Bimetallic Single-Atom Nanozyme-Based Electrochemical-Photothermal Dual-Function Portable Immunoassay with Smartphone Imaging

Biosensing of single-nucleotide polymorphism: Technological advances and their transformative applications on health

Single nucleotide polymorphisms (SNPs) are important genetic changes related to many diseases such as breast cancer, Alzheimer's disease, and β-thalassemia. Because of the increased interest in biosensor technologies, there has been a notable surge in the creation of new techniques to identify these changes in recent years. These new methods are highly accurate and sensitive, cost-effective and fast, making them ideal for use in clinical analysis. The non-invasive nature of biosensing techniques further enhances their integration into clinical protocols and point-of-care diagnostics. Several electrochemical, optical, and mass-based biosensors are carefully examined in this extensive review; each is distinguished by unique sensing platforms and techniques. This review presents in-depth discussions of linear dynamic ranges, detection limits, and real-world applications of contemporary research in the diagnosis of biological substrate disorders.

Harnessing bifunctional nanozyme with potent catalytic and signal amplification for innovating electrochemical immunoassay

Nanozyme-based electrochemical biosensors have emerged as an alternative to enzyme-based biosensors for next-generation bioanalysis. However, potential antibody modifications limit the catalytic sites of the nanozyme, thereby reducing sensor sensitivity. Here, a sensitive method for determining carcinoembryonic antigen (CEA) was developed. It involved coupling a cascade enzyme - enzyme - like catalytic reaction using Fe - Co Prussian blue analog nanozymes with high peroxidase - like activity (79.42 U mg-1). Briefly, the transduction of biological signals to chemical signals was achieved through the strategy centered on catalytic electroactive probes. Thereafter, with the assistance of the microelectrochemical workstation, the output of signals was realized. The platform exhibited an ultra-wide range of 0.020-100 ng mL-1 and a detection limit of 0.013 ng mL-1 CEA, which was mainly attributed to the excellent peroxidase activity, good conductivity, and synergistic amplification of current signals of synthesized nanozymes. In addition, the modification-free features greatly reduced the complexity of the bioassay and significantly improves its portability and cost-effectiveness. Overall, this study advances the development of nanozymes and their electrochemical biosensing applications and is expected to extend to the development of miniaturized devices in direct detection environments.

Advanced cortisol detection: A cMWCNTs-enhanced MB@Zr-MOF ratiometric electrochemical aptasensor

A ratiometric electrochemical aptasensor was developed for ultra-sensitive detection of cortisol using aptamer (Apt) as recognition element, methylene blue (MB) as signal probe, and zirconium metal-organic framework (Zr-MOF) as carrier loaded with abundant MB for signal amplification. The carboxylated multi-walled carbon nanotubes (cMWCNTs)-modified Au electrode showed excellent electrochemical performance to immobilize complementary DNA (cDNA) for hybridizing with MB@Zr-MOF-Apt via amide bonds. In the presence of cortisol, it would compete with cDNA for binding the Apt, resulting in the detachment of MB@Zr-MOF-Apt complex from the electrode surface, and the electrochemical signal of MB was decreased, while that of [Fe(CN)6]3-/4- was basically unchanged. The ratio of the electrochemical signals of [Fe(CN)6]3-/4- to MB was proportional to the cortisol concentration. Due to the greatly enhanced conductivity of the cMWCNTs-decorated Au electrode and the largely improved EC signals of Zr-MOF encapsulated MB probes, this ratiometric electrochemical aptasensor offered high sensitivity with an ultra-low detection limit of 0.0046 nM and a wide linearity of 0.01-1000 nM, as well as satisfactory accuracy with recoveries of 93.79-106.76 % in artificial sweat samples, providing a potential strategy for the detection of more trace hormones in different clinical samples by simply replacing the corresponding aptamers.

Multifunctional dopamine-modified conjugated polymer nanoparticles for ultrasensitive immunoassays

The development of simple and ultrasensitive immunoassays is critical for the early diagnosis and treatment of diseases. The efficient integration of amplification strategies with highly sensitive detection probes plays a key role in boosting the ultrasensitive immunoassays. In this paper, we report a multifunctional and integrated dopamine-modified conjugated polymer nanoparticle (DA-CPN) probe prepared by a one-step nanoprecipitation method for ultrasensitive immunoassay. The multifunctional DA-CPNs fully integrate the unique properties of dopamine and fluorescent conjugated polymer nanoparticles, while possessing three key capabilities. 1, DA-CPNs can be rapidly deposited onto adjacent proteins catalysed by horseradish peroxidase (HRP) labelled in the detection antibody in a sandwich immunoassay. 2, DA-CPNs undergo self-polymerization simultaneously, resulting in the assembly of large numbers of CPNs and thereby amplifying the detection signal. 3, CPNs possess excellent fluorescence brightness and strong photobleaching resistance, further enhancing the sensitivity of fluorescence immunoassays while simplifying the experimental procedure. Using carcinoma embryonic antigen (CEA) as a model, the proposed method demonstrated a wide linear range spanning five orders of magnitude and an exceptional sensitivity with a detection limit of 0.39 fg/mL. Therefore, this study based on DA-CPNs provides a versatile and highly promising platform for the ultrasensitive immunoassays and in vitro diagnosis of diseases.

Application of multi-variable calibration model of electrochemical sensor in high-accuracy long-term monitoring of cadmium ions

BACKGROUND

As the issue of heavy metal pollution has become increasingly prominent, the electrochemical detection of trace heavy metal ions in the marine environment has emerged as a significant and commonly utilized method. The detection of heavy metal ions has been a gradual replacement of traditional methods with electrochemical detection. However, the temperature and pH of seawater vary with time and location, leading to biases in the detection results of conventional ion-selective membrane sensors that only focus on the relationship between concentration and voltage.

