Publications by authors named "Taewook Kang"

89 Publications

Water-Wettable Open Plasmonic Nanocavities for Ultrasensitive Molecular Detections in Multiple Phases.

Nano Lett 2021 07 13;21(14):6194-6201. Epub 2021 Jul 13.

Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, Korea.

Plasmonic nanocavities between metal nanoparticles on metal films are either hydrophobic or fully occupied by nonmetallic spacers, preventing molecular diffusion into electromagnetic hotspots. Here we realize water-wettable open plasmonic cavities by devising gold nanoparticle with site-selectively grown ultrathin dielectric layer-on-gold film structures. We directly confirm that hydrophilic dielectric layers of SiO or TiO, which are formed only at the tips of gold nanorod via precise temperature control, render sub-10 nm cavities open to the surroundings and completely water-wettable. Simulations reveal that spontaneous wetting in our cavities is driven by the presence of tip-selective hydrophilic layer and tendency of minimizing high energy air/water interface inside the cavities. Our plasmonic cavities show significant Raman enhancement of up to 4 orders of magnitude higher than those of conventional ones for molecules in various media. Our findings will offer new opportunities for sensing applications of plasmonic nanocavities and have huge impacts on cavity plasmonics.
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http://dx.doi.org/10.1021/acs.nanolett.1c01872DOI Listing
July 2021

Sensitive and Direct Optical Monitoring of Release and Cellular Uptake of Aqueous CO from CO-Releasing Molecules.

Anal Chem 2021 Jul 8;93(28):9927-9932. Epub 2021 Jul 8.

Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, Korea.

Dynamics of release and cellular uptake of aqueous CO from CO-releasing molecules (CORMs) significantly affect signaling and cell viability. So far, it has been mainly observed by IR, UV-visible, and fluorescence techniques, which suffer from poor sensitivity and slow response time. Here, we show how to directly probe the mass transfer of aqueous CO from CORMs to cells using a fluidic chamber integrated with live cells and Raman reporters of large-area [email protected] core-shell nanoparticle assembly to emulate a physiologically relevant microenvironment. We sensitively and directly detect CO release from trace CORMs of as low as 100 nM by measuring the Raman transitions of CO rapid chemisorption onto the surface of the [email protected] nanoparticles. By using our method, we successfully observe the dynamics of CO release from CORM-2 despite its very short half-life. We also reveal that the initial rate of CO release from CORM-3 is dramatically decreased by tens to hundreds of times when exposed to physiologically relevant pH variations from 7.4 to 2.5, which can be attributed to the acid hydrolysis of the CO ligand. CORM-2 tends to quickly release CO regardless of pH, probably because of its rapid cleavage into two monomeric Ru complexes by the co-solvent. The decrease in the initial rate at lower temperatures is more significant for CORM-3 than for CORM-2. Finally, we observe that the cellular uptake of aqueous CO from CORM-3 by lung cancer cells is approximately 2 times higher than that of normal lung cells.
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http://dx.doi.org/10.1021/acs.analchem.1c02216DOI Listing
July 2021

Effect of meteorological factors and air pollutants on fractures: a nationwide population-based ecological study.

BMJ Open 2021 06 11;11(6):e047000. Epub 2021 Jun 11.

Artificial Intelligence and Big-Data Convergence Center, Gachon University Gil Medical Center, Incheon, South Korea

Objective: To determine the association of meteorological factors and air pollutants (MFAPs) with fracture and to estimate the effect size/time lag.

Design: This is a nationwide population-based ecological study from 2008 to 2017.

Setting: Eight large metropolitan areas in Korea.

Participants: Of 8 093 820 patients with fractures reported in the Korea National Health Insurance database, 2 129 955 were analysed after the data set containing patient data (age, sex and site of fractures) were merged with MFAPs. Data on meteorological factors were obtained from the National Climate Data Center of the Korea Meteorological Administration. Additionally, data on air pollutants (atmospheric particulate matter ≤2.5 µm in diameter (PM), PM, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide) were obtained from the Air Korea database.

Primary And Secondary Outcome Measures: We hypothesised that there would be an association between MFAPs and the incidence of fracture. A generalised additive model was used while factoring in the non-linear relationship between MFAPs and fractures as well as a time lag ≤7 days. Multivariate analysis was performed. Backward elimination with an Akaike information criterion was used to fit the multivariate model.

Results: Overall, in eight urban areas, 2 129 955 patients with fractures were finally analysed. These included 370 344, 187 370, 173 100, 140 358, 246 775, 6501, 228 346, 57 183 and 719 978 patients with hip, knee, shoulder, elbow, wrist, hand, ankle, foot and spine fractures, respectively. Various MFAPs (average temperature, daily rain, wind speed, daily snow and PM) showed significant association with fractures, with positive correlations at time lags 7, 5-7, 5-7, 3-7 and 6-7 days, respectively.

Conclusions: Various MFAPs could affect the occurrence of fractures. The average temperature, daily rain, wind speed, daily snow and PM were most closely associated with fracture. Thus, improved public awareness on these MFAPs is required for clinical prevention and management of fractures.
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http://dx.doi.org/10.1136/bmjopen-2020-047000DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8202114PMC
June 2021

Predicting postoperative complications in patients undergoing lumbar spinal fusion by using the modified five-item frailty index and nutritional status.

Bone Joint J 2020 Dec;102-B(12):1717-1722

Department of Orthopaedics Korea University College of Medicine, Anam Hospital, Seoul, Korea.

Aims: As the population ages and the surgical complexity of lumbar spinal surgery increases, the preoperative stratification of risk becomes increasingly important. Understanding the risks is an important factor in decision-making and optimizing the preoperative condition of the patient. Our aim was to determine whether the modified five-item frailty index (mFI-5) and nutritional parameters could be used to predict postoperative complications in patients undergoing simple or complex lumbar spinal fusion.

Methods: We retrospectively reviewed 584 patients who had undergone lumbar spinal fusion for degenerative lumbar spinal disease. The 'simple' group (SG) consisted of patients who had undergone one- or two-level posterior lumbar fusion. The 'complex' group (CG) consisted of patients who had undergone fusion over three or more levels, or combined anterior and posterior surgery. On admission, the mFI-5 was calculated and nutritional parameters collected.

