An organic device for stimulation and optical read-out of calcium signalling in primary rat cortical astrocytes

Astroglial ion channels and calcium signaling play a central role in the physiology and pathophysiology of the Central Nervous System. In this context, increasing efforts are needed to generate innovative tools for monitoring astrocytes biochemical or bioelectrical activity in vitro and in vivo. Organic field effect devices have a great potential for generating advanced biomedical tools to enable real-time recording and manipulation of communication signals between neural cells. 1,2,3 We previously reported on transparent Organic Cell Stimulating and Sensing Transistors (O-CSTs) that provide bidirectional stimulation and recording of primary neurons.1,2 The transparency of the device also allows the optical imaging of the modulation of the astroglial Ca2+ signaling bioelectrical activity.4,5 Here we explore O-CST functionality to stimulate, evoke and control astroglial Ca2+ signaling and whole cell conductance in primary cultured astrocytes. We found that primary astroglial cells can adhere, grow and differentiate on the perylene based field-effect transistor. Furthermore, the organic material preserves astrocytes electrophysiological properties. By means of patch-clamp analyses, we explore the effect of the stimulation on the whole-cell conductance of patched astrocytes. We found that the stimulation lead to an exclusive increase in the inward current that could be prevented by the application of Ruthenium Red and RN-1734 prior to stimulation. This finding suggests a contribution of the transient receptor potential (TRP) channels, of which TRPV-4 has been shown in former studies to mediate Ca2+ influx in astrocytes. We show, that the provided O-CST evokes intracellular astrocytic Ca2+ response, which can be determined by calcium imaging. The evoked signal was blocked by Gadolininium(III)-chloride and Ruthenium red, thus underpinning the involvement of TRPV channels. By using Ca2+-free bath saline, we show that the response is due to an influx of external Ca2+. We also explored the cellular volume changes and cell viability after stimulation. Our organic cell stimulating and sensing transistor paves the way to a new generation of devices for stimulation, manipulation and recording of astroglial cells' bioelectrical activity in vitro. [1] Benfenati, V. et al. Nat. Mater. 12, 672-680 (2013) [2] Toffanin, S. et al. J. Mater. Chem. B 1 , 3850-3859 (2013) [3] Ichikawa, M. et al. US20130153884 A1, 17/08/2011 [4] Scemes, E. Giaume, C. Glia. 54, 716-25 (2006) [5]Gee, KR. et al. Cell Calcium. 27, 97-106 (2002) [6] Cold Spring Harb Protoc; doi 10.1101/pdb.top066050