Hypoxia-responsive hybrid nanoparticles loaded with fingolimod and colistin against multidrug-resistant Klebsiella pneumoniae with mature biofilm

Multidrug-resistant <i>Klebsiella pneumoniae</i> (MDR-<i>KP</i>) is characterized by high mortality and risk of nosocomial transmission, and biofilm constitutes the primary challenge in the treatment of its implant-associated and refractory pulmonary infections. Notably, the hypoxic microenvironment and the physical barrier of biofilm leading to the increased tolerance of the bacteria to antibiotics. Herein, a hypoxia-responsive hybrid nanoparticle (CHLip@FLD/COL) loaded separately with anti-biofilm candidate fingolimod (FLD) and antibiotic colistin (COL) is achieved targeting antibacterial efficacy against MDR-<i>KP in vitro</i> and <i>in vivo</i>. CHLip@FLD/COL is composed of hybridizing hypoxia-responsive lipids (HLipid) and lipid A targeting materials DSPE-mPEG-COL. HLipid is synthesized by hexadecanedioic acid esterified with nitroimidazole, while DSPE-mPEG is coupling with vector COL via amide reaction. The relative level of extracellular polymeric substances and the NIR-IIb sO₂ images of the infection site are used as indicators to establish mature biofilm models. CHLip@FLD/COL readily releases FLD and COL in hypoxic conditions, and its MIC against MDR-<i>KP</i> is only one-sixteenth of that when COL is used alone <i>in vitro</i>. The nanoparticle exhibits bacterial targeting ability and antibacterial effect in the pulmonary infection and biofilm infection mice models. Bacterial loads eliminated by 4 Log₁₀ CFU and 2 Log₁₀ CFU, respectively. The strategy provides a valuable reference for the treatment of refractory infections caused by MDR-<i>KP</i>.