Eco-friendly synthesis of betanin-conjugated zinc oxide nanoparticles: antimicrobial efficacy and apoptotic pathway activation in oral cancer cells.

Background: Phytochemical-based synthesis of nanoparticles (NPs) is an eco-friendly approach with various biomedical applications. Betanin, a natural pigment in beetroot, has antioxidant, anti-inflammatory, and antimicrobial properties. When conjugated with zinc oxide nanoparticles (ZnO NPs), these properties are enhanced. This study aimed to synthesize betanin-ZnO nanoparticles (BE-ZnO-NPs) and evaluate their biological potential.

Methods: BE-ZnO-NPs were synthesized and characterized using UV-Visible spectroscopy, FTIR, FE-SEM, HR-TEM, EDX, XRD, DLS, and zeta potential analysis. In silico studies assessed interactions with oral pathogen proteins, and antibacterial activity was tested against Enterococcus faecalis, Candida albicans, Staphylococcus aureus and Streptococcus mutans. Antioxidant potential and cytotoxicity on KB cells were evaluated through scavenging assays, MTT assay, and qRT-PCR.

Results: Betanin synthesized ZnO NPs UV-Vis results showed surface plasmon resonance at 388 nm, and FTIR confirmed betanin role as a capping agent. FE-SEM and TEM revealed particles of 37 nm. EDX confirmed zinc content, and XRD showed a hexagonal structure. Zeta potential was - 3.3 mV, and DLS indicated a size of 38.73 nm. In silico analysis showed strong binding to E. faecalis (- 8.0 Kcal/mol). BE-ZnO-NPs demonstrated antibacterial activity at 100 µg/mL, with inhibition zones of 18 ± 0.14 mm for E. faecalis and 14 ± 0.18 mm for S. mutans. In contrast, BE demonstrated antibacterial activity at 100 µg/mL, with zone of inhibition of 10.6 ± 0.14 mm for E. faecalisand 11.4 ± 0.18 mm for S. mutans.Antioxidant assays revealed dose-dependent scavenging activity. Cytotoxicity showed an IC₅₀ of 24.29 µg/mL, with qRT-PCR indicating apoptosis through the BCL2/BAX/P53 pathway.

Conclusions: BE-ZnO-NPs exhibited significant antibacterial and antioxidant activities and demonstrated the ability to induce apoptosis in oral cancer cells via the BCL-2/BAX/P53 signalling pathway. These findings highlight the potential of BE-ZnO-NPs as promising antimicrobial agents for tooth infections and as therapeutic agents for oral tumour treatment.