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Yang M, Kim DS, Lee TJ, Lee SJ, Lee KG, Choi BG. Polyoxometalate-grafted graphene nanohybrid for electrochemical detection of hydrogen peroxide and glucose. J Colloid Interface Sci 2016; 468:51-56. [DOI: 10.1016/j.jcis.2016.01.047] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 01/18/2016] [Accepted: 01/20/2016] [Indexed: 12/17/2022]
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Chen XW, Lee KG, Eghlidi H, Götzinger S, Sandoghdar V. Enhancing the radiative emission rate of single molecules by a plasmonic nanoantenna weakly coupled with a dielectric substrate. OPTICS EXPRESS 2015; 23:32986-32992. [PMID: 26831966 DOI: 10.1364/oe.23.032986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Enhancing the spontaneous emission of single emitters has been an important subject in nano optics in the past decades. For this purpose, plasmonic nanoantennas have been proposed with enhancement factors typically larger than those achievable with optical cavities. However, the intrinsic ohmic losses of plasmonic structures also introduce an additional nonradiative decay channel, reducing the quantum yield. Here we report on experimental studies of a weakly coupled dielectric substrate and a plasmonic nanoantenna for enhancing the radiative decay rate of single terrylene molecules embedded in an ultrathin organic film. We systematically investigate how the refractive index of the dielectric substrate affects the lifetime and the quantum efficiency and show that the coupled structure could moderately enhance the radiative decay rate while maintaining a high quantum efficiency.
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Yang M, Lee KG, Lee SJ, Lee SB, Han YK, Choi BG. Three-Dimensional Expanded Graphene-Metal Oxide Film via Solid-State Microwave Irradiation for Aqueous Asymmetric Supercapacitors. ACS APPLIED MATERIALS & INTERFACES 2015; 7:22364-22371. [PMID: 26387450 DOI: 10.1021/acsami.5b06187] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Carbon-based electrochemical double-layer capacitors and pseudocapacitors, consisting of a symmetric configuration of electrodes, can deliver much higher power densities than batteries, but they suffer from low energy densities. Herein, we report the development of high energy and power density supercapacitors using an asymmetric configuration of Fe2O3 and MnO2 nanoparticles incorporated into 3D macroporous graphene film electrodes that can be operated in a safe and low-cost aqueous electrolyte. The gap in working potential windows of Fe2O3 and MnO2 enables the stable expansion of the cell voltage up to 1.8 V, which is responsible for the high energy density (41.7 Wh kg(-1)). We employ a household microwave oven to simultaneously create conductivity, porosity, and the deposition of metal oxides on graphene films toward 3D hybrid architectures, which lead to a high power density (13.5 kW kg(-1)). Such high energy and power densities are maintained for over 5000 cycles, even during cycling at a high current density of 16.9 A g(-1).
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Lee KG, Lee S, Chang SJ, Choi BG, Seo J, Sangalang A, Kim DH, Park TJ, Lee MK, Lee SJ, Lee H. Bio-inspired Hierarchical Nanowebs for Green Catalysis. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:4292-4297. [PMID: 26060049 DOI: 10.1002/smll.201403717] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 03/02/2015] [Indexed: 06/04/2023]
Abstract
Bio-inspired 3D hierarchical nanowebs are fabricated using silicon micropillars, carbon nanotubes (CNT), and manganese oxide. The Si pillars act as artificial branches for growing CNTs and the secondary metal coating strengthens the structures. The simple but effective structure provides both chemical and mechanical stability to be used as a green catalyst for recycling waste polymers into raw materials.
