Ultrasensitive Biosensor Research Articles

Signal amplification strategy based on target-controlled release of mediator for ultrasensitive self-powered biosensing of acetamiprid

Self-powered biosensors with high sensitivity have garnered significant interest for their potential applications in the realm of portable sensing. Herein, a self-powered biosensor with a novel signal amplification strategy was developed by integrating target-controlled release of mediator with an enzyme biofuel cell for the ultrasensitive detection of acetamiprid (ACE). Zeolitic imidazolate framework-67 was utilized as both a nanocontainer for capturing the electron mediator 2,2′-azidobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and a precursor for the synthesis of cobalt nanoparticles/nitrogen, sulfur-codoped carbon nanotubes (Co NPs/NS-CNTs), which were employed as the electrode material for constructing both the glucose oxidase-based bioanode and the laccase-based biocathode. The target analyte ACE can specifically bind to its aptamer, leading to the release of ABTS, which cyclically participates in the catalytic reaction of the biocathode, thereby amplifying the electrochemical signal. By leveraging the benefits of ABTS cyclic catalysis and the effective electrocatalysis of bioelectrodes based on Co NPs/NS-CNTs, the self-powered biosensor has a broad detection range of 0.1–1000 fM and a low detection limit of 25 aM toward ACE. The proposed signal amplification approach presents a promising strategy for enhancing sensitivity and enabling portable analysis in applications of food safety, environmental monitoring, and medical diagnostics.

Ultrasensitive Electrochemical Biosensor for Rapid Screening of Chemicals with Estrogenic Effect.

Estrogenic chemicals are widely distributed and structurally diverse. They primarily disrupt estrogen-related metabolism in animals or humans by mimicking the agonistic receptor effects of natural estrogens, thereby influencing the transcription of estrogen receptors to regulate their quantity and sensitivity. This disruption of estrogen-related metabolism can lead to estrogen-related effects, posing risks to biological health, emphasizing the urgent need for simple and effective methods to screen compounds with estrogenic effects. Herein, a new electrochemical biological effect biosensor based on human estrogen receptor α (hERα) is developed, which uses hERα as the biorecognition element and employs the electroactive horseradish peroxidase (HRP) labeled 17β-estradiol (E2) multifunctional conjugate HRP-E2 as the signal-boosting element and ligand competition agent. Based on the specific ligand-receptor interaction principle between the target and nuclear receptor, by allowing the test compound to compete with HRP-E2 conjugate for binding to hERα and testing the electrocatalytic signal of the conjugate that fails to bind to the hERα estrogen receptor, rapid screening and quantitative detection of chemical substances with estrogenic effect have been achieved. The biosensor shows a wide linear range of 40 pM to 40 nM with a detection limit of 17 pM (S/N = 3) for E2, and the detection limit is 2 orders of magnitude better than that of the previously reported sensors. The biosensor based on ligand-receptor binding can not only quantitatively analyze the typical estrogen E2, but also evaluate the relative estrogen effect strength of other estrogen compounds, which has good stability and selectivity. This electrochemical sensing platform displays its promising potential for rapid screening and quantitative detection of chemicals with estrogenic effects.

Asymmetric Nanobowl Confinement-Engineered "Plasmonic Storms" for Machine Learning-Assisted Ultrasensitive Immunochromatographic Assay of Pathogens.

Efficient field enhancement effects through plasmonic chemistry for ultrasensitive biosensing still face a great challenge. Herein, nanoconfinement engineering accumulation and synergistic effects are used to develop a "plasmonic storms" strategy with a high field enhancement effect, and gold nanoparticles (AuNPs) are used as active sites for a proof of concept because of their distinctive localized surface plasmon resonance and neighborly coupled electromagnetic field. Briefly, a large number of AuNPs are selectively and accurately stacked in the confined nanocavity of the bowl-like nanostructure through an in situ-synthesized strategy, which provides a space for strong coupling of electromagnetic fields between these adjacent AuNPs, forming "plasmonic storms" with an enhanced field that is 3 orders of magnitude higher than that of free AuNPs. The proposed nanoconfinement-engineered "plasmonic storms" are demonstrated by surface-enhanced Raman scattering (SERS) and photothermal experiments and theoretically visualized by finite element simulation. Finally, the proposed "plasmonic storms" are used for enhanced colorimetric/SERS/photothermal immunochromatographic assay to detect Salmonella typhimurium with the help of a machine learning algorithm, achieving a low limit of detection of 142 CFU mL-1, highlighting the potential of nanoconfinement in biosensing.

