Copper and its alloys have antimicrobial activity effective for various pathogens. Their application to touch surfaces successfully reduced bioburden in hospital intensive care units but failed to completely prevent the transmission of pathogens derived from the hospital room. Discoloration of pure copper with surface oxide growth is another issue to discourage its application to touch surfaces. Common copper alloys have relatively high resistance to discoloration, but their antimicrobial activity is lower than that of pure copper. Therefore, enhancement of the antimicrobial activity of copper alloys is beneficial for their touch surface application. In this study, glutathione was employed for surface treatment of copper and its alloys to enhance their antiviral activity. Treatment with 4 mM glutathione in 99 vol % ethanol-1% H2O markedly enhanced copper and its alloys' antiviral activities against bacteriophage Qβ except MONEL, which has the lowest Cu content (33.4 wt %). Electrochemical impedance measurement under a thin electrolyte film revealed acceleration of copper and its alloys' corrosion by the glutathione treatment. The antiviral activity of tested materials with the glutathione treatment correlated well with their corrosion rate, except MONEL. Potentiodynamic and chronopotentiometry measurements in 6 M KOH + 1 M LiOH demonstrated reduction in the thickness of the surface oxide layer by the glutathione treatment. These facts suggest that the glutathione treatment reduces the surface oxide layer, resulting in acceleration of corrosion with an increase in Cu ion release, which enhances antiviral activity.

The development of biomaterials that actively promote bone regeneration remains a major challenge in regenerative medicine and dentistry. This study investigated the time-dependent osteogenic potential of an organic-inorganic composite bone filler (hydroxyapatite/collagen bone-like nanocomposite, HAp/Col) using a rat calvarial model, assessed by immunohistochemistry and bone histomorphometry.By day 3, vascular endothelial growth factor receptor 2 (VEGFR2)-positive cells were detected on the HAp/Col surface, indicating early vascular invasion. By day 5, vascular infiltration had extended into the scaffold, where double staining with tartrate resistant acid phosphatase (TRAP)/ alkaline phosphatase (ALP) revealed osteoclast-mediated material resorption and osteoblast-mediated bone matrix deposition around vascular cavities. By day 7, bone remodeling within HAp/Col was markedly active, with clusters of osteoblasts producing new bone matrix. Outside the scaffold, osteoblasts adhered to its surface and elongated, enhancing bone formation through the space-forming effect of HAp/Col swelling.Furthermore, collagen triple helix repeat-containing protein 1 (CTHRC1) expression increased progressively from days 3 to 7, as confirmed by immunostaining and qRT-PCR, suggesting its role as a coupling factor between osteoclast activity and osteoblast differentiation.These findings suggest that HAp/Col is associated with cellular activities related to bone remodeling, including vascular invasion and osteoclast/osteoblast recruitment. HAp/Col demonstrates biocompatibility and in vivo tissue compatibility as a candidate biomaterial for medical and dental applications.

A hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) loaded with silver nanoparticles (AgNPs) was prepared by immersion of HAp/Col powder in the AgNPs solution. The adsorption-desorption properties on the preparation process were investigated, followed by the evaluation of antibacterial activities and cytotoxicity. Adsorption of AgNPs on HAp/Col powder was almost finished at 240 min after mixing. Adsorption isotherm revealed that maximum adsorption amount was 1621.9 mg/g with the best fitted model, Dubinin-Radushkevich adsorption model. The AgNPs-loaded HAp/Col membrane prepared by immersion into 1.6 µg/mL and 6.3 µg/mL AgNPs colloidal solution demonstrated no survival of Escherichia coli and Staphylococcus aureus, respectively. Using human osteoblastic cell line, MG-63, no significant cytotoxicity was observed for the AgNPs-loaded HAp/Col membrane prepared with 6.3-12.5 µg/mL AgNPs colloidal solution. These results suggested that AgNPs-loaded HAp/Col would be a good candidate for antibacterial bone void fillers and coating materials for orthopedic and dental implants.

