CDs assembled metal-organic framework: Exogenous coreactant-free biosensing platform with pore confinement-enhanced electrochemiluminescence

Engineering multi-activator-encoded DNA nanonet to accelerate CRISPR-Cas12a activation for rapid and sensitive electrochemiluminescence bioassay

Despite CRISPR-associated (Cas) nucleases have emerged as a versatile and highly programmable tool for biosensing and molecular diagnostics, the efficient manipulation of targeted CRISPR-Cas12a activation requires further improvement. Herein, we engineered a target-response DNA nanodevice called multi-activator-encoded DNA nanonet (MAIDA) which displayed efficient manipulation of CRISPR-Cas12a trans-activity for apurinic/apyrimidinic endonuclease 1 (APE1) activity monitoring. The MAIDA nanodevice was constructed by multi-activator loops (MA loops) encoded with three activator sequences and target-response loops (TR loops) encoded with three abasic sites to generate interlocked DNA nanonet. Notably, the activator sequences on MA loop were pre-hybridized with TR loop, which not only generate AP sites but also inhibit the CRISPR-Cas12a activation in the initial state. When APE1 is present, the AP sites on the MAIDA nanodevice were recognized and cleaved to the release of MA loops, which could activate the trans-cleavage of CRISPR-Cas12a and then output the signal through electrochemiluminescence (ECL) biosensor. Finally, the experimental results demonstrate that the MA loops increase the ECL response of CRISPR-Cas12a by 1.5-fold compared with the conventional single-linear activators, and the limit of detection (LOD) of APE1 by the proposed biosensor is 1.46 × 10-10 U/μL. The MAIDA nanodevice promoted the efficient manipulation of targeted CRISPR-Cas12a activation with high sensitivity and selectivity, which provided a promising tool for enhancing DNA-based sensing and analytical applications.

Green biomass carbon points with efficient broad-spectrum antibacterial activity and widespread application

With low toxicity and good biocompatibility, carbon dots (CDs) are widely used in the fields of biosensing and drug delivery. In recent years, they have demonstrated excellent antimicrobial properties, thus becoming another research hotspot in the antimicrobial field. However, most of the studies showed that CDs were effective in inhibiting Gram-positive bacteria but ineffective against Gram-negative bacteria. In this study, macadamia nutshell (MNS)-CDs were prepared from the hard shells of macadamia nuts by a one-step hydrothermal method, and their appearance, morphology, structural composition, antimicrobial properties, and toxicity were investigated. The results showed that the MNS-CDs were spherical particles with an average diameter of about 4.25 nm, with hydrophilic groups, a hemolysis rate of less than 2%, good biocompatibility, and excellent antimicrobial properties against both Gram-negative and Gram-positive bacteria. The antimicrobial mechanism of these materials was also investigated. The inhibition of Gram-negative bacteria by MNS-CDs was mainly due to electrostatic interactions, while the inhibition of Gram-positive bacteria was mainly based on activated oxygen sterilization. Furthermore, MNS-CDs achieved good antimicrobial effects when applied in the fields of water purification, plates, fabrics, and food packaging, indicating that the prospects of their broad application are good.

Programmable spherical nucleic acids integrated with MOF-confined copper nanoclusters facilitate electrochemiluminescence detection of prostate-specific biomarkers

Alpha-methylacyl-CoA racemase (AMACR) is a promising prostate cancer biomarker due to its high specificity in distinguishing prostate cancer from benign prostatic diseases. However, its low abundance in biological environments presents a significant detection challenge. To address this, we developed an innovative all-in-one s̲pherical n̲ucleic a̲cid (SNA) platform for highly sensitive and selective electrochemiluminescence (ECL) detection of AMACR. The SNAs incorporate two types of ice-cream probes (IC probes), each consisting of interlocked hairpins and circular templates. Specifically, the all-in-one SNAs were elaborately designed to achieve key three functions: (i) the arrangement of IC probes on magnetic nanoparticle interfaces creates a spatially confined environment, promoting rapid interactions, and enhances AMACR conversion efficiency; (ii) the integrated templates and primers within the IC probes facilitate rolling circle amplification (RCA), resulting in exponential signal amplification; and (iii) the products generated through RCA serve as activators for the CRISPR/Cas12a system, remarkably improving its activation efficiency. Upon AMACR activation of the aptamer-prelocked DNA walker, the all-in-one SNAs were specifically driven to initiate RCA, generating exponentially amplified activators to effectively activate the CRISPR/Cas12a system. Additionally, we established a novel ECL nano-complex using a zinc-metal-organic framework loaded with Cu nanoclusters for signal output. This platform demonstrates exceptional sensitivity and specificity for detecting low-abundance biomarkers, offering significant potential for advancing clinical diagnostics.

