Microfluidic beads-based immunosensor for sensitive detection of cancer biomarker proteins using multienzyme-nanoparticle amplification and quantum dots labels

Revolutionizing biocatalysis: A review on innovative design and applications of enzyme-immobilized microfluidic devices

Integrating microfluidic devices and enzymatic processes in biocatalysis is a rapidly advancing field with promising applications. This review explores various facets, including applications, scalability, techno-commercial implications, and environmental consequences. Enzyme-embedded microfluidic devices offer advantages such as compact dimensions, rapid heat transfer, and minimal reagent consumption, especially in pharmaceutical optically pure compound synthesis. Addressing scalability challenges involves strategies for uniform flow distribution and consistent residence time. Incorporation with downstream processing and biocatalytic reactions makes the overall process environmentally friendly. The review navigates challenges related to reaction kinetics, cofactor recycling, and techno-commercial aspects, highlighting cost-effectiveness, safety enhancements, and reduced energy consumption. The potential for automation and commercial-grade infrastructure is discussed, considering initial investments and long-term savings. The incorporation of machine learning in enzyme-embedded microfluidic devices advocates a blend of experimental and in-silico methods for optimization. This comprehensive review examines the advancements and challenges associated with these devices, focusing on their integration with enzyme immobilization techniques, the optimization of process parameters, and the techno-commercial considerations crucial for their widespread implementation. Furthermore, this review offers novel insights into strategies for overcoming limitations such as design complexities, laminar flow challenges, enzyme loading optimization, catalyst fouling, and multi-enzyme immobilization, highlighting the potential for sustainable and efficient enzymatic processes in various industries.

Extending the Shelf-Life of Immunoassay-Based Microfluidic Chips through Freeze-Drying Sublimation Techniques

Point-of-care testing (POCT) platforms utilizing immunoassay-based microfluidic chips offer a robust and specific method for detecting target antibodies, demonstrating a wide range of applications in various medical and research settings. Despite their versatility and specificity, the adoption of these immunoassay chips in POCT has been limited by their short shelf-life in liquid environments, attributed to the degradation of immobilized antibodies. This technical limitation presents a barrier, particularly for resource-limited settings where long-term storage and functionality are critical. To address this challenge, we introduce a novel freeze-dry sublimation process aimed at extending the shelf-life of these microfluidic chips without compromising their functional integrity. This study elaborates on the mechanisms by which freeze-drying preserves the bioactivity of the immobilized antibodies, thereby maintaining the chip's performance over an extended period. Our findings reveal significant shelf-life extension, making it possible for these POCT platforms to be more widely adopted and practically applied, especially in settings with limited resources. This research paves the way for more accessible, long-lasting, and effective POCT solutions, breaking down previous barriers to adoption and application.

A micro-chamber free digital bio-detection for multiplexed and ultrasensitive immunoassay based on encoded magnetic microbeads and tyramide signal amplification strategy

Digital bio-detection has become one of the most appealing methods in recent years due to its excellent performance with ultra-sensitivity in detection of low-abundance targets. Traditional digital bio-detection needs the utilization of micro-chambers for physical isolation of targets, while the recently developed beads-based micro-chamber free one is attracting extensive attention, although there exist the disadvantages of overlaps between positive ("1") and negative ("0") signals as well as the decreased detection sensitivity in multiplexed mode. Here we propose a feasible and robust micro-chamber free digital bio-detection for multiplexed and ultrasensitive immunoassay based on encoded magnetic microbeads (EMMs) and tyramide signal amplification (TSA) strategy. An EMMs-based multiplexed platform is constructed by using a fluorescent encoding method, then a puissant signal amplification of positive events in TSA procedure is achieved via systematical revelation of key factors influences. For proof of concept, a three-plexed tumor markers detection is performed to evaluate our established platform. The detection sensitivity is comparable to the corresponding single-plexed assays and is also approximately 30-15,000 times improvement compared to the conventional suspension chip. Therefore, this multiplexed micro-chamber free digital bio-detection paves a promising way to be an ultrasensitive and powerful tool for clinical diagnosis.

