Electrochemiluminescence-Incorporated Lateral Flow Immunosensors Using Ru(bpy)32+-Labeled Gold Nanoparticles for the Full-Range Detection of Physiological C-Reactive Protein Levels

Advances on Electrochemiluminescent Biosensors for TB Biomarkers

Tuberculosis (TB) is a highly contagious bacterial infection that remains a leading cause of death and persistent threat to global health. The spread of TB is exacerbated by the major limitations of conventional diagnostic approaches, such as complex technicalities, high cost, and low sensitivity. To address these challenges, recent research has focused on using electrochemiluminescence (ECL) as an alternative detection strategy coupled to biosensors. ECL biosensors leverage electrochemically generated chemiluminescence, converting electrical energy to light, as a novel transduction mechanism for TB biosensors. This unique approach offers several advantages, namely, wide linear dynamic ranges, improved device sensitivities, and prompt response times for sensitive early detection. This Review offers a comprehensive overview of advancements in ECL biosensor configurations, including detection and amplification strategies, substrates, and the development of luminophores and coreactants tailored for TB biomarker detection. The focus is on ECL biosensor designs, including biorecognition elements like immunosensors, DNA sensors, and aptasensors, along with various immobilization strategies tailored to target specific TB biomarkers. A comprehensive discussion spans biomarker detection trends over the past decade, clinical relevance, sensitivity thresholds, and detection limits. Furthermore, widely recognized TB biomarkers commonly detected in commercial diagnostic tests are discussed alongside novel markers that, while not exclusive to TB, have demonstrated clinical importance. This Review aims to highlight the potential of ECL-based biosensors as an effective means to advance an early, reliable, and accessible TB detection approach.

Electrochemiluminescence lateral flow immunosensor using luminol-labeled silver nanoparticles for highly sensitive and quantitative detection of cardiac troponin I

Cardiac troponin I (cTnI) is a highly specific biomarker of cardiomyocyte injury, released during cell disintegration and necrosis, and is the gold standard for diagnosing acute myocardial infarction (AMI). At the onset of AMI, cTnI appears in very low concentrations (pg/mL level), necessitating the development of highly sensitive and rapid detection sensors. In this study, an electrochemiluminescence lateral flow immunosensor (ECL-LFI) was designed using luminol-labeled silver nanoparticles (luminol@AgNPs) for the sensitive and quantitative detection of cTnI. A screen-printed electrode (SPE) was integrated beneath the nitrocellulose (NC) membrane with plastic plates of the same thickness applied on both sides of the SPE to ensure a smooth flow surface. Upon addition of cTnI and the luminol-H2O2 system, sandwich immune complexes formed by antibody-functionalized luminol@AgNPs on the strips generated electrochemiluminescent (ECL) signals. The ECL-LFI exhibited a broad linear detection range from 5 pg/mL to 100 ng/mL, with a detection limit as low as 1.6 pg/mL. Additionally, the results show excellent correlation with clinical tests, demonstrating that the ECL-LFI provides a promising point-of-care tool for the early diagnosis of AMI and other diseases.

Lateral flow immunoassay using plasmonic scattering

The lateral flow immunoassay (LFIA) is one of the most successful sensing platforms for real-world point-of-care (POC) testing. However, achieving PCR-level sensitivity without compromising the inherent advantages of LFIA, such as rapid and robust operation, affordability, and naked-eye detection, has remained a primary challenge. In this study, a plasmonic scattering-utilising LFIA was proposed, created by transparentising a nitrocellulose membrane and placing a light-absorbing backing card under the membrane. This LFIA minimised the background signal from its matrix, leading to substantially enhanced sensitivity and enabling naked-eye detection of the plasmonic scattering signal from gold nanoparticles without optics. Our plasmonic scattering-utilising LFIA showed an approximately 2600-4400 times higher detection limit compared with that of commercial LFIAs in influenza A assays. In addition, it exhibited 90% sensitivity in clinical validation, approaching PCR-level sensitivity, while commercial LFIAs showed 23-30% sensitivity. The plasmonic scattering-utilising LFIA plays a ground-breaking role in POC diagnostics and significantly boosts follow-up research.

Biorecognition-based electrochemical sensors for highly sensitive C-reactive protein detection: A review

Highly sensitive C-reactive protein (hsCRP) is a widely recognized biomarker for inflammation and cardiovascular diseases and plays a critical role in early diagnosis, risk assessment, and treatment monitoring. The development of sensitive and selective techniques for hsCRP detection is of paramount importance for clinical diagnostics. Electrochemical sensors have emerged as promising alternatives to traditional methods, offering rapid, cost-effective, and portable solutions for hsCRP analysis. This review comprehensively discusses advancements in biorecognition-based electrochemical sensors for hsCRP detection, focusing on label- and label-free approaches. This review highlights the sensor principles, designs, and performance, and emphasizes their advantages as well as limitations in various target applications. Recent studies have shown the potential of both label- and label-free-based sensors to achieve low detection limits and wide linear ranges comparable to traditional methods. In addition, we discuss the mechanisms, challenges, and future directions of biorecognition-based electrochemical sensors for hsCRP detection. This innovation can potentially revolutionize the diagnosis and treatment of cardiovascular and inflammatory diseases by enhancing the detection sensitivity and specificity. Ultimately, these advancements aim to improve patient outcomes by enabling earlier diagnosis, cost-effectiveness, and more precise monitoring, contributing to more effective management of cardiovascular health globally.

Electrochemiluminescence immunoassay using ionic-liquid submicron particles for prostate-specific antigen determination

In this study, ionic-liquid submicron particles (ILSPs) encapsulating the luminophore tris(2',2-bipyridyl)ruthenium (II) ([Ru(bpy)3]2+) were developed as a carrier for an electrochemiluminescence immunoassay (ECLIA). The ILSPs were applied to quantitative determination of the model analyte prostate-specific antigen (PSA). The electrochemiluminescence of [Ru(bpy)3]2+ was measured with 2-(dibutylamino)ethanol as a co-reactant in nine ionic liquids (ILs). The electrochemiluminescence intensity was higher in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSA]) and N-(2-methoxyethyl)-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide ([MEMP][TFSA]) than the other ILs. ILSPs were prepared using polyoxyethylene sorbitan monolaurate and sorbitan monooleate as surfactants and either [BMIM][TFSA] or [MEMP][TFSA]. The [BMIM][TFSA] ILSPs had a mean particle size of 244 nm and zeta potential of - 21.0 mV, and the [MEMP][TFSA] ILSPs had a mean particle size of 293 nm and zeta potential of - 17.9 mV. Microscope images showed that ILSPs were IL-in-water emulsions that completely encapsulated [Ru(bpy)3]2+. The ILSPs with [BMIM][TFSA] were more stable than those with [MEMP][TFSA], and [BMIM][TFSA] ILSPs was selected as a carrier in ECLIA for PSA determination. The calibration curve of PSA for ECLIA using the [BMIM][TFSA] ILSPs showed a good linear relationship (y = 0.29x + 4.02, r = 0.95) for the PSA concentration range of 100 pg/mL-100 μg/mL. The limit of detection and limit of quantification were 544 pg/mL and 35 ng/mL, respectively. Our results demonstrate that ECLIA using ILSPs can be used to easily determine the PSA concentration even with ILSPs in the particle state.

