Functionalized Hyaluronic Acid Nanoparticles In The Treatment Of Bacterial Pneumonia

Pneumonia by bacterial infection has been a major global concern,but there are still a number of clinical deficiencies in the use of antibiotics.Oral and intravenous formulations lack pulmonary targeting,which leads to systemic toxicity.Although inhaled formulations provide a good solution to the problem of pulmonary targeting,pulmonary delivery requires overcoming the mucus barrier in the lungs and the biofilm formed by incomplete bacterial clearance further promotes bacterial resistance,resulting in ineffective antibiotics.Hyaluronic acid（HA）,a naturally occurring anionic polysaccharide,specifically targets the CD44 receptor that is overexpressed in the inflammatory state and also has good mucus permeability,making it an ideal material for delivery of antibiotic targeted therapy for pneumonia.In this study,we performed compositional analysis and electron microscopic characterization of lung mucus from patients with severe pneumonia and constructed pneumonia mice by bacterial infection to analyze the pathological changes in lung tissue and protein expression levels,revealing patterns such as decreased p H,increased mucin secretion,reduced mucus pores and increased CD44 receptor expression after the onset of pneumonia.Based on the characteristics of the pneumonia microenvironment and the advantages of HA,two HA-modified functionalized nanoparticles for the delivery of antibiotics for the treatment of bacterial pneumonia were constructed.Polymyxin B（PMB）,a highly virulent antibiotic with low resistance rate,was selected as a model drug in the study,and PMB-HA NPs were prepared using the carboxyl group of HA electrostatically bound to the amino group of PMB for the treatment of drug-resistant pneumonia.Homogeneous particles of-7.3 m V,180 nm were obtained by varying the ratio of HA at n _HA:n _PMBof 6.25:1.Elevated endothelial cell CD44 receptor expression was found by lipopolysaccharide mimicking the infected environment,and PMB-HA NPs specifically bound to endothelial cells in the inflammatory state.Following systemic administration,PMB-HA NPs preferentially aggregated in the lungs of pneumonia-prone mice,suggesting that PMB-HA NPs have excellent pneumonia targeting properties.Unlike chemical modifications,electrostatically self-assembled PMB-HA NPs,HA competed with lipopolysaccharides on the cell wall of Gram-negative bacteria,resulting in the release of PMB,and exhibited the same antibacterial activity as PMB in vitro and in vivo.The modification of HA shielded the positive charge of PMB,reducing the toxicity of PMB to normal tissues,and maintained outstanding biosafety in vivo and in vitro.Finally,acid-responsive nanoparticles with hydrophobic structure-HA-PAE/PMB NPs-were obtained by modifying the hydroxyl group of HA and bonded to hydrophobic material-poly（β-amino ester）（PAE）-by wrapping PMB.In the acidic mucus environment of severe pneumonia,HA-PAE/PMB NPs penetrated rapidly into the lung mucus and achieved partial release of the drug to remove free bacteria from the mucus layer.In the in vitro biofilm model,HA-PAE/PMB NPs penetrated effectively into the deep biofilm and eliminated biofilm infection in severe pneumonia.This research provides new insights into the applicability of functionalised HA for the development of antimicrobial agents and lays the foundation for the application of HA in the treatment of lung diseases.