Plasma-Treated PLGA Nanofiber Matrices for Tissue Engineering

Honghyun Park,Ko Eun Park,Won Ho Park,Keun Yong Lee 한국고분자학회 2006 한국고분자학회 학술대회 연구논문 초록집 Vol.2006 No.10

Shear-reversibly Crosslinked Alginate Hydrogels for Tissue Engineering

Park, Honghyun,Kang, Sun-Woong,Kim, Byung-Soo,Mooney, David J.,Lee, Kuen Yong WILEY-VCH Verlag 2009 Macromolecular bioscience Vol.9 No.9

<P>Injectable delivery vehicles in tissue engineering are often required for successful tissue formation in a minimally invasive manner. Shear-reversibly crosslinked hydrogels, which can recover gel structures from shear-induced breakdown, can be useful as an injectable, because gels can flow as a liquid when injected but re-gel once placed in the body. In this study, injectable and shear-reversible alginate hydrogels were prepared by combination crosslinking using cell-crosslinking and ionic crosslinking techniques. The addition of a small quantity of calcium ions decreased the number of cells that were required to form cell-crosslinked hydrogels without changing the shear reversibility of the system. The physical properties and gelation behavior of the gels were dependent on the concentration of both the cells and the calcium ions. We found that gels crosslinked by combination crosslinking methods were effective to engineer cartilage tissues in vivo. Using both ionic and cell-crosslinking methods to control the gelation behavior may allow the design of novel injectable systems that can be used to deliver cells and other therapeutics for minimally invasive therapy, including tissue engineering.</P><P> <img src='wiley_img/16165187-2009-9-9-MABI200800376-gra001.gif' alt='wiley_img/16165187-2009-9-9-MABI200800376-gra001'> </P> <B>Graphic Abstract</B> <P>Injectable alginate hydrogels with shear-reversible gelation behavior can be prepared by combination crosslinking using cell-crosslinking and ionic crosslinking techniques. The addition of a small quantity of calcium ions can decrease the number of cells which are required to form cell-crosslinked hydrogels without changing the shear reversibility. Gels are useful to engineer cartilage tissues in vivo. <img src='wiley_img/16165187-2009-9-9-MABI200800376-content.gif' alt='wiley_img/16165187-2009-9-9-MABI200800376-content'> </P>

Alginate hydrogels modified with low molecular weight hyaluronate for cartilage regeneration

Park, Honghyun,Lee, Hyun Ji,An, Hyoseok,Lee, Kuen Yong Applied Science Publishers 2017 Carbohydrate polymers Vol.162 No.-

<P><B>Abstract</B></P> <P>Alginate is a typical biomaterial that forms hydrogels in the presence of calcium ions and has often been utilized in tissue engineering approaches. However, it lacks biofunctionality in the form of interactions with cells and proteins. Hyaluronate, a main component of glycosaminoglycans, provides CD44-specific interactions with chondrocytes but typically requires chemical cross-linking agents to fabricate hydrogels, which may cause unexpected side effects in the body. In this study, we propose the design and fabrication of a hybrid structure of alginate and hyaluronate useful for cartilage regeneration. Alginate was used as a backbone, and hyaluronate with a low molecular weight was introduced to the backbone to fabricate alginate-hyaluronate hybrid coupled by ethylenediamine. We hypothesized that alginate-hyaluronate hybrid (AH) could maintain its ability to form gels in the presence of calcium ions and could be useful for cartilage regeneration as an injectable system. Characteristics of AH hydrogels containing various composition ratios of hyaluronate to alginate were investigated, and the chondrogenic potential of ATDC5 cells encapsulated within AH hydrogels was evaluated <I>in vitro</I>. Consequently, AH hydrogels having a defined polymer composition and mechanical stiffness were useful to successfully regulate chondrogenic differentiation and to maintain the chondrocytic cell phenotype, which may lead to many useful applications in cartilage regeneration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Alginate-hyaluronate hybrid can be synthesized via ethylenediamine linkage. </LI> <LI> Alginate-hyaluronate hybrid forms hydrogels in the presence of calcium ions. </LI> <LI> Alginate-hyaluronate hybrid gels have potential in cartilage regeneration. </LI> <LI> Defined polymer composition and gel stiffness are critical for tissue regeneration. </LI> </UL> </P>

Quantifying specific cell–polymer interactions using fluorescence correlation spectroscopy

