The LOD paradox: When lower isn't always better in biosensor research and development

Biosensor research has long focused on achieving the lowest possible Limits of Detection (LOD), driving significant advances in sensitivity and opening up new possibilities in analysis. However, this intense focus on low LODs may not always meet the practical needs or suit the actual uses of these devices. While technological improvements are impressive, they can sometimes overlook important factors such as detection range, ease of use, and market readiness, which are vital for biosensors to be effective in real-world applications. This review advocates for a balanced approach to biosensor development, emphasizing the need to align technological advancements with practical utility. We delve into various applications, including the detection of cancer biomarkers, pathology-related biomarkers, and illicit drugs, illustrating the critical role of LOD within these contexts. By considering clinical needs and broader design aspects like cost-effectiveness, sustainability, and regulatory compliance, we argue that integrating technical progress with practicality will enhance the impact of biosensors. Such an approach ensures that biosensors are not only technically sound but also widely useable and beneficial in real-world applications. Addressing the diverse analytical parameters alongside user expectations and market demands will likely maximize the real-world impact of biosensors.

Electrochemical microfluidic sensing platforms for biosecurity analysis

Biosecurity encompasses the health and safety of humans, animals, plants, and the environment. In this article, "biosecurity" is defined as encompassing the comprehensive aspects of human, animal, plant, and environmental safety. Reliable biosecurity testing technology is the key point for effectively assessing biosecurity risks and ensuring biosecurity. Therefore, it is crucial to develop excellent detection technologies to detect risk factors that can affect biosecurity. An electrochemical microfluidic biosensing platform integrates fluid control, target recognition, signal transduction, and output and incorporates the advantages of electrochemical analysis technology and microfluidic technology. Thus, an electrochemical microfluidic biosensing platform, characterized by exceptional analytical sensitivity, portability, rapid analysis speed, low reagent consumption, and low risk of contamination, shows considerable promise for biosecurity detection compared to traditional, more complex, and time-consuming detection technologies. This review provides a concise introduction to electrochemical microfluidic biosensors and biosecurity. It highlights recent research advances in utilizing electrochemical microfluidic biosensing platforms to assess biosecurity risk factors. It includes the use of electrochemical microfluidic biosensors for the detection of risk factors directly endangering biosecurity (direct application: namely, risk factors directly endangering the health of human, animals, and plants) and for the detection of risk factors indirectly endangering biosecurity (indirect application: namely, risk factors endangering the safety of food and the environment). Finally, we outline the current challenges and future perspectives of electrochemical microfluidic biosensing platforms.

Microfluidic-based cardiovascular systems for advanced study of atherosclerosis

Atherosclerosis (AS) is a significant global health concern due to its high morbidity and mortality rates. Extensive efforts have been made to replicate the cardiovascular system and explore the pathogenesis, diagnosis, and treatment of AS. Microfluidics has emerged as a valuable technology for modeling the cardiovascular system and studying AS. Here a brief review of the advances of microfluidic-based cardiovascular systems for AS research is presented. The critical pathogenetic mechanisms of AS investigated by microfluidic-based cardiovascular systems are categorized and reviewed, with a detailed summary of accurate diagnostic methods for detecting biomarkers using microfluidics represented. Furthermore, the review covers the evaluation and screening of AS drugs assisted by microfluidic systems, along with the fabrication of novel drug delivery carriers. Finally, the challenges and future prospects for advancing microfluidic-based cardiovascular systems in AS research are discussed and proposed, particularly regarding new opportunities in multi-disciplinary fundamental research and therapeutic applications for a broader range of disease treatments.

