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Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration accompanied by dilated cardiomyopathy. Recently, abnormality of yes-associated protein (YAP) has been reported as the pathogenesis of muscle degeneration of DMD; however YAP activity remains unclear in dystrophic heart of DMD. Herein, we investigated YAP activity using disease-specific induced pluripotent stem cell (iPSC) derived cardiomyocytes (CMs) in DMD. DMD-iPSCs were generated from DMD patient with exon 48–54 deletion in DMD, and genome-edited (Ed)-DMD-iPSCs with in-frame (Ed-DMD-iPSCs) were created using CRISPR/Cas9. Nuclear translocation of YAP [nuclear (N)/cytoplasmic (C) ratio] was significantly lower in DMD-iPSC-CMs than in Ed-DMD-iPSC-CMs. In addition, Ki67 expression, indicating proliferative ability, was significantly lower in DMD-iPSC-CMs than Ed-DMD-iPSC-CMs. Therefore, immunofluorescent staining showed that actin stress fibers associated with YAP activity by mechanotransduction were disorganized in DMD-iPSC-CMs. Lysophosphatidic acid (LPA), a known lipid mediator on induction of actin polymerization, significantly increased YAP activity and actin dynamics in DMD-iPSC-CMs using live cell imaging. These results suggested that altered YAP activity due to impaired actin dynamics reduced proliferative ability in DMD-iPSC-CMs. Hence, decreased YAP activity in dystrophic heart may contribute to DMD-cardiomyopathy pathogenesis.

Arrhythmogenic cardiomyopathy (ACM) caused by TMEM43 p.S358L is a fully penetrant heart disease that results in impaired cardiac function or fatal arrhythmia. However, the molecular mechanism of ACM caused by the TMEM43 variant has not yet been fully elucidated. In this study, we generated knock-in (KI) rats harboring a Tmem43 p.S358L mutation and established induced pluripotent stem cells (iPSCs) from patients based on the identification of TMEM43 p.S358L variant from a family with ACM. The Tmem43-S358L KI rats exhibited ventricular arrhythmia and fibrotic myocardial replacement in the subepicardium, which recapitulated the human ACM phenotype. The four-transmembrane protein TMEM43 with the p.S358L variant (TMEM43S358L ) was found to be modified by N-linked glycosylation in both KI rat cardiomyocytes and patient-specific iPSC-derived cardiomyocytes. TMEM43S358L glycosylation increased under the conditions of enhanced endoplasmic reticulum (ER) stress caused by pharmacological stimulation or age-dependent decline of the ER function. Intriguingly, the specific glycosylation of TMEM43S358L resulted from the altered membrane topology of TMEM43. Moreover, unlike TMEM43WT , which is mainly localized to the ER, TMEM43S358L accumulated at the nuclear envelope of cardiomyocytes with the increase in glycosylation. Finally, our comprehensive transcriptomic analysis demonstrated that the regional differences in gene expression patterns between the inner and outer layers observed in the wild type myocardium were partially diminished in the KI myocardium prior to exhibiting histological changes indicative of ACM. Altogether, these findings suggest that the aberrant accumulation of TMEM43S358L underlies the pathogenesis of ACM caused by TMEM43 p.S358L variant by affecting the transmural gene expression within the myocardium.

In contrast to hypertrophic cardiomyopathy, there has been reported no specific pattern of cardiomyocyte array in dilated cardiomyopathy (DCM), partially because lack of alignment assessment in a three-dimensional (3D) manner. Here we have established a novel method to evaluate cardiomyocyte alignment in 3D using intravital heart imaging and demonstrated homogeneous alignment in DCM mice. Whilst cardiomyocytes of control mice changed their alignment by every layer in 3D and position twistedly even in a single layer, termed myocyte twist, cardiomyocytes of DCM mice aligned homogeneously both in two-dimensional (2D) and in 3D and lost myocyte twist. Manipulation of cultured cardiomyocyte toward homogeneously aligned increased their contractility, suggesting that homogeneous alignment in DCM mice is due to a sort of alignment remodelling as a way to compensate cardiac dysfunction. Our findings provide the first intravital evidence of cardiomyocyte alignment and will bring new insights into understanding the mechanism of heart failure.

The zirconia used in dental implants requires excellent mechanical and chemical properties such as high strength, high biological performance, corrosion resistance, and phase stability. In this study, after we prepared a highly fluidized solution of calcium phosphate, we fabricated a hydroxyapatite (HA) coating layer on a zirconia substrate using the sol–gel method to enhance its biocompatibility and bone-bonding ability. We dipped the zirconia substrate into the calcium phosphate sol to obtain the HA-coated film, which was dried at room temperature. The phase change and microstructural evolution were examined while the coating dried and during heat treatment. The biological activity of the coated and as-received substrates was evaluated using an in vitro experiment and the results were compared. The HA-coated film showed a highly dense and uniform layer structure, while its physical and biological properties depended on the starting substrate, coating times, and processing conditions.

Human induced pluripotent stem (hiPS) cells have been used as a cell source for regenerative therapy and disease modeling. The purity of hiPS-cardiomyocytes (hiPS-CMs) has markedly improved with advancements in cell culture and differentiation protocols. However, the morphological features and molecular properties of the relatively immature cells are still unclear, which has hampered their clinical application. The aim of the present study was to investigate the extent to which topographic substrates actively influence hiPS-CMs. hiPS-CMs were seeded on randomized oriented fiber substrate (random), anisotropic aligned fiber substrate (align), and flat non-scaffold substrate (flat). After culturing for one week, the hiPS-CMs on the aligned patterns showed more mature-like properties, including elongated rod shape, shorter duration of action potential, accelerated conduction velocity, and elevated cardiac gene expression. Subsequently, to determine whether this development was irreversible or was altered after withdrawal of the structural support, the hiPS-CMs were harvested from the three different patterns and reseeded on the non-scaffold (flat) pattern. After culturing for one more week, the improvements in morphological and functional properties diminished, although hiPS-CMs pre-cultured on the aligned pattern retained the molecular features of development, which were even more significant as compared to that observed during the pre-culture stage. Our results suggested that the anisotropic fiber substrate can induce the formation of geometrical mimic-oriented heart tissue in a short time. Although the morphological and electrophysiological properties of hiPS-CMs obtained via facilitated maturation somehow rely on the existence of an exterior scaffold, the molecular developmental features were preserved even in the absence of the external support, which might persist throughout hiPS-CM development.

