Linking antigen specific T-cell dynamics in a microfluidic chip to single cell transcription patterns.

A new non-invasive screening profile has been realized that can aid in determining T-cell activation state at single-cell level. Production of activated T-cells with good specificity and stable proliferation is greatly beneficial for advancing adoptive immunotherapy as innate immunological cells are not effective in recognizing and eliminating cancer as expected. The screening method is realized by relating intracellular Ca2+ intensity and motility of T-cells interacting with APC (Antigen Presenting Cells) in a microfluidic chip. The system is tested using APC pulsed with OVA257-264 peptide and its modified affinities (N4, Q4, T4 and V4), and the T-cells from OT-1 mice. In addition, single cell RNA sequencing reveals the activation states of the cells and the clusters from the derived profiles can be indicative of the T-cell activation state. The presented system here can be versatile for a comprehensive application to proceed with T-cell-based immunotherapy and screen the antigen-specific T-cells with excellent efficiency and high proliferation.

Solid-Phase Collateral Cleavage System Based on CRISPR/Cas12 and Its Application toward Facile One-Pot Multiplex Double-Stranded DNA Detection.

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 12 (Cas12) system is attracting interest for its potential as a next-generation nucleic acid detection tool. The system can recognize double-stranded DNA (dsDNA) based on Cas12-CRISPR RNA (crRNA) and induce signal transduction by collateral cleavage. This property is expected to simplify comprehensive genotyping. Here, we report a solid-phase collateral cleavage (SPCC) reaction by CRISPR/Cas12 and its application toward one-pot multiplex dsDNA detection with minimal operational steps. In the sensor, Cas12-crRNA and single-stranded DNA (ssDNA) are immobilized on the sensing surface and act as enzyme and reporter substrates, respectively. We also report a dual-target dsDNA sensor prepared by immobilizing Cas12-crRNA and a fluorophore-labeled ssDNA reporter on separate spots. When a spot captures a target dsDNA sequence, it cleaves the ssDNA reporter on the same spot and reduces its fluorescence by 42.1-57.3%. Crucially, spots targeting different sequences do not show a reduction in fluorescence, thus confirming the one-pot multiplex dsDNA detection by SPCC. Furthermore, the sequence specificity has a two-base resolution, and the detectable concentration for the target dsDNA is at least 10-9 M. In the future, the SPCC-based sensor array could achieve one-pot comprehensive genotyping by using an array spotter as a reagent-immobilizing method.

Portable Electrochemical DNA Sensors Based on Gene Amplification Reactions to Screen and Identify Pathogen and SNPs.

In this paper, we introduce portable sensors based on genetic measurements that can be used in the field for the diagnosis of infectious diseases and disease risk based on SNPs (single nucleotide polymorphisms). In particular, the sensors are based on electrochemical measurements that can be performed with printed electrodes and small measuring devices. Indicator molecules that can bind to nucleic acid molecules in various ways are already known, and some of these molecules have electrochemical activity. First, we investigated the change in their electrochemical responses in a solution system. As a result, we searched for nucleic acid-binding molecules whose current value changes in the presence of DNA. In addition, when we measured the change in the current value, associated with the amplification of specific genes, such as PCR (polymerase chain reaction) and LAMP (loop-mediated isothermal amplification), we found that the current value decreased with the number of amplifications, indicating that specific genes can be monitored electrochemically. Based on this principle, we showed that pathogenic microorganisms and viruses, such as Salmonella, O157 E. coli, hepatitis B virus, periodontal disease bacteria, antibiotic-resistant bacteria and influenza virus, were able to be measured. The method was also applied to the diagnosis of SNPs, such as ApoE (apolipoprotein E), which is a risk factor for Alzheimer's disease. Rapid PCR was available with a microfluidic device, and a simple method was also presented with the isothermal amplification of LAMP.

Deskilled and Rapid Drug-Resistant Gene Detection by Centrifugal Force-Assisted Thermal Convection PCR Device.

