Showing papers by "Kwangwoon University published in 2022"

Fabrication of MERS-nanovesicle biosensor composed of multi-functional DNA aptamer/graphene-MoS2 nanocomposite based on electrochemical and surface-enhanced Raman spectroscopy.

Abstract: Middle East respiratory syndrome coronavirus (MERS-CoV) is one of the most harmful viruses for humans in nowadays. To prevent the spread of MERS-CoV, a valid detection method is highly needed. For the first time, a MERS-nanovesicle (NV) biosensor composed of multi-functional DNA aptamer and graphene oxide encapsulated molybdenum disulfide (GO-MoS2) hybrid nanocomposite was fabricated based on electrochemical (EC) and surface-enhanced Raman spectroscopy (SERS) techniques. The MERS-NV aptamer was designed for specifically binding to the spike protein on MERS-NVs and it is prepared using the systematic evolution of ligands by exponential enrichment (SELEX) technique. For constructing a multi-functional MERS aptamer (MF-aptamer), the prepared aptamer was connected to the DNA 3-way junction (3WJ) structure. DNA 3WJ has the three arms that can connect the three individual functional groups including MERS aptamer (bioprobe), methylene blue (signal reporter) and thiol group (linker) Then, GO-MoS2 hybrid nanocomposite was prepared for the substrate of EC/SERS-based MERS-NV biosensor construction. Then, the assembled multifunctional (MF) DNA aptamer was immobilized on GO-MoS2. The proposed biosensor can detect MERS-NVs not only in a phosphate-buffered saline (PBS) solution (SERS LOD: 0.176 pg/ml, EIS LOD: 0.405 pg/ml) but also in diluted 10% saliva (SERS LOD: 0.525 pg/ml, EIS LOD: 0.645 pg/ml).

Nanocarrier cancer therapeutics with functional stimuli-responsive mechanisms

Abstract: Presently, nanocarriers (NCs) have gained huge attention for their structural ability, good biocompatibility, and biodegradability. The development of effective NCs with stimuli-responsive properties has acquired a huge interest among scientists. When developing drug delivery NCs, the fundamental goal is to tackle the delivery-related problems associated with standard chemotherapy and to carry medicines to the intended sites of action while avoiding undesirable side effects. These nanocarriers were able of delivering drugs to tumors through regulating their pH, temperature, enzyme responsiveness. With the use of nanocarriers, chemotherapeutic drugs could be supplied to tumors more accurately that can equally encapsulate and deliver them. Material carriers for chemotherapeutic medicines are discussed in this review keeping in viewpoint of the structural properties and targeting methods that make these carriers more therapeutically effective, in addition to metabolic pathways triggered by drug-loaded NCs. Largely, the development of NCs countering to endogenous and exogenous stimuli in tumor regions and understanding of mechanisms would encourage the progress for tumor therapy and precision diagnosis in future.

Non-thermal argon plasma jets of various lengths for selective reactive oxygen and nitrogen species production

Abstract: Plasma jets simultaneously create a wide range of reactive oxygen species (ROS) and reactive nitrogen species (RNS), making selective production challenging. In this study, an attempt was made to address this problem by adjusting the downstream length of the plasma jet to regulate reactive species production in an AC-driven argon plasma jet. Jets with short downstream lengths are dominated by RNS, whereas longer ones are dominated by ROS. The energy impact collision between energetic electrons and diffused ambient air is primarily responsible for the generation of RNS in argon plasma. Short plasma jets have a higher electron temperature in the plasma effluent, allowing for better excitation and ionization of N2 molecules. In contrast, in longer jets, electrons transfer most of their energy to neutrals and moisture, even before the diffusion of ambient air. Thus, the production of OH radicals and H2O2 is dominant in longer plasma jets. Further, the ratio of NO2- to H2O2 in plasma-activated water decreased from 1.8 to 0.07, as the downstream length was increased from 1 cm to 10 cm. RNS-enriched short plasma jets are appropriate for immune cell activation, jets of intermediate length are suitable for gold nanoparticle formation because of the synergistic action of ROS and electron energy, and ROS-dominated longer plasma jets are excellent for methylene blue degradation. These findings are applicable to the design of plasma devices in which the generation of ROS and RNS in practical quantities is required to realize plasma technology for a wide range of applications.

Image polaritons in van der Waals crystals

Abstract: Abstract Polaritonic modes in low-dimensional materials enable strong light–matter interactions and the manipulation of light on nanometer length scales. Very recently, a new class of polaritons has attracted considerable interest in nanophotonics: image polaritons in van der Waals crystals, manifesting when a polaritonic material is in close proximity to a highly conductive metal, so that the polaritonic mode couples with its mirror image. Image modes constitute an appealing nanophotonic platform, providing an unparalleled degree of optical field compression into nanometric volumes while exhibiting lower normalized propagation loss compared to conventional polariton modes in van der Waals crystals on nonmetallic substrates. Moreover, the ultra-compressed image modes provide access to the nonlocal regime of light–matter interaction. In this review, we systematically overview the young, yet rapidly growing, field of image polaritons. More specifically, we discuss the dispersion properties of image modes, showcase the diversity of the available polaritons in various van der Waals materials, and highlight experimental breakthroughs owing to the unique properties of image polaritons.

