A Review of Off-On Fluorescent Nanoprobes: Mechanisms, Properties, and Applications

A Competitive "On-Off-Enhanced On" AIE Fluorescence Switch for Detecting Biothiols Based on Hg2+ Ions and Gold Nanoclusters

In this study, a novel "on-off-enhanced on" approach to highly sensitive rapid sensing of biothiols was developed, based on competitive modulation of gold nanoclusters (AuNCs) and Hg2+ ions. In our approach, the AuNCs were encapsulated into a zeolite imidazole framework (ZIF) for predesigned competitive aggregation-induced luminescence (AIE) emission. To readily operate this approach, the Hg2+ ions were selected as mediators to quench the fluorescence of AuNCs. Then, due to the stronger affinities between the interactions of Hg2+ ions with -SH groups in comparison to the AuNCs with -SH groups, the quenched probe of AuNCs@ZIF-8/Hg2+ displayed enhanced fluorescence after the Hg2+ ions were competitively interacted with -SH groups. Based on enhanced fluorescence, the probe for AuNCs@ZIF-8/Hg2+ had a sensitive and specific response to trace amounts of biothiols. The developed fluorescence strategy had limit of quantification (LOQ) values of 1.0 μM and 1.5 μM for Cys and GSH molecules in serum, respectively. This competitive AIE strategy provided a new direction for developing biological probes and a promising method for quantifying trace amounts of biothiols in serum. It could promote progress in disease diagnosis.

Experimental Study on Antitumor Activity of Gold Nanoparticles-Assisted Delivery of PD-L1 SiRNA in Non-Small Cell Lung Cancer

Objective: By delivering PD-L1 siRNA to A549 cells using nano-gold we tried to enhance the lymphocytes’ ability to inhibit the growth of non-small-cell lung cancer. Methods: In a one-step reaction, gold nanoparticles and PD-L1 siRNA were combined to form gold nanoparticles and PD-L1 siRNA complexes. After incubation with A549 cells, PD-1 was detected by quantitative polymerase chain reaction (qPCR) as well as immunohistochemical staining. Mouse xenografts were used to test the anti-tumor activity. It was found that using a gold nanoparticle-siRNA complex, we were able to successfully reduce the expression of PD-L1 in A549 cells. The nano-gold-siRNA complex outperformed free siRNA after co-incubation with tumor cells. In vivo experiments show that nano-gold-siRNA is more effective at targeting tumor tissue and increasing T cells’ ability to inhibit the A549 tumor than free siRNA. For this study, we found that the delivery of siRNA to tumors using a nano-gold nanoparticle enhances the ability of the siRNA to aggregate in tumors, which in turn enhances the ability of T lymphocytes to combat non-small cell lung cancer by enhancing their anti-tumor activity. This nano-gold-PD-L1-siRNA complex may be a promising treatment for non-small cell lung cancer, according to preliminary results.