Lip balm drying promotes virus attachment: Characterization of lip balm coatings and XDLVO modeling

HYPOTHESIS: Drying-induced decrease in lip balm surface energy enhances virus adhesion due to the emergence of strong hydrophobic colloid-surface interactions. EXPERIMENTS: A protocol was developed for preparing lip balm coatings to enable physicochemical characterization and adhesion studies. Surface charge and hydrophobicity of four brands of lip balm (dry and hydrated) and human adenovirus 5 (HAdV5) were measured and used to calculate the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) energy of interactions between lip balm coatings and HAdV5 as well as four other colloids: HAdV40, MS2 and P22 bacteriophages, and SiO(2). Quartz crystal microbalance with dissipation monitoring (QCM-D) tests employed SiO(2) colloids, HAdV5 and hydrated lip balms. FINDINGS: Drying of lip balms results in a dramatic decrease of their surface energy ([Formula: see text] 83.0 mJ/m(2)) making the surfaces highly hydrophobic. For dry lip balms, the interaction of the balm surface with all five colloids is attractive. For lip balms hydrated in 150 mM NaCl (ionic strength of human saliva), XDLVO calculations predict that hydrophilic colloids (MS2, P22, SiO(2)) may attach into shallow secondary minima. Due to the relative hydrophobicity of human adenoviruses, primary maxima in XDLVO profiles are low or non-existent making irreversible deposition into primary energy minima possible. Preliminary QCM-D tests with SiO(2) colloids and HAdV5 confirm deposition on hydrated lip balms.