Here we report the improved Cyclo olefin polymer (COP) microfluidic chip and polymerase chain reaction (PCR) amplification system for point-of-care testing (POCT) in rapid detection of Carbapenem-resistant Enterobacteriaceae (CRE). The PCR solution and thermal cycling is controlled by the relative gravitational acceleration (7G) only and is expected to pose minimal problem in operation by non-expert users. Detection is based on identifying the presence of carbapenemase encoding gene through the corresponding fluorescence signal after amplification. For preliminary tests, the device has been demonstrated to detect blaIMP-6 from patients stool samples. From the prepared samples, 96.4 fg/µL was detected with good certainty within 15 min (~106 thermocycles,) which is significantly faster than the conventional culture plate method. Moreover, the device is expected to detect other target genes in parallel as determination of the presence of blaNDM-1 and blaOXA-23 from control samples has also been demonstrated. With the rising threat of drug-resistant bacteria in global healthcare, this technology can greatly aid the health sector by enabling the appropriate use of antibiotics, accelerating the treatment of carriers, and suppressing the spread.

Chemically Regulated ROS Generation from Gold Nanoparticles for Enzyme-Free Electrochemiluminescent Immunosensing.

In the present work, we report on an enzyme-free electrochemiluminescent (ECL) immunosensing scheme utilizing the catalytic generation of reactive oxygen species (ROS) from gold nanoparticles (AuNPs) (diameter ≥5 nm) dispersed in aqueous solutions of trishydroxymethylaminomethane (Tris). First, to examine this catalytic pathway in detail, the effects of various factors such as the AuNP size and concentration, dispersant type and concentration, and dissolved oxygen were investigated using the electrochemiluminescence (ECL) of luminol. It was found that the catalytic generation of ROS from AuNPs can be regulated chemically by altering conditions such as the type, concentration, and pH of the solution that the AuNPs are dispersed in. Under the best conditions studied in this work, the AuNPs displayed high catalytic activity toward ROS generation, with an estimated apparent turnover number per AuNP of 0.1 s-1, comparable to those of several common peroxide-producing enzymes. Following these studies, this phenomenon was applied to develop a one-step enzyme-free ECL immunosensor based on sandwiching the target analyte using antibody-conjugated magnetic beads (MB) and AuNPs. Using IgA as a model analyte, the developed immunosensor was able to detect the target in the range of 1 ng/mL to 10 µg/mL, with the lower detection limit being comparable to those of commercial assays for the same target. Altering the antibodies used to modify the MB and AuNPs could further improve the detection limit as well as expand the applicability of this immunoassay to the detection of other analytes.

Sensitive Detection of Glycated Albumin in Human Serum Albumin Using Electrochemiluminescence.

Monitoring of blood glucose content is vital for diabetes patients. The conventional widely used method involves an invasive procedure for blood sampling. In addition, blood glucose measured by this way is affected by immediate food consumption and it does not show accurate baseline blood glucose measurement. Thus, monitoring blood glucose by a noninvasive method that accurately reflects baseline blood glucose content is important. Glycated albumin (GA), a biomarker for diabetes indicating the average blood glucose over 2 weeks, can be used for semilong-term blood glucose monitoring. Detection of GA in saliva is a noninvasive method that alleviates the use of needles for diabetic patients; however, its content in saliva is in the nanomolar range. Therefore, the GA enzymatic detection method was combined with the ECL method for a highly sensitive detection of GA in human serum albumin and in the saliva sample. Here, the standard curve was constructed using model substrate, FZK, between 0.1 and 2 µM, and GA in human serum albumin was measured in this range. Also, we successfully demonstrated the detection limit of 0.1 µM GA in human serum albumin sample using ECL, which has seen improvement of about 70 times more than the colorimetric methods. The detection of GA in real saliva sample suggested that sample dilution of 5 times may be necessary to suppress the ECL quenching effect by impurities.

Centrifugation-Controlled Thermal Convection and Its Application to Rapid Microfluidic Polymerase Chain Reaction Devices.