Polymerase Chain Reaction Chips for Biomarker Discovery and Validation in Drug Development

Polymerase chain reaction (PCR) chips are advanced, microfluidic platforms that have revolutionized biomarker discovery and validation because of their high sensitivity, specificity, and throughput levels. These chips miniaturize traditional PCR processes for the speed and precision of nucleic acid biomarker detection relevant to advancing drug development. Biomarkers, which are useful in helping to explain disease mechanisms, patient stratification, and therapeutic monitoring, are hard to identify and validate due to the complexity of biological systems and the limitations of traditional techniques. The challenges to which PCR chips respond include high-throughput capabilities coupled with real-time quantitative analysis, enabling researchers to identify novel biomarkers with greater accuracy and reproducibility. More recent design improvements of PCR chips have further expanded their functionality to also include digital and multiplex PCR technologies. Digital PCR chips are ideal for quantifying rare biomarkers, which is essential in oncology and infectious disease research. In contrast, multiplex PCR chips enable simultaneous analysis of multiple targets, therefore simplifying biomarker validation. Furthermore, single-cell PCR chips have made it possible to detect biomarkers at unprecedented resolution, hence revealing heterogeneity within cell populations. PCR chips are transforming drug development, enabling target identification, patient stratification, and therapeutic efficacy assessment. They play a major role in the development of companion diagnostics and, therefore, pave the way for personalized medicine, ensuring that the right patient receives the right treatment. While this tremendously promising technology has exhibited many challenges regarding its scalability, integration with other omics technologies, and conformity with regulatory requirements, many still prevail. Future breakthroughs in chip manufacturing, the integration of artificial intelligence, and multi-omics applications will further expand PCR chip capabilities. PCR chips will not only be important for the acceleration of drug discovery and development but also in raising the bar in improving patient outcomes and, hence, global health care as these technologies continue to mature.

Electroactive Nanomaterials for the Prevention and Treatment of Heart Failure: From Materials and Mechanisms to Applications

Heart failure (HF) represents a cardiovascular disease that significantly threatens global well-being and quality of life. Electroactive nanomaterials, characterized by their distinctive physical and chemical properties, emerge as promising candidates for HF prevention and management. This review comprehensively examines electroactive nanomaterials and their applications in HF intervention. It presents the definition, classification, and intrinsic characteristics of conductive, piezoelectric, and triboelectric nanomaterials, emphasizing their mechanical robustness, electrical conductivity, and piezoelectric coefficients. The review elucidates their applications and mechanisms: 1) early detection and diagnosis, employing nanomaterial-based sensors for real-time cardiac health monitoring; 2) cardiac tissue repair and regeneration, providing mechanical, chemical, and electrical stimuli for tissue restoration; 3) localized administration of bioactive biomolecules, genes, or pharmacotherapeutic agents, using nanomaterials as advanced drug delivery systems; and 4) electrical stimulation therapies, leveraging their properties for innovative pacemaker and neurostimulation technologies. Challenges in clinical translation, such as biocompatibility, stability, and scalability, are discussed, along with future prospects and potential innovations, including multifunctional and stimuli-responsive nanomaterials for precise HF therapies. This review encapsulates current research and future directions concerning the use of electroactive nanomaterials in HF prevention and management, highlighting their potential to innovating in cardiovascular medicine.

Enzyme-free immunoassay for rapid, sensitive, and selective detection of C-reactive protein

C-reactive protein (CRP) is a protein made by the liver, which is released into the bloodstream in response to inflammation. Furthermore, CRP is a potential risk factor for heart disease. Hence, it is of great importance to develop a rapid, sensitive, accurate, and cost-effective method for CRP detection. Herein, we report an enzyme-free fluorescent assay for the rapid and ultra-sensitive detection of CRP with a limit of detection (LOD) reaching as low as 3.08 pg/mL (i.e., ~ 27 fM). The high sensitivity of our method was simply achieved via dual-functionalized gold nanoparticles (AuNPs). By regulating the molar ratio of DNA to CRP antibody immobilized on the AuNP surface, hundreds to thousands-fold amplification in the analyte signal could be instantly accomplished. Furthermore, our sensor was selective: non-target proteins such as interleukin-6, interleukin-1β, procalcitonin, bovine serum albumin, and human serum albumin did not interfere with the target CRP detection. Moreover, simulated serum samples were successfully analyzed. Given the excellent sensitivity, selectivity, and high resistance to complicated matrices, the enzyme-free CRP detection strategy developed in this work can be used as a generic platform to construct sensors for a wide variety of protein biomarkers and hence offers potential as a tool for rapid, accurate, and low-cost medical diagnosis.

Immunosensing of Cardiac Troponin I (cTnI) Using a Two-Electrode Electrochemiluminescence Platform with Near Persisting Luminescence Generated on a Ru(bpy)32+-Tripropylamine System

An economical, rapid, and ultrasensitive detection of biomolecules in clinical settings is very crucial, particularly for the early detection of Cardiac Troponin I (cTnI), which is the gold standard biomarker for Acute Myocardial Infarction (AMI). Electrochemiluminescence (ECL) has risen in prominence as an important technique for in vitro diagnosis and detection by virtue of its high sensitivity reaching a femtomolar level. This study introduces an economically feasible nanoplatform for ECL immunosensing, consisting of a gold nanoparticle (AuNP) with Ru(bpy)32+ and tripropylamine (TPA) system, which is a potential ECL luminophore and coreactant system. AuNPs serve the role of an ECL signal enhancer as well as the carrier of antibody, which enables the creation of a label-free immunosensor for antigen-antibody interactions. The prepared immunosensor detected cTnI with a detection limit (LOD) of 0.03 ng/mL. This potential immunosensor provides appreciable results in the detection of cTnI from spiked real serum analysis, which shows its potential application in low-resource clinical settings.

