Dual-modal biosensor for highly sensitive and selective DNA methyltransferase activity detection based on a porous organic polymer-inorganic nanocomposite (Cu2O@FePPOPBADE) with high laccase-like activity

Abstract

Abnormal DNA Methyltransferase (MTase) activity is closely related with multiple human diseases, which triggered its accurate and sensitive detecting demands. Here, an electrochemical and colorimetric, dual-modal biosensor for Dam MTase (Dam) assay was developed based on an organic-inorganic nanocomposite (Cu2O@FePPOPBADE). Stemming from the laccase-like activity of Cu2O, the catalytic activity of ferriporphyrin and excellent protective effect of the FePPOPBADE shell, Cu2O@FePPOPBADE not only exhibited significantly improved laccase-like activity to catalyze the chromogenic reaction of 2,4-dichlorophenol (2,4-DP) with 4-aminoantipyrine (4-AP), but possessed a strong electrochemical signal. Cu2O@FePPOPBADE was further functionalize with Au nanoparticles and served as a signal probe (Cu2O@FePPOPBADE@AuNPs). Also, magnetic bead (MB)/dsDNA was designed by assembly of streptavidin-modified MB with biotinylated-terminated ssDNA1 and thiolated-terminated ssDNA2, both of which contained specific sequences 5′-G-A-T-C-3′. When Dam and Dpn I were present, the specific sequence of dsDNA is methylated by Dam and then is cut by Dpn I, causing the leaving of thiolated-terminated ssDNA2. Sequentially, the residual MB/dsDNA is linked to the Cu2O@FePPOPBADE@AuNPs probe via Au-S bonds. After another magnetic separation, the unlinked Cu2O@FePPOPBADE@AuNPs left in the supernatant were transferred to accomplish the “dual signal-on” analysis of Dam with lower detection limits and high specificity.