Recent advances in nanotechnology-enhanced biosensors for α-fetoprotein detection

α-Fetoprotein (AFP) is a kind of fetal protein that is related to tumor, the increasing concentration of which gives birth to a large variety of diseases, such as liver cancer. Therefore, the detection method with super sensitivity, high selectivity, and less time consumption under trace concentrations in early stage of diseases is becoming a necessity. In recent years, nanomaterials have been regarded as significant resources for the exploration of efficient biosensors with high sensitivity, selectivity, speed, as well as simple process, due to their excellent optical, electrical, and chemical properties. In this paper, we reviewed the research progress of AFP biosensors with enhanced sensitivity and selectivity by nanoparticles. Representative examples have also been displayed in this paper to expound the nanotechnologies utilized in the early detection of AFP. Furthermore, challenges of the clinical application of AFP biosensors based on nanotechnology have been elaborated, as well as the development opportunity in this field in the future. This review provides a comprehensive overview on the various nano-biosensor for AFP detection based on functional nanotechnology.

Nanomaterial-assisted microfluidics for multiplex assays

Simultaneous detection of different biomarkers from a single specimen in a single test, allowing more rapid, efficient, and low-cost analysis, is of great significance for accurate diagnosis of disease and efficient monitoring of therapy. Recently, developments in microfabrication and nanotechnology have advanced the integration of nanomaterials in microfluidic devices toward multiplex assays of biomarkers, combining both the advantages of microfluidics and the unique properties of nanomaterials. In this review, we focus on the state of the art in multiplexed detection of biomarkers based on nanomaterial-assisted microfluidics. Following an overview of the typical microfluidic analytical techniques and the most commonly used nanomaterials for biochemistry analysis, we highlight in detail the nanomaterial-assisted microfluidic strategies for different biomarkers. These highly integrated platforms with minimum sample consumption, high sensitivity and specificity, low detection limit, enhanced signals, and reduced detection time have been extensively applied in various domains and show great potential in future point-of-care testing and clinical diagnostics.

Nanoscale dynamic chemical, biological sensor material designs for control monitoring and early detection of advanced diseases

Early detection and easy continuous monitoring of emerging or re-emerging infectious, contagious or other diseases are of particular interest for controlling healthcare advances and developing effective medical treatments to reduce the high global cost burden of diseases in the backdrop of lack of awareness regarding advancing diseases. Under an ever-increasing demand for biosensor design reliability for early stage recognition of infectious agents or contagious diseases and potential proteins, nanoscale manufacturing designs had developed effective nanodynamic sensing assays and compact wearable devices. Dynamic developments of biosensor technology are also vital to detect and monitor advanced diseases, such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), diabetes, cancers, liver diseases, cardiovascular diseases (CVDs), tuberculosis, and central nervous system (CNS) disorders. In particular, nanoscale biosensor designs have indispensable contribution to improvement of health concerns by early detection of disease, monitoring ecological and therapeutic agents, and maintaining high safety level in food and cosmetics. This review reports an overview of biosensor designs and their feasibility for early investigation, detection, and quantitative determination of many advanced diseases. Biosensor strategies are highlighted to demonstrate the influence of nanocompact and lightweight designs on accurate analyses and inexpensive sensing assays. To date, the effective and foremost developments in various nanodynamic designs associated with simple analytical facilities and procedures remain challenging. Given the wide evolution of biosensor market requirements and the growing demand in the creation of early stage and real-time monitoring assays, precise output signals, and easy-to-wear and self-regulating analyses of diseases, innovations in biosensor designs based on novel fabrication of nanostructured platforms with active surface functionalities would produce ​remarkable biosensor devices. This review offers evidence for researchers and inventors to focus on biosensor challenge and improve fabrication of nanobiosensors to revolutionize consumer and healthcare markets.

Finding the perfect match between nanoparticles and microfluidics to respond to cancer challenges

The clinical translation of new cancer theranostic has been delayed by inherent cancer's heterogeneity. Additionally, this delay has been enhanced by the lack of an appropriate in vitro model, capable to produce accurate data. Nanoparticles and microfluidic devices have been used to obtain new and more efficient strategies to tackle cancer challenges. On one hand, nanoparticles-based therapeutics can be modified to target specific cells, and/or molecules, and/or modified with drugs, releasing them over time. On the other hand, microfluidic devices allow the exhibition of physiologically complex systems, incorporation of controlled flow, and control of the chemical environment. Herein, we review the use of nanoparticles and microfluidic devices to address different cancer challenges, such as detection of CTCs and biomarkers, point-of-care devices for early diagnosis and improvement of therapies. The future perspectives of cancer challenges are also addressed herein.

