Man Bock Gu

Korea University, Sŏul, Seoul, South Korea

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Publications (163)595.04 Total impact

  • Chul H Song · Man Bock Gu · Ulrich Platt · Shimshon Belkin ·

    Chemosphere 09/2015; 143. DOI:10.1016/j.chemosphere.2015.08.041 · 3.34 Impact Factor
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    ABSTRACT: We present a novel reflectance-based colorimetric aptasensor using gold nanoparticles for the detection of oxytetracycline for the first time. It was found that the reflectance-based measurement at two wavelengths (650 and 520 nm) can generate more stable and sensitive signals than absorbance-based sensors to determine the aggregation of AuNPs, even at high AuNP concentrations. One of the most common antibacterial agents, oxytetracycline (OTC), was detected at concentrations as low as 1 nM in both buffer solution and tap water, which was 25-fold more sensitive, compared to the previous absorbance-based colorimetric aptasensors. This reflectance-based colorimetric aptasensor using gold nanoparticles is considered to be a better platform for portable sensing of small molecules using aptamers.
    The Analyst 09/2015; 140(19). DOI:10.1039/c5an00726g · 4.11 Impact Factor
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    ABSTRACT: It has been more than two decades since aptamer and the systematic evolution of ligands by exponential enrichment (SELEX) method were discovered by Larry Gold and Andrew Ellington in 1990, respectively. Based on the various advantages of aptamers, they have become a potent rival of antibodies in therapeutics and bio-analysis. Especially, the recent advances in aptamer biosensor application are remarkable due to its intrinsic properties of aptamers as nucleic acids and target induced conformational changes, in addition to the introduction of graphene oxide-based easy and simple immobilization-free screening method even for dual aptamers. In addition, the incorporation of various nanomaterials such as metallic nanoparticles, carbon materials, and functional nanospheres in aptasensors has facilitated the improvement of analytical performance and commercial application of aptasensors. In this review, recent prominent reports on aptasensors utilizing nanomaterials were introduced to understand the principle of aptamer-based biosensors and provide an insight for new strategies of aptasensors and the application of various nanomaterials. The perspective on aptamer-based biosensors and diagnostics was also discussed in view of technology and market. Copyright © 2015 Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 06/2015; DOI:10.1016/j.bios.2015.06.040 · 6.41 Impact Factor
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    Nurul Hanun Ahmad Raston · Man Bock Gu ·
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    ABSTRACT: A cognate aptamer duo for visceral adipose tissue-derived serpin (vaspin) which distinctively bind to two different sites on vaspin with high affinity and specificity were successfully developed by using graphene oxide-based systematic evolution of ligands by exponential enrichment (GO-SELEX), which offers immobilization-free screening of aptamers. The specific and simultaneous bindings of this aptamer duo (V1 and V49 aptamers) to the different sites of vaspin were confirmed by circular dichroism (CD) analysis and both sandwich-type surface plasmon resonance (SPR) and quantum dot labelled fluorescence imaging analysis (V1 aptamer serves as primary capturing aptamer and V49 aptamer as secondary signalling aptamer or vice versa). With this vaspin cognate aptamer duo on SPR platform, the detection of the target vaspin were improved to the limit of detection down to 3.5ng/ml in buffer and 4.7ng/ml in human serum samples. This cognate aptamer duo based biosensor could be utilized in the early diagnosis of type-2 diabetes. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 03/2015; 41. DOI:10.1016/j.bios.2015.03.042 · 6.41 Impact Factor
  • Young Seop Kwon · Van-Thuan Nguyen · Je Gun Park · Man Bock Gu ·
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    ABSTRACT: The sensitive detection of iprobenfos (IBF) and edifenphos (EDI) was successfully conducted by using a new aptamer-based colorimetric multi-aptasensor. The dissociation constants of this multi-target aptamer to both iprobenfos and edifenphos were found to be 1.67μM and 38nM, respectively, according to the isothermal calorimetry assay. The aptamer EIA2 was selective to only IBF and EDI, confirmed by AuNP assays. By using this multi-aptasensor, both pesticides IBF and EDI can be eventually detected in a range from 10nM to 5nM, respectively. This multi-aptasensor was successfully implemented in spiked rice samples and the accuracies of this AuNP-based multi-aptasensor were around 80 and 90% in spiked paddy and polished rice samples, respectively. This aptamer EIA2 could be applied not only for the detection of pesticides from real samples in agriculture field as POC, but also can be used as a bioreceptor for other types of aptasensors. Copyright © 2015 Elsevier B.V. All rights reserved.
