Nanoporous Semiconductor Electrode Captures the Quantum Dots: Toward Ultrasensitive Signal-On Liposomal Photoelectrochemical Immunoassay.

Liposomal photoelectrochemical (PEC) bioanalysis has recently emerged and exhibited great potential in sensitive biomolecular detection. Exploration of the facile and efficient route for advanced liposomal PEC bioanalysis is highly appealing. In this work, we report the split-type liposomal PEC immunoassay system consisting of sandwich immunorecognition, CdS quantum dots (QDs)-loaded liposomes (QDLL), and the release and subsequent capture of the QDs by a separated TiO2 nanotubes (NTs) electrode. The system elegantly operated upon the protein binding and lysis treatment of CdS QDLL labels within the 96-well plate, and then the CdS QDs-enabled sensitization of TiO2 NTs electrode. Exemplified by cardiac markers troponin I (cTnI) as target, the proposed system achieved efficient activation of TiO2 NTs electrode and thus the signal generation toward the split-type PEC immunoassay. This work features the first use of QDs for liposomal PEC bioanalysis and is expected to inspire more interests in the design and implementation of numerous QDs-involved liposomal PEC bioanalysis.

Three-Dimensional CdS@Carbon Fiber Networks: Innovative Synthesis and Application as a General Platform for Photoelectrochemical Bioanalysis.

This Letter reports a novel synthetic methodology for the fabrication of three-dimensional (3D) nanostructured CdS@carbon fiber (CF) networks and the validation of its feasibility for applications as a general platform for photoelectrochemical (PEC) bioanalysis. Specifically, 3D architectures are currently attracting increasing attention in various fields due to their intriguing properties, while CdS has been most widely utilized for PEC bioanalysis applications because of its narrow band gap, proper conduction band, and stable photocurrent generation. Using CdS as a representative material, this work realized the innovative synthesis of 3D CdS@CF networks via a simple solvothermal process. Exemplified by the sandwich immunoassay of fatty-acid-binding protein (FABP), the as-fabricated 3D CdS@CF networks exhibited superior properties, and the assay demonstrated good performance in terms of sensitivity and selectivity. This work features a novel fabrication of 3D CdS@CF networks that can serve as a general platform for PEC bioanalysis. The methodology reported here is expected to inspire new interest for the fabrication of other 3D nanostructured Cd-chalcogenide (S, Se, Te)@CF networks for wide applications in biomolecular detection and beyond.

Liposome-Mediated in Situ Formation of AgI/Ag/BiOI Z-Scheme Heterojunction on Foamed Nickel Electrode: A Proof-of-Concept Study for Cathodic Liposomal Photoelectrochemical Bioanalysis.

This work reports the liposome-mediated in situ formation of the AgI/Ag/BiOI Z-scheme heterojunction on foamed nickel electrode for signal-on cathodic photoelectrochemical (PEC) bioanalysis. Specifically, in a proof-of-concept study, Ag nanoparticle-encapsulated liposomes were initially confined via the sandwich immunobinding and then processed to release numerous Ag+ ions, which were then directed to react with the BiOI/Ni electrode, resulting in the in situ generation of a AgI/Ag/BiOI Z-scheme heterojunction on the electrode. The enhanced cathodic signal could be correlated to the target concentration, which thus underlays a novel signal-on cathodic liposomal PEC bioanalysis strategy. Different from previous anodic liposomal PEC bioanalysis, this work features the first cathodic liposomal PEC bioanalysis on the basis of the in situ formation of a Z-scheme heterojunction. More generally, integrated with various biorecognition events, this protocol could serve as a common basis for addressing numerous targets of interest.

Enhanced split-type photoelectrochemical aptasensor incorporating a robust antifouling coating derived from four-armed polyethylene glycol.

Antifouling biosensors capable of preventing protein nonspecific adhesion in real human bodily fluids are highly sought-after for precise disease diagnosis and treatment. In this context, an enhanced split-type photoelectrochemical (PEC) aptasensor was developed incorporating a four-armed polyethylene glycol (4A-PEG) to construct a robust antifouling coating, enabling accurate and sensitive bioanalysis. The split-type PEC system involved the photoelectrode and the biocathode, effectively separating signal converter with biorecogniton events. Specifically, the TiO2 electrode underwent sequential modification with ZnIn2S4 (ZIS) and polydopamine (PDA) to form the PDA/ZIS/TiO2 photoelectrode. The cathode substrate was synthesized as a hybrid of N-doped graphene loaded with Pt nanoparticles (NG-Pt), and subsequently modified with 4A-PEG to establish a robust antifouling coating. Following the anchoring of probe DNA (pDNA) on the 4A-PEG-grafted antifouling coating, the biocathode for model target of cancer antigen 125 (CA125) was obtained. Leveraging pronounced photocurrent output of the photoelectrode and commendable antifouling characteristics of the biocathode, the split-type PEC aptasensor showcased exceptional detection performances with high sensitivity, good selectivity, antifouling ability, and potential feasibility.

