Plasmonic nanomaterials for label-free biosensor towards next-generation point-of-care immunoassay

Abstract

Cytokines, a broad category of low molecular weight signaling proteins, are key immune modulators for cell-based immune response. An abnormal level of cytokine can lead to acute/chronic inflammation, multiple organ failure, or even death. The current “gold standard” method for cytokine quantification is enzyme-linked immunosorbent assay (ELISA), which involves tedious labeling and washing process. In a current clinical laboratory setting, a minimum assay time of 3-8 h is required for simplex cytokine measurement. Considering a detrimental acute inflammation, characterized by the unregulated and increased level of cytokines, a personalized cytokine-blockade treatment needs to be delivered in time based on the individual’s transient immune status. In this regard, an unmet need is developing a next-generation multiplexed immunoassay allowing rapid cytokine analysis with sufficient sensitivity. Localized surface plasmon resonance (LSPR)-based immunoassay that exploits attractive optical properties of plasmonic nanomaterials is a promising candidate to bridge such a gap. In this dissertation, we demonstrated the development of point-of-care nanoplasmonic immunoassay from three aspects. Firstly, we developed a scalable manufacturing method for the parallel fabrication of multiplexed immunoassay by using the weasel hair-enabled calligraphy technique. Secondly, we improved the sensing performance of the current LSPR immunoassay by engineering conventional antibodies and adopting a new LSPR sensing methodology, i.e., digital LSPR. Lastly, we demonstrated the practical use of our label-free LSPR immunoassay to characterize the T cell responses to a type 2 diabetes biomarker, human islet amyloid polypeptide (hIAPP) with differing aggregation stages. Together, we demonstrated the developed LSPR immunoassays can be a promising tool for patient immune status monitoring and cellular functional analysis.