Journal: ACS Nano
Article Title: Digital Immunoassays for Sensitive Quantification of Blood Biomarkers Using Solid-State Nanopores
doi: 10.1021/acsnano.5c16690
Figure Lengend Snippet: Nanopore amplification assay calibration curve and spike recovery. (a) Illustration of bead-based assay consisting of paramagnetic beads-capture antibody (PMB-cAb), antigen, and detection complex of DNA oligo-detector antibody decorated gold nanoparticles (AuNP-dAb). Streptavidin-coated paramagnetic beads (PMB-SA) and AuNP/biotinylated DNA oligo (AuNP) are used for validation of AuNP/oligo conjugation and oligo reporter release. (b) The complete assay immuno-sandwich is exposed to UV light to release DNA reporters, and NanoLock probes are added. The NanoLock reporter in its open state transforms into the locked state and sensed on a nanopore. Individual nanopore translocation events from an 8 pM GFAP (0.4 ng/mL) experiment and box plots of maximum blockage for GFAP assay concentrations of 0.51, 1.0, 2.1, 4.0, 8.2, 16.4, 32.9, and 65.8 pM. (c) Results of GFAP amplification assay, neat and diluted. Standard curve 1 (black) of GFAP concentrations, 0, 0.51, 1.0, 2.1, 4.0, 8.2, 16.4, 32.9, and 65.8 pM, for undiluted samples; and standard curve 2 (green) of GFAP concentrations, 12.8, 25.7, 51.4, 102.8, 205.6, 411.2, 822.4, and 1644.8 pM, for the diluted samples. The black and green lines indicate a 4PL fit of the standard curves for the two assay schemes, and the orange dashed line is the fit of the analog scheme using the capture rate. (d) Spike recovery for spike 1 (19.7 pM) and spike 2 (492 pM). Bar plots of spike 1 and spike 2 in two regimes, undiluted (gray, plain) and 25× diluted (light blue, sparse). (e) Time evolution of circular fraction as a function of an event, for GFAP concentrations ranging from 0.5 pM to 66 pM. The colored bands represent 1 standard deviation from the mean. Experiments are performed in 3.2 M LiCl at 200 mV using an 8 nm pore, all experiments are low-pass Bessel filtered at 200 kHz for analysis.
Article Snippet: 2.7 μm diameter carboxylated paramagnetic beads were conjugated with antihuman GFAP capture antibody (Quanterix, 102336).
Techniques: Amplification, Bead-based Assay, Biomarker Discovery, Conjugation Assay, Translocation Assay, Standard Deviation