In Situ "Confocal" Electrochemiluminescence 3D Imaging: From Cell to Tissue Section

Endowing electrochemiluminescence (ECL) imaging technique with three-dimensional (3D) resolution to investigate specimens at varying axial depths poses a challenging yet significant objective. Herein, a "confocal" 3D ECL imaging method was developed using luminol as ECL probe, in which excited luminophore was formed in the vicinity of electrode surface through homogeneous chemical reactions between oppositely diffusing ECL precursors, luminol diazaquinone intermediate (L), and hydrogen peroxide (H2O2), confining the ECL emission in a thin plane (ECL focal plane) parallel to electrode surface at their intersection. The regulating ability of electrochemical method on the reaction fluxes of L and H2O2 was validated, regulating the axial location of the ECL focal plane from 0 to 63 µm, which can even extend to 400 µm by using the stable coreactant of ClO-. Leveraging the optical sectioning capability of the ECL focal plane, the "confocal" 3D ECL imaging method was applied to bioimaging, from cells to tissue sections. It revealed cellular morphology changes during cell polarity establishment and the heterogeneous distribution of complex tubule structure in kidney tissue sections. The optical sectioning capability of "confocal" 3D ECL imaging makes it a powerful tool for studying complex biological samples.

Metal Nanocluster-Based Biosensors for DNA Detection

The early detection of genetic diseases is a critical need in modern medicine, underscoring the importance of developing deoxyribonucleic acid (DNA) biosensors. In recent years, metal nanoclusters (MNCs) have demonstrated significant potential as biosensors for DNA detection due to their ultra-small size, excellent photostability, bright photoluminescence, low toxicity and other outstanding properties. This review firstly discusses the characteristics of MNCs, which are effective in the early diagnosis of DNA diseases. Subsequently, different synthesis methods of MNCs are introduced. In the following section, DNA sensors based on different types of MNCs and their respective detection mechanisms are discussed in detail. Finally, the opportunities and challenges faced by DNA sensors based on MNCs are analyzed.

Advanced Ligase Chain Reaction Strategy to Generate a Circular DNA Walker for Electrochemiluminescent Detection of Single Nucleotide Polymorphism

Single nucleotide polymorphism (SNP) primarily refers to DNA sequence polymorphism caused by variations in a single nucleotide, which is closely associated with many diseases such as genetic disorders and tumors. However, trace DNA mutants typically exist in a large pool of wild-type DNA, making it challenging to establish accurate and sensitive approaches for SNP detection. Herein, we developed an advanced ligase chain reaction (LCR) strategy to output the circular DNA walker for signal amplification, which realized accuracy and sensitive SNP detection based on the electrochemiluminescent (ECL) platform. Unlike the general LCR system that utilizes two sets of short single-stranded DNA (ssDNA) primers to generate double-stranded DNA amplification products, we ingeniously designed a long single-stranded DNA primer to replace one set of short ssDNA primers, allowing for the generation of circular DNA products upon complementing the target. Noticeably, the circular DNA serves as a DNA walker that can be easily purified by nucleases to eliminate unreacted primers and byproducts, significantly improving accuracy and sensitivity. Then, the circular DNA walker moved along a linearly ordered DNA quenching probe track modified on the ECL sensing interface, restoring the ECL signals by cleaving the quenching probes labeled on the DNA track with the help of apurinic/apyrimidinic endonuclease 1. Employing the p53 gene as a model, we realized the sensitive detection of mutant p53 in the range from 10 aM to 10 pM, with a detection limit of 6 aM, providing a promising platform for SNP detection.

Application of CRISPR/Cas12a in miRNA-155 detection: A novel homogeneous electrochemiluminescence biosensor

BACKGROUND

MicroRNAs (miRNAs) are important non-coding RNA entities that affect gene expression and function by binding to target mRNAs, leading to degradation of the mRNAs or inhibiting their translation. MiRNAs are widely involved in a variety of biological processes, such as cell differentiation, development, metabolism, and apoptosis. In addition, miRNAs are associated with many diseases, including cancer. However, conventional detection techniques often suffer from shortcomings such as low sensitivity, so we need to develop a rapid and efficient detection strategy for accurate detection of miRNAs.

RESULTS

We have developed an innovative homogeneous electrochemiluminescence (ECL) biosensor. This biosensor employs CRISPR/Cas12a gene editing technology for accurate and efficient detection of microRNA (miRNA). Compared to conventional technologies, this biosensor employs a unique homogeneous detection format that eliminates laborious probe fixation steps and greatly simplifies the detection process. By using two amplification techniques - isothermal amplification and T7 RNA polymerase amplification - the biosensor improves the sensitivity and specificity of the assay, providing excellent detection performance in the assay. This makes it possible to evaluate miRNA directly from a variety of biological samples such as cell lysates and diluted human serum. Experimental results convincingly demonstrate the extraordinary performance of this biosensor, including its extremely low detection limit of 1.27 aM, high sensitivity, reproducibility and stability.

