Pelco

For the HAADF-STEM measurements of the NP-stained PSMPs, the samples were drop-casted from diluted PSMP dispersions in ethanol onto carbon-coated copper grids (PELCO by Ted Pella, Inc., 400 mesh). For the NPL-stained PSMPs, lacey grids with otherwise the same specifications were used. Imaging was performed with a ThermoFisher Scientific Talos F200S TEM at 200 kV.

Transmission electron microscopy (TEM, JEOL Ltd., Tokyo, Japan) was used to characterize AgNP morphology. Samples were prepared using a method reported previously by Rahman et al. [13 (link)]. The reaction media was first filtered using a glass microfiber filter (diameter 25 mm, pore size 1.2 µm). TEM samples were prepared by casting 30 μL of filtrate onto the surface of a PELCO^® (Fresno, CA, USA) TEM Grid Carbon Type- B (Ted Pella Inc., 3.05 mm O.D., 400 mesh, 0.4 × 2 mm single slot Cu) and air-dried for 24 h. The TEM analysis used a JOEL JEM-1400 Plus Transmission Electron Microscope (120 kV, 1 kV step, 69 μA beam current, 100 k× magnification, spot size 1) equipped with embedded scanning transmission electron microscopy (STEM, JEOL Ltd., Tokyo, Japan).

The morphologic characteristics of BM-MSC exosomes were observed by TEM (A Zeiss-EM10C-Germany). To prepare the samples, 25 μL of diluted exosomes were carefully placed on carbon films on 300 mesh copper grids (AGS160-3) and incubated for 3 min at room temperature (RT). Subsequently, the exosomes were stained with a uranyl acetate solution (PELCO, Ted Pella). Given the dehydration and fixation of exosomes during the preparation process, the shape and size of exosomes could be changed in the captured image.

A cryogenic scanning electron microscope (SEM, FEI Quanta 200/Quorum PP2000TR FEI, Plant Cell Biology Core Laboratory, The Institute of Plant and Microbial Biology, Academia Sinica, Taiwan) was used to carry out the observations of the immobilized cell samples at 5 kV. The beads containing the immobilized cells were initially cut by scalpel and then they were fixed on a specimens-stage using TedPella PELCO^® conductive graphite gel. Next the specimens were pretreated with a sequence of freeze-dried and Au sputtering processes. Following this procedure, the specimens were frozen using a manifold freeze dryer and then are dried at −80 ℃ overnight. Finally, energy dispersive X-ray (EDX) analysis on immobilized cell samples was performed by the field emission-SEM using a EDX spectrometer (Hitachi S-4700 type-II with Horiba EMAX-ENERGY EX-300, National Tsing Hua University, Hsinchu, Taiwan).

The morphology of p116-assembled particles was visualized using a transmission electron microscope (H-7500, Hitachi, Tokyo, Japan) with an accelerating voltage of 100 KeV. 10 μL of the p116-assembled particle-containing solution was placed onto a carbon-coated 300-mesh copper grid (PELCO, Ted Pella, Inc., Redding, CA, USA) and stayed for 1 min. The excess solution was wicked dry, and the sample was stained with 10 μL 1% phosphotungstic acid for 30 s (negative staining). The excess solution was again wicked dry, and the grid was allowed to air dry before TEM imaging. For AFM imaging, 50 μL the sample containing p116-assembled particles was dropped onto a freshly cleaved mica sheet and allowed to stay for 40 min for adsorption. The sheet was washed twice with Milli-Q water and air-dried for 48 h in the dry cabinet before AFM imaging. AFM measurements were performed with an atomic force microscope (NanoWizard^TM, JPK Instruments, Berlin, Germany). The AFM probe used was 200 mm-long gold-coated cantilevers with oxide sharpened Si₃N₄ tips (Olympus, Tokyo, Japan). The spring constant for the cantilevers was 0.02 nN/nm. The scan rate was 1 Hz.