Use of DNA immobilized on plastic and agarose supports to detect DNA by sandwich hybridization.

Cloned Salmonella DNA, which has been immobilized irreversibly on plastic and agarose solid supports, can form hybrids in both single-layer and "sandwich" hybridization protocols. In single-layer hybridization, 3 micrograms of immobilized DNA bound at least 30 fmol of a specific 800-base DNA sequence (equivalent to 8.5 ng, or the amount of that sequence present in 4 X 10(10) organisms). In a 4-h sandwich hybridization protocol, as little as 14 amol (equivalent to 8 pg, or the amount of that sequence present in 1 X 10(7) organisms) of a 1600-base sequence of DNA could be detected. The methods described should be applicable to use with any set of probes--not just from Salmonella--that fulfill the criteria specified. The ability to perform DNA hybridizations on solid-phase matrices such as those used for immunoassay should bring DNA hybridization into the realm of routine clinical laboratory procedures.