Bacterial biofilms formed through secretion of extracellular polymeric substances (EPS) have been implicated in many serious infections and can increase antibiotic resistance by a factor of more than 1000. Here, we examined the abilities of the antimicrobial peptide HPA3NT3-A2 to inhibit and reduce biofilm formation, eliminate EPS, and suppress inflammation in mice infected with clinical isolates of drug-resistant Pseudomonas aeruginosa strains. HPA3NT3-A2 was developed from a desirable analogue peptide, HPA3NT3, derived from residues 2–20 of the Helicobacter pylori ribosomal protein L1. HPA3NT3-A2 showed stronger activity against planktonic cells (MIC: 8 μM) compared to ciprofloxacin or tobramycin (>512 μM), and a favorable minimum biofilm inhibition and elimination concentration. This peptide also neutralized LPS; decreased levels of EPS; inhibited the production of pro-inflammatory cytokines in the lung, kidney, and spleen; decreased white blood cell counts; and increased survival among infected mice.

Dental implants are typically composed of 3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals). Most dental zirconia implants are currently fabricated via mechanical machining. However, during the machining of zirconia green bodies, many cracks form on the surface. To prevent surface crack formation on the implants, shape forming of the zirconia is necessary using methods such as slip casting. Herein, we fabricated green compacts using slip casting, candidate forming process to reduce surface cracking. To fabricate an optimal 3Y-TZP implant by slip casting and sintering, we prepared a suitable 3Y-TZP slurry for slip casting by adjusting the viscosity via pH, dispersant agent content, and solid loading refinement. Green compacts were prepared by the slip casting of all-ceramic zirconia implants fabricated using optimal slurry conditions, for example, 60 wt% solid content, 1 wt% dispersant, pH 12 and post-sintering at 1450 °C for 2 h. All sintered bodies contained a tetragonal phase with a high sintered density of approximately 6.07 g/cm3, good mechanical hardness of approximately 1367 Hv, grain size of 220 nm, and high surface roughness without cracks.

Background Fabry disease is an X-linked disease caused by mutations in α-galactosidase A (GLA); these mutations result in the accumulation of its substrates, mainly globotriaosylceramide (Gb3). The accumulation of glycosphingolipids induces pathogenic changes in various organs, including the heart, and Fabry cardiomyopathy is the most frequent cause of death in patients with Fabry disease. Existing therapies to treat Fabry disease have limited efficacy, and new approaches to improve the prognosis of patients with Fabry cardiomyopathy are required. Methods and results We generated induced pluripotent stem cell (iPSC) lines from a female patient and her son. Each iPSC clone from the female patient showed either deficient or normal GLA activity, which could be used as a Fabry disease model or its isogenic control, respectively. Erosion of the inactivated X chromosome developed heterogeneously among clones, and mono-allelic expression of the GLA gene was maintained for a substantial period in a subset of iPSC clones. Gb3 accumulation was observed in iPSC-derived cardiomyocytes (iPS-CMs) from GLA activity-deficient iPSCs by mass-spectrometry and immunofluorescent staining. The expression of ANP was increased, but the cell surface area was decreased in iPS-CMs from the Fabry model, suggesting that cardiomyopathic change is ongoing at the molecular level in Fabry iPS-CMs. We also established an algorithm for selecting proper Gb3 staining that could be used for high-content analysis-based drug screening. Conclusions We generated a Fabry cardiomyopathy model and a drug screening system by using iPS-CMs from a female Fabry patient. Drug screening using our system may help discover new drugs that would improve the prognosis of patients with Fabry cardiomyopathy.

// Jong-Kook Lee 1, 3 , Tudor Luchian 2 and Yoonkyung Park 1, 3 1 Research Center for Proteinaceous Materials, Chosun University, Gwangju, Korea 2 Department of Physics, Alexandru I. Cuza University, Iasi, Romania 3 Department of Biomedical Science, Chosun University, Gwangju, Korea Correspondence to: Yoonkyung Park, email: y_k_park@chosun.ac.kr Tudor Luchian, email: luchian@uaic.ro Keywords: Staphylococcus aureus; clavaspirin peptide (CSP); toll-like receptor-2 (TLR-2); nuclear factor-kappa B (NF-κB); pro-inflammatory cytokine Received: November 03, 2017 Accepted: February 20, 2018 Epub: February 26, 2018 Published: March 20, 2018 ABSTRACT Clavaspirin peptide (CSP) is derived from the pharyngeal tissues of the tunicate Styela clava . The 23-amino acid peptide is histidine-rich and amidated at the N-terminus. CSP possesses low antimicrobial and high hemolytic activity at pH 7.4. Therefore, we designed 4 CSP analogs with substituted hydrophobic amino acids to reduce hydrophobic amino acid interactions. These modifications reduced the aggregation and cytotoxicity of the analogs at pH 7.4. The analogs also showed potent antimicrobial activity by accumulating on bacterial cell surfaces and inducing the lytic mechanism against gram-negative and gram-positive cells at pH 5.5 and 7.4. Moreover, exposure to the CSP-4 analog for up to 29 passages did not induce drug resistance in Staphylococcus aureus . Application of CSP-4 to inflamed skin of hairless mice infected with drug-resistant S. aureus (DRSA) significantly reduced skin infections without damaging dermal collagen or elastin. Topically applied CSP-4 penetrated 25–40 μm in the dermis within 30 min, reducing the levels of Toll-like receptor-2, nuclear factor kappa B (NF-κB), and the pro-inflammatory cytokines tumor necrosis factor- α (TNF-α) and interleukin-1β (IL-1 β). These results suggest that CSP-4 could be a promising topical antimicrobial agent for skin diseases caused by DRSA such as S. aureus CCARM 0027.

Nanocrystalline zirconia with high surface area and pure tetragonal crystalline phase was prepared using ethylene diamine (EDA), which acts as both precipitating agent and dispersant of the zirconium precursor. The yttria stabilized zirconia (Y-TZP) is a very attractive material due to its excellent biocompatibility, high fracture toughness, high strength and low wear rates. So zirconyl chloride octahydrate (ZrOCl2 · 8H2O) and yttrium chloride hexahydrate (YCl3 · 6H2O) in different molar ratios were used as starting solution. The detailed effects of various process parameters such as reaction time, concentration of the precursor solution, amount of ethylene diamine, and calcination temperature on the structural properties of the zirconia powders were investigated. The preparation conditions significantly affected the structural stability, crystal size, and crystal phase of the final material. Increases in the reaction time and amount of ethylene diamine led to a substantial increase of the crystal growth rate, the specific surface area, and the tetragonal content of the zirconia.

