Investigating the Stability of RADA16 Peptide Nanofibers Using CD Spectra

Abstract

RADA 16-I is a synthetic amphiphilic peptide which self-assembles into nanofibers and scaffolds in favor of cell growth, hemostasis and tissue engineering. However, it is still unclear in which conditions the peptide maintains its stability and structural consistency in aqueous solutions during storage time. This study investigates dynamic behavior of RADA 16-I using circular dichroism, so as to monitor changes in conformation of the peptides dispersed in water (pH 5) as well as 0.003 M (pH 4) and 0.02 M (pH 3) acetic acid solutions for various incubation times (0.5, 60 and 120 days), concentrations (0.1, 0.3 and 0.5%) and temperatures (4 and 25 °C). The results showed that the peptides exhibit a predominantly helical structure immediately after making their solutions. However, it was seen that, when exposed to solutions with pH 3 and 4, the peptides started to lose the helical structure, with increased amounts of aggregation at these two acidic pH values; this was attributed to increased hydrophobicity. The stable RADA 16-I peptides were identified at pH 5, 0.1% solution and 4 °C, with their secondary structure remained mostly unchanged during the 120-day test period. Furthermore, statistical analysis showed that, the concentration had little effect while pH and temperature had significant effects on the peptide stability, while acidic pH enhanced aggregation. These results may serve as a scientific basis for the processing and application of peptide.