Brain glial interface: Advance materials and devices targeting molecular and functional study of astrocytes

Astrocytes are fundamental for the physiology of the central nervous system. Indeed, astrocytes dysfunction has been observed in many brain pathologies making them an attractive target for innovative therapeutical approaches. Proteins mediating calcium signaling are critically implicated in astrocytic function and dysfunction. However, state-of-the-art tools to study and modulate astroglial functions faced limited spatio-temporal sensitivity, cell selectivity and low throughput. While the use of materials and devices enabling photo- and electrical stimulation, have been shown to modulate neuronal activity, their potential to selectively alter astroglial behaviour have largely been neglected. To address this challenging issue, we use materials and devices to modulate and study astrocytes physiology in vitro. We present a device based on N, N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13), that enables electrical stimulation of astrocytes by evoking increases in intracellular calcium concentrations in primary astrocytes. Pharmacological evidences show that the channels TRPV4 and TRPA1 are critically implicated in the observed effect. Moreover, we show that electrical stimulation promotes also cell swelling. We also explore the potential of graphene-based materials as neural interface by using graphene oxide functionalized with a phospholipid (GO-PL). We demonstrate that GO-PL allows an enhanced adhesion of astrocytes without promoting gliosis, that is not caused by modification of physicochemical properties. Finally, we investigate the effect of infrared neural stimulation (INS) on Ca2+-signaling in vitro and in a validated cell culture model of differentiated astrocytes demonstrating that INS represents a new label-free method to modulate astroglial Ca2+-signaling in vitro. Pharmacology and siRNA experiments, show that INS evoke extracellular Ca2+ influx, mediated by TRPV4 and TRPA1 channels, and Ca2+ release from intracellular stores. Notably, experiments on astrocytes from AQP4-KO-/- showed a delayed response. Collectively, we show the impact of novel technologies for understanding the mechanisms behind astrocytes function as well as the use of this technologies to target astrocyte functioning

Biomimetic graphene for enhanced interaction with the external membrane of astrocytes

Graphene and graphene substrates display huge potential as material interfaces for devices and biomedical tools targeting the modulation or recovery of brain functionality. However, to be considered reliable neural interfaces, graphene-derived substrates should properly interact with astrocytes, favoring their growth and avoiding adverse gliotic reactions. Indeed, astrocytes are the most abundant cells in the human brain and they have a crucial physiological role to maintain its homeostasis and modulate synaptic transmission. In this work, we describe a new strategy based on the chemical modification of graphene oxide (GO) with a synthetic phospholipid (PL) to improve interaction of GO with brain astroglial cells. The PL moieties were grafted on GO sheets through polymeric brushes obtained by atom-transfer radical-polymerization (ATRP) between acryloyl-modified PL and GO nanosheets modified with a bromide initiator. The adhesion of primary rat cortical astrocytes on GO–PL substrates increased by about three times with respect to that on glass substrates coated with standard adhesion agents (i.e. poly-D-lysine, PDL) as well as with respect to that on non-functionalized GO. Moreover, we show that astrocytes seeded on GO–PL did not display significant gliotic reactivity, indicating that the material interface did not cause a detrimental inflammatory reaction when interacting with astroglial cells. Our results indicate that the reported biomimetic approach could be applied to neural prosthesis to improve cell colonization and avoid glial scar formation in brain implants. Additionally, improved adhesion could be extremely relevant in devices targeting neural cell sensing/modulation of physiological activity

An organic transistor architecture for stimulation of calcium signalling in primary rat cortical astrocytes

In this work we report the stimulation of astrocytic calcium signalling using an organic cell sensing and stimulating transistor (O-CST). We demonstrate that astroglial cells can adhere and proliferate on these devices giving us the possibility to stimulate bioelectrical activity in this type of cells. By the use of a microfluorimetric calcium imaging approach we show that our device is able to evoke an increase in intracellular calcium levels. This research opens a new path in the study of glial cells and their bioelectrical activity