RESULTS

This paper treats an experimental and modeling study to predict the electrochemical performance of ion-selective membrane sensors under varying temperatures and pH. By investigating the relationship between the working electrode response potential, pH, temperature, and cadmium ion concentration, a multivariate self-calibration model including pH, T, and the logarithm of cadmium ion concentration as independent variables was constructed. The determination coefficient R2 of the model was 0.9997, indicating a good fit. Automatic correction of electrochemical sensor minimizes the impact of temperature and pH, ensuring accurate readings of cadmium ion concentration during long-term monitoring. In addition, the recovery rates of Cd(II) concentration measurements were 113 % (coexisting with Na(I)) and 121 % (coexisting with Cu(II)), indicating good resistance to interference. Accuracy tests showed recovery rates ranging from 98 % to 121 %, demonstrating the good accuracy.

SIGNIFICANCE

Therefore, the ion-selective membrane sensors can reduce the interference of temperature and pH on the measurement of heavy metal ion concentrations through the multivariate self-calibration model. This study provides a reliable detection method for addressing the issue of heavy metal pollution in water bodies and has a broad application prospect.

Unraveling the Role of Programmed Cell Death Gene Signature and THBS1 in Gastric Cancer Progression and Therapy Response

BACKGROUND

Programmed cell death (PCD) genes play crucial roles in cancer progression and response to therapies, yet their impact on gastric cancer remains inadequately elucidated. This study aimed to create a prognostic cell death signature (PCDs) for gastric cancer, providing insights into potential therapeutic targets and survival predictors.

METHODS

We utilized TCGA-STAD and five GEO datasets, representing thousands of gastric cancer samples, for a comprehensive analysis of PCD genes. Differential gene expression, functional enrichment, survival, and machine learning analyses were conducted to construct a PCD-based prognostic model.

RESULTS

A total of 249 differentially expressed PCD genes were identified between cancerous and noncancerous gastric tissues. Subsequently, a PCD signature based on seven genes was developed and cross-validated across multiple cohorts. The high-PCD subtype correlated with poorer survival outcomes, lower tumor mutational burden, higher infiltration of M2 macrophages, lower levels of immune checkpoint expression, and decreased response to immunotherapy. A nomogram incorporating the PCDs provided accurate survival rate predictions. Additionally, nine machine learning algorithms were implemented for recurrence prediction, with the random forest model displaying high effectiveness. In this model, thrombospondin 1 (THBS1) showed the highest weight, and its knockdown significantly reduced gastric cancer cell proliferation and invasion.

CONCLUSION

This study underscores the significance of PCD genes, particularly THBS1, in gastric cancer progression and highlights their value as potential therapeutic targets. The predictive models developed here can aid in assessing patient prognosis and tailoring personalized treatment strategies.

IFN-γ/IL-2 Double-Color FluoroSpot Assay for Monitoring Human Primary T Cell Activation: Validation, Inter-Laboratory Comparison, and Recommendations for Clinical Studies

The enzyme-linked immunosorbent spot (EliSpot) assay and its fluorescence-based version, FluoroSpot, are sensitive immunoassays commonly used to quantify antigen-specific T and B lymphocytes and other immune cells in peripheral blood or homogenized tissues. Due to their high sensitivity, these assays are popular in clinical trials to evaluate the efficacy of immunotherapy and vaccines, which involve a high level of scrutiny to ensure valid study results. Besides industry consensus white papers and other research publications, there is no formal guidance for the industry on how to validate EliSpot and FluoroSpot assays to ensure their accurate performance for immune monitoring in clinical trials. Herein, we describe a comprehensive in vitro study using healthy human donor peripheral blood mononuclear cells (PBMCs) and model antigens to validate a double-color FluoroSpot assay for monitoring antigen-specific lymphocytes by detecting and quantifying IFN-γ and IL-2-producing lymphocytes. Validation parameters, acceptance criteria set-up, and assay limits-limit of detection (LOD), minimum positive control response, lower and upper limits of quantification (LLOQ and ULOQ)-were determined, and assay performance was demonstrated by assessing precision, specificity, linearity, and robustness. In addition, an inter-laboratory comparison demonstrated concordance between assay results from two laboratories. In summary, this study outlines a robust approach to EliSpot and FluoroSpot validation and demonstrates that the IFN-γ/IL-2 FluoroSpot assay is suitable for the reliable detection of antigen-specific immune responses from PBMC samples across laboratories and meets the current regulatory requirements for bioanalytical method validation.

Biocompatible AgInS2@hydrogel microelectrode with enhanced photoelectrochemical sensitivity for real-time in vivo dopamine monitoring

In situ monitoring of neurochemical dynamics is pivotal for understanding brain function and diagnosing neurological disorders. Conventional photoelectrochemical (PEC) sensors face limitations due to poor tissue compatibility and insufficient light penetration depth in vivo. Herein, we present a transparent and conductive hydrogel-based microelectrode (AgInS2@hydrogel) that integrates a biocompatible topological hydrogel with an AgInS2 semiconductor for selective dopamine (DA) detection. The hydrogel, synthesized via copolymerization of acrylamide and PR-PEGMA crosslinker with PEDOT:PSS as a conductive filler, exhibits tissue-matching elasticity (Young's modulus ≈118 kPa) and high conductivity (177 mS m-1). The AgInS2 semiconductor, in situ grown on the hydrogel surface, generates reactive oxygen species under visible light, triggering DA polymerization into polydopamine (PDA). This process establishes a self-enhancing feedback loop between AgInS2 and PDA, enabling selective DA detection with a linear range of 0.2-4 μM and limit of detection of 64 nM. Implanted into the mouse striatum, the sensor successfully tracked dynamic DA fluctuations induced by nomifensine maleate, demonstrating its capability for real-time in vivo neurochemical analysis. This work advances the development of minimally invasive, high-sensitivity tools for brain research.

