LAMP-CRISPR/Cas12a-based impedimetric biosensor powered by Fe3O4@Au-(S-polyA-S)-Au for detection of SARS-CoV-2.

A low-cost, lab-made polytetrafluoroethylene micro-cell, equipped with three electrodes, wasd eveloped for the impedimetric detection of SARS-CoV-2. The gold working electrode was modified with a double-ended thiolated poly-adenine probe, which was conjugated with magnetic Fe3O4@Au nanoparticles (Fe3O4@Au-(S-polyA-S)-Au). After the loop-mediated isothermal amplification (LAMP) of viral RNA, the single-guide RNA (sgRNA), specifically bound to the SARS-CoV-2 target sequence, activates Cas12a. Cas12a then cleaved the immobilized probe. As a result, the magnetic Fe3O4@Au nanoparticles were released and adsorbed onto the gold electrode surface, using an external magnet. This process increased the physical surface area of the gold electrode, facilitating redox ion ([FeIII/II(CN)6]3-/4-) electron transfer. The decrease in the charge transfer resistance was utilized for SARS-CoV-2 detection. Our LAMP-CRISPR/Cas12a-based impedimetric biosensor, powered by Fe3O4@Au-(S-polyA-S)-Au, demonstrated impressive capabilities, including a remarkable detection limit of 0.8 aM (0.48 copies/µL) and a linear range of 0.01 to 36.06 fM.

Reconnaissance of the candidate genes involved in the pathogenesis of human immunodeficiency virus and targeted by antiretroviral therapy.

The expression levels of many genes change after treatment of human immunodeficiency virus (HIV)-infected subjects by antiretroviral drugs. High-throughput analysis of tremendous datasets led to the discovery of genes that are implicated in the treatment pathways. In this study, we performed a gene-enrichment analysis after determining the differentially expressed genes (DEGs) between untreated HIV-positive and HIV-negative subjects and also between treated HIV-positive subjects with antiretroviral therapy (ART; who receiving nucleoside reverse transcriptase inhibitor-based ART) and untreated HIV-positive cases in the peripheral blood mononuclear cells (PBMCs), adipose, and muscle tissues. In sum, the genes that activate inflammatory, immune response, proliferation, metabolism, and viral involvement pathways have different expression patterns in the untreated HIV-positive subjects and treated HIV-positive cases. Moreover, the expression levels of the genes including ACLY, ALDH18A1, HADHA, and YARS in the PBMCs tissue and HBEGF, PKN3, DEGS2, and EDN3 in the fat tissue were found to be different in the HIV-infected patients, which can be considered as new biomarkers for HIV infection.

Ultrasensitive optical biosensor for detection of miRNA-155 using positively charged Au nanoparticles.

An ultrasensitive optical biosensor for microRNA-155 (miR-155) was developed to diagnose breast cancer at early stages. At first, the probe DNA covalently bind to the negatively charged gold nanoparticles (citrate-capped AuNPs). Then, the target miR-155 electrostatically adsorb onto the positively charged gold nanoparticles (polyethylenimine-capped AuNP) surface. Finally, by mixing citrate-capped AuNP/probe and polyethylenimine-capped AuNP/miR-155, hybridization occurs and the optical signal of the mixture give a measure to quantify the miR-155 content. The proposed biosensor is able to specify 3-base-pair mismatches and genomic DNA from target miR-155. The novelty of this biosensor is in its ability to trap the label-free target by its branched positively charged polyethylenimine. This method increases loading the target on the polyethylenimine-capped AuNPs' surface. So, proposed sensor enables miR-155 detection at very low concentrations with the detection limit of 100 aM and a wide linear range from 100 aM to 100 fM.