Dual tobramycin and docosahexaenoic acid loaded nanoemulsions combating Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa (P. aeruginosa) typically forms biofilms in vivo, which exhibit high resistance and complicate eradication efforts. Additionally, persistent infiammation and excessive oxidative stress can lead to severe lung dysfunction, facilitating bacterial colonization and infection. Herein, we prepared oil-in-water (O/W) nanoemulsions (TD-alpha T NEs) by using PEG5k-block-PCL5k and alpha-tocopherol to encapsulate tobramycin (TOB). To enhance TOB's drug load, a hydrophobic ion pair (TDIP) composed of TOB and docosahexaenoic acid (DHA) was pre-prepared. TD-alpha T NEs was not only easily prepared and aerosolized, but stable in both physics and chemistry. The negatively charged TD-alpha T NEs facilitated penetration through mucus, reaching infection sites. Subsequently, TD-alpha T NEs permeated biofilms due to their small size and released drugs via lipase-triggered carrier dissociation, aiding in eradicating internal bacteria within biofilms (with a 16-fold reduction in CFU vs. free TOB group). TD alpha T NEs simultaneously exerted superior anti-infiammatory effects, reducing levels of pro-infiammatory cytokines (NO, IL-6, IL-8, and TNF-alpha) while increasing the level of anti-infiammatory cytokine (IL-10). It was achieved through the upregulation of PPAR-gamma and downregulation of NF-kappa B signaling, thus mitigating the lung damage. In addition, TD-alpha T NEs demonstrated strong antioxidant activity, alleviating the oxidative stress induced by P. aeruginosa. Notably, when administered via inhalation, TD-alpha T NEs significantly reduced the lung bacterial burden, lung infiammation, and oxidative stress in vivo compared to TOB solution. TD-alpha T NEs could prove beneficial in treating chronic pulmonary infections induced by P. aeruginosa through a comprehensive strategy, specifically enhancing biofilm eradication, reducing infiammation, and alleviating oxidative stress.