Biosensor Array Research Articles

Decoding wheat contamination through self-assembled whole-cell biosensor combined with linear and non-linear machine learning algorithms

The contamination of mycotoxins is a serious problem around the world. It has detrimental effects on human beings and leads to tremendous economic loss. It is essential to develop a rapid and non-destructive method for contamination recognition particularly for early alarm. In this study, the whole-cell biosensor array was constructed and employed for rapid recognition of wheat contamination by combining with machine learning algorithms. Seven key VOCs were explored through univariate coupling to multivariate analysis of orthogonal partial least squares-discrimination analysis (OPLS-DA) models. The promoters of dnaK, katG, oxyR, soxS obtained from the stress-responsive of key VOCs were fused to the bacterial operon and fabricated on the whole-cell biosensor. The constructed whole-cell biosensor array was consisted with four kinds of sensors and 18 sensor unit. The bioluminescent intensity combined with linear machine learning algorithm of partial least squares discriminant analysis (PLS-DA) and non-linear algorithms of back propagating artificial neural network (BP-ANN) and least square support vector machine (LS-SVM) were employed to establish discrimination models for mold contamination especially for early warning. The Monte-Carlo strategy was performed to generate thirty subsets for modeling to give more reliable results. As a result, the whole-cell biosensor combined with non-linear algorithm of LS-SVM was practicable for detecting mold identification for wheat early-warning with the accuracy of 97.24%. Additionally, this study provides practical and effective methods not only for wheat quality guarantee and supervision but also for other foodstuffs.

Ultrasensitive optical biosensing detection and multiple therapy based on an NIR-II thermoelectric nanoheterojunction

An one-to-all optical diagnostic and therapeutic agent, referring to a single nanocatalyst synchronously displaying multiple optical biosensor and therapeutic modes, is still a remarkable promise because of its outstanding capability in tumor. However, nanocatalyst activity is significantly weakened by the limited light absorption property and catalytic efficiency. Here, a unique pyroelectric nanocatalyst, In2S3-CuInS2@red blood cell membrane (In2S3-CIS@RM), with excellent pyroelectric/photothermal conversion capability for boosted peroxidase-mimicking catalytic activity, is rationally developed. The In2S3-CIS@RM displays catalytic capacity by reacting Cu+ with H2O2 to produce highly toxic ·OH, promoted by 808 nm near-infrared (NIR) light-mediated photothermal/pyroelectric therapy. By synergizing this three-modal effect, cancer suppression is realized with an obvious cancer inhibition rate after the introduction of In2S3-CIS@RM into the HepG2 cells and following 808 nm laser irradiation. Meanwhile, an optical biosensor array is constructed through In2S3-CIS@RM-triggered chromogenic reaction for a fast and accurate analysis of five antioxidants. Interestingly, this biosensor array is verified to be effective for accurate monitoring of invasive cancer in early cancer occurrence, benefiting from the superior catalytic activity of In2S3-CIS@RM and abnormal levels of antioxidants in cancer cells. Thus, this study provides an avenue for developing an NIR laser-activatable one-to-all optical diagnostic and therapeutic nanosystem.

A Portable Electrochemical Biosensor Based on an Amino-Modified Ionic Metal-Organic Framework for the One-Site Detection of Multiple Organophosphorus Pesticides.

Constructing stable, portable sensors and revealing their mechanisms is challenging. Ion metal-organic frameworks (IMOFs) are poised to serve as highly effective electrochemical sensors for detecting organophosphorus pesticides (OPs), leveraging their unique charge properties. In this work, an amino-modified IMOF was constructed and combined with near-field communication (NFC) technology to develop a portable, touchless, and battery-free electrochemical biosensor NH2-IMOF@CS@AChE. -NH2 in NH2-IMOF gives the framework a higher electropositivity compared to IMOF, enhancing the electrostatic attraction with acetylcholinesterase (AChE), which is beneficial for immobilizing AChE. Furthermore, the uncoordinated O atoms and the (CH3)2NH2+ groups in NH2-IMOF help to form stronger bonds with AChE through hydrogen bonds. The results showed a wide linear response range of 1 × 10-15 to 1 × 10-9 M and a low detection limit of 1.24 × 10-13 M for glyphosate (Gly) in the practical detection of OPs. Additionally, electrochemical biosensor arrays were constructed to effectively identify and distinguish multiple OPs on the basis of their unique differential pulse voltammetry (DPV) electrochemical signals. This work provides a simple and effective solution for on-site OP analysis and can be widely applied in food safety and water quality monitoring.

