Agilent 5500 microscope

AFM measurements were performed with an Agilent 5500 microscope (Agilent, Santa Clara, CA, USA), working in contact and tapping mode, under the control of PicoView software as previously described^{53 (link)}. OMVs were immobilized on freshly cleaved mica, with poly-L-lysine as a stabilizing matrix. We used SNL probes (Bruker Corp., Billerica, MA, USA) with nominal k = 0.35 N/m. For elasticity determination, the k constant of each probe was measured with a built-in Agilent Thermal-K setup.
Surface probing for elasticity determination was done with a built-in plugin for PicoView software, recording and analyzing force-distance curves. Usually, a resolution of 32 × 32 was used for probing over a chosen region of about 1.5 μm × 1.5 μm. The average elasticity of pixels correlating to grains was measured in the overall image, and then the values from several images for each sample were averaged (n > 25). For AFM analysis the same amount of pure OMVs was used.
Images were analyzed with Gwydion 2.61 software^{54 (link),55 (link)}. The size of OMVs was measured by manual selection using the “line” Gwydion tool, which measures the distance between two points—at least one hundred counts were measured for each type of OMVs.

After QCM-D assay, sensors were dried with a gentle nitrogen flow. The AFM images were obtained in air in the intermittent contact mode with an Agilent 5500 microscope (Agilent Technologies, Santa Clara, CA, USA) using silicon tips NSC15 (Mikromasch USA, San Jose, CA, USA), with a resonance frequency of ~325 kHz and a nominal spring constant of 40 N/m. The scanned areas were 2.0 µm × 2.0 µm. Images were acquired using Pico Image software v. 1.14 (Agilent Technologies, Santa Clara, CA, USA) and were processed with the Gwyddion software (Czech Metrology Institute). The Student’s t-test was used and a significant difference of p ≤ 0.01 was assumed.