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In this work, we describe a simple solvothermal route for the synthesis of Eu3+-doped gadolinium orthovanadate nanocrystals (Eu:GdVO4−PAA) functionalized with poly(acrylic)acid (PAA), that are applicable as cell labeling probes for multimodal cellular imaging. The Eu3+ doping of the vanadate matrix provides optical functionality, due to red photoluminescence after illumination with UV light. The Gd3+ ions of the nanocrystals reduce the T1 relaxation time of surrounding water protons, allowing these nanocrystals to act as a positive MRI contrast agent with a r1 relaxivity of 1.97 mM−1 s−1. Low background levels of Eu3+, Gd3+, and V5+ in biological systems make them an excellent label for elemental microscopy by Laser Ablation (LA)-ICP-MS. Synthesis resulted in polycrystalline nanocrystals with a hydrodynamic diameter of 55 nm and a crystal size of 36.7 nm, which were further characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). The multifunctional nanocrystals were subsequently used for intracellular labeling of both human adipose-derived stem cells (MSCs) and A549 (adenocarcinomic human alveolar basal epithelial) cells.
Nano-carrier systems such as liposomes have promising biomedical applications. Nevertheless, characterization of these complex samples is a challenging analytical task. In this study a coupled hydrodynamic chromatography-single particle-inductively coupled plasma mass spectrometry (HDC-spICP-MS) approach was validated based on the technical specification (TS) 19590:2017 of the international organization for standardization (ISO). The TS has been adapted to the hyphenated setup. The quality criteria (QC), e.g., linearity of the calibration, transport efficiency, were investigated. Furthermore, a cross calibration of the particle size was performed with values from dynamic light scattering (DLS) and transmission electron microscopy (TEM). Due to an additional Y-piece, an online-calibration routine was implemented. This approach allows the calibration of the ICP-MS during the dead time of the chromatography run, to reduce the required time and enhance the robustness of the results. The optimized method was tested with different gold nanoparticle (Au-NP) mixtures to investigate the characterization properties of HDC separations for samples with increasing complexity. Additionally, the technique was successfully applied to simultaneously determine both the hydrodynamic radius and the Au-NP content in liposomes. With the established hyphenated setup, it was possible to distinguish between different subpopulations with various NP loads and different hydrodynamic diameters inside the liposome carriers.
Speciation of Se in fish is needed to elucidate the metabolism of this element in living organisms in the marine environment. In this paper, selenium concentration and its species distribution in several organs and tissues (liver, gills, kidney, muscle and gastrointestinal tract) of African catfish fed with a selenium-enriched garlic based diet was studied. The intention of this paper is focused on both the investigation of selenium distribution in the soluble protein fraction and the detection of selenoaminoacids. Thus, two different procedures have been developed. In the first procedure, screening of selenium in proteins in the Tris-buffer soluble fraction of different tissues was carried out by size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS) and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) separation and electroblotting onto membranes. For the amino acid analysis, several sample treatments for Se-species extraction, based on enzymatic hydrolysis, were compared. The best results were obtained for incubation at controlled temperature. Application of several sample treatments in conjunction with different chromatographic techniques (reverse phase, anion exchange and ion exchange/size exclusion) was crucial to unambiguous Se-species identification. In Se-enriched African catfish a noticeable increase in the content of selenium in different organs was observed, except for the liver, where the Se level remained unaltered. The kidney was the Se-target organ in animals fed with enriched Se food. Selenomethionine (SeMet) was the main Se species identified in fillet extracts, whereas the presence of selenocysteine (SeCys) was detected in the liver and both SeMet and SeCys were present in the kidney.