Upconversion Nanoparticle-Delivery Flexible Optrodes for Long-Lasting Multichannel Electrophysiology and Transcranial NIR Optogenetics.

Near-infrared (NIR) activatable nanoparticles enable remote, cell-type-specific manipulation of neuronal activity, whereas flexible microelectrode arrays (FMAs) facilitate long-term, multichannel recording of neural signals. Despite the recent development of multifunctional neural probes, integrating these techniques into a single, minimally invasive device remains challenging. Here, we present a novel optrode that combines NIR-activatable upconversion nanoparticles (UCNPs) with FMAs. The UCNPs and FMAs are coencapsulated in a nanoliter-scale polymer carrier and delivered into the same brain regions through a single surgery, ensuring highly spatial congruence between the manipulated and recorded neuronal populations. Chronically implanted devices enable simultaneous multichannel recording and transcranial modulation of opsin-defined neuronal populations over extended periods. The flexibility and minimal invasiveness of our optrodes provide a powerful tool for the long-term and spatially precise interrogation of neural circuit functions.