Methylene-blue-encapsulated liposome for immobilization-free electrochemical immunoassay of interleukin-6 from nervous headache

Interleukin-6 (IL-6) protects neurons by inhibiting the expression of factors related to neuronal injury in nervous headache patients. The development of rapid and sensitive IL-6 detection methods will be very advantageous for easing the pain of such patients. In this work, an immobilization-free immunodetection method is explored for the voltammetric screening of IL-6 in serum samples from nervous headache patients. Initially, methylene-blue-encapsulated liposomes (MBLS) labeled with anti-IL-6 detection antibodies are confined in an anti-IL-6 capture antibody-coated microplate through a sandwich-type immunoreaction, and subsequently subjected to lysis treatment. After that, the lytic solution is transferred into a detection cell including a Nafion-modified working electrode. Methylene blue molecules with positive charge are captured on the negatively charged Nafion membrane, thus generating a voltammetric signal. The voltammetric peak currents are relative to the amount of IL-6 in the solution. Under optimized experimental situations, MBLS-based split-type electrochemical sensing protocols have acceptable voltammetric currents for IL-6 from 0.01 to 100 pg mL-1, and allow screening at a concentration of IL-6 as low as 9.1 fg mL-1. The batch-to-batch coefficients of variation were ≤11.95%. Good anti-interference capability was achieved against other biomolecules. Seven human serum specimens and two diluted serum samples including IL-6 obtained from nervous headache patients were determined by MBLS-based electrochemical immunoassay, and achieved well-matched results in comparison with those of the IL-6 ELISA protocol.

Efficient fluorescence and electrochemiluminescence dual-signal au nanoclusters-based portable antibiotic testing platform with super-wide detection range

The convenient detection of tetracycline (TC) residues has attracted considerable attention because irrational use of TC causes food pollution damaging the human health. Herein, a point-of-care testing (POCT) platform is established for the sensitive and specific determination of TC in a polydopamine-functionalised Eppendorf tube. In particular, TC can be efficiently recognised by an aptamer-antibody chimera to trigger visual fluorescence (FL) and electrochemiluminescence (ECL) 'dual-signal' response of gold nanoclusters. Consequently, the biosensor exhibits a wide detection range spanning from 5 fM to 1 μM, with low detection limits of 73 fM (visual FL) and 2.3 fM (ECL). Hence, it can be said that the POCT platform is superior to the enzyme-linked immunosorbent assay. The strategy utilises the strength of FL, i.e. visualisation, and that of ECL, i.e. high sensitivity, providing a guiding approach for the development of POCT in food security and environmental monitoring.

Colorimetric-fluorescent dual-mode background fluorescence-quenching lateral flow immunoassay: Principle, modeling, and application to folic acid detection

Conventional lateral flow immunoassays (LFIAs) face challenges in competitive detection of small molecule antigens, including inverse correlation between signal and analyte concentration and insufficient sensitivity. Background fluorescence quenching lateral flow immunoassay (BF-LFIA) offers a novel solution, but quantitative models to guide quencher design and sensitivity optimization are lacking. This study developed a dual-mode colorimetric-fluorescent BF-LFIA for highly sensitive folic acid (FA) detection using polystyrene-encapsulated ZnS@CdSe quantum dots (QDs) as background fluorophores and gold nanorods (AuNRs) or gold nanoparticles (AuNPs) as quenchers. Based on the inner filter effect (IFE) and heterogeneous capture reaction kinetics, we constructed a mathematical model for this dual-mode BF-LFIA. Under quasi-steady-state approximation, analytical expressions relating FA concentration to colorimetric and fluorescent signals were derived, enabling quantitative description of calibration curves for both modes. Due to higher molar extinction coefficients at excitation and emission wavelengths, AuNRs as quenchers exhibited superior sensitivity compared to AuNPs, achieving limits of detection of 0.14 ng/mL and 0.15 ng/mL for colorimetric and fluorescent modes, respectively. The mathematical model showed good agreement with experimental results. The derived calibration curve equations demonstrated better fitting goodness and residual normal distribution characteristics compared to conventional four-parameter logistic equations. Passing-Bablok regression analysis confirmed good consistency and comparability between the dual-mode BF-LFIA and a commercial FA fluorescent immunoassay kit. This study provides theoretical foundations for understanding dual-mode BF-LFIA principles and guiding optimization, offering new strategies for highly sensitive rapid detection of small molecules and other biomarkers.

A Fast Immunosensor Based on Biohybrid Self-Assembled Nanostructures for the Detection of KYNA as a Cerebrospinal Fluid Biomarker for Alzehimer's Disease

Although the role of kynurenic acid (KYNA) is not yet fully understood, recent research has implicated this tryptophan (Trp) metabolite as a significant biomarker in neurodegenerative diseases. In this study, we developed an immunosensor platform based on self-assembled polyelectrolyte multilayers (PEMs), employing an enzyme-labeled immunoreagent in a competitive displacement format that requires only a single wash step. This immunosensor enables the detection of KYNA and Trp with detection limits (LOD) of 9 pg/mL and 1.2 ng/mL, respectively. Results validated by traditional ELISA methods indicated elevated levels of KYNA and an increased KYNA/Trp ratio in the cerebrospinal fluid (CSF) of Alzheimer's patients compared to controls, consistent with previous findings. Additionally, this immunosensor platform can be readily adapted to detect other neuroactive Trp metabolites by substituting specific immunoreagents, supporting a flexible profile-based approach. This platform could serve as a rapid, cost-effective clinical tool for monitoring neurological and psychiatric disorders, potentially advancing therapeutic strategy development.

Nanoparticles-based electrochemical sensing platform for high-through immunoassay with redox-activity CaCO3 nanotags on a magnetic microfluidic device

A new nanoparticles-based sensing platform was designed for high-through electrochemical immunoassay of ferritin (FET) biomarker on a magneto-controlled microfluidic device by using anti-FET capture antibody-conjugated magnetic sensing probes. Thionine-doped calcium carbonate (CaCO3) nanoparticles labeled with anti-FET detection antibodies were utilized as the recognition elements. Introduction of target FET caused the sandwich-type immunoreaction between two antibodies. The formed immunocomplexes were attached onto magnetic microfluidic sensing interface through an external magnet. Subsequently, the carried CaCO3 nanoparticles were dissolved under acidic conditions to release the doped thionine molecules with redox activity. The thionine-based voltammetric signals increased with the increment of target FET levels within the linear range 0.01-100 ng mL-1. The limit of detection was 7.9 pg mL-1 FET. Good analytical properties such as selectivity, reproducibility, and accuracy were achieved with the nanoparticles-based magnetic electrochemical immunoassay. More significantly, the magnetic microfluidic electrochemical immunoassay provides new opportunities for rapid, simple, and cost-effective serum sample analysis.

