Large-scale acoustic-driven neuronal patterning and directed outgrowth

Abstract

Acoustic manipulation is an emerging non-invasive method enabling precise spatial control of cells in their native environment. Applying this method for organizing neurons is invaluable for neural tissue engineering applications. Here, we used surface and bulk standing acoustic waves for large-scale patterning of Dorsal Root Ganglia neurons and PC12 cells forming neuronal cluster networks, organized biomimetically. We showed that by changing parameters such as voltage intensity or cell concentration we were able to affect cluster properties. We examined the effects of acoustic arrangement on cells atop 3D hydrogels for up to 6 days and showed that assembled cells spontaneously grew branches in a directed manner towards adjacent clusters, infiltrating the matrix. These findings have great relevance for tissue engineering applications as well as for mimicking architectures and properties of native tissues. The architecture of the brain and the nervous system is very complex, yet it is well organized 1,2. High-level architectures can be found in the spinal cord 3,4 , retina 5,6 , six-layered cortex 7 , hippocampus 8,9 , cerebellum 10 , and many other neuronal sub-regions. Between these organized sub-regions, specific neuronal networks, consisting of myriad neurons, work together to transfer and process information efficiently and to perform specific tasks that later are translated into various behaviors 2,11,12. Hence, the ability to artificially organize and pattern neurons at specific spatial positions in order to mimic different architectures and properties of neural networks is of great importance. In various fields in neuroscience research such as neural tissue engineering and regenerative medicine 13-16 , brain-machine interface 17-19 , developmental neuroscience 20 , and neuropharmacology 21,22 such controlling ability may be crucial. Indeed, in neural tissue engineering, much effort has been devoted to artificially mimic the highly organized architectures and properties of native tissues. Tang-Schomer and colleagues engineered functional brain-like cortical tissue by assembling donut-shaped layers. Their work offers a model with physiologically relevant features for assessing different brain disorders 23. Qian and colleagues have generated forebrain-, midbrain-, and hypothalamic-specific organoids from human-induced pluripotent stem cells, which were able to recapitulate the key features of these brain regions 24. Current methods for arranging specific cells include selective surface modifications 25,26 , direct bioprinting 27,28 , specific micromolding 29,30 , and the use of different forces such as optical 31 , magnetic 32 , and fluidic forces 33. Although these methods allow successful cell patterning, each technique has its own limitations. For example, bioprinting is costly and time consuming because it is applied sequentially, and its implementation in vivo is limited. In addition, parameters such as shear stress on cells, the material's viscosity, and different droplet sizes can dramatically affect th...

The waves that make the pattern: a review on acoustic manipulation in biomedical research

“…In contrast, to pattern cells within hydrogels or more viscous liquids, BAWs are the preferred option [ 27 ]. Combining the advantages of both, Cohen used SAWs and BAWs to induce different patterns of linear arrangements or concentric rings, respectively [ 31 ]. Low-frequency manipulation by use of Faraday waves has the advantage that patterns can be achieved in larger culture wells without being susceptible to wave attenuation in fluid and that no increase in temperature is observed upon manipulation.…”

“…A very recent study by Cohen et al. [ 31 ] used superimposed SAW and BAW and presented results on two different patterns. SAW was used to assemble cells into line patterns, whereas the latter one resulted in concentric rings.…”

“…Unfortunately, in-depth characterization of materials used with respect to viscosities, viscoelastic properties, and gelation kinetics ​are often lacking and the different values were seldom reported in the literature. Despite the many different setups and applications, a lot of work is restricted to comparable or similar gelling formulations of GelMa [ 48 , 74 , 75 ], fibrin [ 28 , 45 , 73 ], collagen [ 31 , 39 , 70 , 71 , 74 , 76 ], or PEG-derivates [ 32 , 74 , 77 ]. Based on theoretical considerations by taking equation (1) into account, and systematic rheological characterization, it might be possible to define intrinsic formulation parameters at which patterning by acoustic waves is possible.…”

Recent Advances on Stimuli-Responsive Hydrogels Based on Tissue-Derived ECMs and Their Components: Towards Improving Functionality for Tissue Engineering and Controlled Drug Delivery

“…The development of complex microarchitectures with non-linear patterns within ECM-based hydrogels is an ongoing challenge due to the requirements in terms of means for high spatial control. In this regard, acoustophoretic systems have shown the most promising results as demonstrated by the guided migration of cells into specific patterns that follow the pressure fields formed by standing surface and standing bulk acoustic waves [ 103 , 104 ]. In addition to favoring the development of hydrogel constructs with high cellular alignment, acoustophoresis has been used to organize embedded cells within hydrogels into the cylindrical structures needed to guide the fabrication of vascular networks.…”

A neuronal wiring platform through microridges for rationally engineered neural circuits

“…Furthermore, although single-cell resolution could be achieved with extracellular matrix (ECM) protein patterning 23 and poly-l-lysine (PLL) surface patterning, 24 plating thousands of neurons all together and then letting cells randomly attach to predefined adhesion spots (the rest of unattached cells are washed away) often result in a neuronal network with unknown identities of each cell, thus failing to produce a rationally and accurately defined neuronal circuit. Group cell patterning with acoustic waves 25 or magnetic force 26 also suffers from this issue of identity loss.…”