Treatment of microbial infections is becoming daunting because of widespread antimicrobial resistance. The treatment challenge is further exacerbated by the fact that certain infectious bacteria invade and localize within host cells, protecting the bacteria from antimicrobial treatments and the host’s immune response. To survive in the intracellular niche, such bacteria deploy surface receptors similar to host cell receptors to sequester iron, an essential nutrient for their virulence, from host iron-binding proteins, in particular lactoferrin and transferrin. In this context, we aimed to target lactoferrin receptors expressed by macrophages and bacteria; as such, we prepared and characterized lactoferrin nanoparticles (Lf-NPs) loaded with a dual drug combination of antimicrobial natural alkaloids, berberine or sanguinarine, with vancomycin or imipenem. We observed increased uptake of drug-loaded Lf-NPs by differentiated THP-1 cells with up to 90% proportion of fluorescent cells, which decreased to about 60% in the presence of free lactoferrin, demonstrating the targeting ability of Lf-NPs. The encapsulated antibiotic drug cocktail efficiently cleared intracellular Staphylococcus aureus (Newman strain) compared to the free drug combinations. However, the encapsulated drugs and the free drugs alike exhibited a bacteriostatic effect against the hard-to-treat Mycobacterium abscessus (smooth variant). In conclusion, the results of this study demonstrate the potential of lactoferrin nanoparticles for the targeted delivery of antibiotic drug cocktails for the treatment of intracellular bacteria.

中文翻译：

---

用双载药乳铁蛋白纳米颗粒靶向细胞内细菌

由于广泛的抗菌药物耐药性，微生物感染的治疗变得令人畏惧。由于某些传染性细菌侵入并定位于宿主细胞内，保护细菌免受抗菌治疗和宿主免疫反应的影响，这一事实进一步加剧了治疗挑战。为了在细胞内生存，这些细菌部署与宿主细胞受体类似的表面受体，从宿主铁结合蛋白（特别是乳铁蛋白和转铁蛋白）中螯合铁，铁是其毒力的必需营养素。在这种情况下，我们的目标是针对巨噬细胞和细菌表达的乳铁蛋白受体；因此，我们制备并表征了乳铁蛋白纳米颗粒（Lf-NP），其负载有抗菌天然生物碱、小檗碱或血根碱与万古霉素或亚胺培南的双药物组合。我们观察到分化的 THP-1 细胞对载药 Lf-NP 的摄取增加，其中荧光细胞的比例高达 90%，而在游离乳铁蛋白存在的情况下，该比例下降至约 60%，这证明了 Lf-NP 的靶向能力。与游离药物组合相比，封装的抗生素药物混合物有效地清除了细胞内金黄色葡萄球菌（纽曼菌株）。然而，封装的药物和游离药物都对难以治疗的脓肿分枝杆菌（平滑变体）表现出抑菌作用。总之，本研究的结果证明了乳铁蛋白纳米颗粒在靶向递送抗生素药物混合物以治疗细胞内细菌方面的潜力。