A stand-alone and point-of-care electrochemical immuno-device for Salmonella typhimurium testing

The rapid development of accurate and point-of-care diagnostic tools for foodborne diseases has made a massive impact in global health. Salmonella typhimurium (S. typhimurium) exemplifies an enteric pathogen, being a gram-negative bacteria responsible for several gastrointestinal and systemic illnesses. However, the existing electrochemical devices used to detect S. typhimurium have always been bulky or unfully integrated, implying a critical need for the design and development of stand-alone and point-of-care electrochemical sensors for portable S. typhimurium testing. Herein, we present the first instance of a stand-alone and point-of-care electrochemical immuno-device (SPEID) capable of conducting S. typhimurium analysis in actual specimens of purified drinking water that is mixed with S. typhimurium and watermelon juice that is mixed with S. typhimurium at point-of-care. The development of SPEID for S. typhimurium testing is achieved by overcoming substantial engineering challenges in seamlessly integrating an autonomous-transportation module (ATM) for microfluidic autonomous and directional liquid transportation, an immune-testing module (ITM) for S. typhimurium testing, and an electronic-integration module (EIM) for converting signal and wirelessly transmitting. The SPEID is a stand-alone one which possesses pump-free and cost-effective feature for measuring S. typhimurium at point of care.

Highly sensitive detection of carcinoembryonic antigen via an electrochemical platform fabricated by CCLP- gold nanocomposite

An electrochemical CCLP-AuNPs (Calcium Cross Linked Pectin with Gold nanoparticles)-based biosensor was developed for sensitive detection and discrimination of carcinoembryonic antigen (CEA) based on dual signal amplification of gold nanoparticles tagged enzymatic catalysis. The electrochemical biosensor was fabricated by assembly of CCLP-AuNp modified GCE and subsequently anti CEA was immobilized on the modified GCE followed by the addition of CEA protein and then forming a sandwich-type conjugate was formed when the biosensor was successively reacted with Au-Anti CEA-HRP(Gold nanoparticles tagged with the antibody Carcinoembryonic antigen labelled with Horse radish peroxidase). In the presence of hydroquinone and hydrogen peroxide, in the PB(phosphate buffer) solution resulted in the fabrication of biosensor. The concentration of CEA in the range of 0.1 ng/mL to 10 ng/mL with low detection limit of 0.08 ng/mL thus the fabricated biosensor proves to be feasible tool for clinical diagnosis in complex biological systems and shows good for the early diagnosis of cancer.

Recent advances in MXene nanozyme-based optical and electrochemical biosensors for food safety analysis

The importance of nanotechnology is increasing every day in different fields and, especially, the application of nanomaterials has attracted considerable attention in food safety. Among different nanomaterials, MXenes, which are two-dimensional (2D) transition metal-based layered materials made of nitrides and carbides, have revolutionized various fields as a cutting-edge scientific discovery in nanotechnology. These materials have been widely used in the structure of biosensors and sensors due to their excellent metallic conductivity, mechanical stability, optical absorbance, good redox capability, and higher heterogeneous electron transfer rate. In particular, the application of MXenes as nanozymes has highlighted their high performance to a great extent in biosensor domains. The growing interest in these nanozymes is attributed to their specific physicochemical features. The key enzymatic features of these materials include activities similar to oxidase, peroxidase, catalase, and superoxide dismutase. In this review, initially, several common synthesis methods of MXenes are presented, emphasizing their significant role as nanozymes in constructing efficient sensors. Subsequently, several common applications of MXene nanozymes in food safety analysis are delved into, including the detection of bacteria, mycotoxins, antibiotic residues, and pesticide residues, along with their applications in different electrochemical and optical biosensors. In addition, the gap, limitation, and future perspective of these novel nanozymes in food safety are highlighted.

Wastewater-borne markers of neurodegenerative disease: β-methylamino-L-alanine and aminomethylphosphonic acid

Exposure to toxic organic chemicals such as β-methylamino-L-alanine (BMAA) and glyphosate has been associated with neurodegenerative diseases (NDDs), including amyotrophic lateral sclerosis (ALS), Parkinson's Disease (PD), and Alzheimer's Disease (AD). We explored the utility of BMAA and glyphosate's metabolite aminomethylphosphonic acid (AMPA) for serving as potential markers of NDDs by comparing levels of wastewater-borne BMAA and AMPA with regional U.S. rates of NDD prevalence. Newly developed liquid chromatography tandem mass spectrometry (LC-MS/MS) methods were applied to U.S. wastewater samples (n = 87) and resultant concentrations of putative biomarkers were statistically compared to NDD prevalence rates in conjunction with environmental data on algal blooms and agricultural glyphosate use. Locations of algal blooms were found to be significantly associated (p = 0.01) with ALS prevalence rates per 100,000 people. BMAA levels in wastewater were highly correlated (p < 0.0001) with ALS prevalence rates by region. BMAA in wastewater typically peaked in summer months. We conclude that NDD biomarker detection in wastewater holds potential value, with BMAA outperforming AMPA. Furthermore, prevalence data for NDDs may have to be reported to the Centers for Disease Control and Prevention at a higher geospatial resolution to further enhance the value for the present type of analysis. Further method development is needed for AMPA to be quantified using LC-MS/MS. Future method developments focusing on metabolites (e.g., AMPA) may enable epidemiologists to determine human exposure levels rather than the mere occurrence of toxic organic chemicals in the environment.

