Chonnam National University
  • Gwangju, South Korea
Recent publications
Three-dimensional (3D) stem cell culture systems have attracted considerable attention as a way to better mimic the complex interactions between individual cells and the extracellular matrix (ECM) that occur in vivo. Moreover, 3D cell culture systems have unique properties that help guide specific functions, growth, and processes of stem cells (e.g., embryogenesis, morphogenesis, and organogenesis). Thus, 3D stem cell culture systems that mimic in vivo environments enable basic research about various tissues and organs. In this review, we focus on the advanced therapeutic applications of stem cell-based 3D culture systems generated using different engineering techniques. Specifically, we summarize the historical advancements of 3D cell culture systems and discuss the therapeutic applications of stem cell-based spheroids and organoids, including engineering techniques for tissue repair and regeneration.
Background Focused evaluations on potential sex differences in the angiographic findings of the coronary arteries are scarce. This study was performed to compare the angiographic extent and localization of coronary stenosis between men and women. Methods A total of 2348 patients (mean age 62.5 years and 60% women) with stable chest pain undergoing invasive coronary angiography (CAG) were recruited from the database of the nation-wide chest pain registry. Obstructive coronary artery disease (CAD) was defined as ≥ 50% stenosis of the left main coronary artery and/or ≥ 70% stenosis of any other epicardial coronary arteries. Results Although women were older than men (64.4 ± 10.3 vs. 59.5 ± 11.4 years, P < 0.001), men had worse risk profiles including high blood pressure, more frequent smoking and elevated triglyceride and C-reactive protein. The prevalence of obstructive CAD was significantly higher in men than in women (37.0% vs. 28.4%, P < 0.001). Men had a higher prevalence of LM disease (10.3% vs. 3.5%, P < 0.001) and three-vessel disease (16.1% vs. 9.5%, P = 0.007) compared to women. In multiple binary logistic regression analysis, the risk of men having LM disease or three-vessel disease was 7.4 (95% confidence interval 3.48–15.97; P < 0.001) and 2.7 (95% confidence interval 1.57–4.64; P < 0.001) times that of women, respectively, even after controlling for potential confounders. Conclusions In patients with chest pain undergoing invasive CAG, men had higher obstructive CAD prevalence and more high-risk angiographic findings such as LM disease or three-vessel disease.
Herbicide resistance is one of the main crop traits that improve farming methods and crop productivity. CRISPR-Cas9 can be applied to the development of herbicide-resistant crops based on a target site resistance mechanism, by editing genes encoding herbicide binding proteins. The sgRNAs capable of editing the target genes of herbicides, pds (phytoene desaturase), ALS (acetolactate synthase), and EPSPS (5-Enolpyruvylshikimate-3-phosphate synthase), were designed to use with the CRISPR-Cas9 system in tomato ( Solanum lycopersicum cv. Micro-Tom). The efficiency of the sgRNAs was tested using Agrobacterium mediated transient expression in the tomato cotyledons. One sgRNA designed for editing the target site of PDS had no significant editing efficiency. However, three different sgRNAs designed for editing the target site of ALS had significant efficiency, and one of them, ALS2-P sgRNA, showed over 0.8% average efficiency in the cotyledon genome. The maximum efficiency of ALS2-P sgRNA was around 1.3%. An sgRNA for editing the target site of EPSPS had around 0.4% editing efficiency on average. The sgRNA efficiency testing provided confidence that editing of the target sites could be achieved in the transformation process. We confirmed that 19 independent transgenic tomatoes were successfully edited by ALS2_P or ALS1_W sgRNAs and two of them had three base deletion mutations, which are expected to have altered herbicide resistance. In this study, we demonstrated the usefulness of performing an sgRNA efficiency test before crop transformation, and confirmed that the CRISPR-Cas9 system is a valuable tool for breeding herbicide-resistant crops.