Wearable and Multiplexed Biosensors based on Oxide Field-Effect Transistors.

Wearable sensors designed for continuous, non-invasive monitoring of physicochemical signals are important for portable healthcare. Oxide field-effect transistor (FET)-type biosensors provide high sensitivity and scalability. However, they face challenges in mechanical flexibility, multiplexed sensing of different modules, and the absence of integrated on-site signal processing and wireless transmission functionalities for wearable sensing. In this work, a fully integrated wearable oxide FET-based biosensor array is developed to facilitate the multiplexed and simultaneous measurement of ion concentrations (H+, Na+, K+) and temperature. The FET-sensor array is achieved by utilizing a solution-processed ultrathin (≈6nm thick) In2O3 active channel layer, exhibiting high compatibility with standard semiconductor technology, good mechanical flexibility, high uniformity, and low operational voltage of 0.005V. This work provides an effective method to enable oxide FET-based biosensors for the fusion of multiplexed physicochemical information and wearable health monitoring applications.

Piercing the Shadows: Exploring the Influence of Signal Preprocessing on Interpreting Ultrasensitive Bioelectronic Sensor Data.

The development of ultrasensitive electronic sensors for in vitro diagnostics is essential for the reliable monitoring of asymptomatic individuals before illness proliferation or progression. These platforms are increasingly valued for their potential to enable timely diagnosis and swift prognosis of infectious or progressive diseases. Typically, the responses from these analytical tools are recorded as digital signals, with electronic data offering simpler processing compared to spectral and optical data. However, preprocessing electronic data from potentiometric biosensor arrays is still in its infancy compared to more established optical technologies. This study utilized the Single-Molecule with a Large Transistor (SiMoT) array, which has achieved a Technology Readiness Level of 5, to explore the impact of data preprocessing on electronic biosensor outcomes. A dataset consisting of plasma and cyst fluid samples from 37 patients with pancreatic precursor cyst lesions was analyzed. The findings revealed that standard signal preprocessing can produce misleading conclusions due to artifacts introduced by mathematical transformations. The study offers strategies to mitigate these effects, ensuring that data interpretation remains accurate and reflective of the underlying biochemical information in the samples.

Fully integrated microneedle biosensor array for wearable multiplexed fitness biomarkers monitoring

Fitness monitoring has become increasingly important in modern lifestyles; the current fitness monitoring always relies on physical sensors, making it challenging to detect pertinent issues at a deeper level when exercising. Here, we report a fully integrated wearable microneedle sensor that simultaneously measures fitness related biomarkers (e.g., glucose, lactate, and alcohol) during physical exercise. Such a sensor integrates a biocompatible 3D-printed microneedle array that can comfortably access skin interstitial fluid and a small circuit for signal processing and calibration, and wireless communication. The microneedle array features good biocompatibility and highly sensitive biochemical sensors that can detect even the slightest variations within the biomarkers of this fluid. On-body experimental results indicate that such a sensor can monitor fitness-related biomarkers across multiple subjects and support multi-day monitoring, with results showing a good correlation with commercial devices. The data was transmitted to a smartphone via Bluetooth and uploaded to cloud platforms for further health assessment. This study has the potential to boost intelligent wearable devices in sports health.

Antibody-Based Array for Tacrolimus Immunosuppressant Monitoring with Planar Plastic Waveguides Activated with an Aminodextran-Lipase Conjugate.

Cyclic olefin copolymers (COC; e.g., Zeonor, Topas, Arton, etc.) are materials with outstanding properties for developing point-of-care systems; however, the lack of functional groups in their native form makes their application challenging. This work evaluates different strategies to functionalize commercially available Zeonor substrates, including oxygen plasma treatment, photochemical grafting, and direct surface amination using an amino dextran-lipase conjugate (ADLC). The modified surfaces were characterized by contact angle measurements, Fourier transform infrared-attenuated total reflection analysis, and fluorescence assays based on evanescent wave excitation. The bioaffinity activation through the ADLC approach results in a fast, simple, and reproducible approach that can be used further to conjugate carboxylated small molecules (e.g., haptens). The usefulness of this approach has been demonstrated by the development of a heterogeneous fluorescence immunoassay to detect tacrolimus (FK506) immunosuppressant drug using an array biosensor platform based on evanescence wave laser excitation and Zeonor-ADLC substrates. Surface modification with ADLC-bearing FK506 provides a 3D layer that efficiently leads to a remarkably low limit of detection (0.02 ng/mL) and IC50 (0.9 ng/mL) together with a wide dynamic range (0.07-11.3 ng/mL).

