Improving the reproducibility, accuracy, and stability of an electrochemical biosensor platform for point-of-care use

Turbulence-enhanced microneedle immunoassay platform (TMIP) for high-precision biomarker detection from skin interstitial fluid

Conventional diagnostic methods for biomarker detection often require invasive procedures and exhibit limited reproducibility and sensitivity. In this study, the turbulence-enhanced microneedle immunoassay platform (TMIP) was designed to enhance the performance and accuracy of biomarker detection in skin interstitial fluid (ISF). TMIP combines a bullet-shaped microneedle (MN) array for minimally invasive biomarker capture, a microfluidic device for MN-mediated immunoassay process simplification, and a star-shaped magnetic stirrer tool (MST) to facilitate efficient washing. By targeting S100 calcium-binding protein B (S100B), a diagnostic biomarker for melanoma, TMIP demonstrated substantial improvements in reproducibility, reducing signal deviations by up to 55 % compared to manual operation. The application of nanoporous MNs (NPMNs) achieved a low detection limit of 20 pg/mL with a high linearity (R2 = 0.9758). Validation using a gelatin phantom mimicking human skin confirmed TMIP's ability to achieve improved reproducibility and sensitivity. Furthermore, TMIP successfully detected S100B with high reproducibility in both the phantom (R2 = 0.97523) and melanoma-expressing mice within a rapid incubation time of 1 min. TMIP enables the detection of biomarkers with remarkable reproducibility and sub-nanogram sensitivity by simplifying the analysis process and enhancing reagent washing through turbulence. These features suggest that TMIP has the potential to serve as an efficient and reliable tool for biomarker detection in skin ISF.

A label-free electrochemical biosensor for rapid quantification of antimicrobial peptides in teleost fish mucus

We used a thiol-faradaic electrochemical differential pulse voltammetry and impedance spectroscopy on a gold-modified screen-printed carbon electrode to quantify Chrysophsins antimicrobial peptides in the fish mucus without prior extraction. We have developed a specific anti-Chrysophsins polyclonal antibody and used ferrocene as a transducing system. The platform has a sensitivity of 30.5 nA.mL.ng-1 (11.28 nA.nM-1) in a linear range of 0.1-1 µg.mL-1 and a limit of detection of 0.227 ng.mL-1 (84.15 pM). Selectivity, accuracy, repeatability and stability were validated to meet the guidelines of ligand binding assays. Mean Chrysophsins levels in mucus pools from healthy and thermally unstressed Argyrosomus regius, Dicentrarchus labrax and Sparus aurata fish were 8.763 µM (± 0.007), 7.296 µM (± 0.023) and 8.296 (± 0.044) respectively, within the range of mass spectrometry gill values and below the minimum inhibitory concentration (MIC) of Chrysophsins for fish pathogens. The multi-infected D. labrax pool shows a significant decrease in concentration compared to the healthy and thermally stressed pools (p < 0.0262) with 2.8 µM (± 0.024). The thermally stressed A. regius pool is not significantly different from the other pools with 8.763 µM (± 0.007). This electrochemical platform is a flexible tool for real-time targeting of peptide biomarkers in the real matrix and is suitable for mucosal fluids for early fish welfare monitoring.

Silver Nanoparticles for Biosensing and Drug Delivery: A Mechanical Study on DNA Interaction

Silver nanoparticles (AgNPs) have attracted tremendous attention in recent years due to their unique physicochemical properties, including pronounced surface plasmon resonance, tunable size, and amenability to functionalization. These attributes underpin the growing interest in AgNPs as SMART nanocarriers for targeted drug delivery and as active components in biosensing platforms. In this work, we discuss various synthesis strategies for AgNPs-ranging from conventional chemical methods to green approaches-and highlight their subsequent functionalization with anticancer drugs, notably doxorubicin (DOX). We also examine the potential of AgNPs in biosensor applications, emphasizing electrochemical and optical detection modalities capable of monitoring drug release, oxidative stress, and relevant biomarkers. Our experimental data support the conclusion that AgNPs can effectively improve therapeutic efficacy by exploiting tumor-specific conditions (e.g., lower pH) while also enhancing biosensor sensitivity via surface plasmon resonance and electrochemical signal amplification. We provide a thorough discussion of the results, including mechanistic aspects of reactive oxygen species (ROS) generation, drug release kinetics, and sensor performance metrics. Overall, AgNP-based nanocarriers emerge as a powerful platform to address current challenges in precision oncology and medical diagnostics.

MXene-poly(propylene carbonate) nanofiber network-based modification of SPE interfaces for electrochemical immuno-sensing of synthetic cannabinoid

The decriminalization and legalization of cannabis have increased its consumption and the need for effective monitoring methods. Synthetic cannabinoids, while chemically distinct from natural cannabinoids like THC, can be more potent and cause severe adverse effects, often evading detection by traditional drug tests. Thus, there is a critical need for new biosensors that offer rapid, sensitive, and reliable detection of these compounds in biological samples. This study presents a novel electrochemical immunosensor based on aminated MXene integrated with poly(propylene carbonate) (PPC) nanofibers and monoclonal antibodies designed to enhance the detection of synthetic cannabinoids. The PPC/MXene-NH₂ nanofibers, electrospun onto screen-printed electrodes (SPEs), provide increased surface area and high sensitivity, stability, and selectivity. The biosensor achieved a wide detection range of 0.6-2000 ng/mL in saliva, a low limit of detection (LOD) of 0.66 ng/mL, and demonstrated excellent specificity. It showed high repeatability and reproducibility with minimal signal degradation, with vacuum-sealed storage proving to significantly extend sensor stability over time. These results highlight the potential of MXene-enhanced PPC nanofiber immunosensors as sensitive, selective, and portable tools for rapid detection of synthetic cannabinoids in clinical and forensic settings.

A sensitive electrochemical DNA biosensor for detecting the genome of a plant growth-promoting bacteria

The challenge of increasing food production while maintaining environmental sustainability can be addressed by using biofertilizers such as Azospirillum, which can enhance plant growth and colonize more than 100 plant species. The success of this biotechnology depends on the amount of plant growth-promoting bacteria associated with the plant during crop development. However, monitoring bacterial population dynamics after inoculation requires time-consuming, laborious, and costly procedures. To address these issues, this study describes an effective electrochemical DNA biosensor to detect Azospirillum brasilense. The biosensor comprises a glassy carbon electrode modified with a nanocomposite based on carbon nanotubes and gold nanoparticles capped with 3-n-propylpyridinium chloride silsesquioxane, followed by the immobilization of a thiolated probe oligonucleotide that binds specifically to the A. brasilense genome (AZOgenome). The nanocomposite was characterized utilizing spectroscopic and morphological methods. Its presence on the biosensor's surface enhanced electrochemical responses due to its excellent electrocatalytic properties, as observed during electrochemical impedance spectroscopy and cyclic voltammetry experiments. The biosensor enabled the detection of AZOgenome after the hybridization event, which alters the electrochemical response of the electrode and was rapidly detected by square wave voltammetry. The detection range of the bacterial genome was 1.17 pmol L-1 to 146.8 pmol L-1, with LOD and LOQ of 0.261 and 0.322 pmol L-1, respectively, and sensitivity of -15.560 μA/log [AZOgenome] (pmol L-1). The biosensor showed good selectivity and reproducibility, with a coefficient of variation of -5.69 %, in addition to satisfactory sensitivity and stability for up to seven weeks. These promising analytical features allowed the quantification of A. brasilense in low concentrations in soil metagenomic DNA samples.