Progress in research on gold nanoparticles in cancer management

INTRODUCTION

The rapid advancement of nanotechnology in recent years has fuelled burgeoning interest in the field of nanoparticle research, particularly its application in cancer management. At present, there seems to be heightened interest in the application of gold nanoparticles (AuNPs) to the management of cancer, encompassing diagnosis, monitoring, and treatment. AuNPs could be used as drug delivery agents that target cancer cells or in gene therapy. These efforts are undertaken in the hope of revolutionizing current methods and strategies for cancer treatment. This review will focus on the current applications of AuNPs in cancer management. OBJECTIVES, DATA SOURCES, STUDY APPRAISAL AND SYNTHESIS METHODS, RESULTS:: objectives, data sources, study eligibility criteria, participants, and interventions, study appraisal and synthesis methods, results are not required, as the study will be a literature review. Just introduction, ethics and dissemination, and conclusion are applicable.

ETHICS AND DISSEMINATION

Ethical approval and informed consent are not required, as the study is a literature review and does not involve direct contact with patients or alterations to patient care.

CONCLUSION

AuNPs have many properties that are of great value for the diagnosis and treatment of tumors. AuNPs are small in size and can penetrate widely and deposit on the tumor site, bind to many proteins and drugs, target delivery drugs, and have good biocompatibility. The application of AuNPs in the diagnosis and treatment of tumors is very considerable. In the near future, AuNPs will certainly play an important role in the treatment of tumors.

Computational Design of a Functionalized Substrate for Capturing Nanoparticles with Specific Size and Shape

The efficient capture of nanoscopic particulates plays a key role in many scientific fields like filtration and fabrication of nanocomposites as well as biosensors. In this work, we design two types of nanosubstrates to capture the nanoparticle with specific property by using Brownian dynamics simulations. It is found that the substrate coated with copolymers (composed of nonspecific block and specific block) can be used to capture the nanoparticle with different sizes but its capture efficiency of nanoparticles with different shapes is very low. To overcome such problem, the other substrate containing shaped holes is also designed. By conducting a serial of control simulations, we find that the nonspecific polymers at the bottom and on the rim of the hole have great impact on the sensitive capture. The present study may provide some physical insights into the experimental design of nanodevices in real applications.

Functional Diagnostic and Therapeutic Nanoconstructs for Efficient Probing of Circulating Tumor Cells

The circulation of tumor cells in peripheral blood is mostly recognized as a prerequisite for cancer progression or systemic invasion, and it correlates with the pivotal hallmark of malignancies known as metastasis. Multiple detection schemes for circulating tumor cells (CTCs) have emerged as the most discerning criteria for monitoring the outcome of anticancer therapy. Therefore, there has been a tremendous increase in the use of robust nanostructured platforms for observation of these mobile tumor cells through various simultaneous diagnosis and treatment regimens developed from conventional techniques. This review seeks to give detailed information about the nature of CTCs as well as techniques for exploiting specific biomarkers to help monitor cancer via detection, capturing, and analysis of unstable tumor cells. We will further discuss nanobased diagnostic interventions and novel platforms which have recently been developed from versatile nanomaterials such as polymer nanocomposites, metal organic frameworks, bioderived nanomaterials and other physically responsive particles with desirable intrinsic and external properties. Herein, we will also include in vivo nanotheranostic platforms which have received a lot of attention because of their enormous clinical potential. In all, this review sums up the general potential of key promising nanoinspired systems as well as other advanced strategies under research and those in clinical use.

Cellphone-Enabled Microwell-Based Microbead Aggregation Assay for Portable Biomarker Detection

Quantitative biomarker detection methods featured with rapidity, high accuracy, and label-free are demonstrated for the development of point-of-care (POC) technologies or "beside" diagnostics. Microbead aggregation via protein-specific linkage provides an effective approach for selective capture of biomarkers from the samples, and can directly readout the presence and amount of the targets. However, sensors or microfluidic analyzers that can accurately quantify the microbead aggregation are scared. In this work, we demonstrate a microwell-based microbeads analyzing system, by which online manipulations of microbeads including trapping, arraying, and rotations can be realized, providing a series of microfluidic approaches to layout the aggregated microbeads for further convenient characterizations. Prostate specific antigen is detected using the proposed system, demonstrating the limit of detection as low as 0.125 ng/mL (3.67 pM). A two-step reaction kinetics model is proposed for the first time to explain the dynamic process of microbeads aggregation. The developed microbeads aggregation analysis system has the advantages of label-free detection, high throughput, and low cost, showing great potential for portable biomarker detection.

