Particle dissolution rate controls macrophage response and drug release from mesoporous silica inhalation carriers

Mesoporous silica particles (MSPs) are promising micronized carriers for pulmonary drug delivery, combining excellent aerodynamic properties with the ability to dissolve into nanoparticles in lung fluid, enabling intracellular drug transport. In this study, we evaluated the interactions between three MSPs with distinct dissolution profiles in lung fluid and human macrophage models (primary M1, M2, and dTHP-1 cells). Following 4-hour exposure, all MSPs maintained high mitochondrial activity above the IC50 threshold, regardless of concentration, up to 1 mg/mL. MSPs did not induce TNF-α release, indicating a minimal immunological response. However, in simulated lung fluid, MSPs dissolved into nanoparticles exhibited greater toxicity than their microparticle counterparts. Toxicity correlated with dissolution rate: faster-dissolving particles were more toxic at short exposure times, while all MSPs reached similar toxicity levels after 24 h, independent of medium composition. Albumin, the predominant lung fluid protein, was found to mitigate particle toxicity, enhancing biocompatibility. Drug release studies revealed that faster-dissolving particles produced a rapid but unstable supersaturated drug solution, whereas slower-dissolving particles offered a more sustained release profile, supporting its potential for prolonged pulmonary therapy. The lowest observed adverse effect level (LOAEL) in vitro was determined to be 0.06 mg/mL for all the MSPs. This concentration maintained mitochondrial activity, oxidative stress and cell membrane integrity above 70%. These findings highlight the translational potential of MSPs as dual-scale carriers for targeted pulmonary delivery, combining effective drug release with favorable safety profiles.