This increased attention can be attributed to their distinct physical and chemical properties, including a high ratio of surface area to volume, luminescent properties, unique surface characteristics, and biological activities.

ZnO nanoparticles have many possible applications including anti-bacterial and anti-fungal, anti-tumour, anti-inflammation, skin care, bioimaging and food packaging. This wide variety of application is possible due to their unique physicochemical properties, yet mechanisms behind these effects are still not well understood.

Various studies have been conducted to assess the toxicity and biosafety of ZnO nanoparticles. One study evaluated the cytotoxicity and genotoxicity of mycosynthesized ZnO nanoparticles on human lymphocyte cells, finding significant toxicity at high treatment doses (doses of 500 µg/mL and above). Other studies examined the oral acute toxicity of ZnO nanoparticles in rats, revealing minimal acute toxicity but noticeable effects on liver metabolism. Additionally, investigations into the interaction between ZnO nanoparticles and food matrices showed low oral toxicity in rats. Long-term exposure to unmodified ZnO nanoparticles caused hepatic and renal function impairment, reproductive toxicity, anaemia, antioxidant system imbalance, lipid metabolism disorder and hyperlipidaemia through oxidative injury in mice [1, 2].

It is important to emphasize that factors such as dose, size, and exposure time influence the bio-toxicity of ZnO nanoparticles. Consequently, caution should be exercised when using these nanoparticles in food additives and skincare products that directly come into contact with the human body, requiring strict control of usage parameters.

While there have been numerous studies on their toxicity, there is still a lack of long-term effects data. The acute toxicity of ZnO nanoparticles appears to be low based on current reports, but the focus should shift towards assessing chronic toxicity and long-term effects, which are more crucial. Additionally, the genetic toxicity evaluation of ZnO nanoparticles should be strengthened as it directly relates to the health of future generations. To enhance material biosafety, modifications such as altering the surface reactive properties can be explored to improve biocompatibility and minimize adverse effects.

Currently, the understanding of the mechanisms that involves ZnO nanoparticles is not comprehensive enough, and research results often vary or contradict each other across different models. The lack of essential nanotoxicity information and consensus among researchers regarding evaluation indices hampers effective regulation and control. Therefore, there is a need for standardized experimental protocols to study toxicity mechanisms, as well as guidance and standardization in nanotoxicity evaluation, encompassing areas such as cytotoxicity, in vivo toxicity, and genetic toxicity.