title: Quantitative visualization of colloidal and intracellular gold nanoparticles by confocal microscopy.
abstract: Gold nanoparticles (AuNPs) have the potential to become a versatile biomarker. For further use of AuNPs labeled with functionalized molecules, their visualization in biological systems by routine laboratory tools such as light microscopy is crucial. However, the size far below the diffraction limit affords specialized parameters for microscopical detection, which stimulated the current study, aimed to determine from which size onward AuNPs, either in dispersion or cell-associated, can be reliably detected by standard confocal microscopy. First, gold colloids of size-restricted fractions are examined in dispersion. At a minimum particle size of 60 nm, detection appears to be reliable. Particle counts in dilution series confirm these results by revealing single particle detection of 60-nm colloids. Second, AuNPs are visualized and quantified in cells, which interestingly cause a phase shift in the reflection of AuNPs. Gold mass spectroscopy confirms the number of AuNPs counted microscopically inside cells. Furthermore, it demonstrates for the first time a very high diffusion rate of 15-nm particles into the cells. In conclusion, the results back the suitability of confocal microscopy for the quantitative tracking of colloidal and intracellular gold nanoparticles sized 60 nm.
authors.affiliation: Friedrich-Loeffler-Institut Mariensee, Institute of Farm Animal Genetics, Federal Research Institute of Animal Health, Holtystr. 10, D-31535 Neustadt, Germany. sabine.klein@fli.bund.de
authors.forename: Sabine
authors.initials: S
authors.lastname: Klein
authors.forename: Svea
authors.initials: S
authors.lastname: Petersen
authors.forename: Ulrike
authors.initials: U
authors.lastname: Taylor
authors.forename: Detlef
authors.initials: D
authors.lastname: Rath
authors.forename: Stephan
authors.initials: S
authors.lastname: Barcikowski
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D002461:Cell Line, Transformed; D002498:Centrifugation; D042783:Endothelial Cells / Q000166:cytology; D017979:Gold Colloid / Q000032:analysis / Q000737:chemistry*; D042541:Intracellular Space / Q000737:chemistry*; D013058:Mass Spectrometry; D053768:Metal Nanoparticles / Q000737:chemistry*; D018613:Microscopy, Confocal / Q000379:methods*; D010316:Particle Size; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet; D020349:Surface Plasmon Resonance
chemical_list: D017979:Gold Colloid