Disposable Chip Research Articles

Easy-to-Use Osmosis-Based Microfluidic Chip for Protein Crystallization: Application to a Monoclonal Antibody

We developed a disposable microfluidic chip which mimics the vapor diffusion method for exploring protein crystallization conditions but at the nanoliter scale. This device exploits the permeation of water through a thin poly(dimethylsiloxane) (PDMS) layer separating droplets stored in the chip and containing a mixture of proteins and precipitants from an open microfluidic reservoir. The water chemical activity fixed by the reservoir makes it possible to modify the volume of the droplets in a controlled way (reduction or increase). Because PDMS is only permeable to water, the imposed water activity therefore increases or decreases the concentration of the solutes present in the droplet and consequently the supersaturation of the solution. The specificity of our approach, in addition to the low volumes ensuring controlled mass transport conditions, is that the concentration of all the solutes is known at any time, thus allowing the extraction of quantitative information on the crystallization process. We exploit these chips on a protein of therapeutic interest: the full-length monoclonal antibody anti-CD20. Our experiments allow us in particular to estimate both the solubility of this protein and the width of the metastable zone with Na2SO4 and PEG400 as crystallizing agents. We also show that the fine-tuning of the permeation rate makes it possible to perform crystallization/dissolution cycles to selectively dissolve small crystals and increase the mean size of the remaining anti-CD20 crystals.

Development of a portable MIP-based electrochemical sensor for detection of SARS-CoV-2 antigen

The current COVID-19 pandemic caused by SARS-CoV-2 coronavirus is expanding around the globe. Hence, accurate and cheap portable sensors are crucially important for the clinical diagnosis of COVID-19. Molecularly imprinted polymers (MIPs) as robust synthetic molecular recognition materials with antibody-like ability to bind and discriminate between molecules can perfectly serve in building selective elements in such sensors. Herein, we report for the first time on the development of a MIP-based electrochemical sensor for detection of SARS-CoV-2 nucleoprotein (ncovNP). A key element of the sensor is a disposable sensor chip - thin film electrode - interfaced with a MIP-endowed selectivity for ncovNP and connected with a portable potentiostat. The resulting ncovNP sensor showed a linear response to ncovNP in the lysis buffer up to 111 fM with a detection and quantification limit of 15 fM and 50 fM, respectively. Notably, the sensor was capable of signaling ncovNP presence in nasopharyngeal swab samples of COVID-19 positive patients. The presented strategy unlocks a new route for the development of rapid COVID-19 diagnostic tools.

A Co-Nanoparticles Modified Electrode for On-Site and Rapid Phosphate Detection in Hydroponic Solutions.

Conventional strategies for determining phosphate concentration is limited in efficiency due to the cost, time, and labor that is required in laboratory analysis. Therefore, an on-site and rapid detection sensor for phosphate is urgently needed to characterize phosphate variability in a hydroponic system. Cobalt (Co) is a highly sensitive metal that has shown a selectivity towards phosphate to a certain extent. A disposable phosphate sensor based on the screen-printed electrode (SPE) was developed to exploit the advantages of Co-nanoparticles. A support vector machine regression model was established to predict the concentration of phosphate in the hydroponic solutions. The results showed that Co-nanoparticles improve the detection limit of the sensor in the initial state. Meanwhile, the corrosion of Co-nanoparticles leads to a serious time-drift and instability of the electrodes. On the other hand, the coefficient of variation of the disposable phosphate detection chip is 0.4992%, the sensitivity is 33 mV/decade, and the linear range is 10−1–10−4.56 mol/L. The R2 and mean square error of the buffer-free sensor in the hydroponic solution are 0.9792 and 0.4936, respectively. In summary, the SPE modified by the Co-nanoparticles is a promising low-cost sensor for on-site and rapid measurement of the phosphate concentration in hydroponic solutions.

Arrays of Copper Microelectrodes from Disposable Chips: Fabrication and Characterization

A simple, fast, and low-cost process to fabricate arrays of copper microelectrodes (CuMEs) based on disposable electronic microchips is described. Arrays with 8 to 20 CuMEs were characterized by energy-dispersive X-ray spectroscopy and cyclic voltammetry techniques. The closest interelectrode distance in the arrays is 358 ± 22 μm, and the minor radius ranged from 10.6 to 13.5 μm. The microchips with CuMEs were sealed in epoxy resin to fabricate the rod and flat-shaped platforms, allowing the CuMEs to be addressed separately. Glucose, hydrazine, and nitrate were used as analyte models for voltammetric and amperometric detection at CuMEs arrays, showing excellent performance in batch and flow-through cells. Glucose measurements carried out with flow injection analysis system with amperometric detection at an array of 20 CuMEs showed a wide linear range (0.020-4.0 mmol L-1), high sensitivity (734.1 μA L mmol-1 cm-2), and a limit of detection of 1.7 μmol L-1.

