Spatially Selective Monitoring of Subcellular Enzyme Dynamics in Response to Mitochondria-Targeted Photodynamic Therapy.

Tracking spatial and temporal dynamics of bioactive molecules such as enzymes responding to therapeutic treatment is highly important for understanding of the related functions. However, in situ molecular imaging at subcellular level during photodynamic therapy (PDT) has been hampered by the limitations of existing methods. Herein, we present a multifunctional nanoplatform (termed as UR-HAPT) that is able to simultaneously monitor subcellular dynamics of human apurinic/apyrimidinic endonuclease 1 (APE1) during the near-infrared (NIR) light-mediated PDT. UR-HAPT was constructed by the combination of an upconversion nanoparticle-based PDT design and a mitochondria-targeting strategy with an APE1-responsive DNA reporter. Benefiting from the gain-of-function approach, activatable mitochondrial accumulation of APE1 in response to the oxidative stress was observed during the NIR light-triggered, mitochondria-targeted PDT process. We envision that this nanoplatform can be applicable to screen and evaluate potential enzyme inhibitors to improve the PDT efficacy.

Exploring the Condensation Reaction between Aromatic Nitriles and Amino Thiols To Optimize In†Situ Nanoparticle Formation for the Imaging of Proteases and Glycosidases in Cells.

The condensation reaction between 6-hydroxy-2-cyanobenzothiazole (CBT) and cysteine has been shown for various applications such as site-specific protein labelling and in vivo cancer imaging. This report further expands the substrate scope of this reaction by varying the substituents on aromatic nitriles and amino thiols and testing their reactivity and ability to form nanoparticles for cell imaging. The structure-activity relationship study leads to the identification of the minimum structural requirement for the macrocyclization and assembly process in forming nanoparticles. One of the scaffolds made of 2-pyrimidinecarbonitrile and cysteine joined by a benzyl linker was applied to design fluorescent probes for imaging caspase-3/7 and ß-galactosidase activity in live cells. These results demonstrate the generality of this system for imaging hydrolytic enzymes.

Recent Developments in Peptidyl Diaryl Phoshonates as Inhibitors and Activity-Based Probes for Serine Proteases.

This review presents current achievements in peptidyl diaryl phosphonates as covalent, specific mechanism-based inhibitors of serine proteases. Along three decades diaryl phosphonates have emerged as invaluable tools in fundamental and applicative studies involving these hydrolases. Such an impact has been promoted by advantageous features that characterize the phosphonate compounds and their use. First, the synthesis is versatile and allows comprehensive structural modification and diversification. Accordingly, reactivity and specificity of these bioactive molecules can be easily controlled by appropriate adjustments of the side chains and the leaving groups. Secondly, the phosphonates target exclusively serine proteases and leave other oxygen and sulfur nucleophiles intact. Synthetic accessibility, lack of toxicity, and promising pharmacokinetic properties make them good drug candidates. In consequence, the utility of peptidyl diaryl phosphonates continuously increases and involves novel enzymatic targets and innovative aspects of application. For example, conjugation of the structures of specific inhibitors with reporter groups has become a convenient approach to construct activity-based molecular probes capable of monitoring location and distribution of serine proteases.