Electrochemical Deposition of Hydroxyapatite Substituted with Magnesium and Strontium on Ti-6Al-4V Alloy.

In the present study, electrochemical deposition of hydroxyapatite substituted with magnesium and strontium on Ti-6Al-4V alloy have investigated. Mg and Sr-doped HAp was coated using subsequently pulsed electrochemical deposition process at 85 °C in the solution contained Ca, Mg, Sr, and P ion. The morphology of Mg/Sr-HAp formed on implant was investigated using scanning electron microscopy and X-ray diffraction. HAp grain size and XRD intensity decreased with Mg2+ and Sr2+ ions. The initial current density was changed with addition of Mg and Sr ion concentration when the constant voltage was applied to specimens. The morphologies and phase of HAp coated layers were affected by the Mg and Sr ion concentration. Results suggest that Mg/Sr-HAp layer formed on Ti can be a potential candidate for dental materials application.

Thymosin ß4 Reduces H2O2 Induced Oxidative Stress in MC3T3-E1 Cells on Titanium Surface.

Thymosin ß4 (Tß4) is known to inhibit an inflammatory response and to increase the survival of osteoblasts on titanium (Ti) surfaces. Ti is the most widely used graft material in dentistry; however, an inflammatory response induced following implant placement results in the generation of reactive oxygen species (ROS). The oxidative stress from the production of ROS such as nitric oxide (NO) and hydrogen peroxide (H2O2) can damage surrounding cells, resulting in implant failure by decreasing cell viability. Thus, the aim of this study was to determine the biological effects of Tß4 on the oxidative stress induced to MC3T3-E1 preosteoblasts on the Ti surface. Based on an MTT assay and bromodeoxyuridine immunofluorescence staining, Tß4 was found to increase the proliferation of the H2O2-exposed MC3T3-E1 cells on Ti discs. Reverse transcription-polymerase chain reaction and western blot analyses showed that Tß4 decreased the mRNA and protein expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in H2O2-exposed MC3T3-E1 cells on the Ti discs. Tß4 inhibited the synthesis of intracellular ROS and the secretion of NO and prostaglandin E2 (PGE2) from H2O2-exposed MC3T3-E1 cells on the Ti discs. In conclusion, Tß4 inhibits H2O2-induced iNOS and COX-2 expression with a decrease in ROS, NO, and PGE2 synthesis, which leads to improved cell survival with low cytotoxicity under an oxidative stress condition in MC3T3-E1 cells on the Ti surface. This suggests that Tß4 may be a crucial molecule to reduce oxidative stress-induced cell damage or hypoxia, leading to promoted osseointegration on the Ti surface during implant placement.

Engineered microstructure granules for tailored drug release rate.

Biomaterials developed for controlled drug delivery have demonstrated excellent results in the present study. A biomaterial prepared using hydroxyapatite (HAp) was shown to have a hollow structure with the presence of interconnected pores to house drug carriers. The poly(lactic-co-glycolic acid) particles were used as drug carriers loaded with dexamethasone, a corticosteroid that is known to promote osteoinduction. The surface of the drug carriers was modified using polyethyleneimine, and then conjugated to the surface of HAp granules. The hollow HAp granules had drug carriers on both their inner and outer surfaces and showed a controlled drug release rate that was comparable to that of granules containing drug carriers on their outer surface alone. The pores were designed for insertion of drug carriers and preosteoblasts. Consequently, the biomaterials influenced cellular behavior by first promoting cell proliferation and then inducing early stage osteogenic differentiation. The effects of controlled release rate were evidenced for up to two weeks after cell seeding, resulting in an increase of osteogenic differentiation. In summary, drug carriers loaded onto hollow HAp granules were shown to be suitable for patients who require replacement of missing bone for repair of bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly.

O2/Ar Plasma Treatment for Enhancing the Biocompatibility of Hydroxyapatite Nanopowder and Polycaprolactone Composite Film.

In this study we performed O2/Ar plasma treatment to remove the polycaprolactone on hydroxyapatite nanopowder and polycaprolactone (HAp-NP/PCL) composite film. After plasma ashing, the HAp-NP was exposed on the composite film. The 25 wt% HAp-NP/PCL treated with plasma showed the hydrophilic surface property with reducing the aging effect. The MTT and ALP results indicated that the plasma etching increased the biocompatibility of HAp-NP/PCL composite film. The present simple plasma etching technique can be applicable in a development of biomaterials.

