Photoelectrochemical (PEC) sensor and biosensor are regarded as a hot spot of detection methods which present great potential for future analytical field for various targets. The impetus for the development of Bi2S3-based PEC sensor and biosensor was located the adjustable energy band with various morphologies. In this review, we have discussed the Bi2S3 semiconductor applied in PEC platform for sensing various target molecules. Due to the high recombination efficiency of the photogenerated electron-hole pairs, various strategies have been employed to improve the migration rate of the photogenerated electron, increase the detachment of photogenerated electron-hole pairs and promote the PEC response of Bi2S3, such as element-doping Bi2S3, conductive material modified Bi2S3, Bi2S3-based binary heterojunction, and Bi2S3-based multiple heterojunction, which have been discussed in this work. The challenges against Bi2S3-based PEC and its future prospects will also be explored. 

Recent advances and application of Bi2S3-based composites in photoelectrochemical sensors and biosensors

Molecular assembly offers a promising strategy to construct active systems by using biomolecules as building blocks. Such assembled systems simulate or regulate important biological activities and show great promise in wide bioapplications. In this short review, we focus on the recent progress in ATP-involved active self-assembled systems. ATP-generated active systems are constructed with hierarchical structures via molecular assembly to produce ATP, by using various external influences to generate proton gradient. Further, we highlight present active supermolecular systems driven by ATP as chemical fuel. Finally, we discuss the key challenges and perspectives in the future research. We focus on the recent progress in ATP-generated active systems are constructed with hierarchical structures through ATP synthase-based molecular assembly to produce ATP, by using various external influences to establish proton gradient. We highlight present active supermolecular systems driven by ATP as chemical fuel. 

Advance in ATP-involved Active Self-assembled Systems

Photoelectrochemical (PEC) immunoassays with ultrasensitive detection abilities are highly desirable for in vitro PEC diagnosis and biological detection. In this paper, dual Z-scheme PEC immunoassays with hierarchical nanostructures (TiO2@NH2-MIL-125@CdS) are synthesized through epitaxial growth of MOF-on-MOF and further in situ derivatization. The dual Z-scheme configuration not only extends the light absorption range but also increases the redox ability due to the interface structure nanoengineering, which synergistically suppresses bulk carrier recombination and promotes the charge transfer efficiency at the electron level. Furthermore, a smart MOF-derived labeling probe (CuO@ZnO nanocube) is designed to develop a split-type PEC biosensor by using prostate-specific antigen (PSA) as a target biomarker. In the presence of PSA, the Ab2-labeled CuO@ZnO would specifically bond to the dual Z-scheme electrode. Then, the MOF-derived CuO@ZnO is dissolved by hydrochloric acid to release Cu2+, which could replace Cd2+ via an ion-exchange reaction, thus leading to the decrease of the photocurrent due to the destruction of the dual Z-scheme configuration. In typical applications, the split-type PEC immunoassay exhibits an excellent detection performance for PSA with a LOD as low as 0.025 pg·mL-1.

Ion-Exchange Reaction-Mediated Hierarchical Dual Z-Scheme Heterojunction for Split-Type Photoelectrochemical Immunoassays.

Herein, we reported a novel photoelectrochemical immunoassay method based on a target-triggered on/off signal of the ultra-structured Bi2O2S (BOS) photoanode system for the sensitive testing of carcinoembryonic antigens (CEAs) in serum samples. Well-defined three-dimensional sheet-like self-assembled flower-like Bi2O2S superstructures were obtained using a time-controlled hydrothermal method. Such well-shaped multifaceted surfaces were considered to be good laser cavity mirror surfaces for multifaceted reflection and refraction of excitation light in the material. An elegant enzyme biocatalytic strategy was introduced into the constructed detection model to sensitively detect CEAs. The substrate 4-chloro-1-naphthol (4-CN) was oxidized to 4-chloro-hexadienone (4-CD) under the formation of target-triggered immune complexes against mAb1 and peroxidase-modified mAb2. Subsequently, 4-CD produced by the biocatalytic precipitation reaction was transferred to the photoanodes of Bi2O2S nanoflowers (BOS NFs) to burst their photoelectric signals, thus achieving the quantification of CEAs. Through optimization of the conditions of the immunization protocol, a good negative photocurrent response to the target CEA was found in the wide range of 0.02-50 ng mL-1 with a detection limit of 11.2 pg mL-1. Impressively, the reported biocatalytic PEC sensing strategy on superstructures is comparable, or superior, to the gold standard ELISA kit in terms of sensitivity and the target response range. This study presents a target-mediated PEC immunoassay for biocatalytic precipitation based on a self-assembled superstructure of Bi2O2S, providing a fresh scheme for the analysis of disease-related markers.

Ultrasensitive photoelectrochemical biosensing platform based target-triggered biocatalytic precipitation reactions on a flower-like Bi2O2S super-structured photoanode.

Electron transfer in protein modifications: from detection to imaging

Photoelectrochemical biosensing platforms for tumor marker detection

We construct a peptide-conjugated metal cluster as an enzyme-like catalytic bioprobe to enhance quantitative analysis of a membrane protein biomarker and detect epithelial-to-mesenchymal transition of tumor cells. This bioprobe with atomically precise formula, termed clusterzyme, possesses selective recognition and intrinsic enzyme-like activity. These favorable features facilitate sensitive quantitative analysis of the membrane protein in situ through on-cell catalytic signal amplification. This clusterzyme-based analytical method exhibits excellent compatibility with a traditional enzyme-linked immunosorbent assay and improved detection sensitivity with accuracy and robustness. Further, the expression level of the membrane protein reflects the ability of migration and invasion of model tumor cells, revealing epithelial-to-mesenchymal transition process. This work offers a facile and sensitive approach to monitor tumor cell type evolution at the molecular level, demonstrating a potential application of early cancer diagnosis and therapy assessment.

On-Cell Catalytic Detection of Epithelial-to-Mesenchymal Transition by a Clusterzyme Bioprobe.

Identifying effective reversal agents overcoming multidrug resistance with causal mechanisms from an efflux pump protein is of vital importance for enhanced tumor chemotherapy in clinic. To achieve this end, we construct a metal cluster-based probe, named clusterbody, to develop flow sorting-assisted single-cell mass spectrometry analysis. This clusterbody synthesized by biomimetic mineralization possesses an antibody-like property to selectively recognize an efflux pump protein. The intrinsic red fluorescence emission of the clusterbody facilitates fluorescence-activated high-throughput cell sorting of subpopulations with different multidrug resistance levels. Furthermore, based on the accurate formula of the clusterbody, the corresponding protein abundance at the single-cell level is determined through detecting gold content via precise signal amplification by laser ablation inductively coupled plasma mass spectrometry. Therefore, the effect of reversal agent treatment overcoming multidrug resistance is evaluated in a quantitative manner. This work opens a new avenue to identify reversal agents, shedding light on developing combined or synergetic tumor therapy.

Han Li

Papers

Photoelectrochemical biosensing platforms for tumor marker detection

On-Cell Catalytic Detection of Epithelial-to-Mesenchymal Transition by a Clusterzyme Bioprobe.

Clusterbody Enables Flow Sorting-Assisted Single-Cell Mass Spectrometry Analysis for Identifying Reversal Agent of Chemoresistance.