To sum up

Pros

Connections of flavonoids with metal oxide nanoparticles, mainly zinc oxide, ce-ria, titanium-based, CuO/ZnO, and titanium oxide–gold nanocomposites, resulted in materials of interesting physicochemical and biological properties, including antibacterial, antifungal, antiviral, anticancer, and prospective applications as drug delivery platforms for improved osseointegration in orthopedic implants. Metal oxide nanoparticles, such as zinc oxide, ceria, titanium-based, CuO/ZnO, and titanium oxide–gold, were functionalized with quercetin, EGCG, baicalin, lu-teolin, chrysin, morin, icariin hesperetin 7-rutinoside, flavanone-7-O-glucoside to study their prospective medical applications. The ability of the UV light absorption of zinc oxide nanoparticles indicates their perspective application in antiphotoaging therapy.

Cons

The effects of ZnO-NPs that could be safely applied in the biomedical field have been intensively studied to understand the interplay between their physicochem-ical properties and toxic effects. The safety and toxicity issues of ZnO-NPs have become a field of increased public attention [94,95]. Titanium dioxide is a commonly used food, cosmetic, and drug additive or ingre-dient. Everyday use of nanosize TiO2 raises concerns about safety. There are vari-ous data demonstrating the toxic effects of titania in animal models. An agree-ment on the safety of titania has not yet been reached among researchers [96].