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Gastric cancer (GC) is the fourth most commonly diagnosed cancer and the third leading cause of cancer-related deaths. Most GC deaths can be prevented by early diagnosis. However, biomarkers with high sensitivity and specificity are rare. Comprehensive serum phosphopeptides analysis may lead to the discovery of novel biomarkers for GC. In this work, we report a mass spectrometric strategy for the evaluation of serum phosphopeptides separated and enriched by ZrAs-Fe3O4@SiO2 nanoparticles. Four endogenous phosphopeptides in sera generated by degradation of fibrinogen were synthesized with light- and heavy-glycine residues, respectively, as external/internal standards, and used to gain multi-point standard calibration curves for absolute quantification of phosphopeptides by LC-ESI-MS following ZrAs-Fe3O4@SiO2 enrichment. The ESI-MS signal ratios of the four pairs of light-/heavy-phosphopeptide standards captured by ZrAs-Fe3O4@SiO2 from aqueous solutions are linearly correlated with the molar ratios of the “light” to “heavy” phosphopeptides over the range of 0.05–5 μM with an r2 of up to 0.998 and a slope of close to 1. The recovery of the four phosphopeptides spiked at low, medium and high levels in human sera were 94.7–107.5% with RSDs in the range of 0.6–8.2%. The validated method was utilized to measure the phosphopeptide levels of serum samples from 30 healthy persons and 60 GC patients. Receiver operating characteristic (ROC) analysis shows that one phosphopeptide (F3: DpSGEGDFLAEGGGVR) yields high sensitivity and specificity of 90.0% and 96.7%, respectively, in the validation set for discriminating GC patients from healthy controls. Overall, 53 of 60 GC cases and 29 of 30 controls were correctly classified, including eight of nine GC patients at stage I. These results suggest that F3 in sera may be a potential biomarker for GC diagnosis, particularly for early stage cases.

In this work, the fluorescent β-cyclodextrin-capped ZnO quantum dots (β-CD@ZnO QDs) with a good water-solubility have been synthesized via a facile method. And the synthesized β-CD@ZnO QDs with a diameter ∼3.64 nm and a yellow fluorescence have been characterized by high resolution transmission electron microscope, UV-visible absorption, photoluminescence, and Fourier transform infrared spectroscopy. The β-CD@ZnO QDs were used as a fluorescent sensor for the detection of p-nitrophenol. A linear relationship to the concentration of the p-nitrophenol over the range of 1.0–40 μM with the detection limit of 0.34 μM was obtained. The sensing property of the β-CD-capped ZnO QDs has been successfully examined in real water samples. And the quenching mechanism was proposed, which showed that the quenching effect may be caused by the inclusion complexation between β-CD and p-nitrophenol and electron transfer.

The inhibition effect of 4,6-diamino-2-mercaptopyrimidine (DAMP) as a copper corrosion inhibitor in 3.5 wt% NaCl solution was investigated by weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization. The inhibition efficiency increased with increasing DAMP concentration in the range of 1.0 to 2.0 mM DAMP and decreased with increasing temperature. The obtained results showed that DAMP inhibited both the anodic and cathodic currents and the maximum inhibition efficiency reached 93.2% at 2.0 mM DAMP. The inhibition performance of DAMP was confirmed by SEM and EDS. Quantum chemical calculations revealed that the DAMP molecule was adsorbed on the copper surface in a paralleled way through S and N atoms and the pyrimidine ring. Adsorption of DAMP was found to obey the Langmuir adsorption isotherm.

This paper reports a dramatic cyclic regeneration of polyethyleneimine-templated silver nanoclusters (PEI-AgNCs) based on the pH-induced conformational changes of polyethyleneimine (PEI) in aqueous solution. The PEI-AgNCs have been synthesized and found to be highly sensitive to the pH of the solution in air. The studies show that small AgNCs would gather to form larger silver nanoparticles (AgNPs) by adjusting the pH to 1.5 with a nitric acid solution. The AgNPs in solution was then transformed gradually to Ag(I) ions with stirring in air. Subsequently, the above Ag(I) ions were reduced again to AgNCs by changing the pH to about 9 with a NaOH solution and adding a certain amount of formaldehyde as a reductant to solution. The fluorescence and UV-visible absorption spectra recorded this process in detail. The transmission electron microscopy images, X-ray powder diffraction patterns, and Fourier transform infrared spectra further demonstrated that the cyclic transformation existed among AgNCs, AgNPs, and Ag(I) ions. The amino-rich PEI plays a crucial role in the regeneration of PEI-AgNCs. A large number of amino groups on PEI could be reversibly protonated by adjusting the pH of solution, leading to a change of the interaction between Ag and PEI, which has laid foundation for this work.