An electrochemical biosensor using AuNPs-Ti3C2Tx and ARGET ATRP reactions as signal amplification strategies for ultra-sensitive detection of HER2 protein

Human epidermal growth factor receptor 2 (HER2) status is an important factor in evaluating the prognosis of breast cancer patients. Therefore, it is particularly important to develop a simple and sensitive method for the detection of HER2-positive breast cancer. Here, an ultra-sensitive electrochemical biosensor for detecting HER2-specific proteins was assembled using gold nanoparticles and Two-dimensional carbides (AuNPs-Ti3C2Tx) as a conducting substrate. The prepared AuNPs-Ti3C2Tx not only has good electrical conductivity and strong electrochemical signal output, but also provides a large number of active sites for the AuS bonds assembly aptamer. In addition, the antibodies-modified functionalized graphene oxide (GO) as a carrier platform, which provides an additional boost for the detection of trace targets with high sensitivity under optimal conditions. Afterwards,HER2 protein was detected by signal amplification effect of AuNPs-Ti3C2Tx and functionalized GO combined with Electron transfer activated regeneration catalyst atomic transfer radical polymerization (ARGET ATRP). In the range of 1 to 105 ng·mL-1, there was a good linear relationship between the HER2 concentration and the signal intensity, with a limit of detection of 0.19 pg·mL-1. Moreover, this method has good selectivity and stability, and then still maintains good detection performance and strong anti-interference ability in the complex environment of normal human serum, which is expected to be applied in clinical application.

CRISPR-Cas12a/Cas13a Multiplex Bioassay for ctDNA and miRNA by Mass Spectrometry

The CRISPR-Cas system, particularly CRISPR-Cas12a and CRISPR-Cas13a, has been widely utilized in constructing various biosensors due to their "trans-cleavage" ability as a means of signal amplification. However, this universal "trans-cleavage" characteristic also presents a challenge for realizing CRISPR-Cas multiplexed bioanalysis. Besides, potential signal cascading interference and complicated design are notable obstacles in CRISPR-Cas multiplexed bioanalysis. Herein, we propose a mass spectrometry method that leverages the CRISPR-Cas12a/13a system to achieve simultaneous detection of ctDNA and miRNA. Based on the properties of the CRISPR-Cas12a/13a system, two types of nanoparticle reporter probes have been engineered, using cancer-related biomarkers ctDNA and miR-21 as our model analytes. The nanoparticle tags, which intrinsically incorporated millions of detectable atoms, combined with the CRISPR-Cas12a/Cas13a system's "trans-cleavage" ability, allow the proposed mass spectrometry strategy to achieve fmol-level detection limits without any nucleic acid amplification procedures. The assay was successfully applied to human serum samples, demonstrating its potential for early disease diagnosis and progression tracking.

Luteolin-Manganese Nanozyme Induces Apoptosis and Ferroptosis for Enhanced Cancer Therapy

Cancer presents a significant global public health challenge that impacts millions of individuals worldwide. The incorporation of natural products into cancer treatment has the potential to mitigate many of the side effects commonly associated with chemotherapy. This study builds on the advantages of enhancing the anticancer activity of natural flavonoids through metal chelation by synthesizing a natural antioxidant flavonoid complex, termed Lu-Mn nanozyme, which involves the chelation of luteolin with manganese ions. In vitro experiments demonstrated that Lu-Mn exhibits a strong affinity for hydrogen peroxide (H2O2) and effectively catalyzes the generation of hydroxyl radicals (•OH) from H2O2 within the tumor microenvironment. The administration of the Lu-Mn nanozyme not only induced apoptosis in tumor cells by upregulating the expression of cleaved caspase3 and caspase9 but also activated ferroptosis through downregulation of the NRF2-GPX4 signaling pathway. Furthermore, animal studies have shown that Lu-Mn possesses significant antitumor efficacy and a favorable safety profile. Collectively, these findings suggest that luteolin, through its chelation with metal ions, has considerable potential for application in cancer treatment.

Onion-like carbon based single-atom iron nanozyme for photothermal and catalytic synergistic antibacterial application

Nanozymes with oxidase (OXD)-like activity have emerged as promising antibacterial agents due to their capability of catalyzing atmospheric O2 to generate highly active free radicals. However, the precise engineering of functional nanozyme at the atomic level for antibacterial therapy presents a challenge. Here, atomically dispersed Fe atoms were loaded onto onion-like carbon (OLC) through a ligand-assisted calcination strategy, yielding a single-atom nanozyme (FeSA-OLC) with enhanced oxidase-like activity. The FeSA-OLC could catalyze the decomposition of O2 to produce active hydroxyl radicals (·OH) owing to the fully exposed Fe atoms and a highly curved carbon shell. Density functional theory calculation revealed that the single-atom Fe sites facilitated the generation of free radical species by promoting the adsorption and cleavage of OO bond. Meanwhile, the FeSA-OLC exhibited a notable photothermal conversion efficiency of 66.48% under near-infrared laser irradiation. Furthermore, in vitro experimental results demonstrated a synergistic antibacterial effect towards Escherichia coli due to the photothermal-enhanced oxidase-like activity. Overall, this work introduced a strategy to develop OLC-based single-atom nanozyme, thereby offering new avenues for photothermal-augmented antibacterial therapy.

CRISPR-Cas12a-Mediated Growth of Gold Nanoparticles for DNA Detection in Agarose Gel

The rapid, simple, and sensitive detection of nucleic acid biomarkers plays a significant role in clinical diagnosis. Herein, we develop a label-free and point-of-care approach for isothermal DNA detection through the trans-cleavage activity of CRISPR-Cas12 and the growth of gold nanomaterials in agarose gel. The presence of the target can activate CRISPR-Cas12a to cleave single-stranded DNA, thus modulating the length and number of DNA sequences that mediate the growth of gold nanoparticles (AuNPs) or gold nanorods (AuNRs). Due to the extraordinary plasmonic property of gold nanomaterials, they present characteristic absorption/color after the growth with unique shapes. The sensing strategy is applied to detect BRCA-1, a biomarker related to breast cancer, with limits of detection of 1.72 pM (AuNP-based) and 2.07 pM (AuNR-based). AuNPs/AuNRs can be immobilized in agarose gels that display different colors in the presence of target DNA sequences. The agarose gel-based test allows for a readout by the naked eye or the RGB value with a smartphone. The approach is isothermal and label-free without any surface modification of nanomaterials, which holds great potential for the detection of nucleic acids in clinical applications.

