Optimization of Lung Surfactant Coating of siRNA Polyplexes for Pulmonary Delivery

Role of Hydrophobic Modification in Spermine-Based Poly(β-amino ester)s for siRNA Delivery and Their Spray-Dried Powders for Inhalation and Improved Storage

After RNAi was first discovered over 20 years ago, siRNA-based therapeutics are finally becoming reality. However, the delivery of siRNA has remained a challenge. In our previous research, we found that spermine-based poly(β-amino ester)s are very promising for siRNA delivery. However, the role of hydrophobic modification in siRNA delivery of spermine-based poly(β-amino ester)s is not fully understood yet. In the current work, we synthesized spermine-based poly(β-amino ester)s with different percentages of oleylamine side chains, named P(SpOABAE). The chemical structures of the polymers were characterized by 1H NMR. The polymers showed efficient siRNA encapsulation determined by SYBR Gold assays. The hydrodynamic diameters of the P(SpOABAE) polyplexes from charge ratio N/P 1 to 20 were 30-100 nm except for aggregation phenomena observed at N/P 3. Morphology of the polyplexes was visualized by atomic force microscopy, and cellular uptake was determined by flow cytometry in H1299 cells, where all the polyplexes showed significantly higher cellular uptake than hyperbranched polyethylenimine (25 kDa). The most hydrophobic P(SpOABAE) polyplexes were able to achieve more than 90% GFP knockdown in H1299/eGFP cells. The fact that gene silencing efficacy increased with hydrophobicity but cellular uptake was affected by both charge and hydrophobic interactions highlights the importance of endosomal escape. For pulmonary administration and improved storage stability, the polyplexes were spray-dried. Results confirmed the maintained siRNA activity after storage for 3 months at room temperature, indicating potential for dry powder inhalation.

Targeting Intracellular Bacteria with Dual Drug-loaded Lactoferrin Nanoparticles

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.

Targeted Molecular Therapeutics for Pulmonary Diseases: Addressing the Need for Precise Drug Delivery

Respiratory diseases are a major concern in public health, impacting a large population worldwide. Despite the availability of therapies that alleviate symptoms, selectively addressing the critical points of pathopathways remains a major challenge. Innovative formulations designed for reaching these targets within the airways, enhanced selectivity, and prolonged therapeutic effects offer promising solutions. To provide insights into the specific medical requirements of chronic respiratory diseases, the initial focus of this chapter is directed on lung physiology, emphasizing the significance of lung barriers. Current treatments involving small molecules and the potential of gene therapy are also discussed. Additionally, we will explore targeting approaches, with a particular emphasis on nanoparticles, comparing targeted and non-targeted formulations for pulmonary administration. Finally, the potential of inhaled sphingolipids in the context of respiratory diseases is briefly discussed, highlighting their promising prospects in the field.

Polyplex designs for improving the stability and safety of RNA therapeutics

Nanoparticle-based delivery systems have contributed to the recent clinical success of RNA therapeutics, including siRNA and mRNA. RNA delivery using polymers has several distinct properties, such as enabling RNA delivery into extra-hepatic organs, modulation of immune responses to RNA, and regulation of intracellular RNA release. However, delivery systems should overcome safety and stability issues to achieve widespread therapeutic applications. Safety concerns include direct damage to cellular components, innate and adaptive immune responses, complement activation, and interaction with surrounding molecules and cells in the blood circulation. The stability of the delivery systems should balance extracellular RNA protection and controlled intracellular RNA release, which requires optimization for each RNA species. Further, polymer designs for improving safety and stability often conflict with each other. This review covers advances in polymer-based approaches to address these issues over several years, focusing on biological understanding and design concepts for delivery systems rather than material chemistry.