PICS: a platform for planar imaging of curved surfaces of brain and other tissue.

Optical imaging of wholemount tissue samples provides greater understanding of structure-function relationships as the architecture of these specimens is generally well preserved. However, difficulties arise when attempting to stitch together images of multiple regions of larger, oddly shaped specimens. These difficulties include (1) maintaining consistent signal-to-noise ratios when the overlying sample surface is uneven, (2) ensuring sample viability when live samples are required, and (3) stabilizing the specimen in a fixed position in a flowing medium without distorting the tissue sample. To address these problems, we designed a simple and cost-efficient device that can be 3D-printed and machined. The design for the device, named the Platform for Planar Imaging of Curved Surfaces (PICS), consists of a sample holder, or "cap" with gaps for fluid flow and a depression for securing the sample in a fixed position without glue or pins, a basket with two arms that move along an external radius to rotate the sample around a central axis, and a customizable platform designed to fit on a commercially available temperature control system for slice electrophysiology. We tested the system using wholemounts of the murine subventricular zone (SVZ), which has a high degree of curvature, to assess sample viability and image quality through cell movement for over an hour for each sample. Using the PICS system, tissues remained viable throughout the imaging sessions, there were no noticeable decreases in the image SNR across an imaging plane, and there was no noticeable displacement of the specimen due to fluid flow.

An enzyme-based electrochemical biosensor probe with sensitivity to detect astrocytic versus glioma uptake of glutamate in real time in vitro.

Glutamate, a major excitatory neurotransmitter in the central nervous system, is essential for regulation of thought, movement, memory, and other higher functions controlled by the brain. Dysregulation of glutamate signaling is associated with severe neuropathological conditions, such as epilepsy, and glioma, a form of brain cancer. Glutamate signals are currently detected by several types of neurochemical probes ranging from microdialysis-based to enzyme-based carbon fiber microsensors. However, an important technology gap exists in the ability to measure glutamate dynamics continuously, and in real time, and from multiple locations in the brain, which limits our ability to further understand the involved spatiotemporal mechanisms of underlying neuropathologies. To overcome this limitation, we developed an enzymatic glutamate microbiosensor, in the form of a ceramic-substrate enabled platinum microelectrode array, that continuously, in real time, measures changes in glutamate concentration from multiple recording sites. In addition, the developed microbiosensor is almost four-fold more sensitive to glutamate than enzymatic sensors previously reported in the literature. Further analysis of glutamate dynamics recorded by our microbiosensor in cultured astrocytes (control condition) and glioma cells (pathological condition) clearly distinguished normal versus impaired glutamate uptake, respectively. These results confirm that the developed glutamate microbiosensor array can become a useful tool in monitoring and understanding glutamate signaling and its regulation in normal and pathological conditions. Furthermore, the developed microbiosensor can be used to measure the effects of potential therapeutic drugs to treat a range of neurological diseases.