Based on the nicking endonuclease (NEase)-assisted target recycling and magnetic nanoparticle (MNPs) separation process via the streptavidin–biotin system, we developed a new, signal amplified and ultrasensitive fluorescent biosensor for the detection of mutant human p53 gene. The target mutant DNA hybridizes with the loop portion of a hairpin probe (HP) modified with biotin and a fluorescein isothiocyanate dye (FITC) at its 5′ and 3′ ends separately and forms a nicking site for NEase, which cleaves the HP and releases the target DNA. The released target DNA again hybridizes with the intact HP and initiates the DNA recycling process with the assistance of NEase, leading to the cleavage of a large number of HPs and detachment of the biotin labeled part with the FITC tagged signal portion. Only these cleaved fragments corresponding to target DNAs could remain in solution and function as a signaling flare, while the biotin labeled sequences including intact hairpin probes could be trapped and removed by the streptavidin coated MNPs. The developed method exhibits a detection limit as low as 198 fM and high discrimination efficiency toward a single-base mismatched sequence. Therefore, the novel NEase-amplified magnetic nanoparticle assay has great potential for sensitive and accurate detection of trace amounts of DNA in clinical diagnosis and biomedical research.

4-Octylphenol (OP) was used to form self-assembled films on copper to inhibit its corrosion in 0.5 M HCl solution. The corrosion protection ability of the OP films was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy studies. It was found that the highest inhibition efficiency was obtained when copper was self-assembled in a 1.0 mM OP solution for 24 h. The films on copper were characterized by scanning electron microscopy, contact angle tests, and Fourier transform infrared spectroscopy. Molecular simulations provided the adsorption model of OP molecules on the Cu (111) surface.

Hemin-functionalized MoS2 nanosheets (hemin/MoS2-NSs) are first obtained via van der Waals interactions between few-layered MoS2 nanosheets (MoS2-NSs) and hemin molecules. It is demonstrated that a portion of MoS2-NSs undergoes a phase transition from semiconducting to metallic phase under the influence of hemin, which shows the coexistence of semiconducting and metallic phases in the crystal structure of hemin/MoS2-NSs. MoS2-NSs prepared from sonication-induced exfoliation of bulk MoS2 crystals in aqueous surfactant solution exhibit intrinsic peroxidase-like activity for the oxidation of 3,3,5,5-tetramethylbenzidine in the presence of H2O2, which is further improved by the functionalization of hemin. Significantly, MoS2-NSs are presented as a new support of hemin, and when compared to MoS2-NSs, hemin/MoS2-NSs exhibit better dispersity in aqueous solution, which is used in the development of H2O2 sensor based on the enhanced peroxidase-like activity.

This paper reports a simple method to immediately functionalize ssDNA onto gold electrodes using a low pH-induced and high salt concentration solution route. Electrochemical impedance spectroscopy, cyclic voltammetry, and chronocoulometry were used to characterize the ssDNA self-assembled monolayer (SAM). The effects of pH, ionic strength, and ssDNA sequences for DNA adsorption were investigated. It was found that thiolated ssDNA can be attached to gold electrodes using a low pH-induced route in a high salt concentration solution. A synergistic effect between pH and the salt has been suggested by studying the fundamental kinetics. The surface coverage of 3.054 × 1013 molecules/cm2 in pH 3.4 buffer was higher than that of 4.574 × 1012 molecules/cm2 in pH 7.4 buffer. The ssDNA on the gold surface was functional and was able to recognize complementary DNA strands.

The mechanism of the pH-induced aggregation reaction between melamine (Mel) and phosphate (Ps) has been studied using a combination of resonance Rayleigh scattering (RRS), FTIR, UV-visible spectra, and single-crystal X-ray and powder X-ray diffraction for the first time. The results confirm that the aggregation reaction between Mel and Ps is highly pH-dependent. Changes in pH dramatically influence the molar ratio of Mel to melaminium (Hmel+) and subsequently affect the synergistic nature of hydrogen bonding, electrostatic and π–π stacking interactions, resulting in the reversibility of the aggregation and dissolution process. The composition of the Mel–Ps aggregates has been characterized as 2[Hmel+]·[HPO42−]·3H2O. Mechanism analysis demonstrated that there exist two different methods for the transformation of Mel into Hmel+ by considering the aggregation reaction process and conditions.