| An improved understanding of mucus properties and particle physiochemical properties that govern efficient transport is critical to the design of drug and gene carriers in the lungs, nose, gastrointestinal tract, and reproductive tract. Mucus in the lungs of cystic fibrosis (CF) patients forms a particularly formidable transport barrier due to increased concentrations of highly-branched mucin glycoproteins, DNA, alginate, and lipopolysaccharides that form a dense mesh-like network that traps or adheres to nanoparticle gene carriers targeted at the underlying cell surface.; To develop a better understanding of the relationship between the mechanical properties of CF sputum and the transport rates of nanoparticle gene carriers, the rheological properties of CF sputum samples were correlated with the transport rates of 100--500 nm particles, which are the approximate size of the majority of gene carriers. Using high resolution multiple particle tracking to quantify the transport rates of hundreds of individual model gene carriers, we discovered that particle transport in CF sputum is highly heterogeneous with a small fraction of particles that move many-fold faster than the average ("outliers"). These outliers are important since only a small fraction of inhaled particles may need to cross mucus to treat CF.; The effect of mucolytic agents, which alter the mechanical properties of CF sputum and promote more rapid mucosal clearance, on the rate of particle transport was correlated with the mechanical properties of treated CF sputum samples. Both N acetylcysteine (NAC) and recombinant human deoxyribonuclease (rhDNase) reduced sputum mechanical properties; however, only NAC increased the average rate of particle transport and the percentage of "outlier" particles, which were nearly eliminated in sputum treated with rhDNase.; Sputum is difficult to obtain, especially in high quantities and with reproducible properties; thus, we developed synthetic mucus that accurately mimics the mechanical and nanoparticle transport properties of CF sputum. In this process, we determined the effects of the various constituents, including mucin, surfactants, and high and low molecular weight DNA, on the mechanical and nanoparticle transport properties of CF sputum samples.; After thoroughly characterizing the mechanical properties of CF sputum and synthetic mucus samples, we developed novel polymeric gene delivery systems that could more rapidly traverse mucosal barriers. The time-dependent transport rates of gene carriers were correlated with their adhesivity with mucus, stability in mucus, and with the uptake and DNA delivery efficiencies in mucus-covered lung and gastrointestinal cells. We discovered that surface modification of gene carriers with poly (ethylene glycol) or DNA made them less adhesive with mucus, which resulted in 10--1000-fold faster mucus transport. Gene carriers were functionalized with cell-specific ligands, which resulted in more efficient DNA delivery to mucus-covered cells than cationic liposomes (gold standards for DNA delivery). |