Self-powered wearable biosensor based on stencil-printed carbon nanotube electrodes for ethanol detection in sweat

Herein we introduce a novel water-based graphite ink modified with multiwalled carbon nanotubes, designed for the development of the first wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis. The stencil-printed graphite (SPG) electrodes, printed onto a flexible substrate, were modified by casting multiwalled carbon nanotubes (MWCNTs), electrodepositing polymethylene blue (pMB) at the anode to serve as a catalyst for nicotinamide adenine dinucleotide (NADH) oxidation, and hemin at the cathode as a selective catalyst for H2O2 reduction. Notably, alcohol dehydrogenase (ADH) was additionally physisorbed onto the anodic electrode, and alcohol oxidase (AOx) onto the cathodic electrode. The self-powered biosensor was assembled using the ADH/pMB-MWCNTs/SPG||AOx/Hemin-MWCNTs/SPG configuration, enabling the detection of ethanol as an analytical target, both at the anodic and cathodic electrodes. Its performance was assessed by measuring polarization curves with gradually increasing ethanol concentrations ranging from 0 to 50 mM. The biosensor demonstrated a linear detection range from 0.01 to 0.3 mM, with a detection limit (LOD) of 3 ± 1 µM and a sensitivity of 64 ± 2 μW mM−1, with a correlation coefficient of 0.98 (RSD 8.1%, n = 10 electrode pairs). It exhibited robust operational stability (over 2800 s with continuous ethanol turnover) and excellent storage stability (approximately 93% of initial signal retained after 90 days). Finally, the biosensor array was integrated into a wristband and successfully evaluated for continuous alcohol abuse monitoring. This proposed system displays promising attributes for use as a flexible and wearable biosensor employing biocompatible water-based inks, offering potential applications in forensic contexts.Graphical A novel water-based graphite ink modified with multiwalled carbon nanotubes designed for the development of a wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis.

Development of Metal-Oxide-Metal Micro-Well Array Biosensors for Highly Sensitive Detection of Covid-19

Biosensors play a crucial role in various fields, including medical diagnostics, environmental monitoring, and food safety. Enhancing the sensitivity of biosensors is essential for improving their performance and reliability. One effective approach to achieve this goal is by reducing the distance of electrodes, a parameter that significantly influences the sensor's response. Employing vertical structures to reduce electrode gaps offers several advantages. the heightened controllability of vertical structures facilitates easy adjustments to element size and shape, catering to specific application requirements and maximizing sensor performance. The choice of vertical structures presents a more accessible, flexible, and cost-effective solution from a manufacturing standpoint, particularly for large-scale sensor production.On the other hands, DNA testing plays a pivotal role in the context of COVID-19, demonstrating its profound significance in the identification, monitoring, and management of the virus. Through the analysis of genetic material, particularly RNA in the case of COVID-19, DNA testing enables accurate and timely diagnosis of infections. This precision is instrumental in differentiating the virus from other respiratory illnesses, facilitating early intervention and containment measures. Moreover, the genetic insights garnered from DNA testing contribute to a better understanding of the virus's behavior, mutations, and potential therapeutic targets, thereby informing public health strategies and vaccine development. The integration of DNA testing in the comprehensive approach to combating COVID-19 underscores its indispensable role in mitigating the impact of the pandemic on global health.In this study, we present the development of a novel biosensor based microwell array structure. The fabrication process employed a layer-by-layer method. To be brief, a 4-inch silicon wafer with a 300 nm thick thermal SiO2 was cleaned in acetone, isopropanol, and water. Subsequently, the bottom electrode was deposited by E-gun evaporator followed by a lift-off process. An extremely thin 45nm aluminum oxide layer was deposited by Atomic Layer Deposition (ALD). Then, a 100nm gold layer was deposited as the top electrode by E-gun. Finally, conclude the fabrication by defining the sensing area of the microwell array through Lithography and several etching steps.For the DNA immobilization process, the Covid-probe ssDNA was incubated with the biosensor at 4℃ within the PDMS wells overnight, followed by rinsed 3 times. And 1 uM Covid-target ssDNA was incubated after immobilization of probe DNA. The condition for the reaction of target and probe was 1 hour at room temperature, followed by rinsed 3 times in DI water.The detection was achieved using a combination of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), collectively offering a comprehensive approach for accurate and reliable measurements. The electrolyte consists of 1 mM KCl solution as supporting electrolytes and 5 mM ferricyanide/ferrocyanide as redox pair. The Rct charge transfer resistance of bare device is around 1320 Ohm due to the small sensing area of around 500 * 500 um2. After incubation with the probe DNA, the Rct is around 2150 Ohm indicating that the probe DNA binds to the Au surface successfully. Target DNA was quantitatively measured over a wide concentration range, spanning from 10 pM to 10 nM. The Rct variance from 2260 to 4970 Ohm.Our results demonstrate the biosensor's exceptional performance in terms of sensitivity and dynamic range, showcasing its potential application in the early and accurate diagnosis of Covid-19. The micro-well array biosensor, with its unique design and integrated electrochemical measurement strategy, holds promise for future advancements in point-of-care diagnostics and environmental monitoring. Figure 1

