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Due to the clinical similarities between pulmonary embolism (PE) and myocardial infarction (MI), physicians often encounter challenges in promptly distinguishing between them, potentially missing the critical window for the correct emergency response. This paper presents a biosensor, termed the PEMI biosensor, which is designed for the identification and quantitative detection of pulmonary embolism or myocardial infarction. The surface of the working electrode of the PEMI biosensor was modified with graphene oxide and silk fibroin to immobilize the mixture of antibodies. Linear sweep voltammetry was employed to measure the current-to-potential mapping of analytes, with the calculated curvature serving as a judgment index. Experimental results showed that the curvature exhibited a linear correlation with the concentration of antigen FVIII, and a linear inverse correlation with the concentration of antigen cTnI. Given that FVIII and cTnI coexist in humans, the upper and lower limits were determined from the curvatures of a set of normal concentrations of FVIII and cTnI. An analyte with a curvature exceeding the upper limit can be identified as pulmonary embolism, while a curvature falling below the lower limit indicates myocardial infarction. Additionally, the further the curvature deviates from the upper or lower limits, the more severe the condition. The PEMI biosensor can serve as an effective detection platform for physicians.

This study presents and compares two methods for identifying the types of extracellular vesicles (EVs) from different cell lines. Through SDS-PAGE analysis, we discovered that the ratio of CD63 to CD81 in different EVs is consistent and distinct, making it a reliable characteristic for recognizing EVs secreted by cancer cells. However, the electrophoresis and imaging processes may introduce errors in the concentration values, especially at lower concentrations, rendering this method potentially less effective. An alternative approach involves the use of quartz crystal microbalance (QCM) and electroanalytical interdigitated electrode (IDT) biosensors for EV type identification and quantification. The QCM frequency shift caused by EVs is directly proportional to their concentration, while electroanalysis relies on measuring the curvature of the I-V curve as a distinguishing feature, which is also proportional to EV concentration. Linear regression lines for the QCM frequency shift and the electroanalysis curvature of various EV types are plotted separately, enabling the estimation of the corresponding concentration for an unknown EV type on the graphs. By intersecting the results from both biosensors, the unknown EV type can be identified. The biosensor analysis method proves to be an effective means of analyzing both the type and concentration of EVs from different cell lines.

Uric acid is the primary end product of human purine metabolism and has been regarded as a key parameter in urine and blood for monitoring physiological conditions. This paper presents a paper-based biosensor for a quantitative determination of uric acid using electrochemical detection. The working electrode of the biosensor is modified with graphene oxide (GO) and 5-amino-1,3,4-thiadiazole-2-thiol (ATT) by electropolymerizing ATT on the surface of graphene oxide. In this study, cyclic voltammetry (CV) measurements required only 200 μL of analyte solution. The experimental results showed that the oxidation peak current increased as the concentration of uric acid become higher and exhibited a linear relationship in the concentration range of 0.1-10 mM, indicating that this proposed biosensor has high sensitivity. In addition, this biosensor has good selectivity to detect uric acid because ATT has a specific binding with it. In human blood and body fluids, nitrites may be the only factor that can interfere with the detection of uric acid using this proposed biosensor. Nevertheless, uric acid can be discriminated from nitrite in the CV measurement due to different oxidation potentials. Thus, this proposed paper-based biosensor is a promising tool for detecting uric acid in biological samples., Competing Interests: Declaration of Conflicting Interests The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (Copyright © 2021. Published by Elsevier Inc.)

This paper presents a droplet-based immunoassay chip allowing each droplet to be positioned in a passive droplet-positioning cavern under continuous flow. In addition, the chip surface can immobilize any kind of histidine-tagged capture agents for performing simultaneous multiplex immunoassays. Distinct families of monodispersed droplets were generated since a diaphragm, which is a thin elastomeric flap film suspended from the top of the main channel, forms a double T junction for shearing the aqueous liquids by the carrier flow. These two types of monodispersed droplets traverse the main channel to the downstream detection area and enter the passive positioning caverns for further immunoassay. A layer of Ni-Co film was coated on the substrate by electrodeposition in order to immobilize the multiplex histidine-tagged capture molecules. In this study, the tumor suppressor protein p53 and the extracellular signal-related kinase 1 (ERK1) were used as the capture agents. Then, both histidine-tagged proteins p53 and ERK1 were immobilized by the Ni-Co layer in a microarray format for subsequent immunoassay and fluorescence detection. The experimental results show that the detected fluorescence intensity is proportioned to the concentration of the encapsulated content in a small droplet. This proposed droplet-based immunoassay chip can immobilize multiplex histidine-tagged proteins, irrelevant to the species of proteins, to carry out simultaneous immunoassays and allow the operation sequence to be conducted automatically through the manipulation of droplets.

Blood typing assay is a critical test to ensure the serological compatibility of a donor and an intended recipient prior to a blood transfusion. This paper presents a microfluidic blood typing system using a small quantity of blood sample to determine the degree of agglutination of red blood cell (RBC). Two measuring methods were proposed: impedimetric measurement and electroanalytical measurement. The charge transfer resistance in the impedimetric measurement and the power parameter in the electroanalytical measurement were used for the analysis of agglutination level. From the experimental results, both measuring methods provide quantitative results, and the parameters are linearly and monotonically related to the degree of RBC agglutination. However, the electroanalytical measurement is more reliable than the impedimetric technique because the impedimetric measurement may suffer from many influencing factors, such as chip conditions. Five levels from non-agglutination (level 0) to strong agglutination (level 4+) can be discriminated in this study, conforming to the clinical requirement to prevent any risks in transfusion., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This paper presents a multi-well membrane fabricated using polydimethylsiloxane (PDMS) as a part of a microarray biochip that allows dividable incubation chambers to be provided on a single chip. The conditions of the forming temperature, time, and mixing proportion of the materials were investigated to obtain optimal physical absorption with the surface of the chip substrate. To verify the properties of the multi-well chip, immunoassays were performed by the alpha-1-fetoprotein (AFP) antigen sandwich experiment. The results showed that the detection limit reached to the concentration of 10 ng/ml AFP antigen, and that the dynamic range was 30-3000 ng/ml. Attaining excellent physical absorption helps in avoiding cross-contamination or interference between different samples on the same biochip. The merits of dividable multi-well chips include promoting effective use of surface and multiple-sample experiments.