    Analytica chimica acta 02/2015; 868. DOI:10.1016/j.aca.2015.02.020 · 4.51 Impact Factor
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    Tal Elad · Ho Bin Seo · Shimshon Belkin · Man Bock Gu ·
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    ABSTRACT: We assessed the applicability of multi-strain bacterial bioreporter bioassays to drug screening. To this end, we investigated the reactions of a panel of 15 luminescent recombinant Escherichia coli bacterial bioreporters to a library of 420 pharmaceuticals. The panel included bacterial bioreporters associated with oxidative stress, DNA damage, heat shock, and efflux of excess metals. Eighty nine drugs elicited a response from at least one of the panel members and formed distinctive clusters, some of which contained closely related drugs. In addition, we tested a group of selected nine drugs against a collection of about 2000 different fluorescent transcriptional reporters that covers the great majority of gene promoters in E. coli. The sets of induced genes were in accord with the in vitro toxicity of the tested drugs, as reflected by the response patterns of the 15-member panel, and provided more insights into their toxicity mechanisms. Facilitated by microplates and robotic systems, all assays were conducted in high-throughput. Our results thus suggest that multi-strain assemblages of bacterial bioreporters have the potential for playing a significant role in drug development alongside current in vitro toxicity tests. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 01/2015; 68C:699-704. DOI:10.1016/j.bios.2015.01.067 · 6.41 Impact Factor
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    Insup Jung · Ho Bin Seo · Ji-Eun Lee · Byoung Chan Kim · Man Bock Gu ·
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    ABSTRACT: The use of genetically engineered bioluminescent bacteria, in which bioluminescence is induced by different modes of toxic action, represents an alternative to acute toxicity tests using living aquatic organisms (plants, vertebrates, or invertebrates) in an aqueous environment. A number of these bacterial strains have been developed, but there have been no attempts to develop a hand-held type of biosensor for monitoring or identification of toxicity. We report a facile dip-stick type biosensor using genetically engineered bioluminescent bacteria as a new platform for classification and identification of toxicity in water environments. This dip-stick type biosensor is composed of eight different optically color-coded functional alginate beads that each encapsulates a different bioluminescent bacterial strain and its corresponding fluorescent microbead. These color-coded microbeads exhibit easy identification of encapsulated microbeads, since each microbead has a different color code depending on the bioluminescent bacterial strain contained and improved cell-stability compared to liquid culture. This dip-stick type biosensor can discriminate different modes of toxic actions (i.e. DNA damage, oxidative damage, cell-membrane damage, or protein damage) of sample water tested by simply dipping the stick into the water samples. It was found that each color-coded microbead emitted distinct bioluminescence, and each dip-stick type biosensor showed different bioluminescence patterns within 2 hours, depending on the toxic chemicals contained in LB medium, tap water, or river water samples. This dip-stick type biosensor can, therefore, be widely and practically used in checking toxicity of water in the environment primarily in situ, possibly indicating the status of biodiversity.
