Figure 7.

Schematic view of direct assays. (a) MR sensor surface pre-coated with target antibodies from testing sample followed by adding MNP-linked antigens for specific binding. The number of captured MNPs through antigen-antibody conjugations is proportional to the electrical/magnetic signals from MR sensors; (b) MR sensor surface pre-coated with target antigens from testing sample followed by adding MNP-linked antibodies; (c) MR sensor surface pre-coated with biotin followed by adding streptavidin-coated MNPs. This structure is mostly used as a positive control.