Biomimetic virus-like particles with magnetic core. From bioactivity to an immunodiagnostic tool

In this study, biomimetic virus-like particles (VLPs) composed of superparamagnetic iron oxide nanoparticles (SPIONs) and receptor binding domain (RBD) of the SARS-CoV-2 virus were obtained. The bioactivity of the VLPs was subsequently tested, utilizing natural targets of the RBD protein: angiotensin-converting enzyme 2 (ACE2), toll-like receptor 4 (TLR4), and neutralizing anti-SARS-CoV-2 antibodies. The conducted analyses include both in vitro and in cellulo methods such as dynamic light scattering (DLS), zeta-potential measurement, bio-layer interferometry (BLI), cytotoxicity study, stimulation of the TLR4 activation pathway, spectral flow cytometry, and imaging flow cytometry. The data confirmed the bioactivity of the obtained VLPs, which were subsequently utilized for a proof-of-concept diagnostic tool for the detection of specific anti-SARS-CoV-2 antibodies. The method was proven sensitive and effective, with significantly decreased protocol time compared to commercially available ELISA tests.