Organic Semiconducting Probes for Super-resolution Imaging and In Vivo Imaging

In this presentation, I will present several new types of polymer dots (Pdot) for optical imaging. The hydrophobic semiconductor polymers tend to form small, stable and densely-packed Pdots. The large absorption cross section, high fluorescence quantum yields, and good biocompatibility are promising for biological imaging in vitro and in vivo. We showed that the small photoblinking Pdots are able to image subcellular structures that breaks the optical diffraction limit. We further report two types of BODIPY-based polymer dots (Pdots) with narrow-band emission, pronounced fluctuations, and prominent photostability, thus enabling high-order, dual color SOFI nanoscopy. Single-particle and subcellular SOFI analysis reveals the superior performance of the BODIPY Pdots as compared to conventional Alexa dye labeled antibodies. In contrast with wide-field images, the spatial resolution (∼57 nm) is enhanced by ∼6.0-fold in 8th-order single-particle SOFI nanoscopy. A final spatial resolution (∼30 nm) was obtained by using multifunctional Pdots, high-order SOFI analysis, together with expansion microscopy. For in vivo imaging, we show that an ultrasensitive optical transducer can be used for wireless glucose monitoring via a smartphone. The optical transducer combines oxygen-sensitive polymer dots (Pdots) with glucose oxidase that sensitively detect glucose when oxygen is consumed in the glucose oxidation reaction. By judicious design of the Pdots with ultralong phosphorescence lifetime, the transducer exhibited a significantly enhanced sensitivity by one order of magnitude as compared to the one in a previous study. As a result, the optical images of subcutaneous glucose level obtained with the smartphone camera could be utilized to clearly distinguish between euglycemia and hyperglycemia. We finally describe NIR-II fluorescent Pdots for high contrast in vivo brain vascular imaging. By performing through-skull and through-scalp imaging of the brain vasculature of live mice, we quantitatively analyzed the vascular morphology of transgenic brain tumors in terms of the vessel lengths, vessel branches, and vessel symmetry, which showed statistically significant differences from the wild type animals. The bright NIR-II Pdots obtained through fluorination chemistry provide insightful information for precise diagnosis of the malignancy of the brain tumor.