Nanotoxicology of Metal Oxide Nanoparticles

Amedea Seabra, Nelson Durán
2015 Metals  
This review discusses recent advances in the synthesis, characterization and toxicity of metal oxide nanoparticles obtained mainly through biogenic (green) processes. The in vitro and in vivo toxicities of these oxides are discussed including a consideration of the factors important for safe use of these nanomaterials. The toxicities of different metal oxide nanoparticles are compared. The importance of biogenic synthesized metal oxide nanoparticles has been increasing in recent years; however,
more » ... ent years; however, more studies aimed at better characterizing the potent toxicity of these nanoparticles are still necessary for nanosafely considerations and environmental perspectives. In this context, this review aims to inspire new research in the design of green approaches to obtain metal oxide nanoparticles for biomedical and technological applications and to highlight the critical need to fully investigate the nanotoxicity of these particles. OPEN ACCESS Metals 2015, 5 935 Keywords: nanotoxicity; metal oxide nanoparticles; biogenic nanoparticles; cytotoxicity; in vivo toxicity and ecotoxicity Copper Oxide (CuO, Cu2O) Nanoparticles Copper and copper oxide nanoparticles are used in optical and electronics applications and are a promising antimicrobial agent [5, 24] . Several researchers have described the biogenic synthesis of copper based nanoparticles for a variety of applications. Hasan et al. [25] demonstrated that Serratia sp. produces an intracellular mixture of metallic copper and different copper oxides. Copper oxide (Cu2O) nanoparticles (10-20 nm) were synthesized at room temperature using the baker's yeast Saccharomyces cerevisiae [26] . The proposed mechanism is based on the partial gaseous hydrogen pressure of the reduction potential of metallic ions, which indicates the dependence of membrane bound oxido-reductases [26] . Usha et al. [27] reported the synthesis of copper oxide by Streptomyces sp. for antimicrobial applications in textiles. Copper oxide nanoparticles (100-150 nm) were obtained in solution by the reduction of copper sulfate by the reductase enzymes of the microorganism. The authors demonstrated the antibacterial (against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus)) and antifungal (against Aspergillus niger) efficacies of nanoparticle-coated fabrics. Scanning electron microscopy (SEM) revealed nanoparticles embedded on the treated fabric textile. The durability of the finished fabric was evaluated [27] . Singh et al. [28] reported the biological synthesis (E. coli) of copper oxide nanoparticles with different sizes (10-40 nm, plus aggregates) and shapes (quasi-spherical). The results indicated the presence of a mixture of Cu2O and CuO phases. The proteins secreted by E. coli, with molecular weights ranging from 22 to 52 KDa, were attributed to reduced copper ions and stabilized the nanoparticle suspension [28] . Fungi can also synthesize metallic oxide nanoparticles. The biogenic synthesis of copper oxides was performed using Penicillium aurantiogriseum, P. citrinum and P. waksmanii isolated from soil [29] . The authors investigated the effects of experimental parameters (pH and salt concentration) on the size of biogenic nanoparticles. SEM indicated a spherical shape of the nanoparticles [29] . Another green synthesis of Cu2O used Tridax procumbens leaf extract [30] . The resulting Cu2O nanoparticles were coated with polyaniline by a chemical polymerization technique. Hexagonal and cubic nanoparticles with rough surfaces were observed by SEM. The antibacterial effect of the Cu2O nanoparticles was evaluated against E. coli. A 65% inhibition of bacterial growth was observed upon the incubation of E. coli with 20 µg/cm 3 of nanoparticles. A 100% inhibition was found for Cu2O concentrations in the range of 50-60 µg/cm 3 [30] . Sangeetha et al. [31] produced mono-dispersed, versatile and highly stable CuO nanoparticles from Aloe vera extract. This method is both ecofriendly and inexpensive, and it produced spherical CuO nanoparticles with a size range of 15-30 nm [31]. Iron Oxide (Fe2O3, Fe3O4) Magnetic Nanoparticles Magnetic iron oxide nanoparticles show potential in several biomedical applications, including drug delivery, hyperthermia and nuclear magnetic resonance imaging [2,32,33]. In addition to the classical
doi:10.3390/met5020934 fatcat:uxa7r2k7kva5zdloniv43cr3fi