Oxidative and nitrosative stress induced by ROS/RNS play crucial roles in a wide range of physiological processes and are also implicated in various diseases, including cancer and neurodegenerative disorders. Sensitive and selective methods for the detection of ROS/RNS based on fluorescent and luminescent probes are of great use in monitoring the in vivo production of these species and elucidating their biological functions. This critical review highlights recent advances that have been made in the development of fluorescent and luminescent probes employed to monitor various ROS/RNS (132 references).

The currently available anticancer agents frequently cause unwanted normal cell death mainly owing to their lack of selectivity for cancer cells. In addition, molecular imaging agents for tumors exhibit low target-to-background ratios. As a consequence, elegant methods that more specifically target cancer cells need to be developed for the improvement of chemotherapeutic efficacy and diagnosis. In a recent effort aimed at improving the tumor selectivity of therapeutic and imaging agents, we designed, synthesized and explored the effectiveness of a dual-targeting delivery system that targets cancer cells more selectively. The new delivery system is composed of a synthetic ligand (octreotide) of somatostatin receptors, a dipeptide substrate for cathepsin B, and a fluorophore or an anticancer agent. The fluorophore-conjugated delivery system was found to be applicable for specific fluorescence imaging of cancer cells that express both somatostatin receptors and cathepsin B. In addition, the anticancer agentcontaining delivery system leads to the death of cancer cells specifically. In contrast to cancer cells, normal cells that do not produce both somatostatin receptors and cathepsin B at high levels are unaffected by the delivery system. The new dual-targeting approach has the capability of overcoming obstacles associated with current chemotherapeutic and imaging methods.

In this work, a folate receptor (FR)-mediated dual-targeting drug delivery system was synthesized to improve the tumor-killing efficiency and inhibit the side effects of anticancer drugs. We designed and synthesized an FR-mediated fluorescence probe (FA-Rho) and FR-mediated cathepsin B-sensitive drug delivery system (FA-GFLG-SN38). FA-GFLG-SN38 is composed of the FR ligand (folic acid, FA), the tetrapeptide substrate for cathepsin B (GFLG), and an anticancer drug (SN38). The rhodamine B (Rho)-labeled probe FA-Rho is suitable for specific fluorescence imaging of SK-Hep-1 cells overexpressing FR and inactive in FR-negative A549 and 16-HBE cells. FA-GFLG-SN38 exhibited strong cytotoxicity against FR-overexpressing SK-Hep-1, HeLa, and Siha cells, with IC50 values of 2–3 μM, but had no effect on FR-negative A549 and 16-HBE cells. The experimental results show that the FA-CFLG-SN38 drug delivery system proposed by us can effectively inhibit tumor proliferation in vitro, and it can be adopted for the diagnostics of tumor tissues and provide a basis for effective tumor therapy.

To investigate the density-dependent binding of glycans by lectins using carbohydrate microarrays, a number of C-terminal hydrazide-conjugated neoglycopeptides with various valences and different spatial arrangements of the sugar ligands were prepared on a solid support. The synthetic strategy includes (1) assembly of alkyne-linked peptides possessing C-terminal hydrazide on a solid support, (2) coupling of azide-linked, unprotected sugars to the alkyne-linked peptides on the solid support utilizing click chemistry, and (3) release of the neoglycopeptides from the solid support. By using this synthetic methodology, sixty five neoglycopeptides with a valency ranging from 1 to 4 and different spatial arrangements of the carbohydrate ligands were generated. Carbohydrate microarrays were constructed by immobilizing the prepared neoglycopeptides on epoxide-derivatized glass slides and were used to analyze the density-dependent binding of glycans by lectins. The results of binding property determinations show that lectin binding is highly dependent on the surface glycan density.