Digital immunoassays present distinctive analytical sensitivity for detecting low-abundance biomarkers, however their broad adoption is restricted by sensible obstacles. Business platforms are prohibitively costly for routine use in particular person laboratories, and laboratory-scale ideas usually describe specialised biosensors and complex workflows. Right here, we introduce a nanomembrane-based Catch-and-Show Immunoassay (CAD-IA), a cheap and laboratory-friendly digital immunoassay for frequent analysis settings. In CAD-IA, fluorescent nanoparticles are “captured” by the nanoscale pores of ultrathin silicon nitride membranes by a pipette powered filtration. The captured nanoparticles function optically remoted ‘hotspots’ for fluorescent immunocomplex formation when goal antigen is current. Co-localization of the fluorescent particles and fluorescent immunocomplexes are then “displayed” and quantified by customary confocal microscopy to generate digital indicators. CAD-IA is applied utilizing the µSiM-DX (microfluidic gadget that includes an ultrathin silicon membrane for diagnostics) platform, which is manually assembled from mass produced, cost-effective elements. Utilizing the traumatic mind harm (TBI) biomarker S100B as a mannequin, we exhibit that CAD-IA supplies constant digital outputs and linear quantification over a dynamic vary of at the least two orders of magnitude when digital and analog analyses are mixed on the identical picture units. We additional exhibit that the assay maintains linearity in serum matrices and achieves appropriate sensitivity (LoD = 0.02 µg mL−1) for clinically related diagnostic with the addition of tyramide sign amplification (TSA). Whereas additional optimization of CAD-IA is feasible, these outcomes represent a proof-of-concept demonstration of a novel digital immunoassay deployable in most analysis laboratories.
