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miRNAs are among the novel biomarkers that can be evaluated for sensitive and early cancer diagnosis. In the present study, an electrochemical nanobiosensor has been fabricated to detect two gastric cancer (GC) related miRNAs simultaneously. By employing Au nanoparticles- and CdSe@CdS quantum dots-contained magnetic nanocomposites as electrochemical labels along with the polythiophene/reduced graphene oxide-modified carbon electrodes, this dual signal nanobiosensor showed a considerable performance in quantifying miR-106a (a GC oncogenic miRNA) and let-7a (a GC tumor suppressor miRNA). Using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), not only the accomplishment of desired biosensing platform construction was confirmed, but also its great specificity, appropriate selectivity, acceptable stability, and significant sensitivity were indicated. Through the combined analyses of the dual miRNAs, our nanobiosensor reached detection limit of 0.02 fM and 0.06 fM for let-7a and miR-106a, respectively. This multiplex PCR-free miRNA nanobiosensor demonstrates attractive potentials for promising applications in early diagnosis of GC and additionally the screen of any miRNA sequence.

Purpose Genetic diseases can be the result of genetic dysfunctions that happen due to some inhibitory and/or environmental risk factors, which are mostly called mutations. One of the most promising treatments for these diseases is correcting the faulty gene. Gene delivery systems are an important issue in improving the gene therapy efficiency. Therefore, the main purpose of this study was modifying graphene oxide nanoparticles by spermine in order to optimize the gene delivery system. Methods Graphene oxide/APTES was modified by spermine (GOAS) and characterized by FT-IR, DLS, SEM and AFM techniques. Then pEGFP-p53 was loaded on GOAS, transfected into cells and evaluated by fluorescent microscopy and gene expression techniques. Results FT-IR data approved the GOAS sheet formation. Ninety percent of the particles were less than 56 nm based on DLS analysis. SEM analysis indicated that the sheets were dispersed with no aggregation. AFM results confirmed the dispersed structures with thickness of 1.25±0.87 nm. STA analysis showed that GOAS started to decompose from 400°C and was very unstable during the heating process. The first weight loss up to 200°C was due to the evaporation of absorbed water, the second one observed in the range of 200–550°C was assigned to the decomposition of labile oxygen- and nitrogen-containing functional groups, and the third one above 550°C was attributed to the removal of oxygen functionalities. In vitro release of DNA demonstrated the efficient activity of the new synthesized system. Ninety percent of the cells were transfected and showed the GFP under fluorescence microscopy, and TP53 gene was expressed 51-fold in BT-20 cells compared to β-actin as the reference gene. Flow cytometry analysis confirmed the apoptosis of the cells rather than necrosis. Conclusion It could be concluded that the new synthesized structure could transfer a high amount of the therapeutic agent into cells with best activity.