Chemiluminescence immunoassay for cardiac troponin T by using silver nanoparticles functionalized with hemin/G-quadruplex DNAzyme on a glass chip array

Clinical relevance and advances in detection of translational biomarker cardiac troponin

Cardiovascular diseases (CVD) are a range of diseases, pointing the functional hindrances in the heart and blood vessels of the human system that contributes to 48.6 % of the world's adult death rate. The diagnosis of CVD relies upon the Electro Cardio Gram (ECG) and detection of muscle markers such as troponins. Among the cardiac trio, Cardiac Troponin I (cTnI) weighing 23 KiloDalton (kDa) is a sorted biomarker for CVD. cTnI remains high in the blood after 1-2 weeks of myocardial damage. Testing of cTnI in CVD patients aids in diagnosis and risk stratification of the disease. Different determination systems including optical, electrochemical, and acoustic have been put forward for monitoring the cTnI which are Point of Care (POC) that promotes simple and sensitive detection of cTnI. The modern era has paved way to high-sensitivity Troponin I (hscTnI) devices that can detect up to 0.01 ng/ml in human blood/plasma/serum. Yet, the practice of hscTnI is impracticable due to cost inefficiency. Development of new hscTnI devices with minimal investment and maximal detection range will meet the global requirement. This review gives an over view on different detection systems of cardiac troponin I which stands as a translational detection molecule for CVDs.

DNAzyme-based ultrasensitive immunoassay: Recent advances and emerging trends

Immunoassay, as the most commonly used method for protein detection, is simple to operate and highly specific. Sensitivity improvement is always the thrust of immunoassays, especially for the detection of trace quantities. The emergence of artificial enzyme, i.e., DNAzyme, provides a novel approach to improve the detection sensitivity of immunoassay. Simultaneously, its advantages of simple synthesis and high stability enable low cost, broad applicability and long shelf life for immunoassay. In this review, we summarized the recent advances in DNAzyme-based immunoassay. First, we summarized the existing different DNAzymes based on their catalytic activities. Next, the common signal amplification strategies used for DNAzyme-based immunoassays were reviewed to cater to diverse detection requirements. Following, the wide applications in disease diagnosis, environmental monitoring and food safety were discussed. Finally, the current challenges and perspectives on the future development of DNAzyme-based immunoassays were also provided.

A highly selective optical sensor Eu-BINAM for assessment of high sensitivity cardiac troponin tumor marker in serum of cancer patients

A novel, easy, touchy and selective spectrofluorimetric technique has been successfully applied for sensitive determination of High Sensitivity Cardiac Troponin (TNHS I) in the serum samples of patients suffering malignant tumors through the usage of optical sensor Eu^3+-BINAM complex. The technique is primarily based on quenching of the Eu³⁺-BINAM complex's luminescence intensity upon introducing various concentrations of High Sensitivity Cardiac Troponin (TNHS I). The synthesis and characterization of the optical sensor was performed via absorption and emission. The sensor was also adapted to offer excitation at 394 nm in acetonitrile at pH 7.5. Concentration of High Sensitivity Cardiac Troponin (TNHS I) in serum samples was found to be proportional to the luminescence intensity quenching of the Eu³⁺-BINAM complex, most prominently at λ_em = 618 nm. The limit of the dynamic range is 4.26 × 10^-4 to 2 ng/mL. The limit of detection and quantitation were calculated to be 1.35 and 4.10 ng/mL, respectively. The suggested analytical approach proved its applicability, simplicity and comparatively interference- free. The technique was effectively recruited to quantify High Sensitivity Cardiac Troponin (TNHS I) in human serum samples. The proposed technique could be further extended to evaluate some biomarkers associated with malignancy related diseases in human.

Smartphone-based colorimetric detection of cardiac troponin T via label-free aptasensing

We report an aptasensing platform for the detection of cardiac troponin T (cTnT) in the immediate and early phases of acute myocardial infarction (AMI). High-flow filter paper was used to fabricate a microfluidic paper-based analytical device (μ-PAD), which was further modified with gold-decorated polystyrene microparticles functionalized with a highly specific cTnT aptamer. Herein, cTnT detection is presented in two linear ranges (0.01-0.8 μg/ml and 6.25-50 μg/ml) with an LoD of 3.9X10^-4 μg/ml, which is in agreement with reference values determined by the American Heart Association. The proposed platform showed remarkable selectivity against AMI-associated cardiac biomarkers such as TNF-alpha, interleukin-6, cardiac troponin I, and reactive protein-C. This aptasensor is a label-free assay that relies only on smartphone-based image analysis and takes less processing time in comparison with traditional methods like ELISA. Furthermore, it exhibits outstanding stability over 23 days when devices are stored at 4 °C. The reported platform is a stable and cost-effective method for the on-site and user-friendly detection of cTnT in normal saline buffer and diluted human serum.

