Publications by authors named "Ki-Bum Kim"

81 Publications

Arthroscopic-assisted bone grafting and percutaneous K-wires fixation for the treatment of scaphoid nonunion in the skeletally immature patient: Three cases report.

Medicine (Baltimore) 2021 Jan;100(3):e24095

Department of Orthopedic surgery, Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonbuk National University Medical School Jeonju, Jeonbuk, 54907 - 54896, Republic of Korea.

Rationale: The treatment methods of pediatric scaphoid nonunion are still controversial. To our knowledge, arthroscopic-assisted treatments for pediatric scaphoid nonunion has not been reported in the English-language literature. Therefore, the purpose of this study is to report the use of arthroscopic-assisted bone grafting for scaphoid nonunion fracture in 3 patients and present a literature review.

Patients Concerns: Two 15-year-old patients developed carpal joint injuries over a year, prior to their hospital presentation, since they had not received adequate treatment. The third patient, 12 years of age, was diagnosed with scaphoid fracture after a traffic accident and underwent conservative treatment but presented to the hospital due to issues related with bone union.

Diagnosis: All 3 patients were diagnosed with scaphoid nonunion at our hospital, using plain wrist radiographs and computed tomography.

Interventions: All the patients underwent arthroscopic debridement; 2 patients received autogenous iliac cancellous bone graft, while the other patient received a bone substitute graft. The internal fixation of the scaphoid was performed with K-wires.

Outcomes: Bone unions were achieved in all patients, and the final follow-up resulted in successful outcomes.

Lessons: Arthroscopic-assisted bone grafting and percutaneous K-wire fixation can be considered as a good method for the treatment of pediatric scaphoid nonunion fractures. Therefore, it is a primary treatment option for symptomatic scaphoid nonunion fracture and displaced fractures.
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http://dx.doi.org/10.1097/MD.0000000000024095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7837869PMC
January 2021

Tertiary RNA Folding-Targeted Drug Screening Strategy Using a Protein Nanopore.

Anal Chem 2021 02 21;93(5):2811-2819. Epub 2021 Jan 21.

Disease Target Structure Research Center, KRIBB, Daejeon 34141, Republic of Korea.

Bacterial riboswitch RNAs are attractive targets for novel antibiotics against antibiotic-resistant superbacteria. Their binding to cognate metabolites is essential for the regulation of bacterial gene expression. Despite the importance of RNAs as therapeutic targets, the development of RNA-targeted, small-molecule drugs is limited by current biophysical methods. Here, we monitored the specific interaction between the adenine-sensing riboswitch aptamer domain (ARS) and adenine at the single-molecule level using α-hemolysin (αHL) nanopores. During adenine-induced tertiary folding, adenine-bound ARS intermediates exhibited characteristic nanopore events, including a two-level ionic current blockade and a ∼ 5.6-fold longer dwell time than that of free RNA. In a proof-of-concept experiment, tertiary RNA folding-targeted drug screening was performed using a protein nanopore, which resulted in the discovery of three new ARS-targeting hit compounds from a natural compound library. Taken together, these results reveal that αHL nanopores are a valuable platform for ultrasensitive, label-free, and single-molecule-based drug screening against therapeutic RNA targets.
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http://dx.doi.org/10.1021/acs.analchem.0c03941DOI Listing
February 2021

A preclinical trial of perventricular pulmonary valve implantation: Pericardial versus aortic porcine valves mounted on self-expandable stent.

Artif Organs 2021 May 6;45(5):E89-E100. Epub 2020 Dec 6.

Department of Thoracic and Cardiovascular Surgery, Sejong General Hospital, Bucheon, Korea.

Perventricular pulmonary valve implantation (PPVI) of a xenograft valve can be a less invasive technique that avoids cardiopulmonary bypass in patients who require pulmonary valve replacement. We compared the hemodynamics, durability, and histologic changes between two different xenogenic valves (pericardial vs. aortic valve porcine xenografts) implanted into the pulmonary valve position using a PPVI technique and evaluated the safety and efficacy of PPVI as a preclinical study. In 18 sheep, pericardial (group porcine pericardial [PP], n = 9) or aortic valve (group porcine aortic valve [PAV], n = 9) xenogenic porcine valves manufactured as a stented valve were implanted using a PPVI technique. The porcine tissues were decellularized, alpha-galactosidase treated, fixed with glutaraldehyde after space-filler treatment, and detoxified to improve durability. Hemodynamic and immunohistochemical studies were performed after the implantation; radiologic and histologic studies were performed after a terminal procedure. All stented valves were positioned properly after the implantation, and echocardiography and cardiac catheterization demonstrated good hemodynamic state and function of the valves. All the anti-α-Gal IgM and IgG titers were below 0.3 optical density. Computed tomography of extracted valves demonstrated no significant differences in the degree of calcification between the two groups (P = .927). Microscopic findings revealed a minimal amount of calcification and no significant infiltration of macrophage or T-cell in both groups, regardless of the implantation duration. The PPVI is a feasible technique. Both stented valves made of PP and PAV showed no significant differences in hemodynamic profile, midterm durability, and degree of degenerative dystrophic calcification.
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http://dx.doi.org/10.1111/aor.13845DOI Listing
May 2021

Effect of the Bilayer Period of Atomic Layer Deposition on the Growth Behavior and Electrical Properties of the Amorphous In-Zn-O Film.

ACS Appl Mater Interfaces 2020 Sep 20;12(35):39372-39380. Epub 2020 Aug 20.