    The Analyst 07/2014; 139(18). DOI:10.1039/c4an00308j · 4.11 Impact Factor
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    Van Thuan Nguyen · Young Seop Kwon · JaeHoon Kim · Man bock Gu ·
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    ABSTRACT: We describe a simple, high-speed, high-throughput aptamer screening for a group of small molecules using Graphene Oxide (simple Multi-GO-SELEX) without immobilizing targets for the first time. The affinities of ten different ssDNAaptamers successfully obtained for three pesticides were in a range of 10~100 nM. Beside a specific aptamer for each target, we found a couple of flexible multi-target aptamers, which can bind with 2 or 3 different molecules. These flexible aptamers developed for binding with a mixture of targets not only are significant for the rapid screening of a group of small molecules but also offer great promise for aptamer-based biosensor applications.
    Chemical Communications 07/2014; 50(72). DOI:10.1039/C4CC03953J · 6.83 Impact Factor
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    ABSTRACT: A highly stable, homogeneous and magnetically separable enzyme microbead (EMB) comprised of branched-polymer/silica-shell hybrid microbeads is demonstrated. In addition, an EMB-based modular in vitro cascade reaction system is successfully implemented to the multi-enzymatic reactions with reusability and tractability.
    Green Chemistry 02/2014; 16(3). DOI:10.1039/C3GC41737A · 8.02 Impact Factor
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    Engineering in Life Sciences 01/2014; 14(1). DOI:10.1002/elsc.201470014 · 2.49 Impact Factor
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    ABSTRACT: A shortened 8-mer ssDNA aptamer was successfully truncated for four different tetracyclines with high affinity. The ultrasensitive colorimetric detection of oxytetracycline using this shortened aptamer was possible, which was about 500-fold enhanced compared to that obtained using the original 76-mer aptamer.
    Chemical Communications 11/2013; 50(1). DOI:10.1039/c3cc47108j · 6.83 Impact Factor
  • Man Bock Gu · An-Ping Zeng ·

    Engineering in Life Sciences 09/2013; 13(5):419-420. DOI:10.1002/elsc.201370054 · 2.49 Impact Factor
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    ABSTRACT: In this study, we successfully developed a ssDNA aptamer pairs by using an advanced immobilization-free SELEX method with affinity-based selection and counter-screening process at every round. By implementing this method, two different aptamers specifically binding to bovine viral diarrhea virus type 1(BVDV type 1) with high affinity were successfully screened. This aptamer pair was applied to ultrasensitive detection platform for BVDV type 1 in a sandwich manner. The ultrasensitive detection of BVDV type 1 using one of aptamers conjugated with gold nanoparticles was obtained in aptamer-aptamer sandwich type sensing format, with the limit of detection of 800copies/ml, which is comparable to a real-time PCR method.
    Biosensors & Bioelectronics 08/2013; 51C:324-329. DOI:10.1016/j.bios.2013.07.052 · 6.41 Impact Factor
  • Yeon Seok Kim · Man Bock Gu ·
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    ABSTRACT: : It has been 20 years since aptamer and SELEX (systematic evolution of ligands by exponential enrichment) were described independently by Andrew Ellington and Larry Gold. Based on the great advantages of aptamers, there have been numerous isolated aptamers for various targets that have actively been applied as therapeutic and analytical tools. Over 2,000 papers related to aptamers or SELEX have been published, attesting to their wide usefulness and the applicability of aptamers. SELEX methods have been modified or re-created over the years to enable aptamer isolation with higher affinity and selectivity in more labor- and time-efficient manners, including automation. Initially, most of the studies about aptamers have focused on the protein targets, which have physiological functions in the body, and their applications as therapeutic agents or receptors for diagnostics. However, aptamers for small molecules such as organic or inorganic compounds, drugs, antibiotics, or metabolites have not been studied sufficiently, despite the ever-increasing need for rapid and simple analytical methods for various chemical targets in the fields of medical diagnostics, environmental monitoring, food safety, and national defense against targets including chemical warfare. This review focuses on not only recent advances in aptamer screening methods but also its analytical application for small molecules.
