Fig 1: Visual appearance and ultrastructure of the films: Photographs of specimens of the films of a size around 1 cm2 (a) before (left) and after (right) hydration in a physiological buffer and (b) upon hydration before (left) and after (right) cross-linking. The green spots in the dry sample are usual defects originating from occasional instabilities and dripping in the process of electrospinning. Note that the sample before cross-linking undergoes partial dissolution upon soaking in physiological buffer for 30 min, and so it is only partially recovered after hydration. (c) Spectrum of optical extinction of a cross-linked sample after a slight hydration taken with a V-770 device from Jasco (Tokyo, Japan). The pink line represents the optical emission of the diode laser used for welding. (d) Representative SEM micrograph of a sample before hydration. The scale bar corresponds to 5 µm.