Point-of-Care NSE Biosensor for Objective Assessment of Stroke Risk

The rapid identification of stroke is critical to improving stroke patient outcomes. Existing protocols for assessing the risk of stroke are subjective and may be further complicated by nonspecific symptoms, increasing the risk of misdiagnosis. Neuron-specific enolase (NSE) has emerged as a promising stroke biomarker. However, current detection methods such as the electrochemiluminescence immunoassay (ECLIA) are time-consuming and costly. In this research, we developed an electrochemical biosensor for the rapid quantification of NSE in whole blood. Mouse stroke models were established, and blood samples collected were analyzed using both hospital-standard ECLIA as well as the biosensor. The biosensor limit of detection was 1.15 ng/mL. NSE measurements were highly correlated between the two methods and were obtained in 5 min using 20 μL of unprocessed whole blood samples. Notably, the biosensor could accurately quantify elevated blood NSE blood that was associated with more severe stroke. Our results demonstrate the utility of the proposed biosensor in pre-hospital settings. Combined with existing stroke assessment methods, the biosensor may enable emergency personnel to identify stroke risk with greater accuracy to optimize the chances of receiving necessary treatment within the effective window.

Electrochemical Biosensors for the Detection of Exosomal microRNA Biomarkers for Early Diagnosis of Neurodegenerative Diseases

Early and precise diagnosis of neurodegenerative disorders like Alzheimer's (AD) and Parkinson's (PD) is crucial for slowing their progression and enhancing patient outcomes. Exosomal microRNAs (miRNAs) are emerging as promising biomarkers due to their ability to reflect the diseases' pathology, yet their low abundance poses significant detection hurdles. This review article delves into the burgeoning field of electrochemical biosensors, designed for the precise detection of exosomal miRNA biomarkers. Electrochemical biosensors offer a compelling solution, combining the sensitivity required to detect low-abundance biomarkers with the specificity needed to discern miRNA profiles distinctive to neural pathological states. We explore the operational principles of these biosensors, including the electrochemical transduction mechanisms that facilitate miRNA detection. The review also summarizes advancements in nanotechnology, signal enhancement, bioreceptor anchoring, and microfluidic integration that improve sensor accuracy. The evidence of their use in neurodegenerative disease diagnosis is analyzed, focusing on the clinical impact, diagnostic precision, and obstacles faced in practical applications. Their potential integration into point-of-care testing and regulatory considerations for their market entry are discussed. Looking toward the future, the article highlights forthcoming innovations that might revolutionize early diagnostic processes. Electrochemical biosensors, with their impressive sensitivity, specificity, and point-of-care compatibility, are on track to become instrumental in the early diagnosis of neurodegenerative diseases, possibly transforming patient care and prognosis.

A combinatorial approach to chicken meat spoilage detection using color-shifting silver nanoparticles, smartphone imaging, and artificial neural network (ANN)

Ensuring food freshness is crucial for public health. Biogenic amines (like histamine) are reliable spoilage indicators in protein-rich foods such as meat. This study presents a label-free colorimetric sensor using green-colored silver nanoparticles (AgNPs) functionalized with carboxylated polyvinylpyrrolidone (PVP-COOH) for sensitive BA detection. After optimizing pH, time, and temperature, the modified AgNPs achieved a detection limit (LOD) of 0.21 μg/mL and an analytical dynamic range of 10-100 μg/mL for histamine. Smartphone imaging was employed to capture colorimetric changes, and the extracted data were used to train an artificial neural network (ANN), enhancing the LOD to 0.09 μg/mL and extending the dynamic range to 0.5-200 μg/mL. The sensor was validated with real food samples, successfully monitoring histamine levels in chicken meat over three days, detecting spoilage-related changes with high sensitivity. This integrative approach combining AgNPs, smartphone imaging, and AI offers a powerful tool for advanced food freshness monitoring.

MXene Nanoconfinement of SAM-Modified Molecularly Imprinted Electrochemical Biosensor for Point-of-Care Monitoring of Carcinoembryonic Antigen

The high rate of cancer worldwide and the heavy costs imposed on governments and humanity have always motivated researchers to develop point-of-care (POC) biosensors for easy diagnosis and monitoring of cancer treatment. Herein, we report on a label-free impedimetric biosensor based on Ti3C2Tx MXene and imprinted ortho-phenylenediamine (o-PD) for the detection of carcinoembryonic antigen (CEA), a biomarker for various cancers surveillance, especially colorectal cancer (CRC). Accordingly, MXene was drop-casted on the surface of a disposable silver electrode to increase the sensitivity and create high-energy nanoareas on the surface, which are usable for protein immobilization and detection. A self-assembled monolayer (SAM) was exploited for oriented CEA immobilization on the MXene-modified electrode. The monomer-protein interaction and successful protein removal were confirmed by molecular docking and atomic force microscopy (AFM) investigations to evaluate the quality of the fabricated molecularly imprinted polymer (MIP). Also, the role of MXene in increasing the electrical field inside the nanoareas was simulated using COMSOL Multiphysics software. A suitable limit of detection (9.41 ng/mL), an appropriate linear range of detection (10 to 100 ng/mL) in human serum, and a short detection time (10 min) resulted from the use of SAM/MIP next to MXene. This biosensor presented outstanding repeatability (97.60%) and reproducibility (98.61%). Moreover, acceptable accuracy (between 93.04 and 116.04%) in clinical serum samples was obtained compared with immunoassay results, indicating the high potential of our biosensor for real sample analysis. This biomimetic and disposable sensor provides a cost-effective method for facile and POC monitoring of cancer patients during treatment.

Electrochemical Determination of Dipyrone Using a Cold-Plasma-Treated Graphite Sheet Electrode

The development of fast, reliable, and cost-effective techniques for pharmaceutical compound analysis is an issue of paramount importance to the pharmaceutical industry, environmental sciences, and many other applications. In this work, a low-cost graphite sheet electrode (GSE) was used as a disposable working electrode. To this purpose, the GSE surface was subjected to a cold plasma discharge using a mixture of argon and O2. The sensor was applied to dipyrone (DIP) quantification. Initially, the influence of pH on the electrochemical response of DIP on the pyrolytic graphite sheet (PGS) electrodes was evaluated using a 0.12 mol L-1 Britton-Robinson buffer solution at pH values ranging from 2.0 to 12.0. The solution adjusted to pH 4.0 was selected as the supporting electrolyte for the experiments since a larger current intensity was obtained at this medium. The mass transport of DIP toward the PGS surface was investigated by cyclic voltammetry, evidencing a diffusion-controlled process. DIP was initially quantified by square wave voltammetry (SWV) with a linear range of about 2.5-200 μmol L-1 and a calculated limit of detection of about 0.31 μmol L-1. Finally, SWV was used to enable DIP detection in synthetic urine solutions, demonstrating its applicability as a sensor tool in real analysis.

