Release of PEGylated granulocyte-macrophage colony-stimulating factor fromchitosan/glycerol films

We have prepared a new formulation for mucosal delivery of GM-CSF or PEGyla ted GM-CSF based on a chitosan carrier plus added glycerol to control the r ate of release of the protein. Thin dry films comprised of various weight r atios of chitosan to glycerol and containing either granulocyte-macrophage colony-stimulating factor (GM-CSF) or PEGylated GM-CSF, PEG-(GM-CSF), were prepared. The amount of GM-CSF or PEG-(GM-CSF) released from the chitosan/g lycerol films was determined using size exclusion high performance liquid c hromatography (HPLC-SEC). The amount of PEG-(GM-CSF) released from the film s decreased with an increase in the amount of glycerol present in the film. In parallel with this, films with higher glycerol content exhibited a lowe r degree of equilibrium swelling when immersed in release media, pH measure ments of the release media and analysis of the dried films by Fourier-trans form infrared spectroscopy (FTIR) suggested that the amount of residual ace tic acid in the dry films decreased as the glycerol content increased. This indicates that glycerol may act by displacing and releasing bound acetic a cid from the chitosan molecules, resulting in chitosan-glycerol hydrogen bo nd formation as the film dries. Further, it was found that the release rate and the amount of PEG-(GM-CSF) released decreased with increasing molecula r weight of the conjugated PEG. This effect was not observed with films con taining physical mixtures of PEG and GM-CSF. The decrease in the fraction o f PEG-(GM-CSF) released with increasing PEG molecular weight is believed to be due to the increased steric hindrance of the PEGylated protein molecule during its diffusion out of the swollen chitosan/glycerol film, (C) 2001 E lsevier Science B.V. All rights reserved.