Photoactive conjugated microporous polymer@C60 with quencher on tailed Y-triangular DNA structure for high-performance signal-off photoelectrochemical biosensing

Photocurrent polarity switching photoelectrochemical aptasensor for oxytetracycline based on BiOBr/Ag2S/PDA//CuO: CuO-induced II-type to dual Z-scheme system

BACKGROUND

As a broad-spectrum tetracycline antibiotic, Oxytetracycline (OTC) was widely used in a variety of applications. But, the overuse of OTC had led to the detection of it in food, water and soil, which could present significance risk to human health and cause damage to ecosystem. It was of great significance to develop sensitive detection methods for OTC. Herein, an environmentally friendly photoelectrochemical (PEC) aptasensor was constructed for the sensitive detection of OTC based on CuO-induced BiOBr/Ag2S/PDA (Polydopamine) photocurrent polarity reversal.

RESULTS

BiOBr/Ag2S/PDA composites modified electrode not only produced stable initial anodic photocurrent but also provided attachment sites for the aptamer S1 of OTC by the strong adhesion of PDA. On the other hand, CuO loaded OTC aptamer S2 (Cu-S2) was got through Cu-S bonds. After the target OTC was identified on the electrode surface, CuO was introduced to the surface of ITO/BiOBr/Ag2S/PDA through the specific binding of OTC to S2. This identification process formed dual Z-type heterojunctions and resulted in a remarkable reversal of photocurrent polarity from anodic to cathodic. Under optimization conditions, the PEC aptasensor showed a wide linear range (50 fM ∼ 100 nM), low detection limit (1.9 fM), excellent selectivity, stability and reproducibility for the detection of OTC. Moreover, it was successfully used for the analysis of OTC in real samples of tap water, milk and honey, and had the potential for practical application.

SIGNIFICANCE

This work developed an environmentally friendly photocurrent-polarity-switching PEC aptasensor with excellent selectivity, reproducibility, stability, low LOD and wide linear range for OTC detection. This sensitive system, which was including BiOBr, Ag2S, PDA and CuO were low toxicity, not only reduced the risk of traditional toxic semiconductors to operators and the environment, but can also be used for the detection of real samples, broadening the wider range of applications for BiOBr, Ag2S, PDA and CuO.

Carbon-based photoelectrochemical sensors: recent developments and future prospects

Owing to the considerable potential of photoelectrochemical (PEC) sensors, they have gained significant attention in the analysis of biological, environmental, and food markers. However, the limited charge mass transfer efficiency and rapid recombination of electron hole pairs have become obstacles in the development of PEC sensors. In this case, considering the unique advantages of carbon-based materials, they can be used as photosensitizers, supporting materials and conductive substrates and coupled with semiconductors to prepare composite materials, solving the above problems. In addition, there are many types of carbon materials, which can have semiconductor properties and form heterojunctions after coupling with semiconductors, effectively promoting the separation of electron hole pairs. Herein, we aimed to provide a comprehensive analysis of reports on carbon-based PEC sensors by introducing their research and application status and discussing future development trends in this field. In particular, the types and performance improvement strategies of carbon-based electrodes and the working principles of carbon-based PEC sensors are explained. Furthermore, the applications of carbon-based photoelectric sensors in environmental monitoring, biomedicine, and food detection are highlighted. Finally, the current limitations in the research on carbon-based PEC sensors are emphasized and the need to enhance the sensitivity and selectivity through material modification, structural design, improved device performance, and other strategies are emphasized.

A porous aromatic cage-based electrochemical sensor for enantioselective recognition of DOPA

An electrochemical sensor based on porous aromatic cages was reported, which can achieve chiral sensing of DOPA enantiomers. The prepared sensor can achieve a recognition efficiency of up to 2.6 for DOPA enantiomers. The enhanced recognition efficiency could be attributed to the cooperation of intermolecular interactions, and the efficient charge transfer process.

Visible-light-driven photoelectrochemical sensor based on conjugated microporous polymer-grafted graphene for o-aminophenol detection

The pollutant o-aminophenol (o-AP) presents considerable risk to environmental safety, and its detection is therefore critical. Although various optical and electrochemical methods have been proposed for the detection of o-AP, there are a limited number of detection methods based on photoelectrochemical (PEC) sensors. In this study, a sensitive visible-light-driven PEC sensor was developed for o-AP detection in water. A conjugated microporous polymer (CMP)-coated graphene heterostructure (CMP-rGO) was synthesized and used to develop a PEC sensor. Under optimal conditions, the proposed sensor exhibited a high sensitivity of 0.03 μM with a wide linear range of 0.0034-37.6 μM. The PEC sensor also displayed acceptable repeatability and reproducibility, good long-term stability, and excellent recovery (98-102%). In addition, the binding patterns of CMP to o-AP and o-AP analog molecules were analyzed by molecular docking. Therefore, this study provides a new and feasible PEC sensor-based detection scheme for o-AP detection.

