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MicroRNAs (miRNA) are the potential biomarker for breast cancer, a biosensor for detecting miRNA-21 was successfully prepared by covalently linking carbohydrazide (CON 4 H 6) and tris (4,4 ′- dicarboxylic acid-2,2' - bipyridyl) ruthenium dichloride (Ru (dcbpy) 3 2+) as a self-enhanced emitter (Ru–CON 4 H 6). The biosensor was prepared by coating the electrode with mesoporous silica encapsulated Ru–CON 4 H 6 as luminophores (RMSNs) to covalently link a couple of DNA strands (Q1-H2). The RMSNs coated electrode exhibited strong ECL emission due to the intramolecular electron transfer between the electrochemically oxidized Ru (dcbpy) 3 2+ and co-reactant CON 4 H 6. In the presence of target miRNA-21 and an assistant hairpin H1, H2 could be released from the surface through a strand displacement reaction (SDR), and the reserved Q1 could form G-quadruplex upon the addition of K+. The formed G-quadruplex then interacted with Q2-Fc in the presence of Mg2+ to form a DNA complex on the biosensor surface, which quenched the nano-matrixes propped self-enhanced ECL emission through the electron exchange between Fc and electrode or oxidized ECL intermediates. Under optimal conditions, the ECL decrease showed a correlation with target concentration, leading to a biosensing method for sensitive detection of miRNA-21. The proposed ECL method demonstrated a detectable concentration range from 0.1 fM to 1 nM along with a detection limit of 0.03 fM, good accuracy, and acceptable reproducibility, showing that the self-enhanced ECL biosensing strategy supported by nano-matrix provided a new way for the ultrasensitive detection of miRNA, and promoted the development of breast cancer diagnosis. [ABSTRACT FROM AUTHOR]

The exploitation of accurate and robust photoelectrochemical (PEC) approaches in whole biosensing community counts on the smooth electrons transport and delicate biological design. An aptasensor using depositional rutile titanium dioxide/bismuth vanadate nanoarrays (TiO 2 /BiVO 4 NAs) as photoanode generator and strand-displacement model as nucleic acid frame was developed for microRNA-155 (miRNA-155) detection root in original idea. Photoanode was fabricated via a three-step overlayer deposition procedure including hydrothermal method, electrodeposition and ion beam sputtering. With a sufficient dense of oriented arrays, it provided a solid substrate and fast electronic kinetics reaction during host−guest recognition. In situ yielding electron donors were integrated into the PEC system to provide the most accurate quantitative analysis. The nanoarrays-triggered PEC platform opens another potential perspective in biosensing. • Novel photoelectrochemical emitter TiO 2 /BiVO 4 nanoarrays are firstly synthesized. • TiO 2 /BiVO 4 nanoarrays as well-ordered sensing substrate improve the stability of the biosensor. • In situ photoelectrochemical system is introduced to ensure more accurate photoelectrochemical response. • Strand displacement reaction achieve the sensitive miRNA-155 detection with a low detection limit of 18.2 pM. [ABSTRACT FROM AUTHOR]

The rapid and reliable measurement of procalcitonin (PCT) level exerts a prominent impact on controlling infections and preventing septicemia. This work presents a "signal on-off" electrochemiluminescence (ECL) immunosensor for ultrasensitive PCT detection based on the double quenching effects of Fe 3 O 4 @PDA-Cu x O towards a self-enhanced Ru (bpy) 3 2+-functionalized metal organic framework (MOF). Specifically, mesoporous and hollow MIL-101(Al)–NH 2 is first applied in ECL system to load Ru (bpy) 3 2+ abundantly and stably. Poly (ethylenimine), as the coreactant, is covalently linked with MIL-101(Al)–NH 2 to prevent the leakage of Ru (bpy) 3 2+ and form a self-enhanced Ru complex, thus strong and stable ECL signals are obtained initially. To achieve high-efficiency quenching of "signal on" state, Fe 3 O 4 @PDA-Cu x O-Ab 2 is synthesized tactfully as the quenching probe by which catechol or benzoquinone units in PDA and Cu2+ adsorbed by PDA quench the excited states of Ru (bpy) 3 2+ via electron transfer and resonance energy transfer. In this way, a rapid and robust signal-quenched type ECL immunosensor is developed for PCT measurement with a detection limit of 0.18 pg mL−1 and a dynamic range from 0.0005 ng mL−1 to 100 ng mL−1. Given desirable selectivity, stability and reproducibility, the elaborated ECL immunoassay based on luminescence-functionalized MOF prefigures its great promise in bioanalysis of PCT and other biomarkers. • Mesoporous and hollow MIL-101(Al)–NH 2 is applied in ECL system for the first time. • A self-enhanced ECL complex is prepared by linked PEI with Ru functionalized MOF. • Fe 3 O 4 @PDA-Cu X O can quench Ru (bpy) 3 2+∗ via electron and energy transfer. • Sensitive procalcitonin detection is obtained with good selectivity and stability. [ABSTRACT FROM AUTHOR]

