Chemical Targeting of Specific Cell Types in Living Brain Tissue

This thesis details our early efforts towards the discovery of polymeric and macromolecular platforms for the targeted delivery of sensors and actuators to specific cell types in the living brain tissue. Chapter 1 of this thesis discusses the small molecule tropane tag chosen as a homing ligand and the dopamine transporter (DAT) chosen as a cellular target, as well as the synthesis of new tropane-based molecular tags for evaluation in cultured human DAT (hDAT)-expressing cells and targeting in brain tissue. Chapter 2 discusses the results obtained from evaluation of the new tropane tags in hDAT-expressing and hNET-exressing cells, including early results from the first example of a DAT-specific voltage sensing dye. In Chapter 3, we discuss the principles governing molecular targeting of probes in the living brain tissue. Part I of Chapter 3 gives important background necessary for understanding some of the complexities involved in targeting chemical probes to specific sites in living brain tissue. Part II of Chapter 3 discusses early results obtained from targeting of our tropane tags in living brain tissue. We provide, perhaps, the first example of a binding-site barrier effect in healthy tissue and demonstrate successful delivery of a moderate-sized protein, neutravidin, to dopaminergic axons. Chapter 3 also discusses preliminary results demonstrating the behavior of our small molecule tag and tagged quantum dot construct in the living mouse brain. Studies of our tagged polymers in cultured cells and our work thus far in the brain suggest which polymers may be most effective as delivery platforms for chemical targeting to specific cell types in living brain tissue.