Real-time multiple signal amplification self-powered biosensing platform for ultrasensitive detection of MicroRNA

A portability self-powered sensor facilitates sensitive Cd2+ detection: Dual mechanism and three quantitative mode

As a common heavy metal contaminant, Cd2+ has adverse effects on food safety and consumer health. It is very important for human health to realize highly sensitive Cd2+ detection methods. The self-powered sensing system based on enzyme biofuel cells (EBFCs) does not need an external power supply, which can simplify the experimental equipment and has great application value in portable detection. Thus, the biosensor is innovatively integrated into the screen-printed electrode to construct a new type of portable sensor suitable for on-site and real-time Cd2+ detection. Hybridization chain reaction (HCR) combined with the Cd2+-dependent deoxyribose (DNAzyme) signal amplification strategy is used to enhance the detection sensitivity while specifically recognizing the Cd2+. Moreover, the self-powered sensor combines with smartphones to realize quantitative Cd2+ detection without other instruments and has the characteristic of Effectively improving the hazard detection technology is essential to ensure food safety. Portability, simplicity, and speed are suitable for real-time Cd2+ detection in the field. The dual mechanism and three quantitative modes combining colorimetric and two electrical signals output modes are adopted to realize the visualization and accurate detection. A series of research results confirm that this strategy is of great significance to strengthen the development of intelligent Cd2+ technology, expand the application of self-powered sensing technology, and improve the safety detection system.

Dual Recognition Strategy-Based Ratiometric Electrochemical Assay for Ultrasensitive and Accurate Detection of Specific Circulating Tumor Cells

Sensitive, specific, and accurate detection of circulating tumor cells (CTCs) is of great importance in the diagnosis and prognosis of cancer. Herein, an ultrasensitive ratiometric electrochemical biosensor was designed with a dual recognition strategy for highly specific and accurate detection of circulating MCF-7 human breast cancer cells based on gold film-modified porous organic cages loaded with ferrocene (Au/Fc@POCs) as the substrate and methylene blue-encapsulated covalent organic frameworks (MB@COFs) as the label material, producing two independent electrochemical signals from the Fc and MB probes, respectively. As the concentration of MCF-7 cells increases, the electrochemical signal of MB enhances significantly while the oxidation signal of Fc decreases remarkably. Under optimal experimental conditions, the ratios (IMB/IFc) between the double signals showed a broad dynamic range of 10 to 1 × 107 cells/mL with an effectively lower detection limit of 1 cells/mL (S/N = 3). Furthermore, the biosensor was able to accurately enumerate MCF-7 cells in human serum samples with excellent results. In this work, the developed ratiometric electrochemical biosensor offers a reliable and sensitive strategy for the quantitative determination of circulating MCF-7 human breast cancer cells as well as an effective approach for the clinical detection of rare cancer cells, especially in early stage cancer diagnosis.

Electrochemiluminescence Biosensor for Ascorbic Acid Based on Target Transformation of Cell-Free RNA Transcription System and Duplex-Specific Nuclease-Assisted Recycling Amplification

A cell-free RNA transcription system had been coupled with electrochemiluminescence (ECL) detection technology for the first time to develop an ascorbic acid (AA, acting as a model target) biosensor. The biosensor is composed of single-stranded DNA (ssDNA) sequences modified with alkynyl and azido groups, respectively, alongside an incomplete gene circuit framework. The addition of target AA and copper ions will cause the linkage of the two ssDNA sequences through a click chemistry reaction. This results in the subsequent reconstruction of a complete gene circuit. The reconstituted gene circuit, in conjunction with the T7 RNA polymerase, drives the transcription of substantial quantities of RNA. ssDNA labeled with ferrocene (Fc) (Fc-DNA) had been immobilized on a tris(2,2'-bipyridyl) ruthenium(II) chloride hexahydrate-doped SiO2 nanoparticle (Ru@SiO2 NPs) modified electrode first. The quenching effect of Fc on Ru@SiO2 causes the low ECL detected. The transcribed RNA sequence assisted double-stranded specific nuclease (DSN) to cut the ssDNA-Fc and the ECL of the system was enhanced. Optimal experimental conditions reveal that the ECL signal exhibits a linear correlation with the logarithmic concentration of AA, spanning a detection range from 100 nM to 1 mM, with a detection limit of 45 nM. This innovative methodology expands the utility of a cell-free RNA transcription system within the realm of biosensing applications.

Handgrip-Ring Structure Sensing Probe Assisted Multiple Signal Amplification Strategy for Sensitive and Label-Free Single-Stranded Nucleic Acid Analysis

Precise and efficient identification of single-stranded nucleic acids is crucial for both pathological research and early diagnosis of diseases, such as cancers. Therefore, we have devised a novel biosensor that utilizes an elegantly designed handgrip-ring structure sensing probe to enhance the detection sensitivity and reduce background signals. The handgrip-ring structure sensing probe combines ring padlock-based target recognition and hairpin structure probe-based signal amplification. The target sequences form a binding interaction with the ring padlock in the sensing probe, leading to the elongation of the single-stranded chain with the assistance of polymerase. This elongation step results in the release of the hairpin probe, triggering a signal amplification process. This design significantly minimized the potential discrepancies that may occur during the signal amplification process, hence bestowing the approach with a low level of background signals. By utilizing this innovative design, the current biosensor demonstrates a remarkable ability to detect miRNA with a limit as low as 376 aM and single-stranded DNA sequences with a limit as low as 45.3 aM. In addition, it possesses exceptional discrimination capabilities. The efficacy of this approach in diagnosing targets was also effectively proved by the rational redesign of the ring padlock.

