Fluorescent Polymer Dot-Based Multicolor Stimulated Emission Depletion Nanoscopy with a Single Laser Beam Pair for Cellular Tracking.

Stimulated emission depletion (STED) nanoscopy provides subdiffraction resolution while preserving the benefits of fluorescence confocal microscopy in live-cell imaging. However, there are several challenges for multicolor STED nanoscopy, including sophisticated microscopy architectures, fast photobleaching, and cross talk of fluorescent probes. Here, we introduce two types of nanoscale fluorescent semiconducting polymer dots (Pdots) with different emission wavelengths: CNPPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylene-1,4-phenylene)]) Pdots and PDFDP (poly[{9,9-dihexyl-2,7-bis(1-cyanovinylene)fluorene}-alt-co-{2,5-bis (N,N'-diphenylamino)-1,4-phenylene}]) Pdots, for dual-color STED bioimaging and cellular tracking. Besides bright fluorescence, strong photostability, and easy bioconjugation, these Pdots have large Stokes shifts, which make it possible to share both excitation and depletion beams, thus requiring only a single pair of laser beams for the dual-color STED imaging. Long-term tracking of cellular organelles by the Pdots has been achieved in living cells, and the dynamic interaction of endosomes derived from clathrin-mediated and caveolae-mediated endocytic pathways has been monitored for the first time to propose their interaction models. These results demonstrate the promise of Pdots as excellent probes for live-cell multicolor STED nanoscopy.

Adjustable and ultrafast light-cured hyaluronic acid hydrogel: promoting biocompatibility and cell growth.

Bio-sourced hydrogels are attractive materials for diagnosing, repairing and improving the function of human tissues and organs. However, their mechanical strength decreases with an increase in water content. Furthermore, it is challenging to mold these hydrogels with high precision, which significantly limits their applications. Herein, we modified a biocompatible and biodegradable material, hyaluronic acid, with methacrylic anhydride and then cured it with a four-arm star structure cross-linking agent under ultraviolet light. The hyaluronic acid hydrogel was finally cured within 15 s with an adjustable cross-linking degree. The results demonstrated that the developed gel maintained good mechanical strength with a water content of 90%, while achieving micropatterns at a precision of 20 µm. The biological experiments showed that it could effectively promote the release of vascular endothelial growth factor (VEGF), which contributed to promoting cell growth, and has favorable biocompatibility. Overall, this hyaluronic acid hydrogel is a promising biomedical material with high forming accuracy, excellent mechanical properties, and favorable biocompatibility, which indicate its potential value in a variety of tissue engineering and biomedical applications.