Cryo-TEM Imaging of Venetin-1 Nanoparticles

Venetin-1 at a concentration of 1 mg mL⁻¹ was ultrasonicated for 10 min at 40 °C in an ultrasonic chamber (Pol-Sonic, Poland). Then, the sample was vitrificated in a water solution on the TEM grid covered with Quantifoil R 2/2 carbon film (Quantifoil Micro Tools GmbH, Großlöbichau, Germany). Before observations, the grids were activated with oxygen plasma for 15 s in a Femto plasma cleaner (Diener Electronic, Germany). Next, 3 μL of the Venetin-1 suspension was transferred onto the grid, blotted with filter paper and immersed in liquid ethane for instant freezing by Vitrobot Mark IV (FEI Company, USA). Before observations, the samples were stored in liquid nitrogen. To transfer the specimens to the TEM microscope, they were loaded into the Gatan 626 Cryo-TEM holder (Gatan Inc., USA)^{59 (link)}. The samples were observed using a Tecnai F20 X TWIN microscope (FEI Company, USA) with 200-kV acceleration voltage of the emission gun. An Eagle 4k HS camera (FEI Company, USA) was used to record the images.