(115b) Label-Free Optical Electrophysiology Using Electrochromic Materials

Understanding how a network of neurons receive, store and process information in the human brain is a grand scientific challenge of our time. Neurons encode and communicate information through electrical signals. Traditional electrode-based recording methods such as patch clamp or multielectrode arrays are either highly invasive to cells or inflexible to sense electrical fields of cells at user-selected spatial positions with limited recording capacity. Existing optical methods, on the other hand, rely heavily on inserting voltage-sensitive fluorescent molecules into the cell membrane, which suffer from cell phototoxicity, limited recording duration and signal-to-noise ratio due to photobleaching.

Here, we develop ElectroChromic Optical REcording (ECORE), a new electrophysiology method that optically reads out the electrical activity of electrogenic cells in a label-free, parallel, and non-perturbative manner. The ECORE method fundamentally differs from any existing voltage recording approaches in that cell electrical signals are read out optically through voltage-sensitive optical absorption of electrochromic thin films. Cell electrical signals could modulate the optical absorption of the electrochromic thin film. Changes in optical reflection of the film, rather than fluorescence, are then detected to probe cell electrical activities through our home-engineered optical system with a high signal-to-noise ratio. In this way, ECORE does not perturb the physiology of cells without the insertion of any molecular probes. It is also not limited by photobleaching or phototoxicity, making it a suitable tool for long-term recording of cell electrical signals over weeks or months. Using ECORE, we have demonstrated multi-channel parallel recording of the electrical signals of cardiomyocytes, neurons, and brain slices cultured on electrochromic PEDOT:PSS thin films with high sensitivity and throughput.