Results: Complications occurred in 9.3% (37/396) of patients in the SG, and 10.1% (19/167) of patients in the CG. In the SG, the important predictors of complications were age (odds ratio (OR) 1.036; p = 0.002); mFI-5 (OR 1.026 to 2.411, as score increased to 1 ≥ 2 respectively p = 0.023); albumin (OR 11.348; p < 0.001); vitamin D (OR 2.185; p = 0.032); and total lymphocyte count (OR 1.433; p = 0.011) . In the CG, the predictors of complications were albumin (OR 9.532; p = 0.002) and vitamin D (OR 3.815; p = 0.022).

Conclusion: The mFI-5 and nutritional status were effective predictors of postoperative complications in the SG, but only nutritional status was successful in predicting postoperative complications in the CG. The complexity of the surgery, as well as the preoperative frailty and nutritional status of patients, should be considered when determining if it is safe to proceed with lumbar spinal fusion. Cite this article: 2020;102-B(12):1717-1722.
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http://dx.doi.org/10.1302/0301-620X.102B12.BJJ-2020-0874.R1DOI Listing
December 2020

Control of B Cell Lymphoma by Gammaherpesvirus-Induced Memory CD8 T Cells.

J Immunol 2020 12 13;205(12):3372-3382. Epub 2020 Nov 13.

Microbiology and Immunology Department, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756; and

Persistent infection with gammaherpesviruses (γHV) can cause lymphomagenesis in immunocompromised patients. Murine γHV-68 (MHV-68) is an important tool for understanding immune factors contributing to γHV control; however, modeling control of γHV-associated lymphomagenesis has been challenging. Current model systems require very long incubation times or severe immune suppression, and tumor penetrance is low. In this report, we describe the generation of a B cell lymphoma on the C57BL/6 background, which is driven by the Myc oncogene and expresses an immunodominant CD8 T cell epitope from MHV-68. We determined MHV-68-specific CD8 T cells in latently infected mice use either IFN-γ or perforin/granzyme to control γHV-associated lymphoma, but perforin/granzyme is a more potent effector mechanism for lymphoma control than IFN-γ. Consistent with previous reports, CD4-depleted mice lost control of virus replication in persistently infected mice. However, control of lymphoma remained intact in the absence of CD4 T cells. Collectively, these data show the mechanisms of T cell control of B cell lymphoma in γHV-infected mice overlap with those necessary for control of virus replication, but there are also important differences. This study establishes a tool for further dissecting immune surveillance against, and optimizing adoptive T cell therapies for, γHV-associated lymphomas.
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http://dx.doi.org/10.4049/jimmunol.2000734DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7924667PMC
December 2020

Liposome/gold hybrid nanoparticle encoded with CoQ10 (LGNP-CoQ10) suppressed rheumatoid arthritis via STAT3/Th17 targeting.

PLoS One 2020 6;15(11):e0241080. Epub 2020 Nov 6.

Rheumatism Research Center, Catholic Research Institute of Medical Science, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.

Coenzyme Q10 (CoQ10), also known as ubiquinone, is a fat-soluble antioxidant. Although CoQ10 has not been approved as medication by the Food and Drug Administration, it is widely used in dietary supplements. Some studies have shown that CoQ10 has anti-inflammatory effects on various autoimmune disorders. In this study, we investigated the anti-inflammatory effects of liposome/gold hybrid nanoparticles encoded with CoQ10 (LGNP-CoQ10). Both CoQ10 and LGNP-CoQ10 were administered orally to mice with collagen-induced arthritis (CIA) for 10 weeks. The inflammation pathology of joint tissues of CIA mice was then analyzed using hematoxylin and eosin and Safranin O staining, as well as immunohistochemistry analysis. We obtained immunofluorescence staining images of spleen tissues using confocal microscopy. We found that pro-inflammatory cytokines were significantly decreased in LGNP-CoQ10 injected mice. Th17 cell and phosphorylated STAT3-expressed cell populations were also decreased in LGNP-CoQ10 injected mice. When human peripheral blood mononuclear cells (PBMCs) were treated with CoQ10 and LGNP-CoQ10, the IL-17 expression of PBMCs in the LGNP-CoQ10-treated group was significantly reduced. Together, these results suggest that LGNP-CoQ10 has therapeutic potential for the treatment of rheumatoid arthritis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0241080PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7647073PMC
December 2020

Assessing changes in cervical epidural pressure during biportal endoscopic lumbar discectomy.

J Neurosurg Spine 2020 Oct 30:1-7. Epub 2020 Oct 30.

Objective: Biportal endoscopic spinal surgery has been performed for several years, and its effectiveness is well known; however, no studies on its safety, specifically intracranial pressure, have been conducted to date. The authors sought to evaluate the effect of biportal endoscopic lumbar discectomy on intracranial pressure by monitoring cervical epidural pressure (CEP) changes throughout the procedure.

Methods: Twenty patients undergoing single-level biportal endoscopic lumbar discectomy were enrolled in this study. CEPs were monitored throughout the procedure, consisting of phase 1, establishing the surgical portal and working space; phase 2, performing decompression and discectomy; and phase 3, turning off the fluid irrigation system. After discectomy was completed, the authors evaluated changes in CEP as the irrigation pressure increased serially by adding phase 4, increasing irrigation pressure with outflow open; and phase 5, increasing irrigation pressure with outflow closed.

Results: The mean baseline CEP was measured as 16.65 mm Hg. In phase 1, the mean CEP was 17.3 mm Hg, which was not significantly different from the baseline CEP. In phase 2, the mean CEP abruptly increased up to 35.1 mm Hg when the epidural space was first connected with the working space, followed by stabilization of the CEP at 31.65 mm Hg. In phase 4, the CEP increased as the inflow pressure increased, showing a linear correlation, but not in phase 5. No patients experienced neurological complications.

Conclusions: It is important to ensure that irrigation fluid is not stagnant and is maintained continuously. More attention must be paid to keeping pressures low when opening the epidural space.
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http://dx.doi.org/10.3171/2020.6.SPINE20586DOI Listing
October 2020

Acute Calcific Tendinitis of the Longus Colli.