Sensitive and Cost-Effective Tools in the Detection of Ovarian Cancer Biomarkers

Women diagnosed with late-stage ovarian cancer suffer a very high rate of mortality. Accordingly, it is imperative to detect and diagnose the disease as early as possible in its development. Achievement of this aim implies relatively large-scale screening of women at an age of clinical significance through assay of biomarkers for disease present in blood or serum. Biosensor detection offers an attractive technology for the automated detection of such species. Among several biomarkers that have been identified that are present in patients with ovarian cancer, the only one that is commonly tested for in clinical use is cancer antigen 125, which is considered to be a poor biomarker for the disease. Here, we describe several biosensors that developed in the past decade for the detection of ovarian cancer biomarkers such as CA125, human epididymis protein 4 (HE4) and apolipoprotein A1. The challenges presented by the fabrication of biosensor devices for detecting ovarian cancer and the limited number of biosensors developed for this purpose are discussed.

Label-Free and Universal CRISPR/Cas12a-Based Detection Platform for Nucleic Acid Biomarkers

CRISPR/Cas12a has been widely used in molecular diagnostics due to its excellent trans-cleavage activity. However, conventional reporters, such as F/Q-labeled single-stranded DNA (ssDNA) reporters, enzyme-labeled reporters, and spherical nucleic acid reporters, require complex modification or labeling processes. In this study, we have developed a rapid, universal, and label-free CRISPR/Cas12a-based biomarker detection platform via designing a G-quadruplex (G4) containing a hairpin structure as the reporter. The hairpin loop design of hairpin G4 improves the cleavage efficiency of Cas12a and the signal strength of the G4 binding ligand. Meanwhile, the incorporation of a G4 binding dye (protoporphyrin IX) eliminates the need for complex modifications. The CRISPR-hairpin G4 detection platform is capable of detecting ssDNA, double-stranded DNA, genetic RNAs, and miRNAs. Moreover, this platform achieves label-free detection in clinical samples, demonstrating its practical applicability and efficiency.

CRISPR/Cas12a and Hybridization Chain Reaction-Coregulated Magnetic Relaxation Switching Biosensor for Sensitive Detection of Viable Salmonella in Animal-Derived Foods

We combined a CRISPR/Cas12a system with a hybridization chain reaction (HCR) to develop an ultrasensitive magnetic relaxation switching (MRS) biosensor for detecting viable Salmonella typhimurium (S. typhimurium). Magnetic nanoparticles of two sizes (30 and 1000 nm: MNP30 and MNP1000, respectively) were coupled through HCR. The S. typhimurium gene-activated CRISPR/Cas12a system released MNP30 from the MNP1000-HCR-MNP30 complex through a trans-cleavage reaction. After magnetic separation, released MNP30 was collected from the supernatant and served as a transverse relaxation time (T2) signal probe. Quantitative detection of S. typhimurium is achieved by establishing a linear relationship between the change in T2 and the target gene. The biosensor's limit of detection was 77 CFU/mL (LOD = 3S/M, S = 22.30, M = 0.87), and the linear range was 102-108 CFU/mL. The accuracy for detecting S. typhimurium in real samples is comparable to that of qPCR. Thus, this is a promising method for the rapid and effective detection of foodborne pathogens.

Novel Self-Powered Biosensor Based on Au Nanoparticles @ Pd Nanorings and Catalytic Hairpin Assembly for Ultrasensitive miRNA-21 Assay

An ultrasensitive self-powered biosensor is constructed for miRNA-21 detection based on Au nanoparticles @ Pd nanorings (Au NPs@Pd NRs) and catalytic hairpin assembly (CHA). The Au NPs@Pd NRs possess excellent electrical conductivity to improve the electron transfer rate and show good elimination of byproduct H2O2 to assist glucose oxidase (GOD) to catalyze glucose; CHA is used as an amplification strategy to effectively enhance the sensitivity of the biosensor. To further amplify the output signal, a capacitor is integrated into the self-powered biosensor. With multiple signal amplification strategies, the self-powered biosensor possesses a linear range of 0.1-10-4 fM and a lower limit of detection (LOD) of 0.032 fM (S/N = 3). In addition, the as-prepared self-powered biosensor displays potential applicability in the assay toward miRNA-21 in human serum samples.

