Self-powered electrochromic sensing for visual determination of PSA in serum using PB as an indicator

Insights into the Mechanism of Bipolar Electrodeposition of Au Films and Its Application in Visual Detection of Prostate Specific Antigens

Au particles are commonly used for deposition on the surface of a bipolar electrode (BPE) in order to amplify electrochemical and electrochemiluminescence (ECL) signal because of their excellent conductivity, biocompatibility, and large surface area. In this work, a closed BPE device was fabricated and Au particles were deposited on the two poles of a BPE via bipolar deposition. Results indicated that the electrochemical stability of Au film on the anode part of the BPE and the reduction of AuCl₄^- to Au on the cathode part of the BPE depended on the conductivity of the solution. The prepared Au-Au BPE exhibited a remarkable amplification effect on the ECL signal. Then, a specific sensing interface was constructed on one pole of the BPE for the visual detection of prostate-specific antigens (PSA) based on sandwich-type immunoreactions between primary PSA antibodies (Ab₁) on the electrode surface, PSA, and SiO₂ nanoparticles labeled secondary PSA antibodies (SiO₂-Ab₂). The designed biosensor exhibited a good linear relationship for the ECL detection of PSA in the range of 1 × 10^-6 to 1 × 10^-10 g/mL with a correlation coefficient of 0.9866; the limit of detection (LOD) was 1.5 × 10^-11 g/mL. Additionally, the biosensor can realize the electrochemical imaging of PSA by regulating the electrochemical oxidation of the Au anode with the immunoreactions on the cathode part of BPE. Therefore, the small, portable and highly sensitive biosensors have great potential for on-site detection.

Dual-Modal Photoelectrochemical and Visualized Detection of Copper Ions

Copper is one of the extensively utilized heavy metals in modern industry and can be easily released into the environment due to high solubility of copper ions (Cu²⁺). Its percolation in water and accumulation along the food chain pose a serious threat to human health. Hence, it is of great significance to explore a novel, facile, and sensitive detection method for Cu²⁺. Based on the intriguing photo-to-electricity conversion process of CdS QDs, as well as desirable electrochromic property of WO₃ NFs, a dual-modal photoelectrochemical (PEC) and visualized detection platform for Cu²⁺ is fabricated. The electrochromic WO₃ NFs act as a display for the Cu²⁺ concentration, of which the color change could be observed directly by the naked eye, while the PEC signal provides accurate data for further analysis. In this work, a sensitive detection of Cu²⁺ in the range of 1 × 10^-5 to 5 × 10^-4 M is achieved, with a detection limit of 3.2 × 10^-6 M. The dual-modal analysis gives more choices for signal readouts with enhanced quantification reliability, which is adaptive for diverse application scenarios, especially for on-site investigation. This protocol offers a prototype for quick and reliable detection of the Cu²⁺ concentrations, and is promising for other environmental pollutants.

A DNA dendrimer amplified electrochemical immunosensing method for highly sensitive detection of prostate specific antigen

This work designed a DNA dendrimer for the loading of signal molecule and the construction of amplified electrochemical immunosensing method. The DNA dendrimer was self-assembled by the hybridization of one couple of complementary oligonucleotides (DNA and cDNA) that were covalently conjugated to three arms of a Y-shaped cross-linker, tris(2-maleimidoethyl)amine (TMEA) respectively. The immunosensor was prepared by coating chitosan on glassy carbon electrode to covalently immobilize the capture antibody with glutaraldehyde as a linker. After the target protein was captured on the immunosensor, cDNA-labeled secondary antibody was bound on the surface via a sandwiched immunoreaction to introduce the DNA dendrimer onto immunosensor for loading abundant methylene blue as signal molecule, which amplified greatly the amperometric signal for immunoassay. Using prostate specific antigen (PSA) as a model analyte, this proposed method showed a wide linear range from 1 pg mL^-1 to 10 ng mL^-1 along with a limit of detection down to 0.26 pg mL^-1. The designed strategy avoided complex synthesis of signal tags, and possessed excellent performance for analysis of practical samples, thus providing a new avenue for the development of signal amplification strategy and immunoassay methods.

Photoelectric effect driving PANI/PB multicolor visualized detection of CEA based on Ag2S NPs@ZnO NTs

In this work, a multicolor visual immunoassay platform was developed. The photoelectric effects of Ag₂S NPs@ZnO NTs made the color changes of PANI/PB, which enabled visual inspection of CEA. Under the visible light excitation, Ag₂S NPs@ZnO NTs generates electron-holes. Where, photoelectrons will pass electrical circuit to PB and photoinduced holes will oxidize PANI, which making the PANI/PB composite changes from emerald green-blue-purple-black colors. When CEA was incubated, the migration rate of photogenerated carriers is slowed down owing to the steric hindrance, resulting in different color changes of PANI/PB. In addition, the average green channel of PANI/PB read by photoshop has a certain correlated linear relationship with the concentration of CEA. Meanwhile, we can observe the color transformation of PANI/PB with our own eyes. By integrating advantages of photoelectrochemistry and colorimetry, the linear range of CEA detection was 0.1-20 ng/mL, and the detection limit was 0.05 ng/mL (S/N = 3). More importantly, this multicolor sensing method is very convenient, simple and low-cost. The photocarriers-modulated colorimetric strategy also provides a novel idea for visual portable platform design in clinical diagnosis.