Multicolor Photo‐Crosslinkable AIEgens toward Compact Nanodots for Subcellular Imaging and STED Nanoscopy

Abstract

Aggregation induced emission (AIE) has attracted considerable interest for the development of fluorescence probes. However, controlling the bioconjugation and cellular labeling of AIE dots is a challenging problem. Here, this study reports a general approach for preparing small and bioconjugated AIE dots for specific labeling of cellular targets. The strategy is based on the synthesis of oxetane-substituted AIEgens to generate compact and ultrastable AIE dots via photo-crosslinking. A small amount of polymer enriched with oxetane groups is cocondensed with most of the AIEgens to functionalize the nanodot surface for subsequent streptavidin bioconjugation. Due to their small sizes, good stability, and surface functionalization, the cell-surface markers and subcellular structures are specifically labeled by the AIE dot bioconjugates. Remarkably, stimulated emission depletion imaging with AIE dots is achieved for the first time, and the spatial resolution is significantly enhanced to ≈95 nm. This study provides a general approach for small functional molecules for preparing small sized and ultrastable nanodots.

Unity Makes Strength: How Aggregation‐Induced Emission Luminogens Advance the Biomedical Field

“…C) Comparison of confocal image (left) and STED image (middle) of the microtubule structures labeled by the A12 dots (80 µg mL −1 , 10 µL) and the line profile of the position indicated by the arrow heads (ii) in the images. Adapted with permission . Copyright 2017, Wiley‐VCH.…”

“…Microtubules exist in the cytoplasm of all eukaryotic cells, which are responsible for a number of cellular processes, such as intracellular transport, cell division, and positioning of membrane vesicles and organelles. Recently, Wu and co‐workers reported a new strategy to synthesize photo‐crosslinked AIE dots using oxetane‐substituted red‐emissive A12 and carboxyl‐ and oxetane‐enriched polystyrene (PS‐OXE) for super‐resolution microtubule imaging in cells . Followed by nanoprecipitation of A12 and PS‐OXE, UV light irradiation triggered crosslinking among the oxetane groups in A12 molecules and the encapsulating polymer through cationic ring opening polymerization.…”

Nanoparticle Probes for Super‐Resolution Fluorescence Microscopy

“…A prominent example of this kind of dye is the GFP chromophore . Synthetic dyes featuring aggregation‐induced emission (AIE) have been used to synthesize densely dye‐loaded fluorescent nanoprobes, which were shown to be highly resistant to photobleaching even under long‐term, intense STED illumination ,. Upon surface functionalization with streptavidin, these AIE NPs served as excellent probes for STED imaging of cell‐surface markers and specific subcellular structures via antigen‐antibody specific recognition in fixed MCF‐7 cells …”

“…Sun and co‐workers,, synthesized Pdots by co‐precipitation of a poly(styrene‐ co ‐maleic anhydride) polymer (PSMA) and a fluorescent polymer (poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐(1‐cyanovinylene‐1,4‐phenylene)] (CN‐PPV) or poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐(1,4‐benzo‐{2,1′,3}‐thiadazole)] (PFBT)) and used them for SOFI imaging of subcellular structures. The blinking behavior of these Pdots could easily be fine‐tuned by varying the mass ratio of the two polymers.…”

A new approach to developing diagnostics and therapeutics: Aggregation‐induced emission‐based fluorescence turn‐on

“…In addition, loose packing, formation of special excimers, and other mechanisms were also proposed to explain AIE. According to the understanding of these mechanisms, myriads of AIE‐active probes have been designed and synthesized to emit over a wide wavelength range and exhibit different fluorescent colors ranging from blue to green, and even red or near‐infrared …”