Integrated electrokinetically driven microfluidic devices with pH-mediated solid-phase extraction coupled to microchip electrophoresis for preterm birth biomarkers

Integration in microfluidics is important for achieving automation. Sample preconcentration integrated with separation in a microfluidic setup can have a substantial impact on rapid analysis of low-abundance disease biomarkers. Here, we have developed a microfluidic device that uses pH-mediated solid-phase extraction (SPE) for the enrichment and elution of preterm birth (PTB) biomarkers. Furthermore, this SPE module was integrated with microchip electrophoresis for combined enrichment and separation of multiple analytes, including a PTB peptide biomarker (P1). A reversed-phase octyl methacrylate monolith was polymerized as the SPE medium in polyethylene glycol diacrylate modified cyclic olefin copolymer microfluidic channels. Eluent for pH-mediated SPE of PTB biomarkers on the monolith was optimized using different pH values and ionic concentrations. Nearly 50-fold enrichment was observed in single channel SPE devices for a low nanomolar solution of P1, with great elution time reproducibility (<7% RSD). The monolith binding capacity was determined to be 400 pg (0.2 pmol). A mixture of a model peptide (FA) and a PTB biomarker (P1) was extracted, eluted, injected, and then separated by microchip electrophoresis in our integrated device with ∼15-fold enrichment. This device shows important progress towards an integrated electrokinetically operated platform for preconcentration and separation of biomarkers.

Recent Advances in Electrochemical Immunosensors

Immunosensors have experienced a very significant growth in recent years, driven by the need for fast, sensitive, portable and easy-to-use devices to detect biomarkers for clinical diagnosis or to monitor organic pollutants in natural or industrial environments. Advances in the field of signal amplification using enzymatic reactions, nanomaterials such as carbon nanotubes, graphene and graphene derivatives, metallic nanoparticles (gold, silver, various oxides or metal complexes), or magnetic beads show how it is possible to improve collection, binding or transduction performances and reach the requirements for realistic clinical diagnostic or environmental control. This review presents these most recent advances; it focuses first on classical electrode substrates, then moves to carbon-based nanostructured ones including carbon nanotubes, graphene and other carbon materials, metal or metal-oxide nanoparticles, magnetic nanoparticles, dendrimers and, to finish, explore the use of ionic liquids. Analytical performances are systematically covered and compared, depending on the detection principle, but also from a chronological perspective, from 2012 to 2016 and early 2017.

Single cell biology beyond the era of antibodies: relevance, challenges, and promises in biomedical research

Research of the past two decades has proved the relevance of single cell biology in basic research and translational medicine. Successful detection and isolation of specific subsets is the key to understand their functional heterogeneity. Antibodies are conventionally used for this purpose, but their relevance in certain contexts is limited. In this review, we discuss some of these contexts, posing bottle neck for different fields of biology including biomedical research. With the advancement of chemistry, several methods have been introduced to overcome these problems. Even though microfluidics and microraft array are newer techniques exploited for single cell biology, fluorescence-activated cell sorting (FACS) remains the gold standard technique for isolation of cells for many biomedical applications, like stem cell therapy. Here, we present a comprehensive and comparative account of some of the probes that are useful in FACS. Further, we illustrate how these techniques could be applied in biomedical research. It is postulated that intracellular molecular markers like nucleostemin (GNL3), alkaline phosphatase (ALPL) and HIRA can be used for improving the outcome of cardiac as well as bone regeneration. Another field that could utilize intracellular markers is diagnostics, and we propose the use of specific peptide nucleic acid probes (PNPs) against certain miRNAs for cancer surgical margin prediction. The newer techniques for single cell biology, based on intracellular molecules, will immensely enhance the repertoire of possible markers for the isolation of cell types useful in biomedical research.