Electrochemical and Plasmonic Detection of Myocardial Infarction Using Microfluidic Biochip Incorporated with Mesoporous Nanoscaffolds

This paper reports a microfluidic device for the electrochemical and plasmonic detection of cardiac myoglobin (cMb) and cardiac troponin I (cTnI) with noticeable limits of detection (LoD) as low as a few picograms per milliliter (pg/mL) ranges, achieved in a short detection time. The device features two working electrodes, each with a mesoporous Ni3V2O8 nanoscaffold grafted with reduced graphene oxide (rGO) that improves the interaction of diffusing analyte molecules with the sensing surface by providing a high surface area and reaction kinetics. Electrochemical studies reveal sensitivities as high as 9.68 μA ng/mL and a LoD of 2.0 pg/mL for cTnI, and 8.98 μA ng/mL and 4.7 pg/mL for cMb. Additionally, the surface plasmon resonance (SPR) studies demonstrate a low-level LoD of 8.8 pg/mL for cMb and 7.3 pg/mL for cTnI. The dual-modality sensor enables dynamic tracking of kinetic antigen-antibody interactions during sensing, self-verification through providing signals of two modes, and reduced false readout. This study demonstrates the complementary nature of the electrochemical and SPR modes in biosensing, with the electrochemical mode being highly sensitive and the SPR mode providing superior tracking of molecular recognition behaviors. The presented sensor represents a significant innovation in cardiovascular disease management and can be applied to monitor other clinically important biomolecules.

Ultrasensitive protein and exosome analysis based on a rolling circle amplification assisted-CRISPR/Cas12a strategy

CRISPR/Cas12a system has attracted extensive concern in biosensing due to its high specificity and programmability. Nevertheless, existing Cas12a-based assays mainly focus on nucleic acid detection and have limitations in non-nucleic acid biomarker analysis. To broaden the application prospect of the CRISPR/Cas technology, a cascade Cas12a biosensing platform is reported by combining dual-functionalized gold nanoparticles (FGNPs)-assisted rolling circle amplification (RCA) and Cas12a trans-cleavage activity (GAR-Cas) for ultrasensitive protein and exosome analysis. FGNPs serve as a critical component in the transduction of protein or exosome recognition information into nucleic acid amplification events to produce Cas12a activators. In the GAR-Cas assay, by integrating the triple cascade amplification of FGNPs-assisted transduction, RCA, and Cas12a signal amplification, ultralow abundance of target molecules can arouse numerous concatemers to activate Cas12a trans-cleavage activity to release intense fluorescence, allowing the ultrasensitive detection of as low as 1 fg/mL (∼41 aM) cTnI and 5 exosomes per μL. Furthermore, the presented strategy can be applied to detect exosome levels from clinical samples, showing excellent performance in distinguishing cancer patients from healthy individuals. The GAR-Cas sensing platform exhibits great potential in clinical diagnosis and enlarges biosensing toolboxes based on CRISPR/Cas technology for non-nucleic acid target analysis.

Surface plasmon resonance biosensor chips integrated with MoS2-MoO3 hybrid microflowers for rapid CFP-10 tuberculosis detection

This study reports on the modification of surface plasmon resonance (SPR) chips with molybdenum disulfide-molybdenum trioxide (MoS2-MoO3) microflowers to detect the tuberculosis (TB) markers of CFP-10. The MoS2-MoO3 microflowers were prepared by hydrothermal methods with variations in the pH and amount of trisodium citrate (Na3Ct), which were projected to influence the shape and size of microflower particles. The analysis shows that optimum MoS2-MoO3 hybrid microflowers were obtained at neutral pH using 0.5 g Na3Ct. The modified SPR biosensor exhibits a ten times higher response than the bare Au. Moreover, increasing MoS2-MoO3 thickness results in a higher detection response, sensitivity, and a smaller limit of detection (LOD). Using the optimized material composition, the Au/MoS2-MoO3-integrated SPR sensor can demonstrate sensitivity and LOD of 1.005 and 3.45 ng mL-1, respectively. This biosensor also has good selectivity, stability, and reproducibility based on cross-sensitivity characterization with other analytes and repeated measurements on several chips with different storing times and fabrication batch. Therefore, this proposed SPR biosensor possesses high potential to be further developed and applied as a detection technology for CFP-10 in monitoring and diagnosing TB.