Ultrasensitive Electrochemical Biosensor with Powerful Triple Cascade Signal Amplification for Detection of MicroRNA.

In this work, by ingeniously integrating catalytic hairpin assembly (CHA), double-end Mg2+-dependent DNAzyme, and hybridization chain reaction (HCR) as a triple cascade signal amplifier, an efficient concatenated CHA-DNAzyme-HCR (CDH) system was constructed to develop an ultrasensitive electrochemical biosensor with a low-background signal for the detection of microRNA-221 (miRNA-221). In the presence of the target miRNA-221, the CHA cycle was initiated by reacting with hairpins H1 and H2 to form DNAzyme structure H1-H2, which catalyzed the cleavage of the substrate hairpin H0 to release two output DNAs (output 1 and output 2). Subsequently, the double-loop hairpin H fixed on the electrode plate was opened by the output DNAs, to trigger the HCR with the assistance of hairpins Ha and Hb. Finally, methylene blue was intercalated into the long dsDNA polymer of the HCR product, resulting in a significant electrochemical signal. Surprisingly, the double-loop structure of the hairpin H could prominently reduce the background signal for enhancing the signal-to-noise ratio (S/N). As a proof of concept, an ultrasensitive electrochemical biosensor was developed using the CDH system with a detection limit as low as 9.25 aM, achieving favorable application for the detection of miRNA-221 in various cancer cell lysates. Benefiting from its enzyme-free, label-free, low-background, and highly sensitive characteristics, the CDH system showed widespread application potential for analyzing trace amounts of biomarkers in various clinical research studies.

Chitosan-coated iron(III) oxide nanoparticles and tungsten disulfide quantum dots-immobilized Fiber-based WaveFlex Biosensor for Staphylococcus Aureus bacterial detection in real food samples

The research proposes and investigates an extraordinarily sensitive, label-free WaveFlex biosensor utilizing optical fiber technology for the detection of Staphylococcus aureus (S. aureus), a common foodborne bacterium. The WaveFlex biosensor (plasmon Wave based Flexible optical fiber Biosensor) is based on a novel flexible tapered single-mode fiber structure, utilizing gold nanoparticles (AuNPs) to trigger the phenomenon of localized surface plasmon resonance (LSPR). Additionally, the sensitivity is further enhanced using chitosan-coated iron(III) oxide nanoparticles (Fe3O4–CS NPs) and tungsten disulfide quantum dots (WS2-QDs). The optical fiber surface is functionalized with antibodies to achieve specific detection of S. aureus. For S. aureus concentrations at 1 × 108 CFU/mL (colony-forming units per milliliter), the sensor's maximum sensitivity of 2.74 nm/lg (CFU/mL), and a detection limit (LOD) of 6.67 CFU/mL. This ultra-sensitive biosensor holds great potential for widespread applications in various fields, including disease detection, medical diagnostics, and food safety inspection.

