Abstract
Spatial patterning of cells is of great importance in tissue engineering and biotechnology, as it enables the creation of histoarchitectures of cells and cell aggregates for in vitro high throughput toxicological and therapeutic studies within 3-dimensional environments. Using dielectrophoresis, homogeneous cells suspended in polyethylene glycol diacrylate polymer solution were patterned with repulsive dielectrophoretic forces, generating cell aggregates within a microarray formatted dielectrophoretic system. 2,2-Dimethoxy-2-phenylacetophenone photoinitiator, at low concentrations, initiated PEG-diacrylate crosslinking through a uniform near-UV (peak = 350nm) irradiation of the micro-system within a compact, purpose built portable UV light-box for dielectrophoresis experimentation. The rate of induced cell aggregation over 5 minutes was observed to decrease with increasing PEG-diacrylate polymer concentration, while hydrogel water content remained high(>70%) at PEG-diacrylate concentrations up to 30%. These optimised conditions for rapid dielectrophoretic cell patterning low UV exposure times within the dedicated system and ease of hydrogel peelability were applied to yeast and human leukaemia and cervical cancer cell aggregates which showed 90% cell viability after one week which is significantly better than those published in previous studies. Drug testing study using vinblastine chemo-therapeutic agent showed that the optimised system of representing cells in 3D showed different IC50 graphs compared to results obtained from cells in 2D monolayer indicating the effect of cell-cell interactions. It was noted that the results obtained from monolayers and aggregates were widely apart for all concentrations at all time points studied. Compared to constructing aggregates formed spontaneously or by culturing them on treated surfaces, our system represents a structure more like the original tissue in terms of having a polymer surrounding cells, which serves as a barrier that can represent blood (growth medium with dissolved drug) and extracellular matrix (hydrogel). This work demonstrates the use of this optimised system in cell, drug and tissue engineering studies; the system is easy to use, mimic cells in their natural tissue and it maintain high cell survival.