Precisely Manipulating Steric Hindrance Effect on DNA Walker for Tunable Detection of MicroRNA Using Enzymatic Strand Displacement Amplification

The spatial constraints imposed by the DNA structure have significant implications for the walking efficiency of three-dimensional DNA walkers. However, accurately quantifying and manipulating steric hindrance remains a challenging task. This study presents a steric hindrance-controlled DNA walker utilizing an enzymatic strand displacement amplification (ESDA) strategy for detecting microRNA-21 (miR-21) with tunable dynamic range and sensitivity. The steric hindrance of the DNA walker was precisely manipulated by varying the length of empty bases from 6.5 Å to 27.4 Å at the end of the track strand and adjusting the volumetric dimensions of the hairpin structure from 9.13 nm3 to 26.2 nm3 at the terminus of the single-foot DNA walking strand. This method demonstrated a tunable limit of detection for miR-21 ranging from 3.6 aM to 35.6 nM, along with a dynamic range from ∼100-fold to ∼166 000-fold. Impressively, it exhibited successful identification of cancer cells and clinical serum samples with high miR-21 expression. The proposed novel strategy not only enables tunable detection of miRNA through the regulation of steric hindrance but also achieves accurate and quantitative analysis of the steric hindrance effect, promising broader applications in personalized medicine, early disease detection, and drug development.

A dual-functional NIR fluorescence probe for detecting hypochlorous acid and bisulfite in biosystem

BACKGROUND

Bisulfite (HSO3-) serves as a bleaching agent, antioxidant, antimicrobial, and regulator of enzymatic reactions in biosystem. However, abnormal levels of bisulfite can be detrimental to health. Hypochlorous acid (HOCl), which acts as bioactive small molecules, is crucial for maintaining normal biological functions in living organisms. Disruption of its equilibrium can lead to oxidative stress and various diseases. Therefore, it's essential to monitor the fluctuations of HOCl and HSO3- at cellular and in vivo levels to study their physiological and pathological functions.

RESULTS

This study constructed a novel NIR bifunctional colorimetric fluorescent probe using thienocoumarin-indanedione structures to identify hypochlorite (ClO-) and bisulfite (HSO3-). By using CSO-IO to recognize HSO3- and HOCl, two distinct products were generated, displaying green and blue fluorescence, respectively. This property effectively allows for the simultaneous dual-functional detection of HSO3- (LOD: 113 nM) and HOCl (LOD: 43 nM).

SIGNIFICANCE

In this work, the biocompatible molecule CSO-IO has been effectively designed to detect HOCl/HSO3- in living cells and zebrafish. As a result, the dual-functional fluorescent probe has the potential to be utilized as a molecular tool to detect HSO3- derived compounds and HOCl simultaneously within the complex biological system.

CRISPR/Cas12a-triggered ordered concatemeric DNA probes signal-on/off multifunctional analytical sensing system for ultrasensitive detection of thalassemia

Based on CRISPR/Cas12a triggered ordered concatemeric DNA probes, a "on/off" self-powered biosensor is developed to achieve highly sensitive detection of thalassemia gene CD142 through open-circuit potential-assisted visual signal output. The ingeniously constructed glucose oxidase (GOD)-functionalized ordered concatemeric DNA probe structure can significantly amplify signal output, while the coupled CRISPR/Cas12a system is served as a "signal switch" with excellent signal-transducing capabilities. When the ordered concatemeric DNA probe structure is anchored on electrode, the response signal of the sensing system is in the "signal on" mode. While, the presence of the target activates the non-specific cleavage activity of the CRISPR/Cas12a system, causing the sensing system to switch to the "signal off" mode. In the detection system, GOD catalyzes the oxidation of glucose to produce hydrogen peroxide, which further catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form a color product, enabling visual signal of the target through naked-eye color contrast. By employing a multifunctional analytical mode combining electrochemical and visual signal outputs, accurate determination of the target is achieved, with linear ranges of 0.0001-100 pM, and detection limits of 48.1 aM (S/N = 3). This work provides a reference method for sensitive detection of thalassemia genes and holds great diagnostic potential in biomedical applications.

Rapid, on-site quantitative determination of mycotoxins in grains using a multiple time-resolved fluorescent microsphere immunochromatographic test strip

The label probe plays a crucial role in enhancing the sensitivity of lateral flow immunoassays. However, conventional fluorescent microspheres (FMs) have limitations due to their short fluorescence lifetime, susceptibility to background fluorescence interference, and inability to facilitate multi-component detection. In this study, carboxylate-modified Eu(III)-chelate-doped polystyrene nanobeads were employed as label probes to construct a multiple time-resolved fluorescent microsphere-based immunochromatographic test strip (TRFM-ICTS). This novel TRFM-ICTS facilitated rapid on-site quantitative detection of three mycotoxins in grains: Aflatoxin B1 (AFB1), Zearalenone (ZEN), and Deoxynivalenol (DON). The limit of detection (LOD) for AFB1, ZEN, and DON were found to be 0.03 ng/g, 0.11 ng/g, and 0.81 ng/g, respectively. Furthermore, the TRFM-ICTS demonstrated a wide detection range for AFB1 (0.05-8.1 ng/g), ZEN (0.125-25 ng/g), and DON (1.0-234 ng/g), while maintaining excellent selectivity. Notably, the test strip exhibited remarkable stability, retaining its detection capability even after storage at 4 °C for over one year. Importantly, the detection of these mycotoxins relied solely on simple manual operations, and with a portable reader, on-site detection could be accomplished within 20 min. This TRFM-ICTS presents a promising solution for sensitive on-site mycotoxin detection, suitable for practical application in various settings due to its sensitivity, accuracy, simplicity, and portability.

