A nanoplasmonic cell-on-a-chip for in situ monitoring of PD-L1⁺ exosome-mediated immune modulation

Despite the transformative impact of immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 pathway in cancer therapy, up to 80% of patients fail to respond, necessitating reliable predictive biomarkers to guide treatment decisions. Recent studies highlight the critical role of tumor-derived exosomal PD-L1 in immune evasion, and its potential as a diagnostic and prognostic biomarker in cancer immunotherapy. However, significant challenges remain in elucidating the functional roles of PD-L1⁺ exosomes in immune suppression, as current methods lack the ability to precisely and simultaneously characterize and monitor exosome secretion and the corresponding immune modulation on site. To address this, we developed an integrated microfluidic platform that combines a digital nanoplasmonic immunoassay with a cell-on-a-chip system, enabling in situ monitoring of PD-L1⁺ exosome secretion and exosome-mediated T cell immune responses. This nanoplasmonic immunoassay integrated cell-on-a-chip (NIIC) creates a localized co-cultured microenvironment that facilitates exosome-mediated cellular interactions without direct contact. The NIIC employs machine-learning assisted signal processing for highly sensitive detection of both exosomes and cytokines, providing spatial and quantitative analysis of immune modulation in situ. Using this system, we demonstrated that PD-L1⁺ exosomes from cancer cells significantly suppressed IFN-γ and IL-2 secretion in neighboring T cells, offering direct insights into exosome-mediated immune suppression. The NIIC platform represents a powerful tool for advancing the understanding of exosome-driven immune modulation and holds potential for predicting clinical responses to anti-PD-1/PD-L1 therapies, paving the way for more personalized cancer immunotherapy strategies.