Park, Honghyun,Lee, Kuen Yong Royal Society of Chemistry 2011 SOFT MATTER Vol.7 No.10

<P>Evaluation of interactions between polymers and cells is very important in many biomedical applications, including tissue engineering, as polymer scaffolds represent the extracellular matrix in the body and provide cells with three-dimensional framework. Alginate was modified with a peptide with the sequence of arginine–glycine–aspartic acid (RGD) to prepare cell-interactive polymers, and specific interactions between mouse fibroblasts and RGD peptide-modified alginates were investigated using fluorescence correlation spectroscopy (FCS). FCS was useful for determining cell–polymer interactions in a quantitative manner at nanomolar polymer concentrations, and the results were consistent with those obtained from the fluorescence resonance energy transfer (FRET) technique. This approach of quantitatively determining interactions between cells and polymers could be useful for developing novel polymer scaffolds for tissue engineering, as well as for designing highly efficient drug delivery systems.</P> <P>Graphic Abstract</P><P>Specific interactions between cells and cell-interactive polymers can be quantified using fluorescence correlation spectroscopy. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm01553a'> </P>

기능성 고분자를 이용한 수식 셀룰라아제의 폐 신문용지 탈묵에 관한 연구

김홍현(Honghyun Kim),곽태헌(Tae-Heon Kwak),박진원(Jinwon Park),박귀남(Kwinam Park) 한국청정기술학회 2004 청정기술 Vol.10 No.4

대체냉매 R1234yf를 적용한 자동차용 에어컨 시스템의 성능향상에 관한 연구

조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.4

The performance of automobile air conditioning systems of R1234yf was evaluated and compared with that of R134a. In particular, the performance evaluation was carried out by installing an internal heat exchanger in order to improve the performance of the system used in R1234yf. A performance comparison between the R1234yf and R134a for automotive air conditioning revealed that the cooling capacity and COP of the 1234yf system without the IHX decreased by up to 7% and 4.5%, respectively, but those with the IHX decreased by up to 1.8% and 2.9%, respectively.

R134a 및 R1234yf 적용 냉동시스템의 비가역성 분석

조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6

In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The irreversiblilty of evaporator in a R134a air conditioning system with compressor speed under idle condition was 36.8% which was maximum value, and that of compressor increased with compressor speed. The irreversibility of compressor and IHX in a R1234yf air conditioning system with IHX with compressor speed was 39.6%, 3.6% under idle condition, and those was 44.1%, 9.7% at the compressor speed of 2520 rpm.

냉매 R1234yf 적용 자동차용 에어컨 Drop-in 성능 특성

조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.12

In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The experimental setup of a MAC consists of an belt driven compressor, a condenser, an evaporator and a block type thermal expansion valve. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The compressor discharge temperature of R1234yf is 8℃ lower than that of R134a. The cooling capacity with R1234yf system decreased by 4~7% compared with R134a system. In addition, The COP of R1234yf system is lower 3~4% than that of R134a system.

효소개질 공중합고분자 합성 및 개질 lipase에 관한 연구

김홍현,강신원,박귀남,박진원 한국공업화학회 2004 응용화학 Vol.8 No.1

Copolymer consists of polyethylene oxide (PEO) and maleic acid anhydride (MA) was used to modify the lipase. By controlling the ratio of ethylene oxide to alkylene oxide (AO), hydrophilic property of copolymer was controlled and the MA functional group of copolymer covalently coupled with the amino groups of lipase. Activity of modified lipase increase more than native one by about 20~30% due to substrate effect of synthesized copolymers. Native lipase was absolutely specific that only reacts limited substrate. However, as the modification was progressed, lipase was changed to group specificity that widely reacts several substrates having similar characteristic.

R1234yf와 R134a 냉매의 이젝터를 적용한 냉동사이클 성능에 대한 해석적 연구

조홍현(Honghyun Cho),박차식(Chasik Park) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.7

This paper presents a numerical study on the performance of a vapor compression cycle equipped with an ejector as an expansion device to improve the COP by reducing the expansion loss and compressor work. The simulation is carried out using a model based on the conservation of mass, energy and momentum in the ejector. From the results of the simulation, the vapor compression cycle equipped with an ejector showed a maximum COP improvement of 14.0% when using R134a refrigerant and 16.8% when using R1234yf. In addition, the performance of the system with an ejector represents the increased performance as the temperature difference between condensing and evaporating increased.