Pain Med 2020 08;21(8):1706-1708

Korea University Medical Center, Seoul, Korea.

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http://dx.doi.org/10.1093/pm/pnaa055DOI Listing
August 2020

Direct Optical and Ultrasensitive Probing of Nonequilibrium Dynamics of Carbon Monoxide in an Aqueous Phase during Biochemical Reactions.

ACS Sens 2020 07 14;5(7):2221-2229. Epub 2020 Jul 14.

Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, Korea.

Detection of trace carbon monoxide (CO) dissolved in an aqueous phase is key for monitoring and optimizing biological and chemical gas conversions. So far, irrespective of the nonequilibrium nature of these conversion processes, because of low water solubility of CO, such detection has been performed indirectly, under the assumption of thermodynamic equilibrium, by the combination of chromatographic measurement of relatively abundant CO in a gas phase and Henry's law. Direct and sensitive detection of dissolved CO under nonequilibrium has not been explored yet. Here, we report the direct, ultrasensitive, and real-time monitoring of nonequilibrium dynamics of CO in an aqueous phase during biochemical conversions by devising miniaturized fluidic reactors with built-in CO-specific optical probes surface-enhanced Raman spectroscopy. As the sensitive and selective probes, we fabricate ligand-free [email protected] core-shell nanoparticle monolayers to maximize the Raman signal of single CO in the aqueous phase. We confirm that under equilibrium conditions, aqueous and gaseous CO concentrations estimated by our method are in good agreement with those measured directly and indirectly by gas chromatography (GC). We show that our probe can detect the aqueous CO concentrations as low as 0.01% with high signal reproducibility, which is 200-fold more sensitive than that achieved by infrared spectroscopy. Finally, we successfully observe the nonequilibrium dynamics of the aqueous CO during biochemical reactions, which cannot be sensed by other detection methods including even indirect measurement by GC. We anticipate that our method can be widely applied not only for monitoring of biochemical gas reactions on multiple scales from a large reactor to a single-molecule level but also for molecular imaging of biological systems.
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http://dx.doi.org/10.1021/acssensors.0c00858DOI Listing
July 2020

Incidence & Risk Factors of Postoperative Delirium After Spinal Surgery in Older Patients.

Sci Rep 2020 06 8;10(1):9232. Epub 2020 Jun 8.

Department of Orthopaedics, Korea University College of Medicine, Anam Hospital, Seoul, Korea.

Although postoperative delirium is a common complication in older patients, few papers have described risk factors after of spinal surgery. The purpose of this study was to analyze various perioperative risk factors for delirium after spinal surgery in older patients. This study was performed on retrospective data collection with prospective design. We analyzed 138 patients over 65 years of age who underwent spinal surgery. Preoperative factors were cognitive function (Mini-Mental State Examination-Korean (MMSE-K) and the Korean version of the Delirium Rating Scale-Revised-98 (K-DRS 98)), age, sex, type of admission, American Society of Anesthesiologist classification, metabolic equivalents, laboratory findings, visual analog scale, and Oswestry Disability Index. Intraoperative factors were operation time, blood loss, and type of procedure. Postoperative factors were blood transfusion and type of postoperative pain control. Postoperative delirium developed in 25 patients (18.16%). Patients were divided into two groups: Group with delirium (group A) and group without delirium (group B). MMSE-K scores in Group A were significantly lower than in Group B (p < 0.001). K-DRS 98 scores were significantly higher in Group A than Group B (p < 0.001). The operation time was longer in Group A than Group B (p = 0.059). On multivariate regression analysis, the odds ratio of K-DRS 98 was 2.43 (p = 0.010). After correction for the interaction between age and MMSE-K, patients younger than 73 years old had a significantly lower incidence of delirium with higher MMSE-K score (p = 0.0014). Older age, low level of preoperative cognitive function, long duration of surgery, and transfusion were important risk factors of postoperative delirium after spinal surgery. It is important to recognize perioperative risk factors and manage appropriately.
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http://dx.doi.org/10.1038/s41598-020-66276-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7280299PMC
June 2020

Biportal endoscopic discectomy for high-grade migrated lumbar disc herniation.

J Neurosurg Spine 2020 May 15:1-6. Epub 2020 May 15.

Objective: Although endoscopic procedures for lumbar disc herniation have improved greatly and offer many advantages, the indications are limited mostly to nonmigrated or low-grade migrated disc herniation. Endoscopic application in migrated disc herniation cases is still challenging and technically demanding. The goal in this study was to determine the feasibility of biportal endoscopic discectomy for removal of high-grade migrated disc herniation.

Methods: A retrospective review was performed in 262 patients who had undergone biportal endoscopic discectomy after the diagnosis of lumbar herniated disc. According to preoperative MRI findings, disc herniation was classified into 5 zones based on the direction and distance from the disc space. Patients were divided into 2 groups-a high-grade migration group and a low-grade migration group. Clinical outcomes were evaluated using the Oswestry Disability Index (ODI), visual analog scale (VAS), and modified Macnab criteria, and those outcomes and operation time were compared between the 2 groups.

Results: There were 10 patients with "high-grade up," 8 with "low-grade up," 98 with disc-level, 102 with "low-grade down," and 44 with "high-grade down" herniation, thereby yielding 54 patients in the high-grade group and 208 in the low-grade group. Demographic data for the 2 groups showed no significant difference. There was no significant difference between the 2 groups in ODI, VAS, and modified Macnab criteria. Operation time between the 2 groups was not significantly different (60.74 vs 65.63 minutes, p > 0.05).

Conclusions: Biportal endoscopic discectomy can be effective for high-grade migrated lumbar disc herniation with no prolonged operation time and satisfactory clinical outcomes.
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http://dx.doi.org/10.3171/2020.2.SPINE191452DOI Listing
May 2020

Characterization of Signaling Pathways Associated with Pancreatic β-cell Adaptive Flexibility in Compensation of Obesity-linked Diabetes in Mice.

Mol Cell Proteomics 2020 06 7;19(6):971-993. Epub 2020 Apr 7.

