A review of the application of zinc oxide nanoparticles in the biological sciences

Nanotechnology is an emerging branch of science that is widely used in various fields including medicine. Nanoparticles (NPs) are produced by various compounds in size, shape, and different chemical properties, which can be used in a variety of biological and biomedical applications. Metal NPs are used widely in many fields and have various properties making them appropriate for use in medical applications.Zinc is an essential trace element for almost all living organisms. Due to possessing a significant role in versatile biological processes, including fetal development, natural growth, wound healing, metabolism, immunity, cognitive functions, sperm generation, bone mineralization, neurological, and enzymatic processes.In recent decades, zinc oxide NPs have been one of the most popular types of NPs with numerous biological applications due to their biocompatibility and low toxicity and are used in a wide range of commercial applications including applications in many different industries such as pharmaceuticals, textiles, dyes, rubber, tissue engineering, antibacterial agents, and anti-cancer. Nowadays, significant scientific interest has been directed toward the application of nanomaterials in the modulation of stem cell proliferation and differentiation for further application in regenerative medicine. Zinc is one of the most plentiful trace metals in the human body and was reported to be essential for the regeneration of bone. ZnO-NPs exhibit attractive antibacterial properties. Particular emphasis was given to bactericidal and bacteriostatic mechanisms with a focus on the generation of reactive oxygen species (ROS). ROS has been a major factor for several mechanisms including cell wall damage due to ZnO-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force, and uptake of toxic dissolved zinc ions.  ZnO NPs present certain cytotoxicity in cancer cells and induce cancer cell death via the apoptosis signaling pathway. This autophagy induction was positively correlated with the dissolution of ZnO NPs in lysosomes to release zinc ions, and zinc ions released from ZnO NPs were able to damage lysosomes, leading to impaired autophagic flux and mitochondria.ZnO nanostructures, featuring antimicrobial activity, osteogenesis, and angiogenesis, have been also combined with additive manufacturing technologies with the final aim of designing novel advanced hybrid scaffolds for tissue engineering.Zinc deficiency is positively correlated with diabetes and may also affect the progress of Type 2 diabetes. Several zinc complexes have been synthesized and proven to be effective in rodent models of diabetes.ROS are generated by metal oxide nanoparticles which considerably help in fibroblast proliferation. The interlinkage of the fibroblast cells and zinc oxide nanoparticles was impacted by the surface area and particle size of the nanoparticles. Zinc oxide nanoparticles dressing increases apoptosis, bacteria clearance, platelet activation, tissue necrosis, re-epithelialization, tissue scar formation, debris removal, angiogenesis, and stem cell activation through wound healing. Nanoparticle-based drug delivery systems (DDS) can overcome the aforementioned limitations by releasing the drugs in a slow and sustained manner and delivering them to the desired area of the body system. This article provides an overview of some of the research relating to the use of zinc oxide nanoparticles in biological sciences.