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Park JY, Back SH, Chang SJ, Lee SJ, Lee KG, Park TJ. Dopamine-assisted synthesis of carbon-coated silica for PCR enhancement. ACS APPLIED MATERIALS & INTERFACES 2015; 7:15633-40. [PMID: 26112101 DOI: 10.1021/acsami.5b04404] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Polymerase chain reaction (PCR) has become one of the most popular methods to identify genomic information on cells and tissues as well as to solve crimes and check genetic diseases. Recently, the nanomaterials including nanocomposite and nanoparticles have been considered as a next generation of solution to improve both quality and productivity of PCR. Herein, taking into these demands, carbon-coated silica was synthesized using silica particles via polymerization of biocompatible dopamine (PD) to form polydopamine (PDA) film and carbonization of PDA into graphitic structures. For further investigation of the effects of as-prepared silica, PDA-coated silica (PDA silica), and carbonized PDA silica (C-PDA silica), two different types of genes were adopted to investigate the influences of them in the PCR. Furthermore, the strong interaction between the nanocomposites and PCR reagents including polymerase and primers enables regulation of the PCR performance. The effectiveness of the nanocomposites was also confirmed through adopting the conventional PCR and real-time PCR with two different types of DNA as realistic models and different kinds of analytical methods. These findings could provide helpful insight for the potential application in biosensors and biomedical diagnosis.
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Lee KG, Shin S, Kim BI, Bae NH, Lee MK, Lee SJ, Lee TJ. Ultrasonic bonding method for heterogeneous microstructures using self-balancing jig. LAB ON A CHIP 2015; 15:1412-1416. [PMID: 25648348 DOI: 10.1039/c4lc01473a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Perfect sealing of heterogeneous microstructures in plastic-based microfluidic devices is a significant and urgent challenge to be able to apply them in various microfluidic-based applications, including biosensing, biofiltering, chemical reactors and lab-on-a-chip. In this study we report a simple but practical and effective method to bond a microstructure-incorporated microfluidic device using an ultrasonic bonding method. The specially designed hemisphere-shaped jig, which is called a self-balancing jig, provides a free motion in all x, y, and z directions. These unique properties of the jig allow us to precisely adjust and bond the heterogeneous microstructures in the device. A conventional jig shows in solution leakages around the heterogeneous microstructures while the self-balancing jig did not show any leakages in devices. Furthermore, the bonding performance was also confirmed by using a black ink and fluorescent dye solution. The micro-pillar arrays in the device also demonstrated its capability for selective filtering of microbeads. We believe that this technique would be a useful tool for producing microfluidic devices with heterogeneous microstructures.
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Seok S, Shin S, Lee TJ, Jeong JM, Yang M, Kim DH, Park JY, Lee SJ, Choi BG, Lee KG. Multifunctional polyurethane sponge for polymerase chain reaction enhancement. ACS APPLIED MATERIALS & INTERFACES 2015; 7:4699-4705. [PMID: 25664574 DOI: 10.1021/am508101m] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Selective filtering of target biomaterials from impurities is an important task in DNA amplification through polymerase chain reaction (PCR) enhancement and gene identification to save endangered animals and marine species. Conventional gene extraction methods require complicated steps, skilled persons, and expensive chemicals and instruments to improve DNA amplification. Herein, we proposed an alternative method for overcoming such challenges by imparting secondary functionality using commercially available polyurethane (PU) sponges and cost-effective fabrication approaches through polydopamine and polysiloxane coatings. The porous, highly flexible, and chemically modified superhydrophilic and superhydrophobic PU sponges allow large surface areas and mechanically stable frames for effective extraction of genomic DNA through selective filtering of fish tissues and oils. Furthermore, these chemically modified PU sponges allow separation of genes and improvement of PCR for DNA amplification for the identification of fish species. The combination of a simple fabrication method and functionalized PU sponges could be a useful platform for PCR enhancement and gene-based identification of species for practical applications.
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Lee KG, Lath N. Dysphagia lusoria - a rare cause of prolonged Dysphagia. THE MEDICAL JOURNAL OF MALAYSIA 2015; 70:52-53. [PMID: 26032533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A 64-year-old man presented with prolonged history of intermittent dysphagia with sensation of food sticking at his upper chest. Physical examination was unremarkable, and an upper endoscopy did not reveal the underlying cause. On computed tomography scan of thorax, an aberrant right subclavian artery was seen coursing posterior to the esophagus resulting in external compression, which is a typical radiological feature of Dysphagia Lusoria. The pathophysiology, clinical features, imaging features and updated treatment modalities of this rare disease are discussed.