Background Epigenetic regulations frequently appear in Glioblastoma (GBM) and are highly associated with metabolic alterations. Especially, Histone deacetylases (HDACs) correlates with the regulation of tumorigenesis and cell metabolism in GBM progression, and HDAC inhibitors report to have therapeutic efficacy in GBM and other neurological diseases; however, GBM prevention and therapy by HDAC inhibition lacks a mechanism in the focus of metabolic reprogramming. Methods HDAC2 highly express in GBM and is analyzed in TCGA/GEPIA databases. Therefore, HDAC2 knockdown affects GBM cell death. Analysis of RNA sequencing and qRT-PCR reveals that miR-3189 increases and GLUT3 decreases by HDAC2 knockdown. GBM tumorigenesis also examines by using in vivo orthotopic xenograft tumor models. The metabolism change in HDAC2 knockdown GBM cells measures by glucose uptake, lactate production, and OCR/ECAR analysis, indicating that HDAC2 knockdown induces GBM cell death by inhibiting GLUT3. Results Notably, GLUT3 was suppressed by increasing miR-3189, demonstrating that miR-3189-mediated GLUT3 inhibition shows an anti-tumorigenic effect and cell death by regulating glucose metabolism in HDAC2 knockdown GBM. Conclusions Our findings will demonstrate the central role of HDAC2 in GBM tumorigenesis through the reprogramming of glucose metabolism by controlling miR-3189-inhibited GLUT3 expression, providing a potential new therapeutic strategy for GBM treatment.
Cracked tooth syndrome (CTS) is an incomplete fracture of a human tooth that commonly arises from chewing hard foods. Although it is a very common syndrome, CTS is often difficult to diagnose owing to the common small size of tooth cracks. Conventional techniques for the detection of cracks, such as transillumination and radiographic methods, are inaccurate and have poor imaging resolution. In this study, we devise a novel method for the in vivo detection of tooth microcracks by exploiting the mechanoluminescence (ML) phenomenon. ZrO2:Ti⁴⁺ (ZRT) phosphor particles are pasted onto suspected regions of tooth cracks and emit cyan-colored light as a result of masticatory forces. Then, a stretchable and self-healable photodetector (PD) array laminated on top of the phosphor particles converts the emitted photons into a photocurrent, which facilitates the two-dimensional mapping of the tooth cracks. Because of the high photosensitivity of the PD, intense ML and small size of ZRT phosphor particles, it is possible to image submicron- to micron-sized cracks with high resolution. Furthermore, the uniqueness of this technique over the conventional techniques stems from the application of a simple optical phenomenon, i.e., ML, for obtaining precise information regarding the locations, depth, and length of tooth cracks.
Objective This study aimed to evaluate the accuracy of deep learning-based integrated tooth models (ITMs) by merging intraoral scans and cone-beam computed tomography (CBCT) scans for three-dimensional (3D) evaluation of root position during orthodontic treatment and to compare the fabrication process of integrated tooth models (ITMs) with manual method. Material and methods Intraoral scans and corresponding CBCT scans before and after treatment were obtained from 15 patients who completed orthodontic treatment with premolar extraction. A total of 600 ITMs were generated using deep learning technology and manual methods by merging the intraoral scans and CBCT scans at pretreatment. Posttreatment intraoral scans were integrated into the tooth model, and the resulting estimated root positions were compared with the actual root position at posttreatment CBCT. Discrepancies between the estimated and actual root position including average surface differences, arch widths, inter-root distances, and root axis angles were obtained in both the deep learning and manual method, and these measurements were compared between the two methods. Results The average surface differences of estimated and actual ITMs in the manual method were 0.02 mm and 0.03 mm for the maxillary and mandibular arches, respectively. In the deep learning method, the discrepancies were 0.07 mm and 0.08 mm for the maxillary and mandibular arches, respectively. For the measurements of arch widths, inter-root distances, and root axis angles, there were no significant differences between estimated and actual models both in the manual and in the deep learning methods, except for some measurements. Comparing the two methods, only three measurements showed significant differences. The procedure times taken to obtain the measurements were longer in the manual method than in the deep learning method. Conclusion Both deep learning and manual methods showed similar accuracy in the integration of intraoral scans and CBCT images. Considering time and efficiency, the deep learning automatic method for ITMs is highly recommended for clinical practice.
