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Han, Sang Won,Koh, Won-Gun American Chemical Society 2016 ANALYTICAL CHEMISTRY - Vol.88 No.12
<P>Matrix metalloproteinases (MMPs) play a pivotal role in regulating the composition of the extracellular matrix and have a critical role in vascular disease, cancer progression, and bone disorders. This paper describes the design and fabrication of a microdevice as a new platform for highly sensitive MMP-9 detection. In this sensing platform, fluorescein isocyanate (FITC)-labeled MMP-9 specific peptides were covalently immobilized on an electrospun nanofiber matrix to utilize an enzymatic cleavage strategy. Prior to peptide immobilization, the nanofiber matrix was incorporated into hydrogel micropatterns for easy size control and handling of the nanofiber matrix. The resultant hydrogel-framed nanofiber matrix immobilizing the peptides was inserted into microfluidic devices consisting of reaction chambers and detection zones. The immobilized peptides were reacted with the MMP-9-containing solution in a reaction chamber, which resulted in the cleavage of the FITC-containing peptide fragments and subsequently generated fluorescent flow at the detection zone. As higher concentrations of the MMP-9 solution were introduced or larger peptide-immobilizing nanofiber areas were used, more peptides were cleaved, and a stronger fluorescence signal was observed. Due to the huge surface area of the nanofiber and small dimensions of the microsystem, a faster response time (30 min) and lower detection limit (10 pM) could be achieved in this study. The hydrogel-framed nanofiber matrix is disposable and can be replaced with new ones immobilizing either the same or different biomolecules for various bioassays, while the microfluidic system can be continuously reused.</P>
Lee, Hyun Jong,Koh, Won-Gun American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.12
<P>In this study, we developed multi-functional biomimetic tissue engineered scaffolds that are capable of controlling the spatial locations of stem cells and releasing multiple growth factors with a controlled dose and rate of delivery. This novel scaffold was fabricated by combining electrospinning and photolithography and consisted of polycaprolactone (PCL)/gelatin fibers and poly(ethylene glycol) (PEG) hydrogel micropatterns. The utility of this system was investigated in the context of the osteogenesis of human mesenchymal stem cells (hMSCs). When hMSCs were seeded onto hydrogel-incorporated fibrous scaffolds, they selectively adhered and grew only in the fiber region due to the non-adhesiveness of the PEG hydrogel, enabling spatial positioning of hMSCs on a micrometer scale. For osteogenic differentiation of hMSCs, basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) were loaded on the fibers and within the hydrogel matrix, respectively, to enable sequential delivery of low doses of bFGF during the early stages and sustained release of BMP-2 for long periods. According to in vitro studies, hMSCs cultured on the scaffolds capable of sequential delivery of bFGF and BMP-2 showed stronger osteogenic commitment in culture than those on scaffolds without any growth factors or scaffolds with single administration of either bFGF or BMP-2 under the same conditions. The results demonstrate that hydrogel-incorporated fibrous scaffolds can provide not only biomimetic structures with micropatterned nanostructures but also a suitable biochemical environment with controlled release of multiple growth factors, which may eventually facilitate the control of stem cell fates for various regenerative therapies.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-12/am501714k/production/images/medium/am-2014-01714k_0010.gif'></P>
Yun, Byung Ju,Koh, Won-Gun Elsevier 2020 Journal of industrial and engineering chemistry Vol.82 No.-
<P><B>Abstract</B></P> <P>A new, highly sensitive surface enhanced Raman scattering (SERS)-based immunoassay platform was prepared using silver nanoparticle (AgNP)-decorated electrospun fibers as the capture substrate. We used electrospinning and silver mirror reaction to generate AgNP-decorated polycaprolactone (PCL) fiber matrix (Ag-PCL). The resultant capture substrates obtained were bi-directionally porous, free-standing, and flexible. AgNP formation on the PCL fibers was confirmed via SEM, AFM, XPS, and TGA analysis. In addition, gold nanoparticles immobilized with a Raman reporter, 4-mercaptobenzoic acid (4-MBA), were prepared as the SERS tag. This tag could significantly enhance the SERS signal via generation of additional hot spots between AgNPs on fibers and AuNPs. For a model immunoassay to detect prostate specific antigen (PSA), PSA antibodies were immobilized on both Ag-PCL and AuNP SERS tags. The large surface area of fiber substrates allowed the immobilization of large amounts of antibodies and their porous structures facilitated the assessment of the target antigen to immobilized antibodies. Binding of PSA between antibodies on AgNPs and AuNPs led to formation of a sandwich structure by the two metal nanostructures, and consequently, highly sensitive detection of PSA was possible up to a detection limit of 1pg/mL within 1h of reaction time. The developed SERS-based immunoassay platform produced uniform and reproducible SERS signals over the entire substrate area and from different samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SERS-based immunoassay was carried out using AgNP-decorated electrospun fibers as capture substrate. </LI> <LI> SERS signal was greatly amplified by the generation of hot spots between AgNPs on fibers and AuNP-based SERS tag. </LI> <LI> Fast and sensitive detection of PSA was possible due to the large surface area and porous structure of fibrous substrate. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>