Implementation of π-π interaction in AuNPs@GDY to boost the bioelectrocatalysis in enzymatic biofuel cells

The main challenges (sluggish electron transfer, low energy density) hinder the future application of enzymatic biofuel cells (EBFCs), which urgent to take effective measures to solve these issues. In this work, a composite of Au nanoparticles decorated graphdiyne (AuNPs@GDY) is fabricated and employed as the carrier of enzyme (G6PDH), and a mechanism based on π-π interaction of electron transfer is proposed to understand bioelectrocatalysis processes. The results show that the AuNPs@GDY composite exhibits the highest current density among the three materials (GDY, AuNPs, and AuNPs@GDY), which is 3.4 times higher than that of GDY and 2.5 times higher than that of AuNPs. Furthermore, the results reveal that the AuNPs could increase the loading of enzymes and provide more active site for reaction, while GDY provides highly π-conjugated structure and unique sp/sp2-hybridized linkages interface. This work provides new insights to explore a theoretical basis for the development of more efficient bioelectrocatalytic systems.

WS2 nanosheets-based electrochemical biosensor for highly sensitive detection of tumor marker miRNA-4484

In this paper, a few-layer WS2 nanosheets-based electrochemical biosensor was fabricated for the highly sensitive detection of breast cancer tumor marker miRNA-4484. Firstly, few-layer WS2 nanosheets were prepared by shear stripping and characterized by SEM, TEM, AFM and UV spectrophotometer. After modification of few-layer WS2 nanosheets on the electrode surface, the miRNA probe was fixed on the few-layer WS2 nanosheets by polycytosine (PolyC). Then short-chain miRNA containing PolyC was used as the blocking agent to close the excess active sites on the surface of WS2 nanosheets to complete the fabrication of the sensor biosensing interface. Finally, the current changes caused by the specific binding of miRNA-4484 to the probe were analyzed by differential pulse voltammetry (DPV). The results showed that the sensor had a good linear relationship for the detection of miRNA-4484 in the concentration range of 1 aM-100 fM, and the detection limit was as low as 1.61 aM. In addition, the electrochemical sensor had excellent selectivity, stability and reproducibility. The artificial sample tests indicated that the developed biosensors have the potential for clinical application in the future.

Electrochemiluminescence in Graphitic Carbon Nitride Decorated with Silver Nanoparticles for Dopamine Determination Using Machine Learning

Electrochemiluminescence (ECL) luminophores with wavelength-tunable multicolor emissions are essential for multicolor ECL imaging detection and multiplexed analysis. In this work, silver nanoparticle (Ag NP)-decorated graphitic carbon nitride (g-CN@Ag) nanocomposites were synthesized. The morphology, chemical composition, structure, and ECL property of g-CN@Ag were investigated. The prepared g-CN, g-CN@Ag1, g-CN@Ag5, and g-CN@Ag10 can produce blue, blue-green, chartreuse, and yellow colored ECL emissions, respectively, by using K2S2O8 as the coreagent. The ECL emission wavelength of g-CN@Ag can be regulated from 460 to 565 nm by modulating the content of the immobilized Ag NPs. Then, a multicolor ECL detection array was fabricated by using g-CN, g-CN@Ag1, g-CN@Ag5, and g-CN@Ag10 as four ECL luminophores. Dopamine was detected based on its inhibition effect on the multicolor ECL emissions. The linear range is from 0.1 nM to 1 mM with the lowest detection limit of 44 pM. Then, machine learning-assisted multiparameter concentration prediction of dopamine was further carried out by combining the deep neural network (DNN) algorithm. This work provides a new avenue to regulate the ECL emission wavelength of g-CN by using the metal nanoparticle modification strategy and presents an effective machine learning-assisted multicolor ECL detection strategy for accurate multiparameter quantitative detection.

Determination of Acetylamantadine by γ-Cyclodextrin-Assisted α-HL Nanopore for Potential Cancer Prediagnosis

The high expression of Spermidine/spermine N1-acetyltransferase (SSAT-1) is an important indicator in early cancer diagnosis. Here, we developed a nanopore-based methodology with γ-cyclodextrin as an adaptor to detect and quantify acetylamantadine, the specific SSAT-1-catalyzed product from amantadine, to accordingly reflect the activity of SSAT-1. We employ γ-cyclodextrin and report that amantadine cannot cause any secondary signals in γ-cyclodextrin-assisted α-HL nanopore, while its acetylation product, acetylamantadine, does. This allows γ-cyclodextrin to practically detect acetylamantadine in the interference of excessive amantadine, superior to the previously reported β-cyclodextrin. The quantification of acetylamantadine was not interfered with even a 50-fold amantadine and displayed no interference in artificial urine sample analysis, which indicates the good feasibility of this nanopore-based methodology in painless cancer prediagnosis. In addition, the discrimination mechanism is also explored by 2-D nuclear magnetic resonance (NMR) and nanopore experiments with a series of adamantane derivatives with different hydrophilic and hydrophobic groups. We found that both the hydrophobic region matching effect and hydrophilic interactions play a synergistic effect in forming a host-guest complex to further generate the characteristic signals, which may provide insights for the subsequent design and study of drug-cyclodextrin complexes.