Ultrasensitive Label-free Electrochemical Immunosensor based on Multifunctionalized Graphene Nanocomposites for the Detection of Alpha Fetoprotein

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP). Multifunctionalized graphene nanocomposites (TB-Au-Fe₃O₄-rGO) were applied to modify the electrode to achieve the amplification of electrochemical signal. TB-Au-Fe₃O₄-rGO includes the advantages of graphene, ferroferric oxide nanoparticles (Fe₃O₄ NPs), gold nanoparticles (Au NPs) and toluidine blue (TB). As a kind of redox probe, TB can produce the electrochemical signal. Graphene owns large specific surface area, high electrical conductivity and good adsorption property to load a large number of TB. Fe₃O₄ NPs have good electrocatalytic performance towards the redox of TB. Au NPs have good biocompatibility to capture the antibodies. Due to the good electrochemical performance of TB-Au-Fe₃O₄-rGO, the effective and sensitive detection of AFP was achieved by the designed electrochemical immunosensor. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 1.0 × 10⁻⁵ ng/mL to 10.0 ng/mL with a low detection limit of 2.7 fg/mL for AFP. It also displayed good electrochemical performance including good reproducibility, selectivity and stability, which would provide potential applications in the clinical diagnosis of other tumor markers.

Recent Progress in Electrochemical Biosensors for Glycoproteins

This review provides an overview of recent progress in the development of electrochemical biosensors for glycoproteins. Electrochemical glycoprotein sensors are constructed by combining metal and carbon electrodes with glycoprotein-selective binding elements including antibodies, lectin, phenylboronic acid and molecularly imprinted polymers. A recent trend in the preparation of glycoprotein sensors is the successful use of nanomaterials such as graphene, carbon nanotube, and metal nanoparticles. These nanomaterials are extremely useful for improving the sensitivity of glycoprotein sensors. This review focuses mainly on the protocols for the preparation of glycoprotein sensors and the materials used. Recent improvements in glycoprotein sensors are discussed by grouping the sensors into several categories based on the materials used as recognition elements.

Critical overview on the application of sensors and biosensors for clinical analysis

Sensors and biosensors have been increasingly used for clinical analysis due to their miniaturization and portability, allowing the construction of diagnostic devices for point-of-care testing. This paper presents an up-to-date overview and comparison of the analytical performance of sensors and biosensors recently used in clinical analysis. This includes cancer and cardiac biomarkers, hormones, biomolecules, neurotransmitters, bacteria, virus and cancer cells, along with related significant advances since 2011. Some methods of enhancing the analytical performance of sensors and biosensors through their figures of merit are also discussed.

On-Chip Fluorescent Labeling using Reversed-phase Monoliths and Microchip Electrophoretic Separations of Selected Preterm Birth Biomarkers

On-chip preconcentration, purification, and fluorescent labeling are desirable sample preparation steps to achieve complete automation in integrated microfluidic systems. In this work, we developed electrokinetically operated microfluidic devices for solid-phase extraction and fluorescent labeling of preterm birth (PTB) biomarkers. Reversed-phase monoliths based on different acrylate monomers were photopolymerized in cyclic olefin copolymer microdevices and studied for the selective retention and elution of a fluorescent dye and PTB biomarkers. Octyl methacrylate-based monoliths with desirable retention and elution characteristics were chosen and used for on-chip fluorescent labeling of three PTB biomarkers. Purification of on-chip labeled samples was done by selective elution of unreacted dye prior to sample. Automated and rapid on-chip fluorescent labeling was achieved with similar efficiency to that obtained for samples labeled off chip. Additionally, protocols for microchip electrophoresis of several off-chip-labeled PTB biomarkers were demonstrated in poly(methyl methacrylate) microfluidic devices. This study is an important step toward the development of integrated on-chip labeling and separation microfluidic devices for PTB biomarkers.

Microbead QD-ELISA: Microbead ELISA Using Biocatalytic Formation of Quantum Dots for Ultra High Sensitive Optical and Electrochemical Detection

