Synthesis of Fluorescent, Dumbbell-Shaped Polyurethane Homo- and Heterodendrimers and Their Photophysical Properties.

Fluorescent dendrimers have wide applications in biomedical and materials science. Here, we report the synthesis of fluorescent polyurethane homodendrimers and Janus dendrimers, which often pose challenges due to the inherent reactivity of isocyanates. Polyurethane dendrons (G1-G3) were synthesized via a convergent method using a one-pot multicomponent Curtius reaction as a crucial step to establish urethane linkages. The alkyne periphery of the G1-G3 dendrons was modified by a copper catalyzed azide-alkyne click reaction (CuAAC) to form fluorescent dendrons. In the reaction of the surfaces functionalized two different dendrons with a difunctional core, a mixture of three dendrimers consisting of two homodendrimers and a Janus dendrimer were obtained. The Janus dendrimer accounted for a higher proportion in the products' distribution, being as high as 93% for G3. The photophysical properties of Janus dendrimers showed the fluorescence resonance energy transfer (FRET) from one to the other fluorophore of the dendrimer. The FRET observation accompanied by a large Stokes shift make these dendrimers potential candidates for the detection and tracking of interactions between the biomolecules, as well as potential candidates for fluorescence imaging.

Nitric oxide, DPPH and hydrogen peroxide radical scavenging activity of TEMPO terminated polyurethane dendrimers: Data supporting antioxidant activity of radical dendrimers.

This article describes free radical scavenging activity of TEMPO (2, 2, 6, 6-tetramethylpiperidin-1-yloxyl) radical functionalized dendrimers of generation G0 - G4 against nitric oxide (NO), 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) radicals. The total antioxidant activity of the dendrimers was also reported and compared with pure 4-hydoxy TEMPO (constituent of dendrimers) and ascorbic acid (vitamin C) standard. The activity of TEMPO functionalized G4 dendrimer against scavenging of nitric oxide and hydrogen peroxide radicals was found comparable to vitamin C. The data presented in this article supports the good antioxidant activity of the dendrimers newly reported in our previous publication (Radical dendrimers: Synthesis, anti-tumor activity and enhanced cytoprotective performance of TEMPO free radical functionalized polyurethane dendrimers).