Ultra-sensitive Two-dimensional Photonic Crystal Biosensor for Oral Cancerous Cell Detection

Background & Objectives: Over the past two decades, biophotonic sensors based on two-dimensional (2D) photonic crystals (PhCs) have garnered significant attention in cancer diagnosis. This technology has become a crucial tool in early cancer detection and treatment response monitoring due to its ability to detect minute changes in biomarker concentrations and molecular interactions. The development of these sensors through advanced nano and microfabrication techniques has significantly improved diagnostic accuracy and speed, promising substantial enhancements in therapeutic outcomes for cancer patients. Materials & Methods: A biosensor based on a 2D PhC was designed and simulated for the detection of oral cancer cells in a sample. The biosensor, structured with silicon rods in air using the Finite-Difference Time-Domain tool, utilizes five rods as an analyte for detecting normal and cancerous cells, thereby evaluating the sensor’s performance. Results: The variation in the transmission spectrum was studied to detect the presence of malignant cells in the test sample. The sensor’s structural parameters were carefully adjusted to enhance its sensitivity, a crucial factor in the accurate detection of cancerous cells. Two critical parameters, Q-factor and sensitivity, were derived from the results. The sensor achieved a sensitivity of 1148 nm/RIU with a Q-factor of 193. Conclusion: The designed biosensor demonstrates superior accuracy and sensitivity in identifying both malignant and normal cells in the test sample, making it suitable for real- time deployment in point-of-care applications.

Ultrasensitive electrochemiluminescence biosensor constructed by luminol-diazonium ion functionalized Au/MXene nanocomposites for early stage detection of disease in human

MicroRNAs (miRNAs) are important biomarkers for tracking occurrence and development of many diseases, therefore, the reliable, sensitive, fast and accurate detection of miRNAs plays an extremely critical role in clinic diagnosis and treatment of early stage diseases. Herein, we developed ultrasensitive electrochemiluminescence (ECL) biosensor constructed by luminol-diazonium ion functionalized Au/MXene nanocomposites for early stage detection of kidney disease in human. The synergistic effect of MXene and Au nanoparticles significantly enhanced the ECL emission of luminol up to 6.9-fold due to their shortened electron transfer distance and excellent catalytic performance. The loading efficiency of luminol on MXene could be as high as ∼7 %, enabling the enrichment of luminol on MXene nanosheets. The enhanced ECL signal and excessive loading of luminol allowed the Au-MXene-luminol as an excellent ECL labeling agent, which was further developed for the determination of miRNA-377 according to the sandwich-like assay. The as-developed miRNA-377 biosensor had ultrahigh sensitivity, wide linear range (from ∼50 aM to ∼1 nM), low limit of detection (∼13.2 aM) and high selectivity (∼82.6 %) for highly homologous miRNA with mismatched single-bases. The ultrasensitive ECL biosensor was successfully applied to determine miRNA-377 in the serum samples of early stage kidney patients, which were well consistent with the clinic standard of quantitative real-time polymerase chain reaction method. The ultrasensitive ECL-labeling biosensor with high selectivity is very promising for universally screening any kinds of biomarkers with corresponding specific targets.

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.

An ultrasensitive electrochemical biosensor with dual-amplification mode and enzyme-deposited silver for detection of miR-205-5p.

An electrochemical biosensor based on dual-amplified nucleic acid mode and biocatalytic silver deposition was constructed using catalytic hairpin assembly-hybrid chain reaction (CHA-HCR). The electrochemical detection of silver on the electrode by linear sweep voltammetry (LSV) can be utilized to quantitatively measure miR-205-5p since the amount of silver deposited on the electrode is proportional to the target nucleic acid. The current response values exhibit strong linearity with the logarithm of miR-205-5p concentrations ranging from 0.1pM to 10μM, and the detection limit is 28 fM. A consistent trend was found in the results of the qRT-PCR and electrochemical biosensor techniques, which were employed to determine the total RNA recovered from cells, respectively. Moreover, the constructed sensor was used to assess miR-205-5p on various cell counts, and the outcomes demonstrated the excellent analytical efficiency of the proposed strategy. Therecoveries ranged from 97.85% to 115.3% with RSDs of 2.251% to 4.869% in human serum samples. Our electrochemical biosensor for miR-205-5p detection exhibits good specificity, high sensitivity, repeatability, and stability. It is a potentially useful sensing platform for tumor diagnosis and tumortype identificationin clinical settings.

