Hydrogelation of a Naphthalene Diimide Appended Peptide Amphiphile and Its Application in Cell Imaging and Intracellular pH Sensing

Abstract

This study reports the self-assembly and application of a naphthalene diimide (NDI)-appended peptide amphiphile (PA). H-bonding among the peptide moiety in conjunction with π-stacking between NDI and hydrophobic interactions within the alkyl chain are the major driving forces behind the stepwise aggregation of the PA to form hydrogels. The PA produced efficient self-assemblies in water, forming a nanofibrous network that further formed a self-supportive hydrogel. The molecule followed a three-step self-assembly mechanism. At a lower concentration (50 μM), it forms extremely small aggregates with a very low population of the molecules. With an increase in concentration, spherical aggregates are formed above 450 μM concentration. Importantly, this water-soluble conjugate was found to be nontoxic, cell permeable, and usable for cell imaging. Moreover, the aggregation process and consequently the emission behavior are highly responsive to the pH of the medium. Thus, the pH responsive aggregation and emission behavior has an extended biological application for assessing intracellular pH. The biocompatibility and intracellular pH determining capability suggest it is a promising candidate for use as a supramolecular material in biomedical applications.

Unusual confinement properties of a water insoluble small peptide hydrogel

“…Similar studies were performed with two of our previously reported hydrogels. 25,26 However, in both cases, the hydrogels get dissolved in bulk H 2 O/D 2 O and all the H 2 O molecules were found in the NMR samples. These results demonstrate that the self-assembly creates a system where both the gel-network and the water of gelation are inaccessible to the surrounding environment.…”

Rational Design of Peptide-based Smart Hydrogels for Therapeutic Applications

“…Peptide-Based Smart Therapeutic Hydrogels NDI in case of 46) to provide additional stability to the aggregates (Singha et al, 2017). Recently, we have demonstrated the combination of charge transfer (CT) and cation-π interactions between two molecules that lead to the formation of a self-healing hydrogel.…”

Self‐Assembled Peptide‐Based Nanoprobes for Disease Theranostics and Disease‐Related Molecular Imaging

“…The MSCs labeling results demonstrated that the peptide‐modified SPIONs could improve the targeting efficiency and the rate of positive labeling by up to 95%. Das and co‐workers used a fluorescent naphthalene diimide as a linker to conjugate the hydrophobic C 6 H 13 ‐alkyl chain and the hydrophilic GKRGDS peptide. The resultant peptide amphiphile could self‐assemble into hydrogels through a three‐step self‐assembly mechanism.…”