Search

The occurrence of Alzheimer's disease (AD) is strongly associated with the progressive aggregation of a 42-amino-acid fragment derived from the amyloid-β precursor protein (Aβ 1-42). Therefore, it is crucial to establish a versatile platform that can effectively detect Aβ 1-42 to aid in the early-stage preclinical diagnosis of AD. Herein, we introduce a specialized split-type analytical platform that enables sensitive and accurate monitoring of Aβ 1-42 based on a self-corrected photoelectrochemical (PEC) sensing system. To realize this design, gelatinized Ti 3 C 2 @Bi 2 WO 6 Schottky heterojunctions were prepared and served as photoelectrodes for tackling the photoinduced charge carriers. Functionalized CaCO 3 @CuO 2 nanocomposites were used as signal converters to detect Aβ 1-42 and amplify the signal further. Benefiting from the glucose oxidation induced acid microenvironment and H 2 O 2 output, the nanocomposites are able to rapidly decompose, producing Ca2+ and Fenton-like catalyst Cu2+. The Cu2+-driven Fenton-like reaction generated ·OH, which accelerated the 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. Additionally, Ca2+ was cross-linked with alginate inducing gelation on the surface of Ti 3 C 2 @Bi 2 WO 6 Schottky heterojunctions, influencing mass transfer and light absorption. Eventually results in the shift of photocurrent, allowing for precise quantification with a detection limit of 0.06 pg mL−1. The combination of colorimetric variation and the photoelectric effect provide a more accurate and reliable result. This research opens up new possibilities for constructing PEC platforms and beyond. [ABSTRACT FROM AUTHOR]

Abstract The construction of a photoelectrochemical (PEC) strategy for multi-component detection represents a great challenge in the field of sensing. To address these challenges, herein we presented a hollow-channel paper-based PEC analytical platform based on chemiluminescence (CL) addressable strategies excited PEC strategy for multiplexed sensing application. Sandwich-structured CdS quantum dots (QDs)/reduced graphene oxide (RGO)/ZnO nanorods arrays (NRAs) heterostructure where CdS serves as visible light sensitizers, RGO acts as an electron relay between ZnO NRAs and CdS QDs, were simply assembled on the gold nanoparticles modified paper working photoelectrode (Au-PWE). The PEC performance of the CdS/RGO/ZnO can be greatly improved benefiting from the formation of type II band alignment between CdS QDs and ZnO NR as well as the super charge collection and shuttling property of RGO. Multiplexed CL emission could be achieved through controlling the CL co-reagents transport. By the virtue of CL addressable technique and the excellent PEC activity of CdS/RGO/ZnO, a highly sensitive, and selective multiple microRNAs (miRNAs) quantification method was achieved. Such a tailored strategy would break the bottleneck of the current PEC detection techniques in multiplex tracing, as well as serve as a novel concept for designing multi-channel PEC sensing method. Highlights • A high-throughput photoelectrochemical device was constructed on hollow-channel paper based device. • Sandwich-structured CdS quantum dots/reduced graphene oxide /ZnO nanorods heterostructure was prepared. • Functionalized hollow-channel with different capillary forces was created to control the fluids flow rate. • Successive chemiluminescence emission can be realized to excite the photoactive materials based on the flow rate controlling. [ABSTRACT FROM AUTHOR]

