Raman Fingerprints of the SARS-CoV‑2 Delta Variant and Mechanisms of Its Instantaneous Inactivation by Silicon Nitride Bioceramics

Raman spectroscopy uncovered molecular scale markers of the viral structure of the SARS-CoV-2 Delta variant and related viral inactivation mechanisms at the biological interface with silicon nitride (Si3N4) bioceramics. A comparison of Raman spectra collected on the TY11-927 variant (lineage B.1.617.2; simply referred to as the Delta variant henceforth) with those of the JPN/TY/WK-521 variant (lineage B.1.617.1; referred to as the Kappa variant or simply as the Japanese isolate henceforth) revealed the occurrence of key mutations of the spike receptor together with profound structural differences in the molecular structure/symmetry of sulfur-containing amino acid and altered hydrophobic interactions of the tyrosine residue. Additionally, different vibrational fractions of RNA purines and pyrimidines and dissimilar protein secondary structures were also recorded. Despite mutations, hydrolytic reactions at the surface of silicon nitride (Si3N4) bioceramics induced instantaneous inactivation of the Delta variant at the same rate as that of the Kappa variant. Contact between virions and micrometric Si3N4 particles yielded post-translational deimination of arginine spike residues, methionine sulfoxidation, tyrosine nitration, and oxidation of RNA purines to form formamidopyrimidines. Si3N4 bioceramics proved to be a safe and effective inorganic compound for instantaneous environmental sanitation.