(A) Schematic illustration of capture of the alkaline-phosphate-(ALP-) coated CNT tags to the streptavidin-modified magnetic beads by (a) a sandwich DNA hybridization (b) Ab-Ag-Ab interaction. (B) Enzymatic reaction. (C) Electrochemical detection of the product produced from enzymatic reaction at the CNT-modified glassy carbon electrode, reprinted with permission from [65], Copyright 2001 American Chemical Society. MB: magnetic beads; P1: DNA probe 1, T: DNA target, P2: DNA probe 2, AB1: first antibody, Ag: antigen, Ab2: secondary antibody, S and P: substrate and product, respectively; GC: glassy carbon electrode, and CNT: carbon nanotube layer.