Design of U-shaped peptides with long-lasting antifouling efficacy: Toward a feasible electrochemical aptasensor for robust detection in human serum.

BACKGROUND: Developing biosensors with antifouling properties is essential for accurately detecting low-concentration biomarkers in complex biological matrix, which is imperative for effective disease diagnosis and treatment. Herein, an antifouling electrochemical aptasensor qualifying for probing targets in human serum was explored based on newly-devised peptides that could form inverted U-shaped structures with long-term stability. RESULTS: The inverted U-shaped peptides (U-Pep) with two terminals of thiol groups grafted onto the Au-modified electrode showcase superior antifouling properties in terms of high stability against enzymatic hydrolysis and long acting against biofouling in actual biofluids. The construction of the outlined antifouling electrochemical aptasensor just involved the fabrication of Au-deposited poly(3,4 ethylenedioxythiophene) (Au/PEDOT) modified electrode, followed by one-step co-incubation in the peptides and the aptamer probes with the Au/PEDOT electrode. Taking a typical biomarker of alpha-fetoprotein (AFP) for detection, this elegant antifouling aptasenor demonstrated a nice response for probing the target AFP with a low detection limit of 0.27 pg/mL and a wide linear scope of 1.0 pg/mL to 1.0 µg/mL, and furthermore qualified for assaying of AFP in human serum samples with satisfactory accuracy and feasibility. SIGNIFICANCE: This engineering strategy of U-Pep with long-lasting antifouling efficacy opens a new horizon for high-performance antifouling biosensors suitable for detection in complex bifluids, and it could spark more inspiration for a follow-up exploration of other featured antifouling biomaterials.

An anti-fouling wearable molecular imprinting sensor based on semi-interpenetrating network hydrogel for the detection of tryptophan in sweat.

The challenge of heavy biofouling in complex sweat environments limits the potential of electrochemical sweat sensors for noninvasive physiological assessment. In this study, a novel semi-interpenetrating hydrogel of PSBMA/PEDOT:PSS was engineered by interlacing PEDOT:PSS conductive polymer with zwitterionic PSBMA network. This versatile hydrogel served as the foundation for developing an anti-fouling wearable molecular imprinting sensor capable of sensitive and robust detection of tryptophan (Trp) in complex sweat. The incorporation of PEDOT:PSS conductive polymer into the semi-interpenetrating hydrogel introduced diverse physical crosslinks, including hydrogen bonding, electrostatic interactions, and chain entanglement. This incorporation considerably boosted the hydrogel's mechanical robustness and imparted commendable self-healing property. At the same time, the synergistic coupling between the well-balanced charge of the zwitterionic network and the high conductivity of the PEDOT:PSS polymer facilitated efficient charge transfer. The formation of the desired molecular imprinting membrane of semi-interpenetrating hydrogel was triggered by self-polymerization of dopamine (DA) in the presence of Trp. The designed biosensor demonstrated good sensitivity, selectivity and stability in detecting the target Trp. Notably, it also exhibited exceptional anti-fouling abilities, allowing for accurate Trp detection in complex real sweat samples, yielding results comparable to commercial enzyme-linked immunoassay (ELISA).

Size-Dependent Modulation of Polydopamine Nanospheres on Smart Nanoprobes for Detection of Pathogenic Bacteria at Single-Cell Level and Imaging-Guided Photothermal Bactericidal Activity.

Pathogenic bacterial fouling in agriculture and food-associated products poses mounting food safety concerns today. Efficient integration of precise tracking and on-demand bacterial killing to achieve the source control of pathogenic bacteria at the single-cell level is one of the most valuable antifouling methods for safeguarding food safety but remains unexplored. Here, we report an all-in-one design strategy as a proof of concept to establish a stimuli-responsive nanoprobe PDANSs-FAM-Apt for the detection of Staphylococcus aureus (S. aureus) at the single-cell level, which could be capable of guiding the on-demand photothermal killing of bacteria upon near-infrared (NIR) light irradiation. By examining the size-dependent modulation of the fluorescence resonance energy transfer efficiency to polydopamine nanospheres (PDANSs), PDANSs-FAM-Apt was finally assembled by 6-carboxyfluorescein-terminated S. aureus, binding the aptamer (FAM-Apt) and PDANSs at ∼258 nm through π-π stacking interactions. As a result, PDANSs-FAM-Apt exhibits a remarkable fluorescence enhancement (∼261-fold) to S. aureus with a satisfactory detection limit of 1.0 cfu/mL, allowing for assay at the single-cell level and thus ultralow background fluorescence imaging of S. aureus as well as its biofilms. Moreover, PDANSs-FAM-Apt shows a high photothermal bactericidal property upon NIR light irradiation, endowing it with the strong capacity to efficiently produce heat for destroying S. aureus and its biofilms with the guidance of imaging results. This work emphasizes the versatility of using the combination of stimuli-responsive fluorescence imaging dependent on the PDANS size modulation and NIR light-activated photothermal antibacterial activity to design stimuli-responsive nanoprobes with an improved precision for pathogenic bacteria monitoring and source controlling, which opens a promising antifouling avenue to eliminate bacteria and disrupt bacterial biofilms in agriculture and food-related industries.

