Polyphosphate as a novel aggregation suppressor of gamma globulin

The aggregation of gamma globulin poses a significant challenge in maintaining the quality of biopharmaceutical products. This study aimed to develop a novel approach to prevent gamma globulin aggregation using polyphosphates (PolyPs), linear polymers comprising 14 to 130 phosphate units. The addition of PolyPs effectively suppressed the formation of subvisible particles (SVPs) in the micrometer-sized fraction of bovine gamma globulin (BGG) during storage at 40 °C, as observed through flow imaging. Furthermore, PolyPs mitigated the decrease in soluble protein concentration under these conditions. Mass photometry and isothermal titration calorimetry revealed that PolyPs spontaneously form complexes with BGG. The negative zeta potential and positive B₂₂ and k_Diff values suggested that the BGG-PolyP complexes were stabilized by electrostatic repulsion. Importantly, far-UV circular dichroism confirmed that the secondary structure of BGG remained unaffected by complexation with PolyPs. Notably, arginine-a commonly used aggregation suppressor-failed to prevent the formation of SVPs in BGG under similar conditions. This study demonstrates the potential of biocompatible and stable PolyPs as a novel additive for inhibiting gamma globulin aggregation, offering a promising alternative to conventional approaches.