Detection of Escherichia coli rRNA using target amplification and time-resolved fluorescence detection

Time-resolved fluorescence immunoassay (TRFIA) for the detection of Escherichia coli O157:H7 in apple cider

An immunoassay based on immunomagnetic separation and time-resolved fluorometry was developed for the detection of E. coli O157:H7 in apple cider. The time-resolved fluorescent immunoassay (TRFIA) uses a polyclonal antibody bound to immunomagnetic beads as the capture antibody and the same antibody labeled with europium as the detection antibody. Cell suspensions of 10(1) to 10(8) E. coli O157:H7 and K-12 organisms per ml were used to test the sensitivity and specificity of the assay. The sensitivity of the assay was 10(3) E. coli O157:H7 cells with no cross-reaction with K-12. Pure cultures of E. coli O157:H7 (10(1) to 10(5) CFU/ml) in apple cider could be detected within 6 h, including 4 h for incubation in modified EC broth with novobiocin and 2 h for the immunoassay. When apple cider was spiked with 1 to 10(3) CFU/ml of E. coli O157:H7 and 10(6) CFU/ml of K-12, our data show that the high level of K-12 in apple cider did not impede the detection of low levels of O157:H7. The minimum detectable numbers of cells present in the initial inoculum were 10(2) and 10(1) CFU/ml after 4- and 6-h enrichment. The TRFIA provides a rapid and sensitive means of detecting E. coli O157:H7 in apple cider.

Ultrasensitive bioanalytical assays using time-resolved fluorescence detection

This article reviews the use of time-resolved fluorimetric detection of lanthanide chelate luminescence as a detection method for ultrasensitive bioanalytical assays. Assay formats and detection methods, and the principle of time-resolved fluorimetric detection, are described. Detection systems, assay formats, reagents, and instrumentation for time-resolved fluorimetric detection are outlined. A review of published and commercially available immunoassays and DNA hybridization assays using time-resolved fluorimetric detection of lanthanide chelate luminescence is given.

Time-resolved detection of lanthanide luminescence for ultrasensitive bioanalytical assays

The principles and practice of the application of time-resolved lanthanide chelate luminescence (or fluorescence) as a detection method for ultrasensitive bioanalytical assays such as immunoassays and nucleic acid hybridization assays are reviewed. The various lanthanide chelate-based detection systems which have been developed for use in heterogeneous and homogeneous assay formats are described, including reagents, assay methods, and instrumentation, along with recent improvements in these methods. Detection systems described include those based on dissociative enhancement of lanthanide ions, direct labeling with luminescent chelates, enzyme-amplified lanthanide luminescence, lanthanide luminescence quenching, and energy transfer.

Time-resolved fluorometry in nucleic acid hybridization and western blotting techniques

Time-resolved fluorometry is now used extensively for immunological assays and to a lesser extent in other research areas. In this review I describe applications of time-resolved fluorometry in nucleic acid hybridization and in blotting techniques, including Southern and Western blotting. Clearly, time-resolved fluorometry has potential for playing a major role in techniques other than immunological assays.

Solid-phase time-resolved fluorescence detection of human immunodeficiency virus polymerase chain reaction amplification products

A new assay system for the detection of polymerase chain reaction (PCR) amplification products is presented. This single-pot sandwich assay system employs solid-support oligonucleotide-coated capture beads, a rare earth metal chelate-labeled probe, and a time-resolved fluorescence detection. The new assay system was evaluated for various reaction conditions including, DNA denaturation time, hybridization salt concentration, probe concentration, and hybridization time, all of which are important in designing an assay with a high level of sensitivity for the detection of duplex DNA. This nonisotopic assay system was applied to the detection of purified human immunodeficiency virus (HIV) DNA and sensitivity was compared with agarose gel electrophoresis and slot blot hybridization using a 32P-labeled probe. We were able to detect the amplified product from one copy of HIV DNA after 35 cycles of PCR amplification in less than 30 min using this assay, which compared with one copy by gel electrophoresis after 40 cycles of PCR amplification and one copy by slot blot hybridization after 35 cycles of PCR amplification and an overnight exposure of the autoradiogram. Thus, this assay is rapid, sensitive, and easy to use.