Organic Light Emitting Diodes (OLEDs) for Neuro-optoelectronics

Fluorescence imaging (e.g. Fluorescence imaging (e.g. fluorescent proteins), optical detection (e.g. biosensors), and opsin based neuromodulation (e.g. optogenetics) are the major techniques that have changed the practice of neuroscience. All these techniques use arc lamps, Light Emitting Diodes (LEDs) and lasers as conventional light sources. However, these light sources are not biocompatible and are excessively bulky, which limits their effectiveness as brain implants. Many improvements are necessary, such as the development of appropriate alternative light sources integrated with biological cells to ensure their compatibility with established techniques in biological laboratories. Organic Light Emitting Diodes (OLEDs) combine optical and electrical properties with known advantages of customized materials providing appropriate color tunability, lightness, and low-cost solution processing. In addition, mechanical flexibility combined with the high elastic modulus and biological inertness of carbon-based polymers and nanomaterials confer major advantages for use in non-conformal body cavities. These attractive and innovative qualities of OLEDs make them an alternative and better light source for organic neuro-optoelectronics. However, engineering optoelectronic devices for operation in liquid environments requires a comprehensive understanding of the consequences that may arise. This research is innovative in designing and engineering stable and biocompatible OLEDs for incorporation into living tissues. As a result, organic LEDs do not have to alter cell morphology and electrophysiological integrity/function. The principal challenge is ensuring they can operate in a highly saline and biologically active aqueous environment. Finding materials that are inherently stable in the environment in which they function is key to device optimization. The research will investigate the stability and biocompatibility of commonly used OLED materials. Key electrodes, indium, tin, oxide, gold, aluminum and silver are characterized to examine their suitability for an aqueous environment. [1,2] Treating organic light emitting polymers with laminin has shown enhanced cell adhesion and biocompatibility. Prolonged immersion in cell culture medium highlights the importance of cross-linkable polymers maintaining electrical, optical and morphological properties. These properties are critical to device performance. Insulator materials play complementary and necessary roles at the interface of the OLED/bio environment – ensuring the protection of the device against oxidative or reductive processes. Insulators are critical for extending the lifetime of devices in aqueous operation. They must be encapsulated with hydrophobic polymers for protection against neuron damage from electrical stimulation. Following from the above it becomes possible to design both a highly biocompatible prototype OLED device, which is suitable for fluorescence microscopy, and patch-clamp technique for electrophysiological investigations. This would be based on opsin activation and would also include the investigation of critical design parameters for efficient OLED-opsin coupling stimulation. Additionally, OLED devices have been investigated for in vivo optical imaging of functional cortical architecture and dynamics.Open Acces