Search

Additive manufacturing (AM) or 3D printing of bone defect models is gaining much attention in the biomedical field as it could significantly facilitate the development of customized implants with a high degree of dimensional accuracy. Due to their satisfactory biocompatibility and minimal stress shielding effect, Ti6Al4V (Ti64) alloys are increasingly preferred in the development of such implants. However, their poor osseointegration abilities and lack of antibacterial properties often cause implant loosening and microbial infections, leading to implant failure. To address these drawbacks, we propose in this work a simple surface modification approach of customized Ti64 alloys (3D printed Ti6Al4V) that enables the formation of porous calcium titanate (CT) over their surface as well as the incorporation of silver nanoparticles (AgNPs) into the thus formed porous network. The successful CT formation with the incorporation of AgNPs throughout the 3D printed Ti64 surface and their influence in changing the morphological and mechanical behaviour were studied by Raman spectroscopy, SEM, AFM, Contact angle measurement, XPS, HR-TEM and nano-indentation. Antibacterial studies using Staphylococcus aureus and Escherichia coli, and in-vitro cell studies using MG-63 cell lines showed that surface modified samples resulting from the proposed method exhibit satisfactory antimicrobial property and are highly biocompatible. The obtained surface modified samples also showed a significant improvement in corrosion resistance as compared to unmodified 3D printed Ti64 alloys. The improvement in corrosion resistance was revealed by electrochemical impedance Spectroscopy (EIS). Obtained results emphasis that thus surface modified 3D printed Ti64 alloys are promising candidates for hard tissue implant applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The rate of global warming and unfavorable climate changes caused by the drastic upsurge of carbon dioxide (CO 2) emission has necessitated the development of approaches to limit the significantly high concentration of CO 2 in the atmosphere. The photoelectrochemical reduction of CO 2 results in a reduction of the energy required to transform this greenhouse gas into valuable end products. In this study, we fabricated cost-effective and novel 3D nanoporous structured (3DNS) TiO 2 nanoparticles (T-NPs) on the surface of a thin titanium foil (T-foil) by chemical treatment with hydrogen peroxide (H 2 O 2) followed by calcination at high temperatures in the range of 400–800 °C. The as-proposed samples were analyzed by several characterizations such as XRD, XPS, TEM, and Raman spectroscopy. At 600 °C, the anatase-dominated mixed phases of calcinated T-foil (TO600) were seen, and a maximum photocurrent density of 71.5 µA/cm2 was obtained, in comparison to the T-foils treated at other temperatures (TO400, TO500, TO700, and TO800). Because of the better photocurrent density, TO600 was selected as the photocathode material for photoelectrochemical CO 2 reduction performed with or without the presence of solar light. The lowest CO 2 reduction onset potential (−1.191 V) was observed on the TO600 sample in the presence of light with Ag/AgCl as the reference electrode. 1H NMR analysis of the product solution revealed the formation of formic acid as the major product of the CO 2 reduction reaction after the chronoamperometric electrolysis was performed for more than 25 h. The maximum faradaic efficiency (64%) and formic acid yield (165 µmol cm−2 h−1) were obtained at an applied potential of − 1.3 V (vs. Ag/AgCl reference electrode) for TO600. [Display omitted] • TiO 2 nanoparticles (T-NPs) formed on the surface of porous Ti foil followed to calcination at 400 to 800 °C were prepared. • T-NPs, phase changes from anatase to rutile when the temperature is raised from 400 °C to 800 °C and the bandgap reduced. • TO600 with mixed phases of anatase and rutile were delivered a maximum photocurrent density (71.5 µA/cm-2). • The lowest potential for photocatalytic CO 2 reduction to formic acid with 64% faradaic efficiency was observed on the TO600. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study is to develop a simple method to observe the surface morphology of non-conductive material in its hydrated condition. Here porous hydroxyapatite (HAp) green body prepared by gelcasting process was considered as a case study, and, the resultant body was subsequently treated with hydrophilic ionic liquid (IL). The surface morphology and the pore structure of the IL-treated porous HAp green body were successfully observed even in hydrated condition without any charging using field emission scanning electron microscope (FE-SEM). Results showed that the pore diameter from 300 to 600μm in as-prepared green body was reduced to 100–300μm in the sample sintered at 1000°C. Raman results showed that the IL forms weak hydrogen bond with water molecules within the sample and, that prevents from drying in vacuum condition. In addition, the IL acts as a conducting media for HAp ceramics to be observed under FE-SEM. [Copyright &y& Elsevier]

