Maltodextrins as lyoprotectants in the lyophilization of a model protein, LDH

Purpose. Maltodextrins, partially hydrolysed starches, were evaluated as potential lyoprotectants and the effect of combinations of maltodextrins and PEG 8000 on the protection of lactate dehydrogenase (LDH) was examined. Methods. LDH activity assays were performed immediately before freezing and after reconstitution. The activity recovery was used as the parameter to evaluate the lyoprotectants. Differential Scanning Calorimetry (DSC) was used to measure the glass transition temperature (Tg') of the solutions. DSC and X ray diffraction were used to characterise the freeze-dried products. Results. Maltodextrins were found to protect LDH againt inactivation during freeze-drying. The lyoprotection obtained by these maltodextrins is dependent on their D.E. value and the concentration used. The maltodextrin formulations performed as good or better than those containing sucrose and maltose, depending on the concentration used. Freeze dried cakes of maltodextrin formulations were amorphous. In the case of low D.E. maltodextrins, lyoprotection was improved by the addition of PEG 8000 as a cryoprotectant. Conclusions. Maltodextrins could be considered as potential lyoprotectants in lyophilization of proteins.