CNS Delivery of Peptides Across the BBB Using the Dual-Artery In Situ Brain Perfusion Model

Methods to Study Drug Uptake at the Blood-Brain Barrier Following Experimental Ischemic Stroke: In Vitro and In Vivo Approaches

Drug permeability across the blood-brain barrier (BBB) is an important concept in the development of therapeutic strategies to treat neurological diseases such as ischemic stroke. These mechanisms can be evaluated in detail using cultured brain microvascular endothelial cells or intact animals subjected to experimental stroke. Here, we describe state-of-the-art approaches to study BBB transport of therapeutics using our in vitro and in vivo approaches. These methodologies allow for precise determination of transporter kinetic properties for currently marketed therapeutics or for new chemical entities that are under development as stroke drugs.

SU-8 based microprobes for simultaneous neural depth recording and drug delivery in the brain

While novel influential concepts in neuroscience bring the focus to local activities generated within a few tens of cubic micrometers in the brain, we are still devoid of appropriate tools to record and manipulate pharmacologically neuronal activity at this fine scale. Here we designed, fabricated and encapsulated microprobes for simultaneous depth recording and drug delivery using exclusively the polymer SU-8 as structural material. A tetrode- and linear-like electrode patterning was combined for the first time with single and double fluidic microchannels for independent drug delivery. The device was tested experimentally using the in vivo anesthetized rat preparation. Both probe types successfully recorded detailed spatiotemporal features of local field potentials and single-cell activity at a resolution never attained before with integrated fluidic probes. Drug delivery was achieved with high spatial and temporal precision in a range from tens of nanoliters to a few microliters, as confirmed histologically. These technological advancements will foster a wide range of neural applications aimed at simultaneous monitoring of brain activity and delivery at a very precise micrometer scale.

Detection of free radicals by isolated perfusion of the rat brain following hemorrhagic stroke: a novel approach to cerebrovascular biomarker research

Blood-borne biomarkers are a mainstay of diagnosis and follow-up in many diseases. For stroke, however, no reliable biomarkers have thus far been identified. To remedy this situation, we investigated the usefulness of a modified in situ isolated brain perfusion (IBP) technique for screening potential biomarker candidates. As a proof of concept, the production of reactive oxygen species (ROS) was estimated in a rat model of experimental intracerebral hemorrhage (ICH). After stereotactic infusion of whole blood into the rat striatum, we initiated IBP without intracranial manipulation or discontinuation of cerebral blood flow. To detect ROS, we employed the salicylate trapping method, which involves the hydroxylation of salicylic acid during oxidative stress into dihydroxybenzoic acid (DHBA), and quantification of the latter in venous eluate by using high-performance liquid chromatography. Venous eluate was collected separately from both injured and healthy hemispheres (n=10). Control groups consisted of sham-injured (n=4) and healthy animals (n=3). In animals subjected to ICH (n=10), 50% more 2,5-DHBA was detected in venous eluate on the injured side than in eluate on the contralateral side. Hemorrhagic hemispheres produced more 2,5-DHBA than hemispheres in sham-injured and healthy animals (72 and 110% more 2,5-DHBA, respectively). Isolated brain perfusion combined with salicylate trapping produced data indicating an elevation in the formation of ROS subsequent to ICH. Our findings suggest that isolated in situ brain perfusion is a promising approach to detecting biomarkers of cerebrovascular pathologic conditions.