The structure, stability, and complex behavior of recombinant human gelatins

Gelatin prepared from animal sources is widely used as a stabilizer in vaccine formulations. The disadvantages associated with their use such as heterogeneity and allerginicity, have led to the development of recombinant human gelatins (rhGs) as a substitute. This study focuses on characterizing the structure and monitoring the physical stability of four molecular weights (∼8.5, 25, 50, and 100 kDa) of rhGs as a function of temperature and pH. The information supplied should be useful in predicting the behavior of rhGs under formulation conditions. A number of spectroscopic techniques were employed in this study. Experimental results indicated that the solution properties of all four rhGs were unpredictable with micro‐aggregation observed at various pH values. The 8.5 kDa rhG was found to be in a micro‐aggregated state at pH 5 while the 25 kDa rhG was found to be more aggregated at pHs 5, 7, and 8. The properties of these aggregates have been analyzed as a function of temperature. The rhGs were also found to complex with the polyanion heparin through electrostatic and nonelectrostatic interactions. The stability of these complexes has been studied as a function of temperature and pH. © 2007 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 3363-3378, 2007