The lubrication mechanism in synovial fluid and joints is not yet fully understood. Nevertheless, intermolecular interactions between various neutral and ionic species including large macromolecular systems and simple inorganic ions are the key to understanding the excellent lubrication performance. An important tool for characterizing the intermolecular forces and their structural consequences is molecular dynamics. Albumin is one of the major components in synovial fluid. Its electrostatic properties, including the ability to form