van Swaay, D. | bioRxiv Science

bioRxiv2021

Nanoscale patterning of in vitro neuronal circuits

Methods for patterning neurons in vitro have gradually improved and are used to investigate questions difficult to address in or ex vivo. Though these techniques guide axons between groups of neurons, multiscale control of neuronal connectivity, from circuits to synapses, is yet to be achieved in vitro. As studying neuronal circuits with synaptic resolution in vivo poses significant challenges, an in vitro alternative could serve as a testbed for in vivo experiments or as a platform for validating biophysical and computational models. In this work we use a combination of electron beam and photolithography to create polydimethylsiloxane (PDMS) structures with features ranging from 150 nanometers to a few millimeters. Leveraging the difference between average axon and dendritic spine diameters, we restrict axon growth while allowing spines to pass through nanochannels to guide synapse formation between small groups of neurons (i.e. nodes). We show this technique can be used to generate large numbers of isolated feed-forward circuits where connections between nodes are restricted to regions connected by nanochannels. Using a genetically encoded calcium indicator in combination with fluorescently tagged post synaptic protein, PSD-95, we demonstrate functional synapses can form in this region. Although more work needs to be done to control connectivity in vitro, we believe this is a significant step in that direction.

neuroscience↗

bioRxiv2017

An organ-on-a-chip approach for investigating root-environment interactions in heterogeneous conditions

Plants adapt their root morphology in response to changing environmental conditions, yet it remains largely unknown to what extent developmental adaptations are based on systemic or cell-autonomous responses. We present the dual-flow-RootChip (dfRootChip), a microfluidic organ-on-a-chip platform for asymmetric perfusion of Arabidopsis roots to investigate root-environment interactions under simulated environmental heterogeneity. Applications range from root guidance, monitoring of physiology and development under asymmetric conditions, tracing molecular uptake and selective drug treatments to local inoculation with microbes. We measured calcium responses in roots treated with biotic and abiotic elicitors and observed elicitor-specific signal propagation across the root from treated to untreated cells. We provide evidence for non-autonomous positive regulation of hair growth across the root upon exposure to unfavourable conditions on the opposite side. Our approach sheds light on lateral coordination of morphological adaptation and facilitates studies on root physiology, signalling and development in heterogeneous environments at the organ level.

plant biology↗