Programmable Transdermal Drug Delivery of Nicotine using Carbon Nanotube Membranes

Carbon nanotubes (CNTs) have three key attributes that make them of great inter-est for novel applications such as programmed drug delivery: (1) atomically flat graphite surface allows for ideal fluid slip boundary conditions; (2) the cutting process to open CNTs inherently places functional chemistry at CNT core entrance; and (3) CNT are electrically conductive allowing for electrochemical reactions and applica-tion of electric fields gradients at CNT tips. Towards this goal, a composite membrane structure containing vertically aligned carbon nanotubes passing across a poly-styrene matrix film have been fabricated [Science 2004]. Pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 orders of mag-nitude faster than conventional Newtonian flow due to atomically flat graphite planes inducing nearly ideal slip conditions [Nature 2005]. These properties are nearly ideal for introducing efficient electro-phoretic and electro-osmotic flow to be used as the basis of a programmed transdermal delivery device. CNT tips are functionalized with a high density of negative charge allowing the unidirectional flow of positive cations under small bias, thus inducing an efficient flux of neutral molecules. Efficiencies as high as 1 neutral molecule per ion are seen in the small CNT pores, allowing stan-dard watch batteries to operate for 40 days. An in-vitro cell, composed of a reference electrode, reservoir solution, CNT membrane electrode, gel contact and human skin sample were assembled in a Franz cell. A differential model of diffusion in series (reservoir/CNT/gel/skin) explained observed dosage profile. Therapeutically useful fluxes for Nicotine treatment were controllably switched between, with 0.56 and 2.0 micromole/cm2-hr at 0mV and -600mV respectively.