Research Interests
Publications and Patents
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The only conclusion that can be drawn from evaluating the first 15 years of research efforts related to endothelial cell seeding techniques is that few concrete technical advancements have been made. This changed with the introduction of a novel device and methodology that has been shown to have potential in terms of value improving the efficiency of seeded endothelial cell attachment as well as minimizing cellular losses upon implantation. The technique is called electrostatic endothelial cell seeding. The electrostatic seeding technique has been evaluated in vitro and in vivo using the prototype apparatus shown in Figure 1. The key to this technique is that it enhances endothelial cell adhesion by inducing a temporary positive surface charge or a "temporary glue" on the negatively charged e-PTFE graft luminal surface. Following cell transplantation the e-PTFE graft luminal surface reverts to its original highly negative charged surface. Thus, any non-endothelialized graft surfaces or any exposed graft surfaces resultant from endothelial cell losses upon restoration of blood flow remain non-thrombogenic due to the restored high negative surface charge of the graft material itself. The basic issue underlying tradition endothelial cell seeding techniques that is overcome by the electrostatic endothelial cell seeding is - "How can the surface potential of the graft be altered to attract endothelial cells without rendering the surface thrombogenic?" The electrostatic endothelial cell seeding technique takes advantage of graft material properties (dielectric material). When a dielectric material is placed within a capacitor (electrostatic seeding apparatus), the electrons of the atoms and ions which make up the dielectric material (near surface) are attracted to the capacitor surface which has accumulated the positive charge. The nuclei of the dielectric material (near surface) are attracted to the negatively charged surface. These small displacements, or polarizations, are what induces the surface charge or "temporary glue" on the graft luminal surface. It should be noted that the electrons in a dielectric material are not free, no current carrying capacity due to being an insulating material, and the displacements of the electrons are very slight. Also, the interior volume of the graft material, dielectric, remains unchanged thus, leaving a net charge of zero over the dielectric material.
Cut-away (side view) schematic of the electrostatic endothelial cell transplantation device to illustrate the placement of the voltage calibrator leads and graft within the external conductor.
Photograph of the complete electrostatic endothelial cell transplantation prototype apparatus showing the external conductor, filling apparatus (with internal conductor), pillow blocks, voltage calibrator, and electric motor drive system (Overall length of prototype apparatus is 30.5 cm).
Scanning electron micrograph illustrating the optimum electrostatic endothelial cell seeding (+1.0 V/16 minutes) onto e-PTFE (GORE-TEX). This figure demonstrates the morphological maturation (degree of flattening) and the complete cellular coverage (adhesion) on the e-PTFE nodal areas (x 750 magnification). |
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