Xiao Yang,Minghui Feng,Jianfei Xia,Feifei Zhang,Zonghua Wang
A novel electrochemical biosensor based on AuNPs/Ti 3 C 2 MXene three-dimensional nanocomposite for sensitive miRNA-155 detection by exonuclease III (Exo III)-aided cascade target recycling is reported. Ti 3 C 2 MXene is synthesized and used as a support to immobilize Au nanoparticles (AuNPs) due to its special layered structure and metallic properties. The three-dimensional (3D) structure of the AuNPs/Ti 3 C 2 MXene nanocomposite for the biosensor platform leverages the integrated advantages of a large specific surface area, excellent electrical conductivity and electrocatalytic properties . AuNPs are used to immobilize capture DNA (C-DNA) by Au S chemical bonds. The C-DNA was modified with methylene blue (MB) at the 3′ end, resulting in an initial DPV electrochemical signal ( I d ). In the presence of target, miRNA-155 and C-DNA formed a double-stranded structure by complementary base pairing. Subsequently, Exo III digested the 3′ end of the C-DNA in the double-stranded structure and caused the electrochemical signal to “turn off” (the final signal denoted as I h ). By Exo III-aided cascade cleavage of the target, one miRNA-155 chain causes the release of several C-DNAs under certain conditions, which significantly amplifies the peak current difference on the fabricated biosensor (Δ I = I d ﹣ I h ). The electrochemical sensor achieved a detection limit of 0.35 fM (S/N = 3) with a linear range from 1.0 fM to 10 nM. This sensor also shows desirable stability, reproducibility and specificity.
The microRNA family shows great promise for the diagnosis and prediction of different cancers as biomarkers, in which miRNA-155 (miR155) is recognized as a biomarker for lung cancer and thus has drawn much attention. Therefore, the development of specific and accurate methods to detect miR155 has become a potential research hotspot. In this work, we presented a fluorescence resonance energy transfer (FRET) technique by utilizing core–shell CdSeTe/ZnS quantum dots (QDs) as a signal reporter and a target recycling strategy as a signal amplifier for the detection of miR155. In the presence of miR155, part of the hairpin probe (HP) immobilized onto the surface of gold nanoparticles (AuNPs)@SiO2, could hybridize with it. Then, numerous H1-AuNPs@SiO2 could be produced with the aid of exonuclease III. With the linkage of the assistant chain A2, H1-AuNPs@SiO2 combined with A1-QDs and then the fluorescence (FL) signal of QDs was quenched by AuNPs@SiO2via FRET. The more miR155 present in solution, the weaker the detected FL signal. A linear response range of 0.01 fM to 1 nM and low detection limit of 3 aM were obtained using the proposed method. Furthermore, this method showed high specificity and satisfactory recovery between 93 and 105% in real human serum samples, illustrating its great potential for practical applications.
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