The photoelectrochemical (PEC) technique has resulted in substantial progress in chemical sensing applications. However the complicated photoelectrode modification procedures would enable undesired background noise and decreasing sensitivity. Hence, it is important to explore a new approach alternative to inconvenient substrate modification. Herein, inspired by the stimuli-responsive drug delivery systems, an innovative PEC system is developed for efficiently microRNA-21 (miRNA-21) tracing. Hierarchical nanocomposites based on hematite (α-Fe 2 O 3 ) coated self-ordered titanium dioxide nanorod arrays (TiO 2 NRAs) exhibited enhanced response to solar light, promoted charge carrier separation and transfer efficiency was adopted as photoelectrode directly. Functional mesoporous silica nanomaterial (MSN) is prepared as nanocarriers for efficient loading of Cu 2+ , further capped with miRNA-21 responsive capture RNA probe. Thereafter, the capture RNA probe endows the functional MSN with responsiveness to miRNA-21. With the presence of miRNA-21, this system is thus triggered and a quickly release of capped Cu 2+ occurs due to the dissociation of capture RNA probe presented on the MSN surface via base-pair hybridization. The released Cu 2+ was then served as electron acceptor reduced to Cu° at the counter electrode to enhance electron-hole pair separation efficiency, leading to a promoted photocurrent response. Consequently, the miRNA-21 can be accurately quantified. Taking advantage of its sensitivity and specificity, this versatile strategy demonstrates a new route for the design PEC sensing approach without any photoelectrode modification procedure, and holds great potential for biosensing and clinical diagnosis. [ABSTRACT FROM AUTHOR]

A microfluidic paper-based analytical device (μPAD) was simply constructed for highly sensitive detection of L -glutamic acid and L -cysteine. The μPAD featured with two functional zones on one strip of paper achieved by preferable multi-plate ZnO nanoflowers (ZnO NFs) and molecularly imprinting polymer (MIP) membranes. The as-designed μPAD was established based on the inherent relation between the photo-oxidation products and photoelectrochemical (PEC) performance with the highly sensitive detection of biomolecules. The ZnO NFs were utilized to produce photo-oxidation products by driving the reaction between ferrocenemethanol and photogenerated holes under ultraviolet light. The photo-oxidation products easily flowed to MIP membranes along the hydrophilic channel via capillary action. MIP membranes as the receptors specifically recognized the analytes as well as decreased the electron loss by blocking the reduction reaction between electrons and photo-oxidation products. The PEC response was obtained in the processes of electrons transfer and exhibited the direct relationships corresponding to the concentrations of target analytes. The μPAD showed the detection limits toward L -glutamic acid and L -cysteine as low as 9.6 pM and 24 pM, respectively. Moreover, it is interesting to point out that ZnO NFs nanostructure shows superior PEC signal compared with those of ZnO nanospheres, nanosheets, and nanorod arrays. In current work, photo-oxidation products are utilized to achieve highly sensitive PEC detection for biomolecules under ultraviolet light as well as avoid the effects of multiple modifications in the same region on the reproducibility, which is beneficial for opening up rich possibility for designing more efficient analytical strategy. [ABSTRACT FROM AUTHOR]

This work described that one–step synthesis three dimensional anatase hierarchically cactus–like TiO 2 arrays (AHCT) and their application in constructing a novel photoelectrochemical (PEC) and visualized sensing platform based on molecular imprinting technique, which reports its result with the prussian blue (PB) electrode served as the electrochromic indicator for the detection of glycoprotein (RNase B). The AHCT arrays were perpendicularly grown on FTO substrate with tunable sizes, offering many advantages, such as large contact area, rapid charge electron separation and transport. A possible formation process of the interesting AHCT arrays has been investigated based on time–dependent experiment. In addition, the PEC and visualized sensing platform was constructed based on the molecularly imprinted polymer modified AHCT arrays. Specifically, in the proposed system, the more RNase B being, the more insulating layer was formed on the surface of AHCT arrays that impeded the harvesting of light and electron transfer, resulting in the reduction of photocurrent. When upon light illumination, the photogenerated electrons flow through an external circuit to PB, leading to the reduction of PB to prussian white (PW), which is transparent. The rate of decolourization of PB is proportional to the concentration of RNase B. In this way, a visualized PEC sensing platform that gives its quantitative information could be performed by monitoring the change of color intensity. Under optimal conditions, the protocol possessed a detection range of 0.5 pM to 2 μM (r=0.997) and the limit of detection was 0.12 pM toward RNase B. Our method eliminates the need for sophisticated instruments and high detection expenses, making it possible to be a reliable alternative in resource–constrained regions. [ABSTRACT FROM AUTHOR]

