Novel Deactivation Strategies for Norovirus Using Copper-Infused Lignin Nanoparticles

The Norovirus is the leading cause of gastroenteritis in the United States, resulting in approximately 20 million illnesses and 700 deaths per year. Recent work by our group has shown that low concentrations of Cu(II) ions can bind to virus capsid proteins and cause virus aggregation. Virus capsid degradation and loss of infectivity occur when divalent copper is reduced to Cu(I), but free Cu(I) ions are unstable in the aqueous solution. As such, the stabilization of Cu(I) ions is of significant practical interest for antiviral applications. We investigated two reducing agents to produce Cu(I) ions, sodium ascorbate and lignin derived environmentally benign nanoparticles (EbNPs) [1]. The stability of Cu(I) over time was investigated spectrophotometrically using bathocuproinedsulfonic acid disodium salt (BCS) assays. The colloidal stability of EbNP-Cu(I) suspensions was investigated by dynamic light scattering and zeta potential measurements. When sodium ascorbate was present in aqueous solution, Cu(I) was oxidized to Cu(II) rapidly, and resulted in a loss of virucidal efficacy. When Cu(II) was mixed with EbNP suspensions, Cu(II) was reduced to Cu(I) and stabilized, which prevented oxidation for weeks. Thus, we hypothesize that surface functional groups of lignin nanoparticles stabilize Cu(I) against oxidation in aqueous solution. As a result, copper-infused EbNPs could produce stable, dilute Cu(I) solutions for antiviral applications in healthcare, food service, and waste water treatment.

 [1] Richter, A. P., & Velev, O. D., et al. “An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core” Nature Nanotech. (2015)