Identification of size differences of gold nanoparticles on cell surface by curvature reconstruction method using atomic force microscopy

We have developed a curvature reconstruction method (CRM) for the size estimation of nanoparticles attached and sunk into the rough surface of cells by fitting the curvature of such particles' outer shapes measured using sectional height images obtained by atomic force microscopy (AFM). A dried cell surface, on which a mixture of 30 and 50 nm gold particles was placed, was traced by AFM using a carbon nanotube (CNT) tip to estimate particle size distribution using CRM, and particle size distribution was also measured by field-emission scanning electron microscopy (FE-SEM) for confirmation. The results showed the CRM-estimated diameters of the nanoparticles were within an error of 7.57 ±5.41 nm independent of the difference in the sizes of particles, indicating that (1) a set of nanometer-sized marker probes with 20 nm differences in diameter can be distinguished even on the rough surface of cells, and that (2) errors might be caused by the offset of traces of particle curvature indicated by the shape of the CNT tip used.