In this study, based on in situ generation of CdS quantum dots (QDs) on the surface of branched TiO 2 (B-TiO 2 ) nanorods, an solar innovative photoelectrochemical (PEC) sensing platform was constructed for real-time, and sensitive detection of cellular H 2 S. Specifically, B-TiO 2 nanorods arrays consisting of TiO 2 nanorods directly grown on fluorine-doped tin oxide (FTO) further using TiCl 3 mediated surface treatment of TiO 2 nanorods are designed and fabricated as a new type of photoelectrode. CdS quantum dots (QDs) was formed on the surface of B-TiO 2 nanorods arrays through the reaction between Cd 2+ and S 2- . And a significant enhancement in the photocurrent was obtained that ascribed to the formation of CdS-B-TiO 2 heterostructures, thus leading to sensitive PEC recording of the H 2 S level in buffer and cellular environments. By using Prussian blue (PB) a electrochromic material to capture the photoelectron generated from the photoelectrode, a new visual system was proposed due to the formation of Prussian white (PW), which could be used to visualize the quantum photoelectric effect. This novel PEC sensing platform not only achieved satisfied analysis results toward S 2- , but also showed excellent sensitivity, selectivity, low cost, and portable features. The strategy through the in situ generation of semiconductor nanoparticles on the surface of wide band-gap semiconductor paves the way for the improvements of PEC analytical performance. Meanwhile, the quantitative read-out electrochromic display paves a facile avenue and initiates new opportunities for creation of cheap, miniaturization sensors for other relevant analytes. [ABSTRACT FROM AUTHOR]

By incorporating the Prussian Blue (PB) electrochromic display as cathode, a solar-driven photoelectrochemical (PEC) cell was constructed through combining sandwich-structured graphite-like carbon nitride (g-C 3 N 4 )-Au-branched-titanium dioxide (B-TiO 2 ) nanorods as photoanode for self-powered hydrogen peroxide (H 2 O 2 ) sensing, which exhibits both direct photoelectrochemical and electrochromic response. The gold nanoparticles (Au NPs) sandwiched between the B-TiO 2 nanorods and the g-C 3 N 4 layer served as electron relay as well as plasmonic photosensitizer to enhance the solar-to-chemical energy conversion efficiency. Owing to the effective disproportionation of H 2 O 2 and specific recognition of mannose on cell surface, concanavalin-A conjugated porous AuPd alloy nanoparticles were introduced as the catalytically active nanolabels promoting generation of hydroxyl radicals (·OH). Based on the cleavage of DNA with the participation of ·OH radicals generated by the decomposition of H 2 O 2 under the catalysis of AuPd alloy result in the disassembly of cancer cells to achieve further signal enhancement. The multiple-signal-output sensing response not only provides a promising strategy for different analytical purposes based on novel stimuli-responsive materials, but also enhances the reliability in the analyte detection. [ABSTRACT FROM AUTHOR]

A platelike tungsten trioxide (WO 3 ) sensitized with CdS quantum dots (QDs) heterojunction is developed for solar-driven, real-time, and selective photoelectrochemical (PEC) sensing of H 2 O 2 in the living cells. The structure is synthesized by hydrothermally growing platelike WO 3 on fluorine doped tin oxide (FTO) and subsequently sensitized with CdS QDs. The as-prepared WO 3 -CdS QDs heterojunction achieve significant photocurrent enhancement, which is remarkably beneficial for light absorption and charge carrier separation. Based on the enzymatic etching of CdS QDs enables the activation of quenching the charge transfer efficiency, thus leading to sensitive PEC recording of H 2 O 2 level in buffer and cellular environments. The results indicated that the proposed method will pave the way for the development of excellent PEC sensing platform with the quantum dot sensitization. This study could also provide a new train of thought on designing of self-operating photoanode in PEC sensing, promoting the application of semiconductor nanomaterials in photoelectrochemistry. [ABSTRACT FROM AUTHOR]

