materials for future applications in drug delivery, bone regeneration and electrochemical biosensors. [ABSTRACT FROM AUTHOR]

Crystalline hydroxyapatite (HAP) nanoparticles and nanorods have been successfully synthesized via a simple precipitation method. To control the shape and particle size of HAP nanocrystals, coordination ligands derived from 2-hydroxy-1-naphthaldehyde were first prepared, characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance ( 1 H-NMR) spectroscopies, and finally applied in the synthesis process of HAP. On the other hand, the HAP nanocrystals were also characterized by several techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to the FE-SEM and TEM micrographs, it was found that the morphology and crystallinity of the HAP powders depended on the coordination mode of the ligands. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydroxyapatite nanostructures have been prepared by a simple precipitation method. [•] To control shapes of the products, chelating ligands based on Schiff bases were used. [•] The Schiff bases derived from acetylacetone were applied as novel chelating ligands. [•] Different morphologies of hydroxyapatite nanostructures have been formed. [ABSTRACT FROM AUTHOR]

New complexing agents based on Schiff base compounds have been employed to fabricate nanocrystalline hydroxyapatite (HAP). The use of the Schiff bases derived from 2-hydroxybenzophenone led to the formation of HAP nanoparticles and nanorods. Moreover, hollow needle-like nanorods of HAP were formed in the presence of the Schiff base derived from 2-aminophenol. In the crystal growth mechanism proposed for HAP crystals, zero-dimensional (0-D) and one-dimensional (1-D) nanostructures were generated by considering tetradentate and bidentate coordination modes of the Schiff bases, respectively. The synthesized products were characterized by several techniques including proton nuclear magnetic resonance (¹H NMR) spectroscopy, transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). [ABSTRACT FROM AUTHOR]

Abstract: In this work, hydroxyapatite (HAP), Ca10(PO4)6(OH)2, nanostructures including nanorods, nanobundles and nanoparticles have been prepared via a simple precipitation method. In the present method, Ca(NO3)2·4H2O and (NH4)2HPO4 were used as calcium and phosphorus precursors, respectively. Besides, the Schiff bases derived from 2-hydroxyacetophenone and different diamines were used as complexing agents for the in situ formation of Ca2+ complexes. The formation mechanism of 0-D and 1-D nanostructures of HAP was also considered. When the complexing agents could coordinate to the Ca2+ ions through N and O atoms to form the [CaN2O2]2+ complexes, HAP nanoparticles were generated. On the other hand, nanorods and nanobundles of HAP were obtained by forming the [CaN2]2+ as well as [CaO2]2+ complexes in the reaction solution. This work is the first successful synthesis of pure HAP nanostructures in the presence of Schiff bases instead of using the common surfactants. [Copyright &y& Elsevier]

In the expanding field of tissue engineering (TE), improvement of biodegradability and osteoconductivity of biomaterials are required. The use of non-toxic reagents during manufacturing processes is also necessary to decrease toxicity and increase cell viability in vivo. Herein, we present a novel approach to prepare hydroxyapatite (HA) nanorods from sea bio-wastes through a green and eco-friendly wet-chemical processing for bone TE. Highly porous natural polymer-ceramic nanocomposites made of HA, gelatin (Ge) and carboxymethyl cellulose (CMC) hydrogels are then introduced. It was found that cross-linking of the hydrogel matrix by glucose as a green reagent affected all characteristics of the scaffolds including pore size, swelling, biodegradability, and mechanical properties. The homogeneous microstructure with pore sizes in the range of 100–200 μm were attained at 10–20 wt% glucose concentration. With regard to stability and swelling in phosphate buffer saline (PBS), however, more glucose concentrations were desirable. The high biocompatibility and osteoblast activity of the scaffolds were assayed by MTT and calcium content on cell-cultured scaffolds with mesenchymal stem cells (MSCs). The developed CMC/Ge hydrogels modified with bio-derived HA nanorods have a great potential to be used for non-load bearing applications in bone TE. • A novel approach was used to prepare HA nanorods from sea bio-wastes. • Highly porous natural polymer-ceramic nanocomposites were prepared for TE. • Cross-linking of the hydrogel by glucose affected all characteristics of the scaffolds. • Cross-linking with 20% glucose was suitable for attaining homogeneous microstructure with good stability and swelling. [ABSTRACT FROM AUTHOR]