Pevonedistat, the first small-molecule inhibitor of NEDD8-activating enzyme, has demonstrated clinical activity in Western patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). We report findings from a phase 1/1b study in East Asian patients with AML or MDS, conducted to evaluate the safety/tolerability and characterize the pharmacokinetics of pevonedistat, alone or in combination with azacitidine, in this population, and determine the recommended phase 2/3 dose for pevonedistat plus azacitidine. Twenty-three adult patients with very high/high/intermediate-risk AML or MDS were enrolled in Japan, South Korea and Taiwan. All 23 patients experienced at least one grade ≥ 3 treatment-emergent adverse event. One patient in the combination cohort reported a dose-limiting toxicity. Eighteen patients discontinued treatment; in nine patients, discontinuation was due to progressive disease. Three patients died on study of causes considered unrelated to study drugs. Pevonedistat exhibited linear pharmacokinetics over the dose range of 10–44 mg/m ² , with minimal accumulation following multiple-dose administration. An objective response was achieved by 5/11 (45%) response-evaluable patients in the pevonedistat plus azacitidine arm (all with AML), and 0 in the single-agent pevonedistat arm. This study showed that the pharmacokinetic and safety profiles of pevonedistat plus azacitidine in East Asian patients were similar to those observed in Western patients as previously reported. The recommended Phase 2/3 dose (RP2/3D) of pevonedistat was determined to be 20 mg/m ² for co-administration with azacitidine 75 mg/m ² in Phase 2/3 studies, which was identical to the RP2/3D established in Western patients. Trial registration : NCT02782468 25 May 2016.
Background Heat generation in a drug delivery carrier by exposure to near-infrared (NIR) light with excellent tissue transmittance is an effective strategy for drug release and tumor therapy. Because liposomes have amphiphilic properties, they are useful as drug carriers. Liposomes are also very suitable for drug delivery strategies using heat generation by NIR laser because lipid bilayers are easily broken by heat. Thermally generated bubbles from liposomes not only induce drug release, but also enable ultrasound imaging. Methods Melanin, perfluorohexane (PFH), and 5-fluorouracil (5-FU)-loaded liposomes (melanin@PFH@5-FU-liposomes) that can generate heat and bubble by NIR laser irradiation were prepared by a thin film method. Conversion of light to heat and bubble generation of melanin@PFH@5-FU-liposomes were evaluated using an infrared (IR) thermal imaging camera and an ultrasound imaging system both in vitro and in vivo . To investigate tumor therapeutic effect, NIR laser of 808 nm was used to irradiate tumor site for 10 min after injecting melanin@PFH@5-FU-liposome into tail veins of CT26-bearing mice. Results Melanin@PFH@5-FU-liposomes showed a spherical shape with a size of 209.6 ± 4.3 nm. Upon NIR laser irradiation, melanin@PFH@5-FU-liposomes exhibited effective temperature increase both in vitro and in vivo . In this regard, temperature increase caused a phase transition of PFH to induce bubble generation dramatically, resulting in effective drug release behavior and ultrasound imaging. The temperature of the tumor site was increased to 52 t and contrast was greatly enhanced during ultrasound imaging due to the generation of bubble. More importantly, tumor growth was effectively inhibited by injection of melanin@PFH@5-FU-liposomes with laser irradiation. Conclusions Based on intrinsic photothermal properties of melanin and phase transition properties of PFH, melanin@PFH@5-FU-liposomes exhibited effective heat and bubble generation upon NIR laser irradiation. The elevated temperature induced bubble generation, resulting in contrast enhancement of ultrasound imaging. Melanin@PFH@5-FU-liposomes under NIR laser irradiation induced the death of cancer cells, thereby effectively inhibiting tumor growth. These results suggest that melanin@PFH@5-FU-liposomes can be utilized as a promising agent for photothermal tumor therapy and ultrasound imaging.
