Ultrasensitive Photoelectrochemical Biosensing of Cell Surface N-Glycan Expression Based on the Enhancement of Nanogold-Assembled Mesoporous Silica Amplified by Graphene Quantum Dots and Hybridization Chain Reaction

Folic acid-functionalized graphene quantum dots with tunable fluorescence emission for cancer cell imaging and optical detection of Hg2+

Functional groups may alter the optical and electrical characteristics of graphene quantum dots and lead to unusual properties and related applications.

A novel electrochemical cytosensor for selective and highly sensitive detection of cancer cells using binding-induced dual catalytic hairpin assembly

Rare cancer cells in body fluid could be useful biomarkers for noninvasive diagnosis of cancer. However, detection of these rare cells is currently challenging. In this work, a binding-induced dual catalytic hairpin assembly (DCHA) electrochemical cytosensor was developed for highly selective and sensitive detection of cancer cells. The fuel probe, released by hybridization between the capture probe and catalytic hairpin assembly (CHA) products of target cell-responsive reaction, initiated dual CHA recycling, leading to multiple CHA products. Furthermore, the hybridization between fuel probe and capture probe decreased non-specific CHA products, improving the signal-to-noise ratio and detection sensitivity. Under the optimal conditions, the developed cytosensor was able to detect cells down to 30 cells mL^-1 (S/N = 3) with a linear range from 50 to 100,000 cells mL^-1 and was capable of distinguishing target cells from normal cells in clinical blood samples.

Cerium Dioxide-Mediated Signal "On-Off" by Resonance Energy Transfer on a Lab-On-Paper Device for Ultrasensitive Detection of Lead Ions

In this report, a 3D microfluidic lab-on-paper device for ultrasensitive detection of lead cation was designed using phoenix tree fruit-shaped CeO₂ nanoparticles (PFCeO₂ NPs) as the catalyst and 50 nm silver NPs (Ag NPs) as the quencher. First, snowflake-like Ag NPs were grown on the paper working electrode through an in situ growth method and used as a matrix for DNAzymes that were specific for lead ions (Pb²⁺). After the addition of Ag NP-labeled substrate strands, the Ag NPs restrained the electrochemiluminescence (ECL) intensity of luminol greatly through the resonance energy transfer from luminol to Ag NPs. However, under the existence of Pb²⁺, the substrate strands were separated, and then PFCeO₂ NP-labeled signal strands were hybridized with the DNAzymes. The ECL signal was improved greatly under the fast catalytic reaction between PFCeO₂ NPs and H₂O₂, which converted the response from signal off to signal on state, resulting in sensitive detection of Pb²⁺. Under the optimal conditions, the ECL signal response exhibited a good linear relationship with the logarithm of lead cation in a wide linear range of 0.05-2000 nM and an ultralow detection limit of 0.016 nM. Meanwhile, a sensor featured with good specificity, acceptable stability, reproducibility, and low cost provides a promising portable, simple, and effective strategy for Pb²⁺ detection.

Photoelectrochemical sensitive detection of insulin based on CdS/polydopamine co-sensitized WO3 nanorod and signal amplification of carbon nanotubes@polydopamine

An ultrasensitive photoelectrochemical sandwich immunosensor was designed for detection of insulin based on WO₃/CdS/polydopamine (WO₃/CdS/PDA) co-sensitized and PDA@carbon nanotubes (PDA@CNT) conjugates for signal amplification. The CdS nanoparticles were first deposited on the WO₃ nanorods via sequential chemical bath deposition to form the WO₃/CdS structure to enhance photocurrent. Then equipped with PDA to form the WO₃/CdS/PDA photosensitive structure. The PDA was used not only to reduce the toxicity of CdS but also adsorb insulin primary antibodies (Ab₁). Meanwhile, insulin secondary antibodies (Ab₂) were decorated by PDA@CNT conjugates for signal amplification and further enhance photocurrent. Different photocurrent intensities were obtained by the photoelectrochemical workstation at applied bias of 0V due to the different amount of the PDA@CNT conjugates introduced by the different concentrations of insulin. A good linear relationship was obtained between the increased photocurrent and insulin concentrations range from 0.01ngmL^-1 to 50ngmL^-1. And a detection limit of 2.8pgmL^-1 was obtained. The proposed sensor was applied to the determination of the insulin in human serum sample, and satisfactory results were obtained. The sensor presented good specificity, reproducibility and stability, thus it might find application in the clinical diagnosis of insulin or other biomarkers in the near future.

Carbon nanostructures in biology and medicine

Carbon nanostructures have unique physical, chemical, and electrical properties, which have attracted great interest from scientists. Carbon dots, carbon nanotubes, graphene and other carbon nanomaterials are being successfully implemented in electrochemical sensing, biomedical and biological imaging.

Enzyme-free, signal-amplified nucleic acid circuits for biosensing and bioimaging analysis

Enzyme-free, signal-amplified nucleic acid circuits utilize programmed assembly reactions between nucleic acid substrates to transduce a chemical input into an amplified detection signal.