Abstract: In this study, a simple and convenient method for observing the surface morphology of hydrated porous ceramic green bodies is proposed. The porous hyrdoxyapatite (HAp) green body was prepared by a gelcasting process and was dried in a humid chamber from 90 to 50% relative humidity at 25°C before subsequent treatment with a hydrophilic ionic liquid (IL). The surface morphology of the IL-treated porous HAp green body was observed using FE-SEM. The results showed that the pore morphology and microstructure of the HAp green body was readily observable without evidence of charging. The as-prepared sample showed pores approximately 300–600μm in diameter, which gradually contracted to approximately 200–400μm upon drying in the humid chamber. Following sintering at 1000°C, the pores had further contracted to approximately 100–300μm. The IL binds with the surrounding water to prevent the sample from drying in vacuum and acts as a conductive media, allowing the HAp ceramics to be observed in the electron microscope. In comparison to the micro-focused X-ray CT analysis, the fine pore structure (less than 100μm) could only be observed using FE-SEM when the porous body had also been subjected to the IL treatment. [Copyright &y& Elsevier]

Abstract: Many studies have shown that certain biomaterials with specific porous structures can induce bone formation in non-osseous sites without the need for osteoinductive biomolecules, however, the mechanisms responsible for this phenomenon (intrinsic osteoinduction of biomaterials) remain unclear. In particular, to our knowledge the type of pore structure suitable for osteoinduction has not been reported in detail. In the present study we investigated the effects of interconnective pore size on osteoinductivity and the bone formation processes during osteoinduction. Selective laser melting was employed to fabricate porous Ti implants (diameter 3.3mm, length 15mm) with a channel structure comprising four longitudinal square channels, representing pores, of different diagonal widths, 500, 600, 900, and 1200μm (termed p500, p600, p900, and p1200, respectively). These were then subjected to chemical and heat treatments to induce bioactivity. Significant osteoinduction was observed in p500 and p600, with the highest observed osteoinduction occurring at 5mm from the end of the implants. A distance of 5mm probably provides a favorable balance between blood circulation and fluid movement. Thus, the simple architecture of the implants allowed effective investigation of the influence of the interconnective pore size on osteoinduction, as well as the relationship between bone quantity and its location for different pore sizes. [Copyright &y& Elsevier]

Abstract: Selective laser melting (SLM) is a useful technique for preparing three-dimensional porous bodies with complicated internal structures directly from titanium (Ti) powders without any intermediate processing steps, with the products being expected to be useful as a bone substitute. In this study the necessary SLM processing conditions to obtain a dense product, such as the laser power, scanning speed, and hatching pattern, were investigated using a Ti powder of less than 45μm particle size. The results show that a fully dense plate thinner than 1.8mm was obtained when the laser power to scanning speed ratio was greater than 0.5 and the hatch spacing was less than the laser diameter, with a 30μm thick powder layer. Porous Ti metals with structures analogous to human cancellous bone were fabricated and the compressive strength measured. The compressive strength was in the range 35–120MPa when the porosity was in the range 75–55%. Porous Ti metals fabricated by SLM were heat-treated at 1300°C for 1h in an argon gas atmosphere to smooth the surface. Such prepared specimens were subjected to NaOH, HCl, and heat treatment to provide bioactivity. Field emission scanning electron micrographs showed that fine networks of titanium oxide were formed over the whole surface of the porous body. These treated porous bodies formed bone-like apatite on their surfaces in a simulated body fluid within 3days. In vivo studies showed that new bone penetrated into the pores and directly bonded to the walls within 12weeks after implantation into the femur of Japanese white rabbits. The percentage bone affinity indices of the chemical- and heat-treated porous bodies were significantly higher than that of untreated implants. [Copyright &y& Elsevier]

