Remote Optical Modulation of Cellular Electrical Activity Using Two-Dimensional Ti₃C₂ MXene

The ability to probe and manipulate electrophysiology at the cellular level is crucial for understanding cellular communications and enabling new therapeutics for neurological and psychiatric disorders. Nanomaterial-facilitated photothermal stimulation is a non-invasive technique to manipulate cellular electrophysiology with high spatial precision and rapid response time without the need of genetic modifications. Although recently reported Si-, Au-, and C-based nanomaterials are promising candidates for photothermal stimulation of electrically active cells and tissues, they exhibit limited photothermal conversion efficiency in the near-infrared (NIR) window or have complicated synthesis protocols that prevents direct scale-up. Two-dimensional (2D) Ti3C2 MXene is a promising candidate for optical stimulation due to its high NIR absorption and photothermal energy conversion efficiency. Here, we report an approach for optical modulation of neuronal activity using Ti3C2 MXene flakes. Under illumination with 1 ms pulses of 10 mW NIR laser (λ = 808 nm), the local temperature rise induced by single Ti3C2 MXene flakes was measured to be 3.1 ± 0.7 K. MXene films (25 µg/cm2) and dispersed MXene flakes (100 µg/mL) were evaluated to be biocompatible with dorsal root ganglia (DRG) neurons. Both MXene films and flakes enabled photothermal stimulation of DRG neurons (and DRG networks) with incident energies in the micro-joule regime. Optical stimulation of DRG neurons using Ti3C2 MXene flakes is safe and does not generate cellular stress. Due to its straightforward and large-scale synthesis, MXene can enable neuronal modulation at various scales and dimensions, thus is a powerful tool for future remote, non-genetic biological interfaces.