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Jeong JM, Lee KG, Chang SJ, Kim JW, Han YK, Lee SJ, Choi BG. Ultrathin sandwich-like MoS2@N-doped carbon nanosheets for anodes of lithium ion batteries. NANOSCALE 2015; 7:324-329. [PMID: 25407012 DOI: 10.1039/c4nr06215a] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In this work, we report on a simple and scalable process to synthesize the core-shell nanostructure of MoS2@N-doped carbon nanosheets (MoS2@C), in which polydopamine is coated on the MoS2 surface and is then carbonized. An intensive investigation using transmission electron microscopy and Raman spectroscopy reveals that the as-synthesized MoS2@C possesses a nanoscopic and ultrathin layer of MoS2 sheets with a thin and conformal coating of carbon layers (∼ 3 nm). The MoS2@C demonstrates a superior electrochemical performances as an anode material for lithium ion batteries compared to exfoliated MoS2 and bulk MoS2 samples. This unique core-shell structure is capable of delivering an excellent Li(+) ion charging-discharging process as follows: a specific capacity as high as 1239 mA h g(-1), a high rate capability even at a high current rate of 10 A g(-1) while retaining 597 mA h g(-1), and a good cycle stability over 200 cycles at a high current rate of 2 A g(-1).
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Lee KG, Jeong JM, Lee SJ, Yeom B, Lee MK, Choi BG. Sonochemical-assisted synthesis of 3D graphene/nanoparticle foams and their application in supercapacitor. ULTRASONICS SONOCHEMISTRY 2015; 22:422-428. [PMID: 24857684 DOI: 10.1016/j.ultsonch.2014.04.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 04/22/2014] [Accepted: 04/22/2014] [Indexed: 06/03/2023]
Abstract
Graphene and its derivatives have attracted much attention in application of electrochemical devices. Construction of three-dimensional (3D) heterostructured composites is promising for establishing high-performance devices, which enables large surface area, facilitated ion and electron transport, and synergistic effects between multicomponents. Here, we report a simple and general sonochemical-assisted synthesis to prepare various 3D porous graphene/nanoparticle (i.e., Pt, Au, Pd, Ru, and MnO2) foams using colloidal template. The 3D porous network structure of composite foams significantly improves a large surface area of around 550m(2)g(-1) compared to the bare graphene (215m(2)g(-1)). This unique structure of 3D graphene/MnO2 enables further improvement of electrochemical characteristics, compared with bare graphene/MnO2 composite, showing a high specific capacitance of 421Fg(-1) at 0.1Ag(-1), high rate capability (97% retention at 20Ag(-1)), and good cycling performance (97% retention over 1000 cycles). Moreover, electrochemical impedance analysis demonstrates that electron and ion transfer are triggered by 3D porous structure.
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Jeong HY, Baek SH, Chang SJ, Yang M, Lee SJ, Lee KG, Park TJ. A hybrid composite of gold and graphene oxide as a PCR enhancer. RSC Adv 2015. [DOI: 10.1039/c5ra12932j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A hybrid composite of Au/GO was synthesized and its capability as a PCR enhancer was demonstrated.
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Lee KG, Choi BG, Kim BI, Shyu T, Oh MS, Im SG, Chang SJ, Lee TJ, Kotov NA, Lee SJ. Scalable nanopillar arrays with layer-by-layer patterned overt and covert images. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:6119-24. [PMID: 25100005 DOI: 10.1002/adma.201401246] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 06/03/2014] [Indexed: 05/25/2023]
Abstract
Transferring flexible and scalable nano-pillar arrays on a variety of unconventional substrates, including fabric, paper, and metals, is achieved by a single-step replication process using UV-curable polymers. Local alteration of the contact angle on the nanopillar arrays by LBL films creates selectively hidden images. They can be revealed by the breath and used as an innovative anti-counterfeit technology.
