Tethered Indoxyl-Glucuronides for Enzymatically Triggered Cross-Linking

Abstract

Indoxyl-glucuronides, upon treatment with β-glucuronidase under physiological conditions, are well known to afford the corresponding indigoid dye via oxidative dimerization. Here, seven indoxyl-glucuronide target compounds have been prepared along with 22 intermediates. Of the target compounds, four contain a conjugatable handle (azido-PEG, hydroxy-PEG, or BCN) attached to the indoxyl moiety, while three are isomers that include a PEG-ethynyl group at the 5-, 6-, or 7-position. All seven target compounds have been examined in indigoid-forming reactions upon treatment with β-glucuronidase from two different sources and rat liver tritosomes. Taken together, the results suggest the utility of tethered indoxyl-glucuronides for use in bioconjugation chemistry with a chromogenic readout under physiological conditions.

Molecular design for sub-micromolar enzyme-instructed self-assembly (EISA)

“…Still, there were perceived limitations to the molecular design and/or studies of I: (1) the concentration examined of I was 68 mM, which is likely B10 000 fold higher than relevant for radiotherapy; and (2) the enzyme treatment was carried out in Tris-HCl buffer at pH 9.0, which is not physiologically relevant. Several other substrates for EISA strategies were examined, [20][21][22][23][24] yet each proved to have idiosyncratic limitations.…”