Bimetallic Bi/Pt peroxidase mimic and its bioanalytical applications.

In this work, bimetallic Bi/Pt nanoparticles in bovine serum albumin biomolecular scaffold (BSA-Bi/PtNPs) were synthesized through a facile and green method. As compared with BSA-PtNPs, the BSA-Bi/PtNPs possess enhanced peroxidase-like catalytic activity. Moreover, the BSA-Bi/PtNPs are stable in harsh conditions such as high temperature, extreme pH environments, and high ionic strength, as well as in common biological matrixes. These prominent advantages enable the BSA-Bi/PtNPs to be applied to a wide range of fields. Bioassays, such as serum glucose detection, extracellular hydrogen peroxide (H2O2) monitor, and cancer cells labeling, have been realized with satisfying results. The linear range of glucose determination was from 1 to 100 µM and the limit of detection (LOD) was 0.2 µM. The H2O2 released from each MCF-7 cell after stimulation was calculated to be 2.66 × 10-16 mol/s. By utilizing folic acid as a recognition element, tumor cell could be readily distinguished by BSA-Bi/PtNPs and the LOD for MCF-7 cell detection was 90 cells.

Upregulation of microRNA-370 promotes cell apoptosis and inhibits proliferation by targeting PTEN in human gastric cancer.

Growing evidence suggests that microRNA plays an essential role in the development and metastasis of many tumors, including gastric cancer. Aberrant miR­370 expression has been indicated in tumor growth, but the mechanism of miR­370 inhibits both the proliferation and metastatic ability for gastric cancer remains unclear. Accumulating evidence reported that PTEN signaling pathway plays an important role in the cellular processes, such as apoptosis, cell growth and proliferation. The goal of this study was to identify whether miR­370 could inhibit the growth, migration, invasion, proliferation and metastasis of gastric cancer through targeting PTEN. Real-time PCR (RT-PCR) was used to quantify miR-370 expression in vitro experiments. The biological functions of miR­370 were determined via cell proliferation. Our study indicated that miR­370 targeted PTEN leading to activation of apoptosis signaling and the cell proliferation of cervical cancer cells, ameliorating gastric cancer growth and progression. In addition, the combination of miR­370 and PTEN inactivated AKT, MDM2 and mTOR while stimulated caspase-3, p53 and GSK3ß expression, promoting apoptosis and suppressing proliferation of gastric cancer cells. Therefore, our study revealed the mechanistic links between miR­370 and PTEN in the pathogenesis of gastric cancer through modulation of cell apoptosis and proliferation. Additionally, targeting miR­370 could serve as a novel strategy for future gastric cancer therapy clinically.

Fenton reaction-mediated fluorescence quenching of N-acetyl-L-cysteine-protected gold nanoclusters: analytical applications of hydrogen peroxide, glucose, and catalase detection.

Given the importance of hydrogen peroxide (H2O2) in many biological processes and its wide application in various industries, the demand for sensitive, accurate, and economical H2O2 sensors is high. In this study, we used Fenton reaction-stimulated fluorescence quenching of N-acetyl-L-cysteine-protected gold nanoclusters (NAC-AuNCs) as a reporter system for the determination of H2O2. After the experimental conditions were optimized, the sensing platform enabled the analysis of H2O2 with a limit of detection (LOD) as low as 0.027 µM. As the glucose oxidase cascade leads to the generation of H2O2 and catalase catalyzes the decomposition of H2O2, these two biocatalytic procedures can be probed by the Fenton reaction-mediated quenching of NAC-AuNCs. The LOD for glucose was found to be 0.18 µM, and the linear range was 0.39-27.22 µM. The LOD for catalase was 0.002 U mL(-1), and the linear range was 0.01-0.3 U mL(-1). Moreover, the proposed sensing methods were successfully applied for human serum glucose detection and the non-invasive determination of catalase activity in human saliva, demonstrating their great potential for practical applications.

Platinum nanoparticles/graphene-oxide hybrid with excellent peroxidase-like activity and its application for cysteine detection.

A facile approach is proposed for the growth of platinum nanoparticles on graphene oxide (PtNPs/GO). The resulting PtNPs/GO hybrid has been proved to function as peroxidase mimics that can catalyze the oxidation of peroxidase substrates in the presence of hydrogen peroxide (H2O2). Kinetic studies indicate that the PtNPs/GO nanocomposite has a considerably higher affinity for both 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 than those of other platinum-based peroxidase mimics. Furthermore, colorimetric recognition and sensing of L-cysteine with high sensitivity and selectivity is presented based on target-induced shielding against the peroxidase-like activity of PtNPs/GO. We envision that this material will be an ideal candidate for a wide range of potential applications in the fields of biomedicine and environmental chemistry.

pH-Sensitive gold nanoclusters: preparation and analytical applications for urea, urease, and urease inhibitor detection.

Herein, we reported for the first time a facile synthetic process of gold nanoclusters (AuNCs) by using N-acetyl-L-cysteine both as a reducing agent and as a protection ligand. Based on the pH stimuli-responsive properties of the as-prepared AuNCs, we constructed a pH-sensing platform for the detection of urea, urease, and urease inhibitors.