Covalent organic frame based high-performance nanocomposite for construction of ATP sensor

In this work, a novel covalent organic frame (TAPT-TFPB COF) with self-enhanced photoelectric activity was prepared for decorating on conductive single-walled carbon nanotubes (SWCNT) to synthetize a high-performance photoelectric nanocomposite (COF/SWCNT), in which the interfacial charge separation and photogenerated carrier migration rate was significantly improved to obtain desiring photoelectric conversion efficiency for generating an extremely high photocurrent. Accordingly, the synthetic COF/SWCNT was ingeniously applied in the fabrication of ultrasensitive photoelectrochemical (PEC) biosensor for realizing the trace ATP detection by integrating with an Exo III-assisted dual DNA recycling amplification strategy. The recycling amplification could efficiently convert trace target ATP into plentiful output DNA, which ingeniously triggered the hybridization chain reaction (HCR) to generate a long DNA strand with substantial quencher manganese porphyrin (MnPP) loading to depress the photocurrent of COF/SWCNT. The experimental data showed that proposed biosensor had a detection range from 10 fmol L-1 to 10 nmol L-1 with the detection limit as low as 2.75 fmol L-1 (S/N = 3). In addition, this proposed biosensor showed excellent analytical performance in terms of stability, specificity and reproducibility, providing a possibility to accomplish sensitive and accurate in vitro diagnosis.

Ascorbic Acid Induced the Improved Oxygen Vacancy Defects of Bi4O5Br2 and Its Application on Photoelectrochemical Detection of DNA Demethylase MBD2 with Improved Detection Sensitivity

Oxygen vacancy defects (OVs) are one of the main strategies for nanomaterials modification to improve the photoactivity, but current methods for fabricating OVs are usually complicated and harsh. It is important to develop simple, rapid, safe, and mild methods to fabricate OVs. By studying the effects of different weak reducing agents, the concentration of the reducing agent and the reaction time on fabrication of OVs, it is found that L-ascorbic acid (AA) gently and rapidly induces the increase of OVs in Bi4O5Br2 at room temperature. The increased OVs not only improve the adsorption of visible light, but also enhance the photocurrent response. Based on this, the preparation of OVs in Bi4O5Br2 is employed to the development of a photoelectrochemical biosensor for the detection of DNA demethylase of methyl-CpG binding domain protein 2 (MBD2). The biosensor shows a wide linear range of 0.1-400 ng mL-1 and a detection limit as low as 0.03 ng mL-1 (3σ). In addition, the effect of plasticizers on MBD2 activity is evaluated using this sensor. This work not only provides a novel method to prepare OVs in bismuth rich materials, but also explores a new novel evaluation tool for studying the ecotoxicological effects of contaminants.

Competitive photoelectrochemical aptamer sensor based on a Z-scheme Fe2O3/g-C3N4 heterojunction for sensitive detection of lead ions

Lead ion (Pb2+) is one of the heavy metal contaminants within the environment, which can seriously affect biological health. Thus, it is very important to detect lead ions, especially exceeding the standard concentration (100 ng/mL). In this work, we have developed a photoelectrochemical (PEC) aptamer sensor with Z-scheme Fe2O3/g-C3N4 heterojunction as a substrate material for sensitive detection of Pb2+. Specifically, Fe2O3/g-C3N4 is employed as a substrate with a powerful and stable photocurrent response. Au and DNA-1 connected to the substrate material via the Au-S bond and increased the electron conduction. Marking DNA-2 with ZnO effectively reduced the light absorption intensity resulting in a lower photocurrent response. Surprisingly, the Pb2+ PEC sensor showed good linearity in the detection range of 62 pg/mL to 1 μg/mL with a detection limit as low as 7.9 pg/mL (S/N = 3). The sensor showed stable recovery and low relative standard deviation in real sample detection. Additionally, the sensor exhibited excellent stability, selectivity, and reproducibility. The reproducibility of the electrodes was evaluated, and the accuracy of the individual electrode current values was calculated to range from 0.5% to 2.71% with an RSD of 1.74%. Such PEC sensor guarantees to supply a brand-new approach to the detection of Pb2+.

Small-Molecule Probe-Induced In Situ-Sensitized Photoelectrochemical Biosensor for Monitoring α-Glucosidase Activity

Semiconductor-based photoelectrochemical (PEC) biosensors have garnered significant attention in the field of disease diagnosis and treatment. However, the recognition units of these biosensors are mainly limited to bioactive macromolecules, which hinder the photoelectric response due to their insulating characteristics. In this study, we develop an in situ-sensitized strategy that utilizes a small-molecule probe at the interface of the photoelectrode to accurately detect α-glucosidase (α-Glu) activity. Silane, a prototype small-molecule probe, was surface-modified on graphitic carbon nitride to generate Si nanoparticles upon reacting with hydroquinone, the enzymatic product of α-Glu. The in situ formed heterojunction enhances the light-harvesting property and photoexcited carrier separation efficiency. As a result, the in situ-sensitized PEC biosensor demonstrates excellent accuracy, a low detection limit, and outstanding anti-interference ability, showing good applicability in evaluating α-Glu activity and its inhibitors in human serum samples. This novel in situ sensitization approach using small-molecule probes opens up new avenues for developing simple and efficient PEC biosensing platforms by replacing conventional biorecognition elements.