Man Bock Gu

Korea University, Sŏul, Seoul, South Korea

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Publications (148)495.47 Total impact

  • [Show abstract] [Hide abstract]
    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; · 4.23 Impact Factor
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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; · 6.38 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). · 6.83 Impact Factor
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    Engineering in Life Sciences 01/2014; 14(1). · 1.63 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; · 6.38 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. · 5.43 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; · 1.64 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; · 3.18 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; · 1.87 Impact Factor
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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. · 2.51 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). · 1.63 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; · 5.01 Impact Factor
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    ABSTRACT: We developed a DNA microarray that contains random genomic DNA fragments of Listeria monocytogenes, validated its diagnostic abilities using cells grown in laboratory media and milk, and established enrichment conditions for detection of a low population of L. monocytogenes in milk. Genomic DNA of L. monocytogenes strain ATCC 19111 was fractionated by agarose gel electrophoresis after being cleaved using several different pairs of restriction enzymes. Sixty DNA fragments of different sizes were randomly selected and spotted onto an amine-coated glass slide. To validate diagnostic ability, probes on the DNA microarray were hybridized with genomic DNA extracted from L. monocytogenes, other Listeria spp., and foodborne pathogenic bacteria belonging to other genera grown in laboratory media. The DNA microarray showed 98-100% positive hybridization signals for the 16 strains of L. monocytogenes tested, 7-85% positive signals for 9 strains of other Listeria spp., and 0-32% positive signals for 13 strains of other types of foodborne pathogens. In milk, the detection limit of the DNA microarray was approximately 8 log CFU/mL. When milk contained L. monocytogenes (3-4 log CFU/mL) with other types of bacteria (Bacillus spp., B. cereus, Salmonella Montevideo, Peudomonas aeruginosa, and Yersinia enterocolitica; ca. 3 log CFU/mL each), L. monocytogenes enriched in UVM modified Listeria enrichment broth at 37°C for 24h was successfully detected by the DNA microarray. Results indicate that the DNA microarray can detect L. monocytogenes and distinguish it from other Listeria spp. and other foodborne pathogens in laboratory media and milk. This platform will be useful when developing a DNA microarray to rapidly and simultaneously detect and identify various foodborne pathogens in foods.
    International journal of food microbiology 12/2012; 161(2):134-141. · 3.01 Impact Factor
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    ABSTRACT: Porcine reproductive and respiratory syndrome virus (PRRSV) causes porcine reproductive and respiratory syndrome disease (PRRS), a disease that has a significant and economic impact on the swine industry. In this study, single-stranded DNA (ssDNA) aptamers with high specificity and affinity against VR-2332 strain of PRRSV type II were successfully obtained. Of 19 candidates, the LB32 aptamer was found to be the most specific and sensitive to VR-2332 strain of according to an aptamer-based surface plasmon resonance (SPR) analysis. The detection of VR-2332 of PRRSV type II was successfully accomplished by using the enzyme-linked antibody-aptamer sandwich (ELAAS) method. The detection limit of ELAAS was 4.8 × 10(0) TCID(50)/mL that is comparable to some of previous reports of the PCR-based detection, but does not require any complicated equipments or extra costs. Moreover, this ELAAS-based PRRSV detection showed similar sensitivity for both the VR-2332 samples spiked in diluted swine serum and in buffer. Therefore, this VR-2332 strain-specific aptamer and its assay method with high specificity can be used as an alternative method for the fast and precise detection of PRRSV.
    Analytical Chemistry 11/2012; · 5.70 Impact Factor
  • Joo-Myung Ahn, Man Bock Gu
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    ABSTRACT: In vitro genotoxicity tests detect carcinogens that are thought to act primarily via a mechanism involving direct genetic damage. In this study, we constructed a Geno-Tox cell array chip for genotoxicity testing; eight recombinant bioluminescent bacteria were used to successfully fabricate a Geno-Tox cell array chip. Four well-characterized DNA damage chemicals were selected to determine the capabilities of this Geno-Tox array chip, and each strain of the chip was distinctly responsive, according to the specific mode of genotoxic action. Therefore, this Geno-Tox cell array chip could be implemented to characterize and understand the genotoxic modes of impact; thus, it could be used to provide the genotoxic mechanism of action for new drugs or unknown or newly synthesized chemicals in food and the environment.
    Applied biochemistry and biotechnology 08/2012; 168(4):752-60. · 1.94 Impact Factor
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    ABSTRACT: In the present study, we report on the carbonic anhydrase (CA)-assisted formation of biomineralized calcium carbonate crystalline composites (CCCCs). Ellipsoidal CCCCs, such as calcite polymorphism, in a micro-size range catalyzed by CA were successfully synthesized with polyethylene glycol and magnetic nanoparticles in the constant CO2 pressure controlled chamber, for the first time. CA-assisted CCCCs characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering, showed their crystalline phase with mesoporous property according to Fourier transform infrared and Brunauer–Emmett–Teller area. These CCCCs retained about 43% of free CA esterase activity. Furthermore, the magnet-based separation was also successful for the reuse of the CCCCs. As a result, the CCCCs produced preserved their catalytic activity even after its ten repeated usages, and were stable for more than 50 days under room temperature. The reported method paves the way for novel biomineralization via CA for the formation of functional CA containing nanocomposites and biocatalyst technology applications.