Three-dimensional CdS nanosheet-enwrapped carbon fiber framework: Towards split-type CuO-mediated photoelectrochemical immunoassay.

This work reports a customized methodology for the fabrication of 3D CdS nanosheet (NS)-enwrapped carbon fiber framework (CFF) and its utilization for sensitive split-type CuO-mediated PEC immunoassay. Specifically, the 3D CdS NS-CFF was fabricated via a solvothermal process, while the sandwich immunocomplexing was allowed in a 96 well plate with CuO nanoparticles (NPs) as the signaling labels. The subsequent release of the Cu2+ ions was directed to interact with the CdS NS, generating trapping sites and thus inhibiting its photocurrent generation. In such a protocol, the 3D CdS NS-CFF photoelectrode could not only guarantee its sufficient contact with the Cu2+-containing solution but also supply plenty CdS surface for the Cu2+ ions. Because of the target-dependent release of the Cu2+ ions and its proper coupling with the 3D CdS NS-CFF photoelectrode, a sensitive split-type PEC immunoassay was achieved for the detection of brain natriuretic peptide (BNP). This proposed system exhibited good stability and selectivity, and its applicability for real sample analysis was also demonstrated via comparison with the commercial BNP enzyme-linked immunosorbent assay (ELISA) kit. We expect this work could stimulate more interest in the design and utilization of 3D photoelectrodes for novel PEC bioanalysis.

Enhanced organic-inorganic heterojunction of polypyrrole@Bi2WO6: Fabrication and application for sensitive photoelectrochemical immunoassay of creatine kinase-MB.

In this report, enhanced organic-inorganic heterojunction of polypyrrole@Bi2WO6 was fabricated and applied for sensitive photoelectrochemical (PEC) immunoassay of creatine kinase-MB (CK-MB). Specifically, heterostructured polypyrrole@Bi2WO6 photoelectrode was prepared and sandwich immunorecognition were integrated for the CK-MB immunoassay. In the detection, with the aid of alkaline phosphate (ALP)-induced biocatalytic precipitation (BCP), the precipitation-dependent suppression of the photocurrent can be recorded due to the impediment of the interfacial mass and electron transfer. On the basis of target-controlled BCP formation, a novel PEC immunoassay could be developed for the sensitive and specific CK-MB detection. This work manifested the great potential of polypyrrole@Bi2WO6 heterojunction as a novel platform for PEC bioanalysis development and also a PEC method for CK-MB detection. This work is expected to stimulate more interest in the design and implementation of numerous other organic-inorganic heterojunction for advanced PEC bioanalysis development.

Tyrosinase-encapsulated liposomes: Toward enzyme-induced in situ sensitization of semiconductor for sensitive photoelectrochemical immunoassay.

Liposomal photoelectrochemical (PEC) bioanalysis holds enormous potential for future sensitive PEC bioanalysis. With tyrosinase (Tyr) and TiO2 as representative enzyme and electrode, respectively, this communication reports the elegant use of Tyr-loaded liposomes (TLL) toward in situ sensitization of the electrode and thereby the realization of ultrasensitive PEC immunoassay. Specifically, Tyr-encapsulated and detection antibody-functionalized liposomes were first prepared and used as the signal probe. The subsequent sandwich immunobinding could confine the functional liposomes, which were then lysed with surfactant to release the encapsulated Tyr. The free Tyr could then initiate the transformation of tyrosine to dopa, the latter could bind with the undercoordinated Ti sites, forming the stable dopa-Ti charge transfer complex and thus generating enhanced anodic photocurrent under visible light for signaling. Since different semiconductors and enzymes may be adapted into this format, this work is expected to stimulate more interest in the enzyme-induced activation of semiconductors for advanced liposomal PEC bioanalysis.

Separating photoanode from recognition events: toward a general strategy for a self-powered photoelectrochemical immunoassay with both high sensitivity and anti-interference capabilities.

A general, efficient strategy for a self-powered PEC immunoassay with an evident photocurrent response was proposed by separating the photoanode from recognition events. The immunoassay demonstrates the exciting features of both high sensitivity and anti-interference capabilities.

Enhanced photoelectrochemical aptasensing platform based on exciton energy transfer between CdSeTe alloyed quantum dots and SiO2@Au nanocomposites.

High-efficient exciton energy transfer between CdSeTe alloyed quantum dots and SiO2@Au nanocomposites was applied to develop an enhanced photoelectrochemical aptasensing platform with ultrahigh sensitivity, good selectivity, reproducibility and stability.