Ultra 55 electron microscope

Scanning electron microscopy was performed as described previously (Dahl, 2004 (link)). Msm strains were grown to stationary phase. Culture aliquots were concentrated by centrifugation, resuspended, and fixed with 2.5% glutaraldehyde. Then, sequential ethanol dehydrations were performed. After permutation with isopentylosacetate, critical point drying was determined using a Hitachi HCP-2 Critical Point Dryer (Hitachi High-Technologies Corp., Tokyo, Japan). Samples were gold sputter coated (Technics Hummer V; Anatech), and ultrastructure examination was performed using a Zeiss Ultra 55 electron microscope.

The SEM analysis of alginate nanoparticles was performed using an ULTRA 55 electron microscope (Zeiss, München, Germany), equipped with a thermal field emission transmitter and three different detectors (EsB detector with filtering grid, high-efficiency integrated lens SE detector, Everhart–Thornley secondary electronic detector). The parameters of the microscope were fixed as follows: Electron acceleration voltage: 200 V–20 KV; working distance: 1 mm; sub-nanometric resolution at 15 kV; beam current up to 100 nA. Several drops of the aqueous solution of alginate nanoparticles (500 μg/mL) were deposited on a silicon substrate previously cleaned in successive baths of acetone and isopropanol under ultrasonication across 10 min, and rinsed thoroughly with ultrapure water. Then the substrate was dried at 100 °C for 1 h before observation.