Smell cancer by machine learning-assisted peptide/MXene bioelectronic array

Non-invasive detection of tumors is of utmost importance to save lives. Nonetheless, identifying tumors through gas analysis is a challenging task. In this work, biosensors with remarkable gas-sensing characteristics were developed using a self-assembly method consisting of peptides and MXene. Based on these biosensors, a mimetic biosensor array (MBA) was fabricated and integrated into a real-time testing platform (RTP). In addition, machine learning (ML) algorithms were introduced to improve the RTP's detection and identification capabilities of exhaled gas signals. The synthesized biosensor, with the ability to specifically bind to targeted gas molecules, demonstrated higher performance than the pristine MXene, with a response up to 150% greater. Besides, the MBA successfully detected 15 odor molecules affiliated with five categories of alcohols, ketones, aldehydes, esters, and acids by pattern recognition algorithms. Furthermore, with the ML assistance, the RTP detected the breath odor samples from volunteers of four categories, including healthy populations, patients of lung cancer, upper digestive tract cancer, and lower digestive tract cancer, with accuracies of 100%, 94.1%, 90%, and 95.2%, respectively. In summary, we have developed a cost-effective and precise model for non-invasive tumor diagnosis. Furthermore, this prototype also offers a versatile solution for diagnosing other diseases like nephropathy, diabetes, etc.

Integrated biosensor array for multiplex biomarkers cancer diagnosis via in-situ self-assembly carbon nanotubes with an ordered inverse-opal structure

To enhance the precision and reliability of early disease detection, especially in malignancies, an exhaustive investigation of multi-target biomarkers is essential. In this study, an advanced integrated electrochemical biosensor array that demonstrates exceptional performance was constructed. This biosensor was developed through a controllable porous-size mechanism and in-situ modification of carbon nanotubes (CNTs) to quantify multiplex biomarkers—specifically, C-reaction protein (CRP), carbohydrate antigen 125 (CA125), and carcinoembryonic antigen (CEA)—in human serum plasma. The fabrication process involved creating a highly ordered three-dimensional inverse-opal structure with the CNTs (pCNTs) modifier through microdroplet-based microfluidics, confined spatial self-assembly of nanoparticles, and chemical wet-etching. This innovative approach allowed for direct in-situ modification of nanomaterial onto the surface of electrode array, eliminating secondary transfer and providing exceptional control over structure and stability. The outstanding electrochemical performance was achieved through the synergistic effect of the pCNTs nanomaterial, aptamer, and horseradish peroxidase-labeled (HRP-) antibody. Additionally, the integrated biosensor array platform comprised multiple individually addressable electrode units (n = 11), enabling simultaneous multi-parallel/target testing, thereby ensuring accuracy and high throughput. Crucially, this integrated biosensor array accurately quantified multiplex biomarkers in human serum, yielding results comparable to commercial methods. This integrated technology holds promise for point-of-care testing (POCT) in early disease diagnosis and biological analysis.

