Investigation of magneto-immunoassays in lateral flow format

• Main Author: Barnett, Jacqueline Mary
• Published: University of the West of England, Bristol 2008
• Subjects: 616.07
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504854

This study investigates the development of immunochromatographic assays also known as lateral flow assays with paramagnetic particles (PMP) used as a solid phase and label. The PMPs were quantified by virtue of their magnetic properties using a device known as the Resonant Coil Magnetometer (RCM) which is comprised of a capacitor and coil in series. A direct correlation between number ofPMPs present on nitrocellulose membrane and response in the RCM was observed using four coil configurations, the sensitivity and the limit of detection of the RCM varied depending on the coil design. Membrane and paramagnetic particle combinations were chosen following the evaluation of a range of nitrocellulose membranes and paramagnetic particles and used in the development of lateral flow assays for the quantification of hTransferrin (model) and total and free Prostate specific antigen (PSA). Limits of detection of lng/ml and 5ng/ml measured by scanning densitometer or RCM respectively, were at clinically significant concentrations for free PSA and total PSA. A high coefficient of variation was observed with both measuring systems due to the manual preparation of the assay strips, but was greatest with the RCM where the manual positioning of the capture lines in relation to the sensing coil increased variability. Anonymous serum samples evaluated in the total PSA lateral flow assay in comparison to Immulite and FastPack assays showed a negative proportional bias when measured using the scanning densitometer. The RCM was found to underestimate PSA concentrations where PSA concentrations were >18ng/ml, but a positive proportional bias was observed at lower PSA concentrations. Higher CV values were observed in the data obtained from the RCM. This may explain the different profiles obtained using the two measuring systems in comparison to commercially available immunoassays. Differences may also be due to the ability of the RCM to quantify PMPs present throughout the membrane and not just at the membrane surface as seen with the scanning densitometer. This study has shown that PMPs can be used as a solid phase and label in lateral flow assays and the quantification of analyte in standard and serum samples demonstrates the potential of the RCM as a device for the quantification ofmultiple analytes at the point-of-care.