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Biomedical subjects

M Tanahashi

Publications and source records attributed to M Tanahashi.

31 records · Page 2Linked to original sources
PubMed1997

Surface functional group dependence on apatite formation on self-assembled monolayers in a simulated body fluid.

Self-assembled monolayers (SAMs) of alkanethiols having CH3, PO4H2, COOH, CONH2, OH, and NH2 terminal groups formed on a gold surface via sulfur attachment were soaked in a simulated body fluid (SBF), whose ion concentrations were nearly equal to those of human blood plasma, at 37 degrees C for up to 40 days. The effect of their terminal functional groups on apatite formation was assessed using X-ray photo-electron spectroscopic (XPS) measurement and a quartz crystal microbalance (QCM) technique. The Ca and P atoms were detected, of which element intensities increased with time, on SAMs except for the alkanethiol having the methyl terminal group. The Ca/P atomic ratios of the apatites formed on the SAMs ranged from around 1.0 to around 1.3. The most potent inducer for apatite formation, judged from the growth rate (micrometers per day) calculated from the weight change during QCM measurement, was the SAM of the alkanethiol with the PO4H2 group, followed by that of the alkanethiol with the COOH group. The SAMs of the alkanethiols with the CONH2, OH, and NH2 groups possessed much weaker inducing powers than the former two SAMs. Little weight change was observed for the methyl-group-terminated alkanethiol SAM. The growth rates increased with time, irrespective of the terminal group species among apatite formation-inducing groups. During the experimental observation period, the following relationship held. The growth rate decreased in the order PO4H2 > COOH >> CONH2 approximately equal to OH > NH2 >> CH3 approximately equal to 0. Some negatively charged groups strongly induced apatite formation but the positively charged group did not, it can be said that the apatite formation initiated via calcium ion-absorption upon complexation with a negative surface-charged group may be dominant in biomaterial calcification where ionic species directly contact the biomaterial surface in body fluids.

Alkanes↗
PubMed1997

The effect of TRK-530 on experimental arthritis in mice.

TRK-530 is a newly synthesized diphosphonate derivative. We investigated the effect of TRK-530 on type II collagen-induced arthritis (CIA) in mice in comparison to that of prednisolone and indomethacin. TRK-530 at a dose of 25 mg/kg showed a tendency to inhibit CIA. TRK-530 at a dose of 50 mg/kg inhibited the development of the CIA in terms of the progression of footpad swelling, bone damage and histopathological changes. TRK-530 at a dose of 50 mg/kg also significantly inhibited the delayed type hypersensitivity (DTH) response to type II collagen, but not the production of anti-type II collagen IgG antibody in arthritic mice. To investigate the inhibitory mechanism of TRK-530, the type of effect of TRK-530 on the production of IL-1 beta in vitro was studied. TRK-530 at a concentration of 10(-4) M inhibited LPS-induced IL-1 beta production from J774.1 cells. In conclusion, TRK-530 inhibited CIA in mice. The inhibition of the DTH reaction to type II collagen and the inhibition of IL-1 beta production may partly participate the anti-rheumatoid action of TRK-530.

Animals↗
PubMed1996

Quantitative assessment of apatite formation via a biomimetic method using quartz crystal microbalance.

Quantitative assessment of hydroxyapatite formation on a gold surface via the biomimetic method, composed of a nucleation step in a simulated body fluid (SBF) containing glass powders and a subsequent apatite growth step in glass powder-free SBF, was made using a quartz crystal microbalance (QCM) technique. The frequency change of the QCM linearly increased with increasing soaking time, and largely depended on the nucleation period. The growth rates, defined as daily increase in thickness, increased monotonicly with an increasing nucleation period of up to 96 h, thereafter being constant at 2.0 microns/day. The growth rate of the apatite layer increased with increasing temperature of the SBF: 0.9, 2.0, and 3.8 microns/day at 25, 37, and 50 degrees C, respectively. The Arrhenius-type activation energy for the growth of apatite was 47.3 kJ/mol. The QCM method was found to be a very powerful tool for quantitative, in situ measurement of precipitation and growth of apatite in real time.