SIGNIFICANCE

The application of our constructed sensor in distinguishing between cancerous and non-cancerous cell lines highlights its potential for early cancer detection and monitoring. This innovative approach represents a major advancement in the field of miRNA detection, providing a user-friendly, cost-effective, and sensitive solution with broad implications for clinical diagnosis and patient care, especially in point-of-care settings.

Nanoconfined Silver Nanoclusters Combined with X-Shaped DNA Recognizer-Triggered Cascade Amplification for Electrochemiluminescence Detection of APE1

Apurinic/apyrimidinic endonuclease 1 (APE1), as a vital base excision repair enzyme, is essential for maintaining genomic integrity and stability, and its abnormal expression is closely associated with malignant tumors. Herein, we constructed an electrochemiluminescence (ECL) biosensor for detecting APE1 activity by combining nanoconfined ECL silver nanoclusters (Ag NCs) with X-shaped DNA recognizer-triggered cascade amplification. Specifically, the Ag NCs were prepared and confined in the glutaraldehyde-cross-linked chitosan hydrogel network using the one-pot method, resulting in a strong ECL response and exceptional stability in comparison with discrete Ag NCs. Furthermore, the self-assembled X-shaped DNA recognizers were designed for APE1 detection, which not only improved reaction kinetics due to the ordered arrangement of recognition sites but also achieved high sensitivity by utilizing the recognizer-triggered cascade amplification of strand displacement amplification (SDA) and DNAzyme catalysis. As expected, this biosensor achieved sensitive ECL detection of APE1 in the range of 1.0 × 10-3 U·μL-1 to 1.0 × 10-10 U·μL-1 with the detection limit of 2.21 × 10-11 U·μL-1, rendering it a desirable approach for biomarker detection.

Precision miRNA profiling: Electrochemiluminescence powered by CRISPR-Cas13a and hybridization chain reaction

The article details a groundbreaking platform for detecting microRNAs (miRNAs), crucial biomolecules involved in gene regulation and linked to various diseases. This innovative platform combines the CRISPR-Cas13a system's precise ability to specifically target and cleave RNA molecules with the amplification capabilities of the hybridization chain reaction (HCR). HCR aids in signal enhancement by creating branched DNA structures. Additionally, the platform employs electrochemiluminescence (ECL) for detection, noted for its high sensitivity and low background noise, making it particularly effective. A key application of this technology is in the detection of miR-17, a biomarker associated with multiple cancer types. It exhibits remarkable detection capabilities, characterized by low detection limits (14.38 aM) and high specificity. Furthermore, the platform's ability to distinguish between similar miRNA sequences and accurately quantify miR-17 in cell lysates underscores its significant potential in clinical and biomedical fields. This combination of precise targeting, signal amplification, and sensitive detection positions the platform as a powerful tool for miRNA analysis in medical diagnostics and research.

Emerging trends in CDs@hydrogels composites: from materials to applications

Carbon dots (CDs) are nanoscale carbon materials with unique optical properties and biocompatibility. Their applications are limited by their tendency to aggregate or oxidize in aqueous environments. Turning weakness to strengths, CDs can be incorporated with hydrogels, which are three-dimensional networks of crosslinked polymers that can retain large amounts of water. Hydrogels can provide a stable and tunable matrix for CDs, enhancing their fluorescence, stability, and functionality. CDs@hydrogels, known for their ease of synthesis, strong binding capabilities, and rich surface functional groups, have emerged as promising composite materials. In this review, recent advances in the synthesis and characterization of CDs@hydrogels, composite materials composed of CDs and various types of natural or synthetic hydrogels, are summarized. The potential applications of CDs@hydrogels in fluorescence sensing, adsorption, drug delivery, antibacterial activity, flexible electronics, and energy storage are also highlighted. The current challenges and future prospects of CDs@hydrogels systems for the novel functional materials are discussed.

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) modified metal-organic frameworks boosting carbon dots electrochemiluminescence emission for sensitive miRNA detection

Highly efficient luminescent materials play an important role in electrochemiluminescence (ECL) biosensing systems. Herein, the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified carbon dots (CDs)/zeolitic imidazolate framework-8 (ZIF-8) compositing metal-organic frameworks (MOFs) materials with excellent luminescence performance were prepared as the ECL emitters for biosensing application. In this novel ternary composites, CDs were used as emitters, ZIF-8 was used as a carrier, and the luminescent performance was finally improved by introducing PEDOT:PSS to improve the conductivity of the nanomaterials. As a result, CDs/PEDOT:PSS/ZIF-8 exhibited an approximately 8 times ECL intensity compared to CDs alone. By further modifying with AuNPs, the enhancement factor reached ≈10 in reference to the individual CDs. After combining with a DNAzyme-based two-cycle target amplification principle, an ECL biosensor was constructed to achieve high-sensitivity detection of miRNA-21 with a detection limit of 50 aM. The biosensor also demonstrated desirable selectivity, excellent stability, and quantitative ability for human serum target detection. Overall, these findings not only provide a promising pathway for high luminous efficiency ECL emitters synthesis, but also provide a platform for ultrasensitive miRNA sensing.