Characteristics of Plasma Treated Electrospun Polycaprolactone (PCL) Nanofiber Scaffold for Bone Tissue Engineering.

Polycaprolactone (PCL) nanofibers (PCL-NF) with uniform fibrous structure were fabricated by electrospinning. However, PCL-NF has hydrophobic surface, lacks functional groups and hence it is not a good substrate for cell adhesion. To improve the cell adhesion, PCL-NF surfaces were modified by low pressure RF discharge plasma treatment using monomer such as acrylic acid or oxygen gas. The plasma treated PCL-NFs improved the wettability and cell proliferation.

Oxygen and Nitrogen Gas Plasma Surface Treatments on Titanium for Initial Adhesion and Proliferation of Preosteoblast Cells.

In this study, titanium (Ti) surface was treated through the use of oxygen and nitrogen plasma for improving the initial adhesion and proliferation of preosteoblast cells. The plasma treated Ti surface demonstrated hydrophilic surface property and promoted initial adhesion and proliferation of preosteoblast cells.

Plasma Polymerization of 1,2-Diaminocyclohexane for Covalent Bonding of Bone Morphogenic Protein-2 on Titanium Surface.

Among the bone morphogenic protein (BMP) family members, BMP-2 is a potent osteoinductive factor that plays key roles during bone formation. In this study, plasma polymerization of 1,2-diaminocyclohexane (DACH) was performed to immobilize the BMP-2 on Ti surface. The plasma polymerization of DACH was carried out at a discharge power of 60 W and 100 W under a pressure of 10 mTorr for 90 sec. The BMP-2 was successfully immobilized on the DACH plasma treated Ti surface. The BMP-2 immobilized Ti surface showed the excellent cell differentiation. The results indicate that the DACH plasma polymerized Ti surface has a potential for immobilization of biomolecules in bone tissue engineering.

In Vitro Antibacterial Activity of Nano Silver Ion Substituted Poly Acrylic Acid Films on Titanium by Plasma Polymerization.

Antibacterial activity of oral pathogens such as Streptococcus mutans, Streptococcus sobrinus when silver ion immobilized on commercially pure (CP) titanium (Ti) surface was investigated in this study. Plasma-polymerized acrylic acid to have carboxyl group was deposited on CP-Ti surface and then ion-exchanged with Ag+ ions in 0.1 N AgNO3. In anti-adherent experiment, antibacterial activity was tested using broth culture methods. The biofilm formation assay was performed using semi-defined biofilm medium with sucrose. The silver coated CP-Ti completely inhibited the growth of S. mutans and S. sobrinus. In addition, the biofilm formation was significantly inhibited in silver-coated CP-Ti group.

Secretory Leukocyte Protease Inhibitor (SLPI) Increases Focal Adhesion in MC3T3 Osteoblast on Titanium Surface.

An appropriate interaction between implanted materials and the surrounding tissue is essential for successful implantation. Titanium (Ti) and some of its alloys have been used in dentistry and orthopedics as a substitutive material for hard tissue, such as teeth or natural bone. Nevertheless, metal ions released from titanium and alloy implants have adverse biological effects on biological tissues or cells. Secretory leukocyte protease inhibitor (SLPI) promotes cell migration, proliferation and wound healing. FAK and ERK1/2 signaling regulate cell adhesion and proliferation for cell survival. This study evaluated the potential of SLPI as a molecule to increase the cell adhesion on the Ti surface. Compared with the untreated cells, SLPI increased the adhesion of MC3T3-E1 cells to Ti discs, formation of actin stress fibers, paxillin expression and the phosphorylation of FAK. Moreover, SLPI enhanced the level of Grb2 and Ras expression and ERK1/2 phosphorylation in the MC3T3-E1 cells on Ti discs. These results suggest that SLPI can increase the interaction between the implanted Ti material and surrounding bone in orthodontic and dental surgery, making an effective nanomolecule for successful implantation.

Formation of nano-phase hydroxyapatite film on TiO2 nano-network.