Apatites↗
PubMed1996

Bone bonding ability of an apatite-coated polymer produced using a biomimetic method: a mechanical and histological study in vivo.

A 20-microns thick apatite layer was coated onto polyethersulfone (PES) rectangular plates by soaking them in simulated body fluid containing CaO-SiO2 based glass powder. Coated and uncoated PES plates (10 x 15 x 1.5 mm) were implanted in the tibiae of rabbits, which were sacrificed 8, 16, and 30 weeks thereafter, and the samples were examined histologically using contact microradiography (CMR), Giemsa surface staining, and a scanning electron microscope connected to an electron probe microanalyzer (SEM-EPMA). The tensile failure loads at the bone/implant interfaces were determined using the detaching test. The histological examinations showed excellent bone apposition on coated PES and the sign of degradation of the apatite layer at remodeling lacunae. The apatite layer underwent complete resorption and was replaced by bone in most areas of the bone/implant interface after 30 weeks. Bone did not bond directly to uncoated PES after each follow-up period. The failure loads between bone and coated PES at 8, 16, and 30 weeks after implantation were 1.7 +/- 0.35, 2.36 +/- 0.53, and 1.45 +/- 0.48 kg, respectively. Those between bone and uncoated PES were nearly 0 kg at each postimplantation period. Failure during the detaching test occurred at the bone/apatite interface or near it after 8 weeks. After 16 weeks, it usually occurred at the apatite/ PES interface or near it, and occasionally in the middle of the apatite layer. The apatite layer was hardly detected at the failured interface after 30 weeks. In this study, an apatite-coated PES produced using a biomimetic method was demonstrated to bond directly to bone without any intervening soft tissue, which indicates that this material possesses excellent bioactivity.

Animals↗
PubMed1996

Activation of osteoclast-mediated bone resorption by the supernatant from a rabbit synovial cell line in response to polyethylene particles.

It is unknown whether the soluble factors produced from cells activated by wear particles in the fibrous tissue around failed joint prostheses really activate osteoclastic bone resorption. In this study, the activation of osteoclast-mediated bone resorption by the products from a rabbit synovial cell line (HIG-82) stimulated by various particles was investigated using rabbit unfractionated bone cells cultured on a dentin slice. The HIG cells were challenged with the following laboratory-made particles: high-density polyethylene (PE), cobalt alloy (Co-Cr), titanium alloy (Ti6Al4V), pure titanium (Ti), and sintered hydroxyapatite (HA). The size of each particle was < 2 microns. The supernatants from HIG cells cultured with the appropriate concentration of wear particles were added to unfractionated bone cells on a dentin slice, and then resorbed areas were determined for each particle. Interestingly, resorbed areas significantly increased only when the culture medium from HIG cells with PE particles was added to unfractionated bone cells. This study demonstrates that PE particles stimulate the rabbit synovial cells to produce soluble factors that induce osteoclast-mediated bone resorption. Moreover, this experimental model is a useful method sensitively to evaluate the effects of soluble factors from the cells stimulated by particulate biomaterials from joint prostheses on osteoclastic bone resorption.

Animals↗
PubMed1996

Differences of bone bonding ability and degradation behaviour in vivo between amorphous calcium phosphate and highly crystalline hydroxyapatite coating.