Energy-efficient glucose recovery from chestnut shell by optimization of NaOH pretreatment at room temperature and application to bioethanol production

Abstract: Biofuel policies are currently being implemented globally to reduce greenhouse gas emissions. The recent European regulation, Renewable Energy Directive (RED) II, states that renewable resources should be used as raw materials. In this study, chestnut shell (CNS), a food processing residue, was utilized as a feedstock for bioethanol production. Statistical optimization was performed to improve biomass-to-glucose conversion (BtG) from the CNS. In order to design an energy-efficient process, the pretreatment was fixed at room temperature in the numerical optimization. The optimal conditions derived from the predicted model are as follows: temperature of 25 °C, reaction time of 2.8 h, and NaOH concentration of 1.9% (w/w). Under optimal conditions, both predicted and experimental BtG were 31.0%, while BtG was approximately 3.3-fold improved compared to the control group (without pretreatment). The recovered glucose was utilized for bioethanol fermentation by Saccharomyces cerevisiae K35 and the ethanol yield was achieved to be 98%. Finally, according to the mass balance based on 1000 g CNS, glucose of 310 g can be recovered by the pretreatment; the bioethanol production was approximately 155 g. This strategy suggests a direction to utilize CNS as a potential feedstock for biorefinery through the design of an economical and energy-efficient pretreatment process by lowering the reaction temperature to room temperature.

Application of dielectric barrier discharge plasma for the reduction of non-pathogenic Escherichia coli and E. coli O157:H7 and the quality stability of fresh oysters (Crassostrea gigas)

Abstract: This study focuses on the efficacy of dielectric barrier discharge (DBD) plasma treatment (1.1 kV, 3 mm distance, N2 1.5 L/min) as a non-thermal intervention to reduce non-pathogenic Escherichia coli and E. coli O157:H7 in oysters (Crassostrea gigas). Exposure times of 10–30 min by the plasma against non-pathogenic E. coli and E. coli O157:H7 resulted in a log reduction of 0.31–1.01 and 0.18–0.62, respectively, in fresh oysters. In particular, exposure to DBD plasma for 60 min indicated 2.14 log reduction (99.28% reduction) of non-pathogenic E. coli and 1.19 log reduction (93.54% reduction) of E. coli O157:H7. D1-values for non-pathogenic E. coli and E. coli O157:H7 were 27.78 min and 50.08 min, respectively (R2 ≥ 0.98 by using a first-order kinetic model). The glycogen content (1.10–1.20 g/100 g) and texture profile (hardness, springiness, cohesiveness, resilience) of samples treated with DBD plasma did not differ significantly from that of the control (p > 0.05). Therefore, exposing oysters to DBD plasma for at least 60 min could be useful for reducing >99% of non-pathogenic E. coli and 90% of E. coli O157:H7 without causing any deleterious changes to the glycogen content and overall texture of fresh oyster.

Microwave detection with various sensitive materials for humidity sensing

Abstract: Most of the humidity or gas sensing researches focus on the optimization of sensitive materials, while the studies of microwave detection focus on its sensitive-field control. It is necessary to implement the cooperative study on microwave detection with different types of sensitive materials for a better understanding of the operation mechanism as well as providing a way for performance enhancement. This study presents the double split-ring resonator as the sensitive electrode, where various sensitive materials, including polymer by pure Polyimide (PI), ceramic composite by PI-TiO2, metal composite by PI-Ag composite, are respectively tested as the sensing materials. The S-parameter is tested as the humidity indicators after coating on the sensitive regions with a strong electric-magnetic field. Owing to the improved dielectric properties by doping strong-polarity TiO2 nanoparticles into PI, the higher sensitivity with the maximum of 880.0 kHz/%RH and 0.322 dB/%RH is realized. The introduction of Ag nanoparticles facilitates the water vapor adsorption and desorption showing the sensitivity of 330.0 kHz/%RH and 0.149 dB/%RH, due to the high active-site density and surface roughness. By analyzing variations in resonant frequency and return loss, the microwave sensing mechanism of different sensitive materials is fully discussed from the perspective of polarization, dielectric property, and sensitive area.

Persistent high macrolide resistance rate and increase of macrolide-resistant ST14 strains among Mycoplasma pneumoniae in South Korea, 2019–2020

Abstract: Expansion of the single sequence type 3 (ST3) was associated with a high macrolide resistance rate among Mycoplasma pneumoniae in Korea during the 2014–2016 epidemic. This study investigates the macrolide resistance rate and genetic diversity of the subsequent epidemic of M. pneumoniae pneumonia in 2019–2020. The culture for M. pneumoniae was developed from 1228 respiratory samples collected from children with pneumonia in four hospitals in Korea between January 2019 and January 2020. Determination of macrolide resistance and multilocus sequence typing analysis were performed on M. pneumoniae isolates. eBURST analysis was applied to estimate the relationships among strains and to assign strains to a clonal complex. M. pneumoniae was cultured in 93 (7.6%) of 1228 clinical samples. The overall macrolide resistance rate of M. pneumoniae strains was 78.5% (73/93). Of the nine STs identified, three were novel. The most common ST was ST3 (66 [71.0%]) followed by ST14 (18 [19.4%]) and ST7/ST15 (2 [2.2%] each). Three STs (ST3, ST14, and ST17) exhibited macrolide resistance. The macrolide resistance rates of ST3 and ST14 were 98.5% (65 of 66) and 38.9% (7 of 18), respectively. Compared to the previous outbreak in 2014–2016, the overall macrolide resistance remained high; however, an increasing proportion of macrolide resistance was observed within ST14 strains in 2019–2020.