Biodegradable hydrogel scaffolds for tissue engineering: Development and analysis

Hydrogels are popular materials for biological applications since they exhibit properties similar to natural soft tissue and have similar mass transport. Another appealing aspect is the range of tunability available to adjust properties for a given application. Biodegradable hydrogels provide an added advantage in that they degrade in the physiological environment thereby avoiding the need for a secondary surgery and concerns of long term implant stability. In this work, we investigated poly(beta-amino ester) (PBAE) biodegradable hydrogel systems in order to determine their potential for regenerating damaged tissue. The properties of individual hydrogel scaffolds were studied and a new processing technique was developed to create composite scaffolds that exhibit controlled pore opening. For this procedure particles of a “fast-degrading” hydrogel system are ground and dispersed into a “slow-degrading” outer hydrogel matrix. For individual samples the degradation rate and compressive moduli were measured in vitro. Hydrogel samples were shown to exhibit degradation profiles ranging from 7 hours to 4 months. Compressive moduli were shown to decrease during degradation. Cell response was measured using MTT cytotoxicity analysis of the degradation products which showed toxic concentrations similar to that of PLGA. Direct cell attachment studies were completed using a live/dead assay and fluorescent imaging. Cells seeded directly onto the hydrogels showed significant viability in the first 24 hours (98%) and slightly lower, but still substantial viability at 48 hours (72%). MicroCT analysis and confocal microscopy were used to observe pore formation in the composite scaffolds.