Au Nanoparticles-Trisbipyridine Ruthenium(II) Nanoaggregates as Signal-Amplifying SERS Tags for Immunoassay of cTnI

Acute myocardial infarction (AMI) is one of the leading causes of human mortality worldwide. In the early stages of AMI, the patient's electrocardiogram (ECG) may not change, so the fast, sensitive, and accurate detection of the specific biomarker of cardiac troponin I (cTnI) is of great importance in the early diagnosis of AMI. In this work, for the first time, electrostatic nanoaggregates of negatively charged Au nanoparticles and positively charged trisbipyridine ruthenium(II) ions (i.e., (-)AuNPs|[Ru(bpy)3]2+ ENAs) as novel and signal-amplifying surface-enhanced Raman scattering (SERS) tags were synthesized in an easy and rapid (<3 min) way and applied in the highly sensitive, rapid detection of cTnI in human serum by being combined with an immunochromatographic test strip (ICTS). The synthesized (-)AuNPs|[Ru(bpy)3]2+ ENAs exhibited strong SERS activity due to the multiple Raman-active units (three bpy ligands) carried by each [Ru(bpy)3]2+ complex ion and abundant hotspots in each SERS tag. The developed (-)AuNPs|[Ru(bpy)3]2+ ENAs-based SERS-ICTS has been validated to be applicable in detection of cTnI in human serum with excellent sensing performances, such as fast testing (5 min) and a low detection limit (60 pg/mL). It is envisioned that the developed (-)AuNPs|[Ru(bpy)3]2+ ENAs-based SERS-ICTS sensor may have promising applications in point of care testing of various biomarkers in clinic. Additionally, this work may inspire the finding and the application of new types of Raman reporter molecules based on high valent metal-multi ligand coordination compounds like [Ru(bpy)3]2+.

Rapid Size Determination of Quasispherical Gold Nanoparticles by Electrocatalysis Efficiency-Regulated Electrochemiluminescence

The size of gold nanoparticles (AuNPs) largely decides their properties and applications, making the rapid screening of AuNP size important. Despite the fact that AuNP-amplified electrochemiluminescence (ECL) is widely used in various ECL sensing applications, the mechanism of ECL enhancement remains elusive, especially the quantitative relationship between the enhanced ECL intensity and the size of AuNPs. In this work, taking quasispherical and citrate-stabilized AuNPs as model nanoparticles, we have reported that the ECL intensity of the S2O82--O2 system enhanced significantly with the increasing AuNP size. AuNPs acted as bielectrocatalysts for reducing the S2O82- and O2. The further study of enhancement mechanism demonstrates that AuNPs with increasing size facilitate the electron transfer and promote the generation of radicals required for the ECL emission, which produces more emitters-singlet oxygen. Meanwhile, the high surface density of citrate on small AuNPs suppresses the ECL signal by forming an electrostatic barrier. On the basis of the above phenomena, an ECL-based rapid AuNP size screening approach has been established. The accuracy of this platform is verified by the consistent results in comparison to transmission electron microscopy (TEM) measurements. This work not only provides deep insight into the correlation between the AuNP size and the ECL enhancement but also contributes an alternative to the TEM technique for the rapid AuNP size screening. Additionally, this study also extends the exploration of ECL-based structure analysis techniques toward nanomaterials through clarifying the structure-electrocatalytic activity correlation.

Preparation and application of multiple particle binding-liposomes for electrochemiluminescent signal amplification in bioassays

In this study, multiple particle binding-liposomes (MPB-Lips), encapsulating the luminophore tris(2',2-bipyridyl)ruthenium (II) complex ([Ru(bpy)3]2+), were developed as an electrochemiluminescence (ECL) signal amplifier and were applied to detect the model analyte streptavidin (SA) using the indirect competitive ECL method. The MPB-Lips were prepared by mixing various ratios of two different liposomes-one containing a phospholipid with a primary amine group and a biotinyl group (BIO/NH2-Lip) and one containing a phospholipid with an N-hydroxysuccinimide group (NHS-Lip) to allow binding between particles via amide bonds. Quartz crystal microbalance analysis using SA-modified gold-coated quartz crystals showed that the frequency shift values of MPB-Lips gradually decreased in the order BIO/NH2-Lip:NHS-Lip = 1:0 < 1:1 < 1:3 < 1:5. This indicated that MPB-Lips were successfully formed. The indirect competitive ECL method using SA-modified gold electrodes showed that the 1:5-Lip system had greater sensitivity than the 1:0-Lip system-the limit of detection and quantification values for the systems were 1.84 and 6.30 μg mL-1 for 1:0-Lip, and 1.20 and 1.74 μg mL-1 for 1:5-Lip. Finally, the recovery of SA spiked in fetal bovine serum samples using the 1:5-Lip system showed good accuracy and precision with a recovery rate of 83-106% and relative standard deviation of 4-14%. Our study demonstrated that the MPB-Lips system was an effective and useful ECL amplifier and the ECL method using MPB-Lips could be applied to detect an analyte in a real sample.

A nanoparticle-assisted signal-enhancement technique for lateral flow immunoassays

Lateral flow immunoassay (LFIA), an affordable and rapid paper-based detection technology, is employed extensively in clinical diagnosis, environmental monitoring, and food safety analysis. The COVID-19 pandemic underscored the validity and adoption of LFIA in performing large-scale clinical and public health testing. The unprecedented demand for prompt diagnostic responses and advances in nanotechnology have fueled the rise of next-generation LFIA technologies. The utilization of nanoparticles to amplify signals represents an innovative approach aimed at augmenting LFIA sensitivity. This review probes the nanoparticle-assisted amplification strategies in LFIA applications to secure low detection limits and expedited response rates. Emphasis is placed on comprehending the correlation between the physicochemical properties of nanoparticles and LFIA performance. Lastly, we shed light on the challenges and opportunities in this prolific field.

Electrochemical Lateral Flow Immunoassay with Built-In Electrodes for Ultrasensitive and Wireless Detection of Inflammatory Biomarkers

Paper-based lateral flow immunoassays (LFIAs) are cost-effective, portable, and simple methods for detection of diverse analytes, which however only provide qualitative or semiquantitative results and lack sufficient sensitivity. A combination of LFIA and electrochemical detection, namely, electrochemical lateral flow immunoassay (eLFIA), enables quantitative detection of analytes with high sensitivity, but the integration of external electrodes makes the system relatively expensive and unstable. Herein, the working, counter, and reference electrodes were prepared directly on the nitrocellulose membrane using screen printing, which remarkably simplified the structure of eLFIA and decreased the cost. Moreover, a horseradish peroxidase (HRP)-based electrochemical signal amplification strategy was used for further increasing the analytical sensitivity. HRP captured on the working electrode can catalyze the oxidation of tetramethylbenzidine (TMB) to form the TMB-TMBox precipitate on the electrode surface, which as an electrochemically active product can output an amplified current for quantification. We demonstrated that the eLFIA could detect low-abundant inflammatory biomarkers in human plasma samples with limits of detection of 0.17 and 0.54 pg mL-1 for interleukin-6 and C-reactive protein, respectively. Finally, a fully portable system was fabricated by integrating eLFIA with a flexible and wireless electrochemical workstation, realizing the point-of-care detection of interleukin-6.