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

This study reports on the effect of a bilayer period on the growth behavior, microstructure evolution, and electrical properties of atomic layer deposition (ALD) deposited In-Zn-O (IZO) films, fixing the ALD cycle ratio of In-O/Zn-O as 9:1. Here, the bilayer period is defined as the total number of ALD cycles in one supercycle of In-O and Zn-O by alternately stacking Zn-O and In-O layers at a temperature of 220 °C. IZO films with a bilayer period from 10 to 40 cycles, namely, IZO[In-O/Zn-O = 9:1] to IZO[36:4], result to form an amorphous phase with a resistivity of 4.94 × 10 Ω·cm. However, by increasing the bilayer period above 100 cycles, the IZO films begin to form a mixed amorphous-nanocrystalline microstructure, resulting from the limited intermixing at the interfaces. Concomitantly, the overall film resistivity is considerably increased with a simultaneous decrease in both the carrier mobility and the concentration. These results not only reveal the importance of the bilayer period in designing the ALD stacking sequence in the ALD-IZO, but also provide the possibility of forming various multilayered materials with different electrical properties.
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http://dx.doi.org/10.1021/acsami.0c07540DOI Listing
September 2020

Treatment Outcomes at Skeletal Maturity after Calcaneo-Cuboid-Cuneiform Osteotomy for Symptomatic Flatfoot Deformity in Children.

Clin Orthop Surg 2020 Jun 14;12(2):252-257. Epub 2020 May 14.

Department of Orthopaedic Surgery, Jeonbuk National University Medical School, Research Institute for Endocrine Sciences and Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea.

Background: The purpose of this study was to evaluate clinical and radiological outcomes at skeletal maturity after a calcaneo-cuboid-cuneiform osteotomy (triple C osteotomy) for symptomatic flatfoot deformity compared with healthy young adult controls.

Methods: Nineteen patients (30 feet) who undergone a triple C osteotomy for idiopathic symptomatic flatfeet from July 2006 to April 2013 were compared with 19 controls (38 feet). Radiographic measurements at preoperative examination, 1-year postoperative follow-up, and follow-up at skeletal maturity were evaluated. Functional outcomes were assessed by using the validated visual analog scale foot and ankle (VAS-FA) and the modified American Orthopaedic Foot and Ankle Surgery (AOFAS) score.

Results: In the triple C osteotomy group, 11 of 12 radiographic measurements were significantly improved at 1 year postoperatively and the last follow-up ( < 0.001). There was no recurrence at skeletal maturity ( > 0.05). There were no significant differences in nine of 12 radiographic measurements between the triple C osteotomy group at maturity and the control group ( > 0.05). Average VAS-FA and AOFAS scores were significantly improved at the time of skeletal maturity ( < 0.001).

Conclusions: Surgical correction of symptomatic flatfoot deformity in childhood resulted in favorable outcomes after the triple C osteotomy. Deformity correction was also maintained during follow-up at skeletal maturity.
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http://dx.doi.org/10.4055/cios19062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237249PMC
June 2020

Sheet Resistance Analysis of Interface-Engineered Multilayer Graphene: Mobility Versus Sheet Carrier Concentration.

ACS Appl Mater Interfaces 2020 Jul 26;12(27):30932-30940. Epub 2020 May 26.

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

Both interlayer-undoped and interlayer-doped multilayer graphenes were prepared by the multiple transfers of graphene layers with multiple Cu etching (either dopant-free or doped during etching) and transfer, and the effect of interface properties on the electrical properties of multilayer graphene was investigated by varying the number of layers from 1 to 12. In both the cases, the sheet resistance decreased with increasing number of layers from 700 to 104 Ω/sq for the interlayer-undoped graphene and from 280 to 25 Ω/sq for the interlayer-doped graphene. Further, Hall measurements revealed that the origins of the sheet resistance reduction in the two cases are different. In the interlayer-undoped graphene, the sheet resistance decreased because of the increase in mobility with the addition of inner layers, which has a low carrier density and a high carrier mobility. On the other hand, it decreased because of the increase in sheet carrier density in the interlayer-doped multilayer graphene. The mobility and carrier density variations in both the cases were confirmed by fitting with the model of Hall effect in the heterojunction. In addition, we found that surface property modification by the doping of the top layer and the formation of double-layer graphene with different partial coverages allow the separate control of carrier density and mobility. Our study provides an effective approach for controlling the properties of multilayer graphene for electronic applications.
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http://dx.doi.org/10.1021/acsami.0c04542DOI Listing
July 2020

An electrophoretic DNA extraction device using a nanofilter for molecular diagnosis of pathogens.

Nanoscale 2020 Feb;12(8):5048-5054

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

Rapid and efficient nucleic acid (NA) extraction and concentration are required for point-of-care analysis in order to prevent an epidemic/pandemic disease outbreak. Typical silica-based NA extraction methods have limitations such as being time-consuming, requiring human intervention, and resulting in a low recovery yield. In this study, we have developed a pathogenic DNA extraction device based on electrokinetic separation incorporated with a silicon nitride (SiNx) nanofilter, which expedites the DNA extraction procedure with advantages of being convenient, efficient, and inexpensive. This DNA extraction device consists of a computer numerical control (CNC) milled-Teflon gadget with a cis-chamber as a cell lysate reservoir and a trans-chamber as a elution solution reservoir, with the SiNx nanofilter being inserted between the two chambers. The SiNx nanofilter was fabricated using a photolithographic method in conjunction with nanoimprinting. Approximately 7.2 million nanopores of 220 nm diameter were located at the center of the nanofilter. When a DC electric field is applied through the nanopores, DNA is transferred from the cis-chamber to the trans-chamber to isolate the DNA from the cell debris. To demonstrate the DNA extraction performance, we measured the absorbances at 260 and 280 nm and performed a real-time polymerase chain reaction (real-time PCR) using the recovered DNA to verify its feasibility for downstream genetic analysis. Moreover, the DNA extraction device was successfully operated using a 1.5 V alkaline battery, which verifies the portability of the device for point-of-care testing. Such an advanced DNA extraction system can be utilized in various fields including clinical analysis, pathogen detection, forensic analysis, and on-site detection.
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http://dx.doi.org/10.1039/c9nr10675hDOI Listing
February 2020

Selective Atomic Layer Deposition of Metals on Graphene for Transparent Conducting Electrode Application.

