AVS 53rd International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI2-TuM

Paper BI2-TuM9
Biosensing with Fluidic Force Discrimination and Microbead Labels: Comparison of Sequential and Mixed-Homogeneous Assay Schemes

Tuesday, November 14, 2006, 10:40 am, Room 2014

Session: Biodiagnostic Innovation
Presenter: S.P. Mulvaney, Naval Research Laboratory
Authors: S.P. Mulvaney, Naval Research Laboratory
K.M. Myers, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
A significant challenge for all biosensors is to achieve high sensitivity and specificity while minimizing sample preparation requirements, protocol complexity, and assay time. We have achieved multiplexed, femtomolar detection of both DNA and proteins in complex matrices in minutes by labeling conventional assay schemes with micrometer-scale beads, and applying fluidic force discrimination (FFD). In such assays, analytes captured onto a microarray are labeled with microbeads, and nonspecifically bound bead labels are preferentially removed through the application of controlled microfluidic forces. The density of beads that remain bound is proportional to the analyte concentration. Our typical microbead-labeled assay uses a sequential scheme, whereby the biorecognition builds from the capture probe, to the target, to the label probe, and finally the bead label. Alternatively, a two-step mixed-homogeneous assay scheme is possible with microbead labels and FFD. In this scheme, the sample is mixed with all the reagents (including the microbeads) in solution, and the analyte-loaded beads are then allowed to interact with the capture probes on the microarray. In the second step, FFD is applied and the bound labels counted. This scheme holds potential for enhanced target capture via preconcentration, but the large relative size of the microbead label relative to the molecular analytes complicates the biophysics. Our analysis of the sequential vs. mixed-homogeneous assay schemes at high and low analyte concentrations will be discussed. @FootnoteText@ S.P.M. and K.M.M. are employees of Nova Research Inc., Alexandria, Va.