Diving into RNAi\nTherapy: An Inhalable Formulation\nBased on Lipid–Polymer Hybrid Systems for Pulmonary Delivery\nof siRNA

Here, a pulmonary formulation based on lipid–polymer\nhybrid\nnanoparticles carrying small interfering RNA (siRNA) was developed\nto realize a RNA interference-based therapy to treat respiratory diseases.\nToward this aim, a new copolymer was synthesized, by functionalization\nof the α,β-poly(<i>N</i>-2-hydroxyethyl)-d,l-aspartamide with 35 mol % of 1,2-bis(3-aminopropylamino)ethane,\n0.4 mol % of fluorescent dye, and 4.5 mol % of poly(lactic-<i>co</i>-glycolic acid). This was used to encapsulate siRNA targeting\nthe green fluorescent protein (siGFP), within a lipid shell made from\n1,2-dipalmitoyl-<i>sn</i>-glycero-3-phosphocholine and 1,2-distearoyl-<i>sn</i>-glycero-phosphoethanolamine-N-(polyethylene glycol)<sub>2000</sub>. siGFP-loaded lipid–polymer hybrid nanoparticles\n(LPHFNPs@siGFP) exhibited colloidal size (∼164 nm), positive\nζ potential, high siRNA encapsulation efficiency (∼99%),\nand a core–shell morphology. They showed high cellular uptake\nand a gene silencing efficiency of ∼50% in human lung cancer\ncells expressing GFP. To address aerodynamic challenges, LPHFNPs@siGFP\nwere spray-dried with trehalose, yielding spherical particles (∼3\nμm) with 80% siRNA encapsulation efficiency, excellent aerosolization\nproperties, and a gene silencing efficiency comparable to the fresh\nLPHFNPs@siGFP sample.