"Two-in-One" PtPdCu Trimetallic Multifunctional Nanoparticles-Mediated Dual-Signal-Integrated Aptasensor for Ultradetection of Enrofloxacin

Balancing the accuracy and simplicity of aptasensors is a challenge in their construction. This study addresses this issue by leveraging the remarkable loading capacity and peroxidase-like catalytic activity of PtPdCu trimetallic nanoparticles, which reduces the reliance on precious metals. A dual-signal readout aptasensor for enrofloxacin (ENR) detection is designed, incorporating DNA dynamic network cascade reactions to further amplify the output signal. Exploiting the strong loading capacity of PtPdCu nanoparticles, they are self-assembled with thionine (Thi) to form a signal label capable of generating signals in two independent modes. The label exhibits excellent enzyme-like catalytic activity and enhances electron transfer capabilities. Differential pulse voltammetry (DPV) and square-wave voltammetry (SWV) are employed to independently read signals from the oxidation-reduction reaction of Thi and the catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) by H2O2. The introduced DNA dynamic network cascade reaction modularizes sample processing and electrode surface signal generation, avoiding electrode contamination and efficiently increasing the output of the catalyzed hairpin assembly (CHA) cycle. Under optimized conditions, the developed aptasensor demonstrates detection limits of 0.112 (DPV mode) and 0.0203 pg/mL (SWV mode). Additionally, the sensor successfully detected enrofloxacin in real samples, expanding avenues for designing dual-mode signal amplification strategies.

Controlled-Release Electrochemiluminescence Biosensor with Strong Self-On Effect by a Multiple Signal Amplification Strategy for Trace Detection of Prostate-Specific Antigen

The enhancement of sensitivity in biological analysis detection can reduce the probability of false positives of the biosensor. In this work, a novel self-on controlled-release electrochemiluminescence (CRE) biosensor was designed by multiple signal amplification and framework-enhanced stability strategies. As a result, the changes of the ECL signal were enhanced before and after the controlled-release process, achieving sensitive detection of prostate-specific antigen (PSA). Specifically, for one thing, Fe3O4@CeO2-NH2 with two paths for enhancing the generation of coreactant radicals was used as the coreaction accelerator to boost ECL performance. For another, due to the framework stability, zeolitic imidazolate framework-8-NH2 (ZIF-8-NH2) was combined with luminol to make the ECL signal more stable. Based on these strategies, the constructed CRE biosensor showed a strong self-on effect in the presence of PSA and high sensitivity in a series of tests. The detection range and limit of detection (LOD) were 5 fg/mL to 10 ng/mL and 2.8 fg/mL (S/N = 3), respectively, providing a feasible approach for clinical detection of PSA.

Isothermal strand displacement polymerase reaction (ISDPR)-assisted microchip electrophoresis for highly sensitive detection of cancer associated microRNAs

More and more studies have found that microRNAs (miRNAs) are markers of cancer, and detection of miRNAs is beneficial for early diagnosis and prognosis of cancer. In this paper, the isothermal strand displacement polymerase reaction (ISDPR), which is an enzyme-assisted nucleic acid amplification method, was studied to combine with microchip electrophoresis (MCE) for a simultaneously detection of two cancer related miRNAs named microRNA-21 (miR-21) and microRNA-221 (miR-221). In the ISDPR amplification, two different DNA hairpins (HPs) were specifically designed, so that miR-21 and miR-221 could respectively bind to HPs and started ISDPR amplification to generate two different products which were ultimately detected by MCE. The optimal conditions of ISDPR were carefully investigated, and the limits of detection (LOD) of miR-21 and miR-221 were as low as 0.35 fM and 0.25 fM (S/N = 3) respectively under these conditions. The human lung tumor cells and serum samples were analyzed by this ISDPR-MCE method and satisfactory results were obtained, which means that this method is of high sensitivity, high efficiency, low reagent consumption and simple operation in miRNAs detection.

A zinc-air battery assisted self-powered electrochemical sensor for sensitive detection of microcystin-RR

Building a high-performance sensing platform is the key to developing sensitive sensors. Herein, a highly sensitive self-powered electrochemical sensor (SPES) was constructed using a WO3·H2O film as the cathode prepared by a hydrothermal method and Zn as the anode, and it could be applied to sensitive detection of microcystin (MC-RR). The WO3·H2O film with a larger specific surface area could boost the oxygen reduction reaction (ORR), which could achieve signal amplification and significantly increase the sensitivity of the sensors. Under the optimal conditions, there was a good linear relationship between the increased electrical power density and the logarithm of MC-RR concentration with a detection limit of 1.31 × 10-15 M (S/N = 3). This method had good anti-interference ability and stability when applied to the determination of MC-RR content in actual samples, which could boost the potential application of electrochemical sensors in the field of environmental monitoring.

