Portable, Self-Powered, and Light-Addressable Photoelectrochemical Sensing Platforms Using pH Meter Readouts for High-Throughput Screening of Thrombin Inhibitor Drugs

As a serine protease, thrombin is a pivotal component in coagulation cascade and has been frequently screened as an informative biomarker for the diagnosis of coagulation disorder-related diseases. Herein, a “signal-on” electrochemical biosensor is described for the highly sensitive and selective detection of thrombin activity, by exploiting a thrombin-specific substrate peptide (Tb peptide) as the recognition element and reversible addition–fragmentation chain transfer (RAFT) polymerization for signal amplification. Specifically, the carboxyl-group-free Tb peptides are self-assembled onto gold electrode surface via the N-terminal cysteine residue and are used for the specific recognition of thrombin molecules. After the proteolytic cleavage of the Tb peptides, the carboxyl-group-containing RAFT agents (4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, CPAD) are tethered to the free carboxyl termini of the truncated peptide fragments via the carboxylate-zirconium-carboxylate chemistry. The subsequent RAFT polymerization leads to the grafting of a polymer chain from each proteolytically cleaved site, enabling the recruitment of a large number of electroactive ferrocene (Fc) tags to the electrode surface when ferrocenylmethyl methacrylate (FcMMA) is used as the monomer. Under optimal conditions, the detection limit of the described thrombin biosensor is as low as 2.7 μU mL–1 (∼0.062 pM), with a linear response over the range of 10–250 μU mL–1 (R 2 = 0.997). Results also indicate that the biosensor is highly selective and applicable to the detection of thrombin activity in complex serum samples and the screening of thrombin inhibitors. The described biosensor is low-cost and relatively easy in preparation and thus shows great promise for the highly sensitive and selective detection of thrombin activity.

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confidence: 99%

Amplified Electrochemical Biosensing of Thrombin Activity by RAFT Polymerization

Bao

Gan

et al. 2020

“…This work presents the concept of redox cycling as an advanced signal amplification route and proof-of-concept toward ultrasensitive photoelectrochemical (PEC) bioanalysis. Unique signal amplification has long been highly pursued in the field due to the need for fast and ultrasensitive bioassays and the trend toward miniaturized assays. − For amplification to be achieved, previous strategies mainly resorted to the use of various functional nanoprobes, − DNA-based amplification techniques, − and enzyme-assisted generation of signaling species. − Although these methods have good sensitivity, they often suffer from laborious procedures, heavy consumption of biomolecules, and thus high economic costs. Therefore, facile, selective, and reproducible signal amplification is still highly appealing toward ultrasensitive PEC bioanalysis.…”

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confidence: 99%

Photoelectrochemical-Chemical-Chemical Redox Cycling for Advanced Signal Amplification: Proof-of-Concept Toward Ultrasensitive Photoelectrochemical Bioanalysis

Wang

Mei

et al. 2018

Signal amplification is essential for ultrasensitive photoelectrochemical (PEC) bioanalysis. Exploration of the facile and efficient route for multiple signal amplification is highly appealing. Herein, we present the concept of photoelectrochemical-chemical-chemical (PECCC) redox cycling as an advanced signal amplification route and a proof-of-concept toward ultrasensitive PEC bioanalysis. The system operated upon the bridging between the enzymatic generation of signaling species ascorbic acid (AA) from a sandwich immunoassay and the PECCC redox cycling among the ferrocenecarboxylic acid as redox mediator, the AA, and the tris(2-carboxyethyl)phosphine as reducing agent at the Bi2S3/Bi2WO6 photoelectrode. Exemplified by myoglobin (Myo) as target, the proposed system achieved efficient regeneration of AA and thus signal amplification toward the ultrasensitive split-type PEC immunoassay. This work first exploited the PECCC redox cycling, and we believe it will attract more interest in the research of PEC bioassays on the basis of advanced redox cycling.

“…Photoelectrochemical (PEC) assay with handy operation, low background noise, and high sensitivity has aroused enormous concern over recent years. − In routine PEC analysis systems, electron donors including hydrogen peroxide (H 2 O 2 ), ascorbic acid, and dopamine are directly added into electrolyte solution to neutralize the photogenerated holes for achieving steady and favorable PEC signal. − Nevertheless, in this case, the electron transport process between the electron donor and the photoactive material is an intermolecular electron transport process, which would lead to the restricted photoelectric conversion efficiency. Recently, the donor–acceptor (D-A) type photoactive materials have gained great research interest, which is attributed to the fact that they can realize the intramolecular electron transport process, thereby reducing the energy loss during electron transmission and improving the photoelectric conversion efficiency. , Among diverse D–A type photoactive materials, poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2- b :4,5- b ′]dithiophene-2,6-diyl- alt -3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4- b ]thiophene-4,6-diyl} (PTB7-Th) is a particularly outstanding member because of its excellent film-forming ability and photoelectric properties. − Currently, we employed PTB7-Th as photoactive material and fullerene or polyaniline as sensitizer to construct sensitive PEC biosensors.…”

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confidence: 99%

Ultrasensitive Photoelectrochemical Assay with PTB7-Th/CdTe Quantum Dots Sensitized Structure as Signal Tag and Benzo-4-chlorohexadienone Precipitate as Efficient Quencher

Tian

Liang

et al. 2018

Herein, an ultrasensitive photoelectrochemical (PEC) assay was developed for the monitoring of microRNA-141 (miRNA-141) based on poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl}/CdTe quantum dots ( PTB7-Th/CdTe QDs) sensitized structure as signal tag and the benzo-4-chlorohexadienone (4-CD) precipitate as efficient quencher. PTB7-Th and CdTe QDs were successively modified on the electrode surface to form a novel sensitized structure with eminent photovoltaic performances and surpassing film-forming ability. The PTB7-Th/CdTe QDs sensitized structure served as signal tag for achieving a strong initial PEC signal. Besides, a tiny amount of target (miRNA-141) could be transformed into numerous DNA products via enzyme-assisted target cycling procedure, which further triggered the formation of a DNA supersandwich structure on the electrode surface for loading abundant manganese porphyrin (MnPP). Thereafter, MnPP as mimetic enzyme could catalyze 4-chloro-1-naphthol (4-CN) to generate 4-CD precipitate on the sensing interface in the presence of H2O2, which could efficiently block electron transfer, leading to a significantly quenched PEC signal for determination of miRNA-141. The designed PEC biosensor performed a wide detection range from 0.1 fM to 1 nM with a low detection limit of 33 aM for miRNA-141, which paved a new avenue for highly accurate and ultrasensitive monitoring of multifarious analytes in bioanalysis and clinical diagnosis.