Protein research group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark. Electronic address:

The onset of obesity-linked type 2 diabetes (T2D) is marked by an eventual failure in pancreatic β-cell function and mass that is no longer able to compensate for the inherent insulin resistance and increased metabolic load intrinsic to obesity. However, in a commonly used model of T2D, the mouse, β-cells have an inbuilt adaptive flexibility enabling them to effectively adjust insulin production rates relative to the metabolic demand. Pancreatic β-cells from these animals have markedly reduced intracellular insulin stores, yet high rates of (pro)insulin secretion, together with a substantial increase in proinsulin biosynthesis highlighted by expanded rough endoplasmic reticulum and Golgi apparatus. However, when the metabolic overload and/or hyperglycemia is normalized, β-cells from mice quickly restore their insulin stores and normalize secretory function. This demonstrates the β-cell's adaptive flexibility and indicates that therapeutic approaches applied to encourage β-cell rest are capable of restoring endogenous β-cell function. However, mechanisms that regulate β-cell adaptive flexibility are essentially unknown. To gain deeper mechanistic insight into the molecular events underlying β-cell adaptive flexibility in β-cells, we conducted a combined proteomic and post-translational modification specific proteomic (PTMomics) approach on islets from mice and wild-type controls (WT) with or without prior exposure to normal glucose levels. We identified differential modifications of proteins involved in redox homeostasis, protein refolding, K48-linked deubiquitination, mRNA/protein export, focal adhesion, ERK1/2 signaling, and renin-angiotensin-aldosterone signaling, as well as sialyltransferase activity, associated with β-cell adaptive flexibility. These proteins are all related to proinsulin biosynthesis and processing, maturation of insulin secretory granules, and vesicular trafficking-core pathways involved in the adaptation of insulin production to meet metabolic demand. Collectively, this study outlines a novel and comprehensive global PTMome signaling map that highlights important molecular mechanisms related to the adaptive flexibility of β-cell function, providing improved insight into disease pathogenesis of T2D.
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http://dx.doi.org/10.1074/mcp.RA119.001882DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7261816PMC
June 2020

Efficient Luminescence of SrSiN:Eu nanophosphor and its film applications to LED and Solar cell as a downconverter.

Sci Rep 2020 Jan 30;10(1):1475. Epub 2020 Jan 30.

Interdisciplinary Program of LED Convergence, Pukyong National University, Busan, 48513, Republic of Korea.

Here we present the synthesis of the efficient nanophosphor SrSiN:Eu (D = 144 nm) by a simple milling approach, its strong Rayleigh scattering, and its film applications to white LED and silicon solar cell as a downshifting medium. The final nanophosphor product showed the quantum efficiency comparable to the bulk phosphor which is, to our knowledge, the highest record of nitride nanophosphors. Especially the nanophosphor showed the more tail emission at the shorter-wavelength side of the emission spectrum and the faster thermal quenching with the more spectral broadening along with the temperature due to Rayleigh scattering. Also the lowering in the excitation spectrum was observed due to lower absorbance. Finally, the nanophosphor-dispersed polyvinyl alcohol (PVA) film was made, and its applications to white LED and silicon solar cell as a downshifting medium demonstrated that it gave the high color rendering property in white LED in spite of still lower luminous efficiency, and it caused the increase in efficiency of silicon solar cell.
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http://dx.doi.org/10.1038/s41598-020-58469-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6992749PMC
January 2020

Spinal epidural abscess successfully treated with biportal endoscopic spinal surgery.

Medicine (Baltimore) 2019 Dec;98(50):e18231

Department of Orthopaedics, Korea University College of Medicine, Seoul, South Korea.

Surgical decompression and antibiotic therapy are the treatments of choice for patients with spinal epidural abscess (SEA). Surgical treatment included decompression, evacuation of abscess, and debridement. Recently, minimal invasive surgery has been introduced more widely, and biportal endoscopic spinal surgery have shown satisfactory clinical outcomes compared with traditional open surgery. The purpose of this study was to evaluate the efficacy of biportal endoscopic spinal surgery for the treatment of SEA .From January 2016 to June 2017, 13 patients who underwent biportal endoscopic spinal surgery under the diagnosis of SEA were retrospectively enrolled in this study. The surgical indications of the enrolled patients included SEA with or without early stage spondylodiscitis who had neurological symptoms. Periopertaive data and clinical outcomes were assessed by regular serologic testing, imaging studies, physical examination, visual analog scale, Oswestry Disability Index and modified Macnab criteria.Offending pathogens were identified in seven (54%) of 13 biopsy specimens. Appropriate intravenous antibiotics for the identified pathogens isolated from infected tissue biopsy cultures were administrated to patients for at least 30 days. All patients reported satisfactory relief of pain and neurological symptoms after surgery. No surgery-related complications and recurrences were found after 2 years follow up.Biportal endoscopic spinal surgery may be an effective alternative to traditional open surgical decompression for the treatment of SEA.
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http://dx.doi.org/10.1097/MD.0000000000018231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6922448PMC
December 2019

Optical Detection of Small Metabolites for Biological Gas Conversion by using Metal Nanoparticle Monolayers Produced by Capillary-Assisted Transfer.

Anal Chem 2019 10 26;91(20):13152-13157. Epub 2019 Sep 26.

Department of Life Science , University of Seoul , Seoul 02504 , Korea.

Detection of small metabolites is essential for monitoring and optimizing biological gas conversion. Currently, such detection is typically done by liquid chromatography with offline sampling. However, this method often requires large equipment with multiple separation columns and is at risk of serious microbial contamination during sampling. Here we propose real-time optical detection of small metabolites using uniform plasmonic nanoparticles monolayers produced by capillary-assisted transfer. We reproducibly fabricate metal nanoparticles monolayers with a diameter of ∼1 mm for the detection of acetate, butyrate, and glucose by a glass capillary tube. Metal nanoparticles monolayers are not only uniform in terms of average interparticle distance but also structurally stable under dynamic fluidic conditions. The monolayers resistant to fluid shear stress with surface-enhanced Raman scattering are able to reversibly monitor the concentration of acetate and sensitively detect acetate and glucose at levels as low as 10 μM, which is more than 2 orders of magnitude lower than the concentration range of typical biological gas conversion. In addition, structurally similar metabolites such as acetate and butyrate, when mixed, become distinguishable by our method.
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http://dx.doi.org/10.1021/acs.analchem.9b03439DOI Listing
October 2019

Active Surface Hydrophobicity Switching and Dynamic Interfacial Trapping of Microbial Cells by Metal Nanoparticles for Preconcentration and In-Plane Optical Detection.