CRISPR-associated Plasmonic Colorimeter Method (Ca-PCM): A real-time RGB detection system for gold nanoparticles-based nucleic acid biosensors

BACKGROUND

The detection of genetic sequences represents the gold standard procedure for species discrimination, genetic characterisation of tumours, and identification of pathogens. The development of new molecular detection methods, accessible and cost effective, is of great relevance. Biosensors based on plasmonic nanoparticles, such as gold nanoparticles (AuNPs), provide a powerful and versatile platform for highly sensitive, economic, user-friendly and label-free sensing. However, the readout techniques typically employed with such sensors lack temporal and kinetic information, which hampers the ability to perform quantitative detection.

RESULTS

In this study, a novel methodology designated the 'CRISPR-associated Plasmonic Colorimeter Method' (Ca-PCM), has been developed. This method combines RNA target recognition by CRISPR LwaCas13a, AuNPs' aggregation, and real-time colorimetric Red-Green-Blue (RGB) analysis. The system registers the AuNP's plasmonic signatures in real-time using a RGB colour sensor with 3-channel silicon photodiodes having blue, green and red sensitivities. The acquired signals are automatically analysed by an algorithm designed to distinguish between positive and negative samples and to correlate the temporal spectral patterns of aggregation with dose-dependent molecular detection of the RNA target. In addition, the combination of Ca-PCM with a previous isothermal amplification allows the target efficient detection in real clinical applications.

SIGNIFICANCE

We have shown that the combination of RGB analysis and continuous temporal measurements is a novel and promising method to characterise the behaviour of gold nanoparticle-based biosensors and to achieve dose-dependent target detection. In addition, the simplicity and cost-effectiveness of this new approach expand the possibilities of other plasmonic-based biosensors and their applicability in low-resources clinical environments.

Single-Atom Iridium-doped Carbon Dots Nanozyme with High Peroxidase-Like Activity as Colorimetric Sensors for Multimodal Detection of Mercury Ions

Nanozyme-based colorimetric sensors are promising approaches for environmental monitoring, food safety, and medical diagnostics. However, developing novel nanozymes that exhibit high catalytic activity, good dispersion in aqueous solution, high sensitivity, selectivity, and stability is challenging. In this study, for the first time, single-atom iridium-doped carbon dot nanozymes (SA Ir-CDs) are synthesized via a simple in situ pyrolysis process. Doping carbon dots with iridium in the form of single atoms to achieve maximum atomic utilization not only enhances peroxidase (POD)-like activity to 178.81 U mg-1 but also improves the dispersibility of single-atom nanozymes in aqueous solutions over 30 days. Hence, the SA Ir-CD colorimetric platform is developed for mercury ions (Hg2+) detection and exhibited a good linear relationship from 0.01 to 10 µm and a detection limit of 4.4 nm. Notably, the changes in color can be observed not only through the naked eye but also via a smartphone, enabling convenient field and onsite monitoring without the need for sophisticated analytical equipment. In this study, an approach for fabricating single-atom metal-based carbon dot nanozymes with high POD-like activity is developed, and a new effective and easy-to-use colorimetric sensor for Hg2+ detection is constructed.

MXene Hydrogels for Soft Multifunctional Sensing: A Synthesis-Centric Review

Intelligent wearable sensors based on MXenes hydrogels are rapidly advancing the frontier of personalized healthcare management. MXenes, a new class of transition metal carbon/nitride synthesized only a decade ago, have proved to be a promising candidate for soft sensors, advanced human-machine interfaces, and biomimicking systems due to their controllable and high electrical conductivity, as well as their unique mechanical properties as derived from their atomistically thin layered structure. In addition, MXenes' biocompatibility, hydrophilicity, and antifouling properties render them particularly suitable to synergize with hydrogels into a composite for mechanoelectrical functions. Nonetheless, while the use of MXene as a multifunctional surface or an electrical current collector such as an energy device electrode is prevalent, its incorporation into a gel system for the purpose of sensing is vastly less understood and formalized. This review provides a systematic exposition to the synthesis, property, and application of MXene hydrogels for intelligent wearable sensors. Specific challenges and opportunities on the synthesis of MXene hydrogels and their adoption in practical applications are explicitly analyzed and discussed to facilitate cross gemination across disciplines to advance the potential of MXene multifunctional sensing hydrogels.

Ionic liquid-reinforced Hydroxyapatite@nano-TiO2 as a green platform for Immuno-electrochemical sensing applications

In contemporary society, developing dependable point-of-care (POC) biosensors for the timely detection of cancer markers is crucial. Among various sensor types, screen-printed electrode (SPE)-based sensors, particularly electrochemical ones, stand out as promising candidates for POC applications. Despite ongoing efforts to create numerous SPE-based sensors, there is a continuous pursuit to enhance their sensitivity and analytical capabilities. This study presents an advanced electrochemical sensor designed to sensitively detect the hepatocellular carcinoma (HCC) marker Alpha-fetoprotein (AFP) in saliva. The sensor employs a gold SPE modified with hydroxyapatite, TiO2 nanoparticles, 1-butyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ionic liquid (IL), and AFP monoclonal antibodies. After thorough characterization and optimization using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), the biosensor exhibited a broad detection range (0.01-400 ng/mL), a low limit of detection (LOD) at 0.058 ng/mL, and demonstrated high selectivity, repeatability, reproducibility, and stability. Furthermore, when tested with spiked human saliva samples, the biosensor displayed excellent recovery and robustness, showcasing its potential for noninvasive and POC diagnosis of HCC. In an environmentally conscious evaluation, the biosensor's greenness was assessed using the AGREE metric, yielding a high score of 0.85. This score indicates the biosensor's alignment with the principles of green analytical chemistry, underlining its eco-friendly attributes. This innovative electrochemical sensor contributes to the ongoing efforts for efficient and reliable POC diagnostic tools and aligns with a broader commitment to developing environmentally friendly solutions.

