Carbon nanotubes allow for significant electrode performance in biological applications, and can serve as nanosyringes for drug eution all while preventing major scarring and delivering therapeutic agents.
Background: Microelectrode arrays (MEAs) are neural interfaces that connect neurons to electronic circuitry and include implantable interfaces such as deep brain stimulators, cochlear implants, and cardiac pacemakers. Research suggests that MEAs provide insight into memory function and perception, and therapeutic value for conditions such as epilepsy, depression, and obsessive compulsive disorder (OCD). MEAs can record activity from multiple neurons simultaneously, but electrode implantation can cause chronic inflammation, glial scarring, neuronal cell loss, and a decrease in axonal growth. Current metallic electrode arrays are too large in diameter for applications requiring biocompatibility, which may result in glial scarring at the electrode penetration site leading to decreased performance over time and complete neural degeneration. Attempts to create smaller electrode arrays have failed due to the high aspect ratio that leads to buckling during insertion through various tissue layers.
Technology: Jud Ready from the Georgia Tech Research Institute has developed a carbon nanotube (CNT) array to provide electrical stimulation and read-out electrodes for drug-eluting nano-channel neuronal interfaces. A densified array of CNT towers form spikes for use as electrically conductive neural probes. A lithographic pattern technique is used to create toroidal syringes and inductively coupled plasma is used to micromachine the underlying Si substrate with fluid delivery channels. This results in CNT arrays composed of densely packed CNT “vines” which allow weepage of the drug from the sidewalls of the array for better bio-incorporation.
Potential Commercial Applications: CNTs can be functionized with peptides and other biological compounds to promote neuronal growth and adhesion between the electrode and biologic tissues. This allows for significantly enhanced electrode performance in both stimulation and read-out of neuronal signals. The array can be coupled with nano/microfluids to serve as “nanosyringes” for drug elution. Most metal or doped-Si neural probes do not allow for drug delivery, and those that can deliver drugs only elute from the syringe tip. This method prevents glial scarring, promotes neuronal growth, and delivers therapeutic agents while coupled to an electrode array. The inherent mechanical stiffness of CNTs prevents the buckling occurring with other high-aspect ratio probe systems. With their high conductivity, CNTs provide comparable electrical performance to metallic and doped-Si arrays.
Benefits / Advantages:
Densely packed CNT arrays allow for better bio-incorporation, prevention of glial scarring, chronic inflammation, and neuronal cell loss
Readily functionalized to promote neuronal growth and tissue-electrode adhesion, enhancing electrode performance and quality of read-out signals
Inherent mechanical stiffness enhances the rigidity of adjacent CNTs preventing buckling as in other high-aspect probe systems
W. Jud Ready- Deputy Director of the Institute for Materials, Principal Research Engineer at the Georgia Tech Research Institute, and Adjunct Professor for the School of Materials Science & Engineering- Georgia Tech School of Materials Science and Engineering, Georgia Tech Research Institute