The presence of bacterial endotoxin, lipopolysaccharide (LPS) in the lung can induce a major inflammatory response leading to acute lung injury. LPS is thought to immediately activate resident macrophages, leading to the production of various cytokines, including TNF-α. This will, in turn, prompt the recruitment of inflammatory cells, mainly neutrophils, into the lung through increases in capillary permeability and alveolar edema.1 Neutrophil infiltration into the lung can be monitored by certain, activatable (smart) fluorescent probes. This study evaluates the use of an activatable optical probe that is optically silent upon inhalation and produces a fluorescent signal only after selective cleavage by the serine protease elastase produced by neutrophils.
