Boosting the properties of a fluorescent dye by encapsulation into halloysite nanotubes

The synthesis of a new biocompatible bichromophoric system (CURBO) was developed, by connecting the skeleton of the naturally occurring curcumin to a BODIPY derivative. The system exhibited an intense fluorescence band with maximum at about 510 nm in organic solvent, while its emission spectra in aqueous solution were more complicated and slightly red-shifted, due to the effect of aggregation for the poor solubility of the dyad. To overcome these problems, the bichomophoric system has been loaded into the halloysite nanotubes (HNT). The HNT/CURBO nanocomposite, suspended in aqueous solution, showed an intensity of emission in the red region of the spectrum higher than the one exhibited by the pristine CURBO. The biocompatibility and photophysical behavior of HNT/CURBO nanocomposite were studied using ASC52Telo, h-TERT immortalized adipose-derived mesenchymal stem cells. To investigate the localization of the CURBO alone and in HNT/CURBO, fluorescence epimicroscopy was performed. The HNT/CURBO nanocomposite showed a high propensity to cross cell membranes, resulting in a massive cell uptake around the cell nucleus. Moreover, it lighted up ASC52Telo cells both with intense green and red fluorescence while excited in the blue portion of the electromagnetic spectrum, a phenomenon that could not be observed for the free CURBO. Dual-channel emissions dyes and, in particular, materials, such as the HNT/CURBO nanocomposite, emitting in the red portion of the spectrum have become, in recent decades, particularly fascinating since they can minimize the autofluorescence detection of the cell medium and allow interesting microscopy applications.