Key Engineering Materials Vols. 342-343

Abstract: Dynamic stabilization of the lumbar spine has gained increasingly popularity. These nonfusion systems are alleged to maintain or restore the intradiscal pressure to magnitudes of the intact spine and have little negative effect on the adjacent segments to the stabilized one. Compliant Nitinol alloy (Ni-Ti) has been used in the manufacture of the rods of the dynamic stabilization systems. In this study, we investigated a dynamic stabilization system with its coiled rods made of Nitinol alloy. Four porcine lumbar spines (T12-L6) were prepared: intact, fixed by a conventional rigid fixation system, fixed by a dynamic stabilization system with 2-coiled rods, fixed by a dynamic stabilization system with 3-coiled rods. Intradiscal pressures were measured at all levels before and after insertion of the implant. Our results show that the rigid stabilization system resulted in great changes of disc pressure in flexion and extension regardless of spinal levels. However, Intradiscal pressures (IDPs) remained relatively unchanged in models fixed by the dynamic stabilization systems. Changes in intradiscal pressure can lead to altered metabolism within the disc, with potential long-term disc degeneration. These results suggest that the dynamic stabilization systems are superior over traditional fusion implants in maintaining the intradiscal pressure to the intact level at surgical level and adjacent level and can therefore be considered as an alternative method to fusion surgery in these indications while the intradical pressure is preserved.

Abstract: To analyze the importance of bone quality, we studied 21 primary compressive trabecular system by micro-computed tomography(micro-CT), finite element analysis and destructive mechanical test. Significant correlations were found between histomorphometry and biomechanical parameters. The results indicate that the bone quality of primary compressive trabecular system is determined more by its combined micro-structural parameters (histomorphometry) and biomechanical parameters than histomorphometry only. Assessment of trabecular bone by finite element analysis may become important not only for assessment of bone quality but also for prediction of bone fracture risk of bone degeneration.

Abstract: New medicines for treatment of osteoporotic bones have developed. In the previous studies, there were lots of pre-clinical experiments on animals to analyze the virtue of new medicine. However, the previous methods sacrificed a number of animals. They induced lots of expenses and ethical problems. In the present study, to investigate the effect of a medicine for osteoporosis by using in-vivo micro computed tomography (In-vivo Micro-CT, skyscan 1076, skyscan, Belgium) and micro finite element (*FE) analysis, morphological and mechanical characteristic changes of rat bone were detected and tracked. The 8 female Sprague-Dawley rats, used in the experiment, were randomized into 3 groups (Control, Sham and Risedronate group). The Risedronate (actonel, 0.58mg/Kg and 5days/week) for 8 weeks was administered in RIS group. The 4th lumbar vertebrae of rats were scanned by In-vivo Micro-CT with 35*m at week 0 (just before dose) and week 8 (after dose). Three-dimensional (3D) structural parameters were calculated. Simulated compression tests of 3D FE models were carried out to investigate the mechanical characteristics in the whole vertebral bone model of the 4th lumbar vertebra. The change rate of quantity and structure in Risedronate (RIS) group was smaller than that of control (CON) group. The change rate of structural modulus in RIS group was also smaller than that of CON group. This result shows the virtue of risedronate quantitatively as well as qualitatively. The study introduced the improved noninvasive biomechanical evaluation method, combined with In-vivo Micro-CT and *FE analysis, which was more effective and useful than the previous pre-clinical experiments.

Abstract: The emulsion stabilizing potential of chitosans was compared in the presence of organic additives. The 4 types suspension of 0.1 wt% of chitosan flocculant were obtained by mixing of chitosan colloidal dispersion with three kinds of additives; sorbic acid, benzoic acid and dibutylhydroxytoluene (BHT). The viscosity of emulsion revealed the following order of stabilizing potentials; sorbic acid > benzoic acid > BHT. As a bio-adsorbent for the treatment of biomedical wastewater, the results were capable of adsorbing more than 30% of pure chitosan. The chitosan emulsions represented that the removal efficiency were increased by COD 59.2%, BOD 70.1%, Zn 77.1%, Cu 93.7%, E. coli 99.4%. As a result of this investigation, it is remarked that the high stabilizing potential of chitosan solution is explained by higher adsorption efficiency with organics, heavy metals and microorganism, and that the effectiveness of chitosan solution for coagulating biomedical wastewater suspension could be improved due to stabilization of the viscosity in the presence of organic additives.