A Novel PCR-Free Ultrasensitive GQD-Based Label-Free Electrochemical DNA Sensor for Sensitive and Rapid Detection of Francisella tularensis

Biological warfare agents are infectious microorganisms or toxins capable of harming or killing humans. Francisella tularensis is a potential bioterrorism agent that is highly infectious, even at very low doses. Biosensors for biological warfare agents are simple yet reliable point-of-care analytical tools. Developing highly sensitive, reliable, and cost-effective label-free DNA biosensors poses significant challenges, particularly when utilizing traditional techniques such as fluorescence, electrochemical methods, and others. These challenges arise primarily due to the need for labeling, enzymes, or complex modifications, which can complicate the design and implementation of biosensors. In this study, we fabricated Graphene Quantum dot (GQD)-functionalized biosensors for highly sensitive label-free DNA detection. GQDs were immobilized on the surface of screen-printed gold electrodes via mercaptoacetic acid with a thiol group. The single-stranded DNA (ssDNA) probe was also immobilized on GQDs through strong π-π interactions. The ssDNA probe can hybridize with the ssDNA target and form double-stranded DNA, leading to a decrease in the effect of GQD but a positive shift associated with the increase in DNA concentration. The specificity of the developed system was observed with different microorganism target DNAs and up to three-base mismatches in the target DNA, effectively distinguishing the target DNA. The response time for the target DNA molecule is approximately 1010 s (17 min). Experimental steps were monitored using UV/Vis spectroscopy, Atomic Force Microscopy (AFM), and electrochemical techniques to confirm the successful fabrication of the biosensor. The detection limit can reach 0.1 nM, which is two-five orders of magnitude lower than previously reported methods. The biosensor also exhibits a good linear range from 105 to 0.01 nM and has good specificity. The biosensor's detection limit (LOD) was evaluated as 0.1 nM from the standard calibration curve, with a correlation coefficient of R2 = 0.9712, showing a good linear range and specificity. Here, we demonstrate a cost-effective, GQD-based SPGE/F. tularensis DNA test suitable for portable electrochemical devices. This application provides good perspectives for point-of-care portable electrochemical devices that integrate sample processing and detection into a single cartridge without requiring a PCR before detection. Based on these results, it can be concluded that this is the first enzyme-free electrochemical DNA biosensor developed for the rapid and sensitive detection of F. tularensis, leveraging the nanoenzyme and catalytic properties of GQDs.

Aptamer-Mediated Electrochemical Detection of SARS-CoV-2 Nucleocapsid Protein in Saliva

Gold standard detection of SARS-CoV-2 by reverse transcription quantitative PCR (RT-qPCR) can achieve ultrasensitive viral detection down to a few RNA copies per sample. Yet, the lengthy detection and labor-intensive protocol limit its effectiveness in community screening. In view of this, a structural switching electrochemical aptamer-based biosensor (E-AB) targeting the SARS-CoV-2 nucleocapsid (N) protein was developed. Four N protein-targeting aptamers were characterized on an electrochemical cell configuration using square wave voltammetry (SWV). The sensor was investigated in an artificial saliva matrix optimizing the aptamer anchoring orientation, SWV interrogation frequency, and target incubation time. Rapid detection of the N protein was achieved within 5 min at a low nanomolar limit of detection (LOD) with high specificity. Specific N protein detection was also achieved in simulated positive saliva samples, demonstrating its feasibility for saliva-based rapid diagnosis. Further research will incorporate novel signal amplification strategies to improve sensitivity for early diagnosis.

Advances in Bioreceptor Layer Engineering in Nanomaterial-based Sensing of Pseudomonas Aeruginosa and its Metabolites

Pseudomonas aeruginosa is a pathogen that infects wounds and burns and causes severe infections in immunocompromised humans. The high virulence, the rise of antibiotic-resistant strains, and the easy transmissibility of P. aeruginosa necessitate its fast detection and control. The gold standard for detecting P. aeruginosa, the plate culture method, though reliable, takes several days to complete. Therefore, developing accurate, rapid, and easy-to-use diagnostic tools for P. aeruginosa is highly desirable. Nanomaterial-based biosensors are at the forefront of detecting P. aeruginosa and its secondary metabolites. This review summarises the biorecognition elements, biomarkers, immobilisation strategies, and current state-of-the-art biosensors for P. aeruginosa. The review highlights the underlying principles of bioreceptor layer engineering and the design of optical, electrochemical, mass-based, and thermal biosensors based on nanomaterials. The advantages and disadvantages of these biosensors and their future point-of-care applications are also discussed. This review outlines significant advancements in biosensors and sensors for detecting P. aeruginosa and its metabolites. Research efforts have identified biorecognition elements specific and selective towards P. aeruginosa. The stability, ease of preparation, cost-effectiveness, and integration of these biorecognition elements onto transducers are pivotal for their application in biosensors and sensors. At the same time, when developing sensors for clinically significant analytes such as P. aeruginosa, virulence factors need to be addressed, such as the sensor's sensitivity, reliability, and response time in samples obtained from patients. The point-of-care applicability of the developed sensor may be an added advantage since it enables onsite determination. In this context, optical methods developed for P. aeruginosa offer promising potential.

Soil microbiome characterization and its future directions with biosensing

Soil microbiome characterization is typically achieved with next-generation sequencing (NGS) techniques. Metabarcoding is very common, and meta-omics is growing in popularity. These techniques have been instrumental in microbiology, but they have limitations. They require extensive time, funding, expertise, and computing power to be effective. Moreover, these techniques are restricted to controlled laboratory conditions; they are not applicable in field settings, nor can they rapidly generate data. This hinders using NGS as an environmental monitoring tool or an in-situ checking device. Biosensing technology can be applied to soil microbiome characterization to overcome these limitations and to complement NGS techniques. Biosensing has been used in biomedical applications for decades, and many successful commercial products are on the market. Given its previous success, biosensing has much to offer soil microbiome characterization. There is a great variety of biosensors and biosensing techniques, and a few in particular are better suited for soil field studies. Aptamers are more stable than enzymes or antibodies and are more ready for field-use biosensors. Given that any microbiome is complex, a multiplex sensor will be needed, and with large, complicated datasets, machine learning might benefit these analyses. If the signals from the biosensors are optical, a smartphone can be used as a portable optical reader and potential data-analyzing device. Biosensing is a rich field that couples engineering and biology, and applying its toolset to help advance soil microbiome characterization would be a boon to microbiology more broadly.

Recent advances on nanomaterial-based glutathione sensors

Glutathione (GSH) is one of the most common thiol-containing molecules discovered in biological systems, and it plays an important role in many cellular functions, where changes in physiological glutathione levels contribute to the progress of a variety of diseases. Molecular imaging employing fluorescent probes is thought to be a sensitive technique for online fluorescence detection of GSH. Although various molecular probes for (intracellular) GSH sensing have been reported, some aspects remain unanswered, such as quantitative intracellular analysis, dynamic monitoring, and compatibility with biological environment. Some of these drawbacks can be overcome by sensors based on nanostructured materials, that have attracted considerable attention owing to their exceptional properties, including a large surface area, heightened electro-catalytic activity, and robust mechanical resilience, for which they have become integral components in the development of highly sensitive chemo- and biosensors. Additionally, engineered nanomaterials have demonstrated significant promise in enhancing the precision of disease diagnosis and refining treatment specificity. The aim of this review is to investigate recent advancements in fabricated nanomaterials tailored for detecting GSH. Specifically, it examines various material categories, encompassing carbon, polymeric, quantum dots (QDs), covalent organic frameworks (COFs), metal-organic frameworks (MOFs), metal-based, and silicon-based nanomaterials, applied in the fabrication of chemo- and biosensors. The fabrication of nano-biosensors, mechanisms, and methodologies employed for GSH detection utilizing these fabricated nanomaterials will also be elucidated. Remarkably, there is a noticeable absence of existing reviews specifically dedicated to the nanomaterials for GSH detection since they are not comprehensive in the case of nano-fabrication, mechanisms and methodologies of detection, as well as applications in various biological environments. This research gap presents an opportune moment to thoroughly assess the potential of nanomaterial-based approaches in advancing GSH detection methodologies.

