Study of the geometric and mechanical features of nanoparticles of various nature by atomic force microscopy in PeakForce QNM mode

Objective: to identify the difference of the numerical values of parameters characterizing the geometric and mechanical (adhesive) properties of inorganic nanosized particles and nanosized particles of biological origin by atomic force microscopy using the mode of the mapping of surface features at nanosized resolution.

Material and methods. Exosomes isolated from the blood of Af mice by the method of sequential ultracentrifugation were used as bionanoparticles. Silver nanoparticles were used as inorganic nanoparticles. The nanoparticles were scanned in air with the help of the BioScope Resolve (Bruker) atomic force microscope in the PeakForce QNM in Air mode with the recording of the maps of adhesion forces and imaging of the topography of the studied surfaces.

Results. The silver nanoparticles and exosomes had similar but statistically different diameters (45.59 ± 1.04 nm and 41.25 ± 0.91 nm, р < 0.001 t-test). Nevertheless, the silver nanoparticles were characterized by higher values of both height and free surface area in comparison with the corresponding values of the exosome parameters. This leads to a higher value of the spreading ration for exosomes (the average ratio of diameter to height (d/h) was 11.78 for exosomes and 6.67 for nanoparticles (p < 0.001, Mann-Whitney U test) due to greater adhesion properties of the exosome membranes compared to the silver nanoparticles and a lower value of the ratio of the particle volume to its surface area. Averaged over the nanoscale areas of the nanoparticle surface, the adhesion forces of exosomes were higher (3.2 ± 0.57 nN) compared to those of silver nanoparticles (2.2 ± 0.03 nN, p < 0.05, Mann-Whitney U test).

Conclusion. The differences in the parameters of the geometric (diameter, height, free surface area) and mechanical properties (adhesion forces) of the silver nanoparticles and exosomes have been revealed, which allows identifying and differentiating of these nanoparticles by the methods of atomic force microscopy during the study of complex biological fluids with possible content of both the types of nanoparticles.

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