• 한국수소및신에너지학회논문집
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• 제27권5호
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• pp.540-546
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• 2016

Besides high-efficient photovoltaics based on silicon, polymers, dye-sensitization and hybrid perovskite materials, biomimetic solar cells inspired by a leaf in nature has also been actively studied. As one example, a hydrogel based photovoltaics (HGPV) is a low-cost, environmentally friendly device and requires easy fabrication process. In this paper, the effect of hydroquinone additive on the performance of the HGPV is discussed. The photocurrent increases ~14 times upon the addition of hydroquinone into the agarose hydrogel medium. The photocurrent increase is maximum at the optimum dye concentration, while the photovoltage is barely affected by the dye concentration. The effect of the agarose content in the hydrogel and the types of dyes on the photocurrent is also investigated. Finally, it is shown that the photovoltaic performance of HGPV with hydroquinone can be drastically improved when $TiO_2$ film is deposited on the anode electrode.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.183-183
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• 2006

Hyaluronic acid and chitosan-based poly(ethylene oxide) (HA-PEO and Chitosan-PEO) hydrogels have been employed as unique biomedical polymeric materials with properties such as bioactivity from polysaccharide, biocompatibility of HA and chitosan as well as PEO and control release of bioactive molecules from the hydrogel itself. We here examine in situ hydrogels based on hyaluronic acid and chitosan in terms of their synthesis, mechanical properties, morphologies and in vitro cellular interactions on their surface and inside. In vivo bone regeneration of HA-PEO and Chitosan-PEO hydrogels was compared with in mouse model.

• Journal of Pharmaceutical Investigation
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• 제40권2호
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• pp.91-100
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• 2010

The objective of this work is to study transdermal delivery of donepezil hydrochloride (DH) using iontophoresis and to evaluate various factors which affect the transdermal transport. After the flux study using 4 kinds of hydrogel, hydrogel containing 8% poly(ethylene oxide) (PEO) was chosen as the hydrogel for further studies. Under experimental condition, DH was stable. We have studied the effect of polarity, current density, drug concentration and current profile on transdermal flux and compared the results. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. DH is positively charged at pH 7.4, and anodal delivery was much larger than cathodal and passive delivery at all current densities studied (0.2, 0.4 and 0.6 mA/$cm^2$). Cathodal delivery showed higher flux than passive flux. Flux increased as the concentration of DH in hydrogel increased. Pulsatile application of current showed smaller flux value than the application of continuous current. Based on these results, we have evaluated the possibility of delivering enough amount of DH to reach the therapeutic level. The maximum cumulative amount of DH transported for 12 hours was 455 ${\mu}g/cm^2{\cdot}hr$ when the amount of DH in the hydrogel was 3 mg/mL and the current density was 0.4 mA/$cm^2$. If the patch size is 10 $cm^2$, then we can deliver 4.6 mg for 12 hours. Because the daily dosage of DH is 5 mg, it seems possible to deliver clinically effective amount of DH using iontophoresis. This study also provides some information about the role of electrorepulsion and electroosmosis during the transport through skin.

• The Korean Journal of Physiology and Pharmacology
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• 제19권6호
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• pp.543-547
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• 2015

We investigated the combined moisturizing effect of liposomal serine and a cosmeceutical base selected in this study. Serine is a major amino acid consisting of natural moisturizing factors and keratin, and the hydroxyl group of serine can actively interact with water molecules. Therefore, we hypothesized that serine efficiently delivered to the stratum corneum (SC) of the skin would enhance the moisturizing capability of the skin. We prepared four different cosmeceutical bases (hydrogel, oil-in-water (O/W) essence, O/W cream, and water-in-oil (W/O) cream); their moisturizing abilities were then assessed using a $Corneometer^{(R)}$. The hydrogel was selected as the optimum base for skin moisturization based on the area under the moisture content change-time curves (AUMCC) values used as a parameter for the water hold capacity of the skin. Liposomal serine prepared by a reverse-phase evaporation method was then incorporated in the hydrogel. The liposomal serine-incorporated hydrogel (serine level=1%) showed an approximately 1.62~1.77 times greater moisturizing effect on the skin than those of hydrogel, hydrogel with serine (1%), and hydrogel with blank liposome. However, the AUMCC values were not dependent on the level of serine in liposomal serine-loaded hydrogels. Together, the delivery of serine to the SC of the skin is a promising strategy for moisturizing the skin. This study is expected to be an important step in developing highly effective moisturizing cosmeceutical products.

• Macromolecular Research
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• 제13권6호
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• pp.483-490
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• 2005

A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan ($_{k}C$), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for $_{k}C$­g-polymethacrylic acid ($_{k}C$-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were preliminarily investigated. Absorbency in aqueous salt solutions of lithium chloride, sodium chloride, potassium chloride, calcium chloride, and aluminum chloride indicated that the swelling capacity decreased with increased ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. The swelling of super absorbing hydrogels was measured in solutions with pH ranging from 1 to 13. In addition, the pH reversibility and on-off switching behavior, at pH levels of 3.0 and 8.0, give the synthesized hydrogels great potential as an excellent candidate for the controlled delivery of bioactive agents.

• 통합자연과학논문집
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• 제11권1호
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• pp.39-43
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• 2018

Poly(hydroxyethyl methacrylate)-based hydrogels were surface-functionalized with spiropyran (SP) derivatives to obtain photochromic contact lenses. The contact lens reversibly changes from colorless to purple as response to UV light since colorless ring-closed SP state converts to purple ring-opened merocyanine (MC) state under UV light irradiation. The purple contact lens emits red light at 640 nm. Importantly, the presence of SP segments did not significantly affect the equilibrium water content (EWC) of the lens. SP-functionalized hydrogel lenses may find potential applications in developing light-adaptive ophthalmic materials.

• Carbon letters
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• 제11권2호
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• pp.122-126
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• 2010

The alginate-based hydrogel was prepared as a pH-sensitive drug delivery system. To enhance the drug loading capacity, activated carbon was introduced as a drug absorbent. The iron oxide was incorporated into the alginate matrix for the magnetic transferring to the target organ. The activated carbon and iron-oxide were dispersed uniformly in the alginate hydrogel. The drug release from the alginate/activated carbon composite hydrogel was carried out in various pH conditions with vitamin B12 and Lactobacillus lamnosers as model drugs. The fast and sustainable release of drug was observed in the basic condition due to the pH-sensitive solubility of alginate. The novel drug delivery system having pH-sensitive release property and magnetic movement to target place was developed by using the alginate/activated carbon composite magnetic hydrogels.

• 대한의용생체공학회:의공학회지
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• 제37권5호
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• pp.186-194
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• 2016

In this study, a co-axial flow induced microfluidic chip to fabricate pure collagen type I microfiber via the control of collagen type I and Na-alginate gelation process. The pure collagen type I microfiber was generated by selective degradation of Ca-alginate from 'Core-Shell' structured hydrogel microfiber. To make 'Core-Shell' structure, collagen type I solution was introduced into core channel and 1.5% Na-alginate solution was injected into side channel in microfluidic chip. To evaluatethe 'Core-Shell' structure, the red and green fluorescence substances were mixed into collagen type I and Na-alginate solution, respectively. The fluorescence substances were uniformly loaded into each fiber, and the different fluorescence images were dependent on their location. By immoblizing EpH4-Ras and C6 cells within collagen type I and Na-alginate solution, we sucessfully demonstrated the co-culture of EpH4-Ras and C6 cells with 'Core-Shell' like hydrogel microfiber for 5 days. Only to produce pure collagen type I hydrogel fiber, tri-sodium citrate solution was used to dissolve the shell-like Ca-alginate hydrogel fiber from 'Core-Shell' structured hydrogel microfiber, which is an excellent advantage when the fiber is employed in three-dimensional scaffold. This novel method could apply various application in tissue engineering and biomedical engineering.

• 폴리머
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• 제38권5호
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• pp.626-631
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• 2014

물을 정수하기 위해서는 그에 상응하는 막대한 양의 에너지가 소모되고, 이 때 소모되는 에너지는 환경오염을 야기할 수 있다. 이러한 문제 때문에 정수 공정 중에 상대적으로 낮은 에너지를 요구하는 정삼투 방법이 많은 관심을 받아왔다. 그러나 정삼투 방법은 오염수로부터 물을 끌어오기 위해서 높은 삼투압을 발생시킬 수 있는 유도용질이 필요하다는 점 때문에 어려움이 있었고 본 연구에서는 poly(N-isopropylacrylamide)(PNIPAM)이라는 온도 감응성 고분자 하이드로젤을 기본으로 하는 양쪽성 이온 물질과의 공중합체와 interpenetrating polymer network(IPN) 구조를 가지는 하이드로젤을 제작하고 이를 정삼투막에 부착시켜 성공적으로 유도용질 역할을 수행함을 확인하였다. 공중합체의 경우 팽윤비가 급격히 증가한 것을 확인할 수 있었으나, 그 만큼의 온도감응성이 떨어지는 모습을 보였고 IPN 구조의 경우는 온도감응성과 팽윤비 값이 PNIPAM 젤에 약간 못 미쳤다. 여기에 팽윤비 값과 삼투압의 관계를 확인하였다.

• 통합자연과학논문집
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• 제9권4호
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• pp.249-254
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• 2016

This study evaluated the physical and optical characteristics of hydrophilic ophthalmic polymer with addition of 2-methacryloyloxyethyl phosphorylcholine in the basic hydrogel ophthalmic lens material, and in particular, the utility of 2-methacryloyloxyethyl phosphorylcholine as an ophthalmic contact lens material for ophthalmologic devices was investigated. In this study 2-methacryloyloxyethyl phosphorylcholine were used as additives. For the preparation of hydrogel lens 2-hydroxyethyl methacrylate, methyl methacrylate, acrylic acid and a cross-linker EGDMA were copolymerized in the presence of AIBN as an initiator. The physical properties of the produced polymers were measured as followings. The refractive index of 1.433~1.393, water content of 35.95~53.16%, contact angle of $70.6{\sim}51.24^{\circ}$, UVB transmittance of 81.2~82.4%, UV-B transmittance of 81.2~82.4% and visible transmittance of 91.4~92.2% were obtained. Also, in case of protein absorption, the measurement showed that absorbance of Reference and MPC-10 sample was 0.2598 and 0.2250 respectively. Based on the results of this study, ophthalmic lens material containing 2-methacryloyloxyethyl phosphorylcholine is expected to be used usefully as a material for high wettability and inhibitor of protein adsorption for ophthalmic hydrogel lens.