Concentrated solutions of monoclonal antibodies have attracted considerable attention due to their importance in pharmaceutical formulations, yet their tendency to aggregate and the resulting high solution viscosity has posed considerable problems. It remains a very difficult task to understand and predict the phase behavior and stability of such solutions. Here we present a systematic study of the concentration dependence of the structural and dynamic properties of monoclonal antibodies using a combination of different scattering methods and microrheological experiments. To interpret these data, we use a colloid-inspired approach based on a simple patchy model, which explicitly takes into account the anisotropic shape and the charge distribution of the molecules. Combining theory, simulations and experiments, we are able to disentangle self-assembly and intermolecular interactions and to quantitatively describe the concentration dependence of structural and dynamic quantities such as the osmotic compressibility, the collective diffusion coefficient and the zero shear viscosity over the entire range of investigated concentrations. This simple patchy model not only allows us to consistently describe the thermodynamic and dynamic behavior of mAb solutions, but also provides a robust estimate of the attraction between their binding sites. It will thus be an ideal starting point for future work on antibody formulations, as it provides a quantitative assessment of the effects of additional excipients or chemical modifications on antibody interactions, and a prediction of their effect on solution viscosity.Immunoglobulin gamma (IgG) constitutes the major antibody isotype found in serum and takes part in the immune response following an infection to the body. IgGs contain three structured domains: two antigen binding domains (FAB) and one so-called constant domain (FC) arranged in a Y shape via a flexible hinge region. The specific details of such a hinge region further classify the IgGs into four subclasses: IgG1, IgG2, IgG3 and IgG4. In the biopharmaceutical industry, monoclonal antibodies (mAb) based on IgGs are a major platform for potential drug candidates, with more than 20 mAb based drugs available on the market and more in development [1,2]. The popularity of these macromolecules is due to a large flexibility in molecular recognition thanks to the variable portions of the FAB, a long half-life time in the body, and the possibility of humanization minimizing the risk of immunogenicity.In order for mAbs to become a successful pharmaceutical product, not only a biological effect but also a high chemical and formulation stability of the solutions is required. Generally, for mAb based drugs, a high concentration formulation of the order of 100 g/L or more is desirable [3,4]. However, in many cases mAb solutions at these concentrations exhibit dramatically altered flow * present address: Copenhagen Business School, properties, resulting in serious challenges during production and when administering the drug.The flow p...

We study the self-assembly of colloidal magnetic particles permanently cross-linked into polymer-like structures with different topologies, that we call supracolloidal magnetic polymers (SMPs). In order to understand the influence of the interparticle permanent links, we investigate SMPs holding the main topologies observed in the self-assembly of non-cross-linked magnetic particles via grand canonical Monte Carlo simulations: chains, rings and simple branched structures. Here, using molecular dynamics simulations, we focus on systems of SMP pairs. Our results evidence that the presence of crosslinkers leads to the formation of new types of aggregates, not previously observed for individual magnetic colloids. ARTICLE HISTORY

We employ a method based on Monte Carlo grand-canonical simulations to precisely calculate partition functions of non-interacting chains and rings formed by dipolar hard spheres (DHS) at low temperature. The extended low temperature region offered by such cluster calculations, compared to what had been previously achieved with standard simulations, opens up the possibility of exploring a part of the DHS phase diagram which was inaccessible before. The reported results offer the unique opportunity of verifying well-established theoretical models based on the ideal gas of cluster approximation in order to clarify their range of validity. They also provide the basis for future studies in which cluster-cluster interactions will be included.

No abstract

No abstract