Exploring a mucoacting spray-dried nanoparticle-in-microparticle inhalable formulation for targeted pulmonary delivery of sorafenib in lung cancer therapy

In this study, we developed an inhalable Nano-in-Micro (NiM) system for localized delivery of Sorafenib (Sor) in non-small cell lung cancer (NSCLC) therapy. Sor was encapsulated into mucus-penetrating and folate-targeted polymeric nanoparticles (FA-PPP-NPs@Sor), produced starting from the α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA), functionalised with poly(lactic-co-glycolic acid) (PLGA), and folate-conjugated polyethylene glycol (PEG-FA) FA (DD_PLGA = 3.3 mol %, DD_PEG-FA ≈ 8 chains/molecule). Nanoprecipitation produced 109 nm particles, easy to redisperse, with a DL of 10 wt%, which showed a controlled release of the drug, about 8.4 wt% (pH 7.4) vs. 21.7 wt% (pH 5.5) in 24 h. A selective cytotoxicity towards A549 lung cancer cells via folate receptor-mediated internalization was found, being IC₅₀ = 18 ± 3.2 µM, significantly lower than those found both in 16HBE cells (IC₅₀ = 69 ± 3.1 µM and free Sor (IC₅₀ = 17.7 ± 2.3 µM). The receptor involvement was confirmed by competitive folate blocking, which raised IC₅₀ >100 µM. Wound healing assay performed to evaluate the ability of Sor-loaded nanoparticles to inhibit or reduce cell migration showed 27 % vs. 40 % wound closure at 48 h (NiM vs Sor). The nanoparticles were further incorporated into inhalable microparticles via spray drying (SD), using mannitol, leucine, N-acetylcysteine, and ammonium bicarbonate as functional excipients (yield 63 wt%, EE = 100 wt%, DL = 0.35 wt%). The spray dried NiM_Sor microparticles exhibited a MMAD and a FPF, respectively, of 2.2 µm and 76 %, suitable for deep lung delivery. Furthermore, their storage at r.t. and dissolution in water reconstitutes the nanoparticle dispersion. Rheology tests demonstrated time- and concentration-dependent mucus thinning. Overall, this study presents a promising inhalable platform for targeted lung cancer therapy, combining targeted cytotoxicity, mucus penetration, controlled release, and favourable aerosol properties.