Organic/inorganic biocomposite materials for biodegradable fixation medical devices require osteoconductivity, biocompatibility, and adequate mechanical properties with biodegradation behavior. The objective of this study was to investigate the effect of Si ions substituted in β-tricalcium phosphate (β-TCP) on the mechanical properties of organic/inorganic biocomposites. Biodegradable composite materials were prepared with polylactic acid (PLA) as the matrix and nano Si-substituted β-TCP as the osteoconductive filler by solvent mixing and conventional molding. The nanostructured Si-substituted β-TCP powders were synthesized by co-precipitation, controlling the quantity of Si ions. The amount of nanostructured Si-substituted β-TCP powders in composites was varied in the 0-40 wt% range and the material properties were compared with those of pure β-TCP/PLA composites. The influence of Si ions on the mechanical properties of the composites was evaluated by tensile and flexural tests.

Osteoconductive, biocompatible, and resorbable organic/inorganic composites are most commonly used in fixation medical devices, such as suture anchors and interference screws, because of their unique physical and chemical properties. Generally, studies on biodegradable composites have focused on their mechanical properties based on the composition and the individual roles of organic and inorganic biomaterials. In this study, we prepared biodegradable organic/inorganic nanocomposite materials using the solvent mixing process and conventional molding. We used polylactic acid (PLA) as the matrix and nano-sized hydroxyapatite (nano-HAp) as the osteoconductive filler. The content of nano-HAp was varied in 0-30 wt% and its influence on the In-Vitro mechanical performance of PLA/HAp nanocomposites was evaluated. The In-Vitro mechanical properties of nanocomposites were evaluated using standardized tensile and flexural tests after different immersion times in simulated body fluid.

The antimicrobial peptide HPA3 shows anticancer activity in gastric cancer and leukaemia. However, how HPA3 exerts its anticancer activity, as well as whether it also exhibits activity in other cancers, remains unknown. Therefore, the aim of this study was to evaluate the anticancer activity of HPA3 and its analogues in colon cancer and to elucidate the mechanisms responsible for this activity. HPA3P decreased cell viability, whereas HPA3 and HPA3P2 did not decrease cell viability in colon cancer cells compared with control cells. This reduction in cell viability occurred through necrosis, a conclusion supported by our observation of the release of cellular contents, our intracellular PI staining results, and our observation of the release of HMGB1. Moreover, RIPK3 inhibition blocks the reduction of cell viability by HPA3P. Consistent with this finding, we found that knocking down RIPK3 and MLKL, key necroptosis proteins, attenuates the reductions in cell viability induced by HPA3P. Furthermore, HPA3P can improve the anticancer activity of chemotherapeutic agents and exhibits anticancer activity in other cancer cells. These results suggest that HPA3P may have potential as an anticancer agent in the treatment of colon cancer.

Drug-resistant microorganism infections cause serious disease and can lead to mortality and morbidity. In particular, Staphylococcus aureus induces pyrogenic and toxigenic infections, and drug-resistance occurs rapidly. Multidrug-resistant S. aureus, such as methicillin-resistant S. aureus and methicillin-sensitive S. aureus, can also cause immunodeficiency and immune deficiency syndrome from lipoteichoic acid. However, antimicrobial peptides, such as KW4, have strong antimicrobial activity, low cytotoxicity, and high neutralization activity against endotoxin substances from Gram-negative bacteria. The objective of this study was to use a synthetic KW4 antimicrobial peptide to evaluate the inhibition of drug-resistance development, antimicrobial activity, and neutralizing activity in S. aureus Gram-positive bacteria. The KW4 peptide showed strong antimicrobial activity against drug-resistant S. aureus strains and significantly increased the anti-neutralizing activity of lipoteichoic acid in S. aureus 1630 drug-resistant bacteria. In addition, S. aureus ATCC 29213 did not develop resistance to KW4 as with other antibiotic drugs. These results suggest that the KW4 peptide is an effective antibiotic and anti-neutralizing agent against multidrug-resistant S. aureus strains.

Hemoglobin (Hb) includes oxygen-bound oxyhemoglobin (HbO2), oxygen-free deoxyhemoglobin (deoxyHb), and methemoglobin (metHb), which underwent protein denaturation by heat. The absorption curve of HbO2 reaches a peak at 418 nm, reaches a small peak at 542 and 577 nm, then decreases, and finally forms a smaller peak at 940 nm. DeoxyHb reaches peaks at 430 and 555 nm and reaches a peak once again between 800 and 1200 nm (Fig. 6.1) [1, 2].

Ectopic foci from pulmonary veins (PVs) comprise the main trigger associated with the initiation of atrial fibrillation (AF). An abrupt anatomical narrow-to-wide transition, modeled as in vitro geometrical patterning with similar configuration in the present study, is located at the junction of PVs and the left atrium (LA). Complex cellular composition, i.e., constituent cell heterogeneity, is also observed in PVs and the PVs-LA junction. High frequency triggers accompanied with anatomical irregularity and constituent cell heterogeneity provoke impaired conduction, a prerequisite for AF genesis. However, few experiments investigating the effects of these factors on electrophysiological properties using human-based cardiomyocytes (CMs) with atrial properties have been reported. The aim of the current study was to estimate whether geometrical patterning and constituent cell heterogeneity under high frequency stimuli undergo conduction disturbance utilizing an in vitro two-dimensional (2D) monolayer preparation consisting of atrial-like CMs derived from human induced pluripotent stem cells (hiPSCs) and atrial fibroblasts (Fbs). We induced hiPSCs into atrial-like CMs using a directed cardiac differentiation protocol with the addition of all-trans retinoic acid (ATRA). The atrial-like hiPSC-derived CMs (hiPSC-CMs) and atrial Fbs were transferred in defined ratios (CMs/Fbs: 100%/0% or 70%/30%) on manually fabricated plates with or without geometrical patterning imitating the PVs-LA junction. High frequency field stimulation emulating repetitive ectopic foci originated in PVs were delivered, and the electrical propagation was assessed by optical mapping. We generated high purity CMs with or without the ATRA application. ATRA-treated hiPSC-CMs exhibited significantly higher atrial-specific properties by immunofluorescence staining, gene expression patterns, and optical action potential parameters than those of ATRA-untreated hiPSC-CMs. Electrical stimuli at a higher frequency preferentially induced impaired electrical conduction on atrial-like hiPSC-CMs monolayer preparations with an abrupt geometrical transition than on those with uniform geometry. Additionally, the application of human atrial Fbs to the geometrically patterned atrial-like hiPSC-CMs tended to further deteriorate the integrity of electrical conduction compared with those using the atrial-like hiPSC-CM alone preparations. Thus, geometrical narrow-to-wide patterning under high frequency stimuli preferentially jeopardized electrical conduction within in vitro atrial-like hiPSC-CM monolayers. Constituent cell heterogeneity represented by atrial Fbs also contributed to the further deterioration of conduction stability.

