A three-dimensional cloth-based microfluidic label-free proximity hybridization-electrochemiluminescence biosensor for ultrasensitive detection of K-ras gene.

• A cloth-based microfluidic proximity hybridization-electrochemiluminescence (PH-ECL) DNA biosensor is firstly proposed. • The "H"-shaped complexes increase the sensitivity and selectivity of label-free PH-ECL biosensor. • The multi-walled carbon nanotubes-chitosan can be well used for electrode modification to further improve the sensitivity. • The K-ras gene levels in complex human serum samples can be measured. • The universal determination of different DNA targets can be well achieved. In this work, we firstly propose a cloth-based microfluidic DNA biosensor capable of label-free proximity hybridization-electrochemiluminescence (PH-ECL) detection of target DNA (T-DNA). Carbon ink screen-printing is applied to make the cloth-based electrodes that are patterned with wax-screen-printed cloth-based chambers to fabricate a foldable three-dimensional (3-D) cloth-based device for facile fabrication of multi-walled carbon nanotubes (MWCNTs)-modified PH-ECL sensing interface. When the PH complexes (PC) formed by the T-DNA and help DNA sequences (H-DNA1 and H-DNA2), together with Ru(bpy) 3 2+ (TBR) molecules, are applied onto such a sensing interface, the TBR/tripropylamine (TPA)-based PH-ECL can be well triggered. Under optimized conditions, the biosensor has successfully fulfilled the label-free detection of K-ras gene in the linear range of 0.001–2500 pM, with a detection limit of 0.13 fM. The emission of PH-ECL on the cloth-based device exhibits a relatively high sensitivity, specificity, reproducibility and stability, possibly due to the good formation of "H"-shaped complexes on the electrode. Especially, the biosensor has the ability for K-ras gene detection in complex human serum samples, identification of single-base-mismatched and even two-base-mismatched K-ras gene targets, and universal determination of different T-DNA samples. Thus, it may become a promising avenue for gene diagnostics with wide applications. [ABSTRACT FROM AUTHOR]