Alexey Popov

Mucus-penetrating nanoparticles made with “mucoadhesive” poly(vinyl alcohol)

Nanoparticles that readily penetrate mucosal layers are desirable for a variety of biomedical applications. Nevertheless, most nanoparticles tend to be immobilized in mucus via steric and/or adhesive interactions. Contrary to the established opinion that poly(vinyl alcohol) (PVA) is mucoadhesive, we discovered that coating otherwise mucoadhesive nanoparticles with certain partially hydrolyzed PVAs can aid particle mobility in mucus. We describe two approaches to producing such mucus-penetrating particles (non-covalent modification of pre-formed nanoparticles and emulsification in the presence of PVA) and provide mobility data in human cervicovaginal mucus ex vivo as measured by multiple particle tracking and bulk permeation. When coated with PVAs that are ≥95% hydrolyzed, nanoparticles as small as ~210nm were immobilized in mucus similarly to well-established mucoadhesive controls (P>0.05). However, nanoparticles coated with PVAs that are <95% hydrolyzed penetrated mucus with velocities significantly exceeding those for the mucoadhesive controls (P<0.001) and were mobile in the bulk permeation assay.

Enhanced pulmonary delivery of fluticasone propionate in rodents by mucus-penetrating nanoparticles

Most attempts to achieve sustained drug delivery to pulmonary tissues using nanoparticles have focused on mucoadhesive particles (MAP). However, MAP become trapped in the luminal mucus layer and, as a result, are largely eliminated from the respiratory tract by mucociliary escalator and expiratory clearance, which undermines their sustained release potential. Recent studies have shown that mucus-penetrating particles (MPP) engineered to diffuse through mucus can avoid rapid mucociliary clearance in vivo and persist in the lung longer. Nonetheless, it has not been confirmed that MPP encapsulating small molecules can sustain drug release in the lung longer than MAP of similar size and core composition. As a proof of concept, we encapsulated fluticasone propionate (FP) into poly(lactide)-based MPP and MAP (both ∼ 200 nm diameter, ∼ 30-35% drug loading) and evaluated their pulmonary residence by measuring FP levels in mouse lungs over 24h following intratracheal instillation. Furthermore, we evaluated the duration of action of FP MPP in a rat lung inflammation model compared to that of a non-encapsulated FP control. In rodents, pulmonary delivery of FP formulated as MPP provided a 60% higher local exposure compared to MAP and extended the single dose efficacy by at least 16 h compared to non-encapsulated FP.