Finding a small cytokine inside complex biological matrices using nanobody-functionalized plasmonic metasurfaces
Year: 2026
Type: preprint
Abstract: Interleukin-6 (IL-6) is a key inflammatory cytokine involved in numerous physiological and pathological processes, including cancer progression, fibrosis, and immune regulation. Rapid and label-free detection of IL-6 in complex biological environments is challenging due to its small size, which is overshadowed by the presence of large numbers of competing biomolecules. In this work, we develop a method to detect the spectroscopic signature of IL-6 in complex matrices using a nanobodyfunctionalized plasmonic metasurface that acts as a surface-enhanced Raman spectroscopy (SERS) sensor. Machine-learning-based spectral analysis enables identification of subtle molecular signatures of IL-6, despite the presence of competing species. We measured binary protein solutions containing IL-6 and bovine serum albumin (BSA), followed by IL-6-spiked cell culture medium and fibroblastconditioned culture medium. The mixed IL-6/BSA experiments show that elevated IL-6 scores can be recovered even at BSA-to-IL-6 ratios up to 100:1. In cell culture medium, the IL-6 score depends on the concentration and the observed trend deviates from the well-known Langmuir isotherm model. We developed a model that considers IL-6 binding on the nanobodies as a two-site adsorption problem that accounts for the metasurface geometry and steric effects. The model agrees well with the experimental data. Transforming growth factor beta (TGF-β)-stimulated fibroblast samples show a modest shift toward higher IL-6 scores than medium samples without TGF-β stimulation. Our approach is versatile and applicable to analyzing other biomolecules in a complex biological ‘soup’ of molecules and proteins.
Source: ChemRxiv
Institution: University of Twente
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221672813