Antimicrobial and Antioxidant Activity of the Biologically Synthesized Tellurium Nanorods; A Preliminary In vitro Study

Recent theranostic (therapeutic or diagnostic) applications of tellurium nanoparticles have attracted a great interest for development of different methods for synthesis of this valuable nanostructure, especially via biological resources.
In the present study, the antimicrobial and antioxidant effects of the tellurium nanorods (Te NRs) biosynthesized by a bacterial strain Pseudomonas pseudoalcaligenes strain Te were evaluated.
The antimicrobial effect of Te NRs and potassium tellurite against different bacterial and fungal pathogens was assessed by microdilution method. Furthermore, the disk diffusion method was used to evaluate the antibacterial effect of the biogenic Te NRs and potassium tellurite against methicillin-resistant Staphylococcus aureus, alone or in combination with various antibiotics. Also, the biogenic Te NRs were investigated for antioxidant activity using 2, 2-diphenyl- 1-picrylhydrazyl (DPPH) scavenging activity and reducing power assay.
Transmission electron micrograph (TEM) of the purified Te NRs showed individual and rod-shaped nanostructure (~22 nm diameter by 185 nm in length). Based on the data obtained from both microdilution and disk diffusion method the K2TeO3 exhibited a higher antibacterial and antifungal activity compared to the Te NRs. The measured IC50 for the biogenic Te NRs (i.e. DPPH radical scavenging activity) was found to be 24.9 μg.mL-1, while, K2TeO3 has represented only 17.6 ± 0.8 % DPPH radical scavenging effect at the concentration of 160 μg.mL-1. The reducing power assay revealed a higher electron-donating activity for Te NRs compared to K2TeO3.
Based on the data obtained from both microdilution and disk diffusion method the K2TeO3 exhibited a higher antimicrobial and antifungal activity than Te NRs. Te NRs didn’t show the antibacterial effect against the tested bacterial strain: MRSA and showed an inhibitory effect and antibacterial activity of the effective antibiotics. However, more studies should be performed to explore the action mechanism of the produced biogenic Te NRs.