A pH responsive tannic acid/quaternized carboxymethyl chitosan/oxidized sodium alginate hydrogels for accelerated diabetic wound healing and real-time monitoring

Treatment of diabetic wounds is a major clinical issue. Diabetic wound dressings have higher requirements for anti-oxidant, antibacterial and wound monitoring properties compared to conventional wound dressings. In this study, a novel tannic acid (TA)/quaternized carboxymethyl chitosan (QCMCS)/oxidized sodium alginate (OSA)@carbon quantum dots (CQD) (TA/QCMCS/OSA@CQD) hydrogels for promoting diabetic wound healing and real-time monitoring have been developed. The TA/QCMCS/OSA@CQD hydrogels exhibited excellent self-healing, antibacterial and antioxidant properties. Besides, these hydrogels possessed good biocompatibility and effective hemostasis in a mouse liver injury model and significantly facilitated the healing process in a diabetic wound model. In addition, these hydrogels can reliable and timely measure the diabetic wound pH information by collecting image signals of hydrogels to monitor the healing status. Therefore, the pH responsive TA/QCMCS/OSA@CQD hydrogels could be utilized as wound dressing for promoting diabetic wound healing and real-time monitoring.

Highly sensitive and simultaneous detection of ascorbic acid, dopamine, and uric acid using Pt@g-C3N4/N-CNTs nanocomposites

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is crucial for understanding and managing various illnesses. In this research, Pt@g-C3N4 nanoparticles were synthesized via hydrothermal method and combined with N-doped carbon nanotubes (N-CNTs). The Pt@g-C3N4/N-CNTs-modified glassy carbon (GC) electrode was fabricated as an electrochemical sensor for the determination of AA, DA, and UA. The linear response range of AA, DA, and UA in the optimal condition was 100-3,000 μM, 1-100 μM, and 2-215 μM boasting a low detection limit (S/N = 3) of 29.44 μM (AA), 0.21 μM (UA), and 2.99 μM (DA), respectively. Additionally, the recoveries of AA, DA, and UA in serum sample were 100.4%-106.7%. These results corroborate the feasibility of the proposed method for the simultaneous, sensitive, and reliable detection of AA, DA, and UA. Our Pt@g-C3N4/N-CNTs/GC electrode can provide a potential strategy for disease diagnosis and health monitoring in clinical settings.

Dual-microRNA-Controlled Electrochemiluminescence Biosensor for Breast Cancer Diagnosis and Supplemental Identification of Breast Cancer Metastasis

Breast cancer remains the most frequently diagnosed cancer globally, and the metastasis of this malignancy is the primary cause of mortality in breast cancer patients. Hence, prompt diagnosis and timely detection of metastatic breast cancer are critical for effective therapeutic intervention. Both progression and metastasis of this malignancy are closely associated with aberrant expression of specific microRNAs (miRNAs) and enzymes. To facilitate breast cancer diagnosis and concomitant identification of metastatic breast cancer, we have engineered an innovative electrochemiluminescence (ECL)-based sensing platform integrated with enzyme-free DNA amplification circuits for dual functionality. Specifically, microRNA-21 (miR-21) is employed as a biomarker for breast cancer, and miR-21 induces the quenching of the ECL signal from luminophores via a strategically designed catalytic three-hairpin assembly (CTHA) circuit. Subsequently, miR-105 levels are measured via toehold-mediated strand displacement reactions (TSDR). Here, miR-105 restores the initially quenched ECL signal, enabling the assessment of the metastatic propensity. Our experimental data demonstrate that the devised ECL biosensor offers broad linear detection ranges and low detection limits for both miR-21 and miR-105. Importantly, our novel platform was also successfully validated by using cellular and serum samples. This biosensor not only discriminates breast cancer cell lines MCF-7 and MDA-MB-231 from nonbreast cancer cells like HepG2, TPC-1, and HeLa, but it also distinguishes between malignant MCF-7 and metastatic MDA-MB-231 cells. Consequently, our novel approach holds significant promise for clinical applications and precise cancer screening.

Rational Design of DNA Hydrogels Based on Molecular Dynamics of Polymers

In recent years, DNA has emerged as a fascinating building material to engineer hydrogel due to its excellent programmability, which has gained considerable attention in biomedical applications. Understanding the structure-property relationship and underlying molecular determinants of DNA hydrogel is essential to precisely tailor its macroscopic properties at molecular level. In this review, the rational design principles of DNA molecular networks based on molecular dynamics of polymers on the temporal scale, which can be engineered via the backbone rigidity and crosslinking kinetics, are highlighted. By elucidating the underlying molecular mechanisms and theories, it is aimed to provide a comprehensive overview of how the tunable DNA backbone rigidity and the crosslinking kinetics lead to desirable macroscopic properties of DNA hydrogels, including mechanical properties, diffusive permeability, swelling behaviors, and dynamic features. Furthermore, it is also discussed how the tunable macroscopic properties make DNA hydrogels promising candidates for biomedical applications, such as cell culture, tissue engineering, bio-sensing, and drug delivery.