Voltage-dependent K+ (KV) channels control K+ permeability in response to shifts in the membrane potential. Voltage sensing in KV channels is mediated by the positively charged transmembrane domain S4. The best-characterized KV channel, KvAP, lacks the distinct hydrophilic region corresponding to the S3–S4 extracellular loop that is found in other K+ channels. In the present study, we evaluated the topogenic properties of the transmembrane regions within the voltage-sensing domain in KvAP. S3 had low membrane insertion activity, whereas S4 possessed a unique type-I signal anchor (SA-I) function, which enabled it to insert into the membrane by itself. S4 was also found to function as a stop-transfer signal for retention in the membrane. The length and structural nature of the extracellular S3–S4 loop affected the membrane insertion of S3 and S4, suggesting that S3 membrane insertion was dependent on S4. Replacement of charged residues within the transmembrane regions with residues of opposite charge revealed that Asp72 in S2 and Glu93 in S3 contributed to membrane insertion of S3 and S4, and increased the stability of S4 in the membrane. These results indicate that the SA-I function of S4, unique among K+ channels studied to date, promotes the insertion of S3 into the membrane, and that the charged residues essential for voltage sensing contribute to the membrane-insertion of the voltage sensor domain in KvAP.

Antimicrobial peptides (AMPs) are a promising new class of antibacterial compounds. However, their applications in the treatment of intracellular pathogenic bacteria have been limited by their in vivo instability and low penetrating ability into mammalian cells. Here, we report that gold nanoparticles conjugated with DNA aptamer (AuNP-Apt) efficiently delivered AMPs into mammalian living systems with enhanced stability of the AMPs. C-terminally hexahistidine-tagged A3-APO (A3-APO His ) AMPs were loaded onto AuNPs conjugated with His-tag DNA aptamer (AuNP-Apt His ) by simple mixing and were delivered into Salmonella enterica serovar Typhimurium ( S. Typhimurium)-infected HeLa cells, resulting in the increased viability of host cells due to the elimination of intracellular S. Typhimurium cells. Furthermore, the intravenous injection of AuNP-Apt His loaded with A3-APO His into S. Typhimurium -infected mice resulted in a complete inhibition of S. Typhimurium colonization in the mice organs, leading to 100% survival of the mice. Therefore, AuNP-Apt His can serve as an innovative platform for AMP therapeutics to treat intracellular bacterial infections in mammals.

A thermochemical nonequilibrium analysis was performed under the low enthalpy shock-tunnel flows. A quasi-one-dimensional flow calculation was employed by dividing the flow calculations into two parts, for the shock-tube and the Mach 6 nozzle. To describe the thermochemical nonequilibrium of the low enthalpy shock-tunnel flows, a three-temperature model is proposed. The three-temperature model treats the vibrational nonequilibrium of O2 and NO separately from the single nonequilibrium energy mode of the previous two-temperature model. In the three-temperature model, electron-electronic energies and vibrational energy of N2 are grouped as one energy mode, and vibrational energies of O2, O2+, and NO are grouped as another energy mode. The results for the shock-tunnel flows calculated using the three-temperature model were then compared with existing experimental data and the results obtained from one- and two-temperature models, for various operating conditions of the K1 shock-tunnel facility. The results of the thermochemical nonequilibrium analysis of the low enthalpy shock-tunnel flows suggest that the nonequilibrium characteristics of N2 and O2 need to be treated separately. The vibrational relaxation of O2 is much faster than that of N2 in low enthalpy condition, and the dissociation rate of O2 is manly influenced by the species vibrational temperature of O2. The proposed three-temperature model is able to describe the thermochemical nonequilibrium characteristics of N2 and O2 behind the incident and reflected shock waves, and the rapid vibrational freezing of N2 in nozzle expanding flows.

Novel antibiotic drugs are urgently needed because of the increase in drug-resistant bacteria. The use of antimicrobial peptides has been suggested to replace antibiotics as they have strong antimicrobial activity and can be extracted from living organisms such as insects, marine organisms, and mammals. HPA3NT3-A2 ([Ala1,8] HPA3NT3) is an antimicrobial peptide that is an analogue of the HP (2&ndash, 20) peptide derived from Helicobacter pylori ribosomal protein L1. Although this peptide was shown to have strong antimicrobial activity against drug-resistant bacteria, it also showed lower toxicity against sheep red blood cells (RBCs) and HaCaT cells compared to HPA3NT3. The l-Lys residues of HPA3NT3-A2 was substituted with d-Lys residues (HPA3NT3-A2D, [d-Lys2,5,6,9,10,15] HPA3NT3-A2) to prevent the cleavage of peptide bonds by proteolytic enzymes under physiological conditions. This peptide showed an increased half-life and maintained its antimicrobial activity in the serum against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (pathogen). Furthermore, the antimicrobial activity of HPA3NT3-A2D was not significantly affected in the presence of mono- or divalent ions (Na+, Mg2+, Ca2+). Finally, l- or d-HPA3NT3-A2 peptides exhibited the strongest antimicrobial activity against antibiotic-resistant bacteria and failed to induce resistance in Staphylococcus aureus after 12 passages.

Amphotericin B (AmB) has been widely used against fungal infections throughout almost the entire body, including the skin, nails, oral cavity, respiratory tract, and urinary tract. However, the development of AmB-loaded nanoparticles demands a novel technique that reduces its toxicity and other associated problems. Here, we developed a pH-responsive and redox-sensitive polymer-based AmB-delivery carrier system. In particular, this system was functionalized by conjugation with the antifungal peptide histatin 5, which acts both as a targeting ligand and a synergistic antifungal molecule against Candida albicans, a major systemic fungal pathogen of humans. Our results in vitro and in vivo suggest that this drug-delivery system may serve as a novel tool to facilitate the use of antimicrobial peptides as targeting ligands to pathogenic microbes, which would open new avenues of investigation in the field of drug delivery.