    Advances in biochemical engineering/biotechnology 07/2013; 140. DOI:10.1007/10_2013_225 · 1.66 Impact Factor
  • Ee Taek Hwang · Haemin Gang · Man Bock Gu ·
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    ABSTRACT: The combined effect of both carbonic anhydrase (CA) and the rigidity of polyethylene glycol (PEG) were found to assist the bio-mineralized crystallization behavior of CO2 differentially. In this study, different forms of magnetically responsive calcium carbonate (CaCO3) crystal composites were successfully formed from gaseous CO2 by using the different forms of polyethylene glycols (PEGs) in a constant CO2 pressure controlled chamber. Polygonal particles were produced with more rigid polymer chains (branched PEG), whereas less rigid polymer chains (PEG) induced the formation of ellipsoidal particles. However, no morphological changes occurred without the presence of CA.
    Journal of Biotechnology 07/2013; 168(2). DOI:10.1016/j.jbiotec.2013.06.024 · 2.87 Impact Factor
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    ABSTRACT: We have found that the close proximity among aptamer conjugated gold nanoparticles due to aptamer-target-aptamer binding can occur and result in a color change on fabric pads. In this study, we used aptamer-conjugated gold nanoparticles as a colorimetric transducer and successfully performed in situ onfabric colorimetric detection of thrombin using aptamer-conjugated gold nanoparticles. Gold nanoparticles immobilized with two model aptamers, thrombin binding aptamer (TBA) 15 and TBA 29, respectively, are closely attracted to each other by binding to thrombin. We found that this close proximity among gold nanoparticles occurred not only in solution, but also on fabric pads in the presence of a target protein. The detection sensitivity of this on-fabric colorimetric detection was in a femto-molar range without any specialized amplification process or equipment. Considering that prior diagnosis kits require a complicated fabrication process, this in-situ on-fabric diagnosis system is more stable and cost effective and could be utilized for the on-site diagnosis of various biomarkers by using aptamers instead of antibodies.
    BioChip journal 06/2013; 7(2). DOI:10.1007/s13206-013-7212-x · 1.09 Impact Factor
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    ABSTRACT: The development and implementation of strategies for CO2 mitigation are necessary to counteract the greenhouse gas effect of carbon dioxide emissions. To demonstrate the possibility of simultaneously capturing CO2 and utilizing four-carbon compounds, an integrated system using CA and PEPCase was developed, which mimics an in vivo carbon dioxide concentration mechanism. We first cloned the PEPCase 1 gene of the marine diatom Phaeodactylum tricornutum and produced a recombinant PtPEPCase 1. The affinity column purified PtPEPCase 1 exhibited specific enzymatic activity (5.89 U/mg). When the simultaneous and coordinated reactions of CA from Dunaliella sp. and the PtPEPCase 1 occurred, more OAA was produced than when only PEPCase was present. Therefore, this integrated CA-PEPCase system can be used not only to capture CO2 but also for a new technology to produce value-added four-carbon platform chemicals.
    Bioprocess and Biosystems Engineering 05/2013; 36(12). DOI:10.1007/s00449-013-0968-5 · 2.00 Impact Factor
  • Jinyang Chung · Ee Taek Hwang · Haemin Gang · Man Bock Gu ·
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    ABSTRACT: Uniform magnetic separable robust microbeads using a branched polymer were successfully developed for stable enzyme immobilization. The changed morphology of the microbeads was shown by scanning electron microscopy (SEM) analysis. The aldehyde groups on the polymers and imine groups derived from the Schiff base reaction between the aldehyde and amine moiety were found as the evidence of these reactions based on Fourier transform infrared (FT-IR) spectroscopy. The amine groups of the enzyme react with the aldehyde groups on the glutaraldehyde polymer so that the stable conjugations are formed. The specific activity of the conjugated enzyme was found to be retained more than 50%, but the reaction rate constant, Km value was not changed, compared to the free enzyme. In addition, the enzyme conjugated in the microbeads was found to be highly stable for more than 50 days, pertaining over 60% of its initial activity, even after being reused more than 15 times repeatedly. Furthermore, the magnetic-driven controllability provided facile separable characters for the repeated recycling. It is expected that these microbeads can be utilized as a key tool for successful realization not only in enzymatic conversion processes but also in extended fields; bio-based sensors or analytical devices, bioprocessing, bioremediation, to name only a few of numerous areas.