Recent progress on charge transfer engineering in reticular framework for efficient electrochemiluminescence

Electrochemiluminescence (ECL) is a luminescence production technique triggered by electrochemistry, which has emerged as a powerful analytical technique in bioanalysis and clinical diagnosis. During ECL, charge transfer (CT) is an important process between electrochemical excitation and luminescent emission, and dramatically affects the efficiency of exciton generation, playing a pivotal role in the light-emitting properties of nanomaterials. Reticular framework materials with intramolecular/intermolecular interactions offer a promising platform for regulating CT pathways and enhancing luminescence efficiency. Deciphering the role of intramolecular/intermolecular CT processes in reticular framework materials allows for the targeted design and synthesis of emitters with precisely controlled CT properties. This sheds light on the microscopic mechanisms of electro-optical conversion in ECL, propelling advancements in their efficiency and breakthrough applications. This mini-review focuses on recent advancements in engineering CT within reticular frameworks to boost ECL efficiency. We summarized strategies including intra-reticular charge transfer, CT between the metal and ligands, and CT between guest molecules and frameworks within reticular frameworks, which holds promise for developing next-generation ECL devices with enhanced sensitivity and light emission.

A dry chemistry-based self-enhanced electrochemiluminescence lateral flow immunoassay sensor for accurate sample-to-answer detection of luteinizing hormone

BACKGROUND

Colorimetric lateral flow immunoassay (LFIA) is a widely used point-of-care testing (POCT) technology, while it has entered a bottleneck period because of low detection sensitivity, expensive preparation materials, and incapable quantitative detection. Therefore, it is necessary to develop a novel POCT method that is ultrasensitive, simple, portable, and capable of accurately detecting biomarkers in biofluids daily, particularly for pregnancy preparation and early screening of diseases.

RESULT

In this work, a novel dry chemistry-based self-enhanced electrochemiluminescence (DC-SE-ECL) LFIA sensor is introduced for accurate POCT of luteinizing hormone (LH). The proposed DC-SE-ECL immunosensor significantly improves the detection sensitivity through the Poly-l-Lysine (PLL)-based SE-ECL probe and cathode modification of closed bipolar electrode (C-BPE). Additionally, a new type of C-BPE configuration is designed for easily performing the LFIA. And, two standalone absorbent pads are symmetrically arranged below the reporting channel of the electrode pad to decease useless residues on the detection pad, which further improves the detection performance. Under optimized conditions, the proposed LFIA sensor has a low limit of detection (9.274 μIU mL-1) and a wide linear dynamic range (0.01-100 mIU mL-1), together with good selectivity, repeatability and storage stability.

SIGNIFICANCE

These results indicate that the proposed DC-SE-ECL method has the potential as a new tool for detecting biomarkers in clinical samples.

Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer

This article introduces distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) and carbon dots (CDs) for simultaneous quantification of cytokine biomarkers, namely C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in human biological samples for diagnosis of cytokine syndrome. Using fluorescent CDs and MIP technology, the dPAD exhibits high selectivity and sensitivity. Detection is based on fluorescence quenching of CDs achieved through the interaction of the target analytes with the MIP layer on the paper substrate. Quantitative analysis is easily accomplished by measuring the distance length of quenched fluorescence with a traditional ruler and naked eye readout enabling rapid diagnosis of cytokine syndrome and the underlying infection. Our sensor demonstrated linear ranges of 2.50-24.0 pg mL-1 (R2 = 0.9974), 0.25-3.20 pg mL-1 (R2 = 0.9985), and 1.50-16.0 pg mL-1 (R2 = 0.9966) with detection limits (LODs) of 2.50, 0.25, and 1.50 pg mL-1 for CRP, TNF-α, and IL-6, respectively. This sensor also demonstrated remarkable selectivity compared to a sensor employing a non-imprinted polymer (NIP), and precision with the highest relative standard deviation (RSD) of 5.14%. The sensor is more accessible compared to prior methods relying on expensive reagents and instruments and complex fabrication methods. Furthermore, the assay provided notable accuracy for monitoring these biomarkers in various human samples with recovery percentages ranging between 99.22% and 103.58%. By integrating microfluidic systems, nanosensing, and MIPs technology, our developed dPADs hold significant potential as a cost-effective and user-friendly analytical method for point-of-care diagnostics (POC) of cytokine-related disorders. This concept can be further extended to developing diagnostic devices for other biomarkers.

Rapid and Convenient Single-Chain Variable Fragment-Employed Electrochemical C-Reactive Protein Detection System

Although IgG-free immunosensors are in high demand owing to ethical concerns, the development of convenient immunosensors that alternatively integrate recombinantly produced antibody fragments, such as single-chain variable fragments (scFvs), remains challenging. The low affinity of antibody fragments, unlike IgG, caused by monovalent binding to targets often leads to decreased sensitivity. We improved the affinity owing to the bivalent effect by fabricating a bivalent antibody-enzyme complex (AEC) composed of two scFvs and a single glucose dehydrogenase, and developed a rapid and convenient scFv-employed electrochemical detection system for the C-reactive protein (CRP), which is a homopentameric protein biomarker of systemic inflammation. The development of a point-of-care testing (POCT) system is highly desirable; however, no scFv-based CRP-POCT immunosensors have been developed. As expected, the bivalent AEC showed higher affinity than the single scFv and contributed to the high sensitivity of CRP detection. The electrochemical CRP detection using scFv-immobilized magnetic beads and the bivalent AEC as capture and detection antibodies, respectively, was achieved in 20 min without washing steps in human serum and the linear range was 1-10 nM with the limit of detection of 2.9 nM, which has potential to meet the criteria required for POCT application in rapidity, convenience, and hand-held detection devices without employing IgGs.

Amplification of an Electrochemiluminescence-Emissive Aptamer into DNA Nanotags for Sensitive Fecal Calprotectin Determination

The precision additive manufacturing and tessellated multitasking out of the structural DNA nanotechnology enable a configurable expression of densified electrochemiluminescent (ECL) complexes, which would streamline the bioconjugation while multiplying signals. Herein, a completely DNA-scaffold ECL "polyploid" was replicated out via the living course of rolling circle amplification. The amplicon carried the aptameric sequences of ZnPPIX/TSPP porphyrin as photoreactive centers that rallied at periodical intervals of the persistent extension into a close-packed nanoflower, ZnPDFI/II. Both microscopies and electrophoresis proved the robust nesting of guests at their deployed gene loci, while multispectral comparisons among cofactor substituents pinpointed the pivotal roles of singlet seclusion and Zn2+-chelation for the sake of intensive ECL irradiation. The adversity-resilient hydrogel texture made lipoidal filmogens as porphyrinic ECL prerequisites to be of no need at all, thus not only simplifying assay flows but also inspiring an in situ labeling plan. Upon bioprocessing optimization, an enriched probe ZnPDFIII was further derived that interpolated the binding motif related to calprotectin as validated by molecular docking and affinity titration. With it being a strongly indicative marker of inflammatory bowel disease (IBD), a competitive ECL aptasensing strategy was contrived, managing a signal-on and sensitive detection in mild conditions with a subnanogram-per-milliliter limit of detection by 2 orders of magnitude lower than the standard method as well as a comparable accuracy in clinical stool sample testing. Distinct from those conventional chemophysical rebuilding routes, this de novo biosynthetic fusion demonstrated a promising alternative toward ECL-source bioengineering, which may intrigue vibrant explorations of other ECL-shedding fabrics and, accordingly, a new bioanalytic mode downstream.

