2.5. Scanning electron microscopy (SEM)
Small cubes were cut out from fresh skin of OFI, fixed with glutaraldehyde and dried under critical point conditions in a Polaron critical point dryer operated with liquid CO2. Before observation, the samples were sputtered with gold palladium alloy in a JEOL JFC sputterer. The observations were made with a JEOL JMS-6100 SEM operated at an accelerating voltage ranging from 5 to 8 kV and under secondary electron mode.
2.6. Optical microscopy
Cellulose cells residues were observed under a computer-controlled Zeiss Axiophot 2 optical microscope equipped with a camera and operated in Nomarski’s contrast.