Abstract: Porous titanium metal subjected to NaOH and heat treatments is useful as a bone substitute as it shows high mechanical strength as well as osteoconductivity and osteoinductivity. However, the porous metal is liable to be contaminated with oxygen gas during the fabrication process and this incorporated oxygen could lead to adverse effects on the bioactivity and mechanical properties of the prepared porous body. In this study, oxygen contamination during fabrication of bioactive porous bodies was measured. It was found that the oxygen content of the titanium metal was increased from 0.08 to 0.23 mass% when the porous body was prepared from bar stock, and it further increased up to 0.51 mass% when it was subjected to NaOH and heat treatments. Despite this, the porous bodies subjected to NaOH and heat treatments formed apatite on their pore walls within 1 day in a simulated body fluid. This result was consistent with the apatite-forming ability of NaOH- and heat-treated titanium plates with different oxygen contents in the range of 0.05 to 0.30 mass%. The compressive strength of the porous body was increased about 10% by the NaOH and heat treatments. [Copyright &y& Elsevier]

Abstract: Bio-composites consisting of sol–gel processed apatite wollastonite (AW) glass ceramics and poly methyl methacrylate (PMMA) were prepared by hot compaction method. Density of the composites decreased with increase in PMMA content, while, biaxial flexural strength (BFS) was 21 MPa for 20 wt.% PMMA and beyond which it decreased. A correlation between phase compositions of AW glass ceramics with BFS was attempted from the XRD results. In vitro bioactivity of the composites in a simulated body fluid (SBF) showed the formation of spherical globules on the surface within 7 days of soaking as observed by environmental SEM. Thin film XRD and EDX measurement confirmed these globules to be bone like apatite with Ca/P ratio 1.53 and FTIR measurement showed the corresponding peaks for phosphates. Results indicated the bone bonding ability of the composites by forming a surface apatite (calcium phosphate) layer in SBF and the growth increased with increase in soaking durations. ICP measurement of the remaining SBF after 7, 14 and 21 days soaking of samples was found to be in good agreement with the EDX analysis results. [Copyright &y& Elsevier]

Abstract: The present paper describes calcination of calcium phosphate ceramics (hydroxyapatite, HA) at 200, 400, 600, 800 and 1000 °C to observe the phase change using X-ray diffraction. HA phase was found to be stable up to 600 °C and later got dissociated into other non-stoichiometric phases like tricalcium phosphate (Ca3(PO4)2 [TCP]), calcium pyrophosphate (Ca2P2O7 [CPP]) and calcium hydrogen phosphate (CaHPO4 [CHP]). TCP was found to be the major phase above 1000 °C. FTIR spectra showed the presence of various PO4 3− and OH− groups present in the powder. Powders compacted and sintered at 900, 1000, 1100 and 1200 °C showed an increase in density from 2.11 to 2.95 g/cm3 while biaxial flexural strength (BFS) was found to be higher (48.7 MPa) when the samples were sintered at 1100 °C and it decreased with further increase in sintering temperature. [Copyright &y& Elsevier]

[Display omitted] • Ti6Al4V powder was surface modified by NaOH treatment to form uniform nano network. • Sodium ions were replaced by calcium ions in the network by ion exchange method. • Presence of Ca and Ag transformed the network into anatase and calcium titanate. • Surface modified Ti6Al4V showed good antibacterial activity and biocompatibility. • Composite scaffolds were prepared by blending surface modified Ti6Al4V with PMMA. The present work describes a technique to develop silver nanoparticles decorated calcium titanate–titania (AgNPs-CT-TiO 2) nanostructured layer over Ti6Al4V alloy powder by simple chemical and heat treatment approach. The NaOH solution and heat treatment form a uniform porous nano-network morphology of sodium titanate and subsequent calcium nitrate treatment transforms it into calcium titanate along with rutile TiO 2. However, simultaneous treatment with calcium and silver nitrate solution allows the incorporation of both calcium and silver ions over the nano-network morphology leading to the formation of AgNPs decorated calcium titanate along with anatase TiO 2 (AgNPs-CT-TiO 2 @Ti6Al4V) that collectively induces biocompatibility towards MG 63 osteoblast-like cells as well as antimicrobial activity against Staphylococcus aureus. Thus modified AgNPs-CT-TiO 2 @Ti6Al4V alloy powders were subsequently blended with polymethyl methacrylate to develop a composite scaffold using NaCl as a porogen. This composite could be used as a scaffold or bone cement in various bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

