Hydroxyapatite Composite Films Research Articles

Fire-retardant hydroxyapatite/cellulosic triboelectric materials for energy harvesting and sensing at extreme conditions

Fire accidents pose a significant threat to public safety, property, and the environment. Traditional power-dependent rescue and sensing devices are susceptible to failure or even explosion in high-temperature and open-fire environments. This research has developed fire-retardant cellulosic triboelectric materials, offering a potential solution. Due to the protection of hydroxyapatite, the cellulose nanofibril (CNF)/hydroxyapatite composite film did not undergo obvious deformation or carbonization after burning for 60 s under a 500 °C alcohol lamp flame. The closely packed cross-sectional structure facilitated air filling, endowing it with certain heat insulation performance. The high surface roughness and special microstructure greatly enhanced the triboelectric performance, achieving an open circuit voltage of 102 V and a short circuit current of 6.18 μA under a working area of only 4 cm2, surpassing most cellulose-based triboelectric materials. The results in self-powered sensing of high-temperature and open flames indicate that fire-retardant cellulosic triboelectric materials have the potential for use in high-temperature environments. This study introduces a new idea for energy harvesting and sensing at extreme conditions, which has important significance for the development of wearable self-powered sensors and the smooth progress of fire rescue operations. Data availabilityData will be made available on request.

O-carboxymethyl chitosan/gelatin/silver-copper hydroxyapatite composite films with enhanced antibacterial and wound healing properties.

Wound dressing composite films of O-carboxymethyl chitosan (OCMC) and gelatin were prepared and mixed with hydroxyapatite (HA) composited with Silver (Ag) and Copper (Cu) at different concentrations. The chemical, thermal, morphological, and biological properties of the composite films were studied. The analysis by FTIR confirmed the presence of interactions between gelatin and OCMC, and at the same time, the polymer matrix interactions with Ag-Cu/HA complex. The inclusion of nanoparticle to the composite was associated with an improvement of the thermal stability, morphological roughness, a 9-12% more hydrophobic behavior (composite C1, C5, and C8), increase in antibacterial activity from 23.2 to 33.1% for gram negative bacteria and from 37.28 to 40.59% for gram positive bacteria, and with a cell viability greater than 100% for 24 and 72h. The films obtained can serve as a wound healing dressing and regenerating biomaterial.

Synthesis and Characterization of PLA-Micro-structured Hydroxyapatite Composite Films.

This article presents a facile synthesis method used to obtain new composite films based on polylactic acid and micro-structured hydroxyapatite particles. The composite films were synthesized starting from a polymeric solution in chloroform (12 wt.%) in which various concentrations of hydroxyapatite (1, 2, and 4 wt.% related to polymer) were homogenously dispersed using ultrasonication followed by solvent evaporation. The synthesized composite films were morphologically (through SEM and atomic force microscopy (AFM)) and structurally (through FT-IR and Raman spectroscopy) characterized. The thermal behavior of the composite films was also determined. The SEM and AFM analyses showed the presence of micro-structured hydroxyapatite particles in the film’s structure, as well as changes in the surface morphology. There was a significant decrease in the crystallinity of the composite films compared to the pure polymer, this being explained by a decrease in the arrangement of the polymer chains and a concurrent increase in the degree of their clutter. The presence of hydroxyapatite crystals did not have a significant influence on the degradation temperature of the composite film.

MORPHOLOGICAL AND MICROSTRUCTURAL CHARACTERISTICS OF HA COMPOSITE FILMS DEPOSITED BY PULSED LASER

The influence of oxygen atmosphere and substrate temperature on morphology and microstructure of the hydroxyapatite (HA) composite films prepared by pulsed laser deposition (PLD) was studied. According to the results of X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR), it was found that the phase compositions and the crystallinity of HA were affected by the oxygen pressure and substrate temperature. High oxygen pressure can increase the crystallinity of HA, and make random oriented HA gradually transform into [Formula: see text]-axis orientation, and decrease the Ca/P atomic ratio of the film. High substrate temperature can increase the crystallinity of films and the degree of c-axis orientation of HA, but increase the Ca/P atomic ratio slightly. Changes of oxygen pressure or substrate temperature have little influence on the surface morphology and thickness of film. Valuable HA composite film could be obtained at 600[Formula: see text]C under 5[Formula: see text]Pa O2atmosphere.

