(8a) Real-Time Tracking of Biomaterial-Based Nanoparticle Behavior in Biological Barriers

The human body has evolved numerous mechanisms to protect against foreign entities, but these mechanisms can also limit the effectiveness of therapeutic nanoparticles. For example, at mucosal surfaces, drug and gene carriers must overcome both extra- and intra-cellular biological barriers to deliver therapeutic cargoes to their site-of-action. The difficulty of this challenge is exemplified by attempts at aerosolized gene therapy for cystic fibrosis (CF). Although the gene capable of correcting the genetic defect in CF has been known since 1989, no patient has been cured of this devastating disease. The combination of highly viscous and elastic extracellular mucus, a paucity of membrane receptors on the underlying surface epithelium, intracellular trafficking within lysosomes, and limited uptake into the cell nucleus together effectively limit efficient gene transfer by both viral and non-viral carriers in the lungs. An improved understanding of how nanoparticles behave in various biological environments is essential to guide the rational development of improved delivery systems.

We use biophysical methods to characterize the behavior of nanoparticles in biological environments, including high-resolution multiple particle tracking (MPT) and multi-color confocal video microscopy. MPT allows the real time movements of hundreds of individual drug and gene carriers to be analyzed quantitatively, providing insight into transport phenomena that has largely been studied using bulk-average techniques in the past. Confocal microscopy allows the quantitative correlation of particle location with various cellular structures and/or pathways and, thus, provides a means of identifying bottleneck(s) to efficient drug and gene delivery in live cells. These methods enable the characterization and evaluation of polymeric materials that, when formulated into nanoparticles, possess controlled physicochemical properties that dictate their behavior in the different biological environments.

This talk will discuss our recent work using particle tracking microscopy to guide our improvement of novel drug and gene delivery systems. Surprising findings with important implications for carrier design will be discussed, including results related to particle design parameters that allow for: (i) rapid particle transport in human mucus and (ii) particle trafficking via a novel non-degradative pathway in live cells.