Great strides have recently been made in using implanted electrodes to directly stimulate the cochlea, visual cortex, peripheral nerves, and other aspects of the human nervous system. Thus the electrodes interaction with the surrounding tissue is an important issue in its function. The surface of these electrode materials plays a key role in determining the body's response to the implanted electrode. Conventional materials can provoke an inflammation response that can be both painful and detrimental to the patient. Methods of altering this response include rendering the surface more inert, making it invisible to the immune system, or actively signaling the body to incorporate the implant. We will apply a novel method of changing the surfaces to make them more acceptable to the body with surface analytical methods to quantitate these changes. We will use self-assembled monolayers (SAMs) to modify the exposed surfaces of implanted electrodes in an attempt to make them more biocompatible. We will take advantage of the different chemical composites of a typical electrode, i.e., insulator and metal, to react two different monolayers to these surfaces. We will culture hippocampal and spinal cord neurons in serum-free and serum-containing media and determine the cells' response to the SAM-modified surface. We have previously shown that we can enhance or retard the growth of hippocampal and spinal cord neurons by modifying surfaces with different SAMs. We will quantitate the surface composition both before and after cell culture using X-ray Photoelectron Spectroscopy, Auger Electron Spectroscopy, ellipsometry, and contact angle measurements. The goal of this research is not lust to make the composite surface biocompatible, but to enhance its interaction with the surrounding tissue. We will also use monolayers of biological macromolecules attached to SAMs to recruit neurons for closer proximity to the electrodes. An understanding of basic cell-surface and tissue-surface interactions has a great many implications for the rehabilitation of impaired or disabled people. Issues we hope to address include chronic pain due to the development of inflammation and scar tissue around electrode implants, insights into the role of the surface in cell culture, as well as the incorporation of implanted electrodes in the body.
| Schaffner, A E; Barker, J L; Stenger, D A et al. (1995) Investigation of the factors necessary for growth of hippocampal neurons in a defined system. J Neurosci Methods 62:111-9 |