ACS Appl Mater Interfaces 2020 Mar 15;12(12):14331-14340. Epub 2020 Mar 15.

School of Materials Science and Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Korea.

Although graphene has considerable potential as a next-generation transparent conducting electrode (TCE) material owing to its excellent optical transparency and flexibility, its electrical properties require further improvement for industrial application. This study reports a pathway of doping graphene by selective atomic layer deposition (ALD) of metals to elevate the electrical conductivity of graphene. Introduction of a novel Pt precursor [dimethyl(,-dimethyl-3-butene-1-amine-)platinum(II); CHNPt; DDAP] facilitates a low-temperature (165 °C) process. The sheet resistance () of graphene is reduced significantly from 471 to 86.8 Ω sq after 200 cycles of Pt ALD, while the optical transmittance at 550 nm () is maintained above 90% up to 200 cycles due to the selective growth of Pt on the defects of graphene. Furthermore, comprehensive analysis, including metal (Ru, Pt, and Ni) ALD on graphene, metal (Ru, Pt, Ni, Au, and Co) evaporation on graphene, and change in the ALD chemicals, demonstrates that ALD allows efficient graphene doping and the oxygen affinity of the metal is one of the key properties for efficient graphene doping. Finally, Pt ALD is applied to a multilayer graphene to further reduce down to 75.8 Ω sq yet to be highly transparent ( 87.3%) after 200 cycles. In summary, the selective ALD of metals opens a way of improving the electrical properties of graphene to a level required for the industrial TCE application and has the potential to promote development of other types of functional metal-graphene composites.
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http://dx.doi.org/10.1021/acsami.9b23261DOI Listing
March 2020

Surface modification of solid-state nanopore by plasma-polymerized chemical vapor deposition of poly(ethylene glycol) for stable device operation.

Nanotechnology 2020 May 16;31(18):185503. Epub 2020 Jan 16.

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

Biopolymer adsorption onto a membrane is a significant issue in the reliability of solid-state nanopore devices, since it degrades the device performance or promotes device failure. In this work, a poly(ethylene glycol) (PEG) layer was coated on a silicon nitride (SiN) membrane by plasma-polymerized vapor deposition to inhibit biopolymer adsorption. From optical observations, the deposited PEG layer demonstrated increased hydrophilicity and anti-adsorption property compared to the SiN surface. Electrical properties of the PEG/SiN nanopore were characterized, showing Ohmic behavior and a 6.3 times higher flicker noise power due to the flexible conformation of PEG in water. Antifouling performance of each surface was analyzed by measuring the average time from voltage bias to the first adsorption during DNA translocation experiments, where the modified surface enabled two times prolonged device operation. The time to adsorption was dependent on the applied voltage, implying adsorption probability was dominated by the electrophoretic DNA approach to the nanopore. DNA translocation behaviors on each surface were identified from translocation signals, as the PEG layer promoted unfolded and fast movement of DNA through the nanopore. This work successfully analyzed the effect of the PEG layer on DNA adsorption and translocation in solid-state nanopore experiments.
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http://dx.doi.org/10.1088/1361-6528/ab6cdbDOI Listing
May 2020

Direct electrophoretic microRNA preparation from clinical samples using nanofilter membrane.

Nano Converg 2020 Jan 13;7(1). Epub 2020 Jan 13.

Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea.

A method to directly collect negatively charged nucleic acids, such as DNA and RNA, in the biosamples simply by applying an electric field in between the sample and collection buffer separated by the nanofilter membrane is proposed. The nanofilter membrane was made of low-stress silicon nitride with a thickness of 100 nm, and multiple pores were perforated in a highly arranged pattern using nanoimprint technology with a pore size of 200 nm and a pore density of 7.22 × 10/cm. The electrophoretic transport of hsa-mir-93-5p across the membrane was confirmed in pure microRNA (miRNA) mimic solution using quantitative reverse transcription-polymerase chain reactions (qRT-PCR). Consistency of the collected miRNA quantity, stability of the system during the experiment, and yield and purity of the prepared sample were discussed in detail to validate the effectiveness of the electrical protocol. Finally, in order to check the applicability of this method to clinical samples, liquid biopsy process was demonstrated by evaluating the miRNA levels in sera of hepatocellular carcinoma patients and healthy controls. This efficient system proposed a simple, physical idea in preparation of nucleic acid from biosamples, and demonstrated its compatibility to biological downstream applications such as qRT-PCR as the conventional nucleic acid extraction protocols.
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http://dx.doi.org/10.1186/s40580-019-0212-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6955385PMC
January 2020

Electrical properties of graphene/InO bilayer with remarkable uniformity as transparent conducting electrode.

Nanotechnology 2020 Feb 20;31(9):095708. Epub 2019 Nov 20.