Universal Signal Switch Based on a Mesostructured Silica Xerogel-Confined ECL Polymer for Epigenetic Quantification

The development of a highly accurate electrochemiluminescence (ECL) signal switch to avoid nonspecific stimulus responses is currently a significant and challenging task. Here, we constructed a universal signal switch utilizing a luminophore-quencher pair of mesostructured silica xerogel-confined polymer and gold nanoparticles (Au NPs) that can accurately detect low-abundance epigenetic markers in complex sample systems. Notably, the ECL polymer encapsulated in mesostructured silica xerogel acts as a luminophore, which demonstrated a highly specific dependence on the Au NPs-mediated energy transfer quenching. To demonstrate the feasibility, we specifically labeled the 5-hydroxymethylcytosine (5hmC) site on the random sequence using a double-stranded (dsDNA) tag that was skillfully designed with the CRISPR/Cas12a activator and recombinant polymerase amplification (RPA) template. After amplification by RPA, a large amount of dsDNA tag was generated as the activator to initiate the trans-cleavage activity of CRISPR/Cas12a and subsequently activate the signal switch, allowing for precise quantification of 5hmC. The ECL signal switch improves the stability of the luminophore and prevents nonspecific stimulus responses, providing a new paradigm for constructing high-precision biosensors.

A luminescent MOF-based nonenzymatic probe for colorimetric/photothermal/fluorescence triple-mode assay of uric acid in body fluids

Monitoring the levels of uric acid (UA) in body fluids is of great significance in the clinical diagnosis and therapy of related diseases. Herein, a novel nanocomposite R6G@Fe-MOF based nonenzymatic probe is presented to provide a ratiometric fluorescent, colorimetric, and photothermal triple read-out signal for the visual, sensitive, and convenient assay of UA. The framework structure of the in situ encapsulated R6G@Fe-MOF is found to decompose upon the addition of UA, resulting in the reduction of Fe3+ to Fe2+. This reduction will lead to a rapid increase in fluorescence emission (FL) at 430 nm. Simultaneously, the FL at 573 nm will decrease remarkably due to the inner filter effect (IFE) between UA and R6G@Fe-MOF. Furthermore, the reaction of the generated Fe2+ with potassium ferricyanide (K3 [Fe(CN)6]) can in situ generate Prussian blue (PBNPs) with outstanding color and photothermal properties, which allow for easy colorimetric and photothermal signal readout. The detection limits (LOD) for the colorimetric, fluorometric and photothermal detection are low at 1.68 μM, 0.236 μM, and 1.32 μM respectively. Ultimately, it is successfully employed to determine UA in urine, serum, and saliva, yielding satisfactory results. The constructed R6G@Fe-MOF sensor provides a simple, sensitive, and accurate determination of UA that can be tailored to meet the needs of various applications, and also provides new perspectives for the design and development of versatile sensors for diverse uses.

One master and two servants: One Zr(Ⅳ) with two ligands of TCPP and NH2-BDC form the MOF as the electrochemiluminescence emitter for the biosensing application

Here we put forward an innovative "one master and two servants" strategy for enhancing the ECL performance. A novel ECL luminophore named Zr-TCPP/NH2-BDC (TCPP@UiO-66-NH2) was synthesized by self-assembly of meso-tetra(4-carboxyphenyl)porphine (TCPP) and 4-aminobenzoic acid (NH2-BDC) with Zr clusters. TCPP@UiO-66-NH2 has a porous structure and a highly ordered structure, which allows the molecular motion of TCPP to be effectively confined, thereby inhibiting nonradiative energy transfer. Importantly, TCPP@UiO-66-NH2 has a higher and more stable ECL signal. To further improve the sensitivity of the sensor, we use polydopamine-coated manganese dioxide (PDA@MnO2), which has a double quenching effect, as the quencher. The nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2-N) is one of the ideal markers for the early diagnosis of COVID-19, and its sensitivity detection is of great significance for the prevention and treatment of COVID-19. Thus, we constructed a quenching-type ECL sensor for the ultrasensitive detection of the SARS-CoV-2-N. Its linear range is 10 fg/mL∼1 μg/mL and the calculated detection limit is 1.4 fg/mL (S/N = 3). The spiked recoveries are 97.40-103.8%, with the relative standard deviations (RSD) under 3.0%. More importantly, the technique offers a viable way to identify and diagnose viral infections early.

