Sung-Min Chung

Enhanced bone forming ability of SLA-treated Ti coated with a calcium phosphate thin film formed by e-beam evaporation

With an electron-beam evaporation process, a calcium phosphate (Ca-P) thin film of approximately 500 nm thick was deposited on sand blasted with large grits and acid etched (SLA) Ti without changing the typical morphology of the SLA surface. Dissolution behavior was investigated by measuring the amount of dissolved phosphate ions with ion chromatography after immersing the SLA Ti sample coated with a Ca-P film in 1 ml de-ionized water maintained at 37 degrees C for different periods of soaking time, and the surface morphology was observed with field emission scanning electron microscopy. The amount of phosphate ions increased quickly right after immersion but began to decrease after 2 days of immersion by redeposition with Ca ions as apatite, and the amount of biomimetic apatite increased with the extended soaking time. The Saos-2 cell was more attached on the coated surface, and the in vivo evaluation was that the Ca-P deposited SLA implant greatly improved the new bone formation ability.

Characterizations of the TiO(2-x) films synthesized by e-beam evaporation for endovascular applications.

Different chemical states of titanium oxide films were deposited on commercially pure Ti (CP Ti) by electron-beam evaporation at different oxygen flow rates to examine a possibility of their applications to endovascular stents. The surface morphology, chemical composition and crystal structure of the obtained titanium oxide films were analyzed by FE-SEM, XPS and XRD, respectively. As a function of the deposition parameters employed, the obtained titanium oxide films demonstrated different mixtures of anatase phase, Ti2O3 and TiO. By the formation of titanium oxide film on the CP Ti plate, the contact angle was decreased and the cellular activity of porcine aortic smooth muscle cells was increased. Post-deposition annealing was also found to be an important factor to achieve advantageous biocompatibility. When haemocompatibility was investigated by observing adhesion of blood platelets from platelet-rich plasma, less platelet adhesion was observed on titanium oxide films. These results indicated that titanium oxide film synthesized by e-beam evaporation could be applicable to coronary stents.

Silk fibroin membrane used for guided bone tissue regeneration

With the aim to develop a novel membrane with an appropriate mechanical property and degradation rate for guided bone tissue regeneration, lyophilized and densified silk fibroin membrane was fabricated and its mechanical behavior as well as biodegradation property were investigated. The osteoconductive potency of the silk fibroin membranes were evaluated in a defect rabbit calvarial model. Silk fibroin membrane showed the modulated biodegradable and mechanical properties via ethanol treatment with different concentration. The membrane could prevent soft tissue invasion from normal tissue healing, and the amounts of new bone and defect closure with silk fibroin membrane were similar to those of commercially available collagen membrane.

Effects of calcium phosphate coating to SLA surface implants by the ion-beam-assisted deposition method on self-contained coronal defect healing in dogs.

The aim of this study was to evaluate the healing of self-contained coronal defects on a sand-blasted, large-grit, acid-etched (SLA) surface implant, which had a calcium phosphate (CaP) coating applied by ion-beam-assisted deposition (IBAD). We also evaluated the effect of heating the coating to different temperatures. The CaP-coated SLA implants exhibited a slightly larger bone healing capacity in the self-contained coronal defect than SLA implants, indicating that combining SLA surface implants and a CaP coating by the IBAD method had synergistic effects on bone healing. There was no difference in the healing capacity between 350 degrees C and 450 degrees C heat treatment of the coating layer.

Characterization of a silver-incorporated calcium phosphate film by RBS and its antimicrobial effects

A thin calcium phosphate film was synthesized on both commercially pure Ti and Si wafers by electron beam evaporation of hydroxyapatite as an evaporant with simultaneous Ar ion beam bombardments. Silver was introduced into an ion-beam-assisted deposition of a calcium phosphate thin film for antimicrobial effect. The amount of incorporated silver ions was controlled by immersing calcium-phosphate-coated samples in different AgNO(3) concentrations, and Rutherford backscattering spectrometry (RBS) was employed to measure the amounts of substituted silver. The higher concentration of silver in the calcium phosphate film was more effective in reducing the bacteria of Escherichia coli ATCC 8739 and Streptococcus mutans OMZ 65 on contact with respect to controls.

Biomimetic apatite formed on cobalt-chromium alloy: A polymer-free carrier for drug eluting stent

In this study, sirolimus (SRL) was loaded within biomimetic apatite formed on cobalt-chromium (Co-Cr) alloy, which has been reported for the first time, to inhibit the in-stent restenosis. Two different groups of loading SRL within biomimetic apatite were prepared: Group A (mono-layer of apatite/SRL) and Group B (bi-layer of apatite/SRL). Group A and Group B showed the biphasic pattern of SRL release up to 40 and 90days, respectively. The attachment of human artery smooth muscle cell (HASMC) for both Group A and Group B was significantly inhibited, and proliferation dramatically decreased with the release of SRL. Noteworthily, biomimetic apatite alone also suppressed the SMC proliferation. The porous biomimetic apatite uniformly covered Co-Cr stent without crack or webbings. After balloon expansion, the integrity of biomimetic apatite was sufficient to resist delamination or destruction. Thus, this study demonstrated that biomimetic apatite is a promising drug carrier for potential use in stents.

Evaluation of Poly(Lactic-Co-Glycolic Acid) (65/35) Treated by Dielectric Barrier Discharge in Atmospheric Pressure

The surface properties of scaffolds are important since cell affinity is the most crucial factor to be concerned when the biodegradable polymeric material is utilized as a scaffold in tissue engineering. The surface of biodegradable non-porous poly (lactic-co-glycolic acid) (PLGA) scaffolds were treated by atmospheric pressure dielectric barrier discharge (APDBD). The wetting angle of APDBD treated PLGA were decreased from the untreated PLGA of 73° to 42°. FTIR-ATR analyses showed hydroxyl groups were not detected regardless of treated condition, but the intensities of both ether groups and carbonyl groups were increased with treatment time and oxygen flow rate. Treatment time and oxygen flux are equally effective to make the PLGA surface more hydrophilic.