As a toxic substance, 4-n-nonylphenol (4-n-NP) or 4-nonylphenol (4-NP) is widely present in the environment. 4-n-NP is a single substance with a linear-alkyl side chain, but 4-NP usually refers to a random mixture containing various branched types. Unfortunately, human risk assessment and/or exposure level analysis for 4-n-NP (or 4-NP) were almost nonexistent, and related research was urgently needed. This study aimed to analyze the various exposures of 4-n-NP (or 4-NP) through development of a physiologically based-pharmacokinetic (PBPK) model considering gender difference in pharmacokinetics of 4-n-NP and its application to human risk assessment studies. A PBPK model was newly developed considering gender differences in 4-n-NP pharmacokinetics and applied to a human risk assessment for each gender. Exposure analysis was performed using a PBPK model that considered gender differences in 4-n-NP (or 4-NP) exposure and high variabilities in several countries. Furthermore, an extended application was attempted as a human risk assessment for random mixture 4-NP, which is difficult to accurately evaluate in reality. External-exposure and margin-of-safety estimated with the same internal exposure amount differed between genders, meaning the need for a differentiated risk assessment considering gender. Exposure analysis based on biomonitoring data confirmed large variability in exposure to 4-n-NP (or 4-NP) by country, group, and period. External-exposures estimated using PBPK model varied widely, ranging from 0.039 to 63.875 mg/kg/day (for 4-n-NP or 4-NP). By country, 4-n-NP (or 4-NP) exposure was higher in females than in males and the margin-of-safety tended to be low. Overall, exposure to 4-n-NP (or 4-NP) in populations was largely not safe, suggesting need for ongoing management and monitoring. Considering low in vivo accumulation confirmed by PBPK model, risk reduction of 4-n-NP is possible by reducing its use.
To meet strong emission regulations such as Euro-7, which is expected to be implemented in 2025. The multiple-injection strategy is one of well-known solutions to reduce exhaust gas and improve combustion performance on GDI engine. In order to realize multiple-injection strategy, it is necessary to secure excellent flow rate repeatability within short period. Therefore, the purpose of this study was to analyze the flow rate repeatability of GDI injector under various multiple injection conditions and to correlate with needle behavior of GDI injector and flow rate repeatability. To analyze flow rate repeatability, the injection rate data was obtained by the Bosch method and the individual flow rates of 110 shots were analyzed under several experimental conditions. The movements of the ball and armature inside the injector were visualized using the X-ray phase contrast imaging (XPCI) technique, and the individual behaviors of the ball and the armature were quantitatively analyzed by image post-processing analysis. In this study were used two test GDI injectors with same structure. Whereas Flow rate results were different on shorter dwell time conditions. This study revealed that a specific injector had unstable injection rate and worse Shot to Shot (STS) deviation under dwell time 0.7 ms. In addition, armature bouncing appeared in a specific GDI injector. This armature bouncing affects unstable flow rate characteristics because when armature lift up again, the position of armature was different at every time.
The heterostructure between two-dimensional (2D) metal sulfides and metal oxides is one of the effective strategies to enhance the gas sensing performance owing to their unique electronic properties at the interfaces. In this study, we focus on enhancing gas sensing response under highly humid conditions using 2D tin sulfides (SnS and SnS2)–SnO2 heterostructures in form of vertically aligned 1D nanostructures. They exhibit superior gas response and recovery to 1 ppm NO2 under 90% of relative humidity (RH90) with an extremely low theoretical detection limit of 1.67 ppt. Furthermore, we demonstrate the gas sensor arrays using noble metal catalyst decoration which exhibit diverse selectivity toward various gases. We simulate the gas adsorption/desorption mechanism to reveal the mechanism of gas sensing properties of sulfurized SnO2 NRs under RH90. As a result, a higher preference of H2O physisorption over chemisorption by tin sulfides provided empty active sites even under RH90, yielding higher gas response than pristine SnO2 whose active sites are fully occupied by H2O under RH90. This work will provide a new perspective to the development of gas sensors suitable for high RH conditions like the examination of exhaled breath.