Tyramine-enzyme conjugate repeats for an interdigitated capacitance immunosensing array in the detection of neuroblastoma biomarker neuron-specific enolase

Methods based on enzyme labelling strategies have been widely developed for capacitance immunoassays, but most suffer from low sensitivity and are unfavorable for routine use in the early stages of diagnostics. Herein, we designed a highly efficient capacitance immunosensing method for the low-abundance neuroblastoma biomarker neuron-specific enolase (NSE) using an interdigitated micro-comb electrode. Initially, monoclonal mouse anti-human NSE capture antibodies were immobilized on the interdigitated gold electrodes using bovine serum albumin. Thereafter, a sandwich-type immunoreaction was carried out in the presence of target NSE using horseradish peroxidase (HRP)-labeled secondary antibodies. The labelled HRP subsequently triggered the formation of tyramine-enzyme conjugate repeats with the help of HRP-tyramine and H2O2. The concatenated HRP molecules catalyzed the oxidation of 4-chloro-1-naphthol to produce an insoluble precipitate on the interdigitated micro-comb electrode, resulting in a shift in capacitance. Two protocols, with and without tyramine-HRP repeats, were investigated for the detection of NSE, with improved analytical performance achieved through tyramine signal amplification. Under optimum conditions, the interdigitated capacitance immunosensors exhibited good responses to target NSE within a dynamic linear range of 1.0-10 000 pg mL-1, with a low detection limit of 0.78 pg mL-1. An intermediate reproducibility of ≤9.67% was accomplished with batch-to-batch consistency, and good anti-interference capacity against other proteins was acquired. No significant differences at the 0.05 significance level were encountered in the analysis of 12 human serum specimens between the developed capacitance immunosensor and the commercially available enzyme-linked immunosorbent assay (ELISA).

Nanozyme-based wearable biosensors for application in healthcare

Recent years have witnessed tremendous advances in wearable sensors, which play an essential role in personalized healthcare for their ability for real-time sensing and detection of human health information. Nanozymes, capable of mimicking the functions of natural enzymes and addressing their limitations, possess unique advantages such as structural stability, low cost, and ease of mass production, making them particularly beneficial for constructing recognition units in wearable biosensors. In this review, we aim to delineate the latest advancements in nanozymes for the development of wearable biosensors, focusing on key developments in nanozyme immobilization strategies, detection technologies, and biomedical applications. The review also highlights the current challenges and future perspectives. Ultimately, it aims to provide insights for future research endeavors in this rapidly evolving area.

A sensitive electrochemiluminescence immunosensor for CEA detection based on the ECL-RET between zinc-based metal-organic frameworks and ZiF-8@PDA

In this study, we developed a new system that using zinc-based metal-organic frameworks NH2-Zn-PTC as the donor and ZiF-8@PDA as the acceptor to achieve highly sensitive detection of carcinoembryonic antigen (CEA), using the fundamentals of electrochemiluminescence resonance energy transfer (ECL-RET). Firstly, the aggregation-induced quenching effect (ACQ) was eliminated by the coordination of PTC in MOF and the ECL signal was improved. Secondly, the ECL signal was further amplified by using Au NPs and amino groups as co-reaction promoters to generate more SO4.-. In addition, the introduction of ZiF-8@PDA as an acceptor and NH2-Zn-PTC as a donor took advantage of the feature of partial overlap of the UV-vis absorption spectrum and ECL emission spectra between the two, thereby effectively initiating the ECL-RET behavior, which improved the detection sensitivity of the sensor. The prepared immunosensor showed good linearity in the concentration range of 10-4 to 80 ng/mL with a detection limit of 18.20 fg/mL. This makes it promising for clinical testing of tumor markers.

Ti-co-Ce oxide decorated chitosan fiber oxidase mimic identified for portable monitoring of S2-, CrO42- and Fe2+ assisted with a smartphone

Environmental safety and protection is one of the most concerned topics nowadays. To conveniently monitor toxic S2-/CrO42- and to regulate bioactive Fe2+, Ti-co-Ce oxide decorated chitosan fiber (Ti-co-Ce ox@CC) was developed using microwave-assisted hydrothermal method. The integration of chitosan fiber and nano Ti-co-Ce oxide endowed Ti-co-Ce ox@CC with superior oxidase-like activity and improved water-dispersibility. It could quickly accelerate the oxidization of 3,3',5,5'-tetramethyl benzidine (TMB) with Vmax/Km of 6.67 × 10-8 M·s-1/0.0178 mM, much better than these (4.31 × 10-8 M·s-1/0.0471 mM) for Ti-co-Ce oxide only. Trace S2-, CrO42- or Fe2+ could selectively alter the oxidase-like activity with clear hyperchromic or hypochromic effect. Under the optimized conditions, there expressed excellent linear relationships between A652 and cS2-, cCrO42- or cFe2+ with ideal limits of detection (LOD) of 7.8 × 10-9 M, 5.0 × 10-8 M and 6.5 × 10-8 M respectively. What's more, the red-green-blue (RGB) values analyzed by a smartphone also expressed nice linear relationships with satisfactory LODs of 3.8 × 10-8 M, 7.7 × 10-8 M and 9.2 × 10-8 M for S2-, CrO42- and Fe2+. The proposed Ti-co-Ce ox@CC sensing platform will provide a promising potential for on-site intelligent identification of S2-, CrO42- and Fe2+ in practice.

A bifunctional MXene@PtPd NPs cascade DNAzyme-mediated fluorescence/colorimetric dual-mode biosensor for Pb2+ determination

Pb2+ has numerous sources in cosmetics, industrial pollution and other environments. Therefore, sensitive and accurate detection of Pb2+ content is extremely important in food safety. In this work, bifunctional nanomaterials Ti3C2@PtPd NPs with fluorescence quenching effect and peroxidase activity were prepared by in situ growth of platinum‑palladium nanoparticles (PtPd NPs) on the surface of 2D material Ti3C2. Combining the DNA enzyme recognition element with magnetic separation technology, we constructed a fluorescence/colorimetric dual-channel for the sensitive detection of Pb2+. Under the optimal conditions, the detection ranges of this fluorescence/colorimetric bimodal sensing strategy were 0.1-1000 nmol/L and 0.5-1000 nmol/L, respectively. The LOD of the fluorescence method was 23 pmol/L, and that of the colorimetric method was 74 pmol/L, and the results of the detection were visible to the naked eye. This dual-mode sensing method provides a new platform for accurate, reliable and visualized detection of Pb2+.

