Protein A/G-based microfluidic platform for preparative microseparation of IgG from human serum

IgG antibodies represent the principal analytical target in serological assays due to their high antigen specificity and persistence in blood following infection or vaccination. However, such assays often suffer from matrix-derived background and variability that obscures diagnostic cut-offs. A pre-analytical sample treatment pathway offers a potential solution to these challenges, but existing IgG purification tools are often incompatible with miniaturized detection systems. This gap motivates the development of miniaturized, automation-ready pre-analytical modules for antibody separation. We developed an open-channel PET Lab-on-a-Foil cassette in which protein A/G-functionalized microchannels are able to reversibly capture IgG. An automated flow-control unit runs a bind-wash-elute sequence with pH-triggered IgG release, yielding ∼30 μL of eluate per run. ELISA showed that IgG-enriched fractions had C-reactive protein, used as an internal standard, reduced to background levels, and only residual free protein A/G was detected, consistent with minimal matrix carryover and ligand leaching. SARS-CoV-2 serology was employed as a validation model due to its clinical relevance and well-characterized antibody responses. In the assay detecting IgG anti-SARS-CoV-2 nucleoprotein, positive-serum eluates gave a 7.6-fold higher antigen-specific signal than negative-serum eluates, while blank signals were lower than in matched raw sera. In SPR experiments, reference-channel responses for three sera decreased by 80-90% after pre-treatment, confirming reduced nonspecific adsorption. By integrating IgG capture and acidic elution in a disposable PET cassette that can be interfaced with ELISA and SPR, the platform lowers blank signal and its variance near diagnostic cut-offs and offers a practical route toward automation-compatible point-of-care immunodiagnostics.