OBJECTIVES:Hydroxyapatite (HAp)/collagen (Col) cylinders with laminated collagen layers were implanted into the tibial diaphysis of rats and examined histochemically to clarify how the orientation of HAp and Col bone-like nanocomposite fibers in HAp/Col blocks affects bone resorption and formation. METHODS:HAp/Col fibers were synthesized and compressed into cylindrical blocks to mimic bone nanostructures. These were implanted into the cortical bone cavities of 10-week-old male Wistar rats with fiber bundles parallel to the tibial surface. The implants were histologically analyzed at 3, 5, 7, 14, and 28 days after implantation. RESULTS:TRAP-positive osteoclasts appeared after 3-5 days in the lateral region of the graft, where the fiber ends were exposed, but not in the bottom region, where the HAp/Col fibers were parallel to the surface. Osteoclasts were observed in both regions by day 14. PHOSPHO1-positive osteoblasts were first detected on day 5, appearing slightly away from the cylinder laterally but directly on the bottom surface. A few osteoblasts contacted the block laterally, whereas many were observed on the new bone tissue at the bottom, between days 7 and 14. Bone formation was induced earlier in the bottom region, whereas lateral resorption was dominant. This suggested the uncoupling of bone resorption and formation in the early postimplantation stages. However, bone remodeling shifted to coupling between osteoclasts and osteoblasts throughout the cylinder by day 28. CONCLUSION:The orientation of HAp/Col fibers in HAp/Col graft materials substantially affected the preferential induction of bone resorption or formation during the early stages of bone regeneration.

We have previously reported that a novel bioresorbable self‐setting injectable bone paste composed of hydroxyapatite/collagen bone‐like nanocomposite (HAp/Col) and (3‐glycidoxypropyl)trimethoxysilane (GPTMS) was successfully prepared and was replaced with new bone within 3 months of implantation in defects created in porcine tibia. In this study, the HAp/Col‐GPTMS paste was implanted into bone defects in rat tibiae to investigate the initial kinetics and bone tissue response. Even though more than 35% of GPTMS molecules should be eluted rapidly from directly injected pastes according to previously reported cell culture tests, in this study, energy‐dispersive X‐ray spectrometry did not detect Si (GPTMS) deposition in tissues surrounding the paste at 1 day postimplantation. Further, no abnormal inflammatory responses were observed in the surrounding tissues over the test period for both directly injected and prehardened pastes. Companying these observations with the results of the previous animal test (in which the paste was fully resorbed and was substituted with new bone), the eluted GPTMS resolved in no harm in vivo from the initial to final (completely resorbed) stages. Material resorption rates calculated from X‐ray microcomputed tomography (μ‐CT) images decreased with increasing in GPTMS concentration. Histological observations indicated that tartrate‐resistant acid phosphatase (TRAP) active cells, (assumed to be osteoclasts), exist on the periphery of pastes. This result suggested that the paste was resorbed by osteoclasts in the same way as the HAp/Col. Since a good correlation was observed between TRAP active areas in histological sections and material resorption rate calculated from μ‐CT, the TRAP activity coverage ratio offers the possibility to estimate the osteoclastic resorption ratio of materials, which are replaced with bone via bone remodeling process.

AbstractThe development of hemocompatible biomaterials with antithrombogenic surface coatings remains a challenge in cardiovascular applications. There is interest in negatively charged surfaces that inhibit thrombus formation through electrostatic repulsion between the biomaterial surface and negatively charged platelets. Hence, the present study investigated the influence of electrical polarization on the thrombogenicity of titania nanotubes (TNT), which are promising candidates for inhibiting thrombogenicity via surface modification. TNTs were formed on commercially pure titanium plate by the electrochemical anodization technique using platinum as a counter electrode at 60 V for 24 h with two kinds of electrolytes (hydrofluoric acid diluted with dimethyl sulfoxide [D‐TNT] or ethylene glycol [E‐TNT]) followed by an annealing at 540°C for 3 h in air. Both TNTs were mixture of anatase and rutile, and the D‐TNT had a diameter of 108.76 ± 2.55 nm and the E‐TNT, 53.833 ± 2.42 nm. The TNTs were electrically polarized at 100 V of DC field and 400°C for 1 h. Water contact angle measurements showed that the non‐polarized (0‐) TNT surface was hydrophilic whereas the positively (P‐) or negatively (N‐) polarized TNT surfaces showed high‐hydrophilicity. Antithrombogenicity was evaluated using the thrombus coverage area ratio (TCAR) after soaking the TNTs in bovine whole blood. The TCARs for 0‐polarized E‐ and D‐TNTs were 5.30 ± 4.34% and 36.3 ± 5.8% and for P‐polarized E‐TNT and D‐TNT were 1.50 ± 0.77% and 2.76 ± 1.07%, whereas no thrombus formation (0 ± 0%) for N‐polarized E‐TNT and very few thrombus formation (0.12 ± 0.22%) for N‐polarized D‐TNT. The electrostatic repulsion between the N‐polarized E‐TNTs and platelets completely inhibits thrombus formation, which cannot be achieved by the nanomorphology and high‐hydrophilicity of other TNTs. Hence, N‐TNTs formed by electrical polarization are potential candidates for cardiovascular devices, such as artificial heart valves with long‐term hemocompatibility.

