Probing microfluidic devices using drug loaded nanocrystals in breast cancer studies
Drug carrier development is a financially taxing process. There are a plethora of ongoing studies in academia and industry aimed towards understanding and solving problems within every stage involved in drug discovery, design, and testing starting from the bench top in vitro continuing onwards to in vivo animal models and finally, concluding with FDA approved clinical trials. This dissertation belongs to the body of knowledge aimed at facilitating a smoother transition of drug development from in vitro to in vivo. Specifically, in vitro to in vivo drug carrier transition studies are plagued with a unique problem which often results in the undue desertion or abandonment of a particular drug or drug carrier. In vitro development and testing of drug carriers, though foundational and necessary prior to all other advances in drug formulations, are traditionally conducted under static, homogenous, monolayered conditions. Drug formulations and carriers developed under these conditions often and understandably exhibit different behavior when transitioned into in vivo animal models due to the strikingly different test environments between in vitro and in vivo testing. Recognizing the importance of canonical in vitro studies and the need to bridge the knowledge gap between benchtop development and animal model performance, microfluidic devices of different architectures, morphologies, and make-up have emerged as a viable and useful intermediary step; linking in vitro to in vivo studies as a means to facilitate smoother and more successful transitions for drug carrier development studies. The microfluidic devices chosen differ in the architectural construction of their chambers, they were selected to help address a variety of pressing questions regarding drug carrier performance under physiological flow while subjected to shear and tensile stresses, complex architectures, and in the presence of a multi-cellular environment. Due to the complexity of addressing multifaceted cellular research questions, a set of specialized devices were required to begin teasing apart the impact these various factors have on drug carrier performance. To fully extract enough information from the microfluidic devices chosen, a consistent drug carrier or drug delivery platform was needed which could be tracked easily through the thick polymer gels comprising the microfluidic devices, would not stick to the polymer surfaces of the devices, and could be tested before and after flow using a variety of rigorous chemical analytics techniques. With this criterion in mind, idealized co-culture, microvascular networks, and linear channel devices were studied using in-house synthesized nanocrystals as a model drug delivery probe within this collection of diverse microfluidic devices. The nanocrystals were a unique design and therefore required extensive chemical characterization and validation prior to their infusion through the microfluidic devices. A major portion of this dissertation will focus on the description of their synthesis and methods utilized for their processing and analyses necessary for their validation and use within the mammalian cell seeded microfluidic devices chosen. A select few nanocrystalline constructs containing different targeting ligands and polymer coatings were culled from a library of potential biologically decorated nanocrystalline constructs for drug performance studies subjected to flow, in the presence of mammalian cells, within the microfluidic devices. These studies were intended to tighten the link between their studied performance in vitro and their future performance in vivo. The results from these microfluidic studies reported here and in published work provide a precedent for other researchers working with various drug delivery carriers to utilize as-is and build upon to obtain seamless and guided transitions from in vitro experiments to their counterpart, in vivo.