Scanning electron microscopy. Films were prepared and, when drying was complete, they were coated with 12-nm platinum (Pt)/palladium (Pd) alloy in a Cressington 208HR sputter coater and subsequently photographed on a Zeiss Supra 40V scanning electron microscope (Zeiss, Jena, Germany).

FTIR spectroscopy. FTIR spectroscopy was conducted on films prepared with and without virus using a Nicolet iS 50 FT-IR Spectrometer (Thermo Fisher Scientific, Waltham, MA). Films were placed under the probe, and scans were conducted in the 4000 to 800 cm−1 region using an ATR (attenuated total reflectance) method with a diamond/ZnSe prism.