Tecnai 12 120 kv transmission

The SMALP sample was diluted in buffer solution (50 mM Sodium phosphate pH 7.0, 100 mM NaCl) to 1 X 10^-5 mg/ml. The sample was then drop cast onto a glow discharged carbon coated electron microscopy grid and negatively stained with Uranyl acetate. Imaging was performed with an FEI Tecnai 12, 120 kV transmission electron microscope (TEM) with an FEI Eagle 4k x 4K CCD camera. All subsequent image processing was carried out using Fiji/ImageJ

Prior to TEM analysis, both the ~50 nm and ~100 nm polystyrene nanoparticle samples were diluted in pure water by factors of ~100 and ~40, respectively. Formvar/carbon coated 300 mesh copper grids (Ted Pella Inc.) were made hydrophilic with an easiGlow (Pelco) benchtop glow discharge unit. 5 μL of sample were placed on each grid for 5 min before being manually dried using clean filter paper. Sample coated grids were imaged using a Tecnai 12 120 kV transmission electron microscope (FEI). Images were recorded using a Rio 16 CMOS with DigitalMicrograph software (Gatan Inc.). The resulting TEM images were analyzed using FIJI/ImageJ version 1.53v.^{54 (link)} Tiff-formatted files were converted to binary and contrast was enhanced using the Outline and Dilate features. Noise was removed using Despeckle. Circle radii were obtained using the Hough Circle Transform (HCT) plugin by University of California, Berkeley Vision Sciences with a radius search increment of 1 pixel and a Hough score threshold of 0.5 (more details on this plugin can be found here: https://imagej.net/plugins/hough-circle-transform).^{41 (link),42 (link)} TEM images with a resolution of ~0.5 nm/pixel were analyzed to generate a diameter and mass distribution for each sample. In total, 976 and 1291 particles were analyzed to generate the data shown for the ~50 nm and ~100 nm diameter nanosphere samples, respectively.