Nano Lett 2019 10 5;19(10):7449-7456. Epub 2019 Sep 5.

Department of Chemical and Biomolecular Engineering , Sogang University , Seoul , 04107 , Korea.

The surface hydrophobicity of a microbial cell is known to be one of the important factors in its adhesion to an interface. To date, such property has been altered by either genetic modification or external pH, temperature, and nutrient control. Here we report a new strategy to engineer a microbial cell surface and discover the unique dynamic trapping of hydrophilic cells at an air/water interface via hydrophobicity switching. We demonstrate the surface transformation and hydrophobicity switching of () by metal nanoparticles. By employing real-time dark-field imaging, we directly observe that hydrophobic gold nanoparticle-coated , unlike its naked counterpart, is irreversibly trapped at the air/water interface because of elevated hydrophobicity. We show that our surface transformation method and resulting dynamic interfacial trapping can be generally extended to Gram-positive bateria, Gram-negative bacteria, and fungi. As the dynamic interfacial trapping allows the preconcentration of microbial cells, high intensity of scattering light, in-plane focusing, and near-field enhancement, we are able to directly quantify as low as 1.0 × 10 cells/ml by using a smartphone with an image analyzer. We also establish the identification of different microbial cells by the characteristic Raman transitions directly measured from the interfacially trapped cells.
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http://dx.doi.org/10.1021/acs.nanolett.9b03163DOI Listing
October 2019

Proteomic Analysis of Restored Insulin Production and Trafficking in Obese Diabetic Mouse Pancreatic Islets Following Euglycemia.

J Proteome Res 2019 09 31;18(9):3245-3258. Epub 2019 Jul 31.

Protein Research Group, Department of Biochemistry and Molecular Biology , University of Southern Denmark , DK-5230 Odense M , Denmark.

For the treatment of patients with prediabetes or diabetes, clinical evidence has emerged that β-cell function can be restored by glucose-lowering therapeutic strategies. However, little is known about the molecular mechanisms underlying this functional adaptive behavior of the pancreatic β-cell. This study examines the dynamic changes in protein expression and phosphorylation state associated with (pro)insulin production and secretory pathway function mediated by euglycemia to induce β-cell rest in obese/diabetic islet β-cells. Unbiased quantitative profiling of the protein expression and phosphorylation events that occur upon β-cell adaption during the transition from hyperglycemia to euglycemia was assessed in isolated pancreatic islets from obese diabetic and wild-type (WT) mice using quantitative proteomics and phosphoproteomics together with bioinformatics analysis. Dynamic changes in the expression and phosphorylation of proteins associated with pancreatic β-cell (pro)insulin production and complementary regulated-secretory pathway regulation were observed in obese diabetic islets in a hyperglycemic environment, relative to WT mouse islets in a normal euglycemic environment, that resolved when isolated islets were exposed to euglycemia for 12 h in vitro. By similarly treating WT islets in parallel, the effects of tissue culture could be mostly eliminated and only those changes associated with resolution by euglycemia were assessed. Among such regulated protein phosphorylation-dependent signaling events were those associated with COPII-coated vesicle-dependent ER exit, ER-to-Golgi trafficking, clathrin-coat disassembly, and a particular association for the luminal Golgi protein kinase, FAM20C, in control of distal secretory pathway trafficking, sorting, and granule biogenesis. Protein expression and especially phosphorylation play key roles in the regulation of (pro)insulin production, correlative secretory pathway trafficking, and the restoration of β-cell secretory capacity in the adaptive functional β-cell response to metabolic demand, especially that mediated by glucose.
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http://dx.doi.org/10.1021/acs.jproteome.9b00160DOI Listing
September 2019

Bone union after spinal fusion surgery using local bone in long-term bisphosphonate users: a prospective comparative study.

Arch Osteoporos 2019 06 29;14(1):74. Epub 2019 Jun 29.

Department of Orthopaedics, Korea University College of Medicine, Anam Hospital, Inchonro 73, Seongbukgu, Seoul, 02841, South Korea.

Bisphosphonates are the most commonly used drugs for osteoporosis and long-term use of bisphosphonates may affect fusion rate after spinal fusion surgery. There was significant delayed union after 6 months in long-term bisphosphonates users; however, there were no significant difference in fusion rate of long-term bisphosphonate users. Therefore, spinal fusion surgery should not be hesitated in long-term bisphosphonates users.

Purpose: Bisphosphonates (BPs) are the most popular class of drugs for treatment of postmenopausal osteoporosis. Long-term use of BPs may also inhibit the spinal fusion process after posterior lumbar interbody fusion (PLIF). We compared bone fusion rates of long-term BPs users and non-users after undergoing spinal fusion surgery.

Methods: A total of 97 postmenopausal women who were candidates for single-level PLIF were recruited from 2015 to 2016. Participants were divided into two groups, with 63 patients in a long-term BPs user group and 34 patients in a non-user group. Serum C-terminal cross-linking telopeptide (CTX) levels were checked for bone resorption markers. Bone fusion rates were calculated at 6 months and 1 and 2 years after the surgery. Clinical outcomes were measured using the Oswestry Disability Index (ODI) and visual analog scale (VAS).

Results: Serum CTX level was dramatically decreased in the long-term BPs user group (p < 0.05). Fusion rates at 6 months after surgery were 42% in the non-user group and 26% in the long-term BPs user group (p = 0.035). However, fusion rates were 82% in the long-term BPs user group and 87% in the non-user group at 2 years after surgery (p > 0.05). There was no significant difference between the two groups in ODI or VAS.

Conclusions: Even though there was significant delayed union after 6 months in long-term BPs users, at the 2-year postoperative follow-up, there was no significant difference in bone fusion rate between the two groups. Long-term BPs users showed fusion rates greater than 80% and clinical outcome improvements that were comparable to those in non-users. No significant effect on fusion rate after PLIF was found in long-term BPs users.
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http://dx.doi.org/10.1007/s11657-019-0628-8DOI Listing
June 2019

Patient Blood Management During Lumbar Spinal Fusion Surgery.

