Antiviral properties of select carbon nanostructures and their functionalized analogs

The antiviral properties of nanocarbons namely, carbon nanotubes (CNT), graphene oxide (GO), reduced graphene oxide (rGO), hybrid GO-CNT, rGO-CNT and CNTs functionalized with carboxylic (CNT-COOH), phenol (CNT-phenol), silver (CNT-Ag) are presented. Escherichia coli MS2 bacteriophage was the model virus. All the nanocarbons showed antiviral activities and the activity increased with increase in concentration. CNT-phenol showed the highest antiviral activity (97.1%) at 0.3mg/mL followed by CNT-Ag (90%), GO-CNT (85.5%), rGO-CNT (83.5%), CNT-COOH (82.5%), CNT (78%), GO (45.6%) and rGO (39.5%) at the same concentration. At 0.05 mg/ml, compared to pure CNTs, those functionalized with silver and phenol showed 270% and 200% higher removal efficiencies respectively. GO and rGO were less efficient by themselves, but with the CNTs, namely GO-CNT and rGO-CNT, their activities enhanced by factors of 650 and 950% respectively. The antiviral activity of the nanocarbons was quantified based on both the concentration of nanocarbons needed to reach a 50 percent deactivation (LD₅₀) and the rate of deactivation. CNT-Phenol was the most effective antiviral nanocarbon studied here, it's LD₅₀ was 1400 times lower than the pure CNTs even though it had similar rate of deactivation as the latter, The antiviral efficiency of GO and rGO were relatively lower compared to the other nanocarbons, however they improved by 92% and 89% for GO and rGO when combined with the CNTs in a hybrid form. From the transmission electron microscopy (TEM) analysis, it was observed that the CNTs entangled the viruses which probably led to physical damage to their structure while the functional groups attached to CNTs such as phenol and Ag further enhanced toxicity due to their own properties.