Abstract
The ability to manipulate the cellular microenvironment to facilitate cell-cell interactions, cell-ECM interactions, and soluble stimuli is essential to maintain cell/tissue physiological functions. Conventional approaches for tissue engineering utilize biodegradable scaffolds to modulate extracellular microenvironment to promote adhesion, proliferation, and differentiation of cultured cells. Due to the inability to precisely control the spatial location, distribution, and uniformity of cells inside the scaffold, tissue engineering focuses primarily on relatively simple tissues comprised of homogeneous cell types such as skin, cartilage, and cornea, but to date it has been challenging to organize heterogeneous cell types to reconstruct complex tissues, such as liver, kidney and bone. Natural animal tissues contain multiple cell types organized in a unique architecture that facilitates specific physiological roles. Therefore, the appropriate organization and manipulation of multiple cell types to mimic the complex pattern of natural tissue to facilitate cell-cell interactions, cell-ECM interactions, and soluble stimuli are essential to maintain cell/tissue physiological functions and also critical to engineer complex tissue engineering for regenerative medicine applications. Comparing to different cell-patterning techniques, including photolithography, microcontact printing, microfluidic patterning, inkjet printing, and laser-guided direct writing, dielectrophoresis (DEP) offers the capability of active, rapid, and massively-parallel manipulation of large numbers of biological cells, microorganisms, and microparticles in microscale, which is a superior candidate for cell patterning application. Here, we present the design, microfabrication, and implementation of dielectrophoretic cell patterning microfluidic platform. We develop three novel cell patterning electrodes which are capable of manipulating large numbers of cells/microparticles to in-vitro construct complex tissue-mimetic patterns of liver and bone tissue. Each of the three cell pattering techniques reaches about 85% cell patterning resolution. Using this dielectrophoretic cell patterning platform, we develop three novel cell patterning electrodes we demonstrate that 1.) About six thousands of individual hepatocytes and endothelial cells are rapidly organized into alternate radial and pearl-chain shaped cell strings to form a 2mm2 heterogeneous-integrated lobule-mimetic tissue with single cell-patterning resolution. 2.) About three thousands of individual osteoblasts and bone-matrix microparticles can be rapidly micropatterned into a precise arrangement of multiple osteoblasts-assembled concentric rings interlaced in-between the radial pearl-chain-array of hydroxyapatite-encapsulated microparticles, which form a 2 mm2 heterogeneous-integrated osteon-mimetic tissue. 3.) At least one hundred thousand of hepatocytes and endothelial cells are micropatterned into the array of multiple radial hepatic/endothelial cell strings to from the two-centimeter-scale precise lobule-mimetic liver tissue. The tissue-mimetic patterns after dielectrophoretic cell patterning also maintained intimate-cell-cell contact, high cell viability, and fine cell-patterning resolution after culturing three to five days. Extension of this research will permit the engineering of other complex tissues and investigations of tissue architecture with applications in drug screening and physiology/pathophysiology.