World Neurosurg 2019 Oct 26;130:e566-e572. Epub 2019 Jun 26.

Department of Orthopaedics, Korea University College of Medicine, Anam Hospital, Seoul, Korea.

Objective: Patient blood management (PBM) is defined as treatment of a patient who is at risk of transfusion to minimize the need for transfusion and improve the probability of an optimal clinical outcome. We performed the present study to examine the effects of PBM in spinal fusion surgery.

Methods: A total of 154 patients who had undergone 1- and 2-level posterior lumbar interbody fusion for degenerative lumbar disease were included. We retrospectively reviewed the data from 101 patients from 2012 to 2016 as the pre-PBM group. We recruited 53 patients from 2017 to 2018 for the post-PBM group. Intravenous iron was administered 2-4 weeks before surgery, and intravenous tranexamic acid was administered intraoperatively in the post-PBM group. The primary outcome was the reduction of hemoglobin (Hb). The secondary outcomes included perioperative blood loss, Hemovac drain output, postoperative transfusion, complications, and length of hospital stay.

Results: Intravenous iron was administered 17.4 days before surgery in the post-PBM group. The reduction in Hb was not significantly different statistically between the 2 groups (3.06 vs. 3.33 g/dL; P > 0.05). Of the 101 patients in the pre-PBM group, 24 (24%) underwent transfusion. In contrast, no patient in the post-PBM group had required a transfusion (P < 0.001). The average hospital stay was 10.15 days in the pre-PBM group and 8.33 days in the post-PBM group (P = 0.02). The average operative time was 146 minutes in the pre-PBM group and 133 minutes in the post-PBM group (P = 0.03). The Hb decrease and total Hemovac drain output did not differ significantly between the 2 groups.

Conclusions: Implementation of PBM is an effective strategy for reducing the rate of transfusion in patients undergoing lumbar spinal fusion surgery without significant complications.
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http://dx.doi.org/10.1016/j.wneu.2019.06.153DOI Listing
October 2019

Is biportal technique/endoscopic spinal surgery satisfactory for lumbar spinal stenosis patients?: A prospective randomized comparative study.

Medicine (Baltimore) 2019 May;98(18):e15451

Department of Orthopaedics, Korea University College of Medicine, Seoul, Republic of Korea.

Background: Lumbar decompressive surgery is a standard surgical technique for lumbar spinal stenosis. Many new surgical techniques have been introduced, ranging from open surgery to minimally invasive procedures. Minimally invasive surgical techniques are preferred because patients experience less postoperative pain and shorter hospital stays. However, the success rate of minimally invasive techniques have been controversial. The object of this study was to assess the feasibility of spinal decompression using biportal technique/endoscopic surgery compared with microscopic surgery.

Methods: Seventy lumbar spinal stenosis patients undergoing laminectomy were included in this study. A number table was used to randomize the patients into two groups: a biportal technique/endoscopic surgery group (BG-36) and a microscopic surgery group (OG-34). One surgeon performed either biportal technique/endoscopic decompression or microscopic decompression using a tubular retractor, depending on the group to which the patient was randomized. Perioperative data and clinical outcomes at postoperative 6 months were collected and analyzed.

Results: The demographic data and level of surgery were comparable between the two groups. A shorter operation time (36 ± 11 vs 54 ± 9 min), less hemovac drain output (25.5 ± 15.8 vs 53.2 ± 32.1 ml), less opioid usage (2.3 ± 0.6 vs 6.5 ± 2.5 T) and shorter hospital stay (1.2 ± 0.3 vs 3.5 ± 0.8 days) were shown in BG. The BG experienced no significant differences in clinical outcomes compared with OG. Favorable clinical outcomes were shown at 6 months after surgery in both groups.

Conclusion: Lumbar decompressive surgery using biportal technique/endoscopy showed favorable clinical outcomes, less pain and a shorter hospital stay compared to microscopic surgery in patients with lumbar spinal stenosis.
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http://dx.doi.org/10.1097/MD.0000000000015451DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6504265PMC
May 2019

Generalized On-Demand Production of Nanoparticle Monolayers on Arbitrary Solid Surfaces via Capillarity-Mediated Inverse Transfer.

Nano Lett 2019 03 27;19(3):2074-2083. Epub 2019 Feb 27.

Department of Chemical and Biomolecular Engineering , Sogang University , Seoul 04107 , Korea.

Century-old Langmuir monolayer deposition still represents the most convenient approach to the production of monolayers of colloidal nanoparticles on solid substrates for practical biological and chemical-sensing applications. However, this approach simply yields arbitrarily shaped large monolayers on a flat surface and is strongly limited by substrate topography and interfacial energy. Here, we describe a generalized and facile method of rapidly producing uniform monolayers of various colloidal nanoparticles on arbitrary solid substrates by using an ordinary capillary tube. Our method is based on an interesting finding of inversion phenomenon of a nanoparticle-laden air-water interface by flowing through a capillary tube in a manner that prevents the particles from adhesion to the capillary sidewall, thereby presenting the nanoparticles face-first at the tube's opposite end for direct and one-step deposition onto a substrate. We show that our method not only allows the placement of a nanoparticle monolayer at target locations of solid substrates regardless of their surface geometry and adhesion but also enables the production of monolayers containing nanoparticles with different size, shape, surface charge, and composition. To explore the potential of our approach, we demonstrate the facile integration of gold nanoparticle monolayers into microfluidic devices for the real-time monitoring of molecular Raman signals under dynamic flow conditions. Moreover, we successfully extend the use of our method to developing on-demand Raman sensors that can be built directly on the surface of consumer products for practical chemical sensing and fingerprinting. Specifically, we achieve both the pinpoint deposition of gold nanoparticle monolayers and sensitive molecular detection from the deposited region on clothing fabric for the detection of illegal drug substances, a single grain of rice and an orange for pesticide monitoring, and a $100 bill as a potential anti-counterfeit measure, respectively. We believe that our method will provide unique opportunities to expand the utility of colloidal nanoparticles and to greatly improve the accessibility of nanoparticle-based sensing technologies.
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http://dx.doi.org/10.1021/acs.nanolett.9b00248DOI Listing
March 2019

Phase transfer-driven rapid and complete ligand exchange for molecular assembly of phospholipid bilayers on aqueous gold nanocrystals.

