(683b) Dye-Conjugated Dendrimers As Bright and Photostable Nanoprobes for Fluorescence Microscopy

We demonstrate dye-conjugated dendrimers as nanoscale imaging probes for high-resolution fluorescence microscopy. Fluorescence-based imaging techniques currently rely on a limited set of fluorescent probes, including fluorescent proteins, organic dyes and quantum dots. However, there is a strong need for development of bright and photostable nanoprobes to enable biological imaging with enhanced spatiotemporal resolution. Recent advances in single molecule fluorescence microscopy have broken the diffraction barrier for optical imaging, thereby enabling observation of biological processes at nanometer-scale resolution. Super-resolution imaging techniques such as photoactivated localization microscopy (PALM)and stochastic optical reconstruction microscopy (STORM) rely on either photoactivable fluorescent dye or fluorescent proteins and photoswitchable organic dyes. However, the performance of these super-resolution imaging techniques is limited by the photophysical properties of the current set of fluorescent probes.

In this work, we use dye-conjugated dendrimers as a new class of nanoprobes for fluorescence microscopy, which enables high-resolution fluorescence imaging. Generation-5 polyamidoamine (PAMAM) dendrimers were engineered to contain sets of multiple cyanine dyes, and the photophysical properties were characterized by single molecule fluorescence microscopy using total internal reflection microscopy (TIRF-M). We observed that collective effects in the multichromophoric nanoprobe system result in highly extended photobleaching lifetimes and enhanced localization precision compared to single organic dyes such as Cy5. In addition, we engineered photoswitchable dye-conjugated dendrimers as enhanced nanoprobes for super-resolution imaging. Dye-conjugated dendrimers are bright, photostable and nanometer-sized macromolecular probes that can be synthesized to contain a variety of surface chemical functionalities for biological labeling and imaging. Based on these advantages, we anticipate that dye-conjugated dendrimers will pervasive application as a new class of nanoprobes for fluorescence microscopy.