Confinement-enhanced electrochemiluminescence of copper nanoclusters on 3D layered double hydroxide for ultrasensitive detection of GFAP

In this work, the copper nanoclusters (Cu NCs) were confined on 3D layered double hydroxide (3D-LDH) to form Cu NCs@3D-LDH with outstanding electrochemiluminescence (ECL) for constructing ultrasensitive biosensor to detect of glial fibrillary acidic protein (GFAP) implicated in Alzheimer's Disease (AD). More importantly, compared to the individual Cu NCs, Cu NCs@3D-LDH presented strong and stable ECL response, since 3D-LDH could not only gather more Cu NCs but also limit the intramolecular free motion to reduce nonradiative transition for obtaining high ECL intensity. In addition, the improved cascade amplification method combining proximity ligation assay (PLA) with DNAzyme could transform tiny amount of target protein into a large amount of output DNA to improve sensitivity of biosensor. The ECL biosensor realized ultrasensitive detection of GFAP with the detection limit of 2 ag/mL and it had been successfully applied to the evaluation of GFAP in the serum of patients with neurological diseases. This research offered a general and facile method to improve ECL performance of Cu NCs for sensitive detection of biomarkers for disease diagnosis.

Ultrasensitive Electrochemiluminescence Biosensor Based on DNA-Bio-Bar-Code and Hybridization Chain Reaction Dual Signal Amplification for Exosomes Detection.

Exosomes have received considerable attention as potent reference markers for the diagnosis of various neoplasms due to their close and direct relationship with the proliferation, adhesion, and migration of tumor. The ultrasensitive detection of cancer-derived low-abundance exosomes is imperative, but still a great challenge. Herein, we report an electrochemiluminescence (ECL) biosensor based on the DNA-bio-bar-code and hybridization chain reaction (HCR)-mediated dual signal amplification for the ultrasensitive detection of cancer-derived exosomes. In this system, two types of aptamers were modified on the magnetic nanoprobe (MNPs) and gold nanoparticles (AuNPs) with numerous bio-bar-code DNA, respectively, which formed "sandwich" structures in the presence of specific target exosomes. The "sandwich" structures were separated under magnetic field, and the numerous bio-bar-code DNA were released by dissolving AuNPs. The released bio-bar-code DNA triggered the HCR procedure to produce a good deal of long DNA duplex structure for embedding in hemin, which generated strong ECL signal in the presence of coreactors for ultrasensitive detection of exosomes. Under the optimal conditions, it exhibited a good linearly of exosomes ranging from 10 to 104 exosomes particle μL-1 with limit of detection down to 5.01 exosome particle μL-1. Furthermore, the high ratio of ECL signal and minor change of ECL intensity indicated the good specificity, stability, and repeatability of this ECL biosensor. Given the good performance for exosome analysis, this ultrasensitive ECL biosensor has a promising application in the clinical diagnosis of early cancers.

Electron-Accelerator-Induced Fast Electron Transfer for Enhancing Electrochemiluminescence of Gold Nanoclusters and Its Bioanalysis Application: A Novel Avenue for Developing High-Efficient Emitters.