Chem Commun (Camb) 2019 Mar;55(22):3195-3198

Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, Korea.

A phase transfer-mediated ligand exchange method is developed for highly selective and rapid synthesis of colloidal phospholipid bilayer-coated gold nanocrystals. The complete replacement of strongly bound surface ligands such as cetyltrimethylammonium bromide (CTAB) and citrate by phospholipid bilayer can be quickly achieved by water-chloroform phase transfer.
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http://dx.doi.org/10.1039/c8cc10037cDOI Listing
March 2019

Bubble-free rapid microfluidic PCR.

Biosens Bioelectron 2019 Feb 11;126:725-733. Epub 2018 Oct 11.

Department of Bioengineering, University of California Berkeley, CA 94720, USA; Berkeley Sensor and Actuator Center, University of California Berkeley, CA 94720, USA; UC Berkeley and UCSF Joint Graduate Program in Bioengineering, Berkeley/San Francisco, USA; Department of Electrical Engineering and Computer Science, University of California Berkeley, CA 94720, USA; Biophysics Graduate Program, University of California Berkeley, CA 94720, USA. Electronic address:

Microfluidic polymerase chain reaction (PCR) has been of great interest owing to its ability to perform rapid and specific nucleic acid amplification and analysis on small volumes of samples. One of the major drawbacks of microfluidic PCR is bubble generation and reagent evaporation, which can cause malfunctions. Here, through theoretical modeling and characterization of bubble behavior, we propose a bubble-free microfluidic PCR device via controlled fluid transfer. Our approach exploits a thin impermeable polyethylene (PE) top layer that minimizes the generation of bubbles by inhibiting mass transport along a vertical direction. Simulation results demonstrate that a calculated mass flow difference of approximately 370% can be obtained by utilizing an impermeable membrane as the vertical barrier layer. To demonstrate proof-of-concept, two nanoporous polymeric materials, poly(dimethylsiloxane) (PDMS) and PE, were used for stand-alone self-powered sample loading (approximately 70 s) and for use as a vertical barrier layer, respectively. Consequently, we demonstrate successful amplification of the cMET gene, a nucleic acid (NA) biomarker for lung cancer, and complete an ultrafast PCR test in less than 3 min using a high powered Peltier-based thermal cycler under bubble-free conditions. This approach will result in a new paradigm for ultrafast molecular diagnosis and can facilitate NA-based nearly instantaneous diagnostics for point-of-care testing and for personalized and preventive medicine.
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http://dx.doi.org/10.1016/j.bios.2018.10.005DOI Listing
February 2019

Plasmonic bacteria on a nanoporous mirror via hydrodynamic trapping for rapid identification of waterborne pathogens.

Light Sci Appl 2018 3;7:68. Epub 2018 Oct 3.

1Department of Chemical and Biomolecular Engineering, Sogang University, Seoul, 04107 Korea.

A rapid, precise method for identifying waterborne pathogens is critically needed for effective disinfection and better treatment. However, conventional methods, such as culture-based counting, generally suffer from slow detection times and low sensitivities. Here, we developed a rapid detection method for tracing waterborne pathogens by an innovative optofluidic platform, a plasmonic bacteria on a nanoporous mirror, that allows effective hydrodynamic cell trapping, enrichment of pathogens, and optical signal amplifications. We designed and simulated the integrated optofluidic platform to maximize the enrichment of the bacteria and to align bacteria on the nanopores and plasmonic mirror via hydrodynamic cell trapping. Gold nanoparticles are self-assembled to form antenna arrays on the surface of bacteria, such as and , by replacing citrate with hydroxylamine hydrochloride in order to amplify the signal of the plasmonic optical array. Owing to the synergistic contributions of focused light via the nanopore geometry, self-assembled nanoplasmonic optical antennas on the surface of bacteria, and plasmonic mirror, we obtain a sensitivity of detecting as low as 10 cells/ml via surface-enhanced Raman spectroscopy. We believe that our label-free strategy via an integrated optofluidic platform will pave the way for the rapid, precise identification of various pathogens.
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http://dx.doi.org/10.1038/s41377-018-0071-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168555PMC
October 2018

Photothermal Convection Lithography for Rapid and Direct Assembly of Colloidal Plasmonic Nanoparticles on Generic Substrates.

Small 2018 11 7;14(45):e1803055. Epub 2018 Oct 7.

Department of Life Science, University of Seoul, Seoul, 130-743, Republic of Korea.

Controlled assembly of colloidal nanoparticles onto solid substrates generally needs to overcome their thermal diffusion in water. For this purpose, several techniques that are based on chemical bonding, capillary interactions with substrate patterning, optical force, and optofluidic heating of light-absorbing substrates are proposed. However, the direct assembly of colloidal nanoparticles on generic substrates without chemical linkers and substrate patterning still remains challenging. Here, photothermal convection lithography is proposed, which allows the rapid placement of colloidal nanoparticles onto the surface of diverse solid substrates. It is based on local photothermal heating of colloidal nanoparticles by resonant light focusing without substrate heating, which induces convective flow. The convective flow, then, forces the colloidal nanoparticles to assemble at the illumination point of light. The size of the assembly is increased by either increasing the light intensity or illumination time. It is shown that three types of colloidal gold nanoparticles with different shapes (rod, star, and sphere) can be uniformly assembled by the proposed method. Each assembly with a diameter of tens of micrometers can be completed within a minute and its patterned arrays can also be achieved rapidly.
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http://dx.doi.org/10.1002/smll.201803055DOI Listing
November 2018

Facile Fabrication of Large-Scale Porous and Flexible Three-Dimensional Plasmonic Networks.

ACS Appl Mater Interfaces 2018 Aug 13;10(33):28242-28249. Epub 2018 Aug 13.

Department of Life Science , University of Seoul , Seoul 130-743 , Republic of Korea.