Tongue depressor (bio)sensors: A fast decentralized self-testing of salivary biomarkers for personalized medicine

The clinical tests usually make use of blood samples, requiring invasive sample collection protocols, which are not appropriate for decentralized, frequent, and point-of-care (POC) applications. Here, we report disposable (bio)sensors combining electrochemical and colorimetric technologies on an accessible and lightweight wooden tongue depressor platform. The array of (bio)sensors on this commonly used medical tool enables rapid, and safe saliva sampling and showed promise to be used for frequent self-testing of four clinically relevant biomarkers (glucose, uric acid, nitrite, and thiocyanate) in saliva. The electrochemical system was designed to detect uric acid and glucose by chronoamperometric measurements in clinically relevant concentrations ranging from 50 to 500 µmol L−1 and from 10 to 5000 µmol L−1, respectively. Meanwhile, the colorimetric paper-based spot tests were optimized to detect nitrite and thiocyanate in concentrations ranging from 5 to 200 µmol L−1 and 0.5 to 2.1 mmol L−1, respectively, using digital image colorimetry. Our affordable tongue depressor (bio)sensors provide results within 5 min and achieve limits of detection in the µmol L−1 range. Importantly, the results provided by our tests when applied to human saliva samples presented excellent concordance with the traditional spectrophotometric method (at a 95 % confidence level), demonstrating the reliability and robustness of our method. In addition, the toxicity and biocompatibility studies of the tongue depressor (bio)sensors were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Calcein acetoxymethyl ester (Calcein AM), and Calcein Propidium Iodide Hoechst (Calcein PI) Analysis, confirming the safety use of the test. Therefore, our tongue depressor (bio)sensor facilitates frequent testing of several biomarkers and can contribute to personalized medicine.

Antibody functionalized capacitance sensor for label-free and real-time detection of bacteria and antibiotic susceptibility

The effective management of infectious diseases and the growing concern of antibiotic resistance necessitates accurate and targeted therapies, highlighting the importance of antibiotic susceptibility testing. This study aimed to develop a real-time impedimetric biosensor for identifying and monitoring bacterial growth and antibiotic susceptibility. The biosensor employed a gold 8-channel disk-shaped microelectrode array with specific antibodies as bio-recognition elements. This setup was allowed for the analysis of bacterial samples, including Staphylococcus aureus, Bacillus cereus, and Micrococcus luteus. These microorganisms were successfully cultured and detected within 1 h of incubation even with a minimal bacterial concentration of 10 CFU/ml. Overall, the developed biosensor array exhibits promising capabilities for monitoring S. aureus, B. cereus and M. luteus, showcasing an excellent linear response ranging from 10 to 104 CFU/ml with a detection limit of 0.95, 1.22 and 1.04 CFU/mL respectively. Moreover, real-time monitoring of antibiotic susceptibility was facilitated by changes in capacitance, which dropped when bacteria were exposed to antibiotic doses higher than their minimum inhibitory concentration (MIC), indicating suppressed bacterial growth. The capacitance measurements enabled determination of half-maximal cytotoxic concentrations (CC50) values for each bacteria-antibiotic pair. As a proof-of-concept application, the developed sensor array was employed as a sensing platform for the real time detection of bacteria in milk samples, which ensured the reliability of the sensor for in-field detection of foodborne pathogens and rapid antimicrobial susceptibility tests (ASTs).

Coupled Poly(ethylenimine) Coreactant to Enhance Electrochemiluminescence of Polymer Dots for Array Imaging of Protein Biomarkers.

Traditional electrochemiluminescent (ECL) bioanalysis suffers from the demand for excessive external coreactants and the damage of reaction intermediates. In this work, a poly(ethylenimine) (PEI)-coupled ECL emitter was proposed by covalently coupling tertiary amine-rich PEI to polymer dots (Pdots). The coupled PEI might act as a highly efficient coreactant to enhance the ECL emission of Pdots through intramolecular electron transfer, reducing the electron transfer distance between emitter and coreactant intermediates and avoiding the disadvantages of traditional ECL systems. Through modification of the PEI-Pdots with tDNA, a sequence partially complementary to cDNA that was complementary to the aptamer of target protein biomarker (aDNA), tDNA-PEI-Pdots were obtained. The biosensors were produced using Au/indium tin oxide (ITO) with an aDNA/cDNA hybrid, and an ECL imaging biosensor array was constructed for ultrasensitive detection of protein biomarkers. Using vascular endothelial growth factor 165 (VEGF165) as a protein model, the proposed ECL imaging method containing two simple incubations with target samples and then tDNA-PEI-Pdots showed a detectable range of 1 pg mL-1 to 100 ng mL-1 and a detection limit of 0.71 pg mL-1, as well as excellent performance such as low toxicity, high sensitivity, excellent selectivity, good accuracy, and acceptable fabrication reproducibility. The PEI-coupled Pdots provide a new avenue for the design of ECL emitters and the application of ECL imaging in disease biomarker detection.