A Disposable Sensor Chip Using a Paste Electrode with Surface-Imprinted Graphite Particles for Rapid and Reagentless Monitoring of Theophylline

A Disposable Sensor Chip Using a Paste Electrode with Surface-Imprinted Graphite Particles for Rapid and Reagentless Monitoring of Theophylline

Point of care whole blood microfluidics for detecting and managing thrombotic and bleeding risks.

Point-of-care diagnostics of platelet and coagulation function present demanding challenges. Current clinical diagnostics often use centrifuged plasmas or platelets and frozen plasma standards, recombinant protein standards, or even venoms. Almost all commercialized tests of blood do not recreate the in vivo hemodynamics where platelets accumulate to high densities and thrombin is generated from a procoagulant surface. Despite numerous drugs that target platelets, insufficient coagulation, or excess coagulation, POC blood testing is essentially limited to viscoelastic methods that provide a clotting time, clot strength, and clot lysis, while used mostly in trauma centers with specialized capabilities. Microfluidics now allows small volumes of whole blood (<1 mL) to be tested under venous or arterial shear rates with multi-color readouts to follow platelet function, thrombin generation, fibrin production, and clot stability. Injection molded chips containing pre-patterned fibrillar collagen and lipidated tissue factor can be stored dry for 6 months at 4C, thus allowing rapid blood testing on single-use disposable chips. Using only a small imaging microscope and micropump, these microfluidic devices can detect platelet inhibitors, direct oral anticoagulants (DOACs) and their reversal agents. POC microfluidics are ideal for neonatal surgical applications that involve small blood samples, rapid DOAC testing in stroke or bleeding or emergency surgery situations with patients presenting high risk cofactors for either bleeding or thrombosis.

Electrical Cartridge Sensor Enables Reliable and Direct Identification of MicroRNAs in Urine of Patients.

Urinary miRNAs are biomarkers that demonstrate considerable promise for the noninvasive diagnosis and prognosis of diseases. However, because of background noise resulting from complex physiological features of urine, instability of miRNAs, and their low concentration, accurate monitoring of miRNAs in urine is challenging. To address these limitations, we developed a urine-based disposable and switchable electrical sensor that enables reliable and direct identification of miRNAs in patient urine. The proposed sensing platform combining disposable sensor chips composed of a reduced graphene oxide nanosheet and peptide nucleic acid facilitates the label-free detection of urinary miRNAs with high specificity and sensitivity. Using real-time detection of miRNAs in patient urine without pretreatment or signal amplification, this sensor allows rapid, direct detection of target miRNAs in a broad dynamic range with a detection limit down to 10 fM in human urine specimens within 20 min and enables simultaneous quantification of multiple miRNAs. As confirmed using a blind comparison with the results of pathological examination of patients with prostate cancer, the sensor offers the potential to improve the accuracy of early diagnosis before a biopsy is taken. This study holds the usefulness of the practical sensor for the clinical diagnosis of urological diseases.

A microfluidic device for blood plasma separation and fluorescence detection of biomarkers using acoustic microstreaming

Human blood plasma contains numerous soluble, diffusible, and secreted biomarkers that are used for clinical diagnosis and prognosis of various diseases. However, the blood of some patients is hemolyzed rapidly due to the rupture of cell membranes and releases chemicals and biological molecules that yield false-positive fluorescence detection results due to autofluorescence. The standard method for plasma separation is centrifugation, which is difficult to be integrated with various methods for downstream biomarker detection. Herein, we report development of a novel microfluidic device that is integrated with multiple functionalities on a single disposable chip. Using the principle of bubble-induced acoustic microstreaming, we have tested whole blood controls spiked with fluorescently tagged antibodies to HIV-1 p24 protein and obtained ∼ 31.8 % plasma yield with 99.9 % plasma purity within five minutes. The separated plasma was then routed to an integrated micro-mixing chamber and mixed with HIV-1 p24 antigen conjugated beads (10 μm diameter). The bound p24 antigen-antibody complexes were captured by acoustic microstreaming and detected using a fluorescence microscope. These experiments demonstrated a detection limit of ∼17 pg/μL of p24 antibody in the plasma. The microfluidic device successfully separated plasma from the whole blood control using acoustic microstreaming and integrated with acoustic micro-pumping and micro-mixing for enrichment of biomarkers by mixing p24-bound beads with fluorescently tagged antibodies. The beads with antigen-antibody complexes were efficiently captured in a separate compartment for fluorescence microscopy and detection of biomarkers. Integration of multiple functionalities on a single disposable microfluidic chip can now facilitate rapid detection of biomarkers and be used for monitoring patients’ specimen in real time.