Photocontrollable DNA Walker-Based Molecular Circuit for the Tunable Detection of MicroRNA-21 Using Metal-Organic Frameworks as Label-Free Fluorescence Tags

Tunable detection of microRNA is crucial to meet the desired demand for sample species with varying concentrations in clinical settings. Herein, we present a DNA walker-based molecular circuit for the detection of miRNA-21 (miR-21) with tunable dynamic ranges and sensitivity levels ranging from fM to pM. The phosphate-activated fluorescence of UiO-66-NH2 metal-organic framework nanoparticles was used as label-free fluorescence tags due to their competitive coordination effect with the Zr atom, which significantly inhibited the ligand-to-metal charge transfer. To achieve a tunable detection performance for miR-21, the ultraviolet sensitive o-nitrobenzyl was induced as a photocleavable linker, which was inserted at various sites between the loop and the stem of the hairpin probe to regulate the DNA strand displacement reaction. The dynamic range can be precisely regulated from 700- to 67,000-fold with tunable limits of detection ranging from 2.5 fM to 36.7 pM. Impressively, a Boolean logic tree and complex molecular circuit were constructed for logic computation and cancer diagnosis in clinical blood samples. This intelligent biosensing method presents a powerful solution for converting complex biosensing systems into actionable healthcare decisions and will facilitate early disease diagnosis.

Vesicles as a Multifunctional Microenvironment for Electrochemiluminescence Signal Amplification

Vesicles as a typical interface-rich microenvironment can promote the reaction rate and the intermediate stability, which are promising for introduction in electrochemiluminescence (ECL) signal amplification. In this work, a kind of multilamellar vesicle obtained from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used to modify the electrode surface. The AOT vesicle-modified microenvironment could significantly enhance the ECL performances for the luminol/O2 system in a neutral medium. The mechanism study demonstrated that the nanoscale multilamellar vesicles could maintain the vesicle structure on the electrode surface, which substantially improved the electron transfer and reaction rate, luminescence efficiency of the excited-state 3-aminophthalate anion, and stability of the superoxide anion radical. Alternatively, such a multifunctional microenvironment was also able to enhance the ECL signals from the tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+)/tripropylamine (TPrA) system. Moreover, another dodecyl dimethyl(3-sulfopropyl) ammonium hydroxide inner salt (DSB)-based vesicle was constructed to further verify the versatility of the vesicle-modified microenvironment for ECL signal amplification. Our work not only provides a versatile microenvironment for improving the efficiency of various ECL systems but also offers new insights for the microenvironment construction using the ordered assemblies in ECL fields.

Electrochemical biosensor strategy combining DNA entropy-driven technology to activate CRISPR-Cas13a activity and triple-stranded nucleic acids to detect SARS-CoV-2 RdRp gene

By merging DNA entropy-driven technology with triple-stranded nucleic acids in an electrochemical biosensor to detect the SARS-CoV-2 RdRp gene, we tackled the challenges of false negatives and the high cost of SARS-CoV-2 detection. The approach generates a CRISPR-Cas 13a-activated RNA activator, which then stimulates CRISPR-Cas 13a activity using an entropy-driven mechanism. The activated CRISPR-Cas 13a can cleave Hoogsteen DNA due to the insertion of two uracil (-U-U-) in Hoogsteen DNA. The DNA tetrahedra changed on the electrode surface and can therefore not construct a three-stranded structure after cleaving Hoogsteen DNA. Significantly, this DNA tetrahedron/Hoogsteen DNA-based biosensor can regenerate at pH = 10.0, which keeps Hoogsteen DNA away from the electrode surface, allowing the biosensor to function at pH = 7.0. We could use this technique to detect the SARS-CoV-2 RdRp gene with a detection limit of 89.86 aM. Furthermore, the detection method is very stable and repeatable. This technique offers the prospect of detecting SARS-CoV-2 at a reasonable cost. This work has potential applications in the dynamic assessment of the diagnostic and therapeutic efficacy of SARS-CoV-2 infection and in the screening of environmental samples.

Entropy-driven assisted T7 RNA polymerase amplification-activated CRISPR/Cas13a activity for SARS-CoV-2 detection in human pharyngeal swabs and environment by an electrochemiluminescence biosensor