Brine disposal and energy consumption are the two most important challenges for desalination. In this study, a new hybrid desalination process integrating batch reverse osmosis (BRO) and adsorption desalination (AD) is proposed for high recovery and energy efficiency. Hybrid BRO-AD produces distilled water and drinking water simultaneously. It also provides cooling. Simulation results reveal high recovery of 96.0 % and 64.8 %, low specific electrical energy consumption of 0.536 and 2.089 kWh/m³, specific thermal energy consumption of 182.3 and 312.2 kWh/m³, with cooling power generation of 302.5 and 139.5 kW achieved in brackish water and seawater desalination, respectively. The thermal energy consumption can be supplied by low-grade waste heat. The effects of feed concentrations in the ranges of 1–8 g/L (for brackish water) and 30–44 g/L (for seawater) and feed temperature of 25–35 °C are also investigated. The performance of the BRO-AD is compared against non-hybrid BRO and AD systems. The study shows that the BRO-AD hybrid achieves higher recovery than BRO, while reducing the large amounts of adsorbent material needed by AD. With its versatile characteristics, the BRO-AD hybrid system can be considered a breakthrough step in minimal/zero liquid discharge.
We count the number of isomorphism classes of degree d-twists of some polarized abelian varieties of dimension g over finite fields where either g is an odd prime or else g=2. This can be seen as a higher dimensional analogue of the counting problem for the case of elliptic curves.
The dispersion of platinum nanoparticles over B/N functionalized carbon nanofibers (CNFs) is studied using a simple electrospinning technique. The ratio of boron and nitrogen for the uniform and agglomeration-free Pt loading is optimized. Among the prepared electrocatalysts, Pt-loaded CNFs with an equal amount of B and N (Pt/HCNF-III) exhibit remarkable electrocatalytic activity towards the oxygen reduction, methanol oxidation, and hydrogen evolution reactions. Pt/HCNF-III provides a significant ECSA (62.57 m²/gm). The Pt/HCNF-III being an efficient ORR electrocatalyst follows a 4-electron pathway and renders high half-wave potential. Moreover, Pt/HCNF-III displays relatively high mass activities of 324.77 and 6.17 A g⁻¹ during MOR and HER, respectively. Pt/HCNF-III also demands a minimal overpotential (54 mV) and Tafel slope (33 mV dec⁻¹) during HER. Thus, a unique phenomenon of dopant-induced metal support interaction has enhanced the electrocatalytic activity, stability, and selectivity of the prepared electrocatalysts.
In this study, a novel MoS2/Bi2MoO6 composite photocatalyst, which was further sensitized using graphene quantum dots (GQDs), was developed to realize multiple photocatalytic applications in antibiotic remediation and Cr(VI) reduction. A simple chemical mixing procedure was used to prepare the GQD-MoS2/BMO composite photocatalyst, which was comprehensively characterized to confirm the structural purity, morphology, and distribution of GQDs on the MoS2/BMO catalyst. The enhanced charge separation and channeling of fast electron migration were confirmed by photocurrent and impedance measurements obtained for the 5 GQD-30 MoS2/BMO ternary catalyst system. The photoefficiency observed for the degradation of ofloxacin and reduction of Cr(VI) was 99.5% and 97.2% after 100 and 30 min, respectively, of photochemical reaction under visible-light irradiation. The reaction rate with 5 GQD-30 MoS2/BMO was 14.3- and 1.8-fold higher than that using pristine Bi2MoO6 and 30 MoS2/BMO photocatalysts, respectively. Persulfate (3 mM) improved the photo-oxidation of ofloxacin, with > 80% degradation occurring in the first 20 min. The excellent photocatalytic performance is attributed to the improved light absorption owing to the GQDs and the promotion of charge transfer between Bi2MoO6 and MoS2 via GQDs through a Z-scheme mechanism and the electron-attracting properties of the GQDs.
