Electric Field-Enhanced Sensitivity of Grafted Ligands and Receptors

Particle-based agglutination tests consisting of receptors grafted to colloidal microparticles are useful for detecting small quantities of corresponding ligands of interest in fluid test samples, but detection limits of such tests are limited to a certain concentration and it is most desirable to lower the detection limits and to enhance the rate of recognition of ligands. A mixture of receptor-coated colloidal microparticles and corresponding ligand was sandwiched between 2 indium tin oxide-coated glass plates. Electrohydrodynamic drag from an alternating-current electric field applied perpendicular to the plates increased the local concentration of the colloidal particles, improving the chances of ligand-receptor interaction and leading to the aggregation of the colloidal particles. With this technique the sensitivity of the ligand-receptor recognition was increased by a factor as large as 50. This method can improve the sensitivity of particle-based agglutination tests used in immunoassays and many other applications such as immunoprecipitation and chemical sniffing.