We present herein a first proof of concept demonstrating the potential of a protein nanopore-based technique for real-time detection of selected Gram-negative bacteria (Pseudomonas aeruginosa or Escherichia coli) at a concentration of 1.2 × 108 cfu/mL. The anionic charge on the bacterial outer membrane promotes the electrophoretically driven migration of bacteria towards a single α-hemolysin nanopore isolated in a lipid bilayer, clamped at a negative electric potential, and followed by capture at the nanopore’s mouth, which we found to be described according to the classical Kramers’ theory. By using a specific antimicrobial peptide as a putative molecular biorecognition element for the bacteria used herein, we suggest that the detection system can combine the natural sensitivity of the nanopore-based sensing techniques with selective biological recognition, in aqueous samples, and highlight the feasibility of the nanopore-based platform to provide portable, sensitive analysis and monitoring of bacterial pathogens. Electronic supplementary material The online version of this article (doi:10.1186/s11671-016-1715-z) contains supplementary material, which is available to authorized users.

Removed due to double publication

Refractory castables containing calcium aluminate cement (CAC) are widely used in a range of furnace lining applications in the iron and steel, cement, glass, ceramic, and petrochemical industries. However, magnesia-phosphate cement (MPC) based material could be a new types of cement material, with many advantages such as rapid hydration, high early strength and circumstance suitability, which has very important value and wide application. In this study, MPC was used at Chromia/Alumina castable as binder addition instead of conventional calcium aluminate cement. Meanwhile, it also explains the relationship between the micro-mechanism and performance by micro methods such as SEM. The results shows that MPC based castables have good corrosion resistance, interface adhesiveness and abrasion resistance.

Biphasic calcium phosphate bioceramics were fabricated from the recycling of bone ash which is mostly used as raw materials of bone china. Precursor calcium phosphate powders were prepared by soaking the commercial bone ash in 0.1 M of NaOH solution at 80°C for 4 h. Calcium phosphate powders was obtained by calcination at 800°C for 1 h to completely remove residual organics. Biphasic calcium phosphate bioceramics which is composed of hydroxyapatite and tricalcium phosphate was fabricated by the sintering of pressed compacts at 1200°C for 1 h under moisture protection. The bone ash derived-biphasic calcium phosphate ceramics consists of mostly HA and small amounts of α-tricalcium phosphate, magnesium oxide and calcium oxide. After polishing the HA ceramics, they were immersed in buffered water at 37°C for 3 and 7 days. The bone ash derived- biphasic calcium phosphate ceramics show high biostability in liquid environment with immersion time compared with commercial calcium phosphate ceramics.

This work describes dissolution and related mechanical weakening of phase-pure and dense hydroxyapatite (HA) in distilled water of pH 7.4. Phase-pure HA powder has been synthesized by a wet precipitation method. After uniaxial and cold isostatic pressing, and sintering at 1200°C, dense HA with 98% above of the theoretical density has been obtained. The results show that HA powder has stoichiometric composition with a Ca/P ratio 1.67 ± 0.02. Even after extended exposure for 10 h, no second phases, such as tricalcium phosphate (TCP) and calcium oxide can be observed. Although the HA is supposed to be stable in liquid environment, surface dissolution appears specifically at material’s grain boundaries after immersion for 7 days. Following further immersion to 14 days, grain boundary dissolution progresses interior to the bulk following these paths. This dissolving behavior generates HA particles, disintegrates dense microstructure and at least forms micron-scale cavity. Mechanical property of the HA has been also affected. Fracture toughness (KIc) of the HA sintered body is approximately 1.0 MPa•m1/2. It drastically decreases to almost half of the initial value due to the severe surface dissolution

In situ preparation of magnesium (Mg) substituted biphasic calcium phosphate (BCP) of hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) were carried out through aqueous co-precipitation method. The concentrations of added magnesium were varied with the calcium in order to obtain constant (Ca + Mg)/P ratios of 1.602. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized magnesium substituted BCP powders. The results have shown that substitution of magnesium in the calcium deficient apatites revealed the formation of biphasic mixtures of different HAp/β-TCP ratios after heating at 1000 °C. The ratios of the formation of phase mixtures were dependent on the content of magnesium. After immersing in Hanks’ balanced salt solution (HBSS) for 1 week, 1 wt% magnesium substituted BCP powders were degraded and precipitation started to be formed with small granules consisting of number of flake-like crystal onto the surface of synthesized powders. On the other hand, in the case of pure BCP powders, the formation of new precipitates was detected after immersion in HBSS for 2 weeks. On the basis of these results, magnesium substituted BCP could be able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. In addition, the retention time to produce the new apatite phase in implantation operation for the BCP powder could be controlled by the amount of magnesium substitution.

In a previous study, an antifungal protein, AFP-J, was purified from tubers of the potato (Solanum tuberosum cv. L Jopung) and by gel filtration and HPLC. In this study, the functional peptide was characterized by partial acid digestion using HCl and HPLC. We obtained three peaks from the AFP-J, the first and third peaks were not active in the tested fungal strain. However, the second peak, which was named Potide-J, was active (MIC; 6.25 mu g/mL) against Candida albicans. The amino acid sequences were analyzed by automated Edman degradation, and the amino acid sequence of Potide-J was determined to be Ala-Val-Cys-Glu-Asn-Asp-Leu-Asn-Cys-Cys. Mass spectrometry showed that its molecular mass was 1083.1 Da. Finally, we confirmed that a disulfide bond was present between Cys(3) and Cys(9) or Cys(10). Using this structure, Potide-J was synthesized via solid-phase methods. In these experiments, only the linear sequence was shown to display strong activity against Candida albicans. These results suggest that Potide-J may be an excellent candidate compound for the development of commercially applicable antibiotic agents.

Hydroxyapatite (HA) ceramics were prepared from the bone ash which is mostly used as animal feeds or raw materials. Dissolving behaviors of the HA in buffered water were investigated and compared with commercial HA for further use as biomaterials. HA ceramics were prepared by soaking the bone ash in 0.1 M of NaOH solution at 80°C for 4 h. The ash was calcined at 800°C for 1 h to completely remove organics, and then sintered at 1200°C for 1 h under moisture protection. The bone ash derived-HA consists of mostly HA and small amounts of α-tricalcium phosphate, calcium oxide phosphate, magnesium oxide and calcium oxide. After polishing the HA ceramics, they were immersed in buffered water at 37°C for 3 and 7 days. We previously found that grain boundaries of synthetic HA were intensively dissolved in buffered water. On the other hand, the bone ash derived-HA shows high stability in liquid environment with immersion time compared with commercial HA.

