چكيده لاتين
Presently, the usage of microbial metabolites in the production of advanced biomaterials, such as nanofibers, has been put into perspective as a green and sustainable approach in nanobiotechnology. In the current study, the feasibility of synthesis of nanofibers containing two microbial metabolites, violacein and levan, via electrospinning method was investigated. Levan was cultivated, isolated, and purified from Zymomonas mobilis ATCC 31821 and violacein with Janthinobacterium lividum DSM 1522. A concentration of 5% polyvinyl alcohol as the base polymer was mixed with various concentrations of violacein (1, 2, 3, 4, 6, and 10%) and levan (3, 5, and 7%), and electrospinning was set up. Morphology of the resulting fibers was examined by light and field emission electron microscopies. Violacein and levan release was investigated. Antioxidant activity was assayed using the 2,2-diphenyl-1-picrylhydrazyl reagent, antimicrobial activity against Staphylococcus aureus ATCC 25922 and Alcaligenes faecalis was assayed with the colony count technique, and cytotoxicity activity against normal L-929 and tumor A-375 cells was assayed with methylthiazolyldiphenyl-tetrazolium bromide. Similarly, flow cytometry was also performed to analyze the effect of the fibers on A-375 cancer cell viability using propidium iodide reagent. Results of light microscopy revealed PV1L7 fiber exhibited most homogenous fiber structure with least bead formation. Confirmation of presence of beads in the fiber structure was established by further investigation of fiber structure through field emission electron microscopy. The average nanofiber diameter was determined to be 0.379 ± 0.092 µm. Release of violacein from the fiber matrix was biphasic and consisted of an initial high-rate release in the first 24 hours followed by a slow and sustained release. In total, around 80% of violacein content was released from the fibers within 72 hours. The PL1V4 fiber sample released the highest amount of violacein. The PV1L7 fibers showed an initial rapid reduction in the number of Staphylococcus aureus and Alcaligenes faecalis cells followed by a slower rate of reduction. Staphylococcus aureus was more susceptible to the fibers compared to Alcaligenes faecalis. The antioxidant activity assay also showed that the PL3V6 fibers showed the highest radical scavenging capacity and up to 79% antioxidant capacity. Cytotoxicity against normal L-929 cells during 24 hours, the PV1L7 fibers showed the best performance. However, when it comes to the anticancer effect of the fibers against A-375 cancer cells, the PL3V6 fibers showed the maximum inhibitory capacity with a viability of 17.17%. PV1L7 sample with uniform fiber formation, low cytotoxicity in normal cells, anticancer activity, and proper antioxidant function was subjected to flow cytometry analysis. Flow cytometry analysis after 24 hours indicated that treatment of A-375 cancer cells with this sample, resulted in 45.36% membrane damage and cell viability loss. These findings suggest the potential future use of violacein-levan fibers in biomedical and therapeutic applications.