Three types of calcium phosphate coating were formed on polyethersulphone (PES) rectangular plates using a biomimetic method: a 20 microns thick amorphous calcium phosphate (ACP 20) coating, a 50 microns thick amorphous calcium phosphate (ACP 50) coating, and a 50 microns thick highly crystalline hydroxyapatite (hHA 50) coating. Uncoated PES plates were used as a control group. These materials were implanted in the tibiae of rabbits and subcutaneously in rats, and the samples were harvested 8 and 16 weeks thereafter, and were examined histologically. The tensile failure loads at the bone-implant interfaces were determined using the detaching test. Each ACP coating was more degradable than the hHA 50 coating. However, newly formed bone came into direct contact with underlying materials as the coating degraded. No coating degraded in subcutaneous tissue. Soft tissue intervening was seen in uncoated samples. Failure load of ACP 20-, ACP 50- and hHA 50-coated samples were all relatively higher than that of the uncoated samples at each period. Significant increase of failure load was seen in hHA 50-coated samples by 16 weeks, however, no increase was seen in either the uncoated or ACP-coated samples. If coating longevity is desired, then the hHA coating is preferable. However, if only the osteoconducive property of calcium phosphate coating is desired for initial fixation of porous materials, the ACP coating may be advantageous.

Animals↗
PubMed1996

Ultrastructural study of an apatite layer formed by a biomimetic process and its bonding to bone.

A dense and uniform apatite layer about 20 microns thick was formed on a poly(ether sulphone) (PESF) substrate treated with glow discharge in O2 gas by a biomimetic process. The apatite-polymer composite obtained was implanted into a rabbit tibia and the structure of the PESF-apatite-bone interface was observed under a scanning and a transmission electron microscope 8 weeks after implantation. The apatite layer formed by the biomimetic process was confirmed to consist of small crystals of apatite with a structure similar to that of apatite in bone. The apatite layer remained on the substrate in the body, and bonded to the apatite in bone directly. This type of apatite-organic polymer composite expected to be useful as bone-repairing material.

Animals↗
PubMed1995

Apatite coated on organic polymers by biomimetic process: improvement in its adhesion to substrate by glow-discharge treatment.

A dense, uniform, and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure: First, a substrate is set in contact with particles of bioactive CaO-SiO2-based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma so that a number of apatite nuclei are formed on the substrate. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5SBF) so that the apatite nuclei grow in situ. In the present study, organic polymer substrates were treated with glow-discharge in O2 gas atmosphere, then subjected to the above-mentioned biomimetic process. The induction periods for the apatite nucleation on all the examined organic polymers were reduced from 24 to 6 h, with glow-discharge treatment. The adhesive strengths of the formed apatite layer to the substrates increased from about 4 to 10 MPa for poly(ethylene terephthalate) and poly-ether sulfone, and from 1 approximately 2 to 6 approximately 7 MPa even for poly(methyl methacrylate), polyamide 6 and polyethylene. It is supposed that highly polar groups such as carbonyl, ester, hydroxyl, and carboxyl ones formed by glow-discharge treatment increased the affinity of a silicate ion with the substrates to decrease the induction period, and also increased the affinity of the apatite with the substrate to increase the adhesive strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesiveness↗
PubMed1994

Apatite coated on organic polymers by biomimetic process: improvement in its adhesion to substrate by NaOH treatment.

A dense, uniform and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure. First, a substrate is set in contact with particles of bioactive CaO SiO2 based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates treated with 5 M NaOH solution were subjected to the above mentioned biomimetic process. The induction periods for the apatite nucleation on polyethyleneterephthalate (PET), polymethylmethacrylate (PMMA), polyamide 6 (PA6), and polyethersulfone (PESF) substrates were reduced from 24 to 12 h with the NaOH treatment. The adhesive strength of the formed apatite layer were increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa, and from 0.6 to 5.3 MPa with the NaOH treatment, for PET, PMMA, and PA 6, respectively. It was assumed that highly polar groups, such as carboxyl and sulfinyl ones formed by the hydrolysis of an ester group on PET and PMMA and of an amide group on PA 6, or of a sulfonyl group on PESF with the NaOH treatment, attached a large number of hydrated silica dissolved from the glass particles, to accelerate the apatite nucleation, and also to form a strong bond with the apatite. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing as well as soft tissue-repairing materials.

Adhesiveness↗