Mohsen Mohammadniaei
Chung-Ang University, Republic of Korea
Title: Two-mode electrochemical biosensor composed of gold nanoflower rna/barcode complex for broad and ultra-sensitive detection of microrna in cancer serum
Biography
Biography: Mohsen Mohammadniaei
Abstract
Statement of the Problem: Early cancer diagnosis is immensely vital to improve treatment outcomes and overall survivals. MicroRNAs as the short non-coding RNA sequences (18-24 nucleotides) are promising biomarkers for early cancer diagnosis due to their altered expression levels during cancer development. However, because of their very low abundance in body fluids, sensitive detection of microRNAs is still formidable. Current reliable miRNA detection methods necessitate amplification while either requiring several enzymes to make it costly and time-consuming. Moreover, one of the main limitations in developing any types of biosensors is that the sensitivity enhancement restricts the linear detection range.
Methodology & Theoretical Orientation: To resolve the abovementioned issues, here we propose a novel enzyme-free mechanism to detect microRNA-21 (miR-21) in total patient serum in a two-mode electrochemical system to significantly lower the miRNA detection limit while retaining a broad linear detection range. A three-way junction RNA structure is utilized and modified by (i) a methylene blue (MB)-labeled hairpin RNA at its one end, functioning as the capture probe and (ii) the other two ends for being hybridized with barcode gold nanoparticles (MB/barG) as the electrochemical signal boosters. Upon the target miR-21 invasion, the hairpin structure is opened and subsequently hybridizes with DNA-assembled gold nanoflower/platinum electrode (GNF@Pt). This brings the MB to the close vicinity of surface resulting in a detectable electrochemical signal (1st mode). To expand the biosensor dynamic detection range and amplify its sensitivity, MB/barG is hybridized to the 1st mode to form a dumbbell-like structure and establish the 2nd mode.
Conclusion & Significance: The integrated biosensor could detect 135 aM (324 molecules of miR-21 in only 4 µL sample) and represent a wide linear range from 1 µM to 500 aM in a back-to-back supporting system. The GNF@Pt displayed a remarkable conductivity and addition of MB/barG dramatically increased the MB electrochemical signal by ~230 folds. Further, a novel protocol was introduced to enhance microRNA extraction efficiency from the total serum by ~60%. The developed biosensor showed a high selectivity and specificity towards single base-pair mismatches and could profile different development stages of two cancer serums (breast and liver).