While I haven't come across anything else, the statement that silver nanoparticles might inhibit viral infections is also echoed in this paper - Antiviral activity of mycosynthesized silver nanoparticles against herpes simplex virus and human parainfluenza virus type 3. There seem to be a number of studies that show Silver Nanoparticles interfere with viruses and by extension should help interfere in the infectability of COVID-19. As far as the lead author of this paper, he hasn't re-submitted this one but has submitted a paper on the markers for COVID-19's evolution: Mutation landscape of SARS-CoV-2 reveals three mutually exclusive clusters of leading and trailing single nucleotide substitutions