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A series of single-strand oligonucleotides functionalized catalytically active gold nanoparticle (AuNPs) as nonspecific receptors have been designed to build a protein sensing array. We take advantage of the correlation between the catalytic activity and the exposed surface area of AuNPs, i.e., DNA-proteins interactions mask the surface area of AuNPs, leading to poor catalytic performance of AuNPs. As the number of DNA-bound proteins increases, the surfaces of AuNPs become more masked; thus, the time of 4- nitrophenol/NaBH4 reaction for color change (yellow ? colorless) of the solution increases. Taking advantage of three nonspecific SH-labeled DNA sequences (A15, C15, and T15) as array sensing elements and the color-change time (CCT) of the solution as signal readout, colorimetric response patterns can be obtained on the array and identified via linear discriminant analysis (LDA). Eleven proteins have been completely distinguished with 100% accuracy with the naked eye at the 30 nM level. Remarkably, two similar proteins (bovine serum albumin and human serum albumin), two different proteins (bovine serum albumin and concanavalin) at the same concentration, and the mixtures of the two proteins with different molar ratios have been discriminated with 100%. The practicability of this sensor array is further validated by high accuracy (100%) identification of 11 proteins in human serum samples. [ABSTRACT FROM AUTHOR]

Air pollution is a serious problem. Refractory thiophene sulfides, which cause air pollution, bring great challenges to their rapid and accurate identification. In this work, we propose a fluorescent sensor array based on two perovskite nanocrystals (CsPbBr 3 NCs and CsPbBr 3 /SiO 2 NCs) to distinguish different thiophene sulfides. The hydrogen bonding force between the thiophenics of thiophene sulfides and the amino groups of the perovskite NCs results in the weakening of the fluorescence signals of the perovskite NCs. The diverse interactions between thiophene sulfides and two perovskite NCs provide rich information, which can be obtained on the sensor array and identified by linear discriminant analysis. Five thiophene sulfides (i.e., benzothiophene, dibenzothiophene, 2-methylbenzothiophene, 3-methylthiophene, and thiophene) were discriminated by the sensor array at concentrations of 10-50 ppm. The effectiveness of the sensor array was further verified in the discrimination of blinded samples, in which all 10 samples were correctly identified. In addition, it is gratifying that even binary mixtures of thiophene sulfides could be distinguished by the proposed sensor array.

Many enrichment techniques for phosphopeptides usually rely on the interaction of phosphate groups with metal ions or metal oxides. Based on this, we innovatively designed and fabricated an electrochemical sensor based on TiO 2 nanoparticles (NPs), which can sensitively and rapidly detect phosphopeptides in protein samples pretreated with AuNPs. When the phosphopeptide solution was pretreated with AuNPs, AuNPs can be linked to the polypeptide chain via the amino group at the tail of the polypeptide chain. When TiO 2 NPs are specifically bound to the phosphate group on the peptide, the modified AuNPs can improve the electron conduction ability of the electrode to detect the phosphopeptides. The designed electrochemical sensor had the advantages of high sensitivity, selectivity, and repeatability, and it showed a wide linear concentration range (1 pg/L to 1 mg/L) and a lower limit of detection (0.24 pg/L) for phosphopeptides. In order to improve the detection capability of the electrochemical sensor, we also synthesized TiO 2 and graphene oxide (GO) composite materials. The influence of the morphology and crystal form of TiO 2 NPs on phosphopeptide detection was studied by changing the feeding ratio and heat treatment temperature. We found that the uniformly dispersed anatase crystal TiO 2 and GO composite-modified electrode showed a lower detection limit (0.37 ag/L). This sensing strategy is expected to provide a novel solution for the direct detection of phosphate groups in polypeptides in complex environments.

Robust but ultrasensitive aptasensors with an ability to detect lower concentrations of heavy metal ions enable the detection of serious environmental and health issues. We herein develop a label-free aptasensor for ultrasensitive detection of the silver ion (Ag + ) utilizing gold nanoparticle (AuNP) intensity measurement methodology by dark-field microscopy, which is based on target Ag + and exonuclease III (Exo III)-dependent DNA cleavage recycling amplification. In the presence of target Ag + , thymine (T) bases at two termini of hairpin DNA bind with Ag + through C-Ag + -C coordination to form a DNA duplex, Exo III can recognize the blunt 3' end of the DNA duplex and digest it from the 3' end to the 5' direction. The released target Ag + then binds with another hairpin DNA via C-Ag + -C pairs. After many cycles of the digestion of the DNA duplex by Exo III, numerous remaining single-stranded DNA (ssDNA) are generated. These ssDNA are absorbed on the surface of AuNPs, enhancing the repulsion force between AuNPs, which further promotes the dispersion of AuNPs, leading to a significantly decreased intensity of yellow and red dots (aggregated AuNPs) under dark-field microscopy observation, in contrast to that of the blank solution (without target Ag + ). On this basis, the detection limits of 41 and 39 fM were achieved for Ag + in Tris-HCl buffer and river water, respectively.