Black Phosphorous Aptamer-based Platform for Biomarker Detection

Black phosphorus nanostructures (nano-BPs) mainly include BP nanosheets (BP NSs), BP quantum dots (BPQDs), and other nano-BPs-based particles at nanoscale. Firstly discovered in 2014, nano-BPs are one of the most popular nanomaterials. Different synthesis methods are discussed in short to understand the basic concepts and developments in synthesis. Exfoliated nano-BPs, i.e. nano-BPs possess high surface area, high photothermal conversion efficacy, excellent biocompatibility, high charge carrier mobility (~1000 cm^-2V^-1s^-1), thermal conductivity of 86 Wm^-1K^-1; and these properties make it a highly potential candidate for fabrication of biosensing platform. These properties enable nano-BPs to be promising photothermal/drug delivery agents as well as in electrochemical data storage devices and sensing devices; and in super capacitors, photodetectors, photovoltaics and solar cells, LEDs, super-conductors, etc. Early diagnosis is very critical in the health sector scenarios. This review attempts to highlight the attempts made towards attaining stable BP, BP-aptamer conjugates for successful biosensing applications. BP-aptamer- based platforms are reviewed to highlight the significance of BP in detecting biological and physiological markers of cardiovascular diseases and cancer; to be useful in disease diagnosis and management.

Biomedical and catalytic applications of agri-based biosynthesized silver nanoparticles

Nanotechnology has been recognized as the emerging field for the synthesis, designing, and manipulation of particle structure at the nanoscale. Its rapid development is also expected to revolutionize industries such as applied physics, mechanics, chemistry, and electronics engineering with suitably tailoring various nanomaterials. Inorganic nanoparticles such as silver nanoparticles (Ag-NPs) have garnered more interest with their diverse applications. In correspondence to green chemistry, researchers prioritize green synthetic techniques over conventional ones due to their eco-friendly and sustainable potential. Green-synthesized NPs have proven more beneficial than those synthesized by conventional methods because of capping by secondary metabolites. The present study reviews the various means being used by the researchers for the green synthesis of Ag-NPs. The morphological characteristics of these NPs as obtained from numerous characterization techniques have been explored. The potential applications of bio-synthesized Ag-NPs viz. Antimicrobial, antioxidant, catalytic, and water remediation along with the plausible mechanisms have been discussed. In addition, toxicity analysis and biomedical applications of these NPs have also been reviewed to provide a detailed overview. The study signifies that biosynthesized Ag-NPs can be efficiently used for various applications in the biomedical and industrial sectors as an environment-friendly and efficient tool.

Prefab Hollow Glass Microsphere-Based Immunosensor with Liquid Crystal Sensitization for Acute Myocardial Infarction Biomarker Detection

Quantitative detection of cardiac troponin biomarkers in blood is an important method for clinical diagnosis of acute myocardial infarction (AMI). In this work, a whispering gallery mode (WGM) microcavity immunosensor based on a prefab hollow glass microsphere (HGMS) with liquid crystal (LC) sensitization was proposed and experimentally demonstrated for label-free cardiac troponin I-C (cTnI-C) complex detection. The proposed fiber-optic immunosensor has a simple structure; the tiny modified HGMS serves as the key sensing element and the microsample reservoir simultaneously. A sensitive LC layer with cTnI-C recognition ability was deposited on the inner wall of the HGMS microcavity. The arrangement of LC molecules is affected by the cTnI-C antigen—antibody binding in the HGMS, and the small change of the surface refractive index caused by the binding can be amplified owing to the birefringence property of LC. Using the annular waveguide of the HGMS, the WGMs were easily excited by the coupling scanning laser with a microfiber, and an all-fiber cTnI-C immunosensor can be achieved by measuring the resonant wavelength shift of the WGM spectrum. Moreover, the dynamic processes of the cTnI-C antigen—antibody binding and unbinding was revealed by monitoring the wavelength shift continuously. The proposed immunosensor with a spherical microcavity can be a cost-effective tool for AMI diagnosis.

