Simultaneous detection of five indices of hepatitis B based on an integrated automatic microfluidic device

Facile synthesis of MoS2@Cu2O-Pt nanohybrid as enzyme-mimetic label for the detection of the Hepatitis B surface antigen

An ultrasensitive sandwich-type electrochemical immunosensor was proposed for quantitative detection of hepatitis B surface antigen, which is a representative biomarker of the Hepatitis B virus. First, the porous graphene oxide/Au composites with good conductive ability were employed to accelerate the electron transfer on the electrode interface. Furthermore, the amino functionalized molybdenum disulfide @ cuprous oxide hybrid with coral morphology was prepared to combine platinum nanoparticles for achieving signal amplification strategy. The resulting nanocomposites (molybdenum disulfide @ cuprous oxide - platinum) demonstrated uniform coral morphology, which effectively improved the specific surface area available for loading the secondary antibody and the number of catalytically active sites, even also increased the electrical conductivity. Based on these advantages, this composite system yielded a superior electrocatalytic current response toward the reduction of hydrogen peroxide. In addition, porous graphene oxide/Au composites were used to modify the glassy carbon electrode, thereby presenting a large surface area and becoming biocompatible, for improving the loading capacity of the primary antibody. Under optimal conditions, we obtained a linear relationship between current signal and hepatitis B surface antigen concentration in the broad range from 0.5pg/mL to 200ng/mL, with a detection limit of 0.15pg/mL (signal-to-noise ratio of 3). These values are promising towards clinical applications.

Design of dual working electrodes for concentration process in metalloimmunoassay

Electrochemical immunosensing, particularly through a metalloimmunoassay, is a promising approach for development of point-of-care (POC) diagnostics devices. This study investigated the structure of dual working electrodes (W1 and W2), used in a silver nanoparticles-labeled sandwich-type immunoassay and silver concentration process, paying special attention to the position of W1 relative to W2. The new structures of the dual working electrodes were fabricated for efficient silver concentration and evaluated experimentally, which showed that the duration of prereduction before current measurement decreased from 480 s to 300 s by transforming the position of W1 from 1 line to 2 lines or 6 parts. The experimental results were also compared with numerical simulations based on three-dimensional diffusion, and the prereduction step almost followed the three-dimensional diffusion equation. Using numerical simulations, the ideal structures of dual working electrodes were designed based on relationships between the structures and duration of prereduction or the LOD. In the case of 36 lines at an area ratio of W1 to W1 + W2 of 1 to 10, the prereduction duration decreased to 96 s. The dual working electrodes designed in this study promise to shorten the total analysis time and lower the LOD for POC diagnostics.

Heterogeneous immunoassays in microfluidic format using fluorescence detection with integrated amorphous silicon photodiodes

Miniaturization of immunoassays through microfluidic technology has the potential to decrease the time and the quantity of reactants required for analysis, together with the potential of achieving multiplexing and portability. A lab-on-chip system incorporating a thin-film amorphous silicon (a-Si:H) photodiode microfabricated on a glass substrate with a thin-film amorphous silicon-carbon alloy directly deposited above the photodiode and acting as a fluorescence filter is integrated with a polydimethylsiloxane-based microfluidic network for the direct detection of antibody-antigen molecular recognition reactions using fluorescence. The model immunoassay used consists of primary antibody adsorption to the microchannel walls followed by its recognition by a secondary antibody labeled with a fluorescent quantum-dot tag. The conditions for the flow-through analysis in the microfluidic format were defined and the total assay time was 30 min. Specific molecular recognition was quantitatively detected. The measurements made with the a-Si:H photodiode are consistent with that obtained with a fluorescence microscope and both show a linear dependence on the antibody concentration in the nanomolar-micromolar range.

Internally calibrated quantification of VEGF in human plasma by fluorescence immunoassays in disposable elastomeric microfluidic devices

Herein we report on a proof of principle for the reproducible quantification of Vascular Endothelial Growth Factor (VEGF) in human plasma by fluorescence sandwich immunoassays using disposable polydimethylsiloxane (PDMS) microfluidic chips. The system requires 100 times less sample than typical clinical blood tests, while its current quantification limit is established at 4pM. The in-built calibration method of spiking the plasma with known concentrations of commercially available antigen avoids common sources of error and improves the reliability of the test results. The demonstrated technique is important for immunoassay applications in fundamental scientific research and "point-of-care" (POC) biomedical diagnostics. In particular, the system is immediately applicable to microfluidic quantification of VEGF in human plasma in cancer studies.

Micro- and nanotechnology for viral detection

Since the identification of viruses at the start of the 20th century, detecting their presence has presented great challenges. In the past two decades, there has been significant progress in viral detection methods for clinical diagnosis and environmental monitoring. The earliest advances were in molecular biology and imaging techniques. Advances in microfabrication and nanotechnology have now begun to play an important role in viral detection, and improving the detection limit, operational simplicity, and cost-effectiveness of viral diagnostics. Here we provide an overview of recent advances, focusing especially on advances in simple, device-based approaches for viral detection.

Internally calibrated quantification of protein analytes in human serum by fluorescence immunoassays in disposable elastomeric microfluidic devices

Herein we report on reliable reproducible quantification of protein analytes in human serum by fluorescence sandwich immunoassays in disposable PDMS microfluidic chips. The system requires 1,000 times less sample than typical clinical blood tests and is specifically shown to measure ferritin down to 250 pM in human serum. The in-built calibration method of spiking the serum with known concentrations of commercially available antigen avoids common sources of error and improves the reliability of the test results. The reported microfluidic system is an important new tool for fundamental scientific research, offering sensitive immunoassay measurements in small but complex biosamples. The system is also a further step towards comprehensive affordable "point-of-care" biomedical diagnostics.