Controlling cell–cell interactions using surface acoustic waves

Abstract

The interactions between pairs of cells and within multicellular assemblies are critical to many biological processes such as intercellular communication, tissue and organ formation, immunological reactions, and cancer metastasis. The ability to precisely control the position of cells relative to one another and within larger cellular assemblies will enable the investigation and characterization of phenomena not currently accessible by conventional in vitro methods. We present a versatile surface acoustic wave technique that is capable of controlling the intercellular distance and spatial arrangement of cells with micrometer level resolution. This technique is, to our knowledge, among the first of its kind to marry high precision and high throughput into a single extremely versatile and wholly biocompatible technology. We demonstrated the capabilities of the system to precisely control intercellular distance, assemble cells with defined geometries, maintain cellular assemblies in suspension, and translate these suspended assemblies to adherent states, all in a contactless, biocompatible manner. As an example of the power of this system, this technology was used to quantitatively investigate the gap junctional intercellular communication in several homotypic and heterotypic populations by visualizing the transfer of fluorescent dye between cells.cell-cell interaction | intercellular communication | surface acoustic waves | acoustic tweezers | acoustofluidics M ulticellular systems rely on the interaction between cells to coordinate cell signaling and regulate cell functions. Understanding the mechanism and process of cell-cell interaction is critical to many physiological and pathological processes, such as embryogenesis, differentiation, cancer metastasis, immunological interactions, and diabetes (1-3). Despite significant advances in this field, to further understand how cells interact and communicate with each other, a robust, biocompatible method to precisely control the spatial and temporal association of cells and to create defined cellular assemblies is urgently needed (4). Although several methods have been used to pattern cells, limitations still exist for the demonstrated methods including those that make use of optical, electrical, magnetic, hydrodynamic, and contact printing technologies (5-9). Firstly, most of the methods require modification of the cell's native state. The magnetic assembly method, for example, requires cells to be labeled with magnetic probes. Dielectrophoresis typically requires the use of a special medium (e.g., nonconductive) which may lack essential nutrients or have biophysical properties (such as the osmolality) that may adversely affect cell growth or physiology (6). Optical tweezers provide a label-free and contactless approach, but typically require high laser power to manipulate cells, leading to a high risk of cell damage (5). Secondly, the working principles of the existing technologies mostly preclude the combination of high precision and high throughput into a single ...

Three-dimensional manipulation of single cells using surface acoustic waves

“…The manipulation of particles along the x direction can be achieved in a similar way. With the wide tuning range of the relative-phase-angle lag, we can translocate microobjects to any desired location within the entire microfluidic chamber and maintain any desired formation of the trapping array, which results in a significant improvement in manipulation dexterity, compared with our previous work (14). By demonstrating a vertical range from the substrate surface to the ceiling of the microfluidic chamber, our approach can manipulate microparticles within the entire volume of a microfluidic chamber.…”

“…The procedure for device fabrication was described in our previous work (14,15). Details of the experimental setup and the operating procedures are given in SI Text, Experimental Setup and SI Text, Calibration of Vibration Amplitude.…”

“…To explore potential practical applications of this technology, we performed 3D printing of living cells onto a substrate with customized cell patterns using our 3D acoustic tweezers. Our earlier work (14,15) demonstrated that the use of acoustic tweezers had no discernible effect on cell viability, functionality, and gene expression (14,15). When an acoustic field was applied, living single cells were captured into the 3D trapping nodes.…”

“…Finally, the acoustic tweezers platform can be constructed as a single, integrated microdevice without any moving parts or complicated setup procedures. This feature offers additional advantages for ease of use and versatility.Thus far, sound waves have been demonstrated to successfully perform many microscale functions such as the separation, alignment, enrichment, patterning, and transportation of cells and microparticles (12)(13)(14)(15)(16)(17). None of these acoustic approaches, however, has hitherto demonstrated controlled 3D manipulation of single cells.…”

A One-Sided View of Acoustic Traps

“…Standing wave schemes have recently been proposed to accurately manipulate particles in two dimensions using surface [18,19] or bulk acoustic waves [20] with phase or frequency shifts in order to demonstrate capabilities similar to OTs. However, all the aforementioned techniques share the same limitations; e.g., standing waves form multiple equilibrium positions in one or two dimensions, each of which is likely to trap one or various particles at the same time, therefore precluding separability and selectivity at the single particle level with ease [21,22].…”