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

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).

Nanotechnology-Assisted Biosensors for the Detection of Viral Nucleic Acids: An Overview.

The accurate and rapid diagnosis of viral diseases has garnered increasing attention in the field of biosensors. The development of highly sensitive, selective, and accessible biosensors is crucial for early disease detection and preventing mortality. However, developing biosensors optimized for viral disease diagnosis has several limitations, including the accurate detection of mutations. For decades, nanotechnology has been applied in numerous biological fields such as biosensors, bioelectronics, and regenerative medicine. Nanotechnology offers a promising strategy to address the current limitations of conventional viral nucleic acid-based biosensors. The implementation of nanotechnologies, such as functional nanomaterials, nanoplatform-fabrication techniques, and surface nanoengineering, to biosensors has not only improved the performance of biosensors but has also expanded the range of sensing targets. Therefore, a deep understanding of the combination of nanotechnologies and biosensors is required to prepare for sanitary emergencies such as the recent COVID-19 pandemic. In this review, we provide interdisciplinary information on nanotechnology-assisted biosensors. First, representative nanotechnologies for biosensors are discussed, after which this review summarizes various nanotechnology-assisted viral nucleic acid biosensors. Therefore, we expect that this review will provide a valuable basis for the development of novel viral nucleic acid biosensors.

Intrinsic atmospheric circulation patterns associated with high PM2.5 concentration days in South Korea during the cold season.

Based on observation data and a novel K-mean clustering method, we investigated whether intrinsic atmospheric circulation patterns are related with the occurrence of high particulate matter (PM) concentration days (diameters less than or equal to 2.5 µm (PM2.5)), in Seoul, South Korea, during the cold season (December to March). A simple composite map shows that weak horizontal and vertical ventilation over the Korean Peninsula can cause high PM2.5 concentration (High_PM2.5) days. Also, atmospheric circulations are quite different between one day of High_PM2.5 and periods longer than two days. We also found that two intrinsic atmospheric circulation patterns in Asia, which were obtained by adopting K-mean clustering to the daily 850 hPa geopotential height anomalies for 2005-2020, were associated with High_PM2.5 days. These results indicate that High_PM2.5 days in Seoul, South Korea, occur as a result of intrinsic atmospheric circulation patterns, therefore, they are unavoidable unless the anthropogenic emission sources over the Korean Peninsula, East Asia, or both are reduced. In addition, these two intrinsic atmospheric circulation patterns are more prominent for periods longer than two days while there are no favorable intrinsic atmospheric circulation patterns to induce one day of High_PM2.5, which indicates that a single day of High_PM2.5 tends to occur by a stochastic atmospheric circulation rather than the intrinsic atmospheric circulation patterns.

Ultrasensitive Electrochemical Detection of Mutated Viral RNAs with Single-Nucleotide Resolution Using a Nanoporous Electrode Array (NPEA).

The detection of nucleic acids and their mutation derivatives is vital for biomedical science and applications. Although many nucleic acid biosensors have been developed, they often require pretreatment processes, such as target amplification and tagging probes to nucleic acids. Moreover, current biosensors typically cannot detect sequence-specific mutations in the targeted nucleic acids. To address the above problems, herein, we developed an electrochemical nanobiosensing system using a phenomenon comprising metal ion intercalation into the targeted mismatched double-stranded nucleic acids and a homogeneous Au nanoporous electrode array (Au NPEA) to obtain (i) sensitive detection of viral RNA without conventional tagging and amplifying processes, (ii) determination of viral mutation occurrence in a simple detection manner, and (iii) multiplexed detection of several RNA targets simultaneously. As a proof-of-concept demonstration, a SARS-CoV-2 viral RNA and its mutation derivative were used in this study. Our developed nanobiosensor exhibited highly sensitive detection of SARS-CoV-2 RNA (∼1 fM detection limit) without tagging and amplifying steps. In addition, a single point mutation of SARS-CoV-2 RNA was detected in a one-step analysis. Furthermore, multiplexed detection of several SARS-CoV-2 RNAs was successfully demonstrated using a single chip with four combinatorial NPEAs generated by a 3D printing technique. Collectively, our developed nanobiosensor provides a promising platform technology capable of detecting various nucleic acids and their mutation derivatives in highly sensitive, simple, and time-effective manners for point-of-care biosensing.

Clustered Regularly Interspaced Short Palindromic Repeats-Mediated Amplification-Free Detection of Viral DNAs Using Surface-Enhanced Raman Spectroscopy-Active Nanoarray.

Nucleic acid biomarkers have been widely used to detect various viral-associated diseases, including the recent pandemic COVID-19. The CRISPR-Cas-based trans-activating phenomenon has shown excellent potential for developing sensitive and selective detection of nucleic acids. However, the nucleic acid amplification steps are typically required when sensitive and selective monitoring of the target nucleic acid is needed. To overcome the aforementioned challenges, we developed a CRISPR-Cas12a-based nucleic acid amplification-free biosensor by a surface-enhanced Raman spectroscopy (SERS)-assisted ultrasensitive detection system. We integrated the activated CRISPR-Cas12a by viral DNA with a Raman-sensitive system composed of ssDNA-immobilized Raman probe-functionalized Au nanoparticles (RAuNPs) on the graphene oxide (GO)/triangle Au nanoflower array. Using this CRISPR-based Raman-sensitive system improved the detection sensitivity of the multiviral DNAs such as hepatitis B virus (HBV), human papillomavirus 16 (HPV-16), and HPV-18 with an extremely low detection limit and vast detection range from 1 aM to 100 pM without the amplification steps. We suggest that this ultrasensitive amplification-free detection system for nucleic acids can be widely applied to the precise and early diagnosis of viral infections, cancers, and several genetic diseases.