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

A graphene/InO bilayer (termed as GI-bilayer) is proposed as a transparent conducting electrode with remarkably improved areal-uniformity. To fabricate this new structure, an InO layer with a thickness of less than 50 nm was grown by atomic layer deposition and then a graphene layer was grown by chemical vapor deposition and subsequently transferred onto the as-grown InO layer. Electrical and optical properties of the GI-bilayer were systematically studied to verify effects of the underlying InO layer. Hall measurements and following analysis showed a conductance enhancement of the GI-bilayer owing to p-type doping of graphene. Specifically, Raman analysis and ultraviolet photoelectron spectroscopy were performed to prove p-type doping of the graphene in the GI-bilayer. In addition, the GI-bilayer exhibited the significantly improved uniformity of the sheet resistance compared to that of a conventional monolayer of graphene. There was a duality on the role of the InO underlayer in the GI-bilayer. It acted as a dopant layer to the graphene and lowered the sheet resistance from 863 to 510 Ω/sq as well as compensated microscale defects on graphene. More importantly, the InO underlayer resulted in the extremely reduced standard deviation of sheet resistance from 150 to 7.5 Ω/sq over the area of 49 cm.
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http://dx.doi.org/10.1088/1361-6528/ab599cDOI Listing
February 2020

Risk Factors for Major Amputation on Hindfoot Ulcers in Hospitalized Diabetic Patients.

Adv Wound Care (New Rochelle) 2019 May 3;8(5):177-185. Epub 2019 May 3.

Department of Plastic Surgery, Korea University Guro Hospital, Seoul, South Korea.

The purpose of this study was to investigate the risk factors for major amputation in patients hospitalized with diabetic foot ulcers involving the hindfoot. Between January 2003 and October 2017, a total of 1,657 diabetic patients were admitted to the diabetic wound center of Korea University Guro Hospital, for the management of foot ulcers. Among the admitted patients, 117 diabetic patients with hindfoot ulcers were included in this study. One hundred and four patients (89%) healed without major amputation, while 13 patients (11%) healed with major amputation. Data related to 88 potential risk factors, including demographics, ulcer condition, vascularity, bioburden, neurology, and serology, were collected from patients in these two groups for comparison. Among the 88 potential risk factors, 15 showed statistically significant differences between the two groups. In univariate analysis of 88 potential risk factors, nine showed statistically significant differences. In stepwise multiple logistic regression analysis, three of the nine risk factors remained statistically significant. Multivariate-adjusted odds ratios for pulmonary disorders, erythrocyte sedimentation rate (ESR) levels, and total iron-binding capacity (TIBC) levels were 38.525, 1.047, and 0.976, respectively. Compared with forefoot and midfoot ulcers, diabetic foot ulcers involving the hindfoot are at increased risk of major amputation because infection may spread proximal to the ankle. However, large-scale cohort studies that specifically discuss the outcomes and characteristics of diabetic hindfoot ulcers are not widely available. Risk factors for major amputation in patients hospitalized with diabetic hindfoot ulcers include pulmonary disorders, high levels of ESR, and decreased TIBC levels.
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http://dx.doi.org/10.1089/wound.2018.0814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6855283PMC
May 2019

Osteonecrosis of the medial tibial plateau after intra-articular corticosteroid injection: A case report.

Medicine (Baltimore) 2019 Nov;98(44):e17248

Department of Orthopedic Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital.

Rationale: Intra-articular corticosteroid injection (IACI) is a cost-effective conservative treatment of mild-to-moderate osteoarthritis. Adverse events after this procedure range from life-threatening systemic reactions to self-limiting local reactions. To our knowledge, this is the 1st report of osteonecrosis (ON) in the medial tibial plateau after IACI.

Patient Concerns: An 81-year-old female visited our hospital due to left knee pain of increasing intensity. She presented the sudden onset of severe acute knee pain with long lasting knee pain for several years.

Diagnosis: The diagnosis was confirmed ON of medial tibial plateau of knee joint by pathologic finding.

Interventions: We conducted a posterior stabilized total-knee arthroplasty with no requirement for bone grafting or additional prosthesis, such as metal augments or stems.

Outcomes: At the postoperative 1 year follow-up, the patient was satisfied with the surgery and had no pain during walking and active knee motion.

Lessons: This case especially stress the possibility of ON in medial tibia plateau after IACI. Therefore, clinicians should monitor symptoms after IACI to enable early detection of this complication.
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http://dx.doi.org/10.1097/MD.0000000000017248DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946538PMC
November 2019

Microfluidic electrochemical cell for in situ structural characterization of amorphous thin-film catalysts using high-energy X-ray scattering.

J Synchrotron Radiat 2019 Sep 9;26(Pt 5):1600-1611. Epub 2019 Aug 9.

Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave, Lemont, IL 60439, USA.

Porous, high-surface-area electrode architectures are described that allow structural characterization of interfacial amorphous thin films with high spatial resolution under device-relevant functional electrochemical conditions using high-energy X-ray (>50 keV) scattering and pair distribution function (PDF) analysis. Porous electrodes were fabricated from glass-capillary array membranes coated with conformal transparent conductive oxide layers, consisting of either a 40 nm-50 nm crystalline indium tin oxide or a 100 nm-150 nm-thick amorphous indium zinc oxide deposited by atomic layer deposition. These porous electrodes solve the problem of insufficient interaction volumes for catalyst thin films in two-dimensional working electrode designs and provide sufficiently low scattering backgrounds to enable high-resolution signal collection from interfacial thin-film catalysts. For example, PDF measurements were readily obtained with 0.2 Å spatial resolution for amorphous cobalt oxide films with thicknesses down to 60 nm when deposited on a porous electrode with 40 µm-diameter pores. This level of resolution resolves the cobaltate domain size and structure, the presence of defect sites assigned to the domain edges, and the changes in fine structure upon redox state change that are relevant to quantitative structure-function modeling. The results suggest the opportunity to leverage the porous, electrode architectures for PDF analysis of nanometre-scale surface-supported molecular catalysts. In addition, a compact 3D-printed electrochemical cell in a three-electrode configuration is described which is designed to allow for simultaneous X-ray transmission and electrolyte flow through the porous working electrode.
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http://dx.doi.org/10.1107/S1600577519007240DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6730625PMC
September 2019

Atomic Layer Deposition of Nickel Using a Heteroleptic Ni Precursor with NH and Selective Deposition on Defects of Graphene.

