Alzheimer drugs incorporated in nanoparticles for specific transport over the blood brain barrier

This is a collaborative project between the Department of Neurology, Medical University of Graz, the national partner JSW Life Sciences and the Institute of Physiological Chemistry and Pathobiochemistry, Molecular Neurodegeneration at the University Medical Centre of the Johannes-Gutenberg-University Mainz, Germany, the Fraunhofer Institute for Biomedical Engineering (IBMT) located in St. Ingbert, Germany, and the Physics Department of the Bar Ilan University, Israel. The objective of the project is to develop novel drug delivery systems based on nanoparticles for the specific transport of Alzheimer disease (AD) drugs over the blood brain barrier (BBB). The research consortium will focus on the establishment of in vitro BBB models to determine the kinetics of receptor-mediated nanoparticle transport. These kinetic data will be instrumental for the use of the in vitro BBB model to transport AD drugs, e.g. non-steroidal anti-inflammatory drugs, loaded onto nanoparticles. After establishing the drug transport we will measure the drug release and the biological activity of the released AD drug in tissue culture models. To identify the transport mechanisms we will investigate the nanoparticle transport on a single cell level and monitor nanoparticle transport using micro-optic techniques. The work package conducted at the Medical University Graz will in addition develop an in vivo approach to follow nanoparticle transport in living animals. We will use MRI which is a well suited tool for tracking these nanoparticles because of its non-invasive nature and its high spatial resolution. Importantly, nanoparticles themselves do not induce intrinsic MR contrast and it will thus be mandatory to label them with paramagnetic particles such as Gadolinium-based compounds, ultra-small paramagnetic iron oxides or super-paramagnetic iron oxides to produce strong contrast. Imaging will be done serially and we will use non-toxic compounds that have also been used in clinical settings. All paramagnetic labelling schemes will be tested in cross-linked bovine serum albumin (BSA) gel which ideally mimics relaxation behaviour of brain tissue in terms of T1 and T2 relaxation times. Embedding different volumes and concentrations of labeled nanoparticles in the gel will allow the assessment of the T1 and T2 relaxivity as well as susceptibility effects. The latter will be assessed by quantitative T2 * mapping and by phase imaging. Quantitation of the susceptibility and relaxivity effects of the labelled nanoparticles will help to optimize the imaging sequences for nanoparticle tracking in mice. These sequences will allow to estimate nanoparticle concentration in different brain regions from changes in T2 * and phase values. For tracking the nanoparticles in time and space in the transgenic mouse model, an optimized scanning protocol will be used to investigate the animals prior to treatment, directly after first treatment, and at months 2, 4, and 6. Serial measurements will allow the study of the dynamics of labelled nanoparticles with respect to local distribution and accumulation over time. We will also study using diffusion tensor and magnetization transfer imaging the microstructural tissue changes in gray and white matter structures that may have been induced by the nanoparticel-bound gamma-secretase modulator.

Alzheimers disease (AD) is the most common form of dementia and the most frequent age related neurodegenerative disease. More than 30 million people are affected while there is still no cure for AD. It is commonly believed that some new therapeutic concepts have failed because the drugs could not cross the blood-brain-barrier (BBB) in a therapeutic relevant concentration. This was not entirely unexpected, because the role of the BBB is to act as a shield that protects the brain from harmful substances from the bloodstream which is achieved by the selectivity of tight junctions between endothelia cells. The goal of the collaborative project was to develop nanoparticles (NP) with a size of a few hundred nanometers that can actively transport drugs over the BBB. Magnetic resonance imaging (MRI) is the most promising method to trace these NP noninvasively and to prove the accumulation of NP in the parenchyma of the brain. However, while normal brain tissue provides excellent contrast in MRI, NP do not intrinsically induce MRI contrast. The goal of the subproject therefore was to develop and test new labeling schemes which make drug loaded NP visible for MRI. During the course of the sub-project, several labeling schemes where tested where best results were found for ultra-small iron oxide particles (Magnetite) which are traceable by MRI even with low concentrations due to their strong paramagnetic effect. In in-vivo experiments in adult rats we administered human serums albumin (HSA) based NP (developed by our partners) with iron oxide labeling and we could clearly demonstrate that among other organs NP also accumulated in the brain. While concentration levels in the brain were moderate, global detection was nevertheless possible because of the development of a very sensitive histogram based analysis tool. MRI findings were validated with results from autofluorescence imaging following brain extraction. The outcome of this study provides a solid basis for further research in this direction. It is expected that NP accumulation in the brain can be enhanced through vectorization by activation of specific receptors such that therapeutic relevant concentrations can be achieved. A specific feature in this sub-project was the utilization of a clinical MRI scanner which operates at a significantly lower field strength than animal systems. The benefit is that all sequences and analysis tools developed in the frame work of the subproject are now available for future translational studies in humans.