Stability and biological activity evaluations of PEGylated human basic fibroblast growth factor

BACKGROUND: Human basic fibroblast growth factor (hBFGF) is a heparin-binding growth factor and stimulates the proliferation of a wide variety of cells and tissues causing survival properties and its stability and biological activity improvements have received much attention. MATERIALS AND METHODS: In the present work, hBFGF produced by engineered Escherichia coli and purified by cation exchange and heparin affinity chromatography, was PEGylated under appropriate condition employing 10 kD polyethylene glycol. The PEGylated form was separated by size exclusion chromatography. Structural, biological activity, and stability evaluations were performed using Fourier transform infrared (FITR) spectroscopy, 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay and effect denaturing agent, respectively. RESULTS: FITR spectroscopy revealed that both PEGylated and native forms had the same structures. MTT assay showed that PEGyalated form had a 30% reduced biological activity. Fluorescence spectrophotometry indicated that the PEGylated form denatured at higher concentrations of guanidine HCl (1.2 M) compared with native, which denatured at 0.8 M guanidine HCl. CONCLUSIONS: PEGylation of hBFGF makes it more stable against denaturing agent but reduces its bioactivity up to 30%.