ACS Omega 2019 Jun 25;4(6):11126-11134. Epub 2019 Jun 25.

School of Materials Science and Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Korea.

Atomic layer deposition (ALD) of Ni was demonstrated by introducing a novel oxygen-free heteroleptic Ni precursor, (η-cyclohexenyl)(η-cyclopentadienyl)nickel(II) [Ni(Chex)(Cp)]. For this process, non-oxygen-containing reactants (NH and H molecules) were used within a deposition temperature range of 320-340 °C. Typical ALD growth behavior was confirmed at 340 °C with a self-limiting growth rate of 1.1 Å/cycle. Furthermore, a postannealing process was carried out in a H ambient environment to improve the quality of the as-deposited Ni film. As a result, a high-quality Ni film with a substantially low resistivity (44.9 μΩcm) was obtained, owing to the high purity and excellent crystallinity. Finally, this Ni ALD process was also performed on a graphene surface. Selective deposition of Ni on defects of graphene was confirmed by transmission electron microscopy and atomic force microscopy analyses with a low growth rate (∼0.27 Å/cycle). This unique method can be further used to fabricate two-dimensional functional materials for several potential applications.
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http://dx.doi.org/10.1021/acsomega.9b01003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648170PMC
June 2019

Comparison of Growth Behavior and Electrical Properties of Graphene Grown on Solid and Liquid Copper by Chemical Vapor Deposition.

J Nanosci Nanotechnol 2020 Jan;20(1):316-323

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea.

We study the graphene growth behavior above and below the copper (Cu) melting point (1083 °C) by only changing the growth temperature from 1020 °C to 1100 °C at intervals of 40 °C, to investigate the effect of the Cu phase as a catalyst layer in graphene growth. We investigate the graphene growth behavior by observing the changes in nucleation density and grain size with growth time. As the phase of the Cu catalyst changes from solid to liquid, the grain size of graphene increases by 2 orders of magnitude from 0.4 to 40 m, while the nuclei density decreases by 4 orders of magnitude from 3.02/m₂ to 0.0004/m₂. Additionally, as in previous studies, graphene growth shows a well-aligned hexagonal shape on liquid Cu although graphene on solid Cu shows an irregular shape under the same growth conditions. The effect of the smooth surface of the liquid metal catalyst on graphene growth is remarkable even after considering the temperature difference. The reduction of defect density arising from the increase of the graphene grain size is confirmed by Raman spectroscopy. Additionally, the improvement in electrical properties is also investigated by Hall measurements.
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http://dx.doi.org/10.1166/jnn.2020.17279DOI Listing
January 2020

Nanopore Analysis on the Drug-Induced Conformation Change of a p53-Linker-Mouse Double Minute 2 Protein Complex.

J Nanosci Nanotechnol 2020 Jan;20(1):15-23

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea.

Detection of conformational changes in proteins by protein-protein interaction (PPI) is a key issue in developing drug screening platforms. In order to effectively investigate the conformational change in a protein at a single-molecule level, we propose the use of nanopore detection to identify protein conformational changes resulting from protein-protein interactions and their inhibition by Nutlin-3. We designed a protein complex comprising a p53 peptide and a mouse double minute 2 (MDM2) linked by 6 amino acids, transforming its shape from globular to dumbbell structure by inhibition of interaction between p53 peptide and MDM2. In the NMR experiment, no distinguished crosspeaks were observed upon Nutlin-3 addition. However, the nanopore experiment clearly showed double-peak signals with the addition of Nutlin-3. The observed fraction of the double-peak among single-peak signals increased from 8.77% to 22.03% with a concurrent increase in the Nutlin-3 concentration from a molar ratio of 1 to 10-fold. From the nanopore data, we estimated the dwell time for the elongated form of Nutlin-3-bound protein, which traverses for a longer duration (∼2 times) than the globular form. Finally, the hydrodynamic diameter of the local peak of the double-peak signal was calculated and compared with the X-ray crystallography results. This approach shows feasibility of the nanopore detection to verify the protein conformational change by inhibition of protein-protein interaction at a single-molecule level.
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http://dx.doi.org/10.1166/jnn.2020.17227DOI Listing
January 2020

Assessment of Long-term Outcomes of Soft-Tissue Augmentation by Injecting Fibroblasts Suspended in Hyaluronic Acid Filler.

JAMA Facial Plast Surg 2019 Jul;21(4):312-318

Department of Plastic Surgery, Korea University Guro Hospital, Seoul, South Korea.

Importance: In previous studies, this group has reported that cultured human fibroblasts suspended in hyaluronic acid (HA) filler might have potential use as a long-lasting injectable soft-tissue filler. However, the data were insufficient to determine the long-term outcomes.

Objective: To evaluate the long-term outcomes of cultured human fibroblasts suspended in HA filler used for soft-tissue augmentation.