Dual-mode detection of α-fetoprotein using the photothermal effect and peroxidase-like activity of Au@Cu/Cu2O-rGO

α-Fetoprotein (AFP) is widely recognized as an important marker for monitoring hepatocellular carcinoma (HCC), and its monitoring using two different transduction mechanisms is an effective way to avoid the risk of false positives or false negatives. In this paper, Au@Cu/Cu2O-rGO was used as a photothermal converter as well as an actuator to promote the decomposition of hydrogen peroxide (H2O2), which was further designed as a probe for dual-mode detection to quantitatively assess AFP. The composite nanomaterials possessed photothermal conversion efficiencies (η) of up to 54.9 % and catalytically generated signals up to 1.6 times greater, relative to a single material. Based on the generated temperature and current signals, AFP has been sensitively detected in the range of 0.01-100 ng/mL, with limits of detection (LOD) of 5.62 pg/mL and 1.23 pg/mL, respectively. The dual-mode assay combines portability with high accuracy for the detection of human health systems.

Sensitive Electrochemical Immunosensor for Procymidone Detection Based on a Supramolecular Amplification Strategy

A sensitive electrochemical immunosensor for procymidone detection was developed based on a supramolecular amplification strategy. β-Cyclodextrin (β-CD)-based nanomaterials were employed to immobilize ferrocene derivative (FC)-functionalized antibodies/antigens through host-guest interactions. With the presence of procymidone, the formed β-CD-labeled bioconjugates were immobilized on the antibody-modified electrode after the immunoreaction, indicating fabrication of the immunosensor. The FC/β-CD complexes were with multiplex electroactive species and provided more sites for recognition groups, resulting in signal amplification of the sensor. Monitored with differential pulse voltammetry, the proposed immunosensor exhibited a wide linear range from 5 pM to 0.1 μM with a low detection limit (LOD) of 1.67 pM. The as-prepared immunosensor possessed high sensitivity, specificity, and stability and showed great potential for monitoring procymidone in the field of food safety.

IR-Driven Multisignal Conditioning for Multiplex Detection: Thermal-Responsive Triple DNA-Mediated Reconfigurable Photoelectrochemical/Photothermal Dual-Mode Strategy

Superior to traditional multiplex photoelectrochemical (PEC) sensors, integrated multitarget assay on a single reconstructive electrode interface is promising in real-time detection through eliminating the need of specialized instrumentation and cumbersome interfacial modifications. Current interface reconstruction approaches including pH modulation and bioenzyme cleavage involve biohazardous and time-consuming operations, which cannot meet the demand for rapid, eco-friendly, and portable detection, which are detrimental to the development of multiplex PEC sensors toward portability. Herein, we report a pioneer work on IR-driven "four-to-one" multisignal conditioning to facile reconfigure electrode interface for multitarget detection via photoelectrochemical/photothermal dual mode. The copper sulfide quantum dot (CuS QD) with excellent photoelectrochemical properties and a photothermal effect is first labeled on DNA S2. Once the CuS QD-S2 complementarily pairs with the DNA S3 on the photocathode surface, thermal-responsive triple DNA is formed, and the photocurrent and photothermal dual-mode signals for one target assay are produced. Upon the dissociation of the triple DNA by IR irradiation, the electrode interface is reconfigured for the self-calibrating dual-mode detection of another target. The feasibility of the IR-driven multisignal conditioning sensor is confirmed by detecting coexistent antibiotics kanamycin (KANA) and neomycin (NEO) in complex real samples. The low-loss interface reconfiguration and rapid "four-to-one" multisignal modulation highlight a broad prospect for self-calibrating multiplex assay in the fields of environment, medicine, and food safety.

f-p-d Orbital Hybridization Promotes Hydroxyl Intermediate Adsorption for Electrochemical Biomolecular Oxidation and Identification

The rational design of efficient hydroxyl intermediate (*OH) adsorption catalysts for dopamine electrooxidation still faces a major challenge. To address this challenge, a CeO2-loaded CuO catalyst inspired by the f-p-d orbital hybridization strategy is designed to achieve efficient *OH adsorption and improve dopamine oxidation. The experimental results and theoretical calculations demonstrate that the f-p-d orbital hybridization regulates the electron distribution at the Ce-O-Cu interface, which facilitates electron transfer and optimizes the adsorption of *OH, thereby promoting dopamine oxidation. The designed electrochemical sensor exhibits excellent catalytic activity and sensitivity, reaching a limit of detection of 3.22 nM. This work provides a promising approach for designing highly active electrocatalysts with orbital hybridization for dopamine oxidation.

Copper ions coordination-promoted self-assembly of DNA nanoflowers as cascade catalytic nanoreactor for colorimetric biosensor

The controllable geometry and multifunctionality of DNA nano-bioreactors hold immense promise for disease diagnosis. Herein, a facile rolling circle amplification (RCA)-based crystallization method has been developed for highly efficient self-assembly of three-dimensional (3D) DNA nano-bioreactors, which show excellent cascade catalytic performance by confining bio-enzyme (glucose oxidase (GOx) used in this case) and copper ions (Cu2+) in DNA nanoflowers (DNFs) structure. The participation of Cu2+ during the self-assembly process not only endows the nano-bioreactors (designated as GOx/Cu@DNFs) with inspiring peroxidase-like activity but also greatly improves the assembly efficiency and yield via the effective coordination between Cu2+ and RCA-generated long concatemeric DNAs. The integration of GOx and Cu2+ in the constrained flower-like DNA nanomatrices makes for the efficient inter-catalyst communication, resulting in the striking enhancement of biocatalytic cascade activity. Based on the prepared nano-bioreactors, a colorimetric biosensor has been constructed for glucose detection, achieving a wide linear range (2-400 μM) and a low detection limit (0.45 μM). Furthermore, the proposed sensing strategy enables the accurate determination and discrimination of glucose levels in healthy and diabetic sera, delivering gratifying outcomes. Overall, the meticulously crafted cascade nano-bioreactors not only illuminate the design of multifunctional nanomaterials based on RCA, but also expand the conceptual framework of the universal analytical method for determining small molecules with catalytic reactions to generate H2O2.

