(570f) Microfluidic Probes for Tracer Studies of Convective Transport in the Brain

We have designed a microfluidic probe to perform tracer studies with the goal of characterizing the convective transport during infusions into the brain. These probes consist of two parylene channels with cross-sectional areas of 10 by 25 microns on a silicon substrate with a cross-sectional area of 100 by 100 microns. We infused a bolus (0.5 microliters) of passive tracer into the caudate of adult rats followed by infusion of an artificial cerebral spinal fluid (3 microliters). The tracers used were dextran (10 kDa) and polystyrene nanoparticles (20 and 100 nm). The distribution of the tracers was used to determine differences in hydraulic permeability between white matter, gray matter, and perivascular spaces. We also examine whether tissue dilation during infusion can increase the pore size of the extracellular matrix to allow for enhanced penetration of nanoparticles.