Here, we report the developed cyclo olefin polymer (COP) microfluidic chip on a fabricated rotating heater stage that utilizes centrifugation-assisted thermal cycle in a ring-structured microchannel for polymerase chain reaction (PCR). The PCR solution could be driven by thermal convection and continuously exchanged high/low temperatures in a ring structured microchannel without the use of typical syringe pump. More importantly, the flow rate was controlled by the relative gravitational acceleration only. The platform enables amplification within 10 min at 5G and has a detection limit of 70.5 pg/channel DNA concentration (ß-actin, 295 bp). The current rotating system is capable of testing four different samples in parallel. The microfluidic chip can be preloaded with the PCR premix solution for on-site utility, and, with all of the features integrated to the system, the test can be conducted without the need for specialized laboratory and trained laboratory staff. In addition, this innovative chemical reaction technique has the potential to be utilized in other micromixing applications.

Carbon-Based Nanomaterials in Biomass-Based Fuel-Fed Fuel Cells.

Environmental and sustainable economical concerns are generating a growing interest in biofuels predominantly produced from biomass. It would be ideal if an energy conversion device could directly extract energy from a sustainable energy resource such as biomass. Unfortunately, up to now, such a direct conversion device produces insufficient power to meet the demand of practical applications. To realize the future of biofuel-fed fuel cells as a green energy conversion device, efforts have been devoted to the development of carbon-based nanomaterials with tunable electronic and surface characteristics to act as efficient metal-free electrocatalysts and/or as supporting matrix for metal-based electrocatalysts. We present here a mini review on the recent advances in carbon-based catalysts for each type of biofuel-fed/biofuel cells that directly/indirectly extract energy from biomass resources, and discuss the challenges and perspectives in this developing field.

Toward the development of smart and low cost point-of-care biosensors based on screen printed electrodes.

Screen printing technology provides a cheap and easy means to fabricate disposable electrochemical devices in bulk quantities which are used for rapid, low-cost, on-site, real-time and recurrent industrial, pharmaceutical or environmental analyses. Recent developments in micro-fabrication and nano-characterization made it possible to screen print reproducible feature on materials including plastics, ceramics and metals. The processed features forms screen-printed disposable biochip (SPDB) upon the application of suitable bio-chemical recognition receptors following appropriate methods. Adequacy of biological and non-biological materials is the key to successful biochip development. We can further improve recognition ability of SPDBs by adopting new screen printed electrode (SPE) configurations. This review covers screen-printing theory with special emphasis on the technical impacts of SPE architectures, surface treatments, operational stability and signal sensitivity. The application of SPE in different areas has also been summarized. The article aims to highlight the state-of-the-art of SPDB at the laboratory scale to enable us in envisaging the deployment of emerging SPDB technology on the commercial scale.

Printable Electrochemical Biosensors: A Focus on Screen-Printed Electrodes and Their Application.

In this review we present electrochemical biosensor developments, focusing on screen-printed electrodes (SPEs) and their applications. In particular, we discuss how SPEs enable simple integration, and the portability needed for on-field applications. First, we briefly discuss the general concept of biosensors and quickly move on to electrochemical biosensors. Drawing from research undertaken in this area, we cover the development of electrochemical DNA biosensors in great detail. Through specific examples, we describe the fabrication and surface modification of printed electrodes for sensitive and selective detection of targeted DNA sequences, as well as integration with reverse transcription-polymerase chain reaction (RT-PCR). For a more rounded approach, we also touch on electrochemical immunosensors and enzyme-based biosensors. Last, we present some electrochemical devices specifically developed for use with SPEs, including USB-powered compact mini potentiostat. The coupling demonstrates the practical use of printable electrode technologies for application at point-of-use. Although tremendous advances have indeed been made in this area, a few challenges remain. One of the main challenges is application of these technologies for on-field analysis, which involves complicated sample matrices.

DEP-On-Go for Simultaneous Sensing of Multiple Heavy Metals Pollutants in Environmental Samples.

