Nanosheets-assembled hollow CdIn2S4 microspheres-based photoelectrochemical and fluorescent dual-mode aptasensor for highly sensitive assay of 17β-estradiol based on magnetic separation and enzyme catalytic amplification

The specific and accurate quantitation of environmental endogenous estrogens is traditionally recognized as a vital strategy in environment, health and disease. In this work, nanosheet-assembled hollow CdIn2S4 microspheres were prepared by a one-pot solvothermal method, which attained strong photoelectrochemical signals and applied to build a novel dual-mode aptasensor by integration with fluorescent signals for accurate and selective detection of 17β-estradiol (E2). Specifically, alkaline phosphatase (ALP) modified E2 aptamer (ALP-Apt) was released from magnetic beads (which can effectively achieve the hydrolysis of l-ascorbic acid 2-phosphate (AAP) to form ascorbic acid (AA)), in turn increasing the photocurrents at the photoelectric nano-interface. Simultaneously, the decrease in the double stranded DNA (dsDNA) on the magnetic beads surface also weakened fluorescence signals upon the presence of Helixyte Green™. Under optimal conditions, the as-developed dual-mode aptasensor displayed the wide linear range of 0.1 ∼ 200 nM by the PEC analysis and 0.1 ∼ 100 nM by the fluorimetric assay for detecting E2. This method provides a novel and efficient dual-mode biosensing strategy for promising analysis of small molecular in environmental pollutants.