Bifunctional MOF-Encapsulated Cobalt-Doped Carbon Dots Nanozyme-Powered Chemiluminescence/Fluorescence Dual-Mode Detection of Aflatoxin B1

A novel bifunctional MOF-encapsulated cobalt-doped carbon dots nanozyme (Co-CD/PMOF) with excellent peroxidase-mimic catalytic activity and fluorescence property was synthesized and employed to fabricate a chemiluminescence/fluorescence (CL/FL) dual-mode immunosensor for AFB1 detection. Co-CD/PMOF could catalyze the luminol/H2O2 system to generate robust and long-lasting CL signals due to the slow diffusion effect and continuous generation of •OH, O2•-, and 1O2 species. Differing from traditional flash-type CL emissions, this glow-type CL emission is helpful to fabricate a sensitive and accurate CL sensing platform. Then the CL/FL dual-mode detection of AFB1 was developed using antibody-functionalized Co-CD/PMOF as the signal-amplifying nanoprobe. The CL mode assay based on indirect competitive immune principle was carried out on a chemiluminescence optical fiber platform, where the AFB1-OVA-functionalized optical fiber probe was employed for biorecognition, separation, and signal conducting. The AFB1 detection range and LOD were 0.63-69.36 ng/mL and 0.217 ng/mL, respectively. Using AFB1 antibody-functionalized immunomagnetic beads for capturing and separation, the FL mode detection of AFB1 was established based on the sandwich immune principle. A linear range of 0.54-51.91 ng/mL and a LOD of 0.027 ng/mL were obtained. This work designed a sensitive, rapid, and reliable nanozyme-powered dual-mode assay strategy and provided technical support in the field of environmental monitoring and food safety.

Multiple signal amplification strategy induced by biomarkers of lung cancer: A self-powered biosensing platform adapted for smartphones

Lung cancer is a major malignant cancer with low survival rates, and early diagnosis is crucial for effective treatment. Herein, a biosensing platform that is self-powered derived from a capacitor-coupled EBFC has been developed for ultra-sensitive real-time identification of microRNA-21 (miRNA-21) with the assistance of a mobile phone. The flexible substrate of the platform is prepared on a carbon paper modified with graphdiyne and gold nanoparticles. The biosensor employs DNAzyme-mediated dual strand displacement amplification, which enhances the signal output intensity of the EBFC and improves selectivity. The coupling of the capacitor with the EBFC significantly amplifies the sensing signal, causing a 10.6-fold surge in current respond and further improving the sensitivity of the sensing platform. The established detection approach demonstrates a linear relationship varied from 0.0001 to 10,000 pM, with a sensitivity down to 32.3 aM as the minimum detectable limit, which has been effectively utilized for detecting miRNA-21 in practical samples. This sensing system provides strong support for the construction of portable detection devices, and the strategy of the platform construction provides an effective method for ultra-sensitive and accurate detection of miRNA, holding great potential in clinical diagnosis, prognosis evaluation, and drug screening for cancer.

Enhancing 3D DNA Walker-Induced CRISPR/Cas12a Technology for Highly Sensitive Detection of ExomicroRNA Associated with Osteoporosis

Exosomal microRNAs (exomiRNAs) have emerged as promising biomarkers for the early clinical diagnosis of osteoporosis. However, their limited abundance and short length in peripheral blood present significant challenges for the accurate detection of exomiRNAs. Herein, we have designed and implemented an efficacious fluorescence-based biosensor for the highly sensitive detection of exomiRNA associated with osteoporosis, leveraging the enhancing 3D DNA walker-induced CRISPR/Cas12a technology. The engineered DNA walker is capable of efficiently transforming target exomiRNA into amplifying DNA strands, thereby enhancing the sensitivity of the developed biosensor. Concurrently, the liberated DNA strands serve as activators to trigger Cas12a trans-cleavage activity, culminating in a significantly amplified fluorescent signal for the highly sensitive detection of exomiRNA-214. Under optimal conditions, the devised technology demonstrated the capacity to detect target exomiRNA-214 at concentrations as low as 20.42 fM, encompassing a wide linear range extending from 50.0 fM to 10.0 nM. Moreover, the fluorescence-based biosensor could accurately differentiate between healthy individuals and osteoporosis patients via the detection of exomiRNA-214, which was in agreement with RT-qPCR results. As such, this biosensing technology offers promise as a valuable tool for the early diagnosis of osteoporosis.

A core-shell structured AuNPs@ZnCo-MOF SERS substrate for sensitive and selective detection of thiram

Surface-enhanced Raman scattering (SERS) enables pesticide residue monitoring to become facile and efficient. In this study, a core-shell structured gold nanoparticles@ZnCo metal-organic framework (AuNPs@ZnCo-MOF) SERS substrate was designed and successfully synthesized for efficient and selective detection of thiram. The bimetallic ZnCo-MOF shell can not only enrich the targeted molecules in the electromagnetic field because of its excellent absorptive capacity, but also act as a stabilized matrix for protecting the AuNPs from aggregation. The AuNPs@ZnCo-MOFs exhibited a high enhancement factor (EF) of 3.51 × 106 and a low detection limit of 1 × 10-7 mol L-1. Besides, the substrate material showed exceptional stability for up to 28 days at room temperature. The AuNPs@ZnCo-MOFs were used to detect thiram which displayed wide linearity (1 × 10-7 to 1 × 10-4 mol L-1) and high recoveries (83.45-99.61%). Moreover, the AuNPs@ZnCo-MOF SERS substrate exhibited excellent anti-interference ability and size selectivity for the target molecules. These indicate that the AuNPs@ZnCo-MOF substrate has great potential for the detection of thiram residues in practical applications.

