title: Synchrotron-based X-ray fluorescence imaging of human cells labeled with CdSe quantum dots.
abstract: Synchrotron-based X-ray fluorescence (S-XRF) is a powerful technique for imaging the distribution of many biologically relevant elements as well as of "artificial" elements deliberately introduced into tissues and cells, for example, through functionalized nanoparticles. In this study, we explored the potential of S-XRF for chemical nanoimaging (100 nm spatial resolution, nanoXRF) of human cells through the use of functionalized CdSe/ZnS quantum dots (QDs). We used a commercially available QD-secondary antibody conjugate to label the cancer marker HER2 (human epidermal growth factor receptor 2) on the surface of SKOV3 cancer cells and beta-tubulin, a protein associated with cytoskeleton microtubules. We set up samples with epoxy inclusion and intracellular labeling as well as samples without epoxy inclusion and with surface labeling. Epoxy inclusion, also used in electron microscopy, has the advantage of preserving cell morphology and guaranteeing long-term stability. QDs proved to be suitable probes for nanoXRF due to the Se emission band, which is not in close proximity to any other emission band, and the signal specificity, which is preserved in both types of labeling. Therefore, nanoXRF using QD-based markers can be very effective at colocalizing specific intracellular targets with elements naturally present in the cell and may complement confocal fluorescence microscopy in a synergistic fashion.
authors.affiliation: Dipartimento di Fisica, Università di Perugia, 06123 Perugia, Italy. corezzi@fisica.unipg.it
authors.forename: Silvia
authors.initials: S
authors.lastname: Corezzi
authors.forename: Lorena
authors.initials: L
authors.lastname: Urbanelli
authors.forename: Peter
authors.initials: P
authors.lastname: Cloetens
authors.forename: Carla
authors.initials: C
authors.lastname: Emiliani
authors.forename: Lukas
authors.initials: L
authors.lastname: Helfen
authors.forename: Sylvain
authors.initials: S
authors.lastname: Bohic
authors.forename: Fausto
authors.initials: F
authors.lastname: Elisei
authors.forename: Daniele
authors.initials: D
authors.lastname: Fioretto
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D045744:Cell Line, Tumor; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods*; D045663:Quantum Dots; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D014404:Tubulin / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D018719:Erb-b2 Receptor Tyrosine Kinases; D018036:Selenium Compounds; D014404:Tubulin; C058667:cadmium selenide