Assembling metallic nanoparticles and trapping target molecules within the probe volume of the incident light are important in plasmonic detection. Porous solid structures with three-dimensionally integrated metal nanoparticles would be very beneficial in achieving these objectives. Currently, porous inorganic oxides are being prepared under stringent conditions and further subjected to either physical or chemical attachment of metal nanoparticles. In this study, we propose a facile method to fabricate large-scale porous and flexible three-dimensional (3D) plasmonic networks. Initially, uncured polydimethylsiloxane (PDMS), in which metal ions are dissolved, diffuses spontaneously into the simple sugar crystal template via capillary action. As PDMS is cured, metal ions are automatically reduced to form a dense array of metal nanoparticles. After curing, the sugar template is easily removed by water treatment to obtain porous 3D plasmonic networks. We controlled the far-field scattering and near-field enhancement of the network by changing either the metal ion precursor or its concentration. To demonstrate the key advantages of our 3D plasmonic networks, such as simple fabrication, optical signal enhancement, and molecular trapping, we conducted sensitive Raman detection of several important molecules, including adenine, humidifier disinfectants, and volatile organic compounds.
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http://dx.doi.org/10.1021/acsami.8b11055DOI Listing
August 2018

Tunable Plasmonic Cavity for Label-free Detection of Small Molecules.

ACS Appl Mater Interfaces 2018 Apr 3;10(15):13226-13235. Epub 2018 Apr 3.

Department of Life Science , University of Seoul , Seoul 130-743 , Republic of Korea.

Owing to its high sensitivity and high selectivity along with rapid response time, plasmonic detection has gained considerable interest in a wide variety of sensing applications. To improve the fieldwork applicability and reliability of plasmonic detection, the integration of plasmonic nanoparticles into optical devices is desirable. Herein, we propose an integrated label-free detection platform comprising a plasmonic cavity that allows sensitive molecular detection via either surface-enhanced Raman scattering (SERS) or plasmon resonance energy transfer (PRET). A small droplet of metal ion solution spontaneously produces a plasmonic cavity on the surface of uncured poly(dimethylsiloxane) (PDMS), and as PDMS is cured, the metal ions are reduced to form a plasmonic antennae array on the cavity surface. Unique spherical feature and the integrated metallic nanoparticles of the cavity provide excellent optical functions to focus the incident light in the cavity and to rescatter the light absorbed by the nanoparticles. The optical properties of the plasmonic cavity for SERS or PRET are optimized by controlling the composition, size, and density of the metal nanoparticles. By using the cavity, we accomplish both 1000-fold sensitive detection and real-time monitoring of reactive oxygen species secreted by live cells via PRET. In addition, we achieve sensitive detection of trace amounts of toxic environmental molecules such as 5-chloro-2-methyl-4-isothiazolin-3-one/2-methyl-4-isothiazol-3-one (CMIT/MIT) and bisphenol A, as well as several small biomolecules such as glucose, adenine, and tryptophan, via SERS.
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http://dx.doi.org/10.1021/acsami.8b01550DOI Listing
April 2018

Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β-Cell after Brief Glucose Stimulation.

J Proteome Res 2018 04 15;17(4):1664-1676. Epub 2018 Mar 15.

Protein Research Group, Department of Biochemistry and Molecular Biology , University of Southern Denmark , DK-5230 Odense M , Denmark.

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells.
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http://dx.doi.org/10.1021/acs.jproteome.7b00930DOI Listing
April 2018

Multifunctional Device based on phosphor-piezoelectric PZT: lighting, speaking, and mechanical energy harvesting.

Sci Rep 2018 01 10;8(1):301. Epub 2018 Jan 10.

Interdisciplinary Program of LED Convergence, Pukyong National University, Busan, 608-737, Republic of Korea.

We demonstrated the tri-functional device based on all powder-processing methods by using ZnS powder as phosphor layer and piezoelectric material as dielectric layer. The fabricated device generated the electroluminescent (EL) light from phosphor and the sound from piezoelectric sheet under a supply of external electric power, and additionally harvested the reverse-piezoelectric energy to be converted into EL light. Under sinusoidal applied voltage, EL luminances were exponentially increased with a maximum luminous efficiency of 1.3 lm/W at 40 V and 1,000 Hz, and sound pressure levels (SPLs) were linearly increased. The EL luminances were linearly dependent on applied frequency while the SPLs showed the parabolic increase behavior below 1,000 Hz and then the flat response. The temperature dependence on EL luminances and SPLs was demonstrated; the former was drastically increased and the latter was slightly decreased with the increase of temperature. Finally, as an energy harvesting application, the piezoelectric-induced electroluminescence effect was demonstrated by applying only mechanical pressure to the device without any external electric power.
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http://dx.doi.org/10.1038/s41598-017-18571-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5762879PMC
January 2018

Spontaneous Phase Transfer-Mediated Selective Removal of Heavy Metal Ions Using Biocompatible Oleic Acid.

Sci Rep 2017 12 1;7(1):16727. Epub 2017 Dec 1.

Department of Chemical and Biomolecular Engineering, Sogang University, Seoul, 04107, Korea.

Here, we propose an environmentally benign removal technique for heavy metal ions based on selective and spontaneous transfer to oleic acid. The ions can be removed via (1) the selective and rapid complexation with the carboxylic end of oleic acid at an oleic acid/water interface, and (2) the diffusion of such complex into the oleic acid layer. A wide variety of heavy metal ions such as Cu, Pb, Zn, and Ni can be selectively removed over K and Na. For example, the concentration of Cu is reduced to below 1.3 ppm within 24 h, which corresponds to the level of Cu permitted by the Environmental Protection Agency. The addition of ethylenediamine ligand to the metal ion solutions is also shown to enhance the phase transfer. The removal efficiency is increased by up to 6 times when compared with that in the absence of the ligand and follows the order, Cu (99%) > Pb (96%) > Zn (95%) > Ni (65%). Moreover, the removal time can be shortened from 24 h to 1 h. The effect of an emulsion induced by a mechanical agitation on the removal of heavy metal ion is also studied.
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http://dx.doi.org/10.1038/s41598-017-17092-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5711890PMC
December 2017
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