Stability and angiotensin converting enzyme inhibitory activity of peptide RVPSL-loaded graphene oxide

Abstract

Previous work has demonstrated that the angiotensin converting enzyme (ACE) inhibitory peptide RVPSL is very unstable and loses its ACE inhibitory activity in the gastrointestinal tract. Thus, graphene oxide (GO) was used to improve the stability of RVPSL in the present work. The structure and morphology of RVPSL-GO were characterised using Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. Moreover, the cytotoxicity of RVPSL-GO was examined using HepG2 cells. RVPSL was successfully covalently bonded to GO and the RVPSL-loading capacities of RVPSL-GO were calculated to be 1.05 mg RVPSL/mg GO, and the loading efficiency value was 95.02%. The results showed that GO enhanced RVPSL ACE activity (at 0.026 mg/mL) from 26.47 to 39.70%. This may have caused a higher local concentration of RVPSL in the solution after GO was modified. Moreover, the stability of RVPSL was improved with protection from GO. The ACE inhibition rate of RVPSL-GO was 49.08%, while RVPSL was completely degraded after 2 h in simulated gastrointestinal digestion. In addition, RVPSL-GO displayed high viability for HepG2 cells with no significant cytotoxicity.