AIEgens/Nucleic Acid Nanostructures for Bioanalytical Applications

A Target-Triggered Emission Enhancement Strategy Based on a Y-Shaped DNA Fluorescent Nanoprobe with Aggregation-Induced Emission Characteristic for microRNA Imaging in Living Cells

DNA self-assembled fluorescent nanoprobes have been developed for bio-imaging owing to their high resistance to enzyme degradation and great cellular uptake capacity. In this work, we designed a new Y-shaped DNA fluorescent nanoprobe (YFNP) with aggregation-induced emission (AIE) characteristic for microRNA imaging in living cells. With the modification of the AIE dye, the constructed YFNP had a relatively low background fluorescence. However, the YFNP could emit a strong fluorescence due to the generation of microRNA-triggered AIE effect in the presence of target microRNA. Based on the proposed target-triggered emission enhancement strategy, microRNA-21 was detected sensitively and specifically with a detection limit of 122.8 pM. The designed YFNP showed higher bio-stability and cell uptake than the single-stranded DNA fluorescent probe, which has been successfully applied for microRNA imaging in living cells. More importantly, the microRNA-triggered dendrimer structure could be formed after the recognition of target microRNA, achieving a reliable microRNA imaging with a high spatiotemporal resolution. We expect that the proposed YFNP will become a promising candidate for bio-sensing and bio-imaging.

Chemiluminescence Resonance Energy Transfer-Based Mesoporous Silica Nanosensors for the Detection of miRNA

The chemiluminescence resonance energy transfer (CRET)-based method is free of autofluorescence interference, which can achieve an extremely high signal-to-background ratio for detection. Nevertheless, this method is still hindered by the inner filter effect, quenching effect, and nonspecific absorption of reported nanoparticles. Herein, mesoporous silica nanomaterials (MSNs) acted as carriers to load both the donor (horseradish peroxidase, HRP) and the acceptor (a functional DNA duplex). This approach realized the construction of a new CRET-based nanosensor for the sensitive detection of miRNA. By controlling the energy-transfer distance with the designed DNAs, the donor emission at 430 nm could be quenched by the adsorption of the dye labeled on the acceptor DNA. The CRET system could be destroyed by releasing acceptor DNA from linker DNA via the competitive hybridization of target miRNA, resulting in emission recovery for quantification. With the cancer biomarker miR-155 as the model, the sensitive and selective detection of miR-155 was achieved, which showed high energy-transfer efficiency, good specificity, favorable biodegradability, and low toxicity. This work provides a potential pathway for biological detection and clinical diagnosis.

Manipulating Solid-State Intramolecular Motion toward Controlled Fluorescence Patterns

Molecules have limited mobility in the solid state because of the strong intermolecular interactions, and therefore, applications based on solid-state molecular motions are seldom explored. Herein, by manipulating the solid-state intramolecular motion of tetraphenylethylene (TPE) in a crystallizing polymer matrix, controlled fluorescent patterns with information storage and encoding functionality are developed. The intramolecular mobility of TPE can not only affect the fluorescence intensity but also determine the photocyclization activity, which can be tuned by surrounding polymer rigidity. The soft amorphous region in the semicrystalline polymer facilitates the intramolecular motion to achieve weak blue emission and high photocyclization activity, whereas the rigid crystalline phase restricts the intramolecular motion to give intense blue emission and low photoreactivity. Meanwhile, in the process of crystallization, the dynamic movement of the polymer chain in the crystal growth boundary layer further accelerates the intramolecular motions of TPE, allowing enhanced photoreactivity across crystalline and amorphous regions. The motion-dominated fluorescence allows TPE as a smart molecular robot to generate desired fluorescent patterns triggered by polymer crystallization. Our findings provide a correlation between microscopic molecular motions and macroscopic optical signals.