Saliva Stress Marker Monitor Using Aptamer Immobilized FET Biosensor

Introduction People have felt that their mind controls the body. Advances in immunology and neuroscience are scientifically elucidating this experience. For example, it has been clarified that the mechanism by which changes in the activity of the central nervous system due to stress regulate the immune response through sympathetic nerves. If these latest medical knowledge and electronic advances can be used to provide a simple monitoring system for stress-related substances, it is hoped that it will help prevent mental and physical diseases. Nevertheless, performing a blood draw to detect the stress hormones cortisol and catecholamine has the challenge that the act of drawing blood itself causes stress. Instead, cortisol concentration measurement from saliva has been developed as a non-invasive detection, but catecholamines cannot be detected from saliva. Salivary cortisol concentration measurements have been developed as an alternative non-invasive detection method, but catecholamines are unable to obtain the necessary information from saliva. Salivary α-amylase and chromogranin A (CgA) have also been studied and used in part as alternatives to catecholamines. Secretary immunoglobulin A (s-IgA) in saliva is also a good stress marker that reflects suppression of the immune system by stress. Simultaneous monitoring of the time-dependence of these stress markers of different origins is expected to help elucidate the complex mental stress mechanisms [1]. Sensor module platform Accurate and inexpensive biomaterial detectors are required for IoT biosensing systems and monitoring over time has not been realized until now. Field-effect transistor (FET) biosensors are small devices that detect various types of biomarkers at low power consumption without disturbing the system under test [2]. The biggest challenge of FET biosensors when used in electronics systems is instability due to current drift. We have succeeded in developing a method that minimizes drift using only the normal silicon fab process. This manufacturing process does not use tantalum pentoxide or other special materials. Figure 1 shows a picture of a newly developed four element FET sensor chip with extremely low instability. The electronics part of the developed biosensor module consists of this chip and a Bluetooth Low Energy (BLE)-type communication circuit. We selected four types of aptamers as sensor receptors on the gate insulator on the chip [3]. The aptamers can be stored and used at room temperature for a long period of time. They also have the advantages of being reversible to thermal denaturation and can be produced inexpensively and industrially. Finally, as a technique for producing biosensors with less variation, such as commercial physical sensors, we developed a tool for uniformly immobilizing the receptor monolayer in a narrow range of fixed positions on the chip. Simultaneous detection of multiple stress markers in saliva When n types of receptors are immobilized on n FET elements, n-1 types of independent signals can be extracted. The effects of non-specifically adsorbed substances and pH in saliva, temperature fluctuation, optical noise, and crosstalk between elements can be eliminated from the original signals of multiple FET elements. Using this technique, we succeeded in obtaining multiple stress marker concentrations such as cortisol, a-amylase, s-IgA, and CgA [4], at the same time just by dropping saliva on the sensor. The signal time constant is less than 1 minute, which indicates that a continuous monitor is realized substantially. Operability equivalent to physical sensor Internet of Things (IoT) systems require many low-cost sensors. FET sensor chips manufactured using only the conventional silicon fab process can achieve a low cost of about $1 per chip. However, even with such cheap biosensors, if they are disposable, the cost burden on the user will increase significantly in the long run. As a result, it becomes difficult to secure good customers as fixed users. In addition, disposable chips are not suitable for continuous monitoring required for medically important data. We are developing biosensors that are as easy to operate as conventional physical sensors by introducing reusable cleaning methods and recycled precision cleaning methods.

