This is a proposal to develop synthetic magnetic constructs for gene delivery to normal and abnormal neurons and glial cells, and is thus most directly relevant to gene therapy of neurologic diseases. The work will cover two specific areas: 1) the synthesis or construction of artificial neurotropic gene delivery systems and 2) the quantitation of gene delivery to the CNS in rat models in vivo by MR imaging. It has been shown previously that artificial viral sized 512B dextran particles are efficiently internalized by neurons and glial cells. It has now been shown that DNA vectors can be bound to magnetic and non-magnetic dextran particles such as 512B dextran-superparamagnetic iron oxide particles and 512B dextran-poly-L-lysine copolymers, and that these constructs lead to expression of the marker gene both in cell culture and in vivo. The synthesis of model gene delivery constructs will be optimized, the efficacy of the optimized constructs will be compared in transfecting cells in culture. The mechanisms of neuronal uptake and intracellular metabolism will be investigated, and the toxicity of the artificial constructs will be compared to the toxicity of recombinant viruses. This study will extend previous work that showed that high-resolution MR imaging can be used to quantitate delivery of superparamagnetic constructs in the central nervous system (CNS) in that it is proposed to image gene delivery (distribution maps, local concentration) to the CNS in vivo in rat models. MR imaging data will be assessed for changes in signal-to-noise, length of signal changes, threshold of detectability and accuracy of MR mapping using histopathological correlates.
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