Electrically Modulated Drug Delivery using Nanoporous Electrodes
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Electrically Modulated Drug Delivery using Nanoporous Electrodes David B. Robinson,1 Shaun D. Gittard,2 C.-A. Max Wu,1 Cindy M. Ha,1 and Roger J. Narayan2 1 Energy Nanomaterials, Sandia National Laboratories, Livermore, CA, USA. 2 Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA.
ABSTRACT Nanoporous electrodes, such as those made from carbon or gold, can capture and release ionic analytes at concentrations near 1 mole per liter of pore volume through capacitive charging or electrochemically reversible adsorption. In vitro studies suggest that this phenomenon can be the basis for a noninvasive, precise, and programmable drug delivery method. It would eliminate the need for bulk fluid delivery to target tissue and require only a thin electrical connection, minimizing pain and tissue disruption. We have designed effective gold electrode assemblies and observed the depletion and release phenomena using electrochemical methods and charged dyes.
INTRODUCTION Background Orally administered drugs are generally preferred by patients and medical staff due to their ease of administration. However numerous pharmaceuticals, particularly protein and nucleic acid based drugs, are rapidly metabolized by the stomach and liver rendering them impractical for the oral route [1]. Therefore, direct administration of pharmaceuticals into the bloodstream is still a necessity. Injection is the most widely used technique to deliver pharmaceuticals directly into the bloodstream or specific tissue. Nevertheless injection has numerous undesirable properties. Sharp needles pose an injury risk to both patients and medical personnel. While sharps injury rates in the United States are relatively low (0.18 injuries per healthcare worker per year), injury rates in less developed countries can be exceptionally high (up to 4.7 injuries per healthcare worker per year) [2]. Also, pain is commonly associated with injections, and this can be particularly distressing for children. Studies have reported that 8.6% of young adults have a fear of injections [3]. 20% of children are severely distressed by vaccinations [4]. In addition to the obvious goal of improving patient comfort, minimizing pain could also help patient compliance. For example, 8% of patients choose to not receive seasonal influenza immunizations due to the pain associated with the procedure [5]. While needles themselves can cause pain, much of the discomfort from injections is due to the drug itself. Drugs must be administered in dissolved or liquid form in order to be compatible with injection. Injecting fluid into tissue causes swelling, tissue damage, and resultant pain [6]. Accordingly, larger injection volumes result in greater pain [7]. In some cases the pain and tissue damage from injections is caused by solvents or drugs that are irritants, especially lipid soluble molecules [8-10]. This fluid driven tissue damage is why pain from an injection is often
felt over a relatively large area for well after the injection has occurred. In some case
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