Size-based anti-tumoral effect of paclitaxel loaded albumin microparticle dry powders for inhalation to treat metastatic lung cancer in a mouse model.

In this study, we prepared paclitaxel (PTX) loaded bovine serum albumin (BSA) microparticles (MPs) of different sizes (0.5, 1.0, and 3.0 µm) and converted them into dry powders (DPs) of a uniform size (∼5.0 µm) through spray-drying techniques. The aim of preparing different sized PTX-MPs is to investigate the size-based in vivo biodistribution and retention of PTX in the lungs after intratracheal administration. Following the in vitro characterizations, the anti-tumor efficacy of the DPs containing differently sized PTX-BSA-MPs administered through intratracheal insufflation was compared with intravenously administered PTX solution (Taxol). While the fastest drug release was found for the 0.5 µm group, the 1.0 and 3.0 μm groups showed the highest anti-tumor efficiency in vivo. Taken together, our results demonstrate that the initial particle size of the incorporated particles, i.e., MPs, is crucial for the anti-tumor efficacy of DPs administered by inhalation, and the initial particle size should be regarded as one of the key factors in the development and quality control of such preparations.