Novel electrochemical biosensor for breast cancer detection, based on a nanocomposite of carbon nanofiber, metal-organic framework, and magnetic graphene oxide

In this study, we present the newly developed a novel microRNA biosensor based on magnetic rod carbon paste electrodes for breast cancer detection by using a relatively new MOF structure as a substrate. The major goal of manufacturing biosensors, suitable for clinical diagnostics, is to measure very low amount of microRNA 155 in complex environments. Therefore, we used a combination of different materials, including carbon nanofibers, CuBTC-AIA (CuMOF), and Fe@rGO, to improve the electrode surface-to-volume ratio and facilitate the electron transfer process. In this method, 1-pyrenebutyric acid N-hydroxysuccinimide ester was used to bind the microRNAs to the electrode surface. The hybridization process on the modified electrode surface was investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry across the potential range, in which the accumulated hematoxylin was electroactive. Under optimal conditions, a very low detection limit of 0.08 fM and an adequate dynamic range of 0.2 fM-500 pM were achieved. The fabricated sensor was reported to be reproducible and selective when tested using different types of mismatched target sequences. And finally, the real human serum samples were used to confirm the capability of the nanobiosensor to detect microRNA 155 without any significant interference from other molecules and components.

ZIF-8 labelled a new electrochemical aptasensor based on PEI-PrGO/AuNWs for DON detection

In this work, a novel ultrasensitive aptasensor for deoxynivalenol (DON) detection based on the polyethyleneimine-functionalised porous reduced graphene oxide loaded gold nanowires (PEI-PrGO/AuNWs) and methylene blue (MB)-labelled zeolitic imidazolate framework-8 (ZIF-8) signal amplification strategy was proposed. PEI-PrGO/AuNWs with large surface area and excellent conductivity were used as modification materials on bare gold electrodes, which could increase the combining of complementary strand (cDNA) on the electrode substrate and accelerate the electron transfer efficiency. Furthermore, a novel electrochemical signal probe was synthesized using streptavidin-modified zeolitic imidazolate framework-8 (ZIF-8/SA) as a carrier loaded with MB and reverse complementary chain (sDNA). In the presence of DON, the signal probe was introduced to the electrode surface by Watson-Crick base pairing after specific binding of DON to the aptamer (Apt). As expected, under the optimal conditions, the DON concentration was linearly related to the peak current generated by the prepared aptasensor, and the measured data were combined with theoretical calculations to obtain a detection limit of 2.23 × 10-9 mg/mL.

Biomaterials and bioelectronics for self-powered neurostimulation

Self-powered neurostimulation via biomaterials and bioelectronics innovation has emerged as a compelling approach to explore, repair, and modulate neural systems. This review examines the application of self-powered bioelectronics for electrical stimulation of both the central and peripheral nervous systems, as well as isolated neurons. Contemporary research has adeptly harnessed biomechanical and biochemical energy from the human body, through various mechanisms such as triboelectricity, piezoelectricity, magnetoelasticity, and biofuel cells, to power these advanced bioelectronics. Notably, these self-powered bioelectronics hold substantial potential for delivering neural stimulations that are customized for the treatment of neurological diseases, facilitation of neural regeneration, and the development of neuroprosthetics. Looking ahead, we expect that the ongoing advancements in biomaterials and bioelectronics will drive the field of self-powered neurostimulation toward the realization of more advanced, closed-loop therapeutic solutions, paving the way for personalized and adaptable neurostimulators in the coming decades.

A dual-cycle amplification-based electrochemical platform for sensitive detection of tobramycin

BACKGROUND

Tobramycin (TOB), an essential aminoglycoside antibiotic in human life, poses potential threats due to its residues in the environment. The primary concern is the adverse impact of excessive TOB on human kidneys, hearing, and other organs, significantly affecting human health. Constructing a sensitive electrochemical platform for simple and rapid trace detection is crucial. Herein, to enhance the sensitivity of TOB detection in the environment and mitigate the risks associated with residual antibiotics, an ultrasensitive electrochemical aptasensor was developed.

RESULTS

The sensor employs a dual-cycle amplification strategy involving catalytic hairpin assembly (CHA) and exonuclease III (Exo III) for efficient signal amplification. Simultaneously, the electrode performance was optimized by incorporating gold nanowires (AuNWs) onto the surface of reduced graphene oxide (PDA-rGO). Specifically, in the presence of TOB, which binds to the aptamer (Apt), dsDNA dissociates, releasing cDNA to open hairpin 1 (HP1) and initiate the CHA cycle with the participation of hairpin 2 (HP2). Exo III shears HP1 in the HP1/HP2 complex, freeing HP2 to participate in the CHA cycle again. Ultimately, a significant amount of signal label is retained on the electrode by hybridizing with sheared HP1, generating a robust electrical signal.