Herein, the gold nanoclusters/CaFe2O4 nanospheres (Au NCs/CaFe2O4) heterostructure as a novel electrochemiluminescence (ECL) emitter was developed. Excitingly, Au NCs/CaFe2O4 displayed highly efficient and greatly stable ECL based on the newly defined electron-accelerator p-type semiconductor CaFe2O4 NS-induced fast electron transfer; it solved one key obstacle of metal NC-based ECL emitters: sluggish through-covalent bond electron transport kinetics-caused inferior ECL performance. Specifically, on account of the energy level matching between emitter Au NCs and electron-accelerator CaFe2O4 NSs, the valence band (VB) of the electron-accelerator could provide abundant holes for rapidly transporting the electrogenerated electron from the highest occupied molecular orbital (HOMO) of Au NCs to the electrode, generating massive excited species of Au NCs for strong ECL emission. Notably, Au NCs/CaFe2O4 emerged 5.4-fold higher ECL efficiency with 3.5-fold higher electrochemical oxidation current in comparison with pure Au NCs, exhibiting great prospects in extensive lighting installations, ultrasensitive biosensing, and high-resolution ECL imagery. As applications, an ECL bioassay platform was constructed with Au NCs/CaFe2O4 as an emitter and U-like structure-fueled catalytic hairpin assembly (U-CHA) as a signal amplifier for fast and trace analysis of aflatoxin B1 (AFB1) with the detection limit (LOD) down to 2.45 fg/mL, which was 3 orders of magnitude higher than that of the previous ECL biosensors with much better stability. This study developed an entirely new avenue for enlarging the ECL performance of metal NCs, and it is a very attractive orientation for directing the reasonable design of prominent metal NC-based ECL emitters and broadening the practical application of metal NCs.

High-Efficient Electrochemiluminescence of DNA-Au Ag Nanoclusters with Au NPs@Ti3C2 as a Novel Coreaction Accelerator for Ultrasensitive Biosensing.

In this work, an ultrasensitive electrochemiluminescence (ECL) biosensor was constructed based on DNA-stabilized Au Ag nanoclusters (DNA-Au Ag NCs) as the efficient luminophore and Au NPs@Ti3C2 as a new coreaction accelerator for determining microRNA-221 (miRNA-221) related to liver cancer. Impressively, DNA-Au Ag NCs were stabilized by the high affinity of the periodic 3C sequence, exhibiting an excellent ECL efficiency of 27% compared with classical BSA-Au Ag NCs (16%). Moreover, the Au NPs@Ti3C2 nanocomposites, as a new coreaction accelerator, were first introduced to accelerate the production of abundant sulfate free radicals (SO4•-) for promoting the ECL efficiency of DNA-Au Ag NCs in the DNA-Au Ag NCs/Au NPs@Ti3C2/S2O82- ternary system due to the energy band of Au NPs@Ti3C2 being well-matched with the frontier orbital of S2O82-. Furthermore, the trace target (miRNA-221) could drive the rolling circle amplification to generate an amount of output DNA with periodic 3C and 10A sequences. Through covalent bonds on the surface of poly A and Au NPs, the distance between the luminophor and the coreaction accelerator could be narrowed to further enhance the detection sensitivity. As a result, the constructed sensor has been applied for the ultrasensitive detection of miRNA-221 with a low detection limit of 50 aM and successfully monitored miRNA-221 in MHCC-97L and HeLa cell lysates. This strategy could be utilized for guiding the synthesis of light-emitting DNA-metal NCs, which has great potential in the construction of ultrasensitive biosensors for the early diagnosis of diseases.

Filamentous bacterial nanocelluloses decorated with dense Au nanoparticles for developing ultrasensitive SERS biosensors

Based on hydrogen peroxide (H2O2)-modified bacterial nanocelluloses (BNCs(M)), we report in-situ overgrowth of highly dense plasmonic Au nanoparticles (NPs) on these filamentous three-dimensional (3D) supports by an ingenious “green” photochemical strategy. The measured relative atomic ratio of Au element in the resultant BNCs(M)@Au NPs is ∼ 13 times higher than that formed on pristine BNCs. The BNCs(M)@Au NPs exhibit a higher surface-enhanced Raman scattering spectroscopy (SERS) activity than the reference BNCs@Au NPs. The flexible SERS biosensors enable the label-free detection limit of glucose molecules to be achieved as low as 10−10 M, surpassing many reports in previous works and then facilitating the ultrasensitive evaluation of glucose metallic diseases.

