Synthesis of Amphiphilic and Red Emissive Carbon Dots as Nanoprobes for Targeted Stimulated Emission Depletion Imaging of Live Cell Plasma Membranes

The cell plasma membrane, serving as the fundamental barrier separating cells from the extracellular environment, is a complex and dynamic structure that is crucial to cell biology. The super-resolution observation of plasma membrane morphology and dynamics in living cells, facilitated by stimulated emission depletion (STED) microscopy, holds significant importance for advancing the understanding of plasma membrane functions. Due to the photobleaching and unclear target, the development of plasma membrane nanoprobes suitable for STED imaging remains challenging. In this study, we present red fluorescent carbon dots (R-CDs) characterized by amphiphilicity and photostability. As carbon-based nanomaterials, R-CDs exhibit the targeting ability of the cell plasma membrane, resulting in a superior imaging signal-to-noise ratio. Furthermore, R-CDs enable STED imaging of plasma membranes in living cells, achieving a resolution enhancement of at least 3-fold compared to confocal imaging. Leveraging the excellent performance of R-CDs, the dynamic behavior of microstructures such as vesicles on the plasma membrane was successfully observed through time-lapse STED imaging under nanoscale. Hence, R-CDs, as fluorescent nanoprobes with good photostability and biocompatibility, demonstrate significant potential for long-term STED imaging of live-cell plasma membranes and the exploration of plasma membrane dynamics.