Severe pneumonia caused by bacteria remains a serious clinical challenge, because the mucus in the lower respiratory tract hinders the effective utilization of antibiotics. Thus, drug delivery systems with mucus-penetrating and infection-responsive releasing capabilities show great significance for lung infection treatment. Herein, based on natural polysaccharide oxidized soluble starch (OSS), a responsive nano-agent (OTP) that could overcome mucus barrier was designed and fabricated for lung infection therapy. By Schiff base reaction and non-covalent interaction, OSS was crosslinked with tobramycin (TOB), and the dispersity and mucus-penetrating properties were enhanced by PEGylation. The loaded TOB could be responsively released by the triggering of slightly acidic environment of infection, owning to the pH-sensitive imine bond, which improved the drug delivery efficiency to the infected area. The OTP samples had efficient antibacterial property and good biocompatibility. Due to the hydrophilic property, small size and positively charged surface, OTP showed high performance to penetrate the mucus layer, and could eliminate bacteria inside biofilm. The in vivo efficacy of OTP was demonstrated by a pneumonia animal modal, which could inhibit lung infection within 3 d. This work provided a flexible and effective strategy for constructing drug delivery system to treat pneumonia by inhalation, which had broad prospects in the clinical treatment of severe lung infections.(c) 2022 Elsevier Ltd. All rights reserved.