Dual amplification dynamic DNA network system for CRISPR/Cas12a based p53 gene detection

BackgroundIt is estimated that over 50 % of human cancers are caused by mutations in the p53 gene. Early sensitive and accurate detection of the p53 gene is important for diagnosis of cancers in the early stage. However, conventional detection techniques often suffer from strict reaction conditions, or unsatisfied sensitivity, so we need to develop a new strategy for accurate detection of p53 gene with smart designability, multiple signal amplification in mild reaction conditions. ResultsIn this study, CRISPR/Cas system is exploited in entropy-driven catalysis (EDC) and hybridization chain reaction (CHA) dual signal amplification sensing strategies. The products of both reactions can efficiently and separately activate CRISPR/Cas12a which greatly amplifies the fluorescent signal. The method has good linearity in p53 detection with the concentration ranged from 0.1 fM to 0.5 pM with ultra-low detection limit of 0.096 fM. It also showed good performance in serum, offering potentials for early disease detection. SignificanceThe designed dual amplification dynamic DNA network system exhibits an ultra-sensitive fluorescence biosensing for p53 gene identification. The method is simple to operate and requires only one buffer for the experiment, and meanwhile shows smart designability which could be used for a wide range of markers. Thus, we believe the present work will provide a potential tool for the construction and development of sensitive fluorescent biosensors for diseases.

High-efficiency electrochemiluminescence of host-guest ligand-assembled gold nanoclusters preoxidated for ultrasensitive biosensing of protein

Herein, host–guest ligand-assembled gold nanoclusters (AuNCs) with highly efficient electrochemiluminescence (ECL) as an emitter and a programable tripedal deoxyribonucleic acid (DNA) walker with a well-regulated DNA track as the signal amplifier were used to develop an ultrasensitive biosensing platform for determining soluble urokinase-type plasminogen activator receptor (suPAR) related to chronic kidney disease. Notably, the host–guest ligand-assembled AuNCs with 6-aza-2-thiothymine (ATT) as the ligand and guanidine butyric acid (Gba) as the model (Gba/ATT-AuNCs) exhibited a strong and stable ECL signal under preoxidation, 25.6 times higher than that of traditional ATT-protected AuNCs (ATT-AuNCs). This is because of the dual-enhancement ECL mechanism of the suppression of nonradiative transitions by host–guest recognition and the improvement of the electrochemical redox rate by preoxidation. Furthermore, the trace target protein suPAR could be efficiently converted into a tripedal DNA walker to walk along a well-regulated square DNA orbit with high movement efficiency and low background signal, thereby considerably improving detection sensitivity. Thus, the established ECL sensing platform achieved the ultrasensitive detection of suPAR with a linear range from 10 fg/mL to 10 ng/mL and a limit of detection of 3.15 fg/mL, whose detection sensitivity was five orders of magnitude higher than that of the gold-standard enzyme-linked immunosorbent assay with the lowest detection concentration of 1 ng/mL. This strategy provides a novel enhanced ECL mode of AuNCs for constructing a sensitive biosensing platform and is expected to be extended to the trace detection of other protein markers in human body fluids for disease diagnosis.

Recent advances in ultrasensitive electrochemical sensors and biosensors for determination of antibiotics in environment samples

Recent advances in ultrasensitive electrochemical sensors and biosensors for determination of antibiotics in environment samples

Nanozyme-mediated signal amplification on g-C3N4/NaBiO3 Z-scheme heterojunction photoelectrode toward ultrasensitive photoelectrochemical immunoassay for prostate-specific antigen