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Yang M, Lee KG, Kim JW, Lee SJ, Huh YS, Choi BG. Highly ordered gold-nanotube films for flow-injection amperometric glucose biosensors. RSC Adv 2014. [DOI: 10.1039/c4ra05273k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Seok S, Choi I, Lee KG, Choi BG, Park KJ, Park JY, Kwon OJ, Lee SJ, Kim DH. Dopamine-induced Pt and N-doped carbon@silica hybrids as high-performance anode catalysts for polymer electrolyte membrane fuel cells. RSC Adv 2014. [DOI: 10.1039/c4ra06819j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Park KJ, Lee KG, Seok S, Choi BG, Lee MK, Park TJ, Park JY, Kim DH, Lee SJ. Micropillar arrays enabling single microbial cell encapsulation in hydrogels. LAB ON A CHIP 2014; 14:1873-1879. [PMID: 24706072 DOI: 10.1039/c4lc00070f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Single microbial cell encapsulation in hydrogels is an important task to find valuable biological resources for human welfare. The conventional microfluidic designs are mainly targeted only for highly dispersed spherical bioparticles. Advanced structures should be taken into consideration for handling such aggregated and non-spherical microorganisms. Here, to address the challenge, we propose a new type of cylindrical-shaped micropillar array in a microfluidic device for enhancing the dispersion of cell clusters and the isolation of individual cells into individual micro-hydrogels for potential practical applications. The incorporated micropillars act as a sieve for the breaking of Escherichia coli (E. coli) clusters into single cells in a polymer mixture. Furthermore, the combination of hydrodynamic forces and a flow-focusing technique will improve the probability of encapsulation of a single cell into each hydrogel with a broad range of cell concentrations. This proposed strategy and device would be a useful platform for genetically modified microorganisms for practical applications.
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Lee KG, Park KJ, Seok S, Shin S, Kim DH, Park JY, Heo YS, Lee SJ, Lee TJ. 3D printed modules for integrated microfluidic devices. RSC Adv 2014. [DOI: 10.1039/c4ra05072j] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Direct 3d printing for functional modules and their assembly into an integrated microfluidic device.
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Kim BI, Lee KG, Lee TJ, Choi BG, Park JY, Jung CY, Lee CS, Lee SJ. A continuous tilting of micromolds for fabricating polymeric microstructures in microinjection. LAB ON A CHIP 2013; 13:4321-4325. [PMID: 24056842 DOI: 10.1039/c3lc50494h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate a practical design and integration of multidirectional tilted UV lithography and microinjection molding for microstructure-based microfluidic devices. The previously reported undercut (or T-profile) problem of photoresist causes the imperfect mirror image duplication of the microstructures to the Ni mold. This issue inevitably leads to the unstable molds in the production of microstructure-based microfluidic devices. This study presents a simple route for the successful fabrication of microstructure-based microfluidic devices by multidirectional tilted UV lithography. By changing slope angles of microstructures through tilting the chuck during the UV exposure, the slope angles (up to 30°) around the microstructures allow the effective prevention of the undercut problems of photoresist and facilitate easy releasing of the device with high durability. This technique can be easily used for the production of the microstructure-based microfluidic devices in microanalysis and lab-on-chip applications.
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Jeong JM, Choi BG, Lee SC, Lee KG, Chang SJ, Han YK, Lee YB, Lee HU, Kwon S, Lee G, Lee CS, Huh YS. Hierarchical hollow spheres of Fe2O3 @polyaniline for lithium ion battery anodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:6250-5. [PMID: 23966264 DOI: 10.1002/adma.201302710] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/13/2013] [Indexed: 05/26/2023]
Abstract
Hierarchical hollow spheres of Fe2 O3 @polyaniline are fabricated by template-free synthesis of iron oxides followed by a post in- and exterior construction. A combination of large surface area with porous structure, fast ion/electron transport, and mechanical integrity renders this material attractive as a lithium-ion anode, showing superior rate capability and cycling performance.