In this study, we introduce an electrochemiluminescence (ECL) sensing platform based on the "Entropy-driven triggered T7 amplification-CRISPR/Cas13a system" (EDT-Cas). This platform combines a programmable entropy-driven cycling strategy, T7 RNA polymerase, and the CRISPR/Cas13a system to amplify the determination of the SARS-CoV-2 RdRp gene. The Ti₃C₂T_x-compliant ECL signaling molecule offers unique benefits when used with the ECL sensing platform to increase the assay sensitivity and the electrode surface modifiability. To obtain the T7 promoter, the SARS-CoV-2 RdRp gene may first initiate an entropy-driven cyclic amplification response. Then, after recognizing the T7 promoter sequence on the newly created dsDNA, T7 RNA polymerase starts transcription, resulting in the production of many single-stranded RNAs (ssRNAs), which in turn trigger the action of CRISPR/Cas13a. Finally, Cas13a/crRNA identifies the transcribed ssRNA. When it cleaves the ssRNA, many DNA reporter probes carrying -U-U- are cleaved on the electrode surface, increasing the ECL signal and allowing for the rapid and highly sensitive detection of SARS-CoV-2. With a detection limit of 7.39 aM, our method enables us to locate the SARS-CoV-2 RdRp gene in clinical samples. The detection method also demonstrates excellent repeatability and stability. The SARS-CoV-2 RdRp gene was discovered using the "Entropy-driven triggered T7 amplification-CRISPR/Cas13a system" (EDT-Cas). The developed ECL test had excellent recoveries in pharyngeal swabs and environmental samples. It is anticipated to offer an early clinical diagnosis of SARS-CoV-2 and further control the spread of the pandemic.

Electrochemiluminescence Immunosensors Based on ECL-RET Triggering between Mn SANE/PEI-Luminol and PtCu/h-MPF for Ultrasensitive Detection of CEA

In this paper, a novel donor-acceptor pair was creatively proposed based on the principle of electrochemiluminescence resonance energy transfer (ECL-RET): luminol immobilized on polyethyleneimine (PEI)-functionalized manganese-based single-atom nanozymes (Mn SANE/PEI-luminol, donor) and a PtCu-grafted hollow metal polydopamine framework (PtCu/h-MPF, acceptor). A quenched ECL immunosensor was constructed for the ultrasensitive analysis of carcinoembryonic antigen (CEA). Mn SANE, as an efficient novel coreaction accelerator with the outstanding performance of significantly activating H₂O₂ to produce large amounts of ROS, was further modified by the coreactant PEI, which efficiently immobilized luminol to form a self-enhanced emitter. As a result, the electron transport distance was effectively shortened, the energy loss was reduced, and luminol achieved a high ECL efficiency. More importantly, PtCu-grafted h-MPF (PtCu/h-MPF) was proposed as a novel quencher. The UV-vis spectra of PtCu/h-MPF partially overlap with the ECL spectra of Mn SANE/PEI-luminol, which can effectively trigger the ECL-RET behavior between the donor and the acceptor. The multiple quenching effect on Mn SANE/PEI-luminol was achieved, which significantly improved the sensitivity of the immunosensor. The prepared immunosensor exhibited good linearity in the concentration range of 10^-5 to 80 ng/mL. The results indicate that this work provides a new method for the early detection of CEA in clinical diagnosis.

Positively Charged Carbon Dots with Antibacterial and Antioxidant Dual Activities for Promoting Infected Wound Healing

Bacterial infection and excess reactive oxygen species are key factors that lead to slow or substantially delayed wound healing. It is crucial to design and develop new nanomaterials with antibacterial and antioxidative capabilities for wound healing. Here, positively charged carbon dots (CDs) are rationally designed and synthesized from p-phenylenediamine and polyethyleneimine by a facile one-pot solvothermal method, which show good biocompatibility in in vitro cytotoxicity, hemolysis assays, and in vivo toxicity evaluation. The positively charged CDs show superior antimicrobial effect against Staphylococcus aureus (S. aureus) at very low concentrations, reducing the risk of wound infection. At the same time, CDs with surface defects and unpaired electrons can effectively scavenge excess free radicals to reduce oxidative stress damage, accelerate wound inflammation-proliferation transition, and promote wound healing. The mouse model of skin infection demonstrates that CDs can effectively promote the wound healing of skin infection without obvious side effects by simply dropping or spraying onto the wound. We believe that the prepared CDs have satisfactory biocompatibility, antioxidant capacity, and excellent antibacterial activity and have great application potential in wound healing.

Voltammetric Study and Modeling of the Electrochemical Oxidation Process and the Adsorption Effects of Luminol and Luminol Derivatives on Glassy Carbon Electrodes

Luminol is one of the most widely used electrochemiluminescence (ECL) reagents, yet the detailed mechanism and kinetics of the electrochemical oxidation of luminol remain unclear. We propose a model that describes the electrochemical oxidation of luminol as multiple electron transfer reactions followed by an irreversible chemical reaction, and we applied a finite element method simulation to analyze the electron transfer kinetics in alkaline solutions. Although negligible at higher pH values, the adsorption of luminol on the glassy carbon electrode became noticeable in a solution with pH = 12. Additionally, various types of adsorption behaviors were observed for luminol derivatives and analogues, indicating that the molecular structure affected not only the oxidation but also the adsorption process. The adsorption effect was analyzed through a model with a Langmuir isotherm to show that the saturated surface concentration as well as the reaction kinetics increased with decreasing pH, suggesting a competition for the active sites between the molecule and OH^-. Moreover, we show that the ECL intensity could be boosted through the adsorption effect by collecting the ECL intensity generated through the electrochemical oxidation of luminol and a luminol analogue, L012, in a solution with pH = 13. In contrast with luminol, a significant adsorption effect was observed for L012 at pH = 13, and the ECL intensity was enhanced by the adsorbed species, especially at higher scan rates. The magnitude of the enhancement of the ECL intensity matched well with the simulation using our model.