Multiplex signal amplification for ultrasensitive CRP assay via integrated electrochemical biosensor array using MOF-derived carbon material and aptamers

Accurate and precise detection of disease-associated proteins, such as C-reactive protein (CRP), remains a challenge in biosensor development. Herein, we present a novel approach－an integrated disposable aptasensor array－designed for precise, ultra-sensitive, and parallel detection of CRP in plasma samples. This integrated biosensing array platform enables multiplex parallel testing, ensuring the accuracy and reliability in sample analysis. The ultra-sensitivity of this biosensor is achieved through multiplex signal amplification. Leveraging the superior conductivity and extensive surface area of MOF-derived nanoporous carbon material (CMOF), the biosensor enhances recognition elements (aptamers) by catalyzing the horseradish peroxidase (HRP) label enzyme reaction to multiply the number of probe molecules. Optimized conditions yielded exceptional performance, exhibiting high accuracy (relative standard deviation, RSD≤10.0 %), a low detection limit (0.3 pg/mL, S/N = 3), ultra-sensitivity (0.16 μA/ng mL−1 mm−2), and a rapid response (seven parallel tests within 60 min). Importantly, this multi-unit integrated disposable aptasensor array accurately quantified CRP in human serum, demonstrating comparable results to commercial enzyme–linked immunosorbent assay (ELISA). This technology showcases promise for detecting various biomarkers using a unified approach, presenting an appealing strategy for early disease diagnosis and biological analysis.

Plasmon-Stimulated Colorimetry Biosensor Array for the Identification of Multiple Metabolites.

Rationally designing highly catalytic and stable nanozymes for metabolite monitoring is of great importance because of their huge potential in early disease diagnosis. Herein, a novel nanozyme based on hierarchically structured CuS/ZnS with a highly efficient peroxidase (POD)-mimic capability was developed and synthesized for multiple metabolite determination and recognition via the plasmon-stimulated biosensor array strategy. The designed nanozyme can simultaneously harvest plasmon triggered hot electron-hole pairs and generate photothermal properties, leading to a sharply boosted POD-mimic capability under 808 nm laser irradiation. Interestingly, because of the interaction diversity of the metabolite with POD-like nanomaterials, the unique inhibitory effect of metabolites on the POD-mimic activity could be the signal response as the differentiation. Thus, utilizing TMB as a typical chromogenic substrate in the addition of H2O2, the designed colorimetric biosensor array can produce diverse fingerprints for the three vital metabolisms (cysteine (Cys), ascorbic acid (AA), and glutathione (GSH)), which can be precisely identified by principal component analysis (PCA). Notably, a distinct fingerprint of a single metabolite with different levels and metabolite mixtures is also achieved with a detection limit of 1 μM. Most importantly, cell lysis could be effectively discriminated by the biosensor assay, implying its great potential in clinical diagnosis.

Evaluation of restriction and Cas endonuclease kinetics using matrix-insensitive magnetic biosensors

The enzymatic actions of endonucleases in vivo can be altered due to bound substrates and differences in local environments, including enzyme concentration, pH, salinity, ionic strength, and temperature. Thus, accurate estimation of enzymatic reactions in vivo using matrix-dependent methods in solution can be challenging. Here, we report a matrix-insensitive magnetic biosensing platform that enables the measurement of endonuclease activity under different conditions with varying pH, salinity, ionic strength, and temperature. Using biosensor arrays and orthogonal pairs of oligonucleotides, we quantitatively characterized the enzymatic activity of EcoRI under different buffer conditions and in the presence of inhibitors. To mimic a more physiological environment, we monitored the sequence-dependent star activity of EcoRI under unconventional conditions. Furthermore, enzymatic activity was measured in cell culture media, saliva, and serum. Last, we estimated the effective cleavage rates of Cas12a on anchored single-strand DNAs using this platform, which more closely resembles in vivo settings. This platform will facilitate precise characterization of restriction and Cas endonucleases under various conditions.

