Jana Wotschadlo

Biocompatible fluorescent nanoparticles for pH-sensoring

Dialysis of a mixture of fluorescein and sulforhodamine B marked dextran derivatives yields biocompatible and tuneable nanosensors that can be used for ratiometric pH measurements.

Amino‐Functionalized Cellulose Nanoparticles: Preparation, Characterization, and Interactions with Living Cells

Spherical nanoparticles with sizes from 80 to 200 nm are obtained by self-assembly of highly functionalized 6-deoxy-6-(ω-aminoalkyl)aminocellulosecarbamates. The particles are very stable, nontoxic, and possess primary amino groups that are accessible to further modifications in aqueous suspension. The particles can be labeled with rhodamine B isothiocyanate without changing their size, stability, and shape. The nanoparticles obtained are investigated by means of photo correlation spectroscopy, zeta potential measurements, SEM and fluorescence spectroscopy. Incorporation of the nanoparticles in human foreskin fibroblasts BJ-1-htert and breast carcinoma MCF-7 cells without any transfection reagent is proved by means of confocal laser scanning microscopy.

Stable cellulose nanospheres for cellular uptake.

Pure, perfectly spherical cellulose nanoparticles with sizes of ≈80-260 nm can be prepared by dialysis starting from trimethylsilylcellulose (TMSC). The aqueous suspensions obtained are storable for several months. Subsequent covalent labeling of the cellulose nanoparticles with FITC has no influence on particle size, shape, and stability. The particles can be sterilized and suspended in biological media without structural changes. Incorporation of FITC-labeled cellulose nanoparticles into living human fibroblasts is studied using confocal LSM. In contrast to cellulose nanocrystals, fast cellular uptake is found for the nanospheres without transfection reagents or attachment of a receptor molecule. This suggests an influence of the geometry of biocompatible nanomaterials on endocytosis.

Meltable dextran esters as biocompatible and functional coating materials.

The conversion of dextran with in situ synthesized iminium chlorides of long chain carboxylic acids was used to obtain pure and defined melting dextran esters in an efficient one-pot synthesis. The melting point of these esters can be tailored by the degree of substitutions (DS), the molecular weight of the starting polymer, and the chain length of the ester moiety. The dextran esters give homogeneous and completely transparent melts, which form stable films on a broad variety of materials. Even complex geometries, such as implants, can be evenly coated by multiple melting steps. The films do not display any inhomogeneity and have a very low surface roughness. Therefore, no unspecific protein binding is observed. Moreover, the dextran esters are biocompatible as demonstrated for the interaction with three types of cells namely human brain microvascular endothelial cell, primary human fibroblasts, and mouse myoblast cells.

Suitability of Viability Assays for Testing Biological Effects of Coated Superparamagnetic Nanoparticles

The aim of this study was to establish an in vitro model test system for the analysis of cellular effects of nanoparticles on endothelial cells using the human brain microvascular endothelial cell line HBMEC, a representative of the blood-brain barrier. At first we defined a toxic end point by using superparamagnetic iron oxide nanoparticles coated with cationic substances (polyethylenimine, chitosan, diethylamine ethyl). To study the toxic effects of nanoparticles we evaluated three different viability assays and one cytotoxicity assay for their suitability. We could show that a luminescence-based assay is most promising for an accurate testing, because it is reproducible and unaffected by assay conditions and reagents.

Biocompatible Multishell Architecture for Iron Oxide Nanoparticles

The coating of super-paramagnetic iron oxide nanoparticles (SPIONs) with multiple shells is demonstrated by building a layer assembled from carboxymethyldextran and poly(diallydimethylammonium chloride). Three shells are produced stepwise around aggregates of SPIONs by the formation of a polyelectrolyte complex. A growing particle size from 96 to 327 nm and a zeta potential in the range of +39 to -51 mV are measured. Microscopic techniques such as TEM, SEM, and AFM exemplify the core-shell structures. Magnetic force microscopy and vibrating sample magnetometer measurements confirm the architecture of the multishell particles. Cell culture experiments show that even nanoparticles with three shells are still taken up by cells.

Short‐Term Application of Magnetic Core‐Shell Nanoparticles—Effect on Immune Cells

The effect of magnetic nanoparticles on the survival of leukocytes in general and especially the lymphocytes as important parts of the immune system during incubation and separation was analyzed. Primary leukocytes were inoculated with magnetic core/carboxymethyl‐dextran (CMD) nanoparticles for 4 to 30 minutes. Labelled cells were separated by MACS, counted and analyzed by FACS. T‐Lymphocytes were identified by CD3 and B‐Lymphocytes by CD19. After magnetic separation granulocytes represented the majority of cells in both, the positive and negative fraction. Most of the lymphocytes were detected in the negative fraction. The number of T‐Lymphocytes in the positive fraction increased 2.5‐fold from 4 to 16 minutes, whereas the amount of B‐Lymphocytes remains constant. T cells could be expanded after short‐term incubation with nanoparticles indicating full biological activity. Our enrichment procedure of tumor cells from peripheral blood preserves the integrity and biological activity of leukocytes in the neg...