Two pulmonary interfaces play the key role in respiratory infections, both bacterial and viral (e.g., COVID19). The invaders enter via external interface formed by airway and alveolar epithelial cells. The adjacent internal vascular interface formed by endothelial cells recruits and other host defense including neutrophils (PMN) to invasion site. Overzealous PMN hurt endothelium. Emerging reports implicate this collateral damage in COVID19 poor outcomes. Anti-inflammatory drugs could alleviate this issue, but pose risk of infection spread. To protect lungs from "friendly fire" without inhibiting PMN fighting infection we target nanocarriers loaded with anti-inflammatory agents using affinity ligands binding to specific epitopes on the pulmonary endothelium. Fortuitously, pilot screening of ~30 nanoparticles revealed that after IV injection some formulations lacking affinity ligands accumulate in the PMN in inflamed lungs. We want to use these findings for dual drug delivery to endothelium and adjacent PMN. In Aim 1, we will interrogate the nano-scale interface between the surface of PMN- tropic nanocarriers and microenvironment to elucidate the mechanism of PMN uptake. In Aim 2, we will investigate effect of endothelial- and PMN-tropic nanocarriers on the micro-scale interface of pulmonary microvasculature. These studies will elucidate the fundamental mechanisms by which nanocarrier material properties dictate opsonization, and in turn tropism for PMNs, the most important leukocyte in pneumonia. We will determine how nanocarriers localize to the two key cell types in defense against pneumonia, thus creating a platform drug delivery system to treat both bacterial and viral pneumonia.