다목적댐 연계를 통한 신규사업 진행시 발생되는 문제 고찰(부제 : 춘천시 안정적 맑은물 공급사업 변경)

홍상현,이준희 한국유체기계학회 2021 유체기계 연구개발 발표회 논문집 Vol.2021 No.12

Fabrication of Polystyrene/Carbon nanotube nanocomposite by latex aggregation

홍상현,심상은 한국고분자학회 2008 한국고분자학회 학술대회 연구논문 초록집 Vol.33 No.1

Mussel-inspired surface functionalization by tethering of aldehyde-containing molecule

홍상현,이해신 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Polydopamine (pDA) coating has been issued in the past decade due to its unique material-independent surface modification property. Deposited pDA layers have been applied to various fields because it can be functionalized through simple co-deposition of materials and dopamine. However, this reaction is limited to amine- and thiol-containing molecules, and functionalization with aldehyde has been rarely attempted. Here, we develop a surface functionalization strategy by dopamine-aldehyde coupling, and modified substrates successfully demonstrated anti-fouling, hydrophobic, protein-affinity properties.

Single Component Hydrogel Exhibiting Stretchable, Self-healing,and Mutifunctional Properties Simultaneously

홍상현,이해신 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

For the increasing demand of soft materials with wide range of applications, hydrogels have been developed exhibiting variety of functions. In general, most hydrogels have been designed by multiple component to achieve some functionalities. Multi-conponent systems often requires tremendous labors during preperation process and accompany undesirable reactions that can be avoidable in single component hydrogel system. Here, we developed single component hydrogel, alginate-boronic acid hydrogel, that can exhibit unprecedented multi-functionalities simultaneously such as high stretchable, self-healing, shear-thinning, pH- and glucose-sensitivities, adhesive, and re-shaping properties. Multi-functionalities of alginate-BA hydrogel is resulted from the reversible inter-, intra-molecular interactions by dynamic equilibrium of boronic acid-diol complexation and dissociation. These findings suggest that this novel hydrogel have potentials for use in wide range of biomedical applications.

진정요법과 약물남용

홍상현 대한의사협회 2013 대한의사협회지 Vol.56 No.4

Procedural sedation is now becoming more popular in South Korea along with the increases in cosmetic procedures and surgery, gastrointestinal endoscopy, and minimally invasive surgery,which have been accompanied by a surge in propofol abuse. The mechanism of potential abuse of sedatives and hypnotics share the common feature of all addictive drugs, in that they increase dopamine concentrations in target structures in the mesolimbic dopamine system. The abuse of sedatives and hypnotics occupies a small proportion of all substance abuse; however,propofol abuse is sharply increasing and is closely associated with procedural sedation in South Korea. Previous case reports have indicated that the majority of propofol abusers were healthcare providers; however, recreational use of propofol is spreading among the general public. Lay people become addicted to propofol through repetitive procedural sedation or wrongful use by clinicians who are enticed by the promise of monetary gain. Illicit distribution of propofol accelerates abuse by lay people. The extremely narrow safety margin of propofol may cause a large number of fatal cases. Therefore, nationwide establishment of a policy to prevent the spread of propofol abuse is urgently needed.

Ultrafast sprayable polydopamine surface modifications

홍상현,이해신 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

Stability increase of Ca²⁺-alginate hydrogels by spontaneous ionic-to-covalent bond exchange

홍상현,이해신 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Alginate is a linear polysaccharide extracted from brown algae and composed of homopolymeric blocks of (1-4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G). The most representative features of alginates are the stiffnesses of their polymer chains and their affinities to various transition metal cations, such as Cd²⁺, Ni²⁺, or Mn²⁺, which could be exploited for metal removal in environmental science and engineering. Recently, applications have been expanded to energy storage devices. For example, alginate is used as a silicon anode binder in Li-ion batteries due to the stiffness of the alginate backbone. In addition to environmental sciences and energy storage technologies, the most well-known research field utilizing alginate has been biomaterial sciences. The prompt formation of alginate gels in the presence of calcium ions in aqueous solutions (known as Ca²⁺-alginate gel) has been a useful method of encapsulating and then releasing various macromolecular pharmaceuticals. An early example is the encapsulation of islets to release insulin upon the infusion of glucose for treating diabetes. Additionally, alginate gels are used for local delivery of incorporated vascular endothelial growth factor (VEGF) to enhance angiogenesis in peripheral tissues. Despite the widespread uses, the major drawback of Ca²⁺-alginate gels is rapid gel dissolution due to ionic bond dissociation between the encapsulated Ca²⁺ ions and the carboxylic acid (R-COO-) groups along alginate backbones. This issue prevents the widespread use of Ca²⁺-alginate hydrogels for drug delivery or tissue engineering scaffolds. Methods to overcome this gel dissolution have been developed mostly using cationic polymer coatings. The coatings performed with poly L-lysine, chitosan, or poly(ethylenimine) on hydrogel surfaces showed increased physical stabilities, but nonetheless, the dissociation of the coated polymers is unavoidable, resulting in problems for long-term stability. Alternatively, the formation of covalent bonds via carbodiimide conjugation or reductive amination chemistries increases the physical stability. However, these approaches are generally not compatible with in situ encapsulations of cells or proteins due to the presence of coupling agents. Thus, we hypothesized that combining these two approaches (ionic and covalent linkages) might provide a new method to prepare alginate hydrogels. Our new approach uses ionic couplings for cell encapsulation initially and later in time the covalent bonds are formed, which gradually replace the ionic bonds, thus increasing the physical stability of the alginate gel. We called this alginate gel ‘STAPLE’, an abbreviation for Stable Alginate gel Prepared via Linkage Exchange from ionic to covalent bonds. The key chemistry in STAPLE is the ionic to covalent bond transitions, where the catechol moieties tethered along alginate chains are slowly oxidized to catecholquinone. The catecholquinone mediated crosslinking kinetics are well matched with the kinetics of Ca²⁺ dissociation at pH 7.4 and 37°C. Thus, the original physicochemical integrity of the hydrogel is preserved even after the Ca²⁺ dissociation. This novel method to prepare alginate hydrogels may increase the potential utility in a variety of biomedical applications.