Development of Interdigitated Capacitive Sensor for Real-Time Monitoring of Sub-Micron and Nanoscale Particulate Matters in Personal Sampling Device for Mining Environment

While current personal monitoring devices for mining industry are optimized for monitoring microscale particles, a higher resolution technique is required to detect sub-micron and nanoscale particulate matters (PM) due to smaller volume and mass of the particles. In this work, an interdigitated capacitive sensor is designed for monitoring sub-micron and nanoscale particle concentration in real-time for mining environment and other applicable environments. The 2 mm $\times12$ mm disposable sensor chip fits generic air sampling cassette housing. The re-usable readout board uses resistance-capacitance (RC) delay time constant for monitoring capacitance shift and data is recorded in real-time. The sensor showed clear response with respect to a commonly used test dust, and positive capacitance shift is observed after test. Among the collected particles, about 77 % are sub-micron and most of microparticles are agglomerates of sub-micron particles. A simulation study showed that our sensor response is in a region that is proportional to the particle volume collected on sensor. A comparison with gravimetric method showed that less than 1/1000 of collected particle mass on the sampler is responsible for sensor response due to radial distribution of particle deposition and sensor location. The sensor response is converted into a standard airborne mass particle concentration (g/ $\text{m}^{3}$ ) to demonstrate a continuous monitoring of particle concentration. An incorporated microheater improved stable capacitive sensor reading under air flow and various humidity.

An IoT-enabled paper sensor platform for real-time analysis of isothermal nucleic acid amplification tests

Paper-based sensors can be exploited to develop low-cost, disposable, and rapid assays for the detection of a large variety of analytes. We report a paper-based sensor system for a point-of-care (POC) nucleic acid amplification test that can quantitatively detect multiple genes from different pathogens. The POC system combines a paper sensor chip and a portable instrument, which is built on an Internet of Things (IoT) platform. The paper-based sensor provides the functions of reagent storage, sample transportation, and nucleic acid amplification. The IoT instrument uses an Arduino microcontroller to control temperature, collect fluorescence images, and store the data in cloud storage via a WiFi network. A compact fluorescence reader was designed to measure fluorescence images of the amplicons during a loop-mediated isothermal amplification reaction in real-time. The real-time detection capability enables the quantitative analysis of target genes. The results show that the paper-based sensor cam distinguish multiple genes of the genomic DNA extracted from Escherichia coli and Campylobacter jejuni, with the concentration as low as 2 × 103 copies/μL. The affordable instrument, in conjunction with the disposable paper sensor chip, would have a great potential for POC detections of pathogens.

An Integrated Smartphone-Based Genetic Analyzer for Qualitative and Quantitative Pathogen Detection.

The use of the smartphone is an ideal platform to realize the future point-of-care (POC) diagnostic system. Herein, we propose an integrated smartphone-based genetic analyzer. It consists of a smartphone and an integrated genetic analysis unit (i-Gene), in which the power of the smartphone was utilized for heating the gene amplification reaction, and the camera function was used for imaging the colorimetric change of the reaction for quantitative and multiplex foodborne pathogens. The housing of i-Gene was fabricated by using a 3D printer, which was equipped with a macro lens, white LEDs, a disposable microfluidic chip for loop-mediated isothermal amplification (LAMP), a thin-film heater, and a power booster. The i-Gene was installed on the iPhone in alignment with a camera. The LAMP mixture for Eriochrome Black T (EBT) colorimetric detection was injected into the LAMP chip to identify Escherichia coli O157:H7, Salmonella typhimurium, and Vibrio parahaemolyticus. The proportional–integral–derivative controller-embedded film heater was powered by a 5.0 V power bank to maintain 63 °C for the LAMP reaction. When the LAMP proceeded, the color was changed from violet to blue, which was real-time monitored by the smartphone complementary metal oxide semiconductor camera. The images were transported to the desktop computer via Wi-Fi. The quantitative LAMP profiles were obtained by plotting the ratio of green/red intensity versus the reaction time. We could identify E. coli O157:H7 with a limit of detection of 101 copies/μL within 60 min. Our proposed smartphone-based genetic analyzer offers a portable, simple, rapid, and cost-effective POC platform for future diagnostic markets.

