Hybrid cell adhesive material for instant dielectrophoretic cell trapping and long-term cell function assessment

Fibronectin in Layer-by-Layer Assembled Films Switches Tumor Cells between 2D and 3D Morphology

Tumor cells showing a 3D morphology and in coculture with endothelial cells are a valuable in vitro model for studying cell-cell interactions and for the development of pharmaceuticals. Here, we found that HepG2 cells, unlike endothelial cells, show differences in adhesion to fibronectin alone, or in combination with poly(allylamine hydrochloride). This response allowed us to engineer micropatterned heterotypic cultures of the two cell types using microfluidics to pattern cell adhesion. The resulting cocultures exhibit spatially encoded and physiologically relevant cell function. Further, we found that the protrusive, migratory and 3D morphological responses of HepG2 are synergistically modulated by the constituents of the hybrid extracellular matrix. Treating the hybrid material with the cross-linking enzyme transglutaminase inhibited 3D morphogenesis of tumor cells. Our results extend previous work on the role of fibronectin in layer-by-layer assembled films, and demonstrate that cell-specific differences in adhesion to fibronectin can be used to engineer tumor cell cocultures.

Microfluidic cell trap array for controlled positioning of single cells on adhesive micropatterns

Adhesive micropattern arrays permit the continuous monitoring and systematic study of the behavior of spatially confined cells of well-defined shape and size in ordered configurations. This technique has contributed to defining mechanisms that control cell polarity and cell functions, including proliferation, apoptosis, differentiation and migration in two-dimensional cell culture systems. These micropattern studies often involve isolating a single cell on one adhesive protein micropattern using random seeding methods. Random seeding has been successful for isolated and, to a lesser degree, paired patterns, where two patterns are placed in close proximity. Using this method, we found that the probability of obtaining one cell per pattern decreases significantly as the number of micropatterns in a cluster increases, from 16% for paired micropatterns to 0.3% for clusters of 6 micropatterns. This work presents a simple yet effective platform based on a microfludic sieve-like trap array to exert precise control over the positioning of single cells on micropatterns. We observed a 4-fold improvement over random seeding in the efficiency of placing a pair of single cells on paired micropattern and a 40-fold improvement for 6-pattern clusters. The controlled nature of this platform can also allow the juxtaposition of two different cell populations through a simple modification in the trap arrangement. With excellent control of the identity, number and position of neighbouring cells, this cell-positioning platform provides a unique opportunity for the extension of two-dimensional micropattern studies beyond paired micropatterns to organizations containing many cells or different cell types.

Dielectrophoretic cell capture on polyester membranes

A new system for dielectrophoretic cell capture on permeable polyester membranes is presented. Conventional photolithographic techniques were used to fabricate gold microelectrodes on a polyester membrane. The characterization of the microelectrodes showed that there were no differences regarding roughness, permeability, and hydrophilicity of the membrane before and after processing. Finally, dielectrophoretic cell capture and viability in a microfluidic device was demonstrated on the patterned membrane. These membranes could ultimately be combined with multilayer microfluidic devices to form a powerful tool for studies of cell-cell interactions in coculture, whereby spatial separation of different cell types and/or microenvironments are required.