SIGNIFICANCE

Through the signal amplification strategy, the aptasensor design provides a broad linear range of 0.005-500 nM, with a low detection limit of 0.112 pM for TOB. It is worth mentioning that the aptasensor displayed favorable stability, specificity, and reproducibility, and has been successfully applied to practical samples, demonstrating its utility in practical applications.

Advanced Self-Powered Biofuel Cells with Capacitor and Nanogenerator for Biomarker Sensing

Self-powered biofuel cells (BFCs) have evolved for highly sensitive detection of biomarkers such as noncodon micro ribonucleic acids (miRNAs) in the presence of interfering substrates. Self-charging supercapacitive BFCs for in vivo and in vitro cellular microenvironments represent the most prevalent sensing mechanism for diagnosis. Therefore, self-powered biosensing (SPB) with a capacitor and contact separation with a triboelectric nanogenerator (TENG) offers electrochemical and colorimetric dual-mode detection via improved electrical signal intensity. In this review, we discuss three major components: stretchable self-powered BFC design, miRNA sensing, and impedance spectroscopy. A specific focus is given to 1) assembling of sensors for biomarkers, 2) electrical output signal intensification, and 3) role of supercapacitors and nanogenerators in SPBs. We outline the key features of stretchable SPBs and the sequence of miRNA sensing by SPBs. We have emphasized the need of a supercapacitor and nanogenerator for SPBs in the context of advanced assembly of the sensing unit. Finally, we outline the role of impedance spectroscopy in the detection and estimation of biomarkers. We highlight key challenges in SPBs for biomarker sensing, which needs improved sensing accuracy, integration strategies of electrochemical biosensing for in vitro and in vivo microenvironments, and the impact of miRNA sensing on cancer diagnostics. This article attempts a specific focus on the accuracy and limitations of sensing unit for miRNA biomarkers and associated tool for boosting electrical signal intensity for a potential big step further.

Smartphone-Assisted Flexible Electrochemical Sensor Platform by a Homology DNA Nanomanager Tailored for Multiple Cancer Markers Field Inspection

In this work, an ingenious sensor technology was established by integrating the EBFCs on a flexible paper strip carrier (PE) that was used for simultaneous detection of tumor markers in complex samples. Adopting high performance ultrathin graphdiyne (U-GDY) as the substrate can increase the enzyme load, accelerate the electron transfer rate, and significantly enhance the detection sensitivity. A homologous DNA nanomanager strategy cleverly uses signal switches to recycle and amplify target miRNAs, while the smartphone receives real-time instantaneous current values to realize multivariate detection. Electrochemical data show that the detection limits (LODs) of miRNA-21 and miRNA-155 are 0.09 and 0.15 fM in the wide concentration range. The results confirm that the tailored sensor platform provides a strategy for the early cancer diagnosis and lays the foundation for the construction of a flexible wearable platform.

An ingenious designed dual mode self-powered biosensing platform based on graphdiyne heterostructure substrate for instant hepatocarcinoma marker detection

We report here for the first time a self-powered biosensing platform based on graphene/graphdiyne/graphene (GDY-Gr) heterostructure substrate material for ultrasensitive hepatocarcinoma marker (microRNA-21) detection in both electrochemical and colorimetric test modes. The dual-mode signal intuitively displayed on a smartphone fundamentally improves the detection accuracy. In electrochemical mode, the calibration curve is established in the linear range of 0.1-10000 fM, and the detection limit is as low as 0.333 fM (S/N = 3). Simultaneously, colorimetric analysis of the miRNA-21 is realized by using ABTS as an indicator. The detection limit is confirmed as 32 fM (S/N = 3), and miRNA-21 of concentration from 0.1 pM to 1 nM exhibit a linear relationship with R2 = 0.9968. Overall, the combination of GDY-Gr and multiple signal amplification strategy significantly improved the sensitivity by 310 times compared with traditional enzymatic biofuel cells (EBFCs) based detection platform, showing broad application prospects for on-site analysis and future mobile medical services.

Self-Powered Biosensor for a Highly Efficient and Ultrasensitive Dual-Biomarker Assay

A dual-biomarker, self-powered biosensor was fabricated for the ultrasensitive detection of microRNA-21 (miRNA-21) and miRNA-155 based on enzymatic biofuel cells (EBFCs), catalytic hairpin assembly (CHA), and DNA hybridization chain reaction (HCR), with a capacitor and digital multimeter (DMM). In the presence of miRNA-21, the CHA and HCR are triggered and lead to the generation of a double-helix chain, which stimulates [Ru(NH₃)₆]³⁺ to move to the biocathode surface due to electrostatic interaction. Subsequently, the biocathode obtains electrons from the bioanode and reduces [Ru(NH₃)₆]³⁺ to [Ru(NH₃)₆]²⁺, which significantly increases the open-circuit voltage (E₁^OCV). When miRNA-155 is present, CHA and HCR cannot be completed, resulting in a low E₂^OCV. The self-powered biosensor allows for the simultaneous ultrasensitive detection of miRNA-21 and miRNA-155 with detection limits of 0.15 and 0.66 fM, respectively. Moreover, this self-powered biosensor exhibits the highly sensitive detection for miRNA-21 and miRNA-155 assay in human serum samples.