Development of cross-linked glucose oxidase integrated Cu-nanoflower electrode for reusable and stable glucose sensing

The demand for glucose-sensing devices has increased along with the increasing diabetic population. Here, we aimed to construct a system with a glucose oxidase (GOx)-integrated Cu-nanoflower (Cu-NF) as the underlying electrode. This novel system was successfully developed by creating a cross-linked GOx within a Cu-NF matrix, forming a c-GOx@Cu-NF-coated film on a carbon screen-printed electrode (CSPE). A comparison of the stabilities of the cross-linking methods demonstrated enhanced durability, with an activity level of >88 % maintained after approximately 35 days of storage in room temperature buffer. Regarding the ability of the c-GOx@Cu-NF modified CSPE to detect glucose via electrochemical methods, the redox potential gap (ΔE) and peak current increased in the presence of GOx. In comparison to that of glucose, the sensitivity of c-GOx@Cu-NF was approximately 8 times greater than that of GOx@Cu-NF, with a detection limit of 0.649 μM and a linear range of 5-500 μM. It sustained an average relative activity of 80 % over 20 days. After 10 cycles of repeated use, the activity remained above 75 %. In terms of evaluating the electrode's specificity for glucose, the detection rate for individual similar substances was approximately 1 %. The introduction of a crosslinking strategy to Cu-NF, leading to enhanced mechanical stability and conductivity, improved the detection capability. Furthermore, this approach led to increased long-term storage stability and reusability, allowing for specific glucose detection. To our knowledge, this report represents the first demonstration of a c-GOx@Cu-NF system for integrating electrochemical biosensing devices into digital healthcare pathways, offering enhanced sensing accuracy and mechanical stability.

High versatility of polyethylene terephthalate (PET) waste for the development of batteries, biosensing and gas sensing devices

Continuously growing adoption of electronic devices in energy storage, human health and environmental monitoring systems increases demand for cost-effective, lightweight, comfortable, and highly efficient functional structures. In this regard, the recycling and reuse of polyethylene terephthalate (PET) waste in the aforementioned fields due to its excellent mechanical properties and chemical resistance is an effective solution to reduce plastic waste. Herein, we review recent advances in synthesis procedures and research studies on the integration of PET into energy storage (Li-ion batteries) and the detection of gaseous and biological species. The operating principles of such systems are described and the role of recycled PET for various types of architectures is discussed. Modifying the composition, crystallinity, surface porosity, and polar surface functional groups of PET are important factors for tuning its features as the active or substrate material in biological and gas sensors. The findings indicate that conceptually new pathways to the study are opened up for the effective application of recycled PET in the design of Li-ion batteries, as well as biochemical and catalytic detection systems. The current challenges in these fields are also presented with perspectives on the opportunities that may enable a circular economy in PET use.

Laser-printed paper ELISA and hydroxyapatite immobilization for colorimetric congenital anomalies screening in saliva

BACKGROUND

Alpha-fetoprotein (AFP) is a fetal protein that can indicate congenital anomalies such as Down syndrome and spinal canal blockage when detected at abnormal levels in pregnant women. Current AFP detection methods rely on invasive blood or serum samples, which require sophisticated equipment. From the many solutions proposed, colorimetric paper-based assays excel in point-of-care settings. The concept of paper-based ELISA (p-ELISA) enhances traditional methods, aligning with the ASSURED criteria for diagnostics in resource-limited regions. Despite success in microfluidic paper-based assay devices, laser printing remains underexplored for p-ELISA. Additionally, modifying the paper surface provides an additional layer of sensitivity enhancement.

RESULTS

In this study, we developed a novel laser-printed paper-based ELISA (LP-pELISA) for rapid, sensitive, and noninvasive detection of AFP in saliva samples. The LP-pELISA platform was fabricated by printing hydrophobic barriers on filter paper using a laser printer, followed by depositing hydroxyapatite (HAp) as an immobilization material for the antibodies. The colorimetric detection was achieved using AuNPs functionalized with anti-AFP antibodies and silver nitrate enhancement. The LP-pELISA exhibited a linear response for AFP detection in both buffer and saliva samples over a range of 1.0-800 ng mL-1, with a limit of detection (LOD) reaching 1.0 ng mL-1. The assay also demonstrated good selectivity, repeatability, reproducibility, and stability. The LP-pELISA was further validated by testing spiked human saliva samples, showing its potential for point-of-care diagnosis of congenital disabilities.

SIGNIFICANCE

The LP-pELISA is a noninvasive platform showcasing simplicity, cost-effectiveness, and user-friendliness, utilizing laser printing, hydroxyapatite modification, and saliva samples to efficiently detect AFP. Beyond its application for AFP, this method's versatility extends to other biomarkers, positioning it as a catalyst for the evolution of paper-based biosensors. The LP-pELISA holds promise as a transformative tool for point-of-care diagnostics, fostering advancements in healthcare with its innovative technology.

Dual Chromatic Laser-Printed Microfluidic Paper-Based Analytical Device (μPAD) for the Detection of Atrazine in Water

Water pollution caused by pesticides is a significant threat to the environment and human health. Silver and gold nanoparticle (AgNPs, AuNPs)-based biosensors are affordable tools, ideal for environmental monitoring. Microfluidic paper-based devices (μPADs) are a promising approach for on-site testing, but few studies have explored the use of laser printing (LP) for μPAD-based biosensors. This study investigates the feasibility of using laser printing to fabricate paper-based biosensors for pesticide detection in water samples. The μPAD was designed and optimized by using different filter paper porosities, patterns, and channel thicknesses. The developed LP-μPAD was used to sense the pesticide atrazine in water through colorimetric assessments using a smartphone-assisted image analysis. The analytical assessment showed a limit of detection (LOD) of 3.5 and 10.9 μM for AgNPs and AuNPs, respectively. The sensor had high repeatability and reproducibility. The LP-μPAD also demonstrated good recovery and functionality in simulated contaminated water. Furthermore, the detection of pesticides was found to be specific under the influence of interferents, such as NaCl and pH levels. By combining laser printing and nanoparticles, the proposed sensor could contribute to developing effective and low-cost solutions for monitoring water quality that are widely accessible.

Improved production of β-carotene in light-powered Escherichia coli by co-expression of Gloeobacter rhodopsin expression

BACKGROUND

Providing sufficient and usable energy for the cell factory has long been a heated issue in biosynthesis as solar energy has never been rooted out from the strategy for improvement, and turning Escherichia coli (E. coli) into a phototrophic host has multiple captivating qualities for biosynthesis. In this study, β-carotene was a stable compound for production in E. coli with the expression of four enzymes (CrtE, CrtB, CrtI, CrtY) for production due to its light-harvesting feature as an antenna pigment and as an antioxidant and important precursor for human health. The expression of Gloeobacter rhodopsin (GR) in microbial organisms was proved to have potential for application.

