Green biosynthesis of titanium dioxide quantum dots using watermelon peel waste: antimicrobial, antioxidant, and anticancer activities

In this study, watermelon peel waste was used for biosynthesis of titanium dioxide quantum dots (TiO(2)Qds) through green and ecofriendly method for the first time. The biosynthesized TiO(2)Qds were fully characterized using UV-visible, FTIR, XRD, SEM, EDX, mapping, TEM, and TGA. The characterization of TiO(2)Qds revealed that the synthesized TiO(2)Qds is a polycrystalline crystal structure with an average particle size of 7 nm. The antimicrobial results revealed that TiO(2)Qds exhibited promising antimicrobial activity against Bacillus subtilis, Escherichia coli, Cryptococcus neoformans, Candida albicans, Aspergillus niger, and A. fumigatus where minimum inhibitory concentrations (MICs) were 15.62, 62.5, 7.81, 7.81, 31.25, and 1.95 mu g/mL, respectively. Moreover, TiO(2)Qds have a strong antioxidant activity where IC50 was 31 mu g/mL using DPPH method. Furthermore, TiO(2)Qds have potential anticancer activity against MCF7 cancerous cell line where IC50 was 114 mu g/mL, and inhibition percentages at 1000 and 500 mu g/mL were 99 and 93%, respectively. In conclusion, the biosynthesized TiO(2)Qds using watermelon peel waste have antimicrobial, antioxidant, and anticancer activities with high biocompatibility.