The interaction of dendrimer-doxorubicin conjugates with a model pulmonary epithelium and their cosolvent-free, pseudo-solution formulations in pressurized metered-dose inhalers

Abstract

Oral inhalation (OI) of nano-chemotherapeutics holds great potentials in the treatment of lung cancers as it enables direct targeting of drugs to lung tissues, spatial and temporal control of drug release, and decrease in drug-associated systemic and local lung toxicity. Therefore, the design of chemistry of the nanocarriers and their OI formulations for chemotherapeutics delivery to the peripheral lungs and extrapulmonary tissues of relevance such as lymph nodes, may thus afford new opportunities for treating such relevant diseases. In this work we investigated the effect of polyethylene glycol 1000Da (PEG1000) density and doxorubicin (DOX) payload on the interaction of poly(amidoamine) dendrimer (PAMAM) with an in vitro pulmonary epithelium model (Calu-3). DOX, which was conjugated to the PAMAM through a pH-labile bond, showed a strong time-dependent cell kill against Calu-3 cells due to sustained DOX release. The conjugation of DOX to PEGylated PAMAM dendrimers significantly enhances DOX transport across pulmonary epithelium compared to free drug, with the rate of transport increasing as PEGylation degree increases. Transient interaction of PEGylated dendrimers with cellular junctions of the polarized epithelium as probed by a reduction in transepithelial electrical resistance, faster mucus diffusion, along with reduced cellular internalization compared to the non-PEGylated counterpart promotes transport across the epithelial barrier. A cosolvent free method was developed to formulate PEGylated PAMAM-DOX conjugates in pressurized metered-dose inhalers. The resulting aerosol formulations show a very high final particle fractions (>82%). We further demonstrate that aerodynamic particle size distribution of the nanoconjugates can be tweaked with the addition of a biodegradable lactide-based copolymer, which may help tune lung deposition of PAMAM-DOX conjugates to a specific pulmonary area. The combined results suggest that conjugation to PAMAM dendrimers and their surface modification with PEG1000 can be utilized to modulate the transport of DOX across pulmonary epithelium, and also to easily formulate the conjugates in propellant-based inhalers for pulmonary administration of anticancer therapeutics.

Keywords: Doxorubicin; Lung cancer; Polyamidoamine dendrimer (PAMAM); Pressurized metered-dose inhalers (pMDIs); Pulmonary epithelium; Transepithelial transport.