Label-free immunodetection of α-synuclein by using a microfluidics coplanar electrolyte-gated organic field-effect transistor

The aggregation of α-synuclein is a critical event in the pathogenesis of neurological diseases, such as Parkinson or Alzheimer. Here, we present a label-free sensor based on an Electrolyte-Gated Organic Field-Effect Transistor (EGOFET) integrated with microfluidics that allows for the detection of amounts of α-synuclein in the range from 0.25 pM to 25 nM. The lower limit of detection (LOD) measures the potential of our integrated device as a tool for prognostics and diagnostics. In our device, the gate electrode is the effective sensing element as it is functionalised with anti-(α-synuclein) antibodies using a dual strategy: i) an amino-terminated self-assembled monolayer activated by glutaraldehyde, and ii) the His-tagged recombinant protein G. In both approaches, comparable sensitivity values were achieved, featuring very low LOD values at the sub-pM level. The microfluidics engineering is central to achieve a controlled functionalisation of the gate electrode and avoid contamination or physisorption on the organic semiconductor. The demonstrated sensing architecture, being a disposable stand-alone chip, can be operated as a point-of-care test, but also it might represent a promising label-free tool to explore in-vitro protein aggregation that takes place during the progression of neurodegenerative illnesses.

AutoProteome Chip System for Fully Automated and Integrated Proteomics Sample Preparation and Peptide Fractionation.

With recent advances in LC-MS systems, current MS-based proteomics has an increasing need for automated, high-throughput sample preparation with neglectable sample loss. In this study, we developed a microfluidic system for fully automated proteomics sample preparation. All of the required proteomics sample preparation steps for both protein digestion and peptide fractionation are fully integrated into a disposable plastic chip device (named AutoProteome Chip). The AutoProteome Chip packed with mixed-mode ion exchange beads and C18 membrane in tandem could be fabricated with very low cost and high stability in organic reagents. Benefiting from its low backpressure, the AutoProteome Chip could be precisely driven by gas pressure, which could be easily multiplexed. As low as 2 ng of standard protein BSA could be trapped into the AutoProteome chip and processed within 2 h. Fully automated processing of 10 μg of protein extracts of HEK 293T cells achieved more than 97% of digestion efficiency with missed cleavage less than 2 and comparable performance with conventional approaches. More than 4700 proteins could be readily identified within 80 min of LC-MS analysis with good label-free quantification performance (Pearson correlation coefficient >0.99). Furthermore, deep proteome profiling by integrated high-pH RP fractionation in the same AutoProteome Chip resulted in more than 7500 proteins being identified from only 20 μg of protein extracts of HEK 293T cells and comparable reprodicibility as single-shot analysis. The AutoProteome Chip system provided a valuable prototype for developing a fully automated proteome analysis workflow and for proteomic applications with high demand for processing throughput, reproducibility, and sensitivity.

OPAA/fluoride biosensor chip towards field detection of G-type nerve agents

Sensor technology, particularly disposable, field-deployable devices offer considerable promise for addressing major security demands, in general, and in particular the urgent needs for selective and rapid field detection of highly toxic G-type organophosphate (OP) nerve agents. Herein, we report on the first example of a disposable electrochemical biosensor chip for decentralized field detection of diisopropyl fluorophosphate (DFP), as the simulant compound of G-type nerve agents (e.g., Sarin and Soman), based on the integration of an all-solid-state fluoride potentiometric transducer with the enzyme organophosphorus acid anhydrolase (OPAA) in connection to a hand-held potentiometric analyzer. Such solid-contact fluoride ion-selective electrodes were realized by comparing different fluoride ionophores to select the bis(fluorodioctylstannyl)methane molecule, along with systematic optimization of the experimental parameters. This first solid-contact fluoride detection chip displayed a favorable analytical performance, with near-Nernstian behavior at neutral pH in different buffers, high selectivity against various anions along with excellent reproducibility. Combining such desirable merits of the new fluoride sensor with the selective biocatalytic hydrolysis via an immobilized OPAA, to break the PF bond of G-type neurotoxins and release detectable fluoride ions, thereby enabled an attractive analytical performance. Both the fluoride and the nerve-agent recognition layers have thus been systematically optimized. The resulting biosensor chip thus displays a fast, sensitive and selective response towards DFP (including efficient discrimination against OP pesticides), along with a wide dynamic range of 250–3000 μM. Key challenges towards developing the nerve-agent detection chip were carefully addressed, including the pH incompatibility of the enzymatic and detection processes. By providing effective discrimination against common OP pesticides and minimizing related false alarms, the resultant disposable potentiometric biochip platform is expected to provide an instantaneous reliable warning of chemical attack and exposure towards a timely countermeasure action, and hence, would dramatically advance the protection of our military personnel.

