Delivering Growth Factors
It is also challenging to deliver growth factors to the central nervous system, because most proteins are not able to cross the blood–brain barrier and therefore, cannot be delivery via systemic administration. The most desirable method of delivering growth factors such as nerve growth factor is locally because then only nanogram quantities are needed to supply therapeutic levels to the targeted cell population. A controlled delivery system is needed in order to supply growth factor locally. Another drug delivery system that has been well characterized is poly(ethylene-co-vinyl acetate) (EVAc). EVAc matrices have been approved for use the Food and Drug Administration. Protein release occurs mainly by diffusion, which can be regulated by changing the mass within the polymer matrix. In order to better determine appropriate dosages from EVAc matrices, a study was done to determine how cell density and cell type affect the rate at which a delivered protein is eliminated; NGF was released into PC12 and developing fetal brain cells distributed throughout collagen gels. It was found that both the cell type and the cell density affected the rate of NGF elimination from the gels, suggesting that elimination is a cell-mediated process. The results were compared to a model that was developed to predict the effects of cell type and density on elimination. One specific reason for differences between the data and the model predictions could be because the model does not account for the change increases in cell number due to replication. This study is important for enhancing the ability to accurate deliver the desired dosage to the target tissue based on the amount of growth factor initially in the delivery matrices.
Read more about this topic: Neural Drug Delivery Systems
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