Local delivery of usnic acid loaded Rhamnolipid vesicles by gelatin / tragacanth gum / montmorillonite/ vanillin cryogel scaffold for expression of osteogenic biomarkers and antimicrobial activity

Abstract

Treatment of osteomyelitis as a destructive disease with strong, systemic, and high-dose antibiotics always faces tough challenges and severe side effects. The present study aimed to design dual-purpose cryogel nanocomposite scaffolds with antibacterial and bone regenerative properties. The gelatin/tragacanth gum/montmorillonite/vanillin cryogel scaffold (GTM/V) was prepared and enriched with Usnic acid (UA) encapsulated in Rhamnolipid (RH) biosurfactant nanoparticles as a dispersing agent with antioxidant and antimicrobial properties. The physicochemical properties of drug loaded nanoparticles, mechanical, rheological, and biological properties of the cryogel were evaluated. Biological evaluations, including cell proliferation (by MTT assay), cell attachment (by SEM), osteogenic activity (by Alizarin Red staining and alkaline phosphatase assay), and osteogenic gene expression (by quantitative real-time polymerase chain reaction) were studied using MG-63 cells. The antibiofilm effect of the cryogel was studied on Staphylococcus aureus. The results showed the mechanical profile of UA/RH loaded GTM/V scaffold was 3.08 ± 0.20 MPa compressive strength at 70% strain and the elastic modulus was 19.69 ± 1.57 MPa. Biocompatible UA/RH containing cryogel scaffolds showed osteogenic effect through increasing the ALP activity, and the Alizarin-red staining on days 7 and 14 compared to the control group (P < 0.05). The relative increase in expression of bone repair markers, including COL1A1, BGLAP, and SPP1F were shown by RT-PCR. The scaffold had strong antibacterial effects on S. aureus, with an inhibition zone of 1.40 ± 0.21 cm and antibiofilm activity of 43.76 ± 1.65%. In conclusion, our findings support the application of UA/RH loaded GTM/V scaffold for the treatment of osteomyelitis and bone regeneration.