Orchestrating cells on a chip: Employing surface acoustic waves towards the formation of neural networks

Abstract

For the investigation of cell-cell interaction in general and for neural communication and future applications of neural networks, a controllable and well-defined network structure is crucial. We here propose the implementation of an acoustically driven system for tunable and deliberate stimulation and manipulation of cell growth on a chip. This piezoelectric chip allows us to generate a checkerboard-like standing surface acoustic wave pattern coupled to a fluid layer in a microfluidic chamber on top. Such a dynamically induced patterning lattice is shown to allow for the active positioning of the neurons and subsequent guided neurite outgrowth, thus finally overcoming the limitations of static approaches. After thorough characterization of the resulting tunable potential landscape, we successfully demonstrate cell adhesion and even growth of the such positioned cells within the well-defined pressure nodes. We demonstrate neuron growth at predetermined positions and observe a subsequent neurite outgrowth, even being correlated with the artificial potential landscape. For the very delicate and sensitive primary neural cells, this is a change of paradigm! Our experimental findings give us confidence that our hybrid lab-on-a-chip system in the near future will allow researchers to study cell-cell interaction of primary neurons. If scaled to a true network level, it will enable us to control and study how neural networks connect, interact, and communicate.

Large-scale acoustic-driven neuronal patterning and directed outgrowth

“…S2). This observation demonstrates that applying standing SAWs do not compromise the cells' viability, as was also previously shown for other cell types 49,53,68 .…”

“…In the last two decades, researchers have examined the ability of acoustic standing waves to control the spatial distribution of different cells for various applications in a 2D and 3D manner [46][47][48][49][50] . Despite the advantages of using standing acoustic waves for arranging elements, only a few studies have been conducted using this method for organizing neuronal or neuron-like cells [51][52][53][54] . Bouyer and co-authors organized multi-layered 3D constructs of neural progenitor cells (NPCs) derived from human embryonic stem cells within a fibrin hydrogel.…”

“…Brugger and colleagues have demonstrated long-term manipulation for small-scale patterning (230 cells/mm 2 ). They applied the acoustic stimulation for up to 11 hr continuously, affecting both the location and growth 53 . During network formation, neurons transmit information over long distances via their axonal trees.…”

Massively Multiplexed Submicron Particle Patterning in Acoustically Driven Oscillating Nanocavities

“…While deterministic single‐particle trapping has recently been demonstrated for 7–10 µm diameter particles [ 59,79–82 ] and cells [ 54,83,84 ] with acoustic wavelengths on the order of 20–30 µm, this work represents an order of magnitude reduction in particle size and allows a level of control over nanocavity locations (thus trapped particles) that is not possible with SAWs alone. Furthermore, our work improves on recent reports of nanoparticle capture such as nanoparticle aggregates formed using BAWs [ 49 ] and via interference patterns using air cavity waveguides, [ 50 ] by patterning particles at the single‐particle level.…”

Particle Patterning by Ultrasonic Standing Waves in a Rectangular Cavity

“…The ability to trap particles such as cells, microorganisms, and biochemical compounds with the acoustic radiation force of ultrasonic waves is fostering a revolution in biotechnology and analytical chemistry [1,2]. In recent years, there has been a growing interest in developing acoustic devices for trapping and patterning individual cells, particles, and chemical compounds [3][4][5][6][7][8][9][10][11][12][13]. Cell patterning in microwell arrays is becoming a useful tool in single-cell analysis [14], which includes applications in intracellular research, gene and protein content and expression, polymerase chain reaction, cell culture and division, clone formation, differentiation, morphology, lysis, separation, sorting, cytotoxicity and fluorescence screens, and antibody secretion.…”