Prussian blue-doped CaCO3 nanoparticle-labeled secondary antibodies for electrochemical immunoassay of interleukin-6 with migraine patients

The sensitive and accurate identification of interleukin-6 (IL-6) in biological fluids is essential for assessing migraine due to its role in different physiological and pathological processes. In this study, we designed a simple and feasible electrochemical immunosensing method for the voltammetric measurement of IL-6. The electrochemical immunosensor was fabricated through covalent conjugation of anti-IL-6 capture antibodies on the glassy carbon electrode with a typical carbodiimide coupling method. Anti-IL-6 secondary antibodies were labeled on the surface of Prussian blue-doped CaCO3 nanoparticles (PBCaNP) via the epoxy-amino reaction. The assay was carried out with a sandwich-type immunoreaction. In the presence of target IL-6, the analyte was sandwiched between the capture antibody and detection antibody. Thereafter, the carried PBCaNP accompanying the secondary antibody could be detected by using square wave voltammetry (SWV). The voltammetric peak current was dependent on the concentration of target IL-6. Under optimum conditions, the electrochemical immunosensor exhibited good analytical properties, and allowed detection of IL-6 within a wide linear range from 0.1 to 1000 pg mL-1. The limit of detection was estimated to be 0.078 pg mL-1 of IL-6 at the 3sB criterion. An intermediate reproducibility of ≤10.59% was accomplished with batch-to-batch identification, and good anti-interference capacity against other biomolecules was achieved. Importantly, clinical human serum samples obtained from 15 migraine patients were analyzed with the developed electrochemical immunosensors, giving results well-matched with those obtained from the referenced enzyme-linked immunosorbent assay (ELISA) method.

High throughput electronic detection of biomarkers using enzymatically amplified metallization on nanostructured surfaces

Enzyme-linked immunosorbent assays are commonly used for clinical biomarker detection. However, they remain resource-intensive and difficult to scale globally. Here we present a miniaturized direct electronic biosensing modality which generates a simple and sensitive, quantitative, resistive readout of analyte binding in immunoassays. It utilizes the enhanced metallization generated by synergistic catalytic activity of nanostructured surfaces, created using gold nanoparticles, with enzymatic metallization, catalyzed by analyte-bound enzyme-labeled antibodies, to create a connected metal layer between microelectrodes. Based on this scheme, we develop a portable, high-throughput electronic biomarker detection device and platform which allows testing 96 different low volume (3 μL) clinical samples in a handheld device. We find an analyte concentration-dependent tunable digital switch-like behavior in the measured resistance of this device. We use this system to further explore the mechanism of enhanced metallization and find optimal parameters. Finally, we use this platform to perform quantitative measurement of viral antigen-specific antibody titers from convalescent COVID-19 patient serum.

Dual-electrode signal amplification self-powered biosensing platform based on nanozyme boosting target-induced DNA nanospace array for ultrasensitive detection of sugarcane Pokkah Boeng disease pathogenic bacteria

Sugarcane is a crop with significant economic importance worldwide. However, pokkah boeng disease poses a serious threat to its production and the sustainable development. There is a pressing necessity for precise and portable detection methods. We develop a dual-electrode signal amplification biosensing platform, for highly sensitive detection of sugarcane pokkah boeng disease pathogenic bacteria. This innovative platform integrates highly catalytic AuNPs/Mn3O4 nanozymes with N-GDY, along with a target-induced development of DNA nanostructure arrays. AuNPs/N-GDY serves as dual electrode substrates, and AuNPs/Mn3O4 nanozymes are surface-loaded as the bioanode. The biocathode is constructed by introducing DNA nanospace arrays onto the electrode through target-induced methods. [Ru(NH3)6]3+ is embedded into the nucleic acid double-helix scaffold via electrostatic adsorption, generating an EOCV signal that is strongly correlated with the target concentration. To further enhance sensitivity, the detection platform is combined with a capacitor to amplify the detection signal, utilizing its high power density, which results in a 22.5-fold increase in sensitivity. The method offers a linear detection range of 0.0001 to 10,000 pM and an detection limit of 32.5 aM (S/N = 3). This method supplies a novel approach for real-time monitoring and competent oversight of pokkah boeng disease pathogenic bacteria.

A cerium-doped tungsten trioxide-functionalized sensing platform for photoelectrochemical detection of ascorbic acid with high sensitivity

A highly efficient photoelectrochemical (PEC) strategy was proposed for the determination of ascorbic acid (AA). Cerium-doped tungsten trioxide (Ce-WO3) microrods were synthesized by a hydrothermal method and further characterized through transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. Thereafter, they were deposited onto a cleaned fluorine-doped tin oxide (FTO) glass forming the working electrode as the photoactive material. Under strong visible light irradiation, the resulting PEC sensing platform generated the corresponding electron-hole pairs, converting light signals into electrical signals. Ascorbic acid served as a good electron donor to trap holes for improvement of photocurrent responses on Ce-WO3/FTO. Besides, the strength of photocurrent signals versus the logarithm of ascorbic acid concentration showed a good linearity over the ascorbic acid concentration range of 100-4000 nM and the limit of detection (LOD) was estimated to be 28.6 nM. Importantly, this PEC sensor had a fast response, high sensitivity, and distinguished selectivity for detecting ascorbic acid. In addition, it also had the features of being simple to fabricate, low production cost, and portable, which made it a promising means of ascorbic acid determination.