Biodegradability

The degradation of pure nHCA/PLLA, as well as treated and untreated chitin scaffolds was measured by incubating the samples in phosphate buffer saline (PBS) solution for 1, 2, 3 and 4 weeks at 37 °C. At the completion of each incubation time the scaffolds where rinsed three times with distilled water and dried at 45 °C. The solution was changed every week. For all samples the compressive strength decreased with increasing degradation time, however, the rate and total reduction depended significantly on the scaffold composition. The nHCA/PLLA exhibited the highest continuous decrease throughout the 4 week immersion reaching a value of 0 MPa [34]. The composite with untreated fibers reached a compressive strength of ~2.3 MPa after 4 weeks, hence a ~0.8 MPa decrease from the initial value took place. The treated chitin composite exhibited almost a constant compressive strength during PBS treatment, as only a 0.3 MPa decrease took place after the total immersion period. Treating the fibers resulted in strong chemical bonds between the fiber and matrix, which could withstand the degradation effects. Even after such interface bonds are destroyed by degradation of the high molecular weight PLLA in the matrix to lower molecular weight PLLA, the -OOCR groups in the PLLA can again bind to the treated fibers, rebuilding hence the interface. If the fibers are untreated the bonding between the fiber and matrix relies on molecular forces and hydrogen bonds, which are destroyed by the water molecules in the PBS [34]. Enhancing hence the interface strength allows for the scaffold to retain its mechanical strength for a longer time during degradation.

 
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