W. Wan, A. Li
Washington State Universoty,
Keywords: photoswitch, nanoparticles, imaging, fluorescence
Summary:Nanoparticles have evolved to be the carriers of multiple technologies, which garnished unprecedented power in molecular imaging. For example in bioimaging, a single fluorescent probe is usually lost in the ocean of myriad other molecules in a living cell, thus unambiguously measuring its signal becomes a daunting task because the signal is typically flooded with interferences and noises generated by the matrix. When photoswitchable nanoparticles are used, however, the oscillating signal can be selectively amplified in an unlimited manner and effectively measured after sufficient photoswitching cycles are completed. Here we show that photoswitchable nanoparticles containing photoactive spiropyran-merocyanine could be imaged not only in time domain (like most fluorescent probes), but also in frequency domain (unlike most fluorescent probes). Applying frequency-domain imaging (FDI) to biological applications, we have clearly detected, monitored, and tracked photoswitchabe probes in living cells over the matrix of overwhelming non-switching fluorescence interferences. Therefore, FDI reveals molecular behavior that is not visible or measurable in real-time fluorescence imaging, thus a powerful tool in biomolecular imaging.