Ionic-liquid-based aqueous biphasic systems meet microfluidics: from antibodies to aptamers in prostate-specific antigen detection.

[BACKGROUND] Prostate-specific antigen (PSA) is the most widely used biomarker for prostate cancer screening; still, its reliable quantification in human serum remains challenging due to matrix complexity and high-abundance proteins that interfere with target recognition and signal generation. These limitations reduce the performance of biosensing microfluidic platforms. Ionic-liquid-based aqueous biphasic systems (IL-ABS) have been proposed as effective serum pretreatment tools, enabling selective depletion of high-abundance proteins, analyte preconcentration, and seamless integration with microfluidic devices. However, the synergistic combination of IL-ABS with microfluidic immunoassays has so far been restricted to antibody-based formats, which are limited in stability, cost, and target accessibility.

[RESULTS] Here, the analytical scope of the combined IL-ABS pretreatment and microfluidic detection platform is expanded beyond conventional antibody-based formats by introducing aptamers as recognition elements. The resulting aptamer-based sandwich immunoassay was benchmarked against the conventional antibody-antibody format, demonstrating superior sensitivity and a limit of detection of 7.49 ng mL, within the clinically relevant range for PSA screening.

[SIGNIFICANCE] This work pioneers the combined use of IL-ABS pretreatment and aptamer-based microfluidic detection for PSA. Aptamers, as synthetic ligands, offer high specificity, enhanced stability, and flexible design, providing a cost-effective alternative to antibodies. Incorporating aptamer recognition enhances analytical performance relative to conventional antibody-based assays, highlighting the platform's potential for broader clinical and point-of-care applications.