Nano- and micro-phase HA film formed on TiO2 nano-network surface by simple electrochemical treatment. The range of lateral pore size of the network specimen was about 10-120 nm on Ti surface by anodized in 5 M NaOH solution at 0.3 A for 10 min. Nano-network TiO2 surface were formed by this anodization step which acted as templates and anchorage for growth of the HA during subsequent pulsed electrochemical deposition process at 85 degrees C. The phase and morphologies of deposits HA were influenced by the electrolyte concentration. The nano needle-like precipitates formed under low SBF concentration were identified to be HA crystals orientated parallel to the c-axis direction. Increasing electrolyte concentration, needle-like deposits transferred to the plate-like and micro plate like precipitates in the case of high SBF concentration.

Corrosion behavior of nanotubular oxide on the Ti-29Nb-xZr alloy.

This work reports the corrosion behavior of nanotubular oxide layers on Ti-29Nb-xZr alloys with different compositions by anodization in 1 M H3PO4 + 0.8 wt% NaF. Depending on the alloy composition, nanoporous or highly ordered nanotube structures can be formed. The nanotube oxides on the Ti-29Nb-xZr alloy showed lower corrosion current density compared to non-treated sample.

Nanotube morphology and corrosion resistance of a low rigidity quaternary titanium alloy for biomedical applications.

Highly ordered nanotube oxide layers were developed on low rigidity quaternary beta-type Ti-35Nb-5Ta-7Zr alloy by controlled anodic oxidation in electrolyte containing 1 M H3PO4 and 0.5 wt% NaF at room temperature. The diameters of the nanotubes formed were in the range of 30 to 80 nm. Electrochemical corrosion behavior of the nanotubular alloy was studied in Ringer's solution at 37 +/- 1 degrees C using potentiodynamic polarization and AC Impedance. The result of the study showed that nanotube formation on the surface affect the passivation behavior of the quaternary alloy significantly. However the corrosion current density was considerably higher for the nanotubular alloy.

Cordyceps militaris induces the IL-18 expression via its promoter activation for IFN-gamma production.

ETHNOPHARMACOLOGICAL RELEVANCE: Cordyceps militaris, one of traditional herbal ingredient in oriental medicine, has been known to promote anticancer and immunomodulatory activities in vitro and in vivo. However, the biological mechanism of anticancer activity has been unknown. OBJECTIVE: To investigate the effect of Cordyceps militaris extract on expression of interferon gamma (IFN-gamma) through interlukin-18 (IL-18) induction and its biological mechanism in vitro and in vivo. MATERIALS AND METHODS: Mice were administrated orally with solution extracted from Cordyceps militaris. The transcription level of IL-18 and IFN-gamma production were measured by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. RAW 264.7 cells were transiently transfected with pCATp1 and pCATp2 for IL-18 promoter functional analysis. RESULTS: Cordyceps militaris extracts treatment significantly induced level of IL-18 transcription in mouse brain and liver and enhanced IL-18 transcription level and activated the IFN-gamma production in RAW 264.7 cells. Furthermore, Cordyceps militaris extract led to increase the activity of pCATp1 construct containing the 5' franking region of IL-18 promoter in RAW 264.7 cells. CONCLUSION: Cordyceps militaris extract induced IL-18 mRNA level via enhancing of P1 promoter region result in activation of IFN-gamma production, indicating its potential as an immune activator or anticancer drug.

Bone cement with a modified polyphosphate network structure stimulates hard tissue regeneration.

In this study, a calcium polyphosphate cement (CpPC) consisting of basic components was investigated to assess its potential for hard tissue regeneration. The added basic components for improving the structural stability, which controlled the setting time, where the setting reaction resulted in the formation of amorphous structure with a re-constructed polyphosphate. Moreover, the characteristics were controlled by the composition, which determined the polyphosphate structure. CpPC exhibited outstanding dissolution rate compared with the common biodegradable cement, brushite cement (2.5 times). Despite high amounts of dissolution products, no significant cytotoxicity ensued. Induction of calcification in MG-63 cells treated with CpPC, the level of calcification increased with increasing CpPC dissolution rate. Induced calcification was observed also in CpPC-treated ST2 cells, in contrast with MG-63 and ST2 treated with brushite cement, for which no calcification was observed. In vivo tests using a rat calvarial defect model showed that resorbed CpPC resulted in favorable host responses and promoted bone formation. Additionally, there was a significant increase in defect closure, and new bone formation progressed from CpPC mid-sites as well as defect margins. From these results, CpPC exhibits significant potential as biodegradable bone substitute for bone regeneration.

