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Abstract Micro-opto-electro-mechanical systems (MOEMS) biosensors are employed in various applications such as disease monitoring, drug investigation, detection of pollutants, and biological fluid studies. In this paper, a novel MOEMS biosensor based on a differential folded-flexure structure is introduced. The designed device is employed to detect prostate-specific antigen (PSA) protein and Hepatitis DNA. The target molecules cause a mechanical deflection in the folded-flexure; subsequently, the transmitted optical power across the finger, attached to the flexure, is modulated in proportion to the input concentration. Then, a photodiode power sensor measures the modulated optical power, where the output of the sensor is simply a current related to the target molecules’ concentrations. The employed readout circuit operates at a wavelength of λ = 1550 nm with a laser power of 1 µW. The dimensions of the proposed biosensor are considered to be 365 × 340 × 2 μm³, making this sensor small enough and suitable for integration. The designed biosensor provides notable features of mechanical deflection sensitivities of 0.2053 nm/(ng/ml) and 7.2486 nm/nM, optical transmittance sensitivities of 0.535504 × 10−3 1/(ng/ml) and 18.91 × 10−3 1/nM, total output sensitivities of 0.5398 (mA/W)/(ng/ml) and 19.059 (mA/W)/nM, and measurement ranges of 0-1000 ng/ml and 0-28.33 nM for PSA and Hepatitis DNA, respectively. The proposed system is a sensitive and powerful sensor that can play an important role in diagnosing many diseases.

Accurate monitoring tools are necessary for lactate, a critical biomarker linked to anaerobic metabolism and muscular performance. Lactate dehydrogenase (LDH) immobilized on MXene (Ti3C2Tx)-supported CuO nanocomposites (MCNs) modified glassy carbon electrode (LDH/MCN/GCE) is the innovative electrochemical biosensor for lactate detection presented in this work. CuO nanostructure integration onto MXene nanosheets, MCN production, and LDH immobilization were all successfully accomplished, according to structural characterization performed using XRD, SEM, XPS, and FTIR. The best lactate oxidation current was shown by LDH/MCN/GCE, according to electrochemical study. With a low detection limit of 0.25 µM and a high sensitivity of 5.92107 µA/mM, the biosensor exhibited a linear response range of 0.1–121 mM. The remarkable selectivity, stability, and sensitivity were attributed to enhanced LDH immobilization made possible by MCNs and MXene. The promise of LDH/MCN/GCE for bioanalytical applications is highlighted by promising results from practical testing in human blood samples, opening the door for improvements in lactate monitoring and performance optimization techniques.

Genetically encoded circuits have been successfully utilized to assess and characterize target variants with desirable traits from large mutant libraries. Adenosylcobalamin is an essential coenzyme that is required in many intracellular physiological reactions and is widely used in the pharmaceutical and food industries. High-throughput screening techniques capable of detecting adenosylcobalamin productivity and selecting superior adenosylcobalamin biosynthesis strains are critical for the creation of an effective microbial cell factory for the production of adenosylcobalamin at an industrial level. In this study, we developed an RNA-protein hybrid biosensor whose input part was an endogenous RNA riboswitch to specifically respond to adenosylcobalamin, the inverter part was an orthogonal transcriptional repressor to obtain signal inversion, and the output part was a fluorescent protein to be easily detected. The hybrid biosensor could specifically and positively correlate adenosylcobalamin concentrations to green fluorescent protein expression levels in vivo. This study also improved the operating concentration and dynamic range of the hybrid biosensor by systematic optimization. An individual cell harboring the hybrid biosensor presented over 20-fold higher fluorescence intensity than the negative control. Then, using such a biosensor combined with fluorescence-activated cell sorting, we established a high-throughput screening platform for screening adenosylcobalamin overproducers. This study demonstrates that this platform has significant potential to quickly isolate high-productive strains to meet industrial demand and that the framework is acceptable for various metabolites.

Abstract Catalytic hairpin assembly (CHA)-DNA walker allows nanostructures to spontaneously hybridize to the nucleic acids. The localized surface plasmon resonance provides the ability of color-shift for Au nanoparticles (AuNPs) to design a colorimetric biosensor by implementing CHA-DNA walker reaction on AuNPs. A target gene in Klebsiella pneumoniae as the reaction cascade trigger, was selected. H1 and H2 oligonucleotides as the components of the system were designed and verified by NUPACK. The AuNPs were conjugated to H1. The conjugation of the probes to the AuNPs was evaluated using FT-IR. The signal amplification process was conducted at 25℃. TEM imaging, zeta potential, spectroscopy, and gel-electrophoresis were used to examine the conduction of the reaction cascade and specificity. The sensitivity of the method was analyzed using serial dilution of the target. The formation of over-52 bp intermediate secondary structures (which only exist when the reaction happens) was confirmed by gel-electrophoresis. The color distinction between positive (0.08 to 0.058) and negative samples (0.098 to 0.05) was evidenced instantly and in a period of 90 min of the reaction as a drop change of 520 nm intensity absorbance. TEM imaging confirmed the further distance of AuNPs in the positive sample in comparison to that of the negative sample which reveals effective detection of the pathogen. The LOD of the technique was measured as 2.5 nM of the target sequence. The diagnostic approach is a label-free, enzyme-independent approach and can be executed in a single step. It has been designed by employing the CHA-DNA walker system along with the colorimetric properties of AuNPs for the first time, thereby paving the way for more rapid and accurate diagnostic kits.

Abstract In the quest for early cancer diagnosis, early identification and treatment are paramount. Recently, ctDNA detection has emerged as a viable avenue for early screening of cancer. The examination of ctDNA in fluid biopsies has gained substantial attention in tumor diagnosis and therapy. Both the scientific community and industry are actively exploring this field. However, developing cost-effective, portable, and real-time ctDNA measurement methods using conventional gene detection equipment poses a significant challenge. This challenge has led to the exploration of alternative approaches. Electrochemical biosensors, distinguished by their heightened sensitivity, remarkable specificity, affordability, and excellent portability, have emerged as a promising avenue for ctDNA detection. This review is dedicated to the specific focus on ctDNA detection, highlighting recent advancements in this evolving detection technology. We aimed to reference previous studies related to ctDNA-targeted cancer detection using electrochemical biosensors to advocate the utilization of electrochemical biosensors in healthcare diagnostics. Further research is imperative for the effective integration of ctDNA analysis into point-of-care cancer testing. Innovative approaches utilizing multiple markers need to be explored to advance this technology and make substantial contributions to societal well-being.

A novel lactate biosensor based on a yttrium oxide/boron nitride (Y2O3/BN) nanocomposite modified electrode was developed. The BN nanosheets provided a supporting matrix for the Y2O3 nanoparticles, combining their synergistic properties for electrochemical biosensing. The Y2O3/BN nanocomposite provided high surface area and excellent electrocatalytic effects, promoting the oxidation of hydrogen peroxide generated from lactate oxidase catalyzed lactate oxidation. The Y2O3/BN modified biosensor showed wide linear range from 0.005 to 500 μM, low detection limit of 2 nM, high sensitivity of 1.23 μA/μM, good reproducibility with 3.2 % RSD, and long-term stability over 56 days. The biosensor could detect lactate levels in athlete sweat samples with high accuracy and correlation to standard methods, distinguishing changes in sweat lactate corresponding to different exercise intensities. The nanocomposite modified biosensor showed potential for non-invasive, real-time monitoring of exercise levels and fatigue status based on sweat lactate detection in athletic training applications.