A New Active Cell Culture Material for Controlled Cell Micro-Manipulation

Abstract

Mechanical forces in the cell’s natural environment have a crucial impact on growth and behavior, from single-cell gene expression and cell division to the spatial patterning of complex organ architectures. Few areas of biology can be understood without taking into account how both individual cells and networks of cells sense and transduce physical stresses as part of a tightly-controlled and highly integrated, hierarchical collective. However, the field is currently held back by the limitations of the available methods to apply physiologically relevant stress profiles on cells, particularly with sub-cellular resolution, in controlled in vitro experiments. Here, we present a new active cell culture material that allows highly localized, directional, and reversible deformation of the cell growth substrate, with control at scales ranging from the entire surface to the subcellular, and response times on the order of a few seconds. This material has a hybrid architecture composed of a polymeric array of microstructure actuators that serve as anchorage points for adherent cells, embedded in a temperature-responsive poly(N-isopropylacrylamide) hydrogel layer. By incorporating gold nanorods as a phototransducer component into the hydrogel, we are able to remotely control with focused near-infrared light the localized and highly directional actuation of the supported microstructures over a range of scales down to 10 um, with response times under 5 s. Additionally, the surface cues provided by this hybrid material provide opportunities for controlling the cell attachment and alignment patterns. Thus, by triggering surface deformations at selected locations, we applied uniaxial mechanical stresses directly on defined portions of single cells within a population, with resolution over the cell distortion close to ~3 um, cell strains between 0 and ~45% reached locally in different regions within the same cell, cycling frequencies on the order of ~0.1 Hz, and no losses in cell viability. These capabilities are not matched by any other method, and this versatile material has the potential to bridge the performance gap between the existing single cell micro-manipulation and 2D cell sheet mechanical stimulation techniques.