Development and optimization of quantum dot-neuron interfaces

Micron-scale neuroelectronic interfaces have been used as laboratory models in neuroscience, prosthetic devices, and components of computational systems. However, these devices interact with cells at the whole cell level, and cell signaling occurs through interactions with cell surface proteins that average 10 nm in size. To take advantage of these receptor-scale interactions additional systems are needed. We have designed and optimized one possible system, using semiconductor quantum dots. Quantum dots are crystalline particles, typically less than 10 nm in diameter, that display many unique optical and electronic properties because of quantum confinement of the exciton. As a result, they have been used in a number of optoelectronic and biological applications. Our research attempts to combine these functionalities to create an optically excited interface capable of electrically communicating with nerve cells. To achieve this goal, we manufactured CdS quantum dots using an aqueous synthesis. We characterized the effects of altered synthesis conditions on the size and quantum yield of the particles, indicators of their electrical properties. We then demonstrated three separate methods to produce quantum dot-neuron interfaces. The first of these utilizes biorecognition molecules, including antibodies and peptides, to create controlled interfaces with cell membrane receptors. The second method uses non-specific interactions between the particle core and cell membrane surfaces to create diffuse binding, and the third technique provides interfacing through direct culture of cells on tethered films. Additionally, we present our initial attempts to incorporate these interfaces with existing micron-scale measurement technologies, which could be used to confirm quantum dot-neuron electrical connectivity. Our results, demonstrate one possible path to receptor-scale neuroelectronic interfacing. Ultimately, these devices could be incorporated into existing micron-scale systems to provide new classes of prosthetics and computational devices.