    Green Chemistry 08/2012; 14(8):2216-2220. · 6.83 Impact Factor
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    ABSTRACT: Subtilisin Carlsberg (SC) was immobilized and stabilized on magnetically-separable mesoporous silica (Mag-MSU-F) in the form of nanoscale enzyme reactors (NERs) based on the ship-in-a-bottle mechanism. Stabilized NERs of SC (NER-SC) were freeze-dried and successfully used for the transesterification of N-acetyl-L-phenylalanine ethyl ester with n-propanol in isooctane. Magnetic separation of Mag-MSU-F facilitated the repeated usages of stable NER-SC. This is the first demonstration for the use of stable and magnetically-separable NERs in an organic solvent, which has the potential for environmentally-friendly synthesis using enzymes in organic solvents.
    Green Chemistry 07/2012; 14(7):1884-1887. · 6.83 Impact Factor
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    ABSTRACT: Here, we report the use of an aptamer-immobilized electrospun polystyrene-poly(styrene-co-maleic anhydride) (PS-PSMA) nanofiber as a new aptasensor platform for protein detection. Two thrombin-binding aptamers (TBA29 and TBA15) were used as a model platform to facilitate efficient detection of thrombin in a sandwich manner. Thrombin concentration was measured by fluorescence microscopy and spectroscopy, in which aptamers were labeled with either fluorescein dye or quantum dots. The results indicated that thrombin was captured uniformly on the surface of the nanofiber. Using this sandwich-type biosensor, the minimum detectable concentration of thrombin was 10 pM, with a dynamic range of 0.1-50 nM, when quantum dots were used for labeling. In contrast, the limit of detection was 1 nM, with a dynamic range of 10-200 nM, when using fluorescein dye labeling. This aptamers-on-nanofiber-based biosensor showed 2500-fold higher sensitivity than a 96-microwell plate format, attributed mainly to the large surface area of the nanofibers. In addition, this novel platform also exhibited similar high sensitivity in the detection of exogenously added thrombin in diluted human serum. This aptamers-on-nanofiber system, which is competitive with other sensing platforms and clinically meaningful in terms of its detection limit, is expected to be useful for the detection of various other targets because of its ease of application and manipulation.
    Biosensors & bioelectronics 06/2012; 38(1):302-7. · 5.43 Impact Factor
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    ABSTRACT: A single-stranded DNA (ssDNA) aptamer was successfully developed to specifically bind to nicotinamide phosphoribosyl transferase (Nampt) through systematic evolution of ligands by exponential enrichment (SELEX) and successfully implemented in a gold-interdigitated (GID) capacitor-based biosensor. Surface plasmon resonance (SPR) analysis of the aptamer revealed high specificity and affinity (K(d)=72.52 nM). Changes in surface capacitance/charge distribution or dielectric properties in the response of the GID capacitor surface covalently coupled to the aptamers in response to changes in applied AC frequency were measured as a sensing signal based on a specific interaction between the aptamers and Nampt. The limit of detection for Nampt was 1 ng/ml with a dynamic serum detection range of up to 50 ng/ml; this range includes the clinical requirement for both normal Nampt level, which is 15.8 ng/ml, and Nampt level in type 2 diabetes mellitus (T2DM) patients, which is 31.9 ng/ml. Additionally, the binding kinetics of aptamer-Nampt interactions on the capacitor surface showed that strong binding occurred with increasing frequency (range, 700 MHz-1 GHz) and that the dissociation constant of the aptamer under the applied frequency was improved 120-240 times (K(d)=0.3-0.6 nM) independent on frequency. This assay system is an alternative approach for clinical detection of Nampt with improved specificity and affinity.
    Biosensors & bioelectronics 06/2012; 38(1):233-8. · 5.43 Impact Factor
  • Source
    Sue Hyung Choi, Man Bock Gu
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    ABSTRACT: The genetically-engineeredEscherichia coli strain, DPD2540, which contains afabA::luxCDABE fusion gene, gives a bioluminescent output when membrane fatty acid synthesis is needed. For more practical application of this strain in the field as biosensor, freeze-drying was adopted. A 12% sucrose solution with Luria-Bertani (LB) broth, as determined by the viability after freeze-drying, was found to be the most effective composition for lyophilization solution among various compositions tested. Rapid freezing with liquid nitrogen also gave the best viability after freeze-drying as compared to samples frozen at −70°C and −20°C. The biosensing activities of the cells showed a greater sensitivity when the cells from the exponential phase were freeze-dried. Finally, the optimum temperature for use of the freeze-dried cells in the biosensor field was determined.
    Biotechnology and Bioprocess Engineering 04/2012; 5(3):202-206. · 1.28 Impact Factor

Publication Stats

2k Citations
495.47 Total Impact Points


  • 2002–2014
    • Korea University
      • • College of Life Sciences
      • • Department of Chemical and Biological Engineering
      Sŏul, Seoul, South Korea
  • 2012
    • University of Texas MD Anderson Cancer Center
      • Department of Experimental Radiation Oncology
      Houston, TX, United States
  • 2010–2011
    • Korea Institute of Science and Technology
      • Sensor System Research Center
      Seoul, Seoul, South Korea
    • Korea Research Institute of Chemical Technology
      Daiden, Daejeon, South Korea
  • 2008
    • Sogang University
      • Department of Chemical and Biomolecular Engineering
      Seoul, Seoul, South Korea
    • Hebrew University of Jerusalem
      Yerushalayim, Jerusalem District, Israel
  • 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
      Kwangju, Gwangju, South Korea
  • 2005
    • Pennsylvania State University
      • Department of Chemical Engineering
      University Park, Maryland, United States