A ratio-type fluorescence approach based on dual-functional carbon dots with magnetic and luminescent features for IL-8 separation and detection

Ratio-based fluorescence assays can reduce environmental interference, allowing for the identification of biomarkers with higher specificity. However, the complicated preparation procedures involved in developing multi-fluorescent emission probes and the challenges associated with isolating and enriching specific biomarkers from complex samples present formidable obstacles. Magnetic nanoparticles enable the quick separation and enrichment of biomarkers, hence, the present study developed a ratio-fluorescence assay for the detection of interleukin-8 (IL-8) using carbon dots (CDs) with both magnetic and fluorescent properties. In this approach, magnetic and fluorescent Fe₃O₄-CDs-1 (FCs) hybrid nanoparticles were initially synthesized, followed by the growth of SiO₂ nanorods on their surface. FCs@SiO₂-Ab₁ was then prepared by immobilizing capture IL-8 antibody (Ab₁) through amino modification onto FCs@SiO₂ to selectively capture and enrich target IL-8 from samples. Subsequently, CDs-2 modified with detection IL-8 antibody (Ab₂) served as IL-8 detection probe, which formed sandwich structure with FCs@SiO₂-Ab₁ in the presence of IL-8. As the concentration of IL-8 increased, the fluorescence intensity of CDs-2 enhanced accordingly while the fluorescence intensity of FCs remained relatively unchanged. This ratio-fluorescence sensing platform exhibits a wide linear range (20-1000 pg·mL⁻¹) and an impressive low detection limit (6.9 pg·mL⁻¹). Furthermore, this method enables the reliable detection of IL-8 in human serum, thereby offering promising prospects for the development of enrichment and detection systems for other biomarkers.

Graphical Abstract