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Choi BG, Yang M, Jung SC, Lee KG, Kim JG, Park H, Park TJ, Lee SB, Han YK, Huh YS. Enhanced pseudocapacitance of ionic liquid/cobalt hydroxide nanohybrids. ACS NANO 2013; 7:2453-2460. [PMID: 23397883 DOI: 10.1021/nn305750s] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Development of nanostructured materials with enhanced redox reaction capabilities is important for achieving high energy and power densities in energy storage systems. Here, we demonstrate that the nanohybridization of ionic liquids (ILs, 1-butyl-3-methylimidazolium tetrafluoroborate) and cobalt hydroxide (Co(OH)2) through ionothermal synthesis leads to a rapid and reversible redox reaction. The as-synthesized IL-Co(OH)2 has a favorable, tailored morphology with a large surface area of 400.4 m(2)/g and a mesopore size of 4.8 nm. In particular, the IL-Co(OH)2-based electrode exhibits improvement in electrochemical characteristics compared with bare Co(OH)2, showing a high specific capacitance of 859 F/g at 1 A/g, high-rate capability (∼95% retention at 30 A/g), and excellent cycling performance (∼96% retention over 1000 cycles). AC impedance analysis demonstrates that the introduction of ILs on Co(OH)2 facilitates ion transport and charge transfer: IL-Co(OH)2 shows a higher ion diffusion coefficient (1.06 × 10(-11) cm(2)/s) and lower charge transfer resistance (1.53 Ω) than those of bare Co(OH)2 (2.55 × 10(-12) cm(2)/s and 2.59 Ω). Our density functional theory (DFT) calculations reveal that the IL molecules, consisting of anion and cation groups, enable easier hydrogen desorption/adsorption process, that is, a more favorable redox reaction on the Co(OH)2 surface.
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Kwon BH, Lee KG, Park TJ, Kim H, Lee TJ, Lee SJ, Jeon DY. Continuous in situ synthesis of ZnSe/ZnS core/shell quantum dots in a microfluidic reaction system and its application for light-emitting diodes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:3257-3262. [PMID: 22888060 DOI: 10.1002/smll.201200773] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 06/28/2012] [Indexed: 06/01/2023]
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Lee KG, Cheng MO. Varicella-zoster infection with secondary bacteremia and extensive facial abscesses. THE MEDICAL JOURNAL OF MALAYSIA 2012; 67:529. [PMID: 23770874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Varicella-zoster (chickenpox) infection is a common infectious disease and generally considered to be selflimiting. However, severe bacterial complications associated with the disease have been reported. We describe a case of varicella-zoster infection with secondary Staphylococcus aureus bacteremia, preseptal orbital cellulitis and extensive facial abscesses. She was aggressively treated with intravenous antibiotics and repeated surgical drainage, and eventually made good recovery.
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Lee KG, Indralingam V. A Study of Weekend and Off-hour Effect on Mortality in a Public Hospital in Malaysia. THE MEDICAL JOURNAL OF MALAYSIA 2012; 67:478-482. [PMID: 23770862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
INTRODUCTION Several studies have found higher in-hospital mortality for admissions during weekend or off hours, known as "weekend or off-hour effect". However, data for this on Malaysian populations is limited. This study was conducted to analyze the 3-year mortality trend in a secondary hospital and its relation to time and date of admission. METHODS The clinical data of 126,627 patients admitted to Taiping Hospital from 1st January 2008 to 31st December 2010 obtained via patient registry database of hospital was analyzed. This study compared mortality during weekdays with weekends, office hours (0800-1700) with off hours (1701-0759), and subanalysis of office hours with evening (1701-2259) or night hours (2300-0759), adjusted for age and gender. RESULTS Although the overall staff-to-patient ratio is improving, analyses showed a statistically significant increased risk of mortality for those patients admitted during weekends (OR = 1.22; 95% confidence interval [CI] = 1.14-1.31) or off hours in a weekday (OR = 1.67; 95% CI = 1.57-1.78). In the comparison between time of admission, there was statistically significant increased risk of mortality for admissions during evening hours (OR = 1.44; 95% CI = 1.28-1.62) and night hours (OR = 1.92; 95% CI = 1.71-2.16). Diseases of cardiovascular and respiratory system remained the top two causes of death over the three years. CONCLUSION The risk of mortality is significantly higher as a result of "weekend or off-hour effect". Recognition and intervention addressing these issues will have important implications for the healthcare system setting, hospital staffing and training, quality and timeliness of medical care delivery.