Performance analysis of three distinct NixV2Oy single-phase nano self-assemblies for asymmetric supercapacitor fabrication and effective detection of low-concentration hazardous herbicide

Single-phase inorganic nanostructures with multiple applications are required for cost-effective, sustainable applications to save the environment from toxic activities. Nickel vanadate (NixV2Oy), possessing three phases, such as NiV2O6, Ni2V2O7, and Ni3V2O8, acts as an effective electrode material and potential electrochemical sensors. Nickel vanadate phases (NiV2O6, Ni2V2O7, and Ni3V2O8) were synthesized through the gel-matrix technique, and their phase purity, crystallinity, morphology, optical properties, etc., were evaluated and studied. Electrochemical studies infer that NiV2O6 exhibits the highest specific capacity of 251 C g-1 (69.7 mA h g-1) at 1 A g-1 compared to the other nickel vanadate phases and provides better cyclic stability of 80.19% for 5000 cycles. The asymmetric supercapacitor device fabricated from NiV2O6 results in a specific capacity of 189 C g-1 (52.5 mA h g-1), energy density of 59.06 W h kg-1, and a power density of 1125 W kg-1 with a capacitive retention rate of 74.91% and coulombic efficiency of 99.61% for 10 000 cycles. The electrochemical detection potential of NixV2Oy in bifenox herbicide has been studied with all the synthesized nanostructures. Among them, NiV2O6-based sensor probes demonstrated excellent characteristics, including high sensing current and low detection limits of 0.6 nM with a linear range of 1-57 nM. The real-time herbicide detection of NiV2O6 in live samples was checked with freshly harvested potatoes. This advancement further enhances the utilization of NixV2Oy materials for electrochemical applications.

Construction of a desirable hyperbolic microfluidic chip for ultrasensitive determination of PCT based on chemiluminescence

Since procalcitonin (PCT) is a specific inflammation indicator of severe bacterial inflammation and fungal infection, it is of great significance to construct a sensitive and rapid microfluidic chip to detect PCT in clinical application. The design of micromixers using a lab-on-a-chip (LOC) device is the premise to realizing the adequate mixing of analytical samples and reagents and is an important measure to improve the accuracy and efficiency of determination. In this research study, we investigate the mixing characteristics of hyperbolic micromixers and explore the effects of different hyperbolic curvatures, different Reynolds numbers (Re) and different channel widths on the mixing performance of the micromixers. Then, an optimal micromixer was integrated into a microfluidic chip to fabricate a desirable hyperbolic microfluidic chip (DHMC) for the sensitive determination of inflammation marker PCT with a limit of detection (LOD) as low as 0.17 ng mL^-1via a chemiluminescence signal, which can be used as a promising real-time platform for early clinical diagnosis.

Direct fabrication of NbS2 nanoflakes on carbon fibers by atomic layer deposition for ultrasensitive cardiac troponin I detection

The sensitive detection of cardiac troponin I (cTnI) is of great significance for the early diagnosis of acute myocardial infarction (AMI). Herein, in order to fabricate an electrochemical biosensor for ultrasensitive cTnI detection, atomic layer deposition (ALD) was employed to directly deposit NbS₂ nanoflakes (NFs) on carbon fiber paper (CFP). Due to the self-limiting reaction of ALD, NbS₂NFs were deposited uniformly and accurately on the surface of carbon fibers by controlling the number of ALD cycles, which ensured ultrasensitive detection. Precise regulation of the nanoscale morphology and electrochemical performance of NbS₂ nanoflakes via ALD cycles was observed in depth. Owing to the high surface area and conductivity, an anodic/cathodic current of ∼3.01 mA of NbS₂NFs/CFP can be obtained. Subsequently, an electrochemical biosensor based on the excellent performance of NbS₂NFs/CFP was fabricated. The ultrasensitive detection of cTnI in a linear range of 1 fM to 0.1 nM with a detection limit of 0.32 fM was achieved.

