Fig. 1.

Crystallization of influenza vaccine coatings on Ti sheets. (a) Representative, brightfield optical microscopy images of coatings after storage at ambient conditions (20–23 °C, 20–45% relative humidity) for 15 days. Although all samples were stored for the same amount of time under the same conditions, different degrees of crystallization occurred, as shown by the crystallized portions of the coatings that appear white under these imaging conditions. (b) X-ray diffraction (XRD) patterns corresponding to samples i–v in part (a). Scan range was, 2θ = 8°–40°. Peak shifts were corrected using Ti (P6₃/mmc; a = b = 2.950 Å, c = 4.686 Å; α = β = 90°, γ = 120°) as a standard reference material [39]. Structural analysis was performed by comparing observed characteristic XRD peaks with simulation results based on cell information of trehalose-dihydrate and trehalose anhydrous forms [40,41]. XRD patterns were comparable to characteristic peaks for trehalose-dihydrate crystals.