The Fabrication of a Probe-Integrated Electrochemiluminescence Aptasensor Based on Double-Layered Nanochannel Array with Opposite Charges for the Sensitive Determination of C-Reactive Protein

The effective and sensitive detection of the important biomarker, C-reactive protein (CRP), is of great significance in clinical diagnosis. The development of a convenient and highly sensitive electrochemiluminescence (ECL) aptasensor with an immobilized emitter probe is highly desirable. In this work, a probe-integrated ECL aptamer sensor was constructed based on a bipolar silica nanochannel film (bp-SNF) modified electrode for the highly sensitive ECL detection of CRP. The bp-SNF, modified on an ITO electrode, consisted of a dual-layered SNF film, including the negatively charged inner SNF (n-SNF) and the outer SNF with a positive charge and amino groups (p-SNF). The ECL emitter, tris(bipyridine) ruthenium (II) (Ru(bpy)32+), was stably immobilized in a nanochannel of bp-SNF using the dual electrostatic interactions with n-SNF attracting and p-SNF repelling. The amino groups on the outer surface of bp-SNF were aldehyde derivatized, allowing for the covalent immobilization of recognitive aptamers (5'-NH2-CGAAGGGGATTCGAGGGGTGATTGCGTGCTCCATTTGGTG-3'), leading to the recognition interface. When CRP bound to the aptamer on the recognition interface, the formed complex increased the interface resistance and reduced the diffusion of the co-reactant tripropylamine (TPA) into the nanochannels, leading to a decrease in the ECL signal. Based on this mechanism, the constructed aptamer sensor could achieve a sensitive ECL detection of CRP ranging from 0.01 to 1000 ng/mL, with a detection limit (DL) of 8.5 pg/mL. The method for constructing this probe-integrated ECL aptamer sensor is simple, and it offers a high probe stability, good selectivity, and high sensitivity.

Electrochemiluminescence Aptasensor with Dual Signal Amplification by Silica Nanochannel-Based Confinement Effect on Nanocatalyst and Efficient Emitter Enrichment for Highly Sensitive Detection of C-Reactive Protein

The rapid and sensitive detection of the important biomarker C-reactive protein (CRP) is of great significance for monitoring inflammation and tissue damage. In this work, an electrochemiluminescence (ECL) aptasensor was fabricated based on dual signal amplification for the sensitive detection of CRP in serum samples. The sensor was constructed by modifying a silica nanochannel array film (SNF) on a cost-effective indium tin oxide (ITO) electrode using the Stöber solution growth method. Gold nanoparticles (AuNPs) were grown in situ within the nanochannels using a simple electrodeposition method as a nanocatalyst to enhance the active electrode area as well as the ECL signal. The negatively charged nanochannels also significantly enriched the positively charged ECL emitters, further amplifying the signal. The recognition aptamer was covalently immobilized on the outer surface of SNF after modification with epoxy groups, constructing the aptasensor. In the presence of CRP, the formation of complexes on the recognitive interface led to a decrease in the diffusion of ECL emitters and co-reactants to the supporting electrode, resulting in a reduction in the ECL signal. Based on this mechanism, ECL detection of CRP was achieved with a linear range of 10 pg/mL to 1 μg/mL and a low limit of detection (7.4 pg/mL). The ECL aptasensor developed in this study offers advantages such as simple fabrication and high sensitivity, making promising applications in biomarker detection.

New technologies and reagents in lateral flow assay (LFA) designs for enhancing accuracy and sensitivity

Lateral flow assays (LFAs) are a popular method for quick and affordable diagnostic testing because they are easy to use, portable, and user-friendly. However, LFA design has always faced challenges regarding sensitivity, accuracy, and complexity of the operation. By integrating new technologies and reagents, the sensitivity and accuracy of LFAs can be improved while minimizing the complexity and potential for false positives. Surface enhanced Raman spectroscopy (SERS), photoacoustic techniques, fluorescence resonance energy transfer (FRET), and the integration of smartphones and thermal readers can improve LFA accuracy and sensitivity. To ensure reliable and accurate results, careful assay design and validation, appropriate controls, and optimization of assay conditions are necessary. Continued innovation in LFA technology is crucial to improving the reliability and accuracy of rapid diagnostic testing and expanding its applications to various areas, such as food testing, water quality monitoring, and environmental testing.

Highly Sensitive Photothermal Microfluidic Thread-Based Duplex Immunosensor for Point-of-Care Monitoring

Herein, we successfully developed a thread-based analytical device (μTAD) for simultaneous immunosensing of two biomolecules with attomolar sensitivity by using a photothermal effect. A photothermal effect exploits a strong light-to-heat energy conversion of plasmonic metallic nanoparticles at localized surface plasmon resonance. The key innovation is to utilize the cotton thread to realize this sensor and the use of chitosan modification for enhancing the microfluidic properties, for improving the efficiency of photothermal conversion, and for sensor stability. The developed μTAD sensor consists of (i) a sample zone, (ii) a conjugation zone coated with gold nanoparticles bound with an antibody (AuNPs-Ab2), and (iii) a test zone immobilized with a capture antibody (anti-Ab1). The prepared μTAD is assembled in a custom three-dimensional (3D) printed device which holds the laser for illumination and the thermometer for readout. The 3D-printed supportive device enhances signal response by focusing light and localizing the heat generated. For proof of concept, simultaneous sensing of two key stress and inflammation biomarkers, namely, cortisol and interleukin-6 (IL-6), are monitored using this technique. Under optimization, this device exhibited a detection linear range of 2.0-14.0 ag/mL (R2 = 0.9988) and 30.0-360.0 fg/mL (R2 = 0.9942) with a detection limit (LOD) of 1.40 ag/mL (∼3.86 amol/L) and 20.0 fg/mL (∼950.0 amol/L) for cortisol and IL-6, respectively. Furthermore, the analysis of both biomolecules in human samples indicated recoveries in the range of 98.8%-102.88% with the highest relative standard deviation being 3.49%, offering great accuracy and precision. These results are the highest reported sensitivity for these analytes using an immunoassay method. Our PT-μTAD strategy is therefore a promising approach for detecting biomolecules in resource-limited point-of-care settings.