Programmable Y-Shaped Probes with Proximity Bivalent Recognition for Rapid Electrochemiluminescence Response of Acute Myocardial Infarction

Herein, an exogenous luminophore-free and disposable electrochemiluminescence (ECL) biosensor was established for rapid response of acute myocardial infarction (AMI) using programmable Y-shaped probes (Y-probes) with proximity bivalent recognition. Specifically, the indium tin oxide thin film coated glass electrode (ITO) was modified with urchin-like porous TiO₂ microspheres (pTiO₂ MSs), which could achieve strong and stable ECL in S₂O₈^2- solution due to the dual promoting effect of the coreaction accelerator pTiO₂ MSs, exhibiting 2.7-fold higher ECL intensity in comparison with that of bare ITO. Moreover, the Y-probes as bivalent recognition elements containing two kinds of cardiac troponin I (cTnI, a biomarker of AMI) aptamers and a linker labeled with ferrocene (L-Fc) were designed to export a "signal off" mode. When the target cTnI was in the proximity of the Y-probes, the L-Fc was separated from the electrode surface due to the proximity recognition of cTnI and its aptamers, achieving the highly effective recovery of ECL, which allowed for a much more rapid detection of cTnI than the sandwich-type immunoassay. As a proof of concept, an exogenous luminophore-free and disposable ECL platform for rapid and sensitive monitoring of cTnI was obtained and displayed a desired linear range from 100 fg mL^-1 to 100 ng mL^-1 with a limit of detection (LOD) of 30.1 fg mL^-1, which can be ingeniously expanded as a portable home tester with ECL biosensors developments.

Ordered heterogeneity in dual-ligand MOF to enable high electrochemiluminescence efficiency for bioassay with DNA triangular prism as signal switch

Herein, the microRNA-141 electrochemiluminescence (ECL) bioassay was developed using the dual-ligand metal-organic framework (d-MOF) with ordered heterogeneity, which simultaneously contained the luminophore ligands (1,1,2,2-tetra(4-carboxylbiphenyl)ethylene, denoted as TCBPE) and the coreactant ligands (1,4-diazabicyclo[2.2.2]octane, denoted as DN₂H₂). The resultant d-MOF revealed significantly enhanced ECL intensity without any exogenous coreactants, which was 3.53 times higher in comparison with that of single-ligand MOF (only TCBPE as ligands) even with the addition of exogenous DN₂H₂. Thanks to the ordered heterogeneity in d-MOF, the intramolecular rotation of TCBPE was restricted via oriented coordination and the spatial location of DN₂H₂ was reasonably arranged due to the framework structure, which could not only enhance the excitation efficiency but also improve the electron-transfer efficiency based on the synergistic enhancement effect between structures and compositions in micro/nano confined space. Based on this, the proposed biosensor employed a novel DNA triangular prism (DNA TP) as signal switch to detect microRNA-141, achieving the low detection limit at the level of 22.9 aM and a broad linear ranging from 100 aM to 100 pM. The precise design of the ordered d-MOFs by co-assembling the luminophore and coreactant ligands holds a promise strategy to achieve ECL MOFs and construct the ECL biosensors in diagnostic analysis.

Au NP-Decorated g-C3N4-Based Photoelectochemical Biosensor for Sensitive Mercury Ions Analysis

Herein, an efficient and feasible photoelectrochemical (PEC) biosensor based on gold nanoparticle-decorated graphitic-like carbon nitride (Au NPs@g-C3N4) with excellent photoelectric performance was designed for the highly sensitive detection of mercury ions (Hg2+) . The proposed Au NPs@g-C3N4 was first modified on the surface of the electrode, which possessed a remarkable photocurrent conversion efficiency and could produce a strong initial photocurrent. Then, the thymine-rich DNA (S1) was immobilized on the surface of the modified electrode via Au-N bonds. Subsequently, 1-hexanethiol (HT) was added to the resultant electrode to block nonspecific binding sites. Finally, the target Hg2+ was incubated on the surface of the modified glassy carbon electrode (GCE). In the presence of target Hg2+, the thymine-Hg2+-thymine (T-Hg2+-T) structure formed due to the selective capture capability of thymine base pairs toward Hg2+, resulting in the significantly decrease of the photocurrent. Thereafter, the proposed PEC biosensor was successfully used for sensitive Hg2+ detection, as it possessed a wide linear range from 1 pM to 1000 nM with a low detection limit of 0.33 pM. Importantly, this study demonstrates a new method of detecting Hg2+ and provides a promising platform for the detection of other heavy metal ions of interest.