Antibacterial-functionalized Ag-loaded hydroxyapatite (HAp) coatings were successfully fabricated by the EPD process, with adding various concentrations of Ag ions. Loaded Ag ions were adsorbed around the surface of HAp particles in the suspension, which made the particles become positively charged, and then were deposited together with the HAp particles onto the surface of titanium substrate. The thickness of deposited Ag-loaded HAp coating was dependent on the Ag addition amount and the coatings have strong adhesion, not only for the deposited HAp particles but also for the loaded Ag ions, due to the use of Mg2+ as inorganic binder. The Ag-loaded HAp coatings show potential application in implant surgery, owing to the surface antibacterial function for preventing bacterial infection in surgery, for improving surgical success. (c) 2021 Elsevier B.V. All rights reserved.

Electrophoretic deposition (EPD) is a simple, rapid, and inexpensive technique to accomplish uniform coatings with controlled thicknesses. The EPD using binders that do not require a thermal degreasing process, which also eliminates the polymer components of the composite, are required for coating polymer-ceramic composites. This study demonstrated the application of a modified EPD technique utilizing Mg2+ ions to coat a bone-like hydroxyapatite/collagen nanocomposite (HAp/Col) on a titanium (Ti) substrate. The coating thickness was successfully controlled by varying the applied voltage and/or the treatment time. The adhesive strength of the modified EPD coating, evaluated by the tape test, showed class 0 (coating was not peeled off) and drastically increased in comparison to that of the non-Mg2+ EPD coating, class 5 (coating was completely peeled off). The MG63 cells on the HAp/Col-coated Ti demonstrated similar proliferation to and superior alkaline phosphatase activity to that on the bare Ti. Thus, the HAp/Col-coated Ti is expected to facilitate the surrounding bone formation than the bare-Ti. The results of the study indicated the HAp/Col-coated Ti prepared by the modified EPD is effective for applications in novel instruments, such as, subperiosteal temporary anchorage devices, which strongly requires rapid osseointegration at the bone-implant surface.

AbstractChanges in fluoride removal ability of chicken bone char (CBC) were investigated by both remained amounts of carbon including organic substances and crystallite size of hydroxyapatite in the CBC. Carbon contents in CBC were controlled by heating time at 600°C. Although temperature for crystal‐grain growth for HAp, 650°C, was higher than 600°C, crystallite size of HAp in CBC increased with heating time. Fluoride ion removal ability positively related to the amount of remaining carbon and negatively related to the square of crystallite size, as an index of surface area, of HAp. These results suggested that fluoride ion removal from water by CBC is not only by ion exchange and/or dissolution‐precipitation process, but also by adsorption by carbon and/or temporal capture of fluoride ion by microstructure of carbonate in CBC before immobilize it in apatite structure.

Whisker-like hydroxyapatite (HAp) particles were prepared by controlling particle growth via hydrothermal synthesis. The surface modification for the hydrothermally synthesized HAp whiskers was accomplished by TiO2 coating. After the TiO2 modification, the zeta potential of the HAp whiskers was significantly improved from +8.6 to +21 mV at pH = 8.5. A free-standing membrane (diameter of ~4.5 cm and thickness of ~0.2 mm) was fabricated by using the TiO2-coated HAp whiskers and was used to separate the Au nanoparticles (size = 5 nm and zeta potential = −38.6 mV at pH = 8.5) at a significantly high filtration efficiency of ~100%. The achieved high filtration efficiency was considered to be the result of effectively utilizing the electrostatic interaction between the positively-charged TiO2-coated HAp whiskers and negatively-charged Au nanoparticles. The excellently biocompatible and highly effective TiO2-coated HAp membrane would be potentially applied as biological and artificial separators in biotechnology processes for the biomedicine field.

