Hyperdegranulation of neutrophilic granulocytes is a common finding in sepsis that directly contributes to the heightened immune response leading to organ dysfunction. Currently, cell degranulation is detected by flow cytometry, which requires large infrastructure that is not always available at the point of care. Here, we propose a plasmonic assay for detecting the degranulation status of septic cells colorimetrically. It is based on triggering the aggregation of gold nanoparticles with cationic granule proteins. Cells from septic patients contain fewer granules and therefore release less cationic proteins than healthy cells. This results in red-colored assays than can be easily detected by eye. The assay can selectively detect cationic granule proteins even in the presence of an excess of unrelated proteins, which is key to detect degranulation with high specificity. Coupling this signal generation mechanism with a magnetic purification step enabled the identification of septic cells with the same performance as flow cytometry. This makes the proposed method a promising alternative for diagnosing sepsis in decentralized healthcare schemes.
Keywords: bionanotechnology; cell-based assay; gold; naked eye; nanoparticle; neutrophil.