High-sensitivity biosensor based on SERS integrated with dendrimer-assisted boronic acid-functionalized magnetic nanoparticles for IL-6 detection in human serum

High-sensitivity quantitative analysis of sepsis disease markers in circulating blood is essential for sepsis early diagnosis, rapid stratification, and interventional treatment. Herein, a high-sensitivity biosensor combining surface-enhanced Raman spectroscopy (SERS) and functionalized magnetic materials was developed to quantitatively detect interleukin-6 (IL-6), a glycoprotein disease marker closely related to sepsis. First, boronic acid-functionalized magnetic nanomaterials with high adsorption performance were synthesized by utilizing the branched polyethyleneimine to provide many binding sites for boronic acid. Under antibody-free conditions, dendrimer-assisted boronic acid-functionalized magnetic nanomaterials selectively capture glycoproteins in complex biological samples as bio-capture element. Then, a core-shell bimetallic material with plenty of 'hot spots' was designed and synthesized as the enhancement substrate. The 4-Mercaptobenzonitrile (4-MP) with a characteristic peak at 2224 cm-1(Raman-silent region) was embedded as the Raman reporter to form a SERS immune probe with highly efficient electromagnetic enhancement effect, achieving specific recognition and high-sensitivity detection of IL-6 on bio-capture elements. Using this strategy for quantitative analysis of IL-6, a wide detection range (0.5-5000 pg ml-1) and a low detection limit (0.453 pg ml-1) were obtained. Moreover, this method exhibited excellent detection performance for IL-6 in human serum samples, demonstrating its potential promise in screening clinically relevant diseases. The biosensor presented here not only provides a novel and universally applicable sensing strategy for the enrichment and detection of trace glycoprotein disease markers, but also the application of a portable Raman spectrometer provides a more reliable experimental basis for the diagnosis and treatment of major diseases in the clinic or remote and deprived areas.