We describe a simple and affordable "Disposable electrode printed (DEP)-On-Go" sensing platform for the rapid on-site monitoring of trace heavy metal pollutants in environmental samples for early warning by developing a mobile electrochemical device composed of palm-sized potentiostat and disposable unmodified screen-printed electrode chips. We present the analytical performance of our device for the sensitive detection of major heavy metal ions, namely, mercury, cadmium, lead, arsenic, zinc, and copper with detection limits of 1.5, 2.6, 4.0, 5.0, 14.4, and, 15.5 µg·L-1, respectively. Importantly, the utility of this device is extended to detect multiple heavy metals simultaneously with well-defined voltammograms and similar sensitivity. Finally, "DEP-On-Go" was successfully applied to detect heavy metals in real environmental samples from groundwater, tap water, house dust, soil, and industry-processed rice and noodle foods. We evaluated the efficiency of this system with a linear correlation through inductively coupled plasma mass spectrometry, and the results suggested that this system can be reliable for on-site screening purposes. On-field applications using real samples of groundwater for drinking in the northern parts of India support the easy-to-detect, low-cost (<1 USD), rapid (within 5 min), and reliable detection limit (ppb levels) performance of our device for the on-site detection and monitoring of multiple heavy metals in resource-limited settings.

Optical microscopy imaging for the diagnosis of the pharmacological reaction of mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs).

Quantitative diagnosis of pharmacological chronotropic reactions on mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) was successfully performed by utilizing derivative imaging analysis of videos recorded with a microscope camera at 30 Hz frame rate and 680 × 510 pixel resolution. The imaging analysis algorithm, developed in our lab, generated the contractile profile of the cells which was exploited for drug effect profiling. Six drugs such as isoproterenol (0.01-1 µM), quinidine (2-200 µM), propranolol (0.03-30 µM), verapamil (0.01-1 µM), sotalol (1-100 µM), and acetylsalicylic acid (0.1-10 µM) were administered and the quantitative medication effect was determined. Among the negative chronotropic agents administered, verapamil was found to be the most potent while sotalol was found to be the least potent at the micromolar level. Simultaneous measurement of the field potential and contractile motion in the verapamil effect test showed a coherent result. Moreover, this approach can provide insights into the contraction-relaxation conditions which are not available in the common electrophysiological approach. With these findings, it is expected that this study can aid in providing a simple and reliable in vitro mESC-CM-based screening platform for cardiovascular effect profiling of candidate drugs.

Wireless electrochemiluminescent biosensors: Powering innovation with smartphone technology.

Energy supply and sensor response acquisition can be performed wirelessly, enabling biosensors as Internet of Thing (IoT) tools by linking wireless power supply and electrochemical sensors. Here, we used the electromagnetic induction method to clarify the conditions under which electrochemiluminescence is induced by a simple potential modulation circuit without an integrated circuit on the electrode chip that receives the power. Initially, the potential waveform obtained in a circuit with inductance and capacitance components that resonate with the transmission frequency and a diode for rectification was investigated to clarify the conditions inducing an electrochemiluminescence reaction at the printed electrode. A high-sensitivity complementary metal-oxide semiconductor camera built into the smartphone wirelessly detected the luminescence generated on the electrode chip. The images were quantitatively evaluated using open-source image analysis software which determine the sensitivity of detecting hydrogen peroxide. Glucose oxidase (GOD) encapsulated in a matrix of chitosan polymers and photocrosslinkable polymers was immobilized on a mass-producible and inexpensive printed electrode to maintain high activity. The immobilized membrane suppressed luminescence when immobilized on the working electrode; therefore, the enzyme was immobilized on the counter electrode for glucose measurement over a wide concentration. Thus, luminol electrochemiluminescence was induced on the electrode chip by wireless power supply from a smartphone. Human serum and artificial sweat samples were tested and indicated possibility for actual applications. In this way a fully wireless biosensor was developed with potential as an IoT biosensor.

Miniaturization of CRISPR/Cas12-Based DNA Sensor Array by Non-Contact Printing.

