3D real-time single particle tracking using two-photon fluorescence from bright dye-based organic nanoparticles†

This paper addresses the use of ultrabright dye-based fluorescent organic nanoparticles in a 3D single-particle tracking two-photon microscopy setup. The nanoparticles consist of an assembly of quadrupolar dyes, presenting a large two-photon absorption cross-section. They exhibit low photobleaching, crucial for long-term tracking, and their high brightness allows nanometer localization precision. Their small size compared to previously used nonlinear inorganic nanocrystals, stable structure at physiological temperature, and adjustable optical properties make them promising tools for further biological research. This study highlights their potential to track dynamic processes with precision and stability, paving the way for exploring cellular processes at the nanoscale.