A gentamicin-loaded hydroxyapatite/collagen bone-like nanocomposite (GNT-HAp/Col) was fabricated and evaluated for its absorption–desorption properties, antibacterial efficacy, and cytotoxicity. The hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) powder was mixed with gentamicin sulfate (GNT) in phosphate-buffered saline (PBS) at room temperature. After 6 h mixing, the GNT adsorption in all conditions reached plateau by Langmuir’s isotherm, and maximum GNT adsorption amount was 34 ± 7 μg in 250 μg/mL GNT solution. Saturated GNT-loaded HAp/Col powder of 100 mg was soaked in 10 mL of PBS at 37 °C and released all GNT in 3 days. A shaking culture method for a GNT extraction from the GNT-HAp/Col and an inhibition zone assay for the GNT-HAp/Col compact showed antibacterial efficacy to Escherichia coli (E. coli) at least for 2 days. From the release profile of the GNT from the GNT-HAp/Col powder, antibacterial efficacy would affect E. coli at least for 3 days. Further, no cytotoxicities were observed on MG-63 cells. Thus, the GNT-HAp/Col is a good candidate of bioresorbable anti-infection bone void fillers by prevention initial infections, which is the primary cause of implant-associated infection even for rapid bioresorbable materials.

Calcium phosphate-based bone regenerating materials were developed by utilizing interfacial interaction between inorganic­organic substances. Although apatitic calcium phosphates, hydroxyapatite (HAp) and ¢tricalcium phosphate (¢-TCP), have unique affinity to organic substances, and utilization of the affinity requires appropriate surrounding conditions. The author and his colleagues control the surrounding conditions to realize porous HAp ceramics with high porosity, interconnectivity and compressive strength, composite membrane of ¢TCP and polylactide-based biodegradable polymers for guided bone regeneration, and bone-like nanocomposite of HAp and type-I atelocollagen (HAp/Col). Electrostatic interactions between calcium phosphates and polymers in these composites were presented by reflection infrared spectra. They also examined in vitro and in vivo and demonstrate good bone regeneration properties. Particularly, the HAp/Col exhibits completely incorporation into bone remodeling process that is the first in the world for synthetic materials. Three of these materials are also commercialized and used in medical and dental fields and contribute to human health. ©2020 The Ceramic Society of Japan. All rights reserved.

HAp whiskers with preferable growth along the c-axis were synthesized by a hydrothermal method. The hydrothermally-synthesized HAp whiskers were used to fabricate a free-standing membrane (similar to 4 cm in diameter and similar to 400 mu m in thickness) by a facile way of suction evacuation, with exhibiting a unique bird nest-like microstructure. Due to the tough framework, high specific area, and unique fiber-like morphology of the biocompatible HAp whiskers, the nest-like HAp membrane was used to efficiently separate the Au nanoparticles (3 nm) at a high permeability of similar to 79.6 L/m(2).s.bar and, more significantly, with a high retention efficiency of - similar to 91% for efficiently capturing the negatively-charged Au nanoparticles onto the positively-charged dominated a, b-plane in the preferable-growth HAp whiskers. Due to its nontoxicity, excellent biocompatibility, and high separation performance, the whisker-HAp membrane with unique nest-like microstructure would be utilized as biological and artificial separators in biomedicine field.

The process of bone formation onto the bone surface using a hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) was investigated. Immersion tests were performed to evaluate the impact of pH on the degradation of the specimens in an aqueous environment. The specimens were soaked in aqueous solutions of pH 4.0, 5.0, and 7.0. Using standardized images, the top-view areas of the specimens were measured. Animal experiments were performed to investigate the bone formation process onto the bone surface. The specimens were placed under the rat calvarial periosteum, and μCT image analysis and histological observation were performed on samples harvested on postoperative Days 3, 5, and 7. In all experiments, β-tricalciumphosphate (β-TCP) was adopted as the control. HAp/Col turned to gel in acidic environments below pH 5.0. In contrast to the β-TCP, the HAp/Col specimens placed under the periosteum expanded and attained a hollow structure with a gel-filled center, accompanied by larger volume of new bone and appearance of TRAP-positive multinucleated cells on postoperative Day 5. Therefore, HAp/Col can enhance bone formation onto the bone surface via induction of TRAP-positive multinucleated cells, and may have clinical applications.

