Silk fibroin-copper nanoparticles conglomerated polyurethane fibers incorporating calcium carbonate for enhanced fluid retention, antibacterial efficacy and promotion of cell growth

This work blended calcite crystals with polyurethane solution and fabricated into micro/nanofibers by electrospinning. Subsequently, these fibers were hydrothermally coated using silk fibroin and deposited with copper (Cu) nanoparticles (NPs). The morphology of fibers was smooth, and the diameter increased upon incorporation of CaCO3 from 1.56 +/- 1.07 mu m to 3.35 +/- 0.8 mu m. Adding SF and Cu increased the fiber diameter, and partial or complete masking of fibrous morphology occurred with higher concentrations. The contact angle declined from 105.3 +/- 0.1 degrees to 12.1 +/- 0.1 degrees in the scaffold with SF and Cu NPs, indicating hydrophilicity. The hydrothermally modified scaffolds showed multi-step decomposition temperature with improved thermal stability compared to pristine samples. The tensile strength of PU micro/nanofibers increased from 158.5 +/- 0.5 MPa to 200.06 +/- 0.2 MPa, and the enzymatic degradation of 46.6 +/- 0.4% after 120 days was seen upon adding SF. The antibacterial activity of fibers against Escherichia coli (20.7 +/- 0.16 mm) and Staphylococcus aureus (20.5 +/- 0.4 mm) demonstrated significant antibacterial activity. The growth curve studies and biofilm inhibition tests from OD measurements showed self-inducing antibacterial activity from the hydrothermal deposition of Cu NPs. The 3T3 L1 and NIH 3T3 cells attached firmly and proliferated well on scaffolds with SF and Cu NPs. The measured cell viability was >300% and approximate to 200% in all composite scaffolds.