RESULTS

The expression of fusion protein, GR-GFP, in E. coli showed visible GFP signal under fluorescent microscopy, and its in vivo proton pumping activity signal can be detected in induced photocurrent by electrodes on the chip under intervals of illumination. To assess the phototrophic synthesis ability of the host strain compared to wild-type and vector control strain in chemostat batch with illumination, the expression of red fluorescent protein (RFP) as a target protein showed its yield improvement in protein assay and also reflected its early dominance in RFP fluorescence signal during the incubation, whereas the synthesis of β-carotene also showed yield increase by 1.36-fold and 2.32-fold compared with its wildtype and vector control strain. To investigate the effect of GR-GFP on E. coli, the growth of the host showed early rise into the exponential phase compared to the vector control strain and glucose turnover rate was elevated in increased glucose intake rate and upregulation of ATP-related genes in glycolysis (PtsG, Pgk, Pyk).

CONCLUSION

We reported the first-time potential application of GR in the form of fusion protein GR-GFP. Expression of GR-GFP in E. coli improved the production of β-carotene and RFP. Our work provides a strain of E. coli harboring phototrophic metabolism, thus paving path to a more sustainable and scalable production of biosynthesis.

MEASURE: Multiplex Exhaled Breath Condensate - Scanning Using Rapid Electro-Analytics

Exhaled breath condensate is an emerging source of inflammatory biomarkers suitable for the noninvasive detection of respiratory disorders. Current gold standard methods are highly invasive and pose challenges in sample collection during airway inflammation monitoring. Cytokine biomarkers are detectable in EBC at increased or decreased concentrations. IL-6, IL-1β, IL-8, and hs-CRP are characteristic biomarkers identified in respiratory disorders. We have demonstrated the promising outcomes of a 16-plexed electrochemical platform - READ 2.0 for the multiplexed detection of characteristic biomarkers in EBC. The sensor demonstrates dynamic ranges of 1-243 pg/mL with a lower detection limit of 1 pg/mL for IL-6 and IL-1β, while the detection range and limit of detection for IL-8 and hs-CRP is 1-150 pg/mL and 3 pg/mL, respectively. The detection accuracies for the biomarkers are in the range of ∼85 ± 15% to ∼100 ± 10%. The sensor shows a nonspecific response to similar cross-reacting biomarkers. Analytical validation of the sensor with ELISA as the standard reference generated a correlation of R2 > 0.96 and mean biases of 10.9, 3.5, 17.4, and 3.9 pg/mL between the two methods for IL-6, IL-1β, IL-8, and hs-CRP, respectively. The precision of the sensor in detecting low biomarker concentrations yields a %CV of <7%. The variation in the sensor's response on repeat EBC sample measurements and within a 6 h duration is less than 10%. The READ 2.0 platform shows a promise that EBC-based biomarker detection can prove to be vital in predicting the severity and survival rates of respiratory disorders and serve as a reference point for monitoring EBC-based biomarkers.

The convergence of traditional and digital biomarkers through AI-assisted biosensing: A new era in translational diagnostics?

Advances in consumer electronics, alongside the fields of microfluidics and nanotechnology have brought to the fore low-cost wearable/portable smart devices. Although numerous smart devices that track digital biomarkers have been successfully translated from bench-to-bedside, only a few follow the same fate when it comes to track traditional biomarkers. Current practices still involve laboratory-based tests, followed by blood collection, conducted in a clinical setting as they require trained personnel and specialized equipment. In fact, real-time, passive/active and robust sensing of physiological and behavioural data from patients that can feed artificial intelligence (AI)-based models can significantly improve decision-making, diagnosis and treatment at the point-of-procedure, by circumventing conventional methods of sampling, and in person investigation by expert pathologists, who are scarce in developing countries. This review brings together conventional and digital biomarker sensing through portable and autonomous miniaturized devices. We first summarise the technological advances in each field vs the current clinical practices and we conclude by merging the two worlds of traditional and digital biomarkers through AI/ML technologies to improve patient diagnosis and treatment. The fundamental role, limitations and prospects of AI in realizing this potential and enhancing the existing technologies to facilitate the development and clinical translation of "point-of-care" (POC) diagnostics is finally showcased.

Toward Personalized Nanomedicine: The Critical Evaluation of Micro and Nanodevices for Cancer Biomarker Analysis in Liquid Biopsy

Liquid biopsy for the analysis of circulating cancer biomarkers (CBs) is a major advancement toward the early detection of cancer. In comparison to tissue biopsy techniques, liquid biopsy is relatively painless, offering multiple sampling opportunities across easily accessible bodily fluids such as blood, urine, and saliva. Liquid biopsy is also relatively inexpensive and simple, avoiding the requirement for specialized laboratory equipment or trained medical staff. Major advances in the field of liquid biopsy are attributed largely to developments in nanotechnology and microfabrication that enables the creation of highly precise chip-based platforms. These devices can overcome detection limitations of an individual biomarker by detecting multiple markers simultaneously on the same chip, or by featuring integrated and combined target separation techniques. In this review, the major advances in the field of portable and semi-portable micro, nano, and multiplexed platforms for CB detection for the early diagnosis of cancer are highlighted. A comparative discussion is also provided, noting merits and drawbacks of the platforms, especially in terms of portability. Finally, key challenges toward device portability and possible solutions, as well as discussing the future direction of the field are highlighted.

A label-free electrochemical DNA biosensor used a printed circuit board gold electrode (PCBGE) to detect SARS-CoV-2 without amplification

The emergence of coronavirus disease 2019 (COVID-19) motivates continuous efforts to develop robust and accurate diagnostic tests to detect severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Detection of viral nucleic acids provides the highest sensitivity and selectivity for diagnosing early and asymptomatic infection because the human immune system may not be active at this stage. Therefore, this work aims to develop a label-free electrochemical DNA biosensor for SARS-CoV-2 detection using a printed circuit board-based gold substrate (PCBGE). The developed sensor used the nucleocapsid phosphoprotein (N) gene as a biomarker. The DNA sensor-based PCBGE was fabricated by self-assembling a thiolated single-stranded DNA (ssDNA) probe onto an Au surface, which performed as the working electrode (WE). The Au surface was then treated with 6-mercapto-1-hexanol (MCH) before detecting the target N gene to produce a well-oriented arrangement of the immobilized ssDNA chains. The successful fabrication of the biosensor was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM). The DNA biosensor performances were evaluated using a synthetic SARS-CoV-2 genome and 20 clinical RNA samples from healthy and infected individuals through EIS. The developed DNA biosensor can detect as low as 1 copy per μL of the N gene within 5 minutes with a LOD of 0.50 μM. Interestingly, the proposed DNA sensor could distinguish the expression of SARS-CoV-2 RNA in a patient diagnosed with COVID-19 without any amplification technique. We believe that the proposed DNA sensor platform is a promising point-of-care (POC) device for COVID-19 viral infection since it offers a rapid detection time with a simple design and workflow detection system, as well as an affordable diagnostic assay.