Improved Corrosion Resistance of NiTi Alloy by Coated with TiO<sub>2</sub>-SiO<sub>2</sub>-HAP Composite Films

In order to further improve the corrosion resistance and bioactivity of NiTi alloy, TiO2-SiO2-HAP (hydroxyapatite) composite films with different composition were prepared on NiTi alloy substrate by a sol-gel method. The phase composition, surface morphology, interface adhesive strength and corrosion resistance were studied. The results indicated that the composite film heat-treated at 500°C showed amorphous state, and with increasing of heat-treatment temperature, crystals of CaSiO3, anatase TiO2 and hydroxyapatite (HAP) appeared. The composite film with higher (TiO2-SiO2) content was more uniform and smooth, and had higher interface adhesive strength with the substrate. With the decreasing of (TiO2-SiO2) content, the composite films tended to become irregular, and tiny crack clusters with ringy distribution appeared when the (Ti+Si)/Ca molar ratio was decreased to 25/75, which led to decrease of interface adhesive strength to some extent. The anodic polarization curves indicated that NiTi alloy coated with TiO2-SiO2-HAP composite films had an apparent improvement of corrosion resistance, with an obvious decrease of passivation current.

パルス電解法を用いたチタニア/水酸アパタイト複合膜の作製

The aim of this study was to examine the formation of titania (TiO2)/hydroxyapatite (HAp) composite films on a titanium substrate using anodic-cathodic pulse electrolysis. The TiO2/HAp composites were coated on commercial pure titanium plates (surface area: 1.0 cm2) using pulse electrolysis in an autoclave in an aqueous solution that consisted of 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2 and pH=5.5 at 120°C. The pulse potentials were applied at +8.7 V vs. Ag/AgCl sat. KCl as anodic potential and -9.3 V as cathodic. The total electrolysis time was 1800 s. We examined the effects of the electrolysis cycle (60~600 s) and duty ratio on such properties of the coatings as the surface morphology, the amount of precipitated HAp, and the size of the HAp crystals. Prior to the pulse electrolysis, cathodic and anodic electrolysis experiments were also conducted. With pulse electrolysis, we could obtain TiO2/ HAp composite films with fine HAp particles dispersed uniformly on a thin TiO2 coating.

Preparation of photo-patterned polymer–hydroxyapatite composites

A polymer–hydroxyapatite (HAp) composite is useful as hard tissue engineering scaffold materials for bone and teeth, particularly. It is necessary to control the form of the composites precisely, because form of bone and teeth is unique and specific. We demonstrated that the shape of a base polymer film was controlled by a photo-pattering technique. Hybridization of the photo-patterned polymer film and HAp was performed by alternative soaking of the film into calcium chloride aqueous solution and phosphate buffer solution. Poly(vinyl alcohol) bearing trans-cinnamate moieties as chromophoric groups (P(VA-VCI)) was spin-coated on various substrates, glass, metals such as titanium, aluminum, stainless steel. The spin-coated film was covered with a patterned photo-mask, exposed by using UV lamp and finally developed by dipping into mixed organic solvent. The patterned P(VA-VCI) film was processed by the alternate soaking process for preparation of P(VA-VCI)–HAp composites. We confirmed that formation of HAp in the P(VA-VCI) film by infrared spectroscopy and X-ray diffraction technique. Microscopic observations of the photo-patterned P(VA-VCI)–HAp composites were also performed. The border line between the polymer–HAp composite film and the substrate is clearly observed even after the alternative soaking process. This method is a method for being very useful for producing the polymer–HAp composite with the form of thought way.

Collagen–hydroxyapatite films: piezoelectric properties

In this paper we report a study of the physicochemical, dielectric and piezoelectric properties of anionic collagen and collagen–hydroxyapatite (HA) composites, considering the development of new biomaterials which have potential applications in support for cellular growth and in systems for bone regeneration. The piezoelectric strain tensor element d 14, the elastic constant s 55, and the dielectric permittivity ε 11 were measured for the anionic collagen and collagen–HA films. The thermal analysis shows that the denaturation endotherm is at 59.47 °C for the collagen sample. The collagen–HA composite film shows two transitions, at 48.9 and 80.65 °C. The X-ray diffraction pattern of the collagen film shows a broad band characteristic of an amorphous material. The main peaks associated to the crystalline HA is present in the sample of collagen–HA. In the collagen–HA composite, one can also notice the presence of other peaks with low intensities which is an indication of the formation of other crystalline phases of apatite. The scanning electron photomicrograph of anionic collagen membranes shows very thin bundles of collagen. The scanning electron photomicrography of collagen–HA film also show deposits of hydroxyapatite on the collagen fibers forming larger bundles and suggesting that a collagenous structure of reconstituted collagen fibers could act as nucleators for the formation of apatite crystal similar to those of bone. The piezoelectric strain tensor element d 14 was measured for the anionic collagen, with a value of 0.062 pC N −1, which is in good agreement compared with values reported in the literature obtained with other techniques. For the collagen–HA composite membranes, a slight decrease of the value of the piezoelectricity (0.041 pC N −1) was observed. The anionic collagen membranes present the highest density, dielectric permittivity and lowest frequency constant f. L.