Template Free Anisotropically Grown Gold Nanocluster Based Electrochemical Immunosensor for Ultralow Detection of Cardiac Troponin I

Anisotropic gold nanostructures have fascinated with their exceptional electronic properties, henceforth exploited for the fabrication of electrochemical sensors. However, their synthesis approaches are tedious and often require a growth template. Modern lifestyle has caused an upsurge in the risk of heart attack and requires urgent medical attention. Cardiac troponin I can serve as a biomarker in identification of suspected myocardial infection (heart attack). Hence the present work demonstrates the fabrication of a sensing platform developed by assimilating anisotropic gold nanoclusters (AuNCs) with anti cTnI antibody (acTnI) for the detection of cardiac troponin I (cTnI). The uniqueness and ease of synthesis by a template-free approach provides an extra edge for the fabrication of AuNC coated electrodes. The template-free growth of anisotropic AuNCs onto the indium tin oxide (ITO) glass substrates offers high sensitivity (2.2 × 10-4 A ng-1 mL cm-2) to the developed sensor. The immunosensor was validated by spiking different concentrations of cTnI in artificial serum with negligible interference under optimized conditions. The sensor shows a wide range of detection from 0.06-100 ng/mL with an ultralow detection limit. Thus, it suggests that the template-free immunosensor can potentially be used to screen the traces of cTnI present in blood serum samples, and the AuNCs based platform holds great promise as a transduction matrix, hence it can be exploited for broader sensing applications.

Nanotechnology for cardiovascular diseases

Cardiovascular diseases have become the major killers in today's world, among which coronary artery diseases (CADs) make the greatest contributions to morbidity and mortality. Although state-of-the-art technologies have increased our knowledge of the cardiovascular system, the current diagnosis and treatment modalities for CADs still have limitations. As an emerging cross-disciplinary approach, nanotechnology has shown great potential for clinical use. In this review, recent advances in nanotechnology in the diagnosis of CADs will first be elucidated. Both the sensitivity and specificity of biosensors for biomarker detection and molecular imaging strategies, such as magnetic resonance imaging, optical imaging, nuclear scintigraphy, and multimodal imaging strategies, have been greatly increased with the assistance of nanomaterials. Second, various nanomaterials, such as liposomes, polymers (PLGA), inorganic nanoparticles (AuNPs, MnO2, etc.), natural nanoparticles (HDL, HA), and biomimetic nanoparticles (cell-membrane coating) will be discussed as engineered as drug (chemicals, proteins, peptides, and nucleic acids) carriers targeting pathological sites based on their optimal physicochemical properties and surface modification potential. Finally, some of these nanomaterials themselves are regarded as pharmaceuticals for the treatment of atherosclerosis because of their intrinsic antioxidative/anti-inflammatory and photoelectric/photothermal characteristics in a complex plaque microenvironment. In summary, novel nanotechnology-based research in the process of clinical transformation could continue to expand the horizon of nanoscale technologies in the diagnosis and therapy of CADs in the foreseeable future.

Significance of Cardiac Troponins as an Identification Tool in COVID-19 Patients Using Biosensors: An Update

Coronavirus disease 2019 (COVID-19) has rapidly developed as a global health emergency. Respiratory diseases are significant causes of morbidity and mortality in these patients with a spectrum of different diseases, from asymptomatic subclinical infection to the progression of severe pneumonia and subsequent acute respiratory distress syndrome. Individuals with cardiovascular disease are more likely to become infected with SARS-CoV-2 and develop severe symptoms. Hence, patients with underlying cardiovascular disease mortality rate are over three times. Furthermore, note that patients with a history of cardiovascular disease are more likely to have higher cardiac biomarkers, especially cardiac troponins, than infected patients, especially those with severe disease, making these patients more susceptible to cardiac damage caused by SARS-2-CoV. Biomarkers are important in decision-making to facilitate the efficient allocation of resources. Viral replication in the heart muscle can lead to a cascade of inflammatory processes that lead to fibrosis and, ultimately, cardiac necrosis. Elevated troponin may indicate damage to the heart muscle and may predict death. After the first Chinese analysis, increased cardiac troponin value was observed in a significant proportion of patients, suggesting that myocardial damage is a possible pathogenic mechanism leading to severe disease and death. However, the prognostic performance of troponin and whether its value is affected by different comorbidities present in COVID-19 patients are not known. This review aimed to assess the diagnostic value of troponin to offer insight into pathophysiological mechanisms and reported new assessment methods, including new biosensors for troponin in patients with COVID-19.

