Hydrothermally extracted nanohydroxyapatite from bovine bone as bioceramic and biofiller in bionanocomposite

Bones have an extraordinary capacity to restore and regenerate in case of minor injury. However, major injuries need orthopedic surgeries that required bone implant biomaterials. In this study, n-HAP powder was extracted from bovine bone by hydrothermal and calcined at different calcination temperatures (600-1100°C) without the use of solvents. The n-HAP powders produced were used to fabricate two types of biomaterials (HAP bioceramics and PLA/n-HAP bionanocomposite). The raw-HAP and calcined n-HAP powder samples were compacted into green bodies and were sintered at various temperatures (1000-1400°C) to produce HAP bioceramics. The best calcined n-HAP was mixed with PLA by melt mixing and injection moulding to fabricate PLA/n-HAP bionanocomposite. Characterizations of the n-HAP powder, n-HAP bioceramics and PLA/n-HAP bionanocomposite samples were done by Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transforms infrared (FTIR), Field emission scanning electron microscopy (FESEM), Energy-dispersive x-ray spectroscopy (EDX), X-ray fluorescence (XRF) spectroscopy, universal testing machine (UTM) and melt flow index (MFI) analyses. TGA data revealed that n-HAP was thermally stable at 1300ºC. The extracted n-HAP powder was highly crystalline and crystallite size was in the range of 10-83 nm as confirmed by XRD. Density and hardness of the n-HAP bioceramics increased as sintering temperature increased and showing maximum values at a temperature of 1400°C. The results of PLA/n-HAP bionanocomposite revealed that the higher n-HAP loaded (at 5wt%), the lower the tensile strength of bionanocomposite due to poor interfacial adhesion. The interfacial adhesion was improved by loading of 1.0 wt% maleic anhydride (MAH) as a compatibilizer. The biocompatibility of bionanocomposite was evaluated in simulated body fluids (SBF). The results showed that apatite layers were grown on the surfaces of both biomaterials. Therefore, both biomaterials formulated shall be promising medical biomaterials for orthopedic applications

Feasibility of waste-derived hydroxyapatite mixed with ultra high molecular weight polyethylene composites for fused deposition modeling process

In this study, feasibility of waste-derived hydroxyapatite (HAp) reinforced UHMWPE composites for Fused Deposition Modeling (FDM) process was investigated. Compared to the commercial HAp, derived from natural resources such as corals, fish bone and eggshells have been converted into HAp and show the similarity with the commercial HAp. Ca/P ratio was so important to human body because Ca influence growth of human bones and P play a role in immune system activation. This research has used waste eggshell has been used to synthesize HAp by using hydrothermal synthesis. The Ca/P ratio was investigated by using SEM/EDS and XRD test. By using these test, it revealed Ca/P ratio of waste-derived HAp has shown 1.69 approximately with the standard Ca/P ratio (1.67). HAp/UHMWPE composites formulation samples were prepared by mixed between HAp and UHMWPE using Brabender Mixer. HAp/UHMWPE composite formulation samples were characterized by their weight percentage. The feasibility of each HAp/UHMWPE composite samples has been studied by their morphology, thermal and rheology properties by using SEM/EDS, TGA/DSC and Rheology test. Formulation sample U50H50 with 50 wt.% of HAp has shown the homogenous mixture, 1.69 Ca/P ratio, lowest melting point and good pseudo-plastic behavior compared to other formulation samples. Therefore, this formulation samples has been used in single screw extruder to fabricate diameter size of 1.75+0.05 mm filament wire for FDM process. DOE has been developed by using Taguchi method with the parameter controlled were die temperature and screw frequency. The optimum parameter setting to produce the diameter of 1.75+0.05 mm filament wire was successfully found at screw frequency of 2.5 Hz and die temperature of 190 ºC. The characteristic of the FDM process shows the samples with optimum dimensional accuracy and relative density was found at 245 ºC of temperature nozzle and 130 ºC of temperature platform. This result shown Hap/UHMWPE composite has potential to become material filament wire feedstock for FDM process

Extraction of biological apatite from cow bone at different calcination temperatures: a comparative study