Portable and Battery-Powered PCR Device for DNA Amplification and Fluorescence Detection.

Polymerase chain reaction (PCR) is a technique for nucleic acid amplification, which has been widely used in molecular biology. Owing to the limitations such as large size, high power consumption, and complicated operation, PCR is only used in hospitals or research institutions. To meet the requirements of portable applications, we developed a fast, battery-powered, portable device for PCR amplification and end-point detection. The device consisted of a PCR thermal control system, PCR reaction chip, and fluorescence detection system. The PCR thermal control system was formed by a thermal control chip and external drive circuits. Thin-film heaters and resistance temperature detectors (RTDs) were fabricated on the thermal control chip and were regulated with external drive circuits. The average heating rate was 32 °C/s and the average cooling rate was 7.5 °C/s. The disposable reaction chips were fabricated using a silicon substrate, silicone rubber, and quartz plate. The fluorescence detection system consisted a complementary metal-oxide-semiconductor (CMOS) camera, an LED, and mirror units. The device was driven by a 24 V Li-ion battery. We amplified HPV16E6 genomic DNA using our device and achieved satisfactory results.

Saliva Stress-Marker Monitor Using Aptamer-Immobilized FET Biosensor

Introduction People have felt that their mind controls the body. Advances in immunology and neuroscience are scientifically elucidating this experience. For example, it has been clarified that the mechanism by which changes in the activity of the central nervous system due to stress regulate the immune response through sympathetic nerves. If simple monitoring of stress-related substances is realized by utilizing such medical advances and advances in electronic devices, we can expect to help prevent many diseases. Nevertheless, the medically established technique of collecting blood for the detection of stress hormones, cortisol and catecholamine has the disadvantage of causing stress by the collecting action itself. Instead, cortisol concentration measurement from saliva has been developed as a non-invasive detection, but catecholamines cannot be detected from saliva. Salivary α-amylase and chromogranin A (CgA) have also been studied and used in part as alternatives to catecholamines. Secretary immunoglobulin A (s-IgA) in saliva is also a stress marker that reflects suppression of the immune system by stress. Simultaneous monitoring of time-dependent changes in these stress markers of different origins is expected to be an important technique for mental and physical health [1]. Biosensor module platform Precise but inexpensive biological material detectors are required for IoT biosensing system, and it has not been possible to monitor them over time. A field effect transistor (FET) biosensor is a compact device that detects many types of biomarkers with low power consumption without disturbing the system under test [2]. The biggest challenge of FET biosensors when used in electronics systems is instability due to current drift. We have succeeded in developing a method that minimizes drift using only the normal silicon fab process. This manufacturing process does not use tantalum pentoxide or other special materials.Figure 1 shows a photo of a newly developed four-element FET sensor chip with very low instability. The electronics part of the biosensor module consists of this chip and a Bluetooth Low Energy (BLE) type communication function. We selected aptamers as sensor receptors on the gate insulator film on the chip [3]. Aptamers can be stored and used at room temperature for a long period of time. They also have the advantages of being reversible to thermal denaturation, and can be produced inexpensively and industrially. Finally, as a technology for manufacturing biosensors with as little variation as semiconductor devices, we have developed a tool that uniformly immobilizes receptor monolayers in a narrow place at a fixed position on a chip. Simultaneous detection of stress markers in saliva When n types of receptors are immobilized on n FET elements, n − 1 types of independent signals can be extracted. The effects of non-specifically adsorbed substances and pH in saliva, temperature fluctuation, optical noise, and crosstalk between elements can be eliminated from the original signals of multiple FET elements. Using this technique, we succeeded in obtaining multiple stress marker concentrations such as cortisol, α-amylase, s-IgA, and CgA [4], at the same time just by dropping saliva on the sensor. The signal time constant is less than 1 minute, which indicates that a continuous monitor is realized substantially. Operability equivalent to physical sensor Internet of Things (IoT) systems require a large number of low-cost sensors. An FET sensor chip manufactured using only the normal silicon fab process achieves a low cost of about $ 1 per chip. However, if a biosensor is disposable, the cost burden on the user will increase significantly over the long term. As a result, it becomes difficult to secure good customers as fixed users. In addition, disposable chips are not suitable for continuous monitoring required for medically important data. We are developing an easy-to-reuse cleaning method and a recycling precision cleaning method with the aim of securing customers by realizing biosensor technology with the same operability as conventional physical sensors.