Abstract In this work, by using amorphous bimetallic sulfides of CoSnS x Pd as signal amplifier and magnetic material of Fe 3 O 4 @PPy Au as the substrate, we fabricated an electrochemical immunoassay for N terminal prohormone of brain natriuretic peptide (NT pro BNP). CoSnS x was used as the signal amplifier of the immunosensor for the first time, which was synthesized by fast stoichiometric co-precipitation method. The binary sulfide was identified as an amorphous structure and performed apparent electrochemical behavior. The excellent performance of signal marker was induced by the synergistic effect between SnS 2 and cobalt, as well as the loaded Pd nanoparticles (NPs). Both CoSnS x and Pd NPs presented excellent electrocatalytic activity toward H 2 O 2 oxidation. Moreover, the magnetic nanocomposite of Fe 3 O 4 @PPy Au was firmly immobilized on the magnetic glassy carbon electrode (MGCE) by the magnetic force. The magnetic substrate not only performed good electron conductivity, but also improved the stability of the fabricated electrochemical immunosensor. The developed immunosensor for the NT pro BNP detection exhibited a wide linear response (0.1 pg/mL to 50 ng/mL), and low detection limit of 31.5 fg/mL. In addition, the immunosensor held an excellent analysis capability and broad fascinating application for the detection of other biomarkers in medical diagnosis and treatment. Graphical abstract An electrochemical immunosensor based on amorphous bimetallic sulfides of CoSnS x Pd as signal amplifier and magnetic material of Fe 3 O 4 @PPy Au as the substrate for the NT pro BNP detection. fx1 Highlights • A novel electrochemical immunosensor was designed for detecting NT pro BNP. • CoSnS x was first used as the signal amplifier of the immunosensor and performed apparent electrochemical behavior. • The Fe 3 O 4 @PPy Au as matrix was firmly immobilized on the MGCE by the magnetic force. • It achieved an excellent result in human serum sample analysis. [ABSTRACT FROM AUTHOR]

The biology-material hybrid method for chemical-electricity conversion via microbial fuel cells (MFCs) has garnered significant attention in addressing global energy and environmental challenges. However, the efficiency of these systems remains unsatisfactory due to the complex manufacturing process and limited biocompatibility. To overcome these challenges, here, we developed a simple bio-inorganic hybrid system for bioelectricity generation in Shewanella oneidensis (S. oneidensis) MR-1. A biocompatible surface display approach was designed, and silver-binding peptide AgBP2 was expressed on the cell surface. Notably, the engineered Shewanella showed a higher electrochemical sensitivity to Ag+, and a 60 % increase in power density was achieved even at a low concentration of 10 μM Ag+. Further analysis revealed significant upregulations of cell surface negative charge intensity, ATP metabolism, and reducing equivalent (NADH/NAD+) ratio in the engineered S. oneidensis -Ag nanoparticles biohybrid. This work not only provides a novel insight for electrochemical biosensors to detect metal ions, but also offers an alternative biocompatible surface display approach by combining compatible biomaterials with electricity-converting bacteria for advancements in biohybrid MFCs. [ABSTRACT FROM AUTHOR]

Advanced bioelectronic detection based on the integration of modern optical electronics and biological systems has a broad prospect. The strategy of cathode signal amplification in self-powered photoelectrochemical (PEC) immunosensors with excellent performance is rarely reported in the field of immune analysis. Herein, the work demonstrates a self-powered PEC biosensor formed with BiOI photocathode and WO 3 /SnS 2 /ZnS photoanode, and CsPbBr 3 @COF–V was used as the photocathode signal quenching source for the quantitative monitoring of heart fatty acid binding protein (H-FABP). The high efficiency and stable self-powered biosensor formed not only provides continuous and powerful photocurrent response for bioanalysis through reasonable stepped band structure, but also effectively eliminates the interference of reducing substances. The quenching source CsPbBr 3 @COF–V greatly affects the photocurrent response due to steric hindrance, weak conductivity, competition with the substrate for dissolved oxygen and excitation light source. And the intervention of this key factor achieves multiple signal amplification effect and opens up an innovative vision for self-powered PEC immunosensor. Taking H-FABP as a representative analyte, the proposed signal amplification self-powered photoelectrochemical presents a broad linear range from 0.0005 to 150 ng/mL with the detection limit of 0.19 pg/mL. [ABSTRACT FROM AUTHOR]

