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Direct monitoring of Zn 2+ in living system is extremely important to human health. In Zn 2+ sensing, most chemical molecules with aggregation induced emission (AIE) effect were only used in vitro because of its potential biological toxicity. In this work, a biocompatible “turn-on” fluorescent probe for the determination of Zn 2+ combined AIE fluorophore tetraphenylethene (TPE) molecule with peptide has been designed and synthesized based on Schiff base reaction. The TPE-Peptide probe exhibited strong emission in the presence of Zn 2+ due to the formation of self-assembling complexes between Zn 2+ and the three histidine residues in two strands of peptide, which triggered TPE moieties in an aggregated state. The TPE-Peptide probe displays a highly selective and sensitive fluorescence intensity with a relatively wide linear range from 0 to 100 μM and a detection limit of 18.56 nM. As designed, the probe can penetrate live HeLa cells and image intracellular Zn 2+ by turn-on response with low cytotoxicity and good stability, implying that TPE-Peptide acts as a highly useful fluorescent biosensor for biological systems. Our strategy opens a new way for the investigation of other metal ions or bioactive molecules that can bind with special peptides and it may find wide applications in biological sensing. [ABSTRACT FROM AUTHOR]

This paper presents a new electrochemical DNA biosensor constructed using a substrate electrode composed of a novel nanocomposite material prepared using gold nanoparticles (Au-NPs) and multiwalled carbon nanotubes (MWCNTs) and further modified with an Au electrode (AuE), which was used as the substrate electrode. A single-stranded DNA (ssDNA) probe was immobilized on the Au-NPs/CS–MWCNTs/AuE electrode by means of facile gold–thiol affinity, which resulted in hybridization with the target ssDNA sequence. Hybridization reactions were assessed by using the reduction peak current of methylene blue (MB) as an electrochemical indicator. The advantages of the nanomaterials were found to include high surface area, favorable electronic properties, and strong electrocatalytic activity. The amount of ssDNA adsorbed on the electrode surface was increased and the electrochemical response of MB accelerated. The differential pulse voltammetric responses of MB were in line with the specific target ssDNA sequence within the concentration range 1.0×10 −15 –1.0×10 −8 M with the detection limit 3.3×10 −16 M (3 σ ). In the colony forming unit (CFU) we were able to detect 10 CFU mL −1 of Staphylococcus aureus in the tap water, achieving good discrimination ability between one- and three-base mismatched ssDNA sequences. The polymerase chain reaction (PCR) amplification products of S. aureus nuc gene sequence were also detected with satisfactory results. [ABSTRACT FROM AUTHOR]

Glucose assay is of great scientific significance in clinical diagnostics and bioprocess monitoring, and to design a new glucose receptor is necessary for the development of more sensitive, selective, and robust glucose detection techniques. Herein, a series of cyclic peptide (CP) glucose receptors were designed to mimic the binding sites of glucose binding protein (GBP), and CPs' sequence contained amino acid sites Asp, Asn, His, Asp, and Arg, which constituted the first layer interactions of GBP. The properties of these CPs used as a glucose receptor or substitute for the GBP were studied by using a quartz crystal microbalance (QCM) technique. It was found that CPs can form a self-assembled monolayer at the Au quartz electrode surface, and the monolayer's properties were characterized by using cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy. The CPs' binding affinity to saccharide (i.e., galactose, fructose, lactose, sucrose, and maltose) was investigated, and the CPs' sensitivity and selectivity toward glucose were found to be dependent upon the configuration, i.e., the amino acids sequence of the CPs. The cyclic unit with a cyclo[-CNDNHCRDNDC-] sequence gave the highest selectivity and sensitivity for glucose sensing. This work suggests that a synthetic peptide bearing a particular functional sequence could be applied for developing a new generation of glucose receptors and would find huge application in biological, life science, and clinical diagnostics fields. [ABSTRACT FROM AUTHOR]

In this study, a novel and simple cell-based electrochemical biosensor was developed to assess the individual and combined toxicity of deoxynivalenol (DON) and zearalenone (ZEN) on BEL-7402 cells. The sensor was fabricated by modification with AuNPs, p-aminothiophenol, and folic acid in succession. The BEL-7402 cells which had a good activity were adhered on the electrode through the high affinity between the folate receptor and folic acid selectivity. We used the collagen to maintain the cell adhesion and viability. Electrochemical impedance spectroscopy (EIS) was developed to evaluate the individual and combined toxicity of DON and ZEN. Our results indicate that DON and ZEN caused a marked decrease in the cell viability in a dose-dependent manner. The value of electrochemical impedance spectroscopy decreased with the concentration of DON and ZEN in range of 0.1–20, 0.1–50 μg/ml with the detection limit as 0.03, 0.05 μg/ml, respectively, the IC 50 for DON and ZEN as obtained by the proposed electrochemical method were 7.1 μg/ml and 24.6 μg/ml, respectively, and the combination of two mycotoxins appears to generate an additive response. The electrochemical cytotoxicity evaluation result was confirmed by biological assays. Compared to conventional methods, this electrochemical test is inexpensive, highly sensitive, and fast to respond, with long-term monitoring and real-time measurements. The proposed method provides a new avenue for evaluating the toxicity of mycotoxins. [ABSTRACT FROM AUTHOR]