Supramolecular J- and H-Aggregation of Naphthalimide-Conjugated Dipeptide in Mixed-Solvent Systems and its Application in Cell Imaging

Abstract

In this work, a core-substituted NMI-conjugated dipeptide (4MNLV) was extensively studied in mixed solvent systems to explore the polarity effect on the self-assembly pattern and their photophysical property. 4MNLV adopted J- or H- type aggregation pattern depending upon the polarity index of the solvent system chosen. The self-assembly process was achieved through the anti-solvent effect. UV-vis study suggested that if the stock solution of 4MNLV was diluted with a relatively more polar solvent (compared to the stock solvent), then the system acquired J- type of aggregation pattern by showing a red-shift in their absorption maxima (λ_max). Conversely, when the stock was diluted by a relatively less polar solvent, H-type of aggregation was observed, where blue shift of λ_max was noticed. The emission spectra and the lifetime of the self-assembled materials were also influenced by the chosen solvent system. The chirotopic behaviour of these self-assembled materials was studied through CD spectroscopy. Morphological study indicated the formation of helical nanofibrillar structures. The bright green fluorescence of these highly biocompatible naphthalimide-peptide conjugate was used for cell imaging application, indicating its futuristic scope.