Integrating potential-resolved electrochemiluminescence with molecularly imprinting immunoassay for simultaneous detection of dual acute myocardial infarction markers

A novel potential-resolved molecularly imprinted electrochemical luminescence (ECL) immunosensor has been developed for the first time for the dual sensitive detection of markers of acute myocardial infarction (AMI): cardiac troponin I (cTnI) and myoglobin (Mb). In this work, cost-effective and robust molecularly imprinted polymer (MIP) as biomimetic antibody was used to construct the immunosensors through electropolymerization and elution to form polydopamine (PDA)-MIP modified electrode. In the presence of AMI biomarkers, two ECL probes including Ru(bpy)₃²⁺@ MOCs and MoS₂ QDs functionalized by cTnI antibody and Mb aptamer could be specifically captured respectively. And two potential distinct ECL signals will be generated in one potential scan. The intensity of ECL reflects the concentrations of cTnI and Mb. The two ECL probes were characterized with field emission scanning electron microscopy, X-ray diffraction, FT-IR spectrum and UV-Vis diffuse reflectance spectroscopy. The prepared sensor exhibited a wide linear range (0.05-10⁴ ng/mL) and a low detection limit (0.0184 ng/mL for cTnI and 0.0492 ng/mL for Mb). Additionally, the MIP-ECL sensor displayed excellent anti-interference, sensitivity and stability to detect cTnI and Mb. Therefore, it will be conducive to accelerate more precise and credible early diagnosis for AMI.

A dual-signal electrochemiluminescence immunosensor for high-sensitivity detection of acute myocardial infarction biomarker

Based on two different types of luminescence systems (Ru﹡(bpy)₃²⁺/TPA and SnO₂ NFs/K₂S₂O₈), a new type of electrochemiluminescence (ECL) immunosensor was prepared, which realized the detection of acute myocardial infarction biomarker cTnI. In this strategy, Ru(bpy)₃²⁺, above all, was immobilized on the NH₂-MIL-125 as a capture probe. Subsequently, cTnI and SnO₂ NFs was bonded to the electrode surface through the interaction between antigen and antibody in turn. During this process, Ru(bpy)₃²⁺ and the co-reactant TPA first showed strong and stable ECL emission. As the concentration of cTnI in the test system increased, the signal of SnO₂ NFs and the co-reactant K₂S₂O₈ gradually enhanced, indicating self-calibrating mechanism of the assay system. Therefore, the "off-on" ECL immunosensor can be detected in the linear range of 10^-5 -10⁴ ng/mL, and the limit of detection (LOD) is 3.39 fg/mL (S/N = 3), respectively. The dual-signal electrochemiluminescence method has the advantages of low cost, simple analysis process, wide detection range and good selectivity, providing a promising analysis protocol for clinical applications.

ZnSe nanodisks:Ti3C2 MXenes-modified electrode for nucleic acid liquid biopsy with photoelectrochemical strategy

ZnSe nanodisks:Ti₃C₂ MXene complex was prepared for the first time. Based on its remarkable photoelectrochemical performance, combined with the enzyme-free toehold-mediated strand displacement reaction, a photoelectrochemical biosensor for the detection of the non-small-cell cancer biomarker ctDNA KRAS G12D was developed. ZnSe nanodisks were in situ grown on Ti₃C₂ MXene surface by two-step hydrothermal method. The high conductivity and adjustable band gap of MXene significantly enhanced the photoelectric response of ZnSe. Subsequently, the photoelectrochemical biosensor was prepared by combining with the signal amplification function of p-aminophenol and the enzyme-free toehold-mediated strand displacement reaction on the modified ITO electrode surface. Under the optimized conditions, the linear detection range is 0.5 ~ 100.0 fM, and the detection limit is 0.2 fM, which realizes the sensitive detection of KRAS G12D. The photoelectrochemical biosensor constructed opens up a new pathway for the preparation of new Mxene-based composite materials and the research of photoelectrochemical biosensor. Nucleic acid liquid biopsy with ZnSe nanodisks:Ti₃C₂ MXene photoelectroactive modified electrode.

