Biodegradability

In order to assess biodegradability each component comprising the laminate was examined separately first and then the laminate as a whole. The samples were immersed in a solution comprised of: 5 ml primary medium (DMEM supplemented with 10% FBS, 100 Uml-1 penicillin (PEN), 100 pg ml-1 streptomycin (SP), 50 pg ml-1 gentamicin sulfate (GS) and 250 ng ml-1 fungizone (FZ)) and left at 37 °C. Once the desired degradation time had passed they were washed with DDI water and left to dry in a vacuum and their weight was measured in order to determine the weight loss in the degradation medium. The hydrogel-RGD material degraded completely after 3 weeks; the PLLA fiber mat lost less than 10% of its mass after 4 weeks; the laminate without HA lost 18%, 29%, 34% and 44% of its mass after the 1st, 2nd, 3rd, and 4th week, respectively; while the laminate containing HA had a mass loss of 15%, 17%, 34% and 34% after the 1st, 2nd, 3rd, and 4th week [54]. It is seen that including HA in the hydrogel resulted in a slower degradation rate, and particularly during the last week of immersion (week 4) no mass loss was observed.

Similar to the mechanical properties, the degradable properties of each laminate component (and hence overall degradation of the laminate) can be tuned through their fabrication process. Particularly increasing the amount of lactide in the PLEOF hydrogel increases the density of the ester bonds and hence its degradation. It has been observed that PLEOF containing lactide fractions of 10%, 20%, 30% and 40% resulted in a mass loss of 19%, 23%, 70% and 86% over a four-week period. The ability of tuning the hydrogel degradation rate to such extents can allow for the fabrication of laminates with a bimodal degradation rate, since the hydrogel could degrade much faster than the PLLA fiber network. As a result cell migration can occur in place of the hydrogel, while the PLLA fibers provide the necessary structural and mechanical support until sufficient tissue has been regenerated.

 
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