This brief communication evaluates the cytotoxicity and targeting capability of a dry powder chemotherapeutic. Nano-in-microparticles (NIMs) are a dry powder drug delivery vehicle containing superparamagnetic iron oxide nanoparticles (SPIONs) and either doxorubicin (w/w solids) or fluorescent nanospheres (w/v during formulation; as a drug surrogate) in a lactose matrix. In vitro cytotoxicity was evaluated in A549 adenocarcinoma cells using MTS and LDH assays to assess viability and toxicity after 48 h of NIMs exposure. In vivo magnetic-field-dependent targeting of inhaled NIMs was evaluated in a healthy mouse model. Mice were endotracheally administered fluorescently labeled NIMs either as a dry powder or a liquid aerosol in the presence of an external magnet placed over the left lung. Quantification of fluorescence and iron showed a significant increase in both fluorescence intensity and iron content to the left magnetized lung. In comparison, we observed decreased targeting of fluorescent nanospheres to the left lung from an aerosolized liquid suspension, due to the dissociation of SPIONs and nanoparticles during pulmonary administration. We conclude that dry powder NIMs maintain the therapeutic cytotoxicity of doxorubicin and can be better targeted to specific regions of the lung in the presence of a magnetic field, compared to a liquid suspension.

Significant progress has been made over the last half-century in delivering therapeutics by the pulmonary route. Inhaled therapeutics are administered to humans using metered-dose inhalers, nebulizers, or dry powder inhalers, and each device requires a different formulation strategy for the therapeutic to be successfully delivered into the lung. In recent years, there has been a shift to the use of dry powder inhalers due to advantages in the consistency of the dose delivered, ease of administration, and formulation stability. Numerous preclinical studies, involving small and large animals, have evaluated dry powder drugs, vaccines, and immunotherapeutics delivered by the pulmonary route. These studies used different dry powder delivery devices including nose-only, whole-body, and intratracheal administration systems, each of which works with different aerosolization mechanisms. Unfortunately, these delivery platforms usually lead to variable powder deposition in the respiratory tract of animals. In this review, we will discuss obstacles and variables that affect successful pulmonary delivery and uniform powder deposition in the respiratory tract, such as the type of delivery device, dry powder formulation, and the animal model used. We will conclude by outlining factors that enhance the reproducible deposition of dry powders in the respiratory tract of preclinical animal models and identifying knowledge and technology gaps within the field. We will also outline the important factors necessary for successful translation of studies performed in preclinical models to humans.

Bacille Calmette–Guérin (BCG) is currently the only approved vaccine against tuberculosis (TB) and is administered in over 150 countries worldwide. Despite its widespread use, the vaccine has a variable protective efficacy of 0–80%, with the lowest efficacy rates in tropical regions where TB is most prevalent. This variability is partially due to ubiquitous environmental mycobacteria (EM) found in soil and water sources, with high EM prevalence coinciding with areas of poor vaccine efficacy. In an effort to elucidate the mechanisms underlying EM interference with BCG vaccine efficacy, we exposed mice chronically to Mycobacterium avium (M. avium), a specific EM, by two different routes, the oral and intradermal route, to mimic human exposure. After intradermal BCG immunization in mice exposed to oral M. avium, we saw a significant decrease in the pro-inflammatory cytokine IFN-γ, and an increase in T regulatory cells and the immunosuppressive cytokine IL-10 compared to naïve BCG-vaccinated animals. To circumvent the immunosuppressive effect of oral M. avium exposure, we vaccinated mice by the pulmonary route with BCG. Inhaled BCG immunization rescued IFN-γ levels and increased CD4 and CD8 T cell recruitment into airways in M. avium-presensitized mice. In contrast, intradermal BCG vaccination was ineffective at T cell recruitment into the airway. Pulmonary BCG vaccination proved protective against Mtb infection regardless of previous oral M. avium exposure, compared to intradermal BCG immunization. In conclusion, our data indicate that vaccination against TB by the pulmonary route increases BCG vaccine efficacy by avoiding the immunosuppressive interference generated by chronic oral exposure to EM. This has implications in TB-burdened countries where drug resistance is on the rise and health care options are limited due to economic considerations. A successful vaccine against TB is necessary in these areas as it is both effective and economical. The current vaccine against tuberculosis (TB), BCG, has variable efficacy (0–80%) at protecting against infection. A large body of clinical and experimental evidence implicates host exposure to environmental mycobacteria (EM) as the cause of interference with BCG vaccine-induced immunity. We explore the mechanism by which EM interferes with parenteral immunization and propose oral tolerance as a mechanism for this interference. In addition, we use the pulmonary route to vaccinate EM-exposed hosts, thus ensuring effective BCG immunization and subsequent protection against TB. This work has broad implications in the TB vaccine field as it shows that the vulnerability of the current vaccine, and that of many novel vaccine candidates, may be the route of administration and not necessarily the vaccine itself.