Persistent Green Luminescence in Nanoparticles Functionalized with SARS-CoV-2 Spike Proteins: Virus-Like Particles Showing Active Targeting toward Selected Cells

The possibility of using nanoparticles (NPs) showing prolonged luminescence in the biosensing and bioimaging fields of science is now attracting increasing attention. Such materials can help to overcome the problems of autofluorescence or increased photodamage because, for example, fractionated irradiance can be used in the light-induced generation of reactive oxygen species experiments. However, the carefully designed and engineered surface functionalization of those NPs is required for not only decreased toxicity but most importantly for active targeting toward selected cell types. As a solution, herein, we propose the construction of virus-like particles, which by mimicking the properties of real viruses can selectively enter cells with Toll-like receptors (TLRs), and additionally show afterglow emissive properties for enhanced biosensing and bioimaging applications. In particular, we have functionalized the surface of rod-like, Mn-doped, Zn₂GeO₄ NPs, showing efficient green persistent luminescence, with so-called "artificial corona" composed of SARS-CoV-2 S1 spike proteins. The designed material preserved unique optical properties, including stable green luminescence with persistent decay time at the level of several dozen seconds, showed decreased cytotoxicity, and, most importantly, was taken up more readily by the human pancreatic cancer cell lines positive for TLRs with respect to the cell line negative for those markers.