The Hydroxyapatite (HAp) particles with various unique morphologies are synthesized by a hydrothermal method. The hydrothermal-synthesized HAp particles have different oriented growth mainly along the c- or a, b-axes, as revealed by X-ray diffraction (XRD) patterns and Lotgering factor calculation. The various unique morphologies, involving whisker, sheet, and rod as a result of the orientation growth, are clearly revealed by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) observations. Furthermore, the hydrothermally-synthesized HAp particles are used to fabricate HAp coatings onto the surface of titanium plate by the electrophoresis deposition process (EPD) process. The fabricated HAp coatings have various microstructures like bird-nest, brick-building, and wave-pattern, with achieving an aim of controllable design for microstructure, and present the uniform layer surface and strong adhesion. Therefore, these various microstructured HAp coatings would be expected to meet high versatility in functional requirements for biomedical applications by utilizing their various unique microstructures. (C) 2019 The Electrochemical Society.

This article describes preparation of anti-decay self-setting pastes of hydroxyapatite/collagen (HAp/Col) utilizing (3-glycidoxypropyl)trimethoxysilane (GPTMS). The powder portion of the paste was ball-milled HAp/Col synthesized by the simultaneous titration method, and the liquid portion was GPTMS aqueous solution at a concentration of 0.1, 1.0 or 10 % in volume. The HAp/Col-GPTMS pastes were prepared by mixing the powder and liquid portions at powder/liquid (P/L) ratios ranging from 0.20 to 2.00 (g/cm3). The pastes with P/L ratios from 0.33 to 1.50 showed good handling properties, and their viscosities depended greatly on the P/L ratio. The lowest washout ratio was observed at a P/L ratio of 1.00 independent of the GPTMS concentration. Although cytocompatibilty tests showed that inhibition of cell proliferation depended on the elution amounts of GPTMS from the pastes, an animal test using porcine tibia demonstrated no harmful systemic or local symptoms, because the GPTMS concentration maintained acceptable levels for living tissues through dispersion with body fluid. The animal test also revealed that the paste was completely resorbed and substituted with newly formed bone after 12 weeks implantation. It was concluded based on these results that HAp/Col-GPTMS pastes are promising candidates for use as bioresorbable injectable pastes.

Mixed cationic Ca2+/Na+(Mg2+) polyphosphates, regarded as potential biocomposite fillers, were fabricated by solid-state reactions. Most of them demonstrated low solubility (assessed also by the Glasser and Jenkins approach) from 1 +/- 0.2 g/L for Ca(PO3)(2) to 5 +/- 0.4 g/L for NaCa(PO3)(3) and 50 +/- 2 g/L for soluble phase of NaPO3. Liquid-state NMR of the soluble part of polyphosphates gave the degree of polymerization of their chains ranging from 10 to 30 for NaCa(PO3)(3) and ca. 1000 monomeric units for NaPO3.

This article examines the validity of a test method to determine the torsion strength of bioceramics under in-vivo-mimicking circumstances. The torsion test setup consisted of upper and lower grip jigs, designed to grip dog bone-type bioceramic specimens, and an opening torque tester for PET bottles. A specimen was set on the torque tester through the lower grip jig at the bottom, and the upper grip jig was then mounted on the top end of the specimen. The upper grip jig was rotated by hand to apply torque until the specimen was fractured by the torsion. The torsion strength was calculated using the maximum torque at fracture and the gage diameter. Five calcium phosphate bioceramics were employed for the torsion test. The torsion strength data obtained by this method agreed closely with data measured using a material testing machine with a convertor from the linear crosshead motion into the rotation. Round-robin tests among four different organizations in Japan revealed that the torsion strength data showed good agreement for each sample immersed for 24 hr under phosphate-buffered solution as in-vivo-mimicking circumstances. These results verified the ability of the easy-to-use torsion method to give appropriate strength data with a simple experimental setup.