“…The clustered keywords in Clusters 1–4 reflect the four research hot spots in this field. For Cluster 1 (nanoparticulate systems for delivering drugs with anti-SARS-CoV-2 activity), typical keywords included: “nanoparticles,” “inhibition,” “drug-delivery,” and “antiviral activity.” For Cluster 2, (nanotechnology for rapid and quantitative SARS-CoV-2 detection), typical keywords included: “gold nanoparticles,” “diagnosis,” “rapid detection,” and “biosensor.” For Cluster 3 (nanovaccines against SARS-CoV-2 delivered by lipid nanoparticles), typical keywords included: “COVID-19,” “nanotechnology,” “vaccine,” and “lipid nanoparticles.” For Cluster 4 (screening antibodies for SARS-CoV-2 neutralization on the basis of viral structure), typical keywords included: “SARS-CoV-2,” “coronavirus,” “spike protein,” and “antibodies.” The closed-loop network suggested that the four hot spots could have overlap [47] . Furthermore, according to the data shown in Fig.…”