Electrochemical detection strategies employing semiconductor quantum dots (QDs) open up new opportunities for highly sensitive detection of biological targets. We designed a new assay based on microbead linked enzymatic generation of CdS QDs (Microbead QD-ELISA) and employed it in optical and electrochemical affinity assays for the cancer biomarker superoxide dismutase 2 (SOD2). Biotinylated antibodies against SOD2 were immobilized on the surface of polyvinyl chloride microbeads bearing streptavidin. In order to prevent any non-specific adsorption the microbeads were further blocked with bovine serum albumin. The analyte, SOD2 was captured on microbeads and labeled with alkaline phosphatase-conjugated antibody linked with mouse antibody against SOD2. Hydrolysis of para-nitrophenylphosphate by immobilized alkaline phosphatase triggered the rapid formation of phosphate-stabilized CdS QDs on the surface of microbeads. The resulting semiconductor nanoparticles were detected by fluorescence spectroscopy, microscopy, and square-wave voltammetry (SWV). The electrochemical assay based on the detection with square-wave voltammograms of Cd²⁺ ions originating from immobilized CdS QDs showed linearity up to 45 ng mL^-1, and the limit of SOD2 detection equal to 0.44 ng mL^-1 (1.96 × 10^-11 M). This detection limit is lower by 2 orders of magnitude in comparison with that of other previously published assays for superoxide dismutase. The electrochemical assay was validated with HepG2 (Human hepatocellular carcinoma) cell lysate containing SOD2.

Extended-gate field-effect transistor packed in micro channel for glucose, urea and protein biomarker detection

This study developed a packaging method to integrate the extended-gate field-effect transistor (EGFET) into a microfluidic chip as a biological sensor. In addition, we present two immobilization approaches for the bio-recognition that are appropriate to this chip, allowing it to measure the concentrations of hydrogen ions, glucose, urea, and specific proteins in a solution. Alginate-calcium microcubes were used to embed the enzymes and magnetic powder (enzyme carrier). When the sensing chip needs the enzyme for the catalytic reaction, the alginate microcubes containing the corresponding enzymes enter through the flow channel and are immobilized on the EGFET surface with an external magnet. High sensing performance of the chip is achieved, with 37.45 mV/mM for measuring hydrogen ions at pH 6-8 with a linearity of 0.9939, 7.00 mV/mM for measuring glucose with a linearity of 0.9962, and 8.01 mV/mM for measuring urea with a linearity of 0.9809. In addition, based on the principle of the immunoassay, the magnetic beads with the specific antibody were used to capture the target protein in the sample. Then, negatively charged DNA fragments bound to a secondary antibody were used to amplify the signal for EGFET measurement. The magnetic beads with completed immune response bonding were then fixed on the surface of the sensor by an external magnetic field. Therefore, the measured object can directly contact the sensor surface, and quantitative detection of the protein concentration can be achieved. Apolipoprotein A1 (APOA1) was detected as a target protein, with a minimum detection limit of approximately 12.5 ng/mL.

Quantum dot as probe for disease diagnosis and monitoring

Semiconductor quantum dots (QD) possess unique optical and electric properties like size-tunable light emission, narrow emission range, high brightness and photostability. Recent research advances have minimized the toxicity of QDs and they are successfully used in in vitro and in vivo imaging. Encapsulation of QDs into polymeric nanoparticles and linking them with targeting ligands enabled the detection of tumors and cancer cells in vivo. QD-antibody conjugates were successfully used in monitoring and diagnosis of HIV and myocardial infarction. Application of near infrared (NIR) QDs was found to minimize the absorption and scattering of light by native tissues thus rendering them suitable in deep tissue analysis. Aggregation and endosomal sequestration of QDs pose major challenges for the effective delivery of QDs to the cell cytosol. Toxicity minimization and effective delivery strategies may further increase their suitability for utilization in disease diagnosis. New synthesis of QDs may provide new types of bioconjugates of QDs to biomolecules, which leads to a variety of applications to many challenged research areas. QDs with narrow emission wavelength ranges are very suitable for monitoring multiple cellular targets simultaneously, and still remain the best known probes for imaging as an alternative to traditional fluorophores in disease diagnosis.

Biomarker detection for disease diagnosis using cost-effective microfluidic platforms

Early and timely detection of disease biomarkers can prevent the spread of infectious diseases, and drastically decrease the death rate of people suffering from different diseases such as cancer and infectious diseases. Because conventional diagnostic methods have limited application in low-resource settings due to the use of bulky and expensive instrumentation, simple and low-cost point-of-care diagnostic devices for timely and early biomarker diagnosis is the need of the hour, especially in rural areas and developing nations. The microfluidics technology possesses remarkable features for simple, low-cost, and rapid disease diagnosis. There have been significant advances in the development of microfluidic platforms for biomarker detection of diseases. This article reviews recent advances in biomarker detection using cost-effective microfluidic devices for disease diagnosis, with the emphasis on infectious disease and cancer diagnosis in low-resource settings. This review first introduces different microfluidic platforms (e.g. polymer and paper-based microfluidics) used for disease diagnosis, with a brief description of their common fabrication techniques. Then, it highlights various detection strategies for disease biomarker detection using microfluidic platforms, including colorimetric, fluorescence, chemiluminescence, electrochemiluminescence (ECL), and electrochemical detection. Finally, it discusses the current limitations of microfluidic devices for disease biomarker detection and future prospects.

