Metal-Organic Frameworks Modified Organic Bulk Heterojunction Interfaces for Effective Nongenetic Neuromodulation

Photoactive organic semiconductors, such as bulk heterojunctions (BHJs) of donor-acceptor pairs, are promising for building flexible devices for nongenetic and precise optical neuromodulation. However, the full potential of the diverse compositions and functionalities of BHJs has yet to be explored for neuromodulation due to their unsatisfactory interfaces with soft biotissues, which hinder signal transduction, tissue adhesion, and biocompatibility. Here, we address these challenges by introducing an interfacial layer composed of conductive and porous metal-organic frameworks (MOFs). The MOFs layer enhances charge injection capacity at the interface by >400 times and ensures tight and biocompatible junction between BHJs and biological materials. These improvements enable efficient electrical-to-ionic signal transduction for various BHJs, supporting reliable nongenetic modulation of cultured mouse hippocampal neurons under deep-red and near-infrared light. Moreover, flexible devices made from MOFs-modified BHJs allow for the in vivo stimulation of rat sciatic nerves at an ultralow light intensity threshold (0.01 mW mm^-2), 700 times lower than that required for unmodified devices. This interfacial engineering with porous MOFs can expand the material toolbox of BHJs-based photocapacitors and unlock more functionalities for neuromodulation and prosthetic biointerfaces.