Inorganic nanoparticles coupled to nucleic acid enzymes as analytical signal amplification tools

Nucleic acid enzymes (NAzymes) are a class of nucleic acid molecules with catalytic activity, which can be modulated by the presence of different species such as metal ions, genetic biomarkers, small molecules or proteins, among others. NAzymes offer several important advantages for development of novel bioanalytical strategies, resulting from their functionality as specific recognition elements and as amplified analytical signal generators, making them ideal candidates for developing highly specific bioanalytical strategies for the detection of a wide variety of targets. When coupled with the exceptional features of inorganic nanoparticles (NPs), the sensitivity of the assays can be significantly improved, allowing the detection of targets using many different detection techniques including visual readout, spectrophotometry, fluorimetry, electrochemiluminescence, voltammetry, and single-particle inductively coupled plasma-mass spectrometry. Here we provide an overview of the fundamentals of novel strategies developed to achieve analytical signal amplification based on the use of NAzymes coupled with inorganic NPs. Some representative examples of such strategies for the highly sensitive detection of different targets will be presented, including metal ions, proteins, DNA- or RNA-based biomarkers, and small molecules or microorganisms. Furthermore, future prospective challenges will be discussed.

DNAzyme-Based Biosensors: Immobilization Strategies, Applications, and Future Prospective

Since their discovery almost three decades ago, DNAzymes have been used extensively in biosensing. Depending on the type of DNAzyme being used, these functional oligonucleotides can act as molecular recognition elements within biosensors, offering high specificity to their target analyte, or as reporters capable of transducing a detectable signal. Several parameters need to be considered when designing a DNAzyme-based biosensor. In particular, given that many of these biosensors immobilize DNAzymes onto a sensing surface, selecting an appropriate immobilization strategy is vital. Suboptimal immobilization can result in both DNAzyme detachment and poor accessibility toward the target, leading to low sensing accuracy and sensitivity. Various approaches have been employed for DNAzyme immobilization within biosensors, ranging from amine and thiol-based covalent attachment to non-covalent strategies involving biotin-streptavidin interactions, DNA hybridization, electrostatic interactions, and physical entrapment. While the properties of each strategy inform its applicability within a proposed sensor, the selection of an appropriate strategy is largely dependent on the desired application. This is especially true given the diverse use of DNAzyme-based biosensors for the detection of pathogens, metal ions, and clinical biomarkers. In an effort to make the development of such sensors easier to navigate, this paper provides a comprehensive review of existing immobilization strategies, with a focus on their respective advantages, drawbacks, and optimal conditions for use. Next, common applications of existing DNAzyme-based biosensors are discussed. Last, emerging and future trends in the development of DNAzyme-based biosensors are discussed, and gaps in existing research worthy of exploration are identified.

High-throughput immunosensor chip coupled with a fluorescent DNA dendrimer for ultrasensitive detection of cardiac troponin T

A novel fluorescence (FL) imaging platform was established for ultrasensitive and rapid detection of cardiac troponin T (cTnT), based on a high-throughput immunosensor chip and a DNA dendrimer capped with a large number of fluorescent dyes (FDD@Cy5). Through an enzyme-free and step-by-step strategy, FDD@Cy5 was self-assembled facilely. After the formation of a sandwich immunocomplex and biotin–streptavidin conjugation, FDD@Cy5 could be captured on the chip. FL signals emerged from Cy5 under external light and the enrichment of Cy5 on the dendrimer led to signal amplification. A FL image containing 90 spots could be collected instantaneously by laser confocal scanning microscopy and the brightness of all the spots corresponded to the concentrations of target cTnT. Under optimal conditions, the immunosensor chip coupled with FDD@Cy5 exhibited an excellent detection limit of 0.10 pg L⁻¹, a wide linear range from 0.20 pg L⁻¹ to 2.0 ng L⁻¹, a sample consumption down to 3.0 μL and a maximum throughput of 45 tests per h. The proposed approach was also applied to cTnT quantitation in serum samples with acceptable accuracy, providing a new avenue for early diagnosis and the prognosis evaluation of acute myocardial infarction.

A novel fluorescence imaging platform based on a high-throughput immunosensor chip and a DNA dendrimer capped with plenty of fluorescent dyes was proposed for ultrasensitive quantitation of cardiac troponin T.

