Nanoparticle-assisted sacrificial synthesis of hierarchical porous carbon composite for rapid sample enrichment and ultrasensitive label-free immunosensing of interleukin-6 biomarker

Abstract To achieve an ultrasensitive biosensor, the modified nanomaterials with high specific surface area, proper chemical and electrical/optical properties are highly required. In the present work, we designed a rapid and ultrasensitive label-free electrochemical immunosensor for interleukin-6 (IL-6) detection based on nanoporous mesoporous-carbon (NMC) composite decorated with gold nanoparticles (NMC@AuNPs). The NMC served as the transducer matrix, which is modified on the surface of glassy carbon electrode (GCE), to deposit the gold nanoparticles (AuNPs). NMC is synthesized via a wrinkled SiO2-nanoparticle (wSiO2NP) assisted sacrificing strategy, which displays an interconnected 3D structure to achieve high specific surface area and abundant porous for rapid sample enrichment; meanwhile, the composited hierarchical porous structure promotes the deposition and entanglement of AuNPs to form stable NMC@AuNPs and achieve enhanced electrical conductivity. Specific antibody against IL-6 protein is immobilized onto the surface of AuNPs, based on the antibody-antigen recognition strategy, the constructed immunosensors demonstrate high sensitivity and selectivity for assay of IL-6 with a linear dynamic range of 0.5–1200 pg·mL-1 and the ultralow limit of detection (LOD) of 0.14 pg·mL-1. Toward the detection of IL-6 in human serum samples, this label-free biosensor with a short detection period (within 60 min, including sample processing and electrochemical measurement). Moreover, the label-free biosensor exhibited an excellent sensitivity and specificity, suggesting it possesses the potential for other biomarkers in point-of-care biosensing application.