Electron microscopic analysis of nanoparticles delivering thioflavin-T after intrahippocampal injection in mouse: implications for targeting beta-amyloid in Alzheimer's disease.

Prevention of beta-amyloid (Abeta) production, aggregation and formation of Abeta deposits is a key pharmacological target in Alzheimer's disease. The passage of Abeta-binding compounds through the blood-brain barrier is often hampered for free ligands, whereas it is enhanced by drug encapsulation in nanoparticles. Here, we describe the preparation and characterization of polymeric carriers containing thioflavin-T as a marker for fibrillar Abeta. This study is then focused on electron microscopic analyses of thioflavin-T after injection of thioflavin-T-containing nanoparticles into the mouse hippocampus. Therefore, the photoconversion of fluorescent thioflavin-T as model drug was performed in tissues fixed 3 days post-injection. Thioflavin-T delivered from nanospheres was predominantly found in neurons and microglia. Our data suggest that drugs delivered by nanoparticles might target Abeta in the brain.

99mTc labelled model drug carriers - labeling, stability and organ distribution in rats.

The surface characteristics of intravenously administered particulate drug carriers decisively influence the protein adsorption that is regarded as a key factor for the in vivo fate of the carriers. We labeled surface-modified polymer particles with the gamma-emitting radioisotope 99mTc in order to test their properties in blood and follow their in vivo fate. The biodistribution was different in various types of polymer particles. As expected, labeled particles were found in the mononuclear phagocyte system in a large scale but markedly different biodistribution for some particles were also shown.

Functional groups on polystyrene model nanoparticles: influence on protein adsorption.

The surface characteristics of intravenously administered particulate drug carriers decisively influence the protein adsorption that is regarded as a key factor for the in vivo fate of the carriers. Latex nanoparticles were synthesized to study the influence of different basic and acidic functional groups on particulate surfaces on the protein adsorption from human serum. The protein mass adsorbed to the particles was assessed by BCA protein assay, the protein adsorption patterns were analyzed by two-dimensional electrophoresis. Considerable differences in the protein adsorption with regard to preferential adsorbed proteins were detectable for the different functional groups. Possible correlations between the surface characteristics and the protein adsorption are shown and discussed. The knowledge concerning the interactions of proteins and nanoparticles can be used for a rational development of particulate drug carriers and can also be useful for an optimized design of medical devices, e.g., hemodialysis membranes or implants.

Structural aspects of histone H1-DNA complexes and their relation to transfection efficiency.

During transfection, polycation-DNA complexes are normally diluted by the transfection medium, which often contains salt in the physiological concentration range and serum. It is not exactly known to what extent this dilution step influences the properties of the complexes, which in turn influence the transfection efficiency. In order to gain more insight into the size-structure-transfection activity relationship, we prepared histone H1-DNA complexes in NaCl solutions at various concentrations known to determine the size and structure of the resulting complexes. We characterized the complexes by physicochemical methods. Fluorescence correlation spectroscopy enabled relative measurements of complex sizes even under physiological conditions. The different appearances of the complexes were correlated with their transfection efficiency. When transfection was performed by dilution of the complexes in cell-cultivation media, the initial structure of H1-DNA complexes preformed under distinct salt conditions had no significant influence on the transfection efficiency. The dilution of the preformed complexes with cell-cultivation medium resulted in re-formation and aggregation of the complexes. The addition of the complexes to the cells without cell-cultivation medium, however, showed a direct correlation between the size of the complexes and the transfection efficiency (correlation coefficient 0.91). Small complexes did not contribute to the transfection.