Metal enhanced chemiluminescence nanosensor for ultrasensitive bioassay based on silver nanoparticles modified functional DNA dendrimer

A novel metal enhanced chemiluminescence (MEC) nanosensor was developed for ultrasensitive biosensing and imaging, based on functional DNA dendrimer (FDD), proximity-dependent DNAzyme and silver nanoparticles (AgNPs). The FDD containing two split G-quadruplex structures was prepared through an enzyme-free and step-by-step assembly strategy, and then reacted with AgNPs and hemin molecules to form the FDD/hemin/AgNPs facilely. Such a MEC nanosensor consisted of three modules: FDD (scaffold), the generated G-quadruplex/hemin DNAzyme (signal reporter) and AgNPs (chemiluminescence enhancer). The MEC effect was achieved by controlling the length of DNA sequences between AgNPs on the periphery of FDD and DNAzymes inside it. Such nanosensor exhibited 9-fold amplification and another 6.4-fold metal enhancement in chemiluminescence intensity, which can be easily applied into trace detection of multiple protein markers using a disposable protein immunoarray. The FDD/hemin/AgNPs-based multiplex MEC imaging assay showed wide linear ranges over 5 orders of magnitude and detection limits down to 5× 10^-5 ng L^-1 and 1.8 × 10^-4 U mL^-1 for cardiac troponin T and carcinoma antigen 125, demonstrating a promising potential in application to protein analysis and clinical diagnosis. Moreover, the MEC nanosensor can be effectively delivered into cells with excellent biocompatibility and outstanding stability, offering a new tool for detection of intracellular targets and suggesting wide applications in bioassay.

A review of biosensor technologies for blood biomarkers toward monitoring cardiovascular diseases at the point-of-care

Cardiovascular diseases (CVDs) cause significant mortality globally. Notably, CVDs disproportionately negatively impact underserved populations, such as those that are economically disadvantaged and often located in remote regions. Devices to measure cardiac biomarkers have traditionally been focused on large instruments in a central laboratory but the development of affordable, portable devices that measure multiple cardiac biomarkers at the point-of-care (POC) are needed to improve clinical outcomes for patients, especially in underserved populations. Considering the enormity of the global CVD problem, complexity of CVDs, and the large candidate pool of biomarkers, it is of great interest to evaluate and compare biomarker performance and identify potential multiplexed panels that can be used in combination with affordable and robust biosensors at the POC toward improved patient care. This review focuses on describing the known and emerging CVD biosensing technologies for analysis of cardiac biomarkers from blood. Initially, the global burden of CVDs and the standard of care for the primary CVD categories, namely heart failure (HF) and acute coronary syndrome (ACS) including myocardial infarction (MI) are discussed. The latest United States, Canadian and European society guidelines recommended standalone, emerging, and add-on cardiac biomarkers, as well as their combinations are then described for the prognosis, diagnosis, and risk stratification of CVDs. Finally, both commercial in vitro biosensing devices and recent state-of-art techniques for detection of cardiac biomarkers are reviewed that leverage single and multiplexed panels of cardiac biomarkers with a view toward affordable, compact devices with excellent performance for POC diagnosis and monitoring.

Water-soluble Hemin-mPEG-enhanced Luminol Chemiluminescence for Sensitive Detection of Hydrogen Peroxide and Glucose

In the present study, we synthesized a water-soluble substance (Hemin-mPEG) at room temperature by using hemin and poly(ethylene glycol) methyl ether (mPEG). It was found that the Hemin-mPEG maintained the excellent catalytic activity inherited from hemin, and was first used to catalyze a luminol-H₂O₂ chemiluminescence (CL) system to generate an intense and slow CL signal. The results of a mechanism research showed that the presence of Hemin-mPEG could promote the production of oxygen-relative radicals from H₂O₂ and dissolved oxygen in solution. Based on this mechanism, an ultra-sensitive, cheap and simply practical sensor for detecting glucose and H₂O₂ was developed. Under the most optimal experimental conditions, H₂O₂ and glucose detection results exhibited a good linear range from 0.002 to 3 μM and from 0.02 to 4 μM, respectively, and the detection limits were 1.8 and 10 nM, respectively. This approach has been successfully used to detect glucose in actual biological samples, and achieved good results.

