Advances in optical recording techniques for non-invasive monitoring of electrophysiological signals

The study of electrophysiological signals is crucial for understanding neural functions and physiological processes. Electrophysiological recordings offer direct insights into electrical activity across cellular membranes, aiding in diagnosing and treating neurological disorders. Different from the conventional recording method based on electrical signals and the genetically encoded with fluorescent proteins methods, this review explores label-free mechanisms for optically recording electrophysiological signals: electrochromic materials, surface plasmon resonance (SPR) responses, quantum dots (QDs), and semiconductor-based optoelectronic sensors. The sophistication and limitations of each technology have been discussed, providing insights into potential future directions in this field. Electrochromic materials change optical properties through redox reactions induced by voltages, offering high signal-to-noise ratios and rapid response capabilities. However, these materials have limited biocompatibility and stability. SPR technology modulates signals in response to local changes in electrical potential, achieving high sensitivity. However, challenges such as scattering noise and electro-optic effects still need to be addressed. QDs utilize their photoluminescent properties for high sensitivity and resolution, but concerns about connection efficiency and biocompatibility remain. Semiconductor optoelectronic technologies offer rapid response times, wireless functionality, and integration potential. However, improvements are needed in terms of toxicity, compatibility with biological tissues, and signal amplification and processing. These methods have advantages in neuroscience, medical diagnostics, and biological research, including rapid response, high sensitivity, and label-free monitoring. By combining different optical recording techniques, the performance of voltage imaging can be optimized. In conclusion, interdisciplinary collaboration and innovation are essential for advancing the optical recording of electrophysiological signals and developing diagnostic and therapeutic approaches.