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김혁정,김예지,Su Jung Park,권찬호,노혜란 한국바이오칩학회 2018 BioChip Journal Vol.12 No.4
Contamination by pesticides is an everincreasing problem associated with fields of environmental management and healthcare. Accordingly, appropriate treatments are in demand. Pesticide detection methods have been researched extensively, aimed at making the detection convenient, fast, cost-effective, and easy to use. Among the various detecting strategies, paper-based assay is potent for real-time pesticide sensing due to its unique advantages including disposability, light weight, and low cost. In this study, a paper-based sensor for chlorpyrifos, an organophosphate pesticide, has been developed by layering three sheets of patterned plates. In colorimetric quantification of pesticides, the blue color produced by the interaction between acetylcholinesterase and indoxyl acetate is inhibited by the pesticide molecules present in the sample solutions. With the optimized paper-based sensor, the pesticide is sensitively detected (limit of detection=8.60 ppm) within 5 min. Furthermore, the shelf life of the device is enhanced to 14 days after from the fabrication, by treating trehalose solution onto the deposited reagents. We expect the paper-based device to be utilized as a firstscreening analytic device for water quality monitoring and food analysis.
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Influence of Solution pH on Drug Release from Ionic Hydrogel Lens
김근희,김혁정,노혜란 한국고분자학회 2019 Macromolecular Research Vol.27 No.2
Hydrogel contact lenses have shown the possibility for uses in ophthalmological treatment for the last decades. Moreover, structural changes responsive to solution pH have given further applications toward more complicated drug delivery for physiological and pathological states of a wearer. However, unpredicted variables, swelling degree, and polymer degeneration, have been hurdles for the evaluation and quantification of a designed pharmaceutic system. Many scientists believe understanding empirical/semi-empirical mechanisms behind the drug release can offer simple solutions to quantify and furthermore control the drug release. In this study, we developed silicon-copolymerized hydrogel contact lenses with various functional monomers for delivery of hydroxypropyl methylcellulose, one of the commonly used dry eye drugs. Under the physiological pH, the prepared hydrogels showed different swelling reactions in response to ionic interaction. In addition, analysis of the pH sensitivity and maximum release amounts against the artificial tear pH suggested possible molecular changes in the functional groups and swelling behaviors. Accordingly, the mathematical parameters were calculated to better understand the drug release mechanism from hydrogels. By evaluating these parameters, the primary rate-limiting factors of the silicone hydrogel contact lenses were determined at the investigated pH. These results, with the simple mechanistic study, imply the potentials of silicone hydrogel contact lens in controlled drug delivery under the physiological conditions.
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pH Sensitive Soft Contact Lens for Selective Drug-Delivery
김근희,김혁정,노혜란 한국고분자학회 2018 Macromolecular Research Vol.26 No.3
In this study, we evaluated contact lenses as drug delivery media and the effect of tear physiological pH on drug release behavior. Anionic or cationic hydroxyethyl methacrylate (HEMA) lenses were polymerized with either vinylpyrrolidone (VP) or N-isopropylacrylamide (NIPAAm). The pH of artificial tears was prepared as between 5.8 and 8.35. One of common treatments, hydroxypropyl methylcellulose (HPMC), to dry eye disease was used as a test drug. As a result, drug releases from anionic 100% p-HEMA and p-HEMA-VP lens were both increased with increasing tear pH. However, released drug amounts from cationic the p-HEMA-NIPAAm lens were decreased with increasing pH. In weak basicity (pH 8.03), the p-HEMA-VP (20 wt%) lens swelled resulting releasing drugs 3.5 times more compared to in weak acidity (pH 5.80). On the other hand, the p-HEMA-NIPAAm (20 wt%) lens de-swelled in basic solution resulting decreased drug release compared to in acidic solution. The hydrogel contact lenses showed various physical properties and drug releasing properties including diffusion coefficients in response to ionization reactions between ionic groups in the lens and pH of solution. It suggests that hydrogel contact lens has potential as selective drug delivery media.
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Numerical technique for chloride ingress with cover concrete property and time effect
이방연,Mohamed A. Ismail,김혁정,유성원,권성준 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.2
Durability problems initiated from steel corrosion are unseen but critical issues, so that many researches are focused on chloride penetration evaluation. Even if RC (Reinforced Concrete) structures are exposed to normal environment, chloride ingress varies with concrete surface conditions and exposed period. This paper presents an analysis technique for chloride behavior evaluation considering time effect on diffusion and surface conditions assumed as double-layered system. For evaluation of deteriorated surface condition, field investigation was performed for concrete pavement exposed to deicing agent for 18 years. In order to consider enhanced surface concrete, chloride profiles in surface-impregnated concretes exposed to chloride attack for 2 years from previous research were investigated. Through reverse analysis, effectively deteriorated/ enhanced depth of surface and the related reduced/enlarged diffusion coefficient in the depth are simulated. The proposed analysis technique was evaluated to handle the chloride behavior more accurately considering changes of chloride ingress within surface layer and decreased diffusion coefficient with time. For the concrete surface exposed to deicing agent, the deteriorated depth and enlarged diffusion coefficient are evaluated to be 12.5~15.0 mm and 200% increasing diffusion coefficient, respectively. The results in concrete containing enhanced cover show 10.0~12.5 mm of impregnated depth and 85% reduction of chloride diffusion in tidal and submerged conditions.
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