An electrochemical troponin T aptasensor based on the use of a macroporous gold nanostructure

A specific troponin T (TnT) binding aptamer was identified and immobilized on an electrodeposited macroporous gold nanostructure using poly(ethylene glycol) 600, to fabricate a novel and ultrasensitive TnT aptasensor. The transducer surface on the gold disk electrode was characterized by field emission scanning electron microscopy, and immobilization of the aptamer was monitored by open circuit potential measurements. Binding of TnT by the aptamer was monitored by differential pulse voltammetry using ferro/ferricyanide as the redox probe. The aptamer has a high affinity and specificity, and the electrode is sensitive and selective. Best operated at a working potential of 0.23 V (vs. Ag/AgCl), the electrode can detected TnT in the 0.05 to 5.0 ng mL^-1 concentration range with a 23 pg mL^-1 detection limit. The method was applied to the determination of TnT in 99 spiked human serum samples, and the diagnostic sensitivity and specificity were 94 and 95%, respectively. Graphical abstract Schematic presentation of an electrochemical troponin T aptasensor. A macroporous gold nanostructure was electrodeposited followed by immobilization of a specific TnT aptamer. Binding of TnT by the aptamer was electrochemically monitored. MCH: mercaptohexanol; TnT: troponin T.

Ratiometric fluorescent immunoassay for the cardiac troponin-I using carbon dots and palladium-iridium nanocubes with peroxidase-mimicking activity

A nanozyme-linked immunosorbent assay is described for cardiac troponin I which is a biomarker for myocardial infarction. The method is based on the use of Pd-Ir nanocubes with excellent peroxidase-like activity. The nanocubes catalyze the oxidization of nonfluorescent o-phenylenediamine (OPD) by H₂O₂ to form a yellow fluorescent product (oxOPD) with excitation/emission maxima at 400/570 nm. Carbon dots are added as a reference fluorophore. Under the same excitation wavelength, they display blue fluorescence (450 nm). The ELISA uses the Pd-Ir nanocubes as a label for the secondary antibody and OPD as substrate. The ratio of fluorescence intensities at 570 and 450 nm increases in the 1 pg·mL^-1 to 1 ng·mL^-1 cardiac troponin I concentration range, and the detection limit is 0.31 pg·mL^-1. The method was applied to analyze spiked serum samples, and the results compared well with those obtained by a commercial chemiluminescence assay. Graphical abstract Schematic presentation of the ratiometric fluorescence immunoassay for cardiac troponin-I. Pd-Ir nanocubes were employed to fabricate nanozyme-based signal labels for its excellent peroxidase-mimicking activity.

Fluorescence immunoassay based on the enzyme cleaving ss-DNA to regulate the synthesis of histone-ds-poly(AT) templated copper nanoparticles

Herein, for the first time we report a novel competitive fluorescence immunoassay for the ultrasensitive detection of aflatoxin B1 (AFB1) using histone-ds-poly(AT) templated copper nanoparticles (His-pAT CuNPs) as the fluorescent indicator. In this immunoassay, glucose oxidase (Gox) was used as the carrier of the competing antigen to catalyze the formation of hydrogen peroxide (H2O2) from glucose. H2O2 was converted to a hydroxyl radical using Fenton's reagent, which further regulated the fluorescence signals of His-pAT CuNPs. Owing to the ultrahigh sensitivity of the ss-DNA to the hydroxyl radical, the proposed fluorescence immunoassay exhibited a favorable dynamic linear detection of AFB1 ranging from 0.46 pg mL-1 to 400 pg mL-1 with an good half maximal inhibitory concentration and limit of detection of 6.13 and 0.15 pg mL-1, respectively. The intra- and inter-assay showed that the average recoveries for AFB1 spiked corn samples ranged from 96.87% to 100.73% and 96.67% to 114.92%, respectively. The reliability of this method was further confirmed by adopting ultra-performance liquid chromatography coupled with the fluorescence detector method. In summary, this work offers a novel screening strategy with high sensitivity and robustness for the quantitative detection of mycotoxins or other pollutants for food safety and clinical diagnosis.