Redox-labelled detection probe enabled immunoassay for simultaneous detection of multiple cancer biomarkers

Some of the cancer biomarkers often lack specificity and sensitivity; thus, simultaneous detection of multiple biomarkers can make the diagnosis more accurate. Also, simple sensing system without utilization of extra reagents like mediator or substrate during detection event is desirable for point-of-care testing. To address this, mediator and substrate-free amperometric biosensor for simultaneous detection of cancer biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) have been demonstrated by designing two different redox-labelled detection probes. Colloidal nanoparticles of polyaniline-pectin conjugated with AFP antibody along with ferrocene and silver nanoparticles conjugated with CEA antibody along with anthraquinone were used as redox probes to bind with AFP and CEA during the detection event. Sensor constructed using carboxylic acid tethered polyaniline as immobilization matrix displayed 5 times wider linear range than conventional polyaniline for AFP and CEA detection by sandwich electrochemical assay. The detection limit was 30 pg mL^-1 for AFP and 80 pg mL^-1 for CEA. The biosensor displayed appropriate sensitivity, good specificity, and negligible cross-reactivity between the two targets. The proposed sensor was used to determine APF and CEA in human blood serum. The strategy demonstrated can be further extended for detection of panel of cancer biomarkers by designing appropriate redox probes.

Detection of rare CTCs by electrochemical biosensor built on quaternary PdPtCuRu nanospheres with mesoporous architectures

Circulating tumor cells (CTCs) are promising liquid biopsy biomarkers for early cancer detection and anti-cancer therapy evaluation. The ultra-low abundance of CTCs in blood samples requires highly sensitive and accurate detection ways. In this study, we propose the design of a dual-recognition electrochemical biosensor to improve both the specificity and signal response. PdPtCuRu mesoporous nanospheres (PdPtCuRu MNSs) with excellent three dimensions (3D) nanopore structures were synthesized by one-pot method and connected to mucin 1 (MUC1) aptamer to serve as signal amplification probe. Besides, superconductive carbon black, Ketjen Black (KB), and gold nanoparticles (AuNPs) modified organometallic frame (CeMOF-Au) were combined to work as signal transducer. The characteristic branching structure of KB provides abundant contact points to load CeMOF-Au to heighten the interface electron transfer rate. In addition, AuNPs were reduced on the surface of CeMOF, which could effectively bind the capture antibody and further enhance the conductivity. Under the optimized condition, the limit of detection (LOD) of the as-constructed biosensor was less than 10 cells mL^-1 for model A549 cells, and showed good specificity and accuracy in spiked serum samples. We envision the as-proposed electrochemical biosensor would alternate as a useful tool for the clinical detection of CTCs for cancer diagnosis.

2D MXene-Based Biosensing: A Review

MXene emerged as decent 2D material and has been exploited for numerous applications in the last decade. The remunerations of the ideal metallic conductivity, optical absorbance, mechanical stability, higher heterogeneous electron transfer rate, and good redox capability have made MXene a potential candidate for biosensing applications. The hydrophilic nature, biocompatibility, antifouling, and anti-toxicity properties have opened avenues for MXene to perform in vitro and in vivo analysis. In this review, the concept, operating principle, detailed mechanism, and characteristic properties are comprehensively assessed and compiled along with breakthroughs in MXene fabrication and conjugation strategies for the development of unique electrochemical and optical biosensors. Further, the current challenges are summarized and suggested future aspects. This review article is believed to shed some light on the development of MXene for biosensing and will open new opportunities for the future advanced translational application of MXene bioassays.

Novel electrochemical biosensor key significance of smart intelligence (IoMT & IoHT) of COVID-19 virus control management

Recent outbreak of COVID-19 pandemic has led to the different possibilities of the development of treatment against corona virus. To know the phylogenicity of SARS-CoV, various studies have been conducted with the outcome of the results showing virulence is caused due to spike protein. Various detection techniques with clinical approach like imaging technology, RT-PCR etc. are comparatively expensively than the use of biosensors. Nano-biosensors have an excellent way of approach to track the conditions of individual and public providing information about the existing condition and treatment status. Electrochemical nano-biosensors are referred as an excellent way of detection. The use of graphene based electrochemical nano-biosensors are most advantageous due to its elevated properties. Fluorescence investigation is one of the precise ways of sensing, optical biosignals that helps in obtaining real time results with high accuracy and negligible changes. The potential application of nano-biosensors are very wide, improvised and advanced Nanotechnology helps in the use of nano-biosensors detect all possible biosignals. Significant ubiquitous IoT-enabled novel sensor technologies that can be potentially utilized to respond various facets the growing COVID-19 pandemic from diagnostic and therapeutics to the prevention stage.

Dual-mode nanophotonic upconversion oxygen sensors

Nanophotonic biosensors capable of being excited in the NIR spectrum have applications in various sectors. Here, we develop a 980 nm-excitable nanophotonic sensor for real-time oxygen detection in both water and air by analyzing the photoluminescence lifetime and intensity using a nanocomposite of lanthanide-doped NaYF₄:Yb³⁺,Tm³⁺ upconversion nanoparticles and a PtTFPP platinum porphyrin complex in a polystyrene matrix. Excellent overlap between the emission of the upconversion nanoparticles and the excitation band of the PtTFPP guarantees 68% efficient excitation of the PtTFPP molecules with a 980 nm NIR laser. For the first time, the oxygen sensitivity of the upconversion nanoparticles alone was reported, and it was demonstrated that the PL lifetime-based sensitivity slope was boosted more than 10 times by adding PtTFPP oxygen-sensitive molecules due to the energy transfer from the upconversion nano-emitters. In addition, the functionality of the upconversion-based sensor was investigated by analyzing its sensitivity, stability, reversibility, and temperature-dependent lifetime in both water and air, and its performance was compared with that of the sensor exposed to direct excitation at 410 nm. More importantly, the sensor was implanted under the skin of a chicken, and it was demonstrated that the PL intensity was amplified more than 12 times by employing the 980 nm excitation laser instead of 410 nm laser light. Therefore, excellent emission of the sensor under the skin paves the way for the development of implantable oxygen sensor platforms.

Utilizing Electrochemical-Based Sensing Approaches for the Detection of SARS-CoV-2 in Clinical Samples: A Review

The development of precise and efficient diagnostic tools enables early treatment and proper isolation of infected individuals, hence limiting the spread of coronavirus disease 2019 (COVID-19). The standard diagnostic tests used by healthcare workers to diagnose severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection have some limitations, including longer detection time, the need for qualified individuals, and the use of sophisticated bench-top equipment, which limit their use for rapid SARS-CoV-2 assessment. Advances in sensor technology have renewed the interest in electrochemical biosensors miniaturization, which provide improved diagnostic qualities such as rapid response, simplicity of operation, portability, and readiness for on-site screening of infection. This review gives a condensed overview of the current electrochemical sensing platform strategies for SARS-CoV-2 detection in clinical samples. The fundamentals of fabricating electrochemical biosensors, such as the chosen electrode materials, electrochemical transducing techniques, and sensitive biorecognition molecules, are thoroughly discussed in this paper. Furthermore, we summarised electrochemical biosensors detection strategies and their analytical performance on diverse clinical samples, including saliva, blood, and nasopharyngeal swab. Finally, we address the employment of miniaturized electrochemical biosensors integrated with microfluidic technology in viral electrochemical biosensors, emphasizing its potential for on-site diagnostics applications.

