In Vivo Solute Diffusivity in Brain Tissue Surrounding Indwelling Neural Implants

In this chapter we describe an analytical approach that can be used to study solute diffusivity as a function of the tissue composition surrounding a device implanted in normal, aged, damaged, or diseased brain. The method is capable of resolving changes in solute diffusivity and cellular composition at the scale of a few microns. In this chapter we describe the key features of the method including a quantitative imaging and modeling approach that can be used to assess extracellular diffusion surrounding a model implant, and we illustrate how the approach can be used to study the influence of living cells on tissue remodeling and solute transport. Available evidence suggests that the approach may be useful in sorting out the intricacy of the foreign body response, as well as examining how soluble factors released from various types of transplanted cells affect brain tissue remodeling and regional regeneration in the central nervous system.