In situ preparation of silicon (Si) substituted biphasic calcium phosphate (BCP) of hydroxyapatite (HAp)/ β-tricalcium phosphate (β-TCP) were carried out through aqueous co-precipitation method. The concentrations of added silicon were varied with the phosphor in order to obtain constant Ca/(P+Si) ratios of 1.602. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized silicon substituted BCP powders. The characterization revealed that the formation of biphasic mixtures of different HAp/ β-TCP ratios was dependent on the content of silicon. After immersing in Hanks' balanced salt solution (HBSS) for 1 week, 3 wt% silicon substituted BCP powders were degraded and precipitation started to be formed with small granules consisting of number of flake-like crystal onto the surface of synthesized powders. In the case of 1 wt% silicon substituted BCP powders, the degradation behavior was detected after immersion in HBSS for 3 weeks. On the other hand, silicon unsubtituted BCP powders were not degraded even after that duration. On the basis of these results, silicon substituted BCP is able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. This enhanced reactivity resulted in reduction for the stability of the β-TCP structure due to SiO 4 tetrahedral distortion and disorder at the hydroxyl site when silicon incorporates into BCP.

To replace bottom ash for natural sand completely, the mix proportions of bottom ash in concrete was adjusted according to tab density and replacement ratio of polymeric resin/Potland cement(PC) were established. And then testing for slump, setting time, and compressive strength was conducted. According to test results, the compressive strength of concrete using the bottom ash was lower than that of concrete using natural sand (BA0 concrete). But by adjusting the amount of bottom ash in concrete according tab density so that the fine aggregate proportions change 44% to 38%, the compressive strength of concrete using the bottom ash could even be higher than BA0 concrete. And as the polymeric resin content of bottom ash concrete increased, strength would be increased drastically, but proper dispersant should be cooperated with polymeric resin cement with fine bottom ash powders.

To understand the detailed mechanisms of arrhythmia and methods of its treatment, it is necessary to elucidate the mechanisms of formation and breakdown of cardiac beating at a microscopic level by using appropriate in vitro models of cardiac beating. We developed a method for medium-exchange-free culture of rat cardiac myocytes, and carried out long-term recording of the electrical activity of cardiac myocytes from postnatal rats by means of a microelectrode array (MEA) and our new culture method. Figures 6(a) to 6(f) show a series of properties of spontaneous beating (mean beating interval, standard deviation, and coefficient of variation) of cardiac myocytes cultured by a conventional culture method with alternate-day medium exchange [(a) to (c)] and the newly developed “molecular diffusion culture” method [(d) to (f)]. As shown in these figures, the difference in the beating property between individual cultures that is found in conventional cultures [(a) to (c)] is dramatically reduced in the molecular diffusion cultures [(d) to (f)]. These results also indicate that there is a transient period when the mean beating interval, the standard deviation, and the coefficient of variation all increase transiently before the formation of a stable rhythmic fast beat. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(7): 35–42, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10244

Rat superior cervical ganglion (SCG) neurons and the ventricular myocytes (VMs) were cocultured in chambers made of polydimethylsiloxane. The chambers were placed on a microelectrode array (MEA) substrate and connected with a pathway. Twenty-four hours after dissemination of the VMs, neurites of the SCG neurons outgrew through the pathway and reached the VMs. Spontaneous electrical activities of the SCG neurons and the VMs were observed several days after the dissemination. Constant-voltage stimulation (1 V, 1 ms, biphasic square pulses) was applied to the SCG neurons at the frequency of 10 Hz using 32 electrodes. Contraction rate of the VMs increased by 153 ± 110% immediately after the stimulation to the SCG neurons was stopped. Then contraction rate gradually decreased and returned to almost the same rate as before the stimulation 5 min after the stimulation. Propranolol (β-adrenergic receptor antagonist) prevented contraction rate of the VMs from increasing after electrical stimulation to the SCG neurons. These results suggest that neuromuscular junctions were formed between the SCG neurons and the VMs and that this coculture system can be utilized in the research of cell–cell interactions between the sympathetic neurons and the cardiomyocytes. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Bone ash-derived hydroxyapatite (HA) ceramics were prepared by pressureless sintering and hot pressing, and their dissolution behavior was examined in buffered water. HA powder was obtained by soaking bone ash in a 0.1M NaOH solution at 80 °C, followed by calcination at 1000 °C to completely remove the organic material. The crystal structure of the HA powder with a particle size of approximately 1 μm was mainly hydroxyapatite with a minimal amount of α-tricalcium phosphate. To improve densification, the powder was hot-pressed at 1000 °C for 0.5 h under a pressure of 30 MPa in an Ar atmosphere. The sintered density of the hot-pressed HA was 95 % of the theoretical density, which is much higher than the 70% obtained for the pressureless-sintered compact. In the porous HA ceramics obtained by pressureless sintering, dissolution occurred adjacent to the pores rather than in the dense part, which increased the residual porosity. On the other hand, the hot-pressed HA showed grain boundary dissolution followed by particle loosening.

Hydroxyapatite (HA) ceramics derived from tuna bone (THA) was prepared and their mechanical property was investigated with immersion in buffered water. Tuna bones were soaked in 0.1 M of NaOH solution at 80°C for 1 h. After soaking, the bones were calcined at 800°C for 1 h to completely remove organic, and then attritor-milled for 24 h. The powders obtained were cold isostatically pressed and sintered at 1300°C with a dwell time of 1 h. Sintered densities of the THA was about 93%. After polishing, the THA were immersed in buffered water at 37 °C for 3 and 7 days. The THA ceramics consisted of HA and small amount of magnesium oxide. Immersion test revealed that there was no clear evidence of dissolution for the THA which sintered at high temperatures. Vickers hardness test showed that the hardness value of THA ceramics was not changed with immersion time indicating that dense hydroxyapatite from tuna bone was stable in liquid environment.

Geopolymers were prepared by using the dried fly ash from industrial by-product, NaOH as alkaline activator and Na2SiO3 as liquid glass. Calcium carbonate from a clam shell was added to provide attachment and growth of environmental organisms on the geopolymers. We investigated the effects of a shell powder contents on the microstructure and bonding properties of the geopolymers to normal cement. The major chemical compositions of fly ash were Si and Al at the ratio of 2 to 1 in wt%. The shell powder with layer sheet consisted of aragonite phase. As increasing the amount of the shell powder, fly ash was not polymerized and remained spherical. The bonding between geopolymers and normal cement was obtained when 0-15 wt% of the shell powder was added. On the other hand, bonding was not achieved with higher shell contents of 20-25 wt%.

