Water-Soluble Fluorescent Polyhydroxyurethane as Biocompatible Platform for Tumor Cell Imaging

Since the advent of clustering triggered emission (CTE), its potential for bioimaging has remained relatively unexplored, especially in the context of polyhydroxyurethanes (PHUs), despite their simple, non-isocyanate synthetic methodology and inherent biocompatibility. Building on these insights, we report facile, one-pot synthesis of a range of polyhydroxyurethanes (PHUs) using a careful selection of diamines to provide the necessary solubility in aqueous media for cell imaging applications. The synthesized PHUs exhibit an increase in CTE emission upon thermal annealing, with an almost sixfold increase in emission intensity on increasing the annealing time from 0 to 48 h at 90 °C. Furthermore, the concentration-dependent fluorescence studies in aqueous media show an approximately 8-fold increase in emission intensity as the polymer concentration increases from 1 to 20 mg/mL. Moreover, the excellent cytocompatibility of these PHUs against human embryonic kidney (HEK-293) and human breast adenocarcinoma (MDA-MB-231) cell lines, coupled with CTE and water solubility, enabled the imaging of living cells and deep penetration into 3D tumor spheroids. Overall, in this study, we emphasized a simple, eco-friendly, and cost-effective approach to develop biocompatible fluorescent PHUs for cellular and 3D tumor imaging.