In the paper, a simple and sensitive electrochemiluminescence (ECL) DNA sensor based on graphene-modified porous Au-paper working electrode (GR/Au-PWE) and calcium carbonate/carboxymethyl chitosan (CaCO3/CMC) hybrid microspheres @ luminescent silver nanoparticles (AgNPs) composites was developed. The GR/Au-PWE with excellent conductivity was successfully prepared for the immobilization of capture probe. The CaCO3/CMC hybrid microspheres were prepared by the precipitation of calcium carbonate in an aqueous solution containing CMC. The AgNPs was synthesized by thermal reduction of silver ions in glycine matrix, taking advantage of the solid-state matrix to control the nucleation and migration of reduced silver atoms. The CaCO3/CMC@AgNPs composites exhibited 3.6 times higher ECL intensity than the pure AgNPs-labeled reporter DNA. Taking advantage of dual-amplification effects, the paper-based DNA sensor could detect the target DNA quantitatively, in the range of 4.0×10−17–5.0×10−11 M, with a limit of detection as low as 8.5×10−18 M, and perform excellent selectivity. The simple, low-cost, sensitive device could be easily applied for point-of-care testing, public health and environmental monitoring in remote regions, developing or developed countries. [ABSTRACT FROM AUTHOR]

In this work, a novel sensing platform based on visible light driven biofuel cell (BFC) has been facilely designed for sensitive detection of prostate-specific antigen (PSA) with the photo-response bioanode, realizing the dual route energy conversion of light energy and chemical energy to electricity. The hierarchical branched TiO 2 nanorods (B-TiO 2 NRs) decorated with CdS quantum dots (QDs) act as the substrate to confine glucose dehydrogenase (GDH) for the visible light driven glucose oxidation at the bioanode. Three dimensional flowers like hierarchical carbon/gold nanoparticles/bilirubin oxidase (3D FCM/AuNPs/BOD) bioconjugate served as biocatalyst for O 2 reduction at the biocathode. With an increase in the concentration of PSA, the amount of BOD labels on biocathode increases, thus leading to the higher current output of the as-proposed visible light driven BFC. Based on this, this sensing platform provide great performance in sensitivity and specificity, increasing linear detection range from 0.3 pg mL −1 to 7 μg mL −1 with a detection limit of 0.1 pg mL −1 . Most importantly, our new sensing strategy provided a simple and inexpensive sensing platform for tumor markers detection, suggesting its wide potential applications for clinical diagnostics. [ABSTRACT FROM AUTHOR]

This paper introduces a paper-based closed Au-bipolar electrode (BPE) biosensing system for the rapid and sensitive electrochemiluminescence (ECL) detection of miRNA-155. This microfluidic paper-based sensing platform is formed by wax-printing technology, screen printing method and in-situ Au nanoparticles (NPs) growth to form hydrophilic cells, hydrophobic boundaries, water proof electronic bridge, driving electrode regions and bipolar electrode regions. For rapid and sensitive detection, the cathode of bipolar electrode was modified with the prepared DNA (S1)–AuPd NPs by hybridization chain reaction, in which the target could initiate multiple cycles reaction to load more AuPd NPs which catalyzed H 2 O 2 reduction. In addition, a classical ECL system tris (2,2′-bipyridine) ruthenium (II)- tripropylamine (Ru(bpy) 3 2+/TPrA) exists at the anode of the bipolar electrode. Due to the charge balance between the anode and the cathode of BPE, the ECL signal response of Ru(bpy) 3 2+/TPrA system was enhanced in the reporting cell. The intensity of ECL was quantitatively correlated with the concentration of miRNA-155 in the range of 1 pM–10 μM with the detection limit 0.67 pM. Moreover, this method paves a novel way for highly sensitive detection of miRNA-155 in clinical application. • AuNPs modified bipolar electrode system to improve electrical conductivity. • A paper-based BPE-ECL biosensing platform for the detection of miRNA-155. • AuPd NPs was loaded for signal amplification via hybridization chain reaction. [ABSTRACT FROM AUTHOR]