Troponin I as a Biomarker for Early Detection of Acute Myocardial Infarction

Acute myocardial infarction (AMI) as the main cause of death among cardiovascular diseases is defined as a deficiency of oxygen that generates irreversible tissue necrosis in the heart muscle. For diagnostic measurements, the evaluation of cardiac markers concentration like cardiac triponin I (cTnI) in plasma or saliva thought the use of biosensors has become one of the most commonly applied strategies for prognosis of AMI. Inside this diagnostic devices, electrochemical (ECL) ones have been highly encourage to improve sensing capabilities by using different materials and configurations. In this review, the authors presents a summary of studies that involves cTnI detection using ECL biosensors modified with nanomaterials and related mechanisms.

Microfluidics-Based Sensing of Biospecies

Over the past decades, microfluidic devices based on many advanced techniques have aroused widespread attention in the fields of chemical, biological, and analytical applications. Integration of microdevices with a variety of chip designs will facilitate promising functionality. Notably, the combination of microfluidics with functional nanomaterials may provide creative ideas to achieve rapid and sensitive detection of various biospecies. In this review, focused on the microfluids and microdevices in terms of their fabrication, integration, and functions, we summarize the up-to-date developments in microfluidics-based analysis of biospecies, where biomarkers, small molecules, cells, and pathogens as representative biospecies have been explored in-depth. The promising applications of microfluidic biosensors including clinical diagnosis, food safety control, and environmental monitoring are also discussed. This review aims to highlight the importance of microfluidics-based biosensors in achieving high throughput, highly sensitive, and low-cost analysis and to promote microfluidics toward a wider range of applications.

Enzyme-Free Electrochemical Nano-Immunosensor Based on Graphene Quantum Dots and Gold Nanoparticles for Cardiac Biomarker Determination

An ultrasensitive enzyme-free electrochemical nano-immunosensor based on a screen-printed gold electrode (SPGE) modified with graphene quantum dots (GQDs) and gold nanoparticles (AuNPs) was engineered to detect cardiac troponin-I (cTnI) for the early diagnosis of acute myocardial infarction (AMI). The GQDs and in-house synthesized AuNPs were implanted onto the SPGE and allowed for anti-cTnI immobilization prior to quantifying cTnI. The biomarker could be determined in a wide concentration range using square-wave voltammetry (SWV), cyclic voltammetry (CV), electron impedance spectroscopy (EIS) and amperometry. The analyses were performed in buffer, as well as in human serum, in the investigation ranges of 1–1000 and 10–1000 pg mL⁻¹, respectively. The detection time ranged from 10.5–13 min, depending on the electrochemical method employed. The detection limit was calculated as 0.1 and 0.5 pg mL⁻¹ for buffer and serum, respectively. The sensitivity of the immunosensor was found to be 6.81 µA cm⁻² pg mL⁻¹, whereas the binding affinity was determined to be <0.89 pM. The sensor showed high specificity for cTnI with slight responses for nonspecific biomolecules. Each step of the sensor fabrication was characterized using CV, SWV, EIS and atomic force microscopy (AFM). Moreover, AuNPs, GQDs and their nanocomposites were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This is the first immunosensor that represents the successful determination of an analyte using four different electrochemical techniques. Such a sensor could demonstrate a promising future for on-site detection of AMI with its sensitivity, cost-effectiveness, rapidity and specificity.