Design, Setting, And Participants: A long-term case series study was performed. Between January 2010 and December 2013, a total of 38 patients were treated with fibroblast-HA filler mixture to augment nasal dorsa, nasolabial folds, and cheek depressions. Of these 38 patients, patients with follow-up period of greater than 3 years were included in this study. A total of 22 patients met the inclusion criteria.

Main Outcomes And Measures: Subjective assessment was performed to evaluate degree and time of resorption, improvement, satisfaction, softness of injection sites, and willingness to recommend this treatment to others. Objective assessment was carried out with patients' photographs. Safety and tolerability were also evaluated for this treatment.

Results: Of the 22 patients included in this study, 19 were women; mean (SD) patient age was 43 (15) years. All 22 patients experienced improvement following the treatment. Twenty (91%) patients were satisfied with the treatment. Nineteen patients (86%) considered that the injection site was as soft as it was before treatment. Patients' mean (SD) grading of improvement, satisfaction, and softness were 4.50 (0.51) (95% CI, 4.27-4.73), 4.14 (0.71) (95% CI, 3.82-4.45), and 4.82 (0.50) (95% CI, 4.59-5.00) at the last visit, respectively. Objective assessment demonstrated postoperative improvement in all patients: a rating of "much improved" was given to 7 patients (32%) by investigator 1; 8 patients (36%) by investigator 2; and 12 patients (55%) the injecting physician. This treatment was well tolerated; no adverse event was recorded for any patient.

Conclusions And Relevance: Injection of cultured human fibroblasts suspended in HA filler might be successful for long-term soft-tissue augmentation. To our knowledge, this study represents the longest follow-up study of soft-tissue augmentation with a fibroblast-HA filler mixture to date.

Level Of Evidence: 4.
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http://dx.doi.org/10.1001/jamafacial.2018.2127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6583875PMC
July 2019

Detection of metal corrosion characteristics in chlorine solution using solid state nanopore.

Nanotechnology 2019 May 7;30(22):225501. Epub 2019 Feb 7.

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

Nanopore structures were originally proposed for detection of biomolecule translocation through nanometer-scale pores that perforate membranes by transient changes in ionic current. In this study, these changes are utilized to detect corrosion of different metals in aqueous chlorine media. The corrosion behaviors of Cu, Al, Ti, and Cr were analyzed by monitoring the changes in ion current resulting from ion concentration variations in solutions due to corrosion of the metals. We observed that the Cu layer passivated by CuO was severely corroded when a drastic change of ion current was induced, from 10 to 30 nS to the level of 10 nS, as soon as the bias voltage was applied. In the case of Al passivated by thin AlO , the conductance increased from 10-30 to 166 ± 52 nS and became saturated. Highly localized pitting corrosion was observed on the periphery of the nanopore, where the electrical field was most concentrated. Finally, we observed that Ti and Cr passivated by oxide showed long-term stability without corrosion in 1 M KCl in the pH range of 4-11.
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http://dx.doi.org/10.1088/1361-6528/ab0515DOI Listing
May 2019

DNA translocation through a nanopore in an ultrathin self-assembled peptide membrane.

Nanotechnology 2019 May 5;30(19):195602. Epub 2019 Feb 5.

Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742, Republic of Korea.

Here, we explore the possibility of using peptide-based materials as a membrane in solid-state nanopore devices in an effort to develop a sequence-specific, programmable biological membrane platform. We use a recently developed tyrosine-mediated self-assembly peptide sheet. At the air/water interface, the 5mer peptide YFCFY self-assembles into a uniform and robust two-dimensional (2D) structure, and the peptide sheet is easily transferred to a low-noise glass substrate. The thickness of the peptide membrane can be adjusted to approximately 5 nm (or even to 2 nm) by an etching process, and the diameters of the peptide nanopores can be precisely controlled using a focused electron beam with an attuned spot size. The ionic current noise of the peptide nanopore is comparable to those of typical silicon nitride nanopores or multilayer 2D materials. Using this membrane, we successfully observe translocation of 1000 bp double-stranded DNA with a sufficient signal-to-noise ratio of ∼30 and an elongated translocation speed of ∼1 bp μs. Our results suggest that the self-assembled peptide film can be used as a sensitive nanopore membrane and employed as a platform for applying biological functionalities to solid-state substrates.
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http://dx.doi.org/10.1088/1361-6528/ab0488DOI Listing
May 2019

Potential of Allogeneic Adipose-Derived Stem Cell-Hydrogel Complex for Treating Diabetic Foot Ulcers.

Diabetes 2019 04 24;68(4):837-846. Epub 2019 Jan 24.

Anterogen Co. Ltd., Seoul, South Korea.

Mesenchymal stem cells (MSCs) may hold great promise for treating diabetic wounds. However, it is difficult for a clinician to use MSCs because they have not been commercialized. Meanwhile, a new commercial drug that contains adipose-derived stem cells (ASCs) has been developed. The purpose of this study was to examine the potential of allogeneic ASC sheets for treating diabetic foot ulcers. Fifty-nine patients with diabetic foot ulcers were randomized to either the ASC treatment group ( = 30) or a control group treated with polyurethane film ( = 29). Either an allogeneic ASC sheet or polyurethane film was applied on diabetic wounds weekly. These wounds were evaluated for a maximum of 12 weeks. Complete wound closure was achieved for 73% in the treatment group and 47% in the control group at week 8. Complete wound closure was achieved for 82% in the treatment group and 53% in the control group at week 12. The Kaplan-Meier median times to complete closure were 28.5 and 63.0 days for the treatment group and the control group, respectively. There were no serious adverse events related to allogeneic ASC treatment. Thus, allogeneic ASCs might be effective and safe to treat diabetic foot ulcers.
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http://dx.doi.org/10.2337/db18-0699DOI Listing
April 2019

Skin Hydration Level as a Predictor for Diabetic Wound Healing: A Retrospective Study.

