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.

Simultaneous Quantitative Detection of IL-6 and PCT Using SERS magnetic immunoassay with sandwich structure.

Sepsis is a systemic inflammatory response syndrome caused by infection. The mortality rate is as high as 30%-50%. Early diagnosis and treatment can significantly improve the mortality of patients with sepsis. Therefore, we have developed a SERS-based magnetic immunoassay method that uses the principle of sandwich method to quantitatively detect Interleukin 6 (IL-6) and Procalcitonin (PCT). In this article, two different Raman reporter molecules are embedded in the middle of the Au@Ag shell and coupled with the tracer antibody to form a SERS immunoprobe. Biotin was coupled with capture antibody to form a sandwich structure when participating in the immune response. Streptavidin and biotin systems have extremely high binding affinity. The sandwich structure is quickly captured by SA magnetic beads and then applied with a magnetic field to enrich the magnetic beads. Finally, simultaneous quantitative detection is achieved by the intensity of the two Raman reporter characteristic peaks on the solution magnetic beads. IL-6 and PCT showed a good relationship between 0-1000 pg ml-1and 0-20 ng ml-1, respectively, and the limits of detection were 0.54 pg ml-1and 0.042 ng ml-1, respectively. The recovery rate was between 89.8% and 104.2%, both intra-assay and inter-assay CV were ≤20%. No cross-reaction with C-reactive protein (100µg ml-1), showing good specificity. This method provides a new technical reference for the clinical detection of sepsis biomarkers.