6 Materialchemie
Filtern
Erscheinungsjahr
- 2018 (2) (entfernen)
Dokumenttyp
Sprache
- Englisch (2)
Schlagworte
- Fluorescence (2) (entfernen)
Organisationseinheit der BAM
Biomedical applications, including functional biomaterials, carbohydrate-arrays, and glycan-based biosensors.
The chemistry of glycan immobilization plays an essential role in the bioavailability and function of surface bound carbohydrate moieties. For biomedical applications the stability over time (shelf life) of glycan arrays is a crucial factor. Herein we report on approaches for surface and interface characterization relevant to the needs of production of glycan microarrays which were tested using model carbohydrate surfaces. For detailed characterization of glycan model surfaces we used a combination of X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and ToF SIMS which are complementary techniques of surface chemical analysis. Links to fluorescence spectroscopy often used for characterization in the microarray community were established as well. In detail, amine-reactive silicon oxide and glass surfaces were used for anchoring oligosaccharides with an amino linker. The amount of surface bound carbohydrates was estimated by X-ray photoelectron spectroscopy (XPS). Glycan immobilization was investigated using lectins, which are glycan-binding molecules. A shelf life study of model glycan microarrays on epoxy-coated glass surfaces was done over a period of 160 days under different storage conditions utilizing fluorescence, ToF-SIMS and XPS analysis. It was shown that glycan activity of the models used can be maintained at least for half a year of storage at 4 °C.
During the last years, there has been a rapid rise in the use of nanomaterials in consumer products. Especially silver nanoparticles are frequently used because of their well-known optical and antimicrobial properties. However, the toxicological studies focusing on silver nanoparticles are controversial, either claiming or denying a specific nano-efffect. To contribute to localizing nanoparticles in toxicological studies and to investigate the interaction of particles with cells, a fluorescent marker is often used to monitor their transport and possible degradation. A major problem, in this context is the issue of binding stability of a fluorescent marker which is attached to the particle.
In order to overcome this problem we provide an investigation of the binding properties of fluorescence-labeled BSA to small silver nanoparticles. Therefore, we synthesized small silver nanoparticles which are stabilized by poly(acrylic acid). The particles are available as reference candidate material and were thoroughly characterized in an earlier study. The ligand was exchanged by fluorescence marked albumin (BSA-FITC). The adsorption of the ligands was monitored by dynamic light scattering (DLS). To verify that the observed effects on the hydrodynamic radius originate from the successful ligand exchange and not from agglomeration or aggregation we used small angle X-ray scattering (SAXS). The fluorescent particles were characterized by UV/Vis and fluorescence spectroscopy. Afterwards, desorption of the ligand BSA-FITC was monitored by fluorescence spectroscopy and the uptake of particles in different in vitro models was studied.
The particles are spherical and show no sign of aggregation after successful ligand exchange. The fluorescence intensity is quenched significantly by the presence of the silver cores as expected, but the remaining fluorescence intensity was high enough to use these particles in biological investigations. Half-life of fluorescence labeling on the particle was 21 d in a highly concentrated solution of non-labeled BSA. Thus, a very high dilution and long incubation times are needed to remove BSA-FITC from the particles. Finally, the fluorescence-labeled silver nanoparticles were used for uptake studies in human liver and intestinal cells, showing a high uptake for HepG2 liver cells and almost no uptake in differentiated intestinal Caco-2 cells. In conclusion, we showed production of fluorescence-marked silver nanoparticles. The fluorescence marker is strongly adsorbed to the silver surface which is crucial for future investigations in biological matrices. This is necessary for a successful investigation of the toxicological potential of silver nanoparticles.