Highly Stable Conjugates of Carbon Nanoparticles with DNA Aptamers

Conjugates of carbon nanoparticles and aptamers have great potential in many areas of biomedicine. In order to be implemented in practice, such conjugates should keep their properties throughout long storage period in commonly available conditions. In this work, we prepared conjugates of carbon nanoparticles (CNP) with DNA aptamers using streptavidin-biotin reaction. Obtained conjugates possess superior stability and kept their physical-chemical and functional properties during 30 days at +4 °C and -20 °C. Proposed approach to conjugation allows loading of about 100-120 pM of biotinylated aptamer per 1 mg of streptavidin-coated CNP (CNP-Str). Aptamer-functionalized CNP-Str have zeta potential of -34 mV at pH 7, mean diameter of 168-177 nm, and polydispersity index of 0.080-0.140. High reproducibility of functionalization was confirmed by preparation of several batches of CNP-aptamer with the same size distribution and aptamer loading using independently synthesized parent CNP-Str nanoparticles. Stability of CNP-aptamer conjugates was significantly enhanced by postsynthesis addition of EDTA that prevents nuclease degradation of immobilized aptamers. Obtained nanoparticles were stable at pH ranging from 6 to 10. Optical properties of CNP-aptamer nanoparticles were also studied and their ability to quench fluorescence via Förster resonance energy transfer was shown. Taking into account properties of CNP-aptamer conjugates, we suppose they may be used in both homo- and heterogeneous colorimetric, fluorescent, and aggregation-based assays.

Exonuclease-assisted multicolor aptasensor for visual detection of ochratoxin A based on G-quadruplex-hemin DNAzyme-mediated etching of gold nanorod

An exonuclease-assisted multicolor aptasensor was developed for the visual detection of ochratoxin A (OTA). It is based on the etching of gold nanorods (AuNRs) mediated by a G-quadruplex-hemin DNAzyme. A DNA sequence (AG4-OTA) was designed that comprises a hemin aptamer and an OTA aptamer. OTA binds to AG4-OTA to form an antiparallel G-quadruplex, which halts its digestion by exonuclease I (Exo I) from the 3'-end of AG4-OTA. Thus, the retained hemin aptamer can bind to hemin to form a G-quadruplex-hemin DNAzyme. This DNAzyme has peroxidase-like activity that catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce its diimine derivative (TMB²⁺) in acidic solution. TMB²⁺ can etch the AuNRs by oxidizing Au(0) into Au(I). This results in the generation of rainbow-like colors and provides a multicolor platform for the visual detection of OTA. The assay is based on the use of a single isolated aptamer and possesses obvious advantages such as multi-color visual inspection, relatively high sensitivity and accuracy. It can be used to detect as little as 30 nM concentrations of OTA by visual observation and even 10 nM concentrations by spectrophotometry. The method was successfully applied to the determination of OTA in spiked beer where it gave recoveries of 101-108%, with a relative standard deviation (RSD, n = 5) of <5%. Graphical abstract Schematic of an exonuclease-assisted multicolor bioassay based on the G-quadruplex-hemin DNAzyme-mediated etching of gold nanorods (AuNRs). It enables visual detection of ochratoxin A (OTA) with a detection limit of 30 nM.

Biofunctionalized mesoporous silica nanospheres for the ultrasensitive chemiluminescence immunoassay of tumor markers

Mesoporous silica nanospheres (SiO₂) are synthesized and biofunctionalized for the development of an ultrasensitive chemiluminescent (CL) immunosensor for tumor markers.

Construction and Potential Applications of Biosensors for Proteins in Clinical Laboratory Diagnosis

Biosensors for proteins have shown attractive advantages compared to traditional techniques in clinical laboratory diagnosis. In virtue of modern fabrication modes and detection techniques, various immunosensing platforms have been reported on basis of the specific recognition between antigen-antibody pairs. In addition to profit from the development of nanotechnology and molecular biology, diverse fabrication and signal amplification strategies have been designed for detection of protein antigens, which has led to great achievements in fast quantitative and simultaneous testing with extremely high sensitivity and specificity. Besides antigens, determination of antibodies also possesses great significance for clinical laboratory diagnosis. In this review, we will categorize recent immunosensors for proteins by different detection techniques. The basic conception of detection techniques, sensing mechanisms, and the relevant signal amplification strategies are introduced. Since antibodies and antigens have an equal position to each other in immunosensing, all biosensing strategies for antigens can be extended to antibodies under appropriate optimizations. Biosensors for antibodies are summarized, focusing on potential applications in clinical laboratory diagnosis, such as a series of biomarkers for infectious diseases and autoimmune diseases, and an evaluation of vaccine immunity. The excellent performances of these biosensors provide a prospective space for future antibody-detection-based disease serodiagnosis.

Sensitive detection of cardiac troponin T based on superparamagnetic bead-labels using a flexible micro-fluxgate sensor

In this study, we describe an innovative micro-fluxgate immunosensor based on superparamagnetic Dynabeads for the detection of cardiac troponin T (cTnT), an important biomarker for cardiovascular diseases.