The ability to predict an antibody’s propensity for aggregation is particularly important during product development to ensure the quality and safety of therapeutic antibodies. We demonstrate the role of container surfaces on the aggregation process of three mAbs under elevated temperature and long-term storage conditions in the absence of mechanical stress. A systematic study of aggregation is performed for different proteins, vial material, storage temperature, and presence of surfactant. We use size exclusion chromatography and micro-flow imaging to determine the bulk concentration of aggregates, which we combine with optical and atomic force microscopy of vial surfaces to determine the effect of solid-liquid interfaces on the bulk aggregate concentration under different conditions. We show that protein particles under elevated temperature conditions adhere to the vial surfaces, causing a substantial underestimation of aggregation propensity as determined by common methods used in development of biologics. Under actual long-term storage conditions at 5°C, aggregate particles do not adhere to the surface, causing an increase in bulk concentration of particles, which cannot be predicted from elevated temperature screening tests by common methods alone. We also identify specific protein – surface interactions which promote oligomer formation in the nanometre range. Special care should be taken when interpreting size exclusion and particle count data from stability studies if different temperatures and vial types are involved. We propose a novel combination of methods to characterise vial surfaces and bulk solution for a full understanding of protein aggregation processes in a sample.
COBISS.SI-ID: 3403620
Protein aggregation is a field of increasing importance in the biopharmaceutical industry. Aggregated particles decrease the effectiveness of the drug and are associated with other risks, such as increased immunogenicity. This article explores the possibility of using the Smoluchowski coagulation equation and similar models in the prediction of aggregate-particle formation. Three different monoclonal antibodies, exhibiting different aggregation pathways, are analysed. Experimental data are complemented with aggregation dynamics calculated by a coagulation model. Different processes are implemented in the coagulation equation approach, needed to cover the actual phenomena observed in the aggregation of biopharmaceuticals, such as the initial conformational change of the native monomer and reversibility of smaller oligomers. When describing the formation of larger particles, the effect of different aggregation kernel parameters on the corresponding particle size distribution is studied. A significant impact of the aggregate fractal nature on overall particle size distribution is also analysed. More generally, this work is aimed to establish a mesoscopic phenomenological approach for characterisation of protein aggregation phenomena in the context of biopharmaceuticals, capable of covering various aggregate size scales from nanometres to micrometres and reach large time-scales, up to years, as needed for drug development.
COBISS.SI-ID: 3212644
Controlling the viscosity of concentrated protein solutions -- usually reducing -- is an open challenge, with major recent relevance in protein formulations for biopharmaceutical, medical, food, and other applications. It is of major importance to be able to establish control over the combination of viscosity-affecting additives and adequate protein stability, usually at high protein concentrations. Here, we demonstrate the control and manipulation of the viscosity profile of a selected protein solution (monoclonal antibody of immunoglobulin gamma type – IgG) of direct biopharmaceutical relevance, by identifying elementary viscosity contributions via selected additives that target different protein-protein interactions. Specifically, a combined study of viscosity control and protein aggregation is performed with viscosity characterized by microfluidic measurements and protein aggregation by size-exclusion chromatography, where aggregation data is further supplemented with conformational stability measurements via thermal and chemical protein denaturation. More generally, we show a control over the interplay of viscosity, potency and stability in a distinct protein system, as a general contribution to understanding the viscosity in different colloidal, biological, and soft materials.
COBISS.SI-ID: 23640579
Generation of read-on-demand images and identification codes in a liquid crystal (LC) device is demonstrated. Experimentally, these micrometer-sized polymer features are encoded directly into LC devices using direct laser writing, which locks-in the local molecular orientation at the moment of fabrication. By reading the devices with the same voltage amplitude that is used to write the polymer structures, features can be made to disappear as the director profile becomes homogeneous with the surrounding regions, effectively cloaking the structure for both polarized and unpolarized light The potential use of this work is in authenticity and identification applications. Experiments were performed at the University of Oxford, whereas theory and numerical modelling at the Faculty of Mathematics and Physics at the University of Ljubljana and Department of Condensed Matter Physics at the Jozef Stefan Institute. Work was also presented by Editors of Nature Photonics (Nat. Photon. 12, 504 (2018)).
COBISS.SI-ID: 3223396
We show that topological defects in an ion-doped nematic liquid crystal can be used to manipulate the surface charge distribution on chemically homogeneous, charge-regulating external surfaces, using a minimal theoretical model. In particular, the location and type of the defect encodes the precise distribution of surface charges and the effect is enhanced when the liquid crystal is flexoelectric. We demonstrate the principle for patterned surfaces and charged colloidal spheres. More generally, our results indicate an interesting approach to control surface charges on external surfaces without changing the surface chemistry.
COBISS.SI-ID: 23706371