Low-Cost Full-Range Detection of C-Reactive Protein in Clinical Samples by Aptamer Hairpin Probes and Coprecipitation of Silver Ions and Gold Nanoparticles

C-reactive protein (CRP) levels can vary widely related to diverse disease contexts. However, expensive antibodies have impeded the clinical utility of antibody-based full-range CRP assays, especially in developing countries. Herein, we established a low-cost, antibody-free, 96-well plate-based full-range CRP detection method by combining gold nanoparticles (AuNPs), silver iodide (AgI), Eosin Y, and the aptamer hairpin probe (AHP) with Ag+-mediated cytosine-cytosine mismatches, that is, the Au@AgI/Eosin Y-AHP method. After binding the target CRP, the AHP released Ag+, which subsequently induced the aggregation of AuNPs on the surface of AgI colloids, resulting in a significant increase in the adsorption of Eosin Y on the surface of AuNPs. The changes in fluorescence intensity (FI) of Eosin Y in the supernate without and with CRP were proportional to the concentration of the CRP in the wide range of 0.01-40 ng/mL (r = 0.9969), and 96 samples can be detected in 96-well plates simultaneously by a microplate reader within 45 min. Remarkably, the CRP levels of 100 clinical samples achieved with the Au@AgI/Eosin Y-AHP had a good correlation with those obtained with the latex-enhanced immune turbidimetry assay (r = 0.986). Furthermore, the kit based on the Au@AgI/Eosin Y-AHP method costs only $8.1 for 100 tests. Therefore, the new method is beneficial for less developed areas where expensive assays are not affordable.

Electrochemiluminescence resonance energy transfer between Ru(bpy)32+@Cu3(HHTP)2 and GO-Au composites for C-reactive protein detection

Designing innovative electrochemiluminescence (ECL) immunosensors is critical for the detection of biomarkers with a low concentration and the precise evaluation of clinical diseases. Herein, a Cu₃(hexahydroxytriphenylene)₂ (Cu₃(HHTP)₂) nanoflake-based sandwich-type ECL immunosensor was constructed for C-Reactive Protein (CRP) detection. The Cu₃(HHTP)₂ nanoflake, an electronically conductive metal-organic framework (MOF), has a periodically arranged porous structure with a cavity size of 2 nm, which not only accommodates a large amount of Ru(bpy)₃²⁺ but also confines the spatial diffusion of active species. Therefore, the Ru(bpy)₃²⁺-loaded Cu₃(HHTP)₂ nanocomplex (Ru@CuMOF) as an ECL emitter exhibits an enhanced ECL efficiency. The ECL resonance energy transfer (ECL-RET) was accomplished by combining Ru@CuMOF used as a donor with gold nanoparticles-functionalized graphene oxide nanosheets (GO-Au) utilized as an acceptor. This should be ascribed to the fact that the ECL emission spectrum of Ru@CuMOF shows the strongest signal intensity at 615 nm, overlapping with the absorption spectrum of GO-Au at 580-680 nm. Targeted detection of CRP in human serum samples was achieved by the sandwich-type immunosensor based on the ECL-RET mechanism with a 0.26 pg mL^-1 detection limit. The electro-activated hybrids of Cu₃(HHTP)₂ and ECL emitters provide a new sensing strategy for the high-sensitivity detection of disease markers.

Lateral Flow Immunoassay for Proteins

Protein biomarkers are useful for disease diagnosis. Identification thereof using in vitro diagnostics such as lateral flow immunoassays (LFIAs) has attracted considerable attention due to their low cost and ease of use especially in the point of care setting. Current challenges, however, do remain with respect to material selection for each component in the device and the synergistic integration of these components to display detectable signals. This review explores the principle of LFIA for protein biomarkers, device components including biomaterials and labeling methods. Medical applications and commercial status are examined as well. This review highlights critical methodologies in the development of new LFIAs and their role in advancing healthcare worldwide.

Dry Chemistry-Based Bipolar Electrochemiluminescence Immunoassay Device for Point-of-Care Testing of Alzheimer-Associated Neuronal Thread Protein

In this study, we developed, for the first time, a novel dry chemistry-based bipolar electrochemiluminescence (ECL) immunoassay device for point-of-care testing (POCT) of Alzheimer-associated neuronal thread protein (AD7c-NTP), where the ECL signals were automatically collected and analyzed after the sample and buffer solutions were manually added onto the immunosensor. The proposed immunoassay device contains an automatic ECL analyzer and a dry chemistry-based ECL immunosensor fabricated with a screen-printed fiber material-based chip and a three-dimensional (3D)-printed shell. Each pad of the fiber material-based chip was premodified with certain reagents for immunoreaction and then assembled to form the ECL immunosensor. The self-enhanced ECL of the Ru(II)-poly-l-lysine complex and the lateral flow fiber material-based chip make the addition of coreactants and repeated flushing unnecessary. Only the sample and buffer solutions are added to the ECL immunosensor, and the process of ECL detection can be completed in about 6 min using the proposed automatic ECL analyzer. Under optimized conditions, the linear detection range for AD7c-NTP was 1 to 10⁴ pg/mL, and the detection limit was 0.15 pg/mL. The proposed ECL immunoassay device had acceptable selectivity, stability, and reproducibility and had been successfully applied to detect AD7c-NTP levels in human urine. In addition, the accurate detection of AD7c-NTP and duplex detection of AD7c-NTP and apolipoprotein E ε4 gene were also validated. It is believed that the proposed ECL immunoassay device may be a candidate for future POCT applications.

Electrostatic Interaction-Induced Aggregation-Induced Emission-Type AgAu Bimetallic Nanoclusters as a Highly Efficient Electrochemiluminescence Emitter for Ultrasensitive Detection of Glial Fibrillary Acidic Protein

Herein, the aggregation-induced emission (AIE)-type carboxymethyl chitosan (CMCS)@6-aza-2-thiothymine (ATT) templated AgAu bimetallic nanoclusters (CMCS@ATT-AgAu BMNCs) with superior electrochemiluminescence (ECL) emission were first synthesized to construct a biosensor for the ultrasensitive detection of glial fibrillary acidic protein (GFAP). Impressively, unlike the traditional AIE-type bimetallic nanoclusters (BMNCs) obtained by complicated multi-step synthesis, the AIE-type CMCS@ATT-AgAu BMNCs were prepared by the electrostatic interaction between the negatively charged ATT and positively charged CMCS, in which the molecule ATT was served as a capping and reducing agent of bimetal ions. In addition, a rapidly moving cholesterol labeled DNA walker was constructed to move freely on the lipid bilayer to increase its moving efficiency, and the well-regulated DNA was intelligently designed to further improve its walking efficiency for rapid and ultrasensitive detection of GFAP with a limit of detection (LOD) as low as 73 ag/mL. This strategy proposed an avenue to synthesize highly efficient BMNCs-based ECL emitters, which have great potential in ultrasensitive biosensing for early diagnosis of diseases.

