Antimicrobial and immunomodulatory potential of nanoscale hierarchical one-dimensional zinc oxide and silicon carbide materials

Highlights: • This study compared the antibacterial activity of [0001]-ZnO NRs and [111]-SiC NWs. • The ZnO NRs were 40 nm wide, 1 μm long, and grew in the [0001] direction. • NRs and NWs showed various nano-sizes, shapes, geometries, and crystal directions. • Various gram-negative and gram-positive bacteria were used for antibacterial tests. • ZnO NRs acts as a strong bactericide with large contacting surface for bacterial killing. This work reports the comparison of antimicrobial and immunomodulatory activities between nanoscale hierarchical ZnO nanorods (NRs) and SiC nanowires (NWs). The fabricated one-dimensional (1D) materials possess various nanoscale sizes, morphologies, geometries, and crystal directions. A developed hexamethylenetetramine-assisted hydrothermal regime was followed for preparing wurtzite–ZnO NRs with 40 nm average width, 1 μm length, and [0001] growth orientation. The antibacterial activity of NRs was compared with that of SiC NWs, which had 50–80 nm width and [111] direction. The antibacterial activity of the hierarchical NRs and NWs was tested using different microorganisms including Gram-positive and Gram-negative bacteria and fungi strains. The microbial inactivation of the hierarchical 1D nanomaterials was evaluated by inhibition zone, minimal inhibition concentration (MIC), cell viability assays, and nitroblue tetrazolium reduction test. Cell apoptosis was elucidated by confocal laser scanning microscopy. The scanning electron microscope results showed that [0001]-ZnO NRs led to higher loss in bacterial viability than [111]-SiC NWs. Also, ZnO NRs exhibited lower MIC values than SiC NWs with 3.9, 7.9, 31.25, and 7.91 μg/mL for P. aeruginosa, A. baumannii, S. aureus ATCC 29213, S. typhi ATCC 6539, respectively. This is caused by the higher surface area, smaller width and length, hexagonal wurtzite structure, and highly exposed [0001] polar surface grown along the c-axis of ZnO NRs.