DNA microarrays have been applied for comprehensive genotyping, but remain a drawback in complicated operations. As a solution, we previously reported the solid-phase collateral cleavage (SPCC) system based on the clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 12 (CRISPR/Cas12). Surface-immobilized Cas12-CRISPR RNA (crRNA) can directly hybridize target double-stranded DNA (dsDNA) and subsequently produce a signal via the cleavage of single-stranded DNA (ssDNA) reporter immobilized on the same spot. Therefore, SPCC-based multiplex dsDNA detection can be performed easily. This study reports the miniaturization of SPCC-based spots patterned by a non-contact printer and its performance in comprehensive genotyping on a massively accumulated array. Initially, printing, immobilization, and washing processes of Cas12-crRNA were established to fabricate the non-contact-patterned SPCC-based sensor array. A target dsDNA concentration response was obtained based on the developed sensor array, even with a spot diameter of 0.64 ± 0.05 mm. Also, the limit of detection was 572 pM, 531 pM, and 3.04 nM with 40, 20, and 10 nL-printing of Cas12-crRNA, respectively. Furthermore, the sensor array specifically detected three dsDNA sequences in one-pot multiplexing; therefore, the feasibility of comprehensive genotyping was confirmed. These results demonstrate that our technology can be miniaturized as a CRISPR/Cas12-based microarray by using non-contact printing. In the future, the non-contact-patterned SPCC-based sensor array can be applied as an alternative tool to DNA microarrays.

Surface Modification of Screen-Printed Carbon Electrode through Oxygen Plasma to Enhance Biosensor Sensitivity.

The screen-printed carbon electrode (SPCE) is a useful technology that has been widely used in the practical application of biosensors oriented to point-of-care testing (POCT) due to its characteristics of cost-effectiveness, disposability, miniaturization, wide potential window, and simple electrode design. Compared with gold or platinum electrodes, surface modification is difficult because the carbon surface is chemically or physically stable. Oxygen plasma (O2) can easily produce carboxyl groups on the carbon surface, which act as scaffolds for covalent bonds. However, the effect of O2-plasma treatment on electrode performance remains to be investigated from an electrochemical perspective, and sensor performance can be improved by clarifying the surface conditions of plasma-treated biosensors. In this research, we compared antibody modification by plasma treatment and physical adsorption, using our novel immunosensor based on gold nanoparticles (AuNPs). Consequently, the O2-plasma treatment produced carboxyl groups on the electrode surface that changed the electrochemical properties owing to electrostatic interactions. In this study, we compared the following four cases of SPCE modification: O2-plasma-treated electrode/covalent-bonded antibody (a); O2-plasma-treated electrode/physical adsorbed antibody (b); bare electrode/covalent-bonded antibody (c); and bare electrode/physical absorbed antibody (d). The limits of detection (LOD) were 0.50 ng/mL (a), 9.7 ng/mL (b), 0.54 ng/mL (c), and 1.2 ng/mL (d). The slopes of the linear response range were 0.039, 0.029, 0.014, and 0.022. The LOD of (a) was 2.4 times higher than the conventional condition (d), The slope of (a) showed higher sensitivity than other cases (b~d). This is because the plasma treatment generated many carboxyl groups and increased the number of antibody adsorption sites. In summary, the O2-plasma treatment was found to modify the electrode surface conditions and improve the amount of antibody modifications. In the future, O2-plasma treatment could be used as a simple method for modifying various molecular recognition elements on printed carbon electrodes.

Point-of-Care Diagnostic Biosensors to Monitor Anti-SARS-CoV-2 Neutralizing IgG/sIgA Antibodies and Antioxidant Activity in Saliva.

Monitoring biomarkers is a great way to assess daily physical condition, and using saliva instead of blood samples is more advantageous as the process is simple and allows individuals to test themselves. In the present study, we analyzed the titers of neutralizing antibodies, IgG and secretory IgA (sIgA), in response to the SARS-CoV-2 vaccine, in saliva. A total of 19 saliva and serum samples were collected over a 10-month period 3 weeks after the first vaccine, 8 months after the second vaccine, and 1 month after the third vaccine. The ranges of antibody concentrations post-vaccination were: serum IgG: 81-15,000 U/mL, salivary IgG: 3.4-330 U/mL, and salivary IgA: 58-870 ng/mL. A sharp increase in salivary IgG levels was observed after the second vaccination. sIgA levels also showed an increasing trend. A correlation with trends in serum IgG levels was observed, indicating the possibility of using saliva to routinely assess vaccine efficacy. The electrochemical immunosensor assay developed in this study based on the gold-linked electrochemical immunoassay, and the antioxidant activity measurement based on luminol electrochemiluminescence (ECL), can be performed using portable devices, which would prove useful for individual-based diagnosis using saliva samples.

Novel Glycolipid Chips with a Double Layer of Au Nanoparticles for Biological Toxin Detection.