Plast Reconstr Surg 2019 Apr;143(4):848e-856e

From the Department of Plastic Surgery, Korea University College of Medicine.

Background: In the diabetic foot, the skin may crack and develop fissures, potentially increasing vulnerability to ulceration and infection. Therefore, maintaining adequate skin hydration may be crucial for diabetic wound healing. However, no clinical study has addressed this issue. This study aimed to determine and compare the effect of the skin hydration level on diabetic wound healing with that of the tissue oxygenation level, which is recognized as the most reliable parameter in predicting diabetic wound healing.

Methods: This retrospective study included 263 diabetic patients with forefoot ulcers. Skin hydration and transcutaneous oxygen pressure data collected before and after percutaneous transluminal angioplasty were analyzed. Skin hydration and tissue oxygenation were graded as poor, moderate, or acceptable. Wound healing outcomes were graded as healed without amputation, minor amputation, or major amputation. Wound healing outcomes were compared using four parameters: skin hydration at baseline, transcutaneous oxygen pressure at baseline, post-percutaneous transluminal angioplasty skin hydration, and post-percutaneous transluminal angioplasty transcutaneous oxygen pressure.

Results: Each of the four parameters exhibited statistically significant correlations with wound healing outcomes. In the concurrent analysis of both skin hydration and transcutaneous oxygen pressure, skin hydration was a dominant parameter (p = 0.0018) at baseline, whereas transcutaneous oxygen pressure was a dominant parameter (p < 0.0001) following percutaneous transluminal angioplasty.

Conclusions: Skin hydration level might be a useful predictor for diabetic wound healing. In particular, the skin hydration level before recanalization was found to be superior to transcutaneous oxygen pressure in predicting wound healing.

Clinical Question/level Of Evidence: Risk, III.
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http://dx.doi.org/10.1097/PRS.0000000000005474DOI Listing
April 2019

Differentiation of selectively labeled peptides using solid-state nanopores.

Nanoscale 2019 Jan;11(5):2510-2520

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.

Determination of the amino acid sequence of a protein is critical for understanding various biological processes. Mass spectrometry has mainly been used for protein identification; however, there are limitations to its sensitivity when detecting low abundance proteins. In this study, we attempted to distinguish between three similar peptide sequences (∼40 amino acids, ∼5 kDa) that differed only by the location or number of cysteine residues with solid-state nanopores. The cysteine residues are located at one end, one at the center, and at both ends for each of the three peptides. We found that differentiation of the three types of peptides by nanopore signals was difficult. However, when the cysteine residue was labeled with a negatively charged molecule, Flamma® 496, the labeled peptides showed distinct signals for each peptide. Comparing the relative current blockades of labeled peptides with applied voltages, we found that the label was able to change peptide conformations and the resulting ionic current signals from the three labeled peptides were distinguished based on the relative current blockade, full width at half-maximum of the current blockade distribution, and single-molecule level peak shape analysis. Our results suggest that solid-state nanopores combined with a targeted labeling strategy could be used to obtain characteristic peptide signatures that could ultimately be used for protein identification.
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http://dx.doi.org/10.1039/c8nr09315fDOI Listing
January 2019

Alpha-Hederin Nanopore for Single Nucleotide Discrimination.

ACS Nano 2019 02 23;13(2):1719-1727. Epub 2019 Jan 23.

Graduate School of Biotechnology and Department of Food Science and Biotechnology , Kyung Hee University , Yongin 17104 , Republic of Korea.

Various types of biological and synthetic nanopores have been developed and utilized for the high-throughput investigation of individual biomolecules. Biological nanopores made with channel proteins are so far superior to solid-state ones in terms of sensitivity and reproducibility. However, the performance of a biological nanopore is dependent on the protein in the channel structure its dimensions are predetermined and are difficult to modify for broader applications. Here inspired by the cytotoxic mechanisms of a saponin derivative, alpha-hederin, we report a nonproteinaceous nanopore that can be formed spontaneously in a lipid membrane. We propose the pore-forming mechanism of alpha-hederin in a cholesterol-rich lipid membrane and a strategy to control the pore-forming rate by a lipid partitioning method. The small diameter and effective thickness of alpha-hederin nanopores enabled us to discriminate ssDNA homopolymers as well as four types of nucleotides, showing its potential as a DNA sequencing tool.
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http://dx.doi.org/10.1021/acsnano.8b07797DOI Listing
February 2019

Subnasal Lip Lifting in Aging Upper Lip: Combined Operation with Nasal Tip Plasty in Asians.

Plast Reconstr Surg 2019 03;143(3):701-709

From the Department of Plastic Surgery, Korea University College of Medicine; and the Park-Hyun Plastic Surgery Clinic.

Background: The objective of this study was to illustrate a novel technique for lifting of the aging upper lip with nasal tip plasty in Asians. With this procedure, a shortening of the philtrum, an increase of the vermilion, and a natural and nicer mouth can be obtained, with increase of the tip of the nose simultaneously.

Methods: Thirty patients were the subjects of this study. Incisions were made bilaterally beginning at the alar fold, entering nostrils, and rising medially on the skin below the lower margin of the medial crura. Excess skin of the philtrum was eliminated in two separate pieces and the muscle was suspended to the base of the nose with interrupted stitches.

