High-molecular-weight PVP keeps spray-dried phage PEV1 stable at low to moderate humidity

A Bioengineering & Translational Medicine study from the University of Sydney spray-dried phage PEV1 with polyvinylpyrrolidone (PVP) grades K15 to K100 and stored it for 180 days at 4, 22 and 40 °C and 15 to 53% relative humidity. At 33% relative humidity, high-molecular-weight PVPs (K40, K100) gave long-term stability while lower grades (K15, K25) lost 2–3 log10 of titre; degradation rose about tenfold above a water activity of 0.43, and at 40 °C and ≥43% RH titre losses were substantial even when the glass-transition offset exceeded 100 °C.