    Reactive and Functional Polymers 01/2013; 73(1):39–45. DOI:10.1016/j.reactfunctpolym.2012.10.001 · 2.52 Impact Factor
  • Ee Taek Hwang · Man Bock Gu ·
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    ABSTRACT: Immobilization is a key technology for successful realization of enzyme-based industrial processes, particularly for production of green and sustainable energy or chemicals from biomass-derived catalytic conversion. Different methods to immobilize enzymes are critically reviewed. In principle, enzymes are immobilized via three major routes (i) binding to a support, (ii) encapsulation or entrapment, or (iii) cross-linking (carrier free). As a result, immobilizing enzymes on certain supports can enhance storage and operational stability. In addition, recent breakthroughs in nano and hybrid technology have made various materials more affordable hosts for enzyme immobilization. This review discusses different approaches to improve enzyme stability in various materials such as nanoparticles, nanofibers, mesoporous materials, sol–gel silica, and alginate-based microspheres. The advantages of stabilized enzyme systems are from its simple separation and ease recovery for reuse, while maintaining activity and selectivity. This review also considers the latest studies conducted on different enzymes immobilized on various support materials with immense potential for biosensor, antibiotic production, food industry, biodiesel production, and bioremediation, because stabilized enzyme systems are expected to be environmental friendly, inexpensive, and easy to use for enzyme-based industrial applications.
    Engineering in Life Sciences 01/2013; 13(1). DOI:10.1002/elsc.201100225 · 2.49 Impact Factor
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    ABSTRACT: In the present study, we report on enzyme-assisted formation of biomineralized amorphous calcium phosphate nanocomposites (ACP-NCs). About 100-200 nm sizes of the spherical porous enzyme-assisted ACP-NCs were successfully synthesized via double reverse microemulsion, but no ACP-NCs formed without the enzyme. It is believed that the enzyme was used as an organic template or additive that could regulate the biomineralization process. The enzyme-assisted ACP-NCs were well characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, dynamic light scattering, and Brunauer-Emmett-Teller (BET) criteria. The BET surface area, total pore volume, pore size from adsorption, and pore size from desorption of the ACP-NCs were 163 m2 g-1 or 0.37 cm3 g-1, 8.87 nm, and 7.48 nm, respectively. The enzyme-assisted ACP-NCs retained about 43% of the catalytic activity of free carboxyl esterase. Furthermore, they preserved their bioactivity even after 10th reuse and were stable over 10 days even under a stringent shaking condition. The reported method paves the way for novel biomineralization via enzyme molecules to form functional enzymes containing nanocomposites.
    ACS Applied Materials & Interfaces 12/2012; 5(3). DOI:10.1021/am302580p · 6.72 Impact Factor

Publication Stats

4k Citations
595.04 Total Impact Points


  • 2006-2015
    • Korea University
      • • College of Life Sciences
      • • Department of Chemical and Biological Engineering
      Sŏul, Seoul, South Korea
  • 2013
    • Technische Universität Hamburg-Harburg
      • Institute of Bioprocess and Biochemical Engineering
      Hamburg, Hamburg, Germany
  • 1995-2008
    • University of Delaware
      • Department of Chemical and Biomolecular Engineering
      Newark, DE, United States
  • 2003-2007
    • Gwangju Institute of Science and Technology
      • School of Environmental Science and Engineering
      Gwangju, Gwangju, South Korea
  • 2005
    • Pennsylvania State University
      • Department of Chemical Engineering
      University Park, Maryland, United States