The response of human bone marrow cell to bone ash-derived hydroxyapatite (HA) and tuna bonederived HA powders was compared. HA ceramics were prepared from the commercial bone ash and waste of tuna bone. HA powders were prepared by soaking the bone ash and tuna bone in 0.1M of NaOH solution at 80 °C for 4 hours. Both powders were calcined at 800 °C for 1 hour to completely remove organic and were attritor-milled for 24 hours. The bone ash-derived HA (AHA) and tuna bone-derived HA (THA) ceramics were prepared by cold isostatically pressed and sintered 1200 °C with a dwell time of 1 hour. A human bone cell line MG-63 cells were used to test biocompatibility of AHA and THA ceramics. Cell suspensions in DMEM containing 10% FBS and 1% penicillin-streptomycin were seeded onto 24-well plate containing THA and AHA ceramics. Cell proliferation was evaluated by MTS assay, and cell morphology was observed by SEM.

The sympathetic nervous system is one of the principal sources for regulating cardiovascular functions. Little is known, however, about the network-level interactions between sympathetic neurons and cardiomyocytes. In this study, a semi-separated co-culture system of superior cervical ganglion (SCG) neurons and ventricular myocytes (VMs) was developed by using a polydimethylsyloxane (PDMS) chamber placed on a microelectrode-array (MEA) substrate. Neurites of SCG neurons passed through a conduit of the chamber and reached VMs. Evoked activities of SCG neurons were observed from several electrodes immediately after applying constant-voltage stimulation (1 V, 1 ms, biphasic square pulses) to SCG neurons by using 32 electrodes. Furthermore, this stimulation was applied to SCG neurons at the frequency of 1, 5 and 10 Hz. After applying these three kinds of stimulations, mean minute contraction rate of VMs increased with an increase in the frequency of stimulation. These results suggest that changes in contraction rate of VMs after applying electrical stimulations to SCG neurons depend on frequencies of these stimulations and that the heart-regulating mechanisms as well as that in the body were formed in this co-culture system.

Titanium-based nitride coatings on cutting tools, press molds and dies can be used to prolong their life cycle because of their superior corrosion and oxidation resistance. TiAlN/ZrN and TiCrN/ZrN multilayer coatings were prepared by RF magnetron sputtering, and their microstructural evolution and corrosion resistance during heat treatment were investigated. The TiAlN/ZrN and TiCrN/ZrN multilayer coatings are degraded by heating up to 600 °C with the formation of oxides particles on the surface. During the heat treatment, the TiCrN/ZrN and TiAlN/ZrN multilayer coatings show the lowest corrosion current density and the highest polarization resistance at temperature range of 400–500 °C. Consequently, the TiAlN/ZrN and TiCrN/ZrN multilayer coatings show good corrosion resistance at temperature range of 400–500 °C during heating.

Background: The renin-angiotensin-aldosterone system affects cellular morphology and function in the heart under a variety of pathologic conditions. In the present study the effects of aldosterone on the expression of connexin (Cx) 43 gap junctions in cardiomyocytes were investigated. Methods and Results: Cultured rat ventricular myocytes were exposed to aldosterone for 24 h. The protein and mRNA expression of Cx43 was estimated. Propagation of excitation was visualized by a multiple electrode array system. Treatment of the myocytes with 10-8 mol/L aldosterone resulted in a significant upregulation of Cx43 (by ~1.5-fold in protein and by ~1.2-fold in mRNA). The immunoreactive signal of Cx43 was also increased. Conduction velocity (CV) was increased by ~24%. Treatment of the myocytes with aldosterone at higher concentrations (10-6-10-4 mol/L) caused a significant downregulation of Cx43 protein (by ~0.3-fold) without affecting Cx43 mRNA levels, and decreased the CV by ~23%. The Cx43 upregulation and CV acceleration at 10-8 mol/L aldosterone were prevented by pretreatment with eplerenone, but unaffected by mifepristone. Pretreatment of the myocytes with eplerenone or mifepristone did not prevent the Cx43 downregulation by aldosterone at 10-6-10-4 mol/L. Conclusions: Aldosterone may be involved in arrhythmogenic gap junction remodeling through its dual effects on the expression of Cx43. (Circ J 2009; 73: 1504 - 1512)

A semi-separated co-culture system for spatio-temporal recording of the electrical activities from superior cervical ganglion (SCG) neurons and ventricular myocytes (VMs) was developed by using a handmade “H-shaped” chamber placed on microelectrode arrays (MEA). The chamber was made of polydimethylsyloxane (PDMS) and consisted of two chambers which were connected with a pathway. 16-20 hours after dissemination of SCG neurons into one chamber, the dissociated VMs were disseminated into the other chamber. 4days after dissemination of VMs, SCG neurons and VMs conjugated only at the pathway. Spontaneous electrical activities of SCG neurons and VMs were observed several days after the dissemination of VMs. Constant-voltage stimualtion (1 V, 1 ms, biphasic square pulses) was applied to SCG neurons at the frequency of 10 Hz using 32 electrodes. After applying electrical stimulation to SCG neurons, the contraction rate of VMs in three samples increased by 55±5.6%, 64±8.8%, 280±160%, respectively. This result suggests that neuromuscular junctions were formed between SCG neurons and VMs.

Dissolving behavior of hydroxyapatite (HA) ceramics prepared from bovine bone (BHA) was investigated and compared with synthetic HA. BHA power was obtained by calcining at 800 °C for 1 h to remove organics and then attritor-milling for 24 h. Synthetic HA and BHA powders were prepared by hot-pressing at 1000 °C for 0.5 h under the pressure of 30 MPa in Ar atmosphere. Sintered densities of the synthetic HA and the BHA were about 96% and 95%, respectively. The BHA consisted of mainly HA and small amount of magnesium oxide. Immersion test revealed that there was no clear evidence of dissolution for the BHA, whereas extensive dissolution on the surface of the synthetic HA occurred in buffered water. Accordingly, dense hydroxyapatite from bovine bone was more stable than synthetic HA in liquid environment.

