Horseradish Peroxidase-Encapsulated Fluorescent Bio-Nanoparticle for Ultra-Sensitive and Easy Detection of Hydrogen Peroxide.

Hydrogen peroxide (H2O2) has been a fascinating target in various chemical, biological, clinical, and industrial fields. Several types of fluorescent protein-stabilized gold nanoclusters (protein-AuNCs) have been developed for sensitive and easy detection of H2O2. However, its low sensitivity makes is difficult to measure negligible concentrations of H2O2. Therefore, to overcome this limitation, we developed a horseradish peroxidase-encapsulated fluorescent bio-nanoparticle (HEFBNP), comprising bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and horseradish peroxidase-stabilized gold nanoclusters (HRP-AuNCs). The fabricated HEFBNP can sensitively detect H2O2 owing to its two properties. The first is that HEFBNPs have a continuous two-step fluorescence quenching mechanism, which comes from the heterogenous fluorescence quenching mechanism of HRP-AuNCs and BSA-AuNCs. Second, the proximity of two protein-AuNCs in a single HEFBNP allows a reaction intermediate (•OH) to rapidly reach the adjacent protein-AuNCs. As a result, HEFBNP can improve the overall reaction event and decrease the loss of intermediate in the solution. Due to the continuous quenching mechanism and effective reaction event, a HEFBNP-based sensing system can measure very low concentrations of H2O2 up to 0.5 nM and show good selectivity. Furthermore, we design a glass-based microfluidic device to make it easier use HEFBNP, which allowed us to detect H2O2 with the naked eye. Overall, the proposed H2O2 sensing system is expected to be an easy and highly sensitive on-site detection tool in chemistry, biology, clinics, and industry fields.

Pumpless three-dimensional photo paper-based microfluidic analytical device for automatic detection of thioredoxin-1 using enzyme-linked immunosorbent assay.

Microfluidic-based biosensors have been developed for their precise automatic reaction control. However, these biosensors require external devices that are difficult to transport and use. To overcome this disadvantage, our group made an easy-to-use, cheap, and light pumpless three-dimensional photo paper-based microfluidic analytical device (3D-µPAD; weight: 1.5 g). Unlike conventional paper-based microfluidic analytical devices, the 3D-µPAD can be used to control fluid flow in a 3D manner, thus allowing sophisticated multi-step reaction control. This device can control fluid flow speed and direction accurately using only the capillary-driven flow without an external device like a pump. The flow speed is controlled by the width of the microfluidic channel and its surface property. In addition, fluid speed control and 3D-bridge structure enable the control of fluid flow direction. Using these methods, multi-step enzyme-linked immunosorbent assay (ELISA) can be done automatically in sequence by injecting solutions (sample, washing, and enzyme's substrate) at the same time in the 3D-µPAD. All the steps can be performed in 14 min, and data can be analyzed immediately. To test this device, thioredoxin-1 (Trx-1), a biomarker of breast cancer, is used as the target. In the 3D-µPAD, it can detect 0-200 ng/mL of Trx-1, and the prepared 3D-µPAD Trx-1 sensor displays excellent selectivity. Moreover, by analyzing the concentration of Trx-1 in real patients and healthy individuals' blood serum samples using the 3D-µPAD, and comparing results to ELISA, it can be confirmed that the 3D-µPAD is a good tool for cancer diagnosis.

Noble Metal Nanomaterial-Based Biosensors for Electrochemical and Optical Detection of Viruses Causing Respiratory Illnesses.

Noble metal nanomaterials, such as gold, silver, and platinum, have been studied extensively in broad scientific fields because of their unique properties, including superior conductivity, plasmonic property, and biocompatibility. Due to their unique properties, researchers have used them to fabricate biosensors. Recently, biosensors for detecting respiratory illness-inducing viruses have gained attention after the global outbreak of coronavirus disease (COVID-19). In this mini-review, we discuss noble metal nanomaterials and associated biosensors for detecting respiratory illness-causing viruses, including SARS-CoV-2, using electrochemical and optical detection techniques. this review will provide interdisciplinary knowledge about the application of noble metal nanomaterials to the biomedical field.

Electrochemical H2O2 biosensor based on horseradish peroxidase encapsulated protein nanoparticles with reduced graphene oxide-modified gold electrode.