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Lee KG, Hong J, Wang KW, Heo NS, Kim DH, Lee SY, Lee SJ, Park TJ. In vitro biosynthesis of metal nanoparticles in microdroplets. ACS NANO 2012; 6:6998-7008. [PMID: 22769564 DOI: 10.1021/nn302043q] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report the use of a hydrogel polymer, recombinant Escherichia coli cell extracts, and a microdroplet-based microfluidic device to fabricate artificial cellular bioreactors which act as reactors to synthesize diverse metal nanoparticles (NPs). The combination of cell extracts, microdroplet-based microfluidic device, and hydrogel was able to produce a mass amount of artificial cellular bioreactors with uniform size and shape. For the first time, we report the alternating generation of microdroplets through one orifice for the fabrication of the artificial cellular reactors using the cell extract as inner cellular components and hydrogel as an artificial cellular membrane. Notably, the hydrogels were able to protect the encapsulated cell extracts from the surrounding environment and maintain the functionality of cellular component for the further cellular bioreactor applications. Furthermore, the successful applications of the fabricated artificial cellular bioreactors to synthesize various NPs including quantum dots, iron, and gold was demonstrated. By employing this microfluidic technique, the artificial cellular bioreactors could be applicable for the synthesis of diverse metal NPs through simple dipping of the reactors to the metal precursor solutions. Thus, the different size of NPs can be synthesized through controlling the concentration of metal precursors. This artificial cellular bioreactors offer promising abilities to biofriendly ways to synthesis diverse NPs and can be applicable in chemical, biomedical, and bioengineering applications.
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Lee KG, Lee TJ, Jeong SW, Choi HW, Heo NS, Park JY, Park TJ, Lee SJ. Development of a plastic-based microfluidic immunosensor chip for detection of H1N1 influenza. SENSORS 2012; 12:10810-9. [PMID: 23112630 PMCID: PMC3472858 DOI: 10.3390/s120810810] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 07/26/2012] [Accepted: 07/31/2012] [Indexed: 02/04/2023]
Abstract
Lab-on-a-chip can provide convenient and accurate diagnosis tools. In this paper, a plastic-based microfluidic immunosensor chip for the diagnosis of swine flu (H1N1) was developed by immobilizing hemagglutinin antigen on a gold surface using a genetically engineered polypeptide. A fluorescent dye-labeled antibody (Ab) was used for quantifying the concentration of Ab in the immunosensor chip using a fluorescent technique. For increasing the detection efficiency and reducing the errors, three chambers and three microchannels were designed in one microfluidic chip. This protocol could be applied to the diagnosis of other infectious diseases in a microfluidic device.
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Park G, Bartolome L, Lee KG, Lee SJ, Kim DH, Park TJ. One-step sonochemical synthesis of a graphene oxide-manganese oxide nanocomposite for catalytic glycolysis of poly(ethylene terephthalate). NANOSCALE 2012; 4:3879-3885. [PMID: 22592889 DOI: 10.1039/c2nr30168g] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Ultrasound-assisted synthesis of a graphene oxide (GO)-manganese oxide nanocomposite (GO-Mn(3)O(4)) was conducted without further modification of GO or employing secondary materials. With the GO nanoplate as a support, potassium permanganate oxidizes the carbon atoms in the GO support and gets reduced to Mn(3)O(4). An intensive ultrasound method could reduce the number of reaction steps and temperature, enhance the reaction rate and furthermore achieve a Mn(3)O(4) phase. The composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The coverage and crystallinity of Mn(3)O(4) were controlled by changing the ratio of permanganate to GO dispersion. The synthesized nanocomposite was used as a catalyst for poly(ethylene terephthalate) (PET) depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET). The highest monomer yield of 96.4% was obtained with the nanocomposite containing the lowest amount of Mn(3)O(4), while PET glycolysis with the Mn(3)O(4) without GO yielded 82.7% BHET.
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