Lab on a chip for multiplexed immunoassays to detect bladder cancer using multifunctional dielectrophoretic manipulations

A multiplexed immunosensor has been developed for the detection of specific biomarkers Galectin-1 (Gal-1) and Lactate Dehydrogenase B (LDH-B) present in different grades of bladder cancer cell lysates. In order to immobilize nanoprobes with different antibodies on a single chip we employed three-step programmable dielectrophoretic manipulations for focusing, guiding and trapping to enhance the fluorescent response and reduce the interference between the two antibody arrays. The chip consisted of a patterned indium tin oxide (ITO) electrode for sensing and a middle fish bone shaped gold electrode for focusing and guiding. Using ITO electrodes for the sensing area can effectively eliminate the background noise of fluorescence response as compared to metal electrodes. It was also observed that the three step manipulation increased fluorescence response after immunosensing by about 4.6 times as compared to utilizing DEP for just trapping the nanoprobes. Two different-grade bladder cancer cell lysates (grade I: RT4 and grade III: T24) were individually analyzed for detecting the protein expression levels of Gal-1 and LDH-B. The fluorescence intensity observed for Gal-1 is higher than that of LDH-B in the T24 cell lysate; however the response observed in RT4 is higher for LDH-B as compared to Gal-1. Thus we can effectively identify the different grades of bladder cancer cells. In addition, the platform for DEP manipulation developed in this study can enable real time detection of multiple analytes on a single chip and provide more practical benefits for clinical diagnosis.

Glycan-based diagnostic devices: current progress, challenges and perspectives

The development of glycan-based diagnostic devices is illustrated with recent examples from both carbohydrate recognition and device design aspects.

Biosensors for the detection of circulating tumour cells

Metastasis is the cause of most cancer deaths. Circulating tumour cells (CTCs) are cells released from the primary tumour into the bloodstream that are considered the main promoters of metastasis. Therefore, these cells are targets for understanding tumour biology and improving clinical management of the disease. Several techniques have emerged in recent years to isolate, detect, and characterise CTCs. As CTCs are a rare event, their study requires multidisciplinary considerations of both biological and physical properties. In addition, as isolation of viable cells may give further insights into metastatic development, cell recovery must be done with minimal cell damage. The ideal system for CTCs analysis must include maximum efficiency of detection in real time. In this sense, new approaches used to enrich CTCs from clinical samples have provided an important improvement in cell recovery. However, this progress should be accompanied by more efficient strategies of cell quantification. A range of biosensor platforms are being introduced into the technology for CTCs quantification with promising results. This review provides an update on recent progress in CTCs identification using different approaches based on sensor signaling.

Ultrasensitive non-mediator electrochemical immunosensors using Au/Ag/Au core/double shell nanoparticles as enzyme-mimetic labels

Determination of squamous cell carcinoma antigen (SCCA) in human serum plays an important role in diagnosis of cervical squamous cell carcinoma. In this work, Au/Ag/Au core/double shell nanoparticles (Au/Ag/Au NPs) were prepared by a simple approach and were used as novel enzyme-mimetic labels for development of a sandwich-type electrochemical immunosensor for SCCA. The nanostructure of Au/Ag/Au NPs could be well confirmed by transmission electron microscope (TEM) and UV-vis spectra. Au NPs decorated mercapto-functionalized graphene sheets (Au@SH-GS) were used as platform for immobilization of primary antibody (Ab1), while Au/Ag/Au NPs were employed as labels of secondary antibody (Ab2). Due to the excellent electrocatalytic activity of Au/Ag/Au NPs towards the reduction of hydrogen peroxide (H2O2), electrochemical amperometric responses to SCCA were achieved after the immuno-reaction. Under optimum conditions, the electrochemical immunosensor exhibited a wide linear range from 0.5 pg/mL to 40 ng/mL with a low detection limit of 0.18 pg/mL for SCCA. The designed immunosensor displayed an excellent analytical performance with good reproducibility, high selectivity and stability.