Whole-cell sensing for a harmful bloom-forming microscopic alga by measuring antibody--antigen forces.

Aureococcus anophagefferens, a harmful bloom-forming alga responsible for brown tides in estuaries of the Middle Atlantic U.S., has been investigated by atomic force microscopy for the first time, using probes functionalized with a monoclonal antibody specific for the alga. The rupture force between a single monoclonal antibody and the surface of A. anophagefferens was experimentally found to be 246 +/- 11 pN at the load rate of 12 nN/s. Force histograms for A. anophagefferens and other similarly-sized algae are presented and analyzed. The results illustrate the effects of load rates, and demonstrate that force-distance measurements can be used to build biosensors with high signal-to-noise ratios for A. anophagefferens. The methods described in this paper can be used, in principle, to construct sensors with single-cell resolution for arbitrary cells for which monoclonal antibodies are available.