A sandwich-type photoelectrochemical (PEC) immunosensor for prostate-specific antigen (PSA) detection was developed using the g-C3N4/NaBiO3 (CN/NBO) Z-scheme heterojunction as the photoelectrode and glutathione-Cu/Cu2O nanozyme (GSH-Cu/Cu2O NPs) as the signal amplifier. The unique Z-scheme charge-carrier migration pathway of the CN/NBO heterojunction significantly promotes the separation and migration of photogenerated electron-hole pairs, producing a high photocurrent response of the photoelectrode. GSH-Cu/Cu2O NPs with ascorbic acid oxidase (AAO) activity were introduced into the PEC immunosensing system through immunoreactions for signal amplification. Signal amplification was achieved through double photocurrent quenching of the GSH-Cu/Cu2O NPs on the photoelectrode. On the one hand, GSH-Cu/Cu2O NPs as AAO catalyzed ascorbic acid (AA), an electron donor in the PEC system, to produce dehydroascorbic acid (DHA), leading to a decrease in the photocurrent response. On the other hand, the GSH-Cu/Cu2O NPs prevented AA transfer from the detection solution to the interface of the photoelectrode, further aggravating the PEC signal quenching effect. Benefiting from the excellent performance of the Z-scheme heterojunction-based photoelectrode, the dual signal quenching effect of GSH-Cu/Cu2O NPs, the PEC immunosensor showed an ultralow detection limit of 5.1 × 10−15 g mL−1. By coupling a Z-scheme heterojunction-based photoelectrode with a nanozyme-mediated signal amplification strategy, this study provides a novel avenue for the construction of ultrasensitive and convenient biosensing systems.

Ultrasensitive Paper-Based Photoelectrochemical Biosensor for Acetamiprid Detection Enabled by Spin-State Manipulation and Polarity-Switching.

Efficient carrier separation is vitally crucial to improving the detection sensitivity of photoelectrochemical (PEC) biosensors. Here, we developed a facile strategy to efficiently regulate the carrier separation efficiency of the photoactive matrix BiOI and In2S3 signal label functionalized paper chip by manipulation of electrons spin-state and rational design of electron transport pathways. The spin-dependent electronic structures of BiOI and In2S3 were regulated via enhanced electron-spin parallel alignment induced by an external magnetic field, markedly retarding carrier recombination and extending their lifetime. Simultaneously, with the progress of the target-induced catalytic hairpin assembly process, the transfer path of photogenerated carriers was changed, leading to a switch in photocurrent polarity from cathode to anode. This reversed electron transport pathway not only boosted the separation ability of photogenerated electrons but also eliminated false-positive and false-negative signals, thereby further improving the detection sensitivity. As a proof of concept, the well-designed magnetic field-stimulated paper-based PEC biosensor showed highly selectivity and sensitivity for acetamiprid assay with a wide linear range of 1 fM to 20 nM and an ultralow detection limit of 0.73 fM. This work develops a universal strategy for improving the sensitivity of biosensors and exhibits enormous potential in the fields of bioanalysis and clinical diagnosis.

Ultrasensitive self-powered biosensor with facile chemical signal amplification strategy using hydrogen peroxide-triggered silver oxidation reaction

The amplification strategies used for self-powered biosensor based on biofuel cell (BFC-SPB) need to be further developed. Because the currently developed strategies utilized the complicated hybridization of DNA or poorly readable current signal of capacitors for amplification, which limits the practical application in public health emergencies. Here, we present a facile chemical amplification strategy for BFC-SPB. The 5-min amplification was triggered by simply adding H2O2 solution dropwise to the sensing cathode after the formation of the immune sandwich. The Ag NP of immunoprobe were oxidized to Ag(I), which can be served as the electron acceptor of the cathode. The amount of immunoprobe was positively correlated with that of the antigen, resulting in corresponding and high concentration of Ag(I) after the amplification, which enhanced the ability of the cathode as the electron acceptor. Meanwhile the glucose oxidation reaction (GOR) was performed on the bioanode modified with glucose oxidase (GOx). After assembling the bioanode and sensing cathode, the open circuit voltage of the BFC-SPB, measured by digital multimeter, distinctly rised with the elevated concentration of the antigen. To demonstrate the proof of concept, immunoglobulin G (IgG), selecting as a model analyte, was sensitively detected using this method. Result indicated that the limit of detection was 4.4 fg mL−1 (0.03 amol mL−1) in the linear range of 1 pg mL−1-10 μg mL−1. This work initiates a brand-new way of chemical amplification strategy for BFC-SPB, and offers a promising platform for practical applications.