Indiscriminate SARS-CoV-2 multivariant detection using magnetic nanoparticle-based electrochemical immunosensing

The increasing mutation frequency of the SARS-CoV-2 virus and the emergence of successive variants have made correct diagnosis hard to perform. Developing efficient and accurate methods to diagnose infected patients is crucial to effectively mitigate the pandemic. Here, we developed an electrochemical immunosensor based on SARS-CoV-2 antibody cocktail-conjugated magnetic nanoparticles for the sensitive and accurate detection of the SARS-CoV-2 virus and its variants in nasopharyngeal swabs. The application of the antibody cocktail was compared with commercially available anti-SARS-CoV-2 S1 (anti-S1) and anti-S2 monoclonal antibodies. After optimization and calibration, the limit of detection (LOD) determination demonstrated a LOD = 0.53–0.75 ng/mL for the antibody cocktail-based sensor compared with 0.93 ng/mL and 0.99 ng/mL for the platforms using anti-S1 and anti-S2, respectively. The platforms were tested with human nasopharyngeal swab samples pre-diagnosed with RT-PCR (10 negatives and 40 positive samples). The positive samples include the original, alpha, beta, and delta variants (n = 10, for each). The polyclonal antibody cocktail performed better than commercial anti-S1 and anti-S2 antibodies for all samples reaching 100% overall sensitivity, specificity, and accuracy. It also showed a wide range of variants detection compared to monoclonal antibody-based platforms. The present work proposes a versatile electrochemical biosensor for the indiscriminate detection of the different variants of SARS-CoV-2 using a polyclonal antibody cocktail. Such diagnostic tools allowing the detection of variants can be of great efficiency and economic value in the fight against the ever-changing SARS-CoV-2 virus.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Fluorescent bioassay for SARS-CoV-2 detection using polypyrene-g-poly(ε-caprolactone) prepared by simultaneous photoinduced step-growth and ring-opening polymerizations

The construction of a rapid and easy immunofluorescence bioassay for SARS-CoV-2 detection is described. We report for the first time a novel one-pot synthetic approach for simultaneous photoinduced step-growth polymerization of pyrene (Py) and ring-opening polymerization of ε-caprolactone (PCL) to produce a graft fluorescent copolymer PPy-g-PCL that was conjugated to SARS-CoV-2-specific antibodies using EDC/NHS chemistry. The synthesis steps and conjugation products were fully characterized using standard spectral analysis. Next, the PPy-g-PCL was used for the construction of a dot-blot assay which was calibrated for applications to human nasopharyngeal samples. The analytical features of the proposed sensor showed a detection range of 6.03–8.7 LOG viral copy mL⁻¹ (Ct Scores: 8–25), the limit of detection (LOD), and quantification (LOQ) of 1.84 and 6.16 LOG viral copy mL⁻¹, respectively. The repeatability and reproducibility of the platform had a coefficient of variation (CV) ranging between 1.2 and 5.9%. The fluorescence-based dot-blot assay was tested with human samples. Significant differences were observed between the fluorescence intensity of the negative and positive samples, with an overall correct response of 93.33%. The assay demonstrated a high correlation with RT-PCR data. This strategy opens new insights into simplified synthesis procedures of the reporter molecules and their high potential sensing and diagnosis applications.

Properties and Applications of Graphene and Its Derivatives in Biosensors for Cancer Detection: A Comprehensive Review

Cancer is one of the deadliest diseases worldwide, and there is a critical need for diagnostic platforms for applications in early cancer detection. The diagnosis of cancer can be made by identifying abnormal cell characteristics such as functional changes, a number of vital proteins in the body, abnormal genetic mutations and structural changes, and so on. Identifying biomarker candidates such as DNA, RNA, mRNA, aptamers, metabolomic biomolecules, enzymes, and proteins is one of the most important challenges. In order to eliminate such challenges, emerging biomarkers can be identified by designing a suitable biosensor. One of the most powerful technologies in development is biosensor technology based on nanostructures. Recently, graphene and its derivatives have been used for diverse diagnostic and therapeutic approaches. Graphene-based biosensors have exhibited significant performance with excellent sensitivity, selectivity, stability, and a wide detection range. In this review, the principle of technology, advances, and challenges in graphene-based biosensors such as field-effect transistors (FET), fluorescence sensors, SPR biosensors, and electrochemical biosensors to detect different cancer cells is systematically discussed. Additionally, we provide an outlook on the properties, applications, and challenges of graphene and its derivatives, such as Graphene Oxide (GO), Reduced Graphene Oxide (RGO), and Graphene Quantum Dots (GQDs), in early cancer detection by nanobiosensors.

Autonomous electrochemical biosensing of glial fibrillary acidic protein for point-of-care detection of central nervous system injuries

The integration of electrochemical biosensors into fluid handling units such as paper-based, centrifugal, and capillary microfluidic devices has been explored with the purpose of developing point-of-care platforms for quantitative detection of bodily fluid markers. However, the present fluidic device designs largely lack the capacity of full assay automation, needing manual loading of one or multiple reagents or requiring external devices for liquid manipulation. Such fluidic handing platforms also require universality for detecting various biomarkers. These platforms are also largely produced using materials unsuitable for scalable manufacturing and with a high production cost. The mechanism of fluid flow also often induces noise to the embedded biosensors which adversely impacts the accuracy of biosensing. This work addresses these challenges by presenting a reliable design of a fully automated and universal capillary-driven microfluidic platform that automates several steps of label-free electrochemical biosensing assays. These steps include sample aliquoting, controlled incubation, removal of non-specific bindings, reagent mixing and delivery to sensing electrodes, and electrochemical detection. The multilayer architecture of the microfluidic device is made of polymeric and adhesive materials commercially used for the fabrication of point-of-care devices. The design and geometry of different components of the device (e.g., sampling unit, mixer, resistances, delay valves, interconnecting components) were optimized using a combined experimental testing and numerical fluid flow modeling to reach high reproducibility and minimize the noise-induced to the biosensor. As a proof of concept, the performance of this on-chip immunosensing platform was demonstrated for rapid and autonomous detection of glial fibrillary acidic proteins (GFAP) in phosphate-buffered saline (PBS). The microfluidic immunosensing device exhibited a linear detection range of 10-1000 pg mL^-1 for the detection of GFAP within 30 min, with a limit of detection (LoD) and sensitivity of 3 pg mL^-1 and 39 mL pg^-1 mm^-2 in PBS, respectively. Owing to its simplicity, sample-to-result performance, universality for handing different biofluids, low cost, high reproducibility, compatibility with scalable production, and short analysis time, the proposed biosensing platform can be further adapted for the detection of other biomarkers in different clinical bodily fluids for rapid diagnostic and prognostic applications.