High stability of the immunomodulatory GK-1 synthetic peptide measured by a reversed phase high-performance liquid chromatography method.

The 18-mer anionic peptide GK-1 has been successfully employed to improve the immunogenicity and protective response induced by the influenza vaccine and exhibited some degree of protection against experimental murine melanoma. In this study, a sensitive and quantitative reversed-phase HPLC method was developed to study GK-1 stability under different pH, temperature and storage time. The analysis was carried out on a Sunfire C18 column with mobile phase of acetonitrile-water containing 0.02% TFA. The detection was performed on an UV/Vis Detector at 220nm. The method was validated with respect to linearity, limits of detection and quantification, precision and selectivity. The linear calibration curves were obtained in the concentration range of 0.015-0.24mg/mL (r(2)=0.99) with lower limits of detection (LOD) and quantification (LOQ) of 0.001 and 0.018mg/mL, respectively. The intra- and inter-day precision (relative standard deviation, R.S.D.) values were below 3% at all quality control levels. Forced degradation studies were conducted by introducing a sample of GK-1 peptide standard solution to different conditions of pH (from 2 to 8), temperature (4, 25 and 40°C) and storage time (10days to 6 months). The peptide GK-1 showed to be stable under different ranges of pH and temperature; however it was susceptible to prolonged storage at room temperature. Results shown in this study sustain the high stability of the GK-1 peptide using a reliable new selective and precise method suitable for its analysis.