Results: All patients expressed a high degree of satisfaction. The average ratio between the L1 reference line and the height of the upper lip measurement preoperatively was 0.43 ± 0.05. This ratio was improved postoperatively to an average of 0.32 ± 0.05. The nasolabial angle was 91.31 ± 4.19 degrees before surgery and 105.62 ± 5.04 degrees after surgery. The angle of the upper lip was 48.97 ± 2.41 degrees before surgery and 38.21 ± 3.34 degrees after surgery.

Conclusions: Lip lift is an effective tool for correcting a natural tendency of the upper lip to cover the upper teeth during aging. There is a dramatic improvement in the patient's facial aesthetic appearance during smiling and at rest. The authors strongly recommend this technique as part of the surgical procedure to achieve a youthful face.

Clinical Question/level Of Evidence: Therapeutic, V.
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http://dx.doi.org/10.1097/PRS.0000000000005315DOI Listing
March 2019

The dynamics of electron beam scattering on metal membranes: nanopore formation in metal membranes using transmission electron microscopy.

Nano Converg 2018 Nov 12;5(1):32. Epub 2018 Nov 12.

Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul, South Korea.

The dynamics of nanopore formation in metal membranes using the highly focused and high energy electron beams (e-beams) of transmission electron microscopy instruments was investigated. Various metals such as Al, Ti, Cr, Cu, and Au were selected to investigate the effect of the atomic mass of the metal on nanopore drilling, namely, elastic versus inelastic scattering. We demonstrated that the effect of elastic scattering (pore formation by sputtering) decreased as the atomic mass of the metal increased. Furthermore, experimental cross-sections obtained from normalized drilled volume vs. electron dose curves (characteristic contrast curves) matched well the calculated atomic displacement cross-sections determined from elastic scattering data. The sputtering energies of Ti, Cr, and Cu were determined to be approximately 10, 9, and 7 eV, respectively, which were in good agreement with the reported range of sputtering energy values.
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http://dx.doi.org/10.1186/s40580-018-0164-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6230544PMC
November 2018

Translocation of DNA and protein through a sequentially polymerized polyurea nanopore.

Nanoscale 2019 Jan;11(2):444-453

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea.

Here, we investigated the translocation of biomolecules, such as DNA and protein, through a sequentially polymerized polyurea nanopore, with a thin (<10 nm) polymer membrane of uniform thickness. The polyurea membrane was synthesized by molecular layer deposition using p-phenylenediisocyanate (PDI) and p-phenylenediamine (PDA) as sequential precursors. The membrane exhibited a hydrophobic surface with a highly negative surface charge density (-51 mC m-2 at pH 8). It was particularly noted that the high surface charge density of the membrane resulted in a highly developed electro-osmotic flow which, in turn, strongly influenced the capture probability of biomolecules, depending on the balance between the electro-osmotic and electrophoretic forces. For instance, the capture frequency of negatively charged DNA was demonstrated to be quite low, since these two forces more or less cancelled each other, whereas that of positively charged MDM2 was much higher, since these two forces were additive. We also identified that the mean translocation time of MDM2 through the polyurea nanopore was 26.1 ± 3.7 μs while that of the SiN nanopore was 14.2 ± 2.0 μs, hence suggesting that the enhanced electrostatic interaction between positively charged MDM2 and the negatively charged pore surface affects the translocation speed.
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http://dx.doi.org/10.1039/c8nr06229cDOI Listing
January 2019

Historical Perspectives of the Development of Materials Science and Engineering Program at Seoul National University and Vision.

Adv Mater 2018 10;30(42):e1804800

Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea.

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http://dx.doi.org/10.1002/adma.201804800DOI Listing
October 2018

Recent Progress in Solid-State Nanopores.

Adv Mater 2018 Oct 10;30(42):e1704680. Epub 2018 Sep 10.

Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea.

The solid-state nanopore has attracted much attention as a next-generation DNA sequencing tool or a single-molecule biosensor platform with its high sensitivity of biomolecule detection. The platform has advantages of processability, robustness of the device, and flexibility in the nanopore dimensions as compared with the protein nanopore, but with the limitation of insufficient spatial and temporal resolution to be utilized in DNA sequencing. Here, the fundamental principles of the solid-state nanopore are summarized to illustrate the novelty of the device, and improvements in the performance of the platform in terms of device fabrication are explained. The efforts to reduce the electrical noise of solid-state nanopore devices, and thus to enhance the sensitivity of detection, are presented along with detailed descriptions of the noise properties of the solid-state nanopore. Applications of 2D materials including graphene, h-BN, and MoS as a nanopore membrane to enhance the spatial resolution of nanopore detection, and organic coatings on the nanopore membranes for the addition of chemical functionality to the nanopore are summarized. Finally, the recently reported applications of the solid-state nanopore are categorized and described according to the target biomolecules: DNA-bound proteins, modified DNA structures, proteins, and protein oligomers.
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http://dx.doi.org/10.1002/adma.201704680DOI Listing
October 2018

Correction: Solid-state nanopore analysis on conformation change of p53TAD-MDM2 fusion protein induced by protein-protein interaction.

Nanoscale 2018 10;10(38):18423

Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea.

Correction for 'Solid-state nanopore analysis on conformation change of p53TAD-MDM2 fusion protein induced by protein-protein interaction' by Hongsik Chae et al., Nanoscale, 2018, DOI: 10.1039/c8nr06423g.
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http://dx.doi.org/10.1039/c8nr90204fDOI Listing
October 2018