  The COVID-19 pandemic has stimulated the scientific world to intensify
virus-related studies, aimed at the development of quick and safe ways of
detecting viruses in human body, studying the virus-antibody and virus-cell
interactions, and designing nanocarriers for targeted antiviral therapies.
However, research on dangerous viruses can only be performed in certified
laboratories that follow strict safety procedures. Thus, developing deactivated
virus constructs or safe-to-use virus-like objects, which imitate real viruses
and allow performing virus-related studies in any research laboratory,
constitutes an important scientific challenge. One of the groups of such
species are the so-called virus-like particles (VLPs). Instead of capsids with
viral DNA/RNA, VLPs have synthetic cores with real virus proteins attached to
them. We have developed a method for the preparation of VLPs imitating the
virus responsible for the COVID-19 disease: the SARS-CoV-2. The particles have
Au cores surrounded by "coronas" of S1 domains of the virus's Spike protein.
Importantly, they are safe to use and specifically interact with SARS-CoV-2
antibodies. Moreover, Au cores exhibit localized surface plasmon resonance
(LSPR), which makes the synthesized VLPs suitable for biosensing applications.
Within our studies, the effect allowed us to visualize the interaction between
the VLPs and the antibodies and identify the characteristic vibrational
signals. What is more, additional functionalization of the particles with a
fluorescent label revealed their potential in studying specific virus-related
interactions. Notably, the universal character of the developed synthesis
method makes it potentially applicable for fabricating VLPs imitating other
life-threatening viruses.