Bone Tissue Engineering by Using Calcium Phosphate Glass Scaffolds and the Avidin-Biotin Binding System.

Highly porous and interconnected scaffolds were fabricated using calcium phosphate glass (CPG) for bone tissue engineering. An avidin-biotin binding system was used to improve osteoblast-like cell adhesion to the scaffold. The scaffolds had open macro- and micro-scale pores, and continuous struts without cracks or defects. Scaffolds prepared using a mixture (amorphous and crystalline CPG) were stronger than amorphous group and crystalline group. Cell adhesion assays showed that more cells adhered, with increasing cell seeding efficiency to the avidin-adsorbed scaffolds, and that cell attachment to the highly porous scaffolds significantly differed between avidin-adsorbed scaffolds and other scaffolds. Proliferation was also significantly higher for avidin-adsorbed scaffolds. Osteoblastic differentiation of MG-63 cells was observed at 3 days, and MG-63 cells in direct contact with avidin-adsorbed scaffolds were positive for type I collagen, osteopontin, and alkaline phosphatase gene expression. Osteocalcin expression was observed in the avidin-adsorbed scaffolds at 7 days, indicating that cell differentiation in avidin-adsorbed scaffolds occurred faster than the other scaffolds. Thus, these CPG scaffolds have excellent biological properties suitable for use in bone tissue engineering.

Expression and functional characterization of the system L amino acid transporter in KB human oral epidermoid carcinoma cells.

We have examined the expression and function of system l amino acid transporter in KB human oral epidermoid carcinoma cells. The KB cells express l-type amino acid transporter 1 (LAT1) in plasma membrane, but not l-type amino acid transporter 2 (LAT2). The [14C]l-leucine uptake by KB cells is inhibited by system l selective inhibitor BCH. The majority of [14C]l-leucine uptake is, therefore, mediated by LAT1. These results suggest that the transport of neutral amino acids including several essential amino acids into the KB cells mediated by LAT1 and the specific inhibition of LAT1 in oral cancer cells will be a new rationale for anti-cancer therapy.

Antimicrobial effect of Korean propolis against the mutans streptococci isolated from Korean.

The aim of this study was to determine the optimal concentration of Korean propolis against clinical isolates of mutans streptococci (MS) from Koreans. The antimicrobial activity was evaluated using the minimum inhibitory concentration (MIC) and time-kill curves against mutans streptococci. The MIC(90) values of propolis for MS were 35 µg/ml. Propolis had a bacteriostatic effect on Streptococcus mutans ATCC 25175(T) and bactericidal effects on Streptococcus sobrinus ATCC 33478(T) at > 2 × MIC (70 µg/ml). These results suggest that the propolis can be used in the development of oral hygiene products for the prevention of dental caries.

Differential expression of system L amino acid transporters during wound healing process in the skin of young and old rats.

UNLABELLED: In order to elucidate the role of the system L-type amino acid transporters (LATs) in the wound healing process of aged and young subjects, we investigated the expression of LAT1, LAT2 and their subunit 4F2hc in the skin healing process after artificial wounds of dorsal skin in the young and old rats. METHODS: The 1 cm full-thickness incisional wounds were made through the skin and panniculus carnosus muscle. The wounds were harvested at days 1, 3, 5 and 7 post-wounding, the experimental controls were harvested the skin of rat without wounds and the various analyses were performed. RESULTS: In young rats, gradually and noticeable wound healing was detected, however, in old rats, wound healing was found to be greatly delayed. In young rats, the expression of LAT1 was increased rapidly on the day 1 after wound induction, on the other hand, in old rats, the expression of LAT1 after wound induction was not different from the control group. In young rats, the expression of LAT2 after the induction of wound was not different from the control group, however in old rats, the expression of LAT2 on the day 1 of wound induction was rapidly elevated. CONCLUSION: These results suggest that the LAT1 and LAT2 increase in the wound healing process after cell injury in young and old rats, respectively.