Diving into RNAi Therapy: An Inhalable Formulation Based on Lipid-Polymer Hybrid Systems for Pulmonary Delivery of siRNA

Here, a pulmonary formulation based on lipid−polymerhybrid nanoparticles carrying small interfering RNA (siRNA) wasdeveloped to realize a RNA interference-based therapy to treatrespiratory diseases. Toward this aim, a new copolymer was synthesized,by functionalization of the α,β-poly(N-2-hydroxyethyl)-D,L-aspartamidewith 35 mol % of 1,2-bis(3 aminopropylamino)ethane, 0.4 mol % offluorescent dye, and 4.5 mol % of poly(lactic-co-glycolic acid). This wasused to encapsulate siRNA targeting the green fluorescent protein(siGFP), within a lipid shell made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-distearoyl-sn-glycero-phosphoethanolamine-N-(polyethylene glycol)2000. siGFP-loaded lipid−polymer hybrid nano-particles (LPHFNPs@siGFP) exhibited colloidal size (∼164 nm),positive ζ potential, high siRNA encapsulation efficiency (∼99%), and a core−shell morphology. They showed high cellular uptakeand a gene silencing efficiency of ∼50% in human lung cancer cells expressing GFP. To address aerodynamic challenges,LPHFNPs@siGFP were spray-dried with trehalose, yielding spherical particles (∼3 μm) with 80% siRNA encapsulation efficiency,excellent aerosolization properties, and a gene silencing efficiency comparable to the fresh LPHFNPs@siGFP sample.