Abstract This work reported curcumin quenched electrochemiluminescence (ECL) behavior of luminol with H 2 O 2 as coreactant. To achieve excellent ECL signal, luminol was anchored on Au functionalized MoS 2 /Bi 2 S 3 nanorods (Luminol-Au@MoS 2 /Bi 2 S 3), which not only exhibited super catalysis for H 2 O 2 decomposition to enhance the ECL intensity of luminol/H 2 O 2 system, but also offered a satisfying substrate material for grafting more Au nanoparticles via Au-S binding which was used to adsorb luminol and primary antibodies. As an antioxidant, the hydrophobicity of curcumin limited its bioavailability. Herein, curcumin was conjugated with ZnO nanomaterials (ZnO-CR) to increase its dispersity in water which can make it more bioavailable. Moreover, the possible quenching mechanism between luminol/H 2 O 2 system and ZnO-CR was ascribed to the consumption of superoxide radical (O 2 •−) and energy transfer. The consumption amount of O 2 •− was calculated to be 1.2092 μM/mL through superoxide anion free radical detection kit. Besides, polydopamine was self-polymerized on the surface of ZnO-CR (PDA@ZnO-CR) to anchor secondary antibodies. In optimum parameter, the ECL immunosensor exhibited excellent performance for amyloid-β(Aβ) proteins detection with a wide detection range from 0.05 pg mL−1 to 10 ng mL−1 and a low detection limit of 21 fg mL−1 (S/N = 3). Highlights • Curcumin quenched ECL behavior of luminol with H 2 O 2 as coreactant. • Luminol was anchored on Au functionalized MoS 2 /Bi 2 S 3 nanorods through Au–NH 2 bond. • Curcumin conjugated with ZnO nanomaterials to increase its dispersity in water. • The quenching mechanism was ascribed to consumption of O 2 −• and energy transfer. • The sandwich ECL immunosensor was used to detect amyloid-β proteins. [ABSTRACT FROM AUTHOR]

Abstract An ultrasensitive label-free photoelectrochemical (PEC) immunosensor with high visible-light activity was developed for quantitative detection of amyloid β-protein (Aβ) by cross-linking anti-Aβ antibody onto the Ag 2 S sensitized SnO 2 /SnS 2 nanocomposites. Specifically, SnO 2 with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS 2 , which brought about the sensitization of SnO 2 and enhanced the separation of photogenerated electrons and holes. Moreover, Ag 2 S was in-situ growth on the surface of SnO 2 /SnS 2 , which further enhanced the photocurrent response significantly. Therefore, SnO 2 /SnS 2 /Ag 2 S could form stepwise band-edge structure, which benefited the light harvesting and provided a good foundation for sensor construction and detection. Under optimal conditions, the PEC immunosensor was used to detect the content of Aβ and exhibited a wide linear concentration range from 0.5 pg mL−1 to 100 ng mL−1, with low limit of detection (0.17 pg mL−1) and limit of quantification (0.56 pg mL−1). Additionally, the designed PEC immunosensor exhibited good reproducibility, specificity, and stability which may find potential applications in the biosensor, biomedicine, clinical diagnosis, photocatalysis and other related fields. Highlights • A label-free PEC immunosensor was developed based on SnO 2 /SnS 2 /Ag 2 S nanocomposites. • SnO 2 /SnS 2 /Ag 2 S nanocomposites exhibited excellent photoelectrochemical performance. • The PEC immunosensor displayed highly sensitive detection toward amyloid β-protein. [ABSTRACT FROM AUTHOR]

The establishment of new mechanisms for target identification and signal amplification continues to drive innovation in electrochemiluminescence (ECL) sensing platforms. In this paper, a novel ECL insulin sensing platform was constructed by utilizing the molecular recognition properties of cucurbit[7]uril. Specifically, the macrocyclic host molecule cucurbit[7]uril was immobilized on the surface of the sensing platform as an identification probe, which could selectively capture insulin according to the inherent properties of the protein N-terminal. Introducing the rigid molecule cucurbit[7]uril into the sensing interface could reduce the influence of the environmental parameters on the sensing system, which provides a reliable guarantee for the accurate detection of insulin. Furthermore, gold nanoclusters were modified by utilizing the molecular recognition properties of cucurbit[7]uril, and used as anode signal probes for ECL sensing platform. The macrocyclic molecules cucurbit[7]uril passivated the surface of the nanoclusters, inhibited the non-radiative relaxation and improved the physical stability of the luminophore, leading to a significant increase in the sensitivity and stability of the ECL probe. The ECL sensing platforms exhibited a linear range from 50.00 fg/mL to 100.0 ng/mL, with a detection limit of 5.44 fg/mL. This study revealed the critical role of cucurbit[7]uril in target recognition and signal amplification, extending the scope of supramolecular applications in ECL. [ABSTRACT FROM AUTHOR]

