Black phosphorus nanosheets adhering to thionine-doped 2D MOF as a smart aptasensor enabling accurate capture and ratiometric electrochemical detection of target microRNA

Novel two-dimensional (2D) metal-organic frameworks (MOF) were one-pot prepared by solvothermal reaction, using copper nitrate and 4,4’,4’’,4’’’-(porphine-5,10,15,20-tetrayl)tetrakis benzoic acid as precursors and thionine (TH) as the doping component. Black phosphorus nanosheets (BPNSs) were prepared by liquid-phase exfoliation of bulk crystals and were adhered to TH-doped 2D MOF (TH/Cu-MOF) to produce BPNSs/TH/Cu-MOF complex. The complex was drop-casted on glassy carbon electrode (GCE) to construct BPNSs/TH/Cu-MOF/GCE, followed by combining ferrocene (Fc)-labeled single-strand DNA aptamer to form aptamer-BPNSs/TH/Cu-MOF nanohybrid on GCE. The formation process of nanohybrid was characterized and experiment conditions were optimized. Under optimal conditions, the aptamer-BPNSs/TH/Cu-MOF/GCE platform served as a smart ratiometric electrochemical aptasensor that can accurately capture and detect microRNA (miR3123). With increase of miR3123 concentration (CmiR3123), the redox peak current of Fc (IFc) decreased, because special combination of Fc-aptamer with miR3123 led to Fc away from GCE surface. TH was doped into 2D MOF and its peak current (ITH) had negligible changes. TH and Fc acted as reference signal and response signal, respectively. There is a plotted linear relationship between (IFc/ITH) and logarithm of CmiR3123 in the range from 2 pM to 2 μM, together with a low limit of detection of 0.3 pM. The aptasensor had high sensitivity, selectivity and stability, and was applied to accurate detection of miR3123 in practical samples, showing high practicability.