Papers by Author: In Seop Lee

Abstract: Tissue-engineering must be either manufactured aseptically or sterilized after processing. To extend protection of medical devices against microbial contamination, various sterilization methods have been suggested. Hydrogen peroxide gas plasma sterilization has been applied in hospitals worldwide for almost a decade. In this study, we investigated the sterilization efficacy of hydrogen peroxide gas plasma sterilizer with porous polyurethane sample. The result is suggested that hydrogen peroxide gas plasma can be applicable to the sterilization of polymer scaffold for tissue engineering materials.

Abstract: Various composition of calcium-silicate thinfilms were deposited to the thickness of 1μm by electron-beam deposition. The composition was varied by changing the composition of source. The Si concentration of thinfilm was ranged from 25 at% to 85 at%, evaluated by EDS. The specimens were immersed into PBS solution at 37 °C. Changes of the morphology and calcium phosphate formation on the specimens were examined by SEM. If the concentration of calcium is high, the calcium phosphate was quickly formed on the specimen. However, the calcium phosphate formed on the high calcium oxide concentration exhibited very poor adhesion onto the substrate. There is a range of appropriate calcium oxide concentration to use as a surface modification method for dental or orthopedic implants.

Abstract: The aim of this study is to evaluate the effects of coating implants with hydroxyapatite (HA) by an ion beam-assisted deposition (IBAD) method and to compare them with implants prepared with machined and anodized surfaces. Twenty-four implants in this study were divided into three groups; machined, anodized, anodized plus IBAD surface implants. Implant stability and osseointegration were assessed by resonance frequency analysis (RFA) and histologic analysis. We can conclude that implants coated by HA by IBAD demonstrate characteristics of contact osteogenesis, but the research design does not permit conclusions regarding long-term treatment outcome with implants. Further studies are needed.

Abstract: The surface morphology of commercially pure titanium was investigated with varying electrical waveform. Controlling of electrical pulse width is effective to change pore sizes. Longer electrical pulse width was induced, larger size of pores were generated.

Abstract: A part of the titanium dental implant surface, which will meet connective tissue after being inserted in mandibular bone, was coated with calcium phosphate by ion beam assisted deposition (IBAD). Twenty-four implants of coated and uncoated group were randomly placed in mandibles after 3 months of premolars extraction in beagle dogs. All the implants were firmly anchored in the bone and had no clinical signs of peri-implant inflammation after 3-month insertion. The probing depth in calcium phosphate coated group is 1.9±0.2 mm, less than in control group (2.1±0.2 mm) (p<0.05). Most of the probing sites tended to bleed upon probing in two groups. It might indicate that the calcium phosphate coating has the potential to promote soft tissue integration.

Abstract: Implantable neural prostheses form hybrid interfaces with biological constructs, and the application of electrical fields can restore functions of patients with neurological damages. The various stoichiometric compositions of iridium oxide were synthesized using reactive magnetron sputtering. The charge injection behavior of iridium oxide deposited with an O2/Ar ratio of 0.5 was similar to pure Ir. The charge density of iridium oxide increased with increasing O2/Ar ratio, and increasing thickness of iridium oxide.

Abstract: In this study, human dermal fibroblast behaviors onto non-porous PLGA (75:25) films immobilized with 1, 10 and 100 µg/ml collagen (CN) or fibronectin (FN) were investigated according to different cell-seeding densities (1,000, 10,000 and 100,000 cells/ml). Cell attachment and proliferation were assessed using water soluble tetrazolium salt. The results indicated that 1 µg/ml of FN-immobilized PLGA film demonstrated significantly (p < 0.05) superior cellular attachment to the intact PLGA film after 4 hr of incubation. Moreover, the number of attached cells was shown to be directly proportional to that of initially seeded cells. After 48 hr, the cells showed significantly (p < 0.05) higher proliferation onto 1 or 10 µg/ml of FN-immobilized PLGA films than onto other PLGA films, regardless of the initial cell-seeding density. In terms of CN-immobilization, cell proliferation was appreciably increased but it was relatively lower than FN-immobilization. These results suggested that ECM-immobilization can enhance the cell affinity of hydrophobic scaffolds and be used to potential applications for tissue engineering by supporting cell growth.

Abstract: 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.

Abstract: The hygrothermal degradation of glass fiber/nylon composite was investigated after aged at 25°C, 50°C, 75°C and 100°C up to 1 month of total exposure in aqueous solution. The effects of moisture absorption and thermal aging on mechanical properties are compared as functions of temperature, fiber volume and concentration of sodium chloride. The amount of water absorption increases when the aging temperature is increased and the concentration of NaCl is lowered. In general, the mechanical properties decrease with amount of water absorption. The degradation rate of various mechanical properties is different depending on the temperature, fiber volume and the concentration of NaCl. The diffusion mechanisms of water in short-fiber reinforced nylon are discussed as functions of fiber volume, molding conditions and concentration of sodium chloride.