Development of binding assays in microfabricated picoliter vials: An assayfor biotin

A homogeneous binding assay for the detection of biotin in picoliter vials was developed using the photoprotein aequorin as the label. The binding ass ay was based on the competition of free biotin with biotinylated aequorin ( AEQ-biotin) for avidin. A sequential protocol was used, and modification of the assay to reduce the number of steps was examined. Results showed that detection limits on the order of 10(-14) mol of biotin were possible. Reduc ing the number of steps provided similar detection limits but only if the a mount of avidin used was decreased. These binding assays based on picoliter volumes have potential applications in a variety of fields, including micr oanalysis and single-cell analysis, where the amount of sample is limited. In addition, these assays are suitable for the high-throughput screening of biopharmaceuticals.