Albumin-on-a-chip: binding profiling of circulating human albumin via selective immunocapture and real-time SPR analysis.

A cost-effective surface plasmon resonance (SPR)-based sensing platform was developed to evaluate alterations in albumin binding capacity under clinically relevant conditions. This ex vivo approach enables real-time assessment of albumin-ligand interactions using albumin directly isolated from plasma, thus overcoming key limitations of conventional in vitro approaches. The sensing surface was prepared by covalently immobilizing a polyclonal anti-albumin antibody onto a CM5 chip, followed by a single-step immunocapture of albumin from patient plasma samples. Mass spectrometry confirmed the selective retrieval of both native and structurally modified albumin forms, preserving their relative abundance and disease-associated microheterogeneity. The sensing surface demonstrated high reusability and analytical reproducibility over ~ 500 capture-release cycles, significantly lowering per-sample costs. Functional validation was performed using ligands targeting the three main albumin binding sites. As proof of application, the system was used to investigate albumin binding properties in plasma from (i) type 2 diabetic patients with (n = 10) and without (n = 10) moderate kidney impairment, and (ii) patients with cirrhosis and acute-on-chronic liver failure (n = 6), a condition associated with extensive albumin damage. The proposed approach provides a robust analytical framework for the functional characterization of circulating albumin in healthy and diseased conditions.