Elastic phase response of silica nanoparticles buried in soft matter

Abstract

Tracking the uptake of nanomaterials by living cells is an important component in assessing both potential toxicity and in designing future materials for use in vivo. We show that the difference in the local elasticity at the site of silica (SiO2) nanoparticles confined within a macrophage enables functional ultrasonic interactions. By elastically exciting the cell, a phase perturbation caused by the buried SiO2 nanoparticles was detected and used to map the subsurface populations of nanoparticles. Localization and mapping of stiff chemically synthesized silica nanoparticles within the cellular structures of a macrophage are important in basic as well as applied studies.

Beating beats mixing in heterodyne detection schemes

“…To illustrate the importance of beating in heterodyne measurements, we use the example of heterodyne force microscopy (HFM) [8][9][10] , as it represents a model system with a highly nonlinear mixing element (much higher order than quadratic). HFM enables the non-destructive imaging below a surface with nanometre resolution using an atomic force microscope [11][12][13][14][15][16][17][18][19] . The typical excitation scheme is sketched in Fig.…”

Acoustic Scanning Probe Microscopy: An Overview

“…Alternatively, electronic interconnect architectures have been cut to demonstrate the capability of A-SPM techniques for imaging subsurface voids [71]. Finally, in some cases, as in the subsurface imaging of cells exposed to nanoparticles, the comparison with blank control samples allowed a better interpretation of A-SPM images [72,73].…”

“…Notwithstanding this limitation, SNFUH has been demonstrated to be a versatile tool for the characterization of nanoscale subsurface features of samples. SNFUH has been used to detect defects at buried interfaces in interconnect architectures [71] and for the subsurface imaging of cells, revealing the intracellular structures [68] as well as the presence of internalized submicrometrical and nanometrical objects either biological (malaria parasites) [69] or synthetic (nanoparticles) [72,73].…”

A subsurface add-on for standard atomic force microscopes

“…Ultimately, this is of crucial importance, as subsurface imaging is a long standing desire in microscopy in general. One might think about applications in cell biology, 4,13,[18][19][20] material science, 12,14,15,29 and nanoelectronics 4,17 as well as nanomechanics.…”

“…By now, ultrasound-AFM techniques have been applied to image nanoparticles inside polymer matrices, 4,[12][13][14][15][16] voids in metals, 17 the inside of mammal cells, 4,18,19 the inside of plant cells, 20 and for the determination of resonance frequencies as well as their mode shapes of nanomechanical systems. 21 Although it has been successfully demonstrated on all these different systems that ultrasound-AFM provides access to otherwise unobtainable sample information, the interpretation of these images is not well understood, as the physical origin of the contrast formation as well as the incredible resolution remain (until now) a mystery.…”