(191w) Establishing a Toxicity Threshold for Polymeric Nanoparticles in Pulmonary Cells

Lung disease is a major burden on the United States and global community. Diseases such as asthma, chronic obstructive pulmonary disease, pneumonia, and lung cancer are major causes of death and economic loss. In the US alone, 39.5 million people suffer from asthma and 12.7 million from COPD. Respiratory diseases have direct costs of $97.7 billion in hospital stays, medications, and primary doctor visits. Therapeutics by pulmonary administration offer targeted treatment for these illnesses with advantages not present in other routes of administration. Pulmonary administration avoids first-pass metabolism, eliminating distribution to unnecessary tissues and consequent side effects. Certified caregivers and needles are not required to administer the therapeutics, resulting in increasing patient compliance and reducing costs of treatment.

However, current methods of studying particle interactions with the respiratory system utilize in vitro and in vivo animal models, which are difficult to extrapolate into predictions of response in the human respiratory system. Typical preclinical models involve rats, mice, guinea pigs, and nonhuman primates, which have different modes of breathing and species-specific airway geometry, resulting in toxicity thresholds that differ from that of the human respiratory system. There is a need to establish toxicity thresholds in humans for materials commonly used in pulmonary therapeutics. CALU-3 and A549 cell lines were used to mimic the conducting airways and pulmonary airspaces of the human respiratory system, respectively. These human cell lines were used to study the effects of particle exposure and establish toxicity thresholds for polystyrene and poly(lactic-co-glycolic acid) nanoparticles in the main regions of the respiratory system. Culturing conditions of the airway and alveolar epithelial cells were optimized to obtain confluent polarized monolayers of cells. Characterization of cell lines included formation of functional tight junctions, by both florescence microscopy and transepithelial electrical resistance (TEER), and the secretion of mucus and surface proteins.

After exposure, cells were evaluated for effects of particles including viability assays observing mitochondrial activity and integrity of cell membranes, observation of resulting cell morphology, and RNA studies to quantify expression of various proteins including mucus secretion proteins, junctional adhesion molecules, and tight junction proteins. These studies allow us to conclude ideal particle sizes and dose concentrations for effective therapeutics.