Schematic display of HCR-based miRNA immunosensing: (A) preparation of MBs including modification with AbS9.6, selective capture of the target miRNA/HP heteroduplex, HCR at the MBs by hybridization of the HP with AP1 and AP2 probes, and labeling of the biotin moieties with Strep-HRP. (B) Magnetic attraction of the modified MBs to the surface of the working electrodes (via magnet placed below the array) and chronoamperometric measurement of the enzymatic reduction of H2O mediated by hydroquinone. The cathodic current increased with the concentration of the target miRNA. Reproduced from Multiplexed Immunosensing Platform Coupled to Hybridization Chain Reaction for Electrochemical Determination of Micro RNAs in Clinical Samples, Jirakova, L.; Hrstka, R.; Campuzano, S.; Pingarrón, J.M.; Bartosik, M. Electroanalysis, Vol. 31, Issue 2 (ref 21). Copyright 2019 Wiley.