Abstract: As a natural biomaterial, collagen especially pepsin-solubilized collagen (type I) has been used widely in biomedical fields due to its excellent biocompatibility. In this preliminary study, we investigate the effect of some inorganic ions which are frequently utilized in the preparation of collagen on the morphology and crystallinity of fibrils. The scanning electron microscope and x-ray diffraction were applied to analyze the morphology and the crystallization of the reconstituted collagen fibrils, respectively. Although further studies are needed, these initial results indicate that by controlling the self-assembly conditions of collagen molecules, we may achieve the desired properties of fibrillar collagen products.

Abstract: To use nanobiosensors as diagnostic devices, they should be evaluated and approved as medical devices before marketing. This study was performed to establish appropriate evaluation guidelines that provide how to verify the safety and effectiveness of a novel nanobiosensor as a medical device. We prepared an enzymeless glucose sensor with nanoporous platinum electrode to evaluate performance and stability by comparing it with a commercial enzyme-based glucose sensor. Through these evaluation studies, we developed guidelines, and the guidelines consist of five parts: evaluation of analytical performance, clinical performance, safety, stability, and design and quality control systems. Analytical and clinical performance of nanobiosensors should be evaluated by accuracy, sensitivity, reproducibility, cut-off value, and other specific performance characteristics. Also, electric, mechanical, and biological safety should be evaluated. With the performance and safety, validation of storing conditions and shelf life should be established with evaluation and characterization of nano-structured parts for stability evaluation. Then, design and quality control systems should be evaluated in the aspect of quality requirements, material, manufacturing process, and final product. These guidelines will be helpful for facilitating the commercialization of the safe, effective, and novel diagnostic nanobiosensors into market place.

Abstract: The purpose of this study was to investigate the remineralization effect of Galla Rhois and Psoralea corylifolia extracts with sodium fluoride (NaF), and interaction between the herbal extracts and NaF in dentifrice using the microbiological pH cycling model on artificial caries enamel. For the analysis, Surface hardness score of the enamel lesion on bovine teeth was measured, before and after the microbiological pH cycling sequences for 15 days. It showed that fluoride group was more higher surface hardness score than non fluoride group, and there were no significant differences among test dentifrices in each group. Thus, it is suggested that Galla Rhois and Psoralea corylifolia extracts with NaF have the remineralization effect on tooth surface. And there was no antagonistic interaction between those herbal extarcts and NaF in dentifrice.

Abstract: The main objective of this study was to manufacture an oral rinse using the natural antibacterial agent (phytosphingosine, Doosan, Korea) for the prevention of periodontal disease and dental caries. Phytosphingosine is known to inhibit the growth of bacterial strains and induce apoptotic cell death in human cancer lines. In this study, antibacterial activity and cytotoxicity of oral rinses were performed with an experimental group containing phytosphingosine(PS) in vitro. Control groups consist of two Korean products and two American products containing chlorhexidine and cetylpyridinium chloride, respectively. There was no significant difference between experimental and control groups in the antibacterial activity and cytotoxicity except for Chika Chika Liq (p<0.05). According to the results, antibacterial activity of oral rinse containing PS was 99.62%, the strongest contact inhibition of Streptococcus mutans strain among tested groups. In the cytotoxicity test of oral rinses, PS had a weaker cytotoxicity than control groups in mouse and human normal cell lines and showed the strongest cytotoxicity in human oral cancer cell lines (KB cell). From the results, PS may be widely used as an oral rinse for the healthy and the patients with oral cancers in the near future.

Abstract: We developed the successive roller type of microneedle system without pain to improve the permeation of drug through the skin barrier. The permeation rates of FITC-ovalbumin (OVA, MW: 45,000g/mole), FITC-insulin (MW: 5,733 g/mole) and FITC-bufexamac (MW: 227.37 g/mole) as model drugs were determined by modified Franz diffusion cells using the microneedle device with four times treatment. The average penetration fluxes of FITC- OVA, FITC-insulin and FITC-bufexamac were steeply increased from 13.4 to 83.3, 10.1 to 110.6 and 11.9 to 242.6 pmol/cm2 with treatment for 12 hrs, respectively. The lower the molecular weight of the drugs, the more the permeation flux investigated. In conclusion, we confirmed the possibility of the application for transdermal delivery of the larger molecular drugs as protein using the designed microneedle treatment device.