Zinc Oxide Nanoparticles: Therapeutic Benefits and Toxicological Hazards

What is it about?

Despite the widespread application of zinc oxide nanoparticles in biomedicine, their use is still a controversial issue. Zinc oxide nanoparticles were reported to have therapeutic benefits. However, they were reported to have toxicological hazards as well. Several studies reported the antibacterial, anticancer, antioxidant, and immunomodulatory effects of zinc oxide nanoparticles. Additionally, zinc oxide nanoparticles were used in sunscreens. Furthermore, the ability to use zinc oxide nanoparticles as an adjuvant treatment to alleviate the toxic effects of chemotherapeutic drugs has been reported. However, zinc oxide nanoparticles were shown to induce toxic effects in different body organs and systems. The affected organs included liver, spleen, kidney, stomach, pancreas, heart and lung. In addition, zinc oxide nanoparticles were reported to adversely affect the neurological system, lymphatic system, hematological indices, sex hormones levels, and fetal development. The toxic effects of zinc oxide nanoparticles were based on their concentration, their dose, the route of their administration, and the time of exposure to those particles. Thus, it is crucial to assess their efficacy and safety to determine their toxicological risks and therapeutic benefits.

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Why is it important?

Nanoparticles may be natural or synthetic. Synthetic nanoparticles are classified into several types; such as metal nanoparticles (e.x. gold and silver nanoparticles), metal oxide nanoparticles (e.x. zinc oxide), carbon nanoparticles, and quantum dots (e.x. cadmium selenide). Synthetic nanoparticles have physicochemical features and special reactivity, which are attributed to their small size, and to their high surface area in comparison to their larger counterparts of the same material. In synthetic nanoparticles, the proportion of atoms on the surface is much larger than the proportion of atoms in the interior of the particle. These factors give synthetic nanoparticles a higher surface reactivity than their counterparts of the same material. Zinc is a nutritional supplement and food additive. The melted and oxidized zinc at a high temperature can generate zinc oxide nanoparticles that affect the growth of many bacteria such as Staphylococcus, Streptococcus, and E. coli. Currently, there are widespread applications of zinc oxide nanoparticles in medicine because of their antibacterial effect. They are also used in several industries such as paints, pigments, dyes, electronics, cosmetics and personal care products. Consequently, humans are more exposed to zinc oxide nanoparticles via various routes such as dermal penetration, inhalational, oral and intravenous routes. In the last few years, the use of zinc oxide nanoparticles became controversial. Although zinc oxide nanoparticles can pass easily through the cell membrane and interact with cellular macromolecules leading to therapeutic effects on some organs, they were found to exert oxidative stress causing cytotoxic effects on other organs .