Here, effect of solution pH on precipitation of silver decorated hydroxyapatite (Ag-HAp) nano powder during its wet-synthesis was systematically studied. XRD pattern of Ag-HAp nano powder synthesised at pH ranging from 5 to 10 shows that calcium hydrogen phosphate was formed as dominating phase when the solution pH was between 5 and 9 and this phase was gradually transformed into a stable HAp above pH 9. A quantitative analysis of silver amount in Ag-HAp nano powder synthesised at different pH showed that silver can be precipitated to its maximum amount at pH 8 and the further addition of ammonia leads to the formation of a silver-ammonium complex, thereby remaining in the solution. HR-TEM and XPS analysis further confirmed the presence of silver in HAp nanocrystals, synthesised at an optimum pH 9. This trace amount of silver in HAp nano powder showed effective antibacterial activity against Staphylococcus aureus and Escherichia coli. In addition, the cytocompatibility studies carried out on MG63 cells further confirmed the present optimised silver concentration of the Ag-HAp nano powder is well within the toxic limit to be useful in various biomedical applications. [ABSTRACT FROM AUTHOR]

In the present study, the pH dependence hydroxyapatite (HAp) ceramics synthesis, and, their phase stabilities with respect to calcination temperatures were examined. Subsequently, HAp ceramics mixed with different silver amounts (HAp–Ag composites) were prepared in the temperature range 800–1200°C to evaluate the phase stability of HAp in presence of silver. XRD results showed that as-synthesized HAp powder to be partially crystalline and are independent of pH of solution in the range of 9–11. These HAp phases remained stable even upto 1200°C although crystallinity increased in all cases. Additional Ag peaks were appeared in HAp–Ag composites when the mixed powders were heated in the temperature range 800–1200°C. FTIR result further confirmed the presence of Ca2+ and PO4 3− ions. TEM observation showed the precipitation of needle like HAp nanocrystals of 20–40nm in length which agglomerated into particulate morphology above 800°C. Antibacterial study of HAp–Ag composites on Staphylococcus aureus for 1, 3 and 5wt% silver concentration showed that 3wt% silver is sufficient to kill the surrounding bacteria. Further studies on NIH3T3 cells for HAp–Ag composites at 10wt% silver of different concentrations showed good cytocompatibility compared to HAp indicates the prospective applications in therapeutic interventions. [ABSTRACT FROM AUTHOR]

Supercapacitors are continuously gaining popularity in the market because of their powerful ultrafast charging ability, yet their energy is still low while contrasting with batteries. In most cases, utilization of redox additive materials (either by decoration or composite creation) and the redox response in the electrolyte itself are some of the strategies for improving the poor energy density of supercapacitors. Herein, we present, a facile, fast and economical one-pot microwave-assisted synthesis, characterization and supercapacitor application of nitrogen and sulfur co-doped graphene (NSG). The characterization result shows good exfoliation and a superior amount of heteroatoms content (14.9% of Nitrogen and 4.3% of Sulfur) in the graphene. The 1:1.5NSG shows a maximum specific capacitance of 310 F/g in two electrodes symmetric configuration using 1 M H 2 SO 4 electrolyte. In addition, the device fabrication shows a high specific capacitance of 226 F/g and 150 F/g in non-aqueous organic and ionic liquid electrolytes with an energy density of 31 Wh/kg and 32 Wh/kg, respectively. In redox additive 0.015 M HQ in H 2 SO 4 electrolyte, the supercapacitor device exhibits enhanced specific capacitance (667 F/g) with maximum energy density of 59 Wh/kg, which is very high and comparable to lithium-ion batteries. Image 1 [ABSTRACT FROM AUTHOR]