Snl 10

The grid index of a single montmorillonite particle, which was later used for cell–mineral interaction against the bacterial coated probe, was recorded using the light microscope integrated in the AFM. Then, the structure of the respective particle was studied in PFQNM mode at 5 nN in air using a new SNL probe (k = 0.12 N m⁻¹, SNL-10, Bruker, USA). The same process was applied to a single R. erythropolis cell before its interaction with the kaolinite probe.

Before a relocation system with a built-in characterizer could be prepared, the potential characterizers had to be characterized themselves. A detailed description is given in ESI (SI-1, step 1).† Briefly, a sharp nitride lever tip (k = 0.12 N m⁻¹, SNL-10, Bruker, USA) was characterized by scanning a titanium roughness sample (RS-12M, Bruker, USA, ESI-Fig. 1a†) in Peak Force Quantitative Nanomechanical Mapping (PFQNM) mode in air with an atomic force microscope (AFM, Dimension Icon, Bruker Corporation, USA) and further used as built-in characterizer for the kaolinite modified probe. The titanium roughness sample allows the characterization of the very end of the AFM tip^{25 (link)} which was needed to precisely define the dilation length of the ∼40 nm thick kaolinite sheets. As a characterizer for the bacterial modified tipless probe, the more elongated Tap150A probe (k = 5 N m⁻¹, Bruker, USA) was characterized by tapping mode using a test grating TGT1 (NT-MDT Spectrum Instruments, USA). The TGT1 characterizes the overall tip shape at a sub-micron scale, which was essential for the morphology imaging of the bacteria in μm scale. We always used the frame down command, i.e., a horizontal fast scan direction. The resultant images were flattened by first order and subjected to blind tip reconstruction analysis using NanoScope Analysis software (version 8.15, Bruker).

Purified exosomes were diluted 1: 50 in deionized water; 5- to 10-μL samples were spotted onto freshly cleaved mica sheets (V-1, thickness 0.15 mm, size 15×15 mm) and dried with mild nitrogen flow for atomic force microscopy (AFM) scanning at room temperature. An Icon AFM (Dimension Icon, Bruker; Camarillo, CA) was used to obtain exosome topographic images at tapping mode, which generates high-resolution images by detecting the change in the vibration amplitude of the cantilever by silicon probes (SNL-10 and Scanasyst-Air, Bruker, USA). A 5×5 μm sample area was scanned in every microscopic field. Topographic images were recorded at 512×512 pixels at a scan rate of 1 Hz and 100 pN force. After that, samples were analyzed in peak force quantitative nanomechanical mapping (Peak Force QNM) mode to obtain nanomechanical maps of exosomes. In Peak Force QNM mode, the silicon probes acted on samples to obtain force-distance curves which are then used as feedback signals to generate the peak force error images. Image processing was performed with NanoScope Analysis software (Bruker; Camarillo, CA).