In this study, an electrochemical biosensor composed of a horseradish peroxidase (HRP)-encapsulated protein nanoparticles (HEPNP) was fabricated for the sensitive and selective detection of H2O2. The HEPNP has a three-dimensional structure that can contain a large amount of HRP; therefore, HEPNP can amplify the electrochemical signals necessary for the detection of H2O2. Furthermore, reduced graphene oxide (rGO) was used to increase the efficiency of electron transfer from the HEPNP to an electrode, which could enhance the electrochemical signal. This biosensor showed a sensitive electrochemical performance for detection of H2O2 with signals in the range from 0.01-100 µM, and it could detect low concentrations up to 0.01 µM. Furthermore, this biosensor was operated against interferences from glucose, ascorbic acid, and uric acid. In addition, this fabricated H2O2 biosensor showed selective detection performance in human blood serum. Therefore, the proposed biosensor could promote the sensitive and selective detection of H2O2 in clinical applications.

Pump-Free Glass-Based Capillary Microfluidic Immuno-Assay Chip for Electrochemical Detection of Prostate-Specific Antigen.

Immuno-assay is one of diagnostic methods that usually measures biomarkers associated with cancers. However, this method is complex and take a long time to analyze. To overcome these disadvantages, many immuno-sensing chips have been designed and developed. However, these devices still require an external pump or electrical source. In this study, our group fabricated a capillary microfluidic device using glass and adhesive polyethylene terephthalate (PET) film, which were designed by simply patterning and cutting to make the microfluidic capillary channels. Using capillary force alone, glass microfluidic chip can control the speed of fluid-flow and the flow sequence by adjusting the width of the channel and design. In addition, each flow can push out other flow without mixing. The glass-based capillary microfluidic chip (GCMC) can automatically perform immunoassay in regular order without external devices and it provide an electrochemical signal analysis in an average of 2 min. The concentration of the prostate-specific antigen (PSA), a biomarker of prostate cancer, was measured by cyclic voltammetry (CV). In conclusion, GCMC can detect between a range of 100 pg/ml to 1 µg/ml of PSA and provide high selectivity to PSA.

Engineering Pseudomonas putida KT2440 to convert 2,3-butanediol to mevalonate.

Biological production of 2,3-butanediol (2,3-BDO), a C4 platform chemical, has been studied recently, but the high cost of separation and purification before chemical conversion is substantial. To overcome this obstacle, we have conducted a study to convert 2,3-BDO to mevalonate, a terpenoid intermediate, using recombinant Pseudomonas putida and this biological process won't need the separation and purification process of 2,3-BDO. The production of mevalonate when 2,3-BDO was used as a substrate was 6.61 and 8.44 times higher than when glucose and glycerol were used as substrates under the same conditions, respectively. Lower aeration contributed to higher yields of mevalonate in otherwise identical conditions. The maximum mevalonate production on the shaking flask scale was about 2.21 g/L, in this study (product yield was 0.295, 27% of theoretical yield (1.10)). This study was the first successful attempt for mevalonate production by P. putida using 2,3-BDO as the sole carbon source and presented a new metabolic engineering tool and biological process for mevalonate synthesis.

Detection of thioredoxin-1 using ultra-sensitive ELISA with enzyme-encapsulated human serum albumin nanoparticle.

Many methods for early diagnosis of the disease use biomarker tests, which measure indicators of biological state in body fluids or blood. However, a limitation of these methods is their low sensitivity to biomarkers. In this study, human serum albumin (HSA) based nanoparticles capable of encapsulating excess horseradish peroxidase (HRP) are synthesized and applied to the development of enzyme-linked immunosorbent assay (ELISA) kit with ultra-high sensitivity. The size of the nanoparticles and the amount of encapsulated enzyme are controlled by varying the synthesis conditions of pH and protein concentration, and the surface of the nanoparticles is modified with protein A (proA) to immobilize antibodies to the nanoparticles by self-assembly. Using the synthesized nanoparticles, the biomarker of breast cancer, thioredoxin-1, can be measured in the range of 10 fM to 100 pM by direct sandwich ELISA, which is 105 times more sensitive than conventional methods.

Musculoskeletal Disorders and Agricultural Risk Factors Among Korean Farmers.

Farming is a strenuous occupation with various health risks, with musculoskeletal disorders (MSDs) being some of the most common. The risk factors for MSDs among Korean farmers are not well understood. Data were obtained from the Korean Farmers' Occupational Disease and Injury Survey (2012), which interviewed 16,113 participants regarding their demographic profiles, self-reported MSDs, and agricultural characteristics. Multiple logistic regression analysis was used to identify the risk factors for MSDs. Subjects reported MSDs in the neck or upper extremities (5.89%), lower extremities (19.62%), and back (26.9%). Working in animal husbandry significantly increased the risk of MSDs in the neck/upper extremities, compared with irrigation farming (odds ratio: 1.837, 95% confidence interval: 1.130-2.987). The risk of MSDs increased significantly with number of years of farming, after adjusting for age and sex (neck/upper extremities, P for trend = .0002; lower extremities, <.001; back, <.001). Agriculture type, years of farming, and ergonomic factors increased the risk of MSDs among Korean farmers.