Characteristics of the pH-regulated aggregation-induced enhanced emission (AIEE) and nanostructure orchestrate via self-assembly of naphthalenediimide–tartaric acid bola-amphiphile: role in cellular uptake

Abstract

In this study, tartaric acid (TA)-appended naphthalene diimide (NDI)-based bolaamphiphile (NDI–TA) was designed and synthesized to investigate the effect of the head group on the nanostructures fabricated by their self-assembly. Scanning electron microscopy (SEM) revealed the effect of the pH of the bolaamphiphile solution on the formation and morphology of the produced supramolecular nanostructures. It is known that the protonation/deprotonation of the TA head group in NDI–TA bolaamphiphile plays a significant role in compound nanostructures. Here, the circular dichroism (CD) study has revealed the presence of chirality at the supramolecular level of this nanostructure orchestrate. These findings show that the chirality of NDI–TA is significantly impacted in the pH range of 2 to 9. Importantly, the NDI–TA bolaamphiphile showed remarkable selectivity and biocompatibility in binding to markers in MDA-MB 231 cancer cells compared to NDI alone, even with its improved solubility. The cell morphology and uptake studies using confocal fluorescence microscopy exhibited blue to green fluorescence, a parameter that can be further explored for the efficient monitoring of intercellular pH levels and related cellular changes. Thus, our studies have demonstrated the potential of NDI–TA bolaamphiphile as a delivery agent for therapeutic intervention, and as an indicator of intercellular pH changes by binding to cell markers.