Colorimetric detection of D-dimer in a paper-based immunodetection device

A microfluidic paper-based analytical device (μPADs) immunoassay for detection of the blood native biomarker D-dimer is reported. The μPAD is created by wax printing on a single piece of chromatographic paper and combined with an anti-D-dimer capture antibody and conjugates of anti-D-dimer antibody with 40 nm gold nanoparticles. The presence of D-dimer in buffer/simulated plasma samples is successfully reported for concentrations as low as 15 ng D-dimer/mL. Linearity between signal intensity and D-dimer concentration is observed up to 100 ng/mL. Using an appropriate dilution, the test could be used to yield positive results only for those samples with a D-dimer concentration above the clinically relevant threshold range of 250-500 ng/mL. Finally, the merits and pitfalls of using μPADs as compared to lateral flow devices in immunoassays are discussed.