Dissolving behavior of hydroxyapatite (HA) ceramics prepared from bovine bones (BHA) was investigated and compared with artificial HA. BHA and artificial HA were sintered at 1200 °C for 1 h, and they were immersed in distilled water at 37 °C for 3, 7, 14 and 28 days. Detectable peaks in artificial HA were only identical to HA phase, however, BHA consists of mostly HA phase and small amount of MgO. Sintered density of BHA was lower than that of artificial HA. Dissolution of artificial HA was founded after 7 days. The grain boundaries on the surface of artificial HA appeared to initiate dissolution, and grains are pulled out of the artificial HA surface at the end of the immersion period, however, there is no evidence of BHA surface at the end of the immersion period. It was found that HA from bovine bone was more stable than artificial HA in a liquid environment.

Hydroxyapatite (HA) has been of interest in many industrial applications, such as ion exchange, catalysis and biomaterials. Chelating agents have often been used to prepare inorganic powders in the form of sphere, rod, whisker and fiber. In this study, HA whiskers were synthesized directly from typically shaped HA powders by refluxing at 80 and 100 °C for 24 h using ethylenediamine tetraacetic acid (EDTA). 3% or 6% of hydrogen peroxide (H 2 O 2 ) was used to promote precipitation of HA crystals. The pH of the solution was adjusted at 7 or 9 by adding ammonia solution. The higher the H 2 O 2 concentration, pH value and refluxing temperature, the longer and thinner whiskers were formed. The whiskers produced at 100 °C with 6% of H 2 O 2 and pH 9 had the highest aspect ratio of about 50–60 (a length of 3 μm and a width of 0.05 μm).

Titanium-based nitride coatings on cutting tools, press molds and dies can prolong their life cycle because of superior corrosion and oxidation resistance of coatings. In this study, TiAlN/ZrN and TiCrN/ZrN multilayer coatings were prepared by R.F magnetron sputtering, and microstructural evolution and corrosion resistance of the coatings were investigated during heat treatment. The TiAlN/ZrN and TiCrN/ZrN multilayer coatings were degraded by heating up to 600 oC with formation of oxides particles on the surface. During the heat treatment, the TiCrN/ZrN and TiAlN/ZrN multilayer coatings showed the lowest corrosion current density and the highest polarization resistance at temperature range of 400 oC and 500 oC. Consequently, the TiAlN/ZrN and TiCrN/ZrN multilayer coatings showed good corrosion resistance at temperature range of 400°C and 500°C during heating.

Objective To evaluate the protective effect of Ginkgo biloba extract (GBE) on gentamicin (GM)-induced morphological damage of an artificial otoconia. Materials and methods An artificial otoconia powder was placed in a 12-well culture plate containing artificial endolymph. GM (500 μL; 40 mg/mL) was added to the first four wells. GM (500 μL; 40 mg/mL) with GBE (500 μL) was added to the next four wells. PBS (500 μL) was added to the remaining four wells as a control. The levels of nitric oxide (NO) synthesis were determined in the supernatants of each group. Alteration in surface morphology and calcium content were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. Results NO concentration increased in the GM-treated group compared with that in the control group. When the calcite-gelatin composite was treated with GBE, GM-stimulated NO production significantly decreased. The surface of the calcite-gelatin composite exposed to GM showed erosive fissures and had a honeycomb-like appearance. GBE showed a protective effect against dissolution. EDX showed that the calcium content of the GM-treated group significantly decreased. However, the GBE-treated group demonstrated an insignificant change in the calcium concentration compared with the control. Conclusion From these results, we can conclude that GBE may have a protective effect against GM-induced NO production and superficial structural changes.

The reaction-sintered zirconia-alumina and zirconia-spinel ceramics having low firing shrinkage were prepared from ZrO2(Ca-PSZ)/Al and ZrO2(Baddellyite)/MgAl powder mixtures via the attrition milling and the effect of the characteristics of used raw powders was investigated. Flaky Al powders mixed with coarse Ca-PSZ powders was not effectively comminuted due to lower hardness of zirconia powders. So by using the alumina ball media or coarse Al2O3 powders rather than Al, the milling efficiency could be much more increased. When fused Ca-PSZ powder was reaction-sintered with Al at 1550 for 3 hours, the reaction-sintering and densification were somewhat difficult because the Ca-PSZ/Al powder mixture was not effectively comminuted. And the Ca ion in Ca-PSZ grains diffused into alumina grains during sintering so that the unstabilization of Ca-PSZ body was occurred which gave the cracks in the specimens. But when MgAl alloy powder was added to monoclinic zirconia, Mg and Al became to oxide at first and subsequently converted to spinel(MgAl2O4) during heating and finally unreacted MgO seemed to stabilize the zirconia. The oxides which formed at the oxidation process would have very fine grain size so that the reaction sintering was more effective to densification and homogeneous microstructure. The mechanical properties of reaction-sintered stabilized zirconia/spinel composite were better than only MgO stabilized zirconia. Sintering behavior in reaction and mechanical properties of sintered body were examined, with emphasis on the relations between spinel formation and mechanical properties.

Dissolution of calcium phosphate powders with different compositions in simulated body fluid was investigated. Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) powders were synthesized by a precipitation method and by controlling pH of the solution. Biphasic calcium phosphate (BCP) powders were prepared by mixing the HA and β-TCP powders with ratio of 80:20 and 60:40 in weight % in a planetary mill for 4 h. For dissolution test, 0.5g of each β-TCP, HA and BCP powders were immersed in 50 ml of SBF at 37°C for 3-28 days. HA powders with stoichiometric composition showed no significant morphological change regardless of the immersion time. β-TCP powders were not dissolved in SBF in spite of its high solubility. The surface of BCP powders became rough due to dissolution with increasing immersion time. This surface dissolution gradually extended into the core region of the particles resulting in disintegration of the dense particle into fine crystallites. It may be caused that the milling process during preparation of BCP powders may induce stress concentration or formation of dislocation on the surface of particles.

Calcium phosphate ceramics (CPC) have been attractively used in different areas of biomedical applications, such as substances of artificial hard tissue replacement implants, drug delivery system due to their biocompatibility and bioactivity. In this work, three calcium phosphate powders between Ca/P molar ratio 1.50-1.67 were synthesized by aqueous precipitation method, using the mixture of Ca(NO3)2·4H2O and H3PO4 solutions to ammonia solution. During the precipitation reaction, Ca/P molar ratio was adjusted by controlling pH of the solution between 8.0 and 10.5 by the addition of ammonium hydroxide solution. All powders were treated at 800 oC for 2 hrs. The calcined powders were immersed in pH 7.4 distilled water at 37°C for 3 and 7 days. Decomposition and related dissolution with the various Ca/P ratios were investigated by XRD, FTIR, and TEM observation.