Glycolipid chips having a double layer of Au nanoparticles are proposed for detection of biological toxins. The sugar-modified chips constitute an under and an upper layer of Au nanoparticles of 20-80 nm diameter on glass plates, and Au nanoparticles of each layer are linked with 1,8-octanedithiol by a self-assembled monolayer (SAM) technique. A tris-sialo glycosphingolipid, ganglioside GT1b, having lipoic amide at the sphingosine part was immobilized on the Au outside surface of the upper layer, and botulinum toxin (type A heavy chain) was detected by localized surface plasmon resonance (LSPR). The GT1b-Cer-coated chip having a double layer of Au nanoparticles enhanced the toxin detection by LSPR more than those with single monolayers. The LSPR response changed according to the sizes of Au nanoparticles in each under and upper layer. The combination of 60 and 40 nm Au nanoparticles in the under and upper layer, respectively, gave the best result, which enabled the toxin detection at concentrations below 5 ng/mL with the portable LSPR device.

A High-Throughput Single-Cell Assay on a Valve-Based Microfluidic Platform Applied to Protein Quantification, Immune Response Monitoring, and Drug Discovery.

The use of microfluidic technology in single-cell assay has shown potential in biomedical applications like protein quantification, immune response monitoring, and drug discovery. Because of the details of information that can be obtained at single-cell resolution, the single-cell assay has been applied to tackle challenging issues such as cancer treatment. Information like the levels of protein expression, cellular heterogeneity, and unique behaviors within subsets are very important in the biomedical field. For a single-cell assay system, a high-throughput platform that can do on-demand media exchange and real-time monitoring is advantageous in single-cell screening and profiling. In this work, a high-throughput valve-based device is presented, its use in single-cell assay, particularly in protein quantification and surface-marker analysis, and its potential application to immune response monitoring and drug discovery are laid down in detail.

Development of Nano-Micro Fused LSPR Chip for In Situ Single-Cell Secretion Analysis.

Single-cell analysis has become increasingly important in uncovering cell heterogeneity, which has great implications in medicine and biology for a deep understanding of cell characteristics. Owing to its significance, it is vital to create novel devices that can reveal special or unique cells. In this work, we developed a single-cell secretion detection chip consisting of microwells that can trap single cells. Each well is surrounded by Au nanopillars capable of localized surface plasmon resonance (LSPR) measurement. Using microfabrication and nanofabrication techniques, Au nanopillar and microwell structures were fabricated on a COP film. The Au nanopillar was modified with IL-6 antibodies for the direct detection of single-cell secreted IL-6 via LSPR absorbance peak shift. Specific IL-6 detection was successfully demonstrated using a null and IL-6 oversecreting Jurkat cell. A high single-cell trapping efficiency of over 80% was also achieved. Overall, the development of this single-cell secretion detection chip with a simple LSPR measurement setup represents a significant development in the field of cell biology and immunology, providing researchers with a powerful tool for studying individual cells and their secreted cytokines, and is useful for point-of-care testing (POCT) diagnostics.

Single-beam optical biosensing based on enzyme-linked laser nanopolymerization of o-phenylenediamine.

We report an innovative biosensing technique using a focused laser beam for the fabrication of a polymer nanostructure and the detection of its nanoscale growth. A nanoaggregate structure is formed by focusing a single beam of a continuous-wave (cw) green laser beam on an o-phenylenediamine (o-pD) solution dropped on a glass substrate. The backreflection intensity of the focused laser beam shows a temporal oscillation, whereas the size of the aggregate monotonously increases. Simple calculations based on the Fresnel equation qualitatively reproduce the experimental results, indicating that the backreflected laser oscillation occurs because of the interference between two beams reflected at the front and the back surfaces of the aggregate. Because the growth speed of the aggregate depends on light absorption by the oxidized o-PD, the backreflection oscillation curve can be used to monitor the oxidative reaction in the solution. We apply this phenomena to optical biosensing based on the oxidation of o-PD by the peroxidase enzyme reaction. A reliable quantification of glucose can be achieved by simply focusing a single laser beam and detecting its reflection intensity in a manner similar to the optical pickup unit of optical storage drives.