Affinity-Switchable Lateral Flow Assay.

Lateral flow assay (LFA) has been a valuable diagnostic tool in many important fields where rapid, simple, and on-site detection is required, for applications such as pregnancy tests and infectious disease prevention. Currently, two types of LFAs are available: lateral flow immunoassay (LFIA) and nucleic acid lateral flow assay (NALFA). Both are generally used for the testing of proteins and nucleic acids. However, enzyme activities and small molecules without the corresponding binding partner cannot be detected by the existing LFAs. In this paper, we introduce a LFA approach termed affinity-switchable lateral flow assay (ASLFA) to overcome the limitations. The detection principle is based on the switchable binding between the affinity-switchable biotin (ASB) probe and avidin protein. In the presence of the target molecule, the activated ASB probe would be captured by the avidin, thereby leaving a distinct test line on the membrane. The ASLFA concept was demonstrated by testing the F ion, NADH cofactor, and nitroreductase activity. Thus, this general ASLFA can be used for the rapid detection of molecules that cannot be accessed by the classical LFAs.