The purpose of this study is to extract natural hydroxyapatite (HAP) from cow bone. The hydrothermal method followed by calcination treatment at different temperatures is used in this current research. Cow bone has the potential for producing hydroxyapatite, a chief component present in bone and teeth of vertebrates. HAP is an excellent material used in bone restoration and tissue regeneration. Characterizations of the cow bone natural HAP powder were done by X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). TGA data revealed that biological apatite is thermally stable at 1100ºC. XRD data showed that the extracted HAP is, highly crystalline and hexagonal crystal structure having a crystallite size in the range of 10-83 nm. The extracted HAP material is found to be thermally stable up to 1300ºC

Effective one-body dynamics in multiple-quantum NMR experiments

A suitable NMR experiment in a one-dimensional dipolar coupled spin system allows one to reduce the natural many-body dynamics into effective one-body dynamics. We verify this in a polycrystalline sample of hydroxyapatite (HAp) by monitoring the excitation of NMR many-body superposition states: the multiple-quantum coherences. The observed effective one-dimensionality of HAp relies on the quasi 1d structure of the dipolar coupled network that, as we show here, is dynamically enhanced by the quantum Zeno effect. Decoherence is also probed through a Loschmidt echo experiment, where the time reversal is implemented on the double-quantum Hamiltonian, I_{i,+}I_{j,+} + I_{i,-}I_{j,-}. We contrast the decoherence of adamantane, a standard 3d system, with that of HAp. While the first shows an abrupt Fermi-type decay, HAp presents a smooth exponential law.Comment: 8 pages, 6 figure

Facile Synthesis, Characterization, and Antimicrobial Activity of Cellulose-Chitosan-Hydroxyapatite Composite Material: A Potential Material for Bone Tissue Engineering

Hydroxyapatite (HAp) is often used as a bone-implant material because it is biocompatible and osteoconductive. However, HAp possesses poor rheological properties and it is inactive against disease-causing microbes. To improve these properties, we developed a green method to synthesize multifunctional composites containing: (1) cellulose (CEL) to impart mechanical strength; (2) chitosan (CS) to induce antibacterial activity thereby maintaining a microbe-free wound site; and (3) HAp. In this method, CS and CEL were co-dissolved in an ionic liquid (IL) and then regenerated from water. HAp was subsequently formed in situ by alternately soaking [CEL+CS] composites in aqueous solutions of CaCl2 and Na2HPO4. At least 88% of IL used was recovered for reuse by distilling the aqueous washings of [CEL+CS]. The composites were characterized using FTIR, XRD, and SEM. These composites retained the desirable properties of their constituents. For example, the tensile strength of the composites was enhanced 1.9 times by increasing CEL loading from 20% to 80%. Incorporating CS in the composites resulted in composites which inhibited the growth of both Gram positive (MRSA, S. aureus and VRE) and Gram negative (E. coli and P. aeruginosa) bacteria. These findings highlight the potential use of [CEL+CS+HAp] composites as scaffolds in bone tissue engineering

Wireless Information and Power Transfer in Full-Duplex Systems with Massive Antenna Arrays

We consider a multiuser wireless system with a full-duplex hybrid access point (HAP) that transmits to a set of users in the downlink channel, while receiving data from a set of energy-constrained sensors in the uplink channel. We assume that the HAP is equipped with a massive antenna array, while all users and sensor nodes have a single antenna. We adopt a time-switching protocol where in the first phase, sensors are powered through wireless energy transfer from HAP and HAP estimates the downlink channel of the users. In the second phase, sensors use the harvested energy to transmit to the HAP. The downlink-uplink sum-rate region is obtained by solving downlink sum-rate maximization problem under a constraint on uplink sum-rate. Moreover, assuming perfect and imperfect channel state information, we derive expressions for the achievable uplink and downlink rates in the large-antenna limit and approximate results that hold for any finite number of antennas. Based on these analytical results, we obtain the power-scaling law and analyze the effect of the number of antennas on the cancellation of intra-user interference and the self-interference.Comment: Accepted for the IEEE International Conference on Communications (ICC 2017