Dual surrogate imprinting: an innovative strategy for the preparation of virus-selective particles

This work involves the preparation of dual surrogate-imprinted polymers (D-MIPs) for the capture of SARS-CoV-2. To achieve this goal, an innovative and novel dual imprinting approach using carboxylated-polystyrene (PS-COOH) nanoparticles with a diameter of 100 nm and a SARS-CoV-2 Spike-derived peptide was carried out at the surface of amine-functionalized silica (PS-NH₂) microspheres with a diameter of 500 nm. Firstly, PS-COOH nanoparticles with the same size and spherical shape as the SARS-CoV-2 virus were employed to form hemispherical indentations (HI) at the surface of the PS-NH₂ microspheres (obtaining dummy particle-imprinted polymers, HI-MIPs). Next, a specific peptide sequence representing the Spike protein at the surface of the target virus was also used as the second template to generate specific peptide binding sites at the HI. Finally, the PS-COOH and the peptide were removed by several washing steps providing D-MIPs, comprising both dummy particle indentations (HI) and peptide binding sites. The D-MIPs and HI-MIPs were in-depth characterized via scanning electron microscopy (SEM), transmission electron microscope (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy dispersive X-ray analysis (EDAX). 100% rebinding efficiency was achieved for the SARS-CoV-2 peptide with D-MIPs highlighting its specificity vs. non-peptide-imprinted control polymers (HI-MIPs), which only achieved a binding efficiency of <40.5%. D-MIPs also showed higher affinity than HI-MIPs towards real SARS-CoV-2 virus. Furthermore, lower rebinding percentages for both HI-MIPs (8.5%) and D-MIPs (6.9%) were obtained when incubated with an alternative peptide (i.e., characteristic for Zika virus) indicating a successful peptide imprinting process for the target SARS-CoV-2 peptide.