Smartphone-based microplate reader for high-throughput quantitation of disease markers in serum

Herein, a smartphone-based portable reader with integrated optics for standard microtiter plates (96 wells) has been designed and demonstrated for high-throughput quantitation of validated biomarkers in serum. The customized optical attachment was simply constructed with a convex lens and a light source, by which the transmitted light through a 96-well microtiter plate was converged for imaging with a smartphone, so that accurate and wide-range reading of the plate can be achieved. More importantly, relying on the digitized colorimetric analysis of the obtained images, concentrations of various biomarkers can be determined directly using the customized mobile app. A set of validated biomarkers for inflammation and infection, C-reactive protein (CRP), serum amyloid A (SAA), and procalcitonin (PCT) have been quantitated with this new system; both the response ranges and limits of detection meet the requirement of clinical tests. The consistency with the results obtained using a commercial microplate reader proves its reliability and precision, augments its potential as a point-of-care diagnostic device for on-site testing or resource-limited settings.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

DNA Tetrahedron-Based Valency Controlled Signal Probes for Tunable Protein Detection

Combined detection of multiple markers related to the same disease could improve the accuracy of disease diagnosis. However, the abundance levels of multiple markers of the same disease varied widely in real samples, making it difficult for the traditional detection method to meet the requirements of a wide detection range. Herein, three kinds of cardiac biomarkers, cardiac troponin I (cTnI), myoglobin (Myo), and C-reaction protein (CRP), which were from the pM level to the μM level in real samples, were selected as model targets. Valency-controlled signal probes based on DNA tetrahedron nanostructures (DTNs) and platinum nanoparticles (PtNPs) were constructed for tunable cardiac biomarker detection. PtNPs with high horseradish peroxidase-like activity and stability served as signal molecules, and DTNs with unique spatial structure and sequence specificity were used for precisely controlling the number of connected PtNPs. By controlling the number of PtNPs connected to DTNs, monovalent, bivalent, and trivalent signal probes were obtained and were used for the detection of cardiac markers in different concentration ranges. The limit of detection of cTnI, Myo, and CRP was 3.0 pM, 0.4 nM, and 6.7 nM, respectively. Furthermore, it performed satisfactorily for the detection of cardiac markers in 10% human serum. It was anticipated that the design of valency-controlled signal probes based on DTNs and nanozymes could be extended to the construction of other multi-target detection platforms, thus providing a basis for the development of a new precision medical detection platform.

Fabrication of a Disposable Electrochemical Immunosensor Based on Nanochannel Array Modified Electrodes and Gated Electrochemical Signals for Sensitive Determination of C-Reactive Protein

Sensitive determination of C-reactive protein (CRP) is of great significance because it is an early indicator of inflammation in cardiovascular disease and acute myocardial infarction. A disposable electrode with an integrated three-electrode system (working, reference, and counter electrodes) has great potential in the detection of biomarkers. In this work, an electrochemical immunosensing platform was fabricated on disposable and integrated screen-printed carbon electrode (SPCE) by introducing nanochannel arrays and gated electrochemical signals, which can achieve the sensitive detection of CRP in serum. To introduce active reactive groups for the fabrication of immuno-recognitive interface, vertically-ordered mesoporous silica-nanochannel film (VMSF) with rich amino groups (NH₂-VMSF) was rapidly grown by electrochemical assisted self-assembly (EASA). The electrochemically reduced graphene oxide (ErGO) synthesized in situ during the growth of NH₂-VMSF was used as a conductive adhesive glue to achieve stable bonding of the nanochannel array (NH₂-VMSF/ErGO/SPCE). After the amino group on the outer surface of NH₂-VMSF reacted with bifunctional glutaraldehyde (GA/NH₂-VMSF/ErGO/SPCE), the converted aldehyde surface was applied for covalent immobilization of the recognitive antibody (Ab) followed with the blocking of the non-specific sites. The fabricated immunosensor, Ab/GA/NH₂-VMSF/ErGO/SPCE, enables sensitive detection of CRP in the range from 10 pg/mL to 100 ng/mL with low limit of detection (LOD, 8 pg/mL, S/N = 3). The immunosensor possessed high selectivity and can realize reliable determination of CRP in human serum.

Mask assistance to colorimetric sniffers for detection of Covid-19 disease using exhaled breath metabolites

According to World Health Organization reports, large numbers of people around the globe have been infected or died for Covid-19 due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Researchers are still trying to find a rapid and accurate diagnostic method for revealing infected people by low viral load with the overriding goal of effective diagnostic management. Monitoring the body metabolic changes is known as an effective and inexpensive approach for the evaluation of the infected people. Here, an optical sniffer is introduced to detect exhaled breath metabolites of patients with Covid-19 (60 samples), healthy humans (55 samples), and cured people (15 samples), providing a unique color pattern for differentiation between the studied samples. The sniffer device is installed on a thin face mask, and directly exposed to the exhaled breath stream. The interactions occurring between the volatile compounds and sensing components such as porphyrazines, modified organic dyes, porphyrins, inorganic complexes, and gold nanoparticles allowing for the change of the color, thus being tracked as the sensor responses. The assay accuracy for the differentiation between patient, healthy and cured samples is calculated to be in the range of 80%-84%. The changes in the color of the sensor have a linear correlation with the disease severity and viral load evaluated by rRT-PCR method. Interestingly, comorbidities such as kidney, lung, and diabetes diseases as well as being a smoker may be diagnosed by the proposed method. As a powerful detection device, the breath sniffer can replace the conventional rapid test kits for medical applications.

Cluster-Dominated Electrochemiluminescence of Tertiary Amines in Polyethyleneimine Nanoparticles: Mechanism Insights and Sensing Application

Designing and screening highly efficient and cost-effective luminophores have always been a challenge to develop sensitive electrochemiluminescence (ECL) biosensors. Herein, polyethyleneimine nanoparticles (PEI NPs), a kind of nonconjugated polymer (NCP) NPs with tertiary amine clusters, were developed as an ECL luminophore. Specifically, PEI NPs were synthesized by a one-step hydrothermal method using PEI and formaldehyde. The properties of PEI NPs were investigated in detail using photochemical and electrochemical techniques. The results showed cluster-dominated luminescence of tertiary amines in PEI NPs via "through-space conjugation". This non-negligible ECL performance (at 631 nm) was also verified by the initiated reduction-oxidation process. With persulfate as a coreactant, PEI NPs acted as both the luminophore and coreaction accelerator to enhance the ECL intensity remarkably, which was eightfold higher than that of isolated PEI. Moreover, choosing dopamine as the model target, a highly sensitive "signal off" ternary ECL sensor was constructed utilizing PEI NPs as the luminophore. Dopamine could be oxidized to benzoquinone at the sensing interface, quenching the signal via ECL energy transfer. Free from any signal amplification, the proposed sensor achieved a low detection limit (4.3 nM) for target monitoring with good selectivity and stability. This strategy not only provides a unique perspective for designing novel efficient and facile ECL luminophores of tertiary amines but also broadens the biological application of NCP NPs.

