A renewable screen-printed electrode based on magnetic NiCo@N-doped carbon nanotubes derived from Co-MOF for ractopamine detection.

A renewable electrochemical screen-printed electrode (SPE) is proposed based on magnetic bamboo-like nitrogen-carbon (N-C) nanotubes loaded with nickel-cobalt alloy (NiCo) nanoparticles (NiCo@N-CNTs) for the determination of ractopamine (RAC). During the preparation of NiCo@N-CNTs, Co-MOF-67 (ZIF-67) was firstly synthesized, and then blended with dicyandiamide and nickel acetate, followed by a one-step pyrolysis procedure to prepare NiCo@N-doped carbon nanotubes. The surface morphology, structure, and chemical composition of NiCo@N-CNTs were characterized by SEM, TEM, XRD, XPS, and EDS. The electrocatalytic and electrochemical behavior of NiCo@N-CNTs were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that NiCo@N-CNTs possessed remarkable conductivity and electrocatalysis to the oxidation of ractopamine (RAC). By using screen-printed electrode (SPE), NiCo@N-CNTs, and a designed base support, a magnetic RAC sensor (NiCo@N-CNTs/SPE) was successfully constructed. It presented a detection linear range of 0.05-80 µM with a detection limit of 12 nM (S/N = 3). It also exhibited good sensitivity, reproducibility, and practicability in spiked real pork samples. Since the adhesion of NiCo/N-CNTs on SPE was controlled by magnet, the NiCo@N-CNTs was easily detached from the SPE surface by magnetism and thus displayed excellent renewability. This work broadened insights into portable devices for on-site and real-time analysis.

A dual-mode strategy based on ß-galactosidase and target-induced DNA polymerase protection for transcription factor detection using colorimetry and a glucose meter.

In this work, we report a novel dual-mode method for the highly specific and sensitive detection of transcription factors (TFs) via the integration of Klenow polymerase protection induced by target-specific recognition, cascade-signal amplification using the hybridization chain reaction (HCR) and CRISPR/Cas12a system, and dual-signal transduction mediated by ß-galactosidase (ß-gal) and two substrates. A dual-mode signal-sensing interface was constructed by immobilizing the oligo DNA probe (P1) tethered ß-gal in a 96-well plate. A hairpin H1 with the ability to initiate HCRs was designed to contain the TF binding site. The binding between the TF and H1 protected the H1 from being extended by the Klenow fragment. After thermal denaturation, the reserved H1 launched the HCR and the HCR products activated CRISPR/Cas12a to cleave P1 and reduce the ß-gal on the sensing interface, and thus the contents of the TFs and the corresponding signals mediated by the catalysis of ß-gal showed a correlation. This work was the first attempt at utilizing ß-gal for dual-signal transduction. It is a pioneering study to utilize the HCR-CRISPR/Cas12a system for dual-mode TF sensors. It revealed that DNA polymerase protection through the binding of TF and DNA could be applied as a new pattern to develop TF sensors.

Enhancement and inactivation effect of CRISPR/Cas12a via extending hairpin activators for detection of transcription factors.

An enhancement effect for the activation of CRISPR/Cas12a (CRISPR = clustered regularly interspaced short palindromic repeats; Cas = CRISPR-associated) was discovered. That was, a hairpin model with dangling 5' end complementary to crRNA (CRISPR RNA) greatly improved the activity of CRISPR/Cas12a after extention of two random sequences. But, the corresponding intact hairpin without PAM (protospacer adjacent motif) or suboptimal PAM sequences was completely inactive to CRISPR/Cas12a because of the superhigh stability of intact hairpin. According to the finding, a CRISPR/Cas12a-based strategy coupled with a signal reported system was designed for transcription factors detection. By using mono-labeled ssDNA (single-stranded DNA) as reporter and two newly synthesized N-C (nitrogen-doped carbon) nanosheets as scavenger to eliminate the fluorescent background, the strategy realized the detection of NF-ĸB p50 (p50 subunit of nuclear factor kappa-B) with a linear detection range of 0.8 - 2000.0 pM and a LOD of 0.5 pM. The discovery of "enhancement and inactivation effect" not only deepened insight into CRISPR/Cas12a but also broadened the practical application of CRISPR/Cas systems for the molecular detection and disease diagnostics.

Identification of miRNA/mRNA-Negative Regulation Pairs in Nasopharyngeal Carcinoma.

BACKGROUND Nasopharyngeal carcinoma (NPC) is a common malignancy in South-East Asia. NPC is characterized by distant metastasis and poor prognosis. The pathophysiological mechanism of nasopharyngeal carcinoma is unknown. This study aimed to identify the crucial miRNAs in nasopharyngeal carcinoma and their target genes, and to discover the potential mechanism of nasopharyngeal carcinoma development. MATERIAL AND METHODS Microarray expression profiling of miRNA and mRNA from the Gene Expression Omnibus database was downloaded, and we performed a significance analysis of differential expression. An interaction network of miRNAs and target genes was constructed. The underlying function of differentially expressed genes was predicted through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. To validate the microarray analysis data, significantly different expression levels of miRNAs and target genes were validated by quantitative real-time polymerase chain reaction. RESULTS We identified 27 differentially expressed miRNAs and 982 differentially expressed mRNAs between NPC and normal control tissues. 12 miRNAs and 547 mRNAs were up-regulated and 15 miRNAs and 435 mRNAs were down-regulated in NPC samples. We found a total of 1185 negative correlation pairs between miRNA and mRNA. Differentially expressed target genes were significantly enriched in pathways in cancer, cell cycle, and cytokine-cytokine receptor interaction signaling pathways. Significantly differentially expressed miRNAs and genes, such as hsa-miR-205, hsa-miR-18b, hsa-miR-632, hsa-miR-130a, hsa-miR-34b, PIGR, SMPD3, CD22, DTX4, and CDC6, may play essential roles in the development of nasopharyngeal carcinoma. CONCLUSIONS hsa-miR-205, hsa-miR-18b, hsa-miR-632, hsa-miR-130a, and hsa-miR-34b may be related to the development of nasopharyngeal carcinoma by regulating the genes involved in pathways in cancer and cell cycle signaling pathways.

The composite of bismuth oxyiodide-bismuth/nitrogen-doped carbon for photoreduction and electrochemical/photoelectrochemical dual-model sensing of Cr(VI).

A porous bismuth oxyiodide-metal bismuth/nitrogen-doped carbon (BiOI-Bi/N-C) composite composed of BiOI nanosheets, N-C sheets, and metallic Bi nanoparticles was prepared. BiOI-Bi/N-C exhibited remarkable cathodic photoelectrochemical activity and rapid adsorption capacity for Cr(VI) ions. Interestingly, the photocatalytic process of BiOI-Bi/N-C toward Cr(VI) was pH dependent. Under acidic medium, the synthesized material displayed efficient photocatalysis and achieved 95.0% photoreduction efficacy for Cr(VI) ions to Cr3+ within 30 min under visible light irradiation. Under neutral medium, Cr(VI) state showed a different photocatalytic process, and Cr(OH)3 as a product covered on BiOI-Bi/N-C, which decreased the electrochemical (EC) and photoelectrochemical (PEC) performance of BiOI-Bi/N-C. Based on the findings, BiOI-Bi/N-C was utilized as EC/PEC dual-model sensing interface for the detection of Cr(VI) ions. The presented dual-model sensing method displayed an ultralow limit of detection down to 6.8 pM for EC and 3.2 pM for PEC. It demonstrated the practical application potential for the assay of Cr(VI) in real samples.