An Aptameric Biolayer Interferometric Assay for Detection of Recombinant Human Erythropoietin-α

The biolayer interferometry (BLI), one promising biosensing technique for real-time, high-sensitive detection of analytes, is a new surface-sensitive spectroscopic technique in which the change of biolayer thickness is reflected by measuring the interferometric phase deflections. In our previous research, an ssDNA aptamer, 39nt, with definite interaction characteristics for recombinant human erythropoietin-α (EPO-α) was screened. In this work, a new aptameric BLI assay of EPO-α based on this aptamer 39nt was established. The biotinylated aptamer 39nt was firstly immobilized onto the optical fiber streptavidin biosensor chip, and the analytes in microliter volume were quickly diffused via high-speed vibration of 2200 r/min. The key parameters such as the orientation of aptamer sequence, the concentration for immobilization, and the overcome of nonspecific adsorption to exhibit the affinity recognition of aptamers were optimized. It was found that the 3'-end biotinylated aptamer 39nt with 50 nmol/L provided the best sensitivity, and the addition of Tween 20 and BSA could efficiently overcome nonspecific adsorption effect. Besides, towards the original designed disposable sensor chip, the affinity between protein EPO-α and ssDNA aptamer 39nt for ca. 10 times was still maintained under optimized regeneration condition, which reflected the operational flexibility of single-channel BLI system. Furthermore, a signal amplification approach of a sandwiched format via wheat germ agglutinin for detection of EPO-α was established, with the linear range of 10–200 nmol/L, and the LOD was 5 nmol/L. This assay was directly applied to the complex matrix such as 50% human plasma with recoveries in the range of 86.7%–104.2% and RSDs less than 15%. The BLI sensing system developed here provided a helpful way for practical applications in label-free protein interaction and detection. A new aptameric biolayer interferometry assay based on single stranded DNA aptamer 39nt was firstly established. Concomitantly with a signal amplification approach of a sandwiched format via wheat germ agglutinin, a sensitive measurement of recombinant human erythropoietin-α in complex matrix such as 50% human plasma were fulfilled.

Disposable DNA Amplification Chips with Integrated Low-Cost Heaters.

Fast point-of-use detection of, for example, early-stage zoonoses, e.g., Q-fever, bovine tuberculosis, or the Covid-19 coronavirus, is beneficial for both humans and animal husbandry as it can save lives and livestock. The latter prevents farmers from going bankrupt after a zoonoses outbreak. This paper describes the development of a fabrication process and the proof-of-principle of a disposable DNA amplification chip with an integrated heater. Based on the analysis of the milling process, metal adhesion studies, and COMSOL MultiPhysics heat transfer simulations, the first batch of chips has been fabricated and successful multiple displacement amplification reactions are performed inside these chips. This research is the first step towards the development of an early-stage zoonoses detection device. Tests with real zoonoses and DNA specific amplification reactions still need to be done.

Design and fabrication of PDMS microfluidics device for rapid and label-free DNA detection

Microfluidics explores the manipulation of fluid in small volume, a multidisciplinary field is imperative for DNA extraction. This study offers a simple yet substantial methodology for the fabrication of microfluidics structure-based polydimethylsiloxane (PDMS) biopolymer on a glass substrate with SU-8 photoresist for label-free detection of pathogenic genomic DNA. Two microfluidics designs for DNA detection were based on AutoCAD software, both contain two inlets and one outlet, with dimensions of 28 mm wide, and 18 mm long, and total surface area of 504 mm2. The designs were patterned in such particular sizes and dimensions to test fluid delivery and enhancement in biochemical processes in DNA extraction, while maintaining economical values as a disposable chip. Both microfluidics devices showed no leakage during fluid delivery, have heights of 97.97 and 103.44 μm, and surface roughness of 0.15 and 0.07 μm, respectively. DNA extraction from pathogenic fungus Ganoderma boninense was run on PDMS microfluidic device and UV–Vis analysis confirmed successful extraction with peaks found at 260–280 nm. Current–voltage (I–V) measurement confirmed the accuracy of microfluidic device for the specific pathogen with both real and synthetic samples of G. boninense illustrating the similar graph values of only 0.000005 A difference at 1.0 V after hybridization.