Sugar-Phosphate Composite Glasses for Lysozyme: An Effective Technique for Lysozyme Preservation

The Spray drying method was employed for the processing and storage preservation of lysozyme using sugar-phosphate glasses. While previous studies have reported the surfactants to reduce protein adsorption at the air/water interface, this study demonstrates that water-soluble inorganic phosphates effectively minimize lysozyme surface adsorption. Sugar glasses containing sucrose or mannitol, combined with water-soluble phosphates and glass formers such as PVP K30 or calcium lactate were prepared using hot plate drying. These sugar glasses were evaluated to confirm their glassy state using optical microscopy, infrared spectral analysis, X-ray diffraction (XRD), and thermal behavior studies (DSC). The lysozyme mixtures with sugar glasses were processed using both spray drying and lyophilization. They were then analyzed for pH, moisture content, % yield, and % lysozyme activity. Physical changes in lysozyme were assessed using XRD. The batch exhibiting the highest lysozyme activity was selected for stability testing in accordance with ICH guidelines. Results indicated that water-soluble phosphates, in combination with glass formers like PVP K 30 and calcium lactate, efficiently formed composite glasses during spray drying, whereas water-insoluble phosphates failed to produce a stable glassy matrix. XRD analysis of sodium phosphate monobasic and dibasic in the presence of glass formers confirmed an amorphous state during post-stability studies, with maximum lysozyme activity retained at room temperature. The processing and storage stability of lysozyme was superior in spray-dried products compared to lyophilized ones. These findings validate the potential of sugar-phosphate composite glasses as an effective technique for lysozyme preservation, offering a promising approach to enhancing protein stability in pharmaceutical formulations.