Potential of albumin nanoparticles as carriers for interferon gamma.

Although interferon gamma (IFN-gamma has been extensively studied as a potent activator for macrophages and as a promising adjuvant in vaccines, its rapid biodegradation and clearance have severely limited its clinical efficacy. Our major objective in this work was to develop formulation conditions to get high association of the cytokine to albumin nanoparticles, without leading any conformational changes and subsequent loss of activity. To achieve this objective, two different formulations were prepared by either 1) incubation between the cytokine and the newly prepared nanoparticles (IFN-NPA) or 2) between the protein and IFN-gamma prior coacervation (IFN-NPB). Steady-state fluorescence emission spectra revealed that the environment of the tryptophan (Trp) residue was not affected by conditions of mechanical stress required for preparing nanoparticles. A bioassay for antiproliferative activity with Hela cells indicated that the cytokine, after their desorption from the surface of nanoparticles (IFN-NPA), fully retained its activity. It also indicated that the cytokine was principally associated with nanoparticles via electrostatic interactions and confirmed by desorption experiments carried out in media with different pH and ionic strength, with burst effect ranked in the order pH 5 > pH 7.4 > pH 8.5. Also, the adsorption of IFN-gamma onto these carriers was able to improve the priming effects of IFN-gamma on the nitric oxide production (NO) by RAW macrophages. On the contrary, when we incubated the cytokine with the albumin solution prior to the desolvation process for preparing nanoparticles (IFN-NPB), we obtained better encapsulation efficiencies (around 100%), but the cytokine was inactive: it was not detected by ELISA or bioassay in Hela cells and unable to stimulate NO production by macrophages.