The wide and even whole pH range electrochemiluminescence (ECL) is attractive for steroid estrogens detection under harsh conditions (such as strong acid and alkali). Herein, we presented an efficient europium-based metal-organic framework (Eu-MOF) as ECL luminophore, which has been synthesized via the specific 2, 4-bis(3, 5-dicarboxyphenylamino)-6-oltriazine (H 4 BDPO) ligand with acid-base buffering effect. The functional groups with weak acid and base endowed the H 4 BDPO with eight ionogenic group states, thereout different total charges of H 4 BDPO were derived, thus high and steady ECL signals of Eu-MOF were acquired under different environments with pH = 1.0–14.0. Most notably, combined with the means of UV–vis, fluorescence spectra, cyclic voltammetry (CV) and density functional theory (DFT) calculations, the Eu-MOF has been explored different luminescence mechanisms with variational total charges. The constructed ECL biosensor based on the Eu-MOF realized sensitive detection of trenbolone under wide pH range (In order to maintain the biological activity of antigen and antibody, the studied pH value is 5–8.5), in which the limits of detection were 3.95 fg/mL (pH = 5.0), 2.36 fg/mL (pH = 7.4) and 5.48 fg/mL (pH = 8.5) respectively. This work provides a considerable method to realize efficient trace detection of steroid estrogens under the wide or even whole pH conditions. [ABSTRACT FROM AUTHOR]

A method for the detection of procalcitonin (PCT) with improved accuracy is urgently needed. A dual-mode electrochemical immunosensor with CuCo 2 S 4 –Au bimetallic sulfides as enhancer for accurate detection of PCT was fabricated in this work. The immunosensor not only displays a heavy square wave voltammetry (SWV) signal due to the electron transfer of Cu2+ and Cu+ but not the addition of electron mediators. But also presents high electrocatalytic activity towards H 2 O 2 redox reactions and enhances the detection sensitivity of the amperometric i-t curve (i-t). The introduction of Au nanoparticles, not only improves the conductivity but also has synergistic effects between Au NPs and CuCo 2 S 4 , which promote the detection sensitivity by SWV and i-t. To firmly immobilize antibodies, electrolytic gold was used as the matrix for the immunosensor. Based on a CuCo 2 S 4 –Au dual-signal indicator and electrolytic gold as the matrix, the developed immunosensor for PCT detection in this study demonstrates a wide linear response (0.0001–50 ng/mL) and a low detection limit (SWV: 82.6 fg/mL and i-t : 95.4 fg/mL). Additionally, the fabricated immunosensor exhibited an outstanding analytical approach for PCT and broad application for other biomarkers in clinical diagnosis and treatment. • A dual-mode electrochemical immunoassay was designed for PCT. • CuCo 2 S 4 –Au was first used as a dual-signal indicator of the immunosensor. • PCT detection results were established by F-test and t-test. • It achieved an excellent result in human serum sample analysis. [ABSTRACT FROM AUTHOR]

The point of fabricating ultrasensitive electrochemiluminescence (ECL)-based biosensors should be focused on how to maintain high immune recognition of antigens by antibodies in whole process. That is not effortless due to the structure of the protein can be destroyed root in toxic nanocarriers, excessive cyclic potential and superoxide radicals in coreactant, all of which can lead to reduce the bioactivity of antigen and antibody. In this work, the effect of negative voltage and divers coreactant on protein bioactivity were verified. Based on that, a motivated ECL biosensor with good biocompatibility was fabricated for procalcitonin (PCT) detection using Au nanoclusters (Au NCs) as low-potential cathodic luminophor and K 2 S 2 O 8 as non-toxic coreactant, respectively. Besides, highly-branched Cu 2 O was utilized to catalyze K 2 S 2 O 8 and produce more radical anion SO 4 •−, which can oxidize Au NCs•− to generate more high-energy-state Au NCs*, thus doubling the ECL intensity to meet the requirements of trace analysis. In addition, protein A (PA) as specific antibody capturer was employed to bind the Fc region of anti-PCT in an orientated way, further maintaining the physiological activity of antibody. As expected, all strategies undoubtedly practically improved the immune recognition of the biosensor and reduced the detection limit to 2.90 fg/mL. Image 1 • Highly-branched Cu 2 O electroplated on ITO surface was utilized as well-ordered co-reaction accelerator. • −BSA-templated Au NCs as ECL emitter exhibited low luminous potential of -1.2 V. • Protein A (PA) as site-oriented antibody immobilizer was utilized to achieve high specificity. • This proposed ECL biosensor exhibited ultralow detection limit of 2.90 fg/mL. [ABSTRACT FROM AUTHOR]