Tripeptide consisting of benzyl protected di-cysteine and phenylalanine forms spherical assembly and induces cytotoxicity in cancer cells via apoptosis

Abstract

The study of peptide derived self-organized nanoarchitectures is an emerging scientific research area due to its potential application in advanced material science, biointerface engineering, therapeutics etc. In the present study, we report the synthesis and detailed biophysical properties of terminally protected tripeptide ‘N-Boc-L-Phe-S-benzyl-L-Cys-S-benzyl-L-Cys methyl ester’. The solid state FTIR spectrum reveals an intermolecular hydrogen bonded β-sheet like backbone in the solid state. Accordingly, secondary conformation of this tripeptide in the liquid state has been investigated by CD spectroscopy, which demonstrates that the tripeptide preferably exists as an unordered conformation in the liquid phase. Morphology of the self-assembled structure adapted by this tripeptide has been determined by atomic force microscopy (AFM), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). AFM results revealed that the tripeptide self-assembly behaviour is concentration dependent but independent of the solvent system in which the self-assembled structure was formed. Concentrated methanol solution of the tripeptide produces oligomers 800–1050 nm in size, whereas diluted solutions of tripeptide in ethyl acetate solvent constructs oligomers 350–550 nm in size (diameter). Moreover, this tripeptide retains its self-assembled structure in biological environments i.e. DMEM and FBS also. Furthermore, the tripeptide shows potential cytotoxicity towards cancer cell lines. IC₅₀ values were found to be 6.2 to 7.5 μM against breast (MCF-7, MDA-MB-231) and liver cancer (HepG2) cell lines, estimated by in vitro cell viability assay. Western blot analysis establishes that this tripeptide kills the cancer cells through apoptosis.