Prior to the SEM measurements, all samples were shock-frozen in liquid nitrogen and lyophilized overnight using a Beta 2-8 LCSplus -Martin Christ lyophilizer. The morphology of the freeze-dried samples was visualized via a Zeiss Supra 55 VP microscope (Faculty Center for Nano Structure Research) with an accelerating voltage between 3 and 5 kV. The samples were carefully fixed onto carbon tape at the top of the aluminum specimen containers and placed on the specimen holder. Subsequently, they were sputter-coated with gold to a thickness of ~ 3 nm (Leica EM SCD050) and positioned at the specimen stage of the SEM. Measurements were performed at a magnification range of 40x to 2000x, using a Secondary Electrons detector.