As the uncertainty and importance of securing resources increase, the nexus concept is used for integrated sustainable use management planning. In particular, because protected farms are most affected by temperature change, the connection between the heating temperature variable and resources must be analyzed. In this study, a water-energy-food-carbon nexus model that reflected the agricultural characteristics of protected farms was constructed. The crop yield, irrigation amount, and heating energy were simulated, and a sensitivity analysis was performed according to climate change scenarios and heating temperature variables. There was no significant decrease in the yield of food resources even at heating temperatures lower than 12 °C. In contrast, the growing period shortened as the heating temperature increased above 12 °C, which decreased the irrigation amount but tended to increase the heating energy. In addition, lowering the heating temperature standard from 12 °C to 8 °C (or less) is suitable for efficient resource management.
An additive in hybrid perovskite is playing a vital role in the increment of power conversion efficiency (PCE), stability, and reproducibility of perovskite solar cells (PVSCs). Although, single-phase α-FAPbI3 perovskite has an ideal band gap but is continuously transforming to δ–FAPbI3, which is non-photoactive. Here, we controlled the methylammonium (MA) and formamidinium (FA) ratio in the (MAxFA1-x)PbI3 perovskite composition and tuned its morphology with the help of the thioacetamide (TAA) Lewis base additive. The optimum MA:FA ratio and fine-tuning of TAA additive result in a highly crystalline, large grain size and smooth surface of the (MA0.5FA0.5)PbI3 perovskite film. These highly uniform thin films with 850 nm grain size offered a superior interaction between the perovskite material and the electron transport layer (ETL) and a longer lifetime yielding a high PCE. The (MA0.5FA0.5)PbI3+1% TAA-based champion device exhibited the highest PCE of 21.29% for a small area (0.09 cm²) and 18.32% PCE for a large area (1 cm²). The TAA-assisted devices exhibited high stability with >85% retention over 500 h. These results suggest that the (MA0.5FA0.5)PbI3 along with the 1% TAA additive is a promising absorber layer that can produce >21% PCE.
To improve the performance of solid-state lithium batteries (SSLB), solid-state succinonitrile (SCN) is incorporated into a composite solid electrolyte (CSE) comprising Al-doped LLZO (Li6.4Al0.2La3Zr2O12), poly(ethylene oxide) (PEO), and lithium salts, thereby conferring flexibility to the CSE. SCN acts as a solid-state plasticizer that increased the ion conduction and interfacial control between the materials. The flexible CSE sheet exhibits a high ionic conductivity of 2.5 × 10⁻⁴ S cm⁻¹ at 40 °C and a wide potential window of ∼5.2 V vs. Li/Li⁺. The solid SCN provides new synergistic properties such as an additional ion conduction path and suppresses PEO oxidation. When the CSE with 7 wt% SCN is utilized as the cathode layer and solid electrolyte layer in SSLBs, instead of the liquid electrolyte, a discharge capacity of approximately 130 mAh g⁻¹ is realized at 45 °C and 0.1C, whilst a capacity retention rate of 90% and a coulombic efficiency of 99% are obtained over 100 cycles. A 3-stack bipolar cell is fabricated to evaluate the mechanical properties of the flexible CSE sheet, demonstrating stable cycle performance over 50 cycles without any short circuiting or leakage current.
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2,650 members
Kwang Il Nam
  • Department of Anatomy
Zahid Parvez Sukhan
  • Department of Fisheries Science
Dong Hoon Lee
  • Department of Otolaryngology and Head and Neck Surgery
Narayan Chandra Paul
  • Department of Integrative Food Bioscience & Biotechnology
Oksoo Han
  • Department of Molecular Biotechnology
Yongbong-Ro 77, Buk-Gu, 500-757, Gwangju, South Korea
Head of institution
JEE, Byung-moon