TY - JOUR A1 - Saleh, Maysoon I. A1 - Rühle, Bastian A1 - Wang, Shu A1 - Radnik, Jörg A1 - You, Yi A1 - Resch-Genger, Ute T1 - Assessing the protective effects of different surface coatings on NaYF4:YB3+, Er3+, upconverting nanoparticles in buffer and DMEM JF - Scientific reports N2 - We studied the dissolution behavior of β NaYF4:Yb(20%), Er(2%) UCNP of two different sizes in biologically relevant media i.e., water (neutral pH), phosphate buffered saline (PBS), and Dulbecco’s modified Eagle medium (DMEM) at different temperatures and particle concentrations. Special emphasis was dedicated to assess the influence of different surface functionalizations, particularly the potential of mesoporous and microporous silica shells of different thicknesses for UCNP stabilization and protection. Dissolution was quantified electrochemically using a fluoride ion selective electrode (ISE) and by inductively coupled plasma optical emission spectrometry (ICP OES). In addition, dissolution was monitored fluorometrically. These experiments revealed that a thick microporous silica shell drastically decreased dissolution. Our results also underline the critical influence of the chemical composition of the aqueous environment on UCNP dissolution. In DMEM, we observed the formation of a layer of adsorbed molecules on the UCNP surface that protected the UCNP from dissolution and enhanced their fluorescence. Examination of this layer by X ray photoelectron spectroscopy (XPS) and mass spectrometry (MS) suggested that mainly phenylalanine, lysine, and glucose are adsorbed from DMEM. These findings should be considered in the future for cellular toxicity studies with UCNP and other nanoparticles and the design of new biocompatible surface coatings. KW - Fluorescence KW - Lifetime KW - Method KW - Quantification KW - Stability KW - Coating KW - Surface chemistry KW - Lanthanide KW - Fluoride KW - Electrochemistry KW - ICP-OES KW - Upconversion KW - Nano KW - Particle KW - Aging KW - Quality assurance KW - Mass spectrometry KW - XPS PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515984 DO - https://doi.org/10.1038/s41598-020-76116-z SN - 2045-2322 VL - 10 IS - 1 SP - 19318-1 EP - 19318-11 PB - Springer Nature CY - London AN - OPUS4-51598 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute A1 - Andresen, Elina A1 - Saleh, Maysoon I. A1 - Würth, Christian A1 - Rühle, Bastian A1 - Radnik, Jörg A1 - Prinz, Carsten T1 - Influence of Surface Chemistry and Size on the Stability of β-NaYF4:Yb,Er Nanocrystals in Various Environments N2 - The use of inorganic lanthanide-doped upconversion nanoparticles (UCNP) in bioimaging and cellular studies requires biocompatible particles. One possible cause of UCNP toxicity is the release of potentially harmful fluoride and lanthanide ions as revealed by dilution studies in aqueous environments, particularly under high dilution conditions. To address this issue, suitable surface coatings preventing such effects in combination with fast screening methods suited for online monitoring and in situ analyses are desired. Here we present systematic studies of differently sized β-NaYF4:Yb,Er UCNP stabilized with different surface coatings and hydrophilic ligands varying in binding strength to the particle surface in various aqueous environments at different temperatures and UCNP concentrations. The concentration of the fluoride and lanthanide ions released upon particle dissolution was quantified electrochemically with a fluoride ion-sensitive electrode and inductively coupled plasma optical emission spectrometry (ICP-OES) and monitored fluorometrically, thereby exploiting the sensitivity of the upconversion luminescence to changes in size and surface chemistry. Moreover, changes in surface chemistry were determined with X-Ray photoelectron spectroscopy (XPS). Based upon our results, we could derive optimum screening parameters for UCNP stability studies and determine conditions and coating procedures and ligands for enhancing UCNP stability in aqueous environments. T2 - UPCON2021 CY - Online meeting DA - 06.04.2021 KW - Fluorescence KW - Lifetime KW - Method KW - Quantification KW - Stability KW - Coating KW - Surface chemistry KW - Lanthanide KW - Fluoride KW - Electrochemistry KW - ICP-OES KW - Upconversion KW - Nano KW - Particle KW - Aging KW - Quality assurance KW - Mass spectrometry KW - XPS PY - 2021 AN - OPUS4-52411 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholtz, Lena A1 - Tavernaro, Isabella A1 - Eckert, J. G. A1 - Lutowski, M. A1 - Geißler, D. A1 - Hertwig, A. A1 - Hidde, G. A1 - Bigall, N. C. A1 - Resch-Genger, Ute T1 - Influence of nanoparticle encapsulation and encoding on the surface chemistry of polymer carrier beads JF - scientific reports N2 - Surface-functionalized polymer beads encoded with molecular luminophores and nanocrystalline emitters such as semiconductor nanocrystals, often referred to as quantum dots (QDs), or magnetic nanoparticles are broadly used in the life sciences as reporters and carrier beads. Many of these applications require a profound knowledge of the chemical nature and total number of their surface functional groups (FGs), that control bead charge, colloidal stability, hydrophobicity, and the interaction with the environment and biological systems. For bioanalytical applications, also the number of groups accessible for the subsequent functionalization with, e.g., biomolecules or targeting ligands is relevant. In this study, we explore the influence of QD encoding on the amount of carboxylic acid (COOH) surface FGs of 2 μm polystyrene microparticles (PSMPs). This is done for frequently employed oleic acid and oleylamine stabilized, luminescent core/shell CdSe QDs and two commonly used encoding procedures. This included QD addition during bead formation by a thermally induced polymerization reaction and a post synthetic swelling procedure. The accessible number of COOH groups on the surface of QD-encoded and pristine beads was quantified by two colorimetric assays, utilizing differently sized reporters and electrostatic and covalent interactions. The results were compared to the total number of FGs obtained by a conductometric titration and Fourier transform infrared spectroscopy (FTIR). In addition, a comparison of the impact of QD and dye encoding on the bead surface chemistry was performed. Our results demonstrate the influence of QD encoding and the QD-encoding strategy on the number of surface FG that is ascribed to an interaction of the QDs with the carboxylic acid groups on the bead surface. These findings are of considerable relevance for applications of nanoparticle-encoded beads and safe-by-design concepts for nanomaterials. KW - Optical spectroscopy KW - Particle KW - Optical assay KW - IR spectroscopy; conductometry KW - Fluorescence KW - Quantum yield KW - Quality assurance KW - Nano KW - Synthesis KW - Surface chemistry KW - Quantification KW - Method PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581502 DO - https://doi.org/10.1038/s41598-023-38518-7 SN - 2045-2322 VL - 13 IS - 1 SP - 1 EP - 15 PB - Springer Nature AN - OPUS4-58150 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stock, V. A1 - Fahrenson, C. A1 - Voss, L. A1 - Thünemann, Andreas A1 - Boehmert, L. A1 - Sieg, S. A1 - Lampen, A. T1 - Impact of artificial digestion on the sizes and shapes of microplastic particles N2 - The environmental pollution with plastic debris is one of the great challenges scientists are facing in recent times Due to degradation by UV radiation and other environmental factors, larger pieces of plastic can decompose into microscale fragments which can enter human foodstuff through the food chain or by environmental entry Recent publications show a contamination of various food products with microplastic particles suggesting a widespread exposure Thus, orally ingested plastic particles pose a potential health risk to humans In this study, we investigated the impact of artificial digestive juices on the size and shape of the three environmentally relevant microplastic particles polystyrene (PS), polypropylene (PP) and polyvinyl chloride (PVC). T2 - 12th International Particle Toxicology CY - Salzburg , Austria DA - 11.09.2019 KW - Microplastic KW - Particle PY - 2019 AN - OPUS4-48847 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -