Development of multilayered cell-hydrogel composites using an acoustic focusing technique.

Multilayered composites, composed of mammalian cells arranged in a hydrogel, have been prepared using an acoustic focusing technique. Acoustic focusing is a simple, nonchemical technique that allows for the fast arrangement of cells in matrices where the control of cell geometry is beneficial. Breast cancer cells (MDA-MB231) were dispersed in a 30 wt % solution of poly(ethylene glycol) diacrylate (PEGDA) of molecular weight 400 at a density of 5 x 10(6) cells/mL of PEGDA solution. An ultrasonic field was used to organize the cells before polymerization of PEGDA. Disk-shaped hydrogel composites, typically 1 cm in diameter and 2-mm thick were prepared based on a PEGDA solution volume of 130 microL. At an acoustic frequency of 2.32 MHz, composites having cells positioned within concentric cylindrical shells interspersed with zones of cell-free hydrogel were produced. The cells were located in annuli approximately 80-microm thick and about 300 microm apart. The structure and viability of the cells within these constructs were studied using a fluorescent LIVE/DEAD assay. The viability of the cells was on the order of 50%. For the conditions used in this study, cell death was primarily attributed to exposure of cells to the PEGDA solution prior to polymerization, rather than adverse effects of polymerization or the sound field itself.

Mechanical and cell viability properties of crosslinked low- and high-molecular weight poly(ethylene glycol) diacrylate blends.

There is a strong need for tissue engineering scaffolds that are mechanically robust, exhibit good biocompatibility, and can be made from readily available materials. To this end, blends of commercially available poly(ethylene glycol) diacrylate (PEGDA) with molecular weights of 400 and 3400 were UV-crosslinked at total polymer concentrations that varied systematically from 20 to 40 wt %. The compressive strength and cell viability were determined for each PEGDA mixture. The compressive modulus of the blends was maximized when the weight percent ratio PEGDA3400/400 was about 40/60, with the compressive strength reaching 1.7 MPa. Cell viability results with a LIVE/DEAD fluorescence assay show an average viability of approximately 80% at a total PEGDA concentration of 20 wt % for all blends. Increasing the total polymer concentration increased the compressive modulus of a polymer, but adversely affected cell viability for all the PEGDA blend compositions. The blend composition affected the mechanical behavior of the discs, where a higher degree of crosslinking was achieved by increasing the concentration of shorter chained PEGDA400, whereas elasticity was gained by incorporating longer chained PEGDA3400 into the blends. These results can be exploited for use in tissue engineering applications, where a mechanically robust scaffold is advantageous.