Fei teneo lv feg sem

The morphology and structure of PLGA nanoparticles were characterized by scanning electron microscopy (SEM) using FEI Teneo LV FEG SEM (Thermo Fisher Scientific) with the Everhart-Thornley Detector (ETD) for secondary and back-scattered electrons. All types of PLGA nanoparticles were visualized using a voltage (HV) set to 2.00 kV, and beam current (curr) set to 13, 25, or 50 pA depending on the magnification. The magnification varied with each image (refer to figure caption for this detail). The obtained images using the ETD had an electron beam dwell time of 10 microseconds and resolution of 1536 × 1026 px.

Tissue sections and punches were fixed in a 2.5% glutaraldehyde, 1.5% paraformaldehyde, and 0.12 M sodium cacodylate buffer (pH 7.4) solution for a minimum of 24 h, then rinsed with a 0.12 M sodium cacodylate buffer (pH 7.4) at 3 × 15 min intervals and placed in a 1% OsO₄ solution for 1 h. Samples were then dehydrated by subsequent immersion in 9 ethanol-water solutions with increasing concentration (15% up to 100%) at 15 min intervals before immediately being placed in a Tousimis 931 critical point dryer (Tousimis, Rockville, MD). After fixation, samples were mounted onto SEM stubs and sputter coated (Cressington Scientific Instruments, Watford, England) with a 6 nm-thick coating of iridium. All SEM images were acquired using a FEI Teneo LV FEG SEM (Thermo Fisher Scientific, Waltham, MA) with a high voltage of 2 kV and a current of 13 pA.