Green synthesis of TiO₂ nanoparticles using cyanobacterial phycobiliproteins for antibacterial and antioxidant toothpaste applications

Oral diseases such as dental caries are highly prevalent and are strongly associated with microbial biofilms and oxidative stress. This study investigated the green synthesis of titanium dioxide nanoparticles (TiO₂ nanoparticles) using cyanobacterial phycobiliproteins, including phycocyanin (PC) and phycoerythrin (PE), extracted from Trichormus sp. 121B and Desmonostoc alborizicum. Spectrophotometric analysis confirmed nanoparticle formation, while Fourier Transform Infrared (FTIR) analysis indicated the presence of organic functional groups derived from cyanobacterial pigments. Dynamic Light Scattering (DLS) analysis showed an average nanoparticle size of approximately 122 nm. The toothpaste formulation containing 2% TiO₂ nanoparticles exhibited the highest antibacterial activity, with inhibition zones of 12.33 ± 0.33 mm against S. mutans, 15.33 ± 0.33 mm against Staphylococcus aureus, and 11.33 ± 0.33 mm against Escherichia coli, compared to no activity in the control group. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values against S. mutans were reduced by 75% and 80%, respectively. Total phenolic content and antioxidant activity were also better preserved, with approximately 22% higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and 17% higher Fourier Transform Infrared (FTIR) values compared to the control. Sensory evaluation confirmed strong acceptability of the 2% nanoparticle toothpaste formulation. Overall, incorporation of 2% biosynthesized TiO₂ nanoparticles significantly enhanced antibacterial efficacy, antioxidant preservation, formulation stability, and sensory properties, demonstrating a clear dose-dependent improvement across all evaluated parameters.