Nanotechnology-assisted microfluidic systems: from bench to bedside

With significant advancements in research technologies, and an increasing global population, microfluidic and nanofluidic systems (such as point-of-care, lab-on-a-chip, organ-on-a-chip, etc) have started to revolutionize medicine. Devices that combine micron and nanotechnologies have increased sensitivity, precision and versatility for numerous medical applications. However, while there has been extensive research on microfluidic and nanofluidic systems, very few have experienced wide-spread commercialization which is puzzling and deserves our collective attention. For the above reasons, in this article, we review research advances that combine micro and nanotechnologies to create the next generation of nanomaterial-based microfluidic systems, the latest in their commercialization success and failure and highlight the value of these devices both in industry and in the laboratory.

A microfluidic cathodic photoelectrochemical biosensor chip for the targeted detection of cytokeratin 19 fragments 21-1

A microfluidic chip integrated with a microelectrode and a cathodic photoelectrochemical (PEC) biosensor for the ultrasensitive detection of non-small cell lung cancer cytokeratin fragments based on a signal amplification strategy was designed. The mechanism for signal amplification is developed based on the p-n junction of AgI/Bi₂Ga₄O₉, with dissolved O₂ as an electron acceptor to produce the superoxide anion radical (˙O₂^-) as the working microelectrode. By combining this with a novel superoxide-dismutase-loaded honeycomb manganese oxide nanostructure (SOD@hMnO₂) as the co-catalyst signal amplification label, ˙O₂^- can be catalyzed by SOD via a disproportionation reaction to produce O₂ and H₂O₂; then, hMnO₂ is able to trigger the decomposition of H₂O₂ to generate O₂ and H₂O. Therefore, the increased O₂ promotes the separation of electron-hole pairs via consuming more electrons, leading to an effective enhancement of the cathodic PEC behavior. Under optimum conditions, with the cytokeratin 19 fragments 21-1 (CYFRA 21-1) as the targeted detection objects, the microfluidic cathodic PEC biosensor chip exhibited excellent linearity from 0.1 pg mL^-1 to 100 ng mL^-1, with a detection limit of 0.026 pg mL^-1 (S/N = 3). The exciting thing that this work offers is a new strategy for the detection of other important cancer biomarkers for disease diagnosis and prognosis.

Gold Nanoparticle-Based Platforms for Diagnosis and Treatment of Myocardial Infarction

In recent years, an increasing rate of mortality due to myocardial infarction (MI) has led to the development of nanobased platforms, especially gold nanoparticles (AuNPs), as promising nanomaterials for diagnosis and treatment of MI. These promising NPs have been used to develop different nanobiosensors, mainly optical sensors for early detection of biomarkers as well as biomimetic/bioinspired platforms for cardiac tissue engineering (CTE). Therefore, in this Review, we presented an overview on the potential application of AuNPs as optical (surface plasmon resonance, colorimetric, fluorescence, and chemiluminescence) nanobiosensors for early diagnosis and prognosis of MI. On the other hand, we discussed the potential application of AuNPs either alone or with other NPs/polymers as promising three-dimensional (3D) scaffolds to regulate the microenvironment and mimic the morphological and electrical features of cardiac cells for potential application in CTE. Furthermore, we presented the challenges and ongoing efforts associated with the application of AuNPs in the diagnosis and treatment of MI. In conclusion, this Review may provide outstanding information regarding the development of AuNP-based technology as a promising platform for current MI treatment approaches.

Bimodal size distribution immuno-quantum dots for fluorescent western blotting assay with high sensitivity and extended dynamic range

A highly sensitive quantum dot (QD)-based western blot assay with extended dynamic range was developed. Bimodal size distribution QD (BQ) immunoprobes composed of small size single QD (7.3 nm) and big size QD nanobead (QB) (82.9 nm) were employed for fluorescent western blot immunoassay on a membrane. Small size QD immunoprobes contributed to wider dynamic range of assay, while big size QB immunoprobes provided higher detection sensitivity. This BQ-based western blot assay can achieve a wide dynamic range (from 7.8 to 4000 ng IgG) and is nearly as sensitive as commercial available ultrasensitive chemiluminescent methods, just using a simple gel imager with UV light (365 nm) excitation and red light filter (610 nm). The fluorescent signals of BQ western blot were stable for 10 min, while chemiluminescent signals faded after 1 min. Moreover, this BQ immunoprobe was utilized for the detection of housekeeping protein and specific target proteins in complex cell lysate samples. The limit of detection of housekeeping protein is 0.25 μg of cell lysate, and the signal intensities were proportional to loading protein amount in a wide range from 0.61 to 80 μg. We believe that this new strategy of bimodal size distribution nanoparticles can also be expanded for other functional nanoparticle-based biological assays to improve the sensitivity and extend the dynamic range. Graphical abstract.

