Peptide conjugates of a nonsteroidal anti-inflammatory drug as supramolecular gelators: Synthesis, characterization, and biological studies

Abstract

Indomethacin (IND), which is a well-known nonsteroidal anti-inflammatory drug (NSAID), was conjugated with various naturally occurring amino acids. Most of these bioconjugates were capable of gelling pure water, a solution of NaCl (0.9 wt %), and phosphate-buffered saline (pH 7.4), as well as a few organic solvents. The gels were characterized by table-top and dynamic rheology, and electron microscopy. Variable-temperature ¹H NMR spectroscopy studies on a selected gel were performed to gain insights into the self-assembly process during gel formation. Both 1D and 2D hydrogen-bonded networks were observed in the single-crystal structures of two of the gelators. Plausible biological applications of the hydrogelators were evaluated with the ultimate aim of drug delivery in a self-delivery fashion. All hydrogelators were stable in phosphate-buffered saline at pH 7.4 at 37 °C, and biocompatible in mouse macrophage RAW 264.7 cell line (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay). Two of the most biocompatible hydrogelators displayed an anti-inflammatory response comparable to that of the parent drug IND in prostaglandin E₂ assay. Release of the bioconjugates into the bulk solvent interfaced with the corresponding hydrogels indicated their plausible future application in drug delivery.