Nanoparticles in the diagnosis and treatment of vascular aging and related diseases

Aging-induced alternations of vasculature structures, phenotypes, and functions are key in the occurrence and development of vascular aging-related diseases. Multiple molecular and cellular events, such as oxidative stress, mitochondrial dysfunction, vascular inflammation, cellular senescence, and epigenetic alterations are highly associated with vascular aging physiopathology. Advances in nanoparticles and nanotechnology, which can realize sensitive diagnostic modalities, efficient medical treatment, and better prognosis as well as less adverse effects on non-target tissues, provide an amazing window in the field of vascular aging and related diseases. Throughout this review, we presented current knowledge on classification of nanoparticles and the relationship between vascular aging and related diseases. Importantly, we comprehensively summarized the potential of nanoparticles-based diagnostic and therapeutic techniques in vascular aging and related diseases, including cardiovascular diseases, cerebrovascular diseases, as well as chronic kidney diseases, and discussed the advantages and limitations of their clinical applications.

Recent Advances in Silica-Nanomaterial-Assisted Lateral Flow Assay

Lateral flow assays (LFAs) have attracted much attention as rapid and affordable point-of-care devices for medical diagnostics. The global SARS-CoV-2 pandemic has further highlighted the importance of LFAs. Many efforts have been made to enhance the sensitivity of LFAs. In recent years, silica nanomaterials have been used to either amplify the signal of label materials or provide stability, resulting in better detection performance. In this review, the recent progress of silica-nanomaterial-assisted LFAs is summarized. The impact of the structure of silica nanomaterials on LFA performance, the challenges and prospects in this research area are also discussed.

Dual-Modal Immunochromatographic Test for Sensitive Detection of Zearalenone in Food Samples Based On Biosynthetic Staphylococcus aureus-Mediated Polymer Dot Nanocomposites

The rapid detection of toxins is of great significance to food security and human health. In this work, a dual-modality immunochromatographic test (DICT) mediated by Staphylococcus aureus (SA)-biosynthesized polymer dots (SABPDs) was constructed for sensitive monitoring of zearalenone (ZEN) in agro products. The SABPDs as potent microorganism nanoscaffolds with excellent solubility, brightness, and stability were ingeniously fabricated employing hydroquinone and SA as precursors in the Schiff base reaction and a self-assembly technique. Thanks to the fact that they not only preserved an intact microsphere for loading Fc regions of monoclonal antibodies (mAbs) and the affinity of their labeled mAbs to antigen but also generated superb colorimetric-fluorescent dual signals, the versatile SABPDs manifested unique possibilities as the new carriers for dual-readout ICT with remarkable enhancement in sensitivity in ZEN screening (limit of detection = 0.036 ng/mL, which was 31-fold lower than that of traditional gold nanoparticle-based ICT). Ultimately, the proposed immunosensor performed well in millet and corn samples with satisfactory recoveries, demonstrating its potential for point-of-care testing. This work offers a bio-friendly strategy for biosynthesizing cell-based PD vehicles with bimodal signals for food safety analysis.

Biomimetic -mineralized multifunctional nanoflowers for anodic-stripping voltammetric immunoassay of rehabilitation-related proteins

C-reactive proteins (CRPs; an acute-phase protein) in patients with initial acute cerebral infarction neurological rehabilitation prediction have a significant correlation. In this work, a simple and sensitive anodic-stripping voltammetric (ASV) immunosensing system was innovatively designed for the quantitative screening of target CRPs using biomimetic-mineralized bifunctional antibody-Cu₃(PO₄)₂ nanoflowers as molecular tags. In this system, a monoclonal anti-CRP antibody-anchored microtiter plate was utilized to specifically capture target CRPs from the sample. For detection, a sandwiched immunoreaction mode was employed with the antibody-Cu₃(PO₄)₂ nanoflowers in the presence of analytes. Subsequent ASV measurement of copper ions (Cu²⁺) released under acidic conditions from the bifunctional nanoflowers was conducted at an in situ prepared mercury film electrode. The introduction of hybrid nanoflowers greatly increased the loading amount of copper ions on the molecular tag, thereby amplifying the detectable signal of electrochemical immunoassay. Meanwhile, factors influencing the analytical properties of the electrochemical immunoassay were investigated in detail. By combining the high-efficiency nanohybrids with signal amplification, the dynamic concentration range of electrochemical immunoassay spanned from 0.01 ng mL^-1 to 100 ng mL^-1 toward the target CRP. The limit of detection was calculated to be 0.0079 ng mL^-1 at 3S_blank criterion. Intra- and interassay imprecisions (relative standard deviations: RSDs) were less than or equal to 6.72%. Good anti-interference ability, long-term storage stability, and acceptable accuracy for the evaluation of human serum specimens were observed during a series of procedures to determine the target protein. In addition, the bifunctional nanoflower-based immunosensing system offers promise for the simple, cost-effective analysis of disease-related proteins.

Advances in the Application of Nanomaterials as Treatments for Bacterial Infectious Diseases

Bacteria-targeting nanomaterials have been widely used in the diagnosis and treatment of bacterial infectious diseases. These nanomaterials show great potential as antimicrobial agents due to their broad-spectrum antibacterial capacity and relatively low toxicity. Recently, nanomaterials have improved the accurate detection of pathogens, provided therapeutic strategies against nosocomial infections and facilitated the delivery of antigenic protein vaccines that induce humoral and cellular immunity. Biomaterial implants, which have traditionally been hindered by bacterial colonization, benefit from their ability to prevent bacteria from forming biofilms and spreading into adjacent tissues. Wound repair is improving in terms of both the function and prevention of bacterial infection, as we tailor nanomaterials to their needs, select encapsulation methods and materials, incorporate activation systems and add immune-activating adjuvants. Recent years have produced numerous advances in their antibacterial applications, but even further expansion in the diagnosis and treatment of infectious diseases is expected in the future.

Recent Development of Nanomaterials-Based Cytosensors for the Detection of Circulating Tumor Cells

The accurate analysis of circulating tumor cells (CTCs) holds great promise in early diagnosis and prognosis of cancers. However, the extremely low abundance of CTCs in peripheral blood samples limits the practical utility of the traditional methods for CTCs detection. Thus, novel and powerful strategies have been proposed for sensitive detection of CTCs. In particular, nanomaterials with exceptional physical and chemical properties have been used to fabricate cytosensors for amplifying the signal and enhancing the sensitivity. In this review, we summarize the recent development of nanomaterials-based optical and electrochemical analytical techniques for CTCs detection, including fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence, electrochemistry, electrochemiluminescence, photoelectrochemistry and so on.