Nanoscale Technologies in Highly Sensitive Diagnosis of Cardiovascular Diseases

Cardiovascular diseases (CVD) are the leading cause of death and morbidity in the world and are a major contributor to healthcare costs. Although enormous progress has been made in diagnosing CVD, there is an urgent need for more efficient early detection and the development of novel diagnostic tools. Currently, CVD diagnosis relies primarily on clinical symptoms based on molecular imaging (MOI) or biomarkers associated with CVDs. However, sensitivity, specificity, and accuracy of the assay are still challenging for early-stage CVDs. Nanomaterial platform has been identified as a promising candidate for improving the practical usage of diagnostic tools because of their unique physicochemical properties. In this review article, we introduced cardiac biomarkers and imaging techniques that are currently used for CVD diagnosis. We presented the applications of various nanotechnologies on diagnosis within cardiac immunoassays (CIAs) and molecular imaging. We also summarized and compared different cardiac immunoassays based on their sensitivities and working ranges of biomarkers.

Emerging Trends in Microfluidics Based Devices

One of the major challenges for scientists and engineers today is to develop technologies for the improvement of human health in both developed and developing countries. However, the need for cost-effective, high-performance diagnostic techniques is very crucial for providing accessible, affordable, and high-quality healthcare devices. In this context, microfluidic-based devices (MFDs) offer powerful platforms for automation and integration of complex tasks onto a single chip. The distinct advantage of MFDs lies in precise control of the sample quantities and flow rate of samples and reagents that enable quantification and detection of analytes with high resolution and sensitivity. With these excellent properties, microfluidics (MFs) have been used for various applications in healthcare, along with other biological and medical areas. This review focuses on the emerging demands of MFs in different fields such as biomedical diagnostics, environmental analysis, food and agriculture research, etc., in the last three or so years. It also aims to reveal new opportunities in these areas and future prospects of commercial MFDs.

Dual-modality microfluidic biosensor based on nanoengineered mesoporous graphene hydrogels

A dual-modality microfluidic biosensor is fabricated using a mesoporous nanostructured cysteine-graphene hydrogel for the quantification of human cardiac myoglobin (cMb). In this device, the nanoengineered mesoporous l-cysteine-graphene (Cys-RGO) hydrogel performs the role of a dual-modality sensing electrode for the measurements conducted using differential pulse voltammetry and surface plasmon resonance (SPR) techniques. High surface reactivity, mesoporous structure and fast electron transfer combined with good reaction kinetics of the graphene hydrogel in this device indicate excellent performance for the detection of human cardiac myoglobin in serum samples. In electrochemical modality, this microfluidic chip exhibits a high sensitivity of 196.66 μA ng^-1 mL cm^-2 for a linear range of concentrations (0.004-1000 ng mL^-1) with a low limit of detection (LOD) of 4 pg mL^-1 while the SPR technique shows a LOD of 10 pg mL^-1 for cMb monitoring in the range 0.01-1000 ng mL^-1. The intra-assay coefficient of variation was less than 8% for standard samples and 9% for real serum samples, respectively. This Cys-RGO hydrogel-based microfluidic SPR chip allows real-time dynamic tracking of cMb molecules with a high association constant of 4.93 ± 0.2 × 10⁵ M^-1 s^-1 and a dissociation constant of 1.37 ± 0.08 × 10^-4 s^-1, self-verification, reduced false readout, and improved detection reliability.