Preparation of Highly Emissive Fluorescent Particle for Robust Coatings and Bio-imaging

홍상현,이해신 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Polydopamine coating has been issued in the past decade due to its unique material-independent surface modification ability, and there have been many demonstrations of co-deposition of amine-, thiolcontaining molecules with dopamine to form Michael addition. However, co-deposition with aldehyde group has been rarely attempted. In this work, dopamine and aldehyde were co-polymerized through Schiff-base reaction, and the rapid reaction allowed formation of aggregates that can be deposited on various substrates. Modified substrates was successfully functionalized by aldehyde coupling demonstrating anti-fouling and controlling wettability. Interestingly, the resultant particles showed high a fluorescence signal, which remained even when the particles were coated on substrates. This novel fluorescent polydopamine particle shows great potential in bio-imaging applications such as live cell imaging.

차량속도와 라이즈비에 따른 타이드 아치형 거더의 동적증폭

홍상현,이종세,박경훈,노화성 한국방재학회 2014 한국방재학회논문집 Vol.14 No.5

In this paper the effect of rise ratio on the dynamic amplification (DA) of the tied-arch girder is investigated through a finite elementanalysis. Equivalent nodal loads are considered for the modeling of moving vehicle loads, and several vehicle speeds ranged between60 km/hr and 120 km/hr are applied for the DA investigation. For detailed investigation, the relationship between the first mode frequencyof the girder and the DA at the middle of the girder is investigated. The results show that the DA of the girder sensitively variesaccording to the rise ratio; especially when the rise ratio is more than 0.03, the maximum DA is relatively larger than the cases ofthe smaller rise ratio. Such result is appeared since the girder becomes more flexible and the developing time of the maximum DA isclose to the first natural period of the girder. 본 논문에서는 타이드 아치형 거더의 라이즈비에 따른 동적증폭을 유한요소해석을 통해 분석하였다. 이동차량하중은 등가 절점하중으로 모델링하였으며 60 km/hr에서 120 km/hr까지의 다양한 범위의 차량속도에 따른 동적증폭을 비교하였다. 자세한 분석을 위해 거더중앙부에 최대 동적증폭이 발생하는 시간과 1차 모드 고유주기와의 관계를 분석하였다. 해석결과, 거더의 동적증폭은 라이즈비에 따라크게 변화하였으며, 특히 라이즈비 0.03 이상일 경우 최대 동적증폭은 크게 증가하는 경향을 보였다. 이러한 결과는 거더가 보다 유연해지고 거더 중앙부에서의 최대 동적증폭의 발생시간이 거더의 1차 모드 고유주기에 가까워지기 때문으로 판단된다.

Controlled synthesis of alginate hydrogel via boronic acid and cis-diol interactions

홍상현,이해신 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Hydrogels have been used for many applications due to its unique and desirable properties. And those characteristics and applications of the gels are closely related to their preparation methods. In this study, we introduced boronic acid (BA) into alginate backbone for specific binding between BA and diol group in alginate and successfully prepared hydrogel by its own component without adding any other cross-linkers. The hydrogel showed high sensitivity to pH change due to the pH responsibility of the BA-diol interactions. Furthermore alginate-BA gel prepared under specific conditions showed interesting mechanical properties such as sol-gel transition, adhesiveness, self-healing, re-shaping, superior elongation. We expect that these excellent mechanical properties and specific binding with diol can be used for biomedical applications.