Colorimetric detection of oral bacteria using functionalized gold nanoparticles as a plasmonic biosensor array.

Early detection of specific oral bacterial species would enable timely treatment and prevention of certain oral diseases. In this work, we investigated the sensitivity and specificity of functionalized gold nanoparticles for plasmonic sensing of oral bacteria. This approach is based on the aggregation of positively charged gold nanoparticles on the negatively charged bacteria surface and the corresponding localized surface plasmon resonance (LSPR) shift. Gold nanoparticles were synthesized in different sizes, shapes and functionalization. A biosensor array was developed consisting of spherical- and anisotropic-shaped (1-hexadecyl) trimethylammonium bromide (CTAB) and spherical mercaptoethylamine (MEA) gold nanoparticles. It was used to detect four oral bacterial species (Aggregatibacter actinomycetemcomitans, Actinomyces naeslundii, Porphyromonas gingivalis and Streptococcus oralis). The plasmonic response was measured and analysed using RGB and UV-vis absorbance values. Both methods successfully detected the individual bacterial species based on their unique responses to the biosensor array. We present an in-depth study relating the bacteria zeta potential and AuNP aggregation to plasmonic response. The sensitivity depends on multiple parameters, such as bacterial species and concentration as well as gold nanoparticle shape, concentration and functionalization.

Investigation of electrocatalysis for tiered-tower micro-electro-mechanical-system-based biosensors: application in the early detection of the thrombosis factor trimethylamine N-oxide.

Trimethylamine N-oxide (TMAO) has been recognized as a biomarker for the early detection of thrombosis. However, testing for TMAO typically requires expensive laboratory equipment and skilled technicians, making it unsuitable for home care pre-screening. To enable its widespread use in home applications, it is crucial to develop a scalable and sensitive device capable of catalyzing TMAO metabolism with a specific enzyme that is tailored for point-of-care use. This study presents an investigation of a MEMS-based two-tiered-tower biosensor array with a detection limit of 0.1 μM for TMAO, aiming to diagnose chronic metabolic diseases using urine or serum samples. Based on the augmented Cole-Cole model, the proposed parameters R_catalyzed, C_catalyzed, and Rp_catalyzed can predict the catalytic impedance of enzymatic activities such as the redox effects of analytes and characterize the small-signal current caused by catalysis. The proposed MEMS biosensor, integrated with a readout circuitry, demonstrates a high sensitivity of 41 ADC counts per μM TMAO (or 4.5 mV μM-1 TMAO), a response time of 1 second, a repetition rate of 98.9%, and a drift over time of 0.5 mV. The sensor effectively distinguishes TMAO based on minute capacitance changes induced by the TorA enzyme, resulting in a discernible distinction of 10.6%. These measurements were successfully compared to conventional cyclic voltammetry (CV) results, showing a variance of only 0.024%. The proposed biosensor is well-suited for pre-screening thrombosis factors for the early detection and prevention of thrombosis in point-of-care applications. The device is cost-effective, lightweight, and demonstrates excellent performance, with a conversion rate of 88% of TMAO and a selectivity rate of 97% for the by-product TMA, allowing for the prediction of cardiovascular risks.

An Electrochemical CMOS Biosensor Array Using Phase-Only Modulation With 0.035% Phase Error And In-Pixel Averaging.

This paper presents a 16×20 CMOS biosensor array based on electrochemical impedance spectroscopy (EIS), a highly sensitive label-free technique for rapid disease detection at point-of-care. This high-density system implements a polar-mode detection with phase-only EIS measurement over a 5 kHz - 1 MHz frequency range. The design features predominantly digital readout circuitry, ensuring scalability with technology, along with a load-compensated transimpedance amplifier at the front, all within a 140×140 μm2; pixel. The architecture enables in-pixel digitization and accumulation, which increases the SNR by 10 dB for each 10× increase in readout time. Implemented in a 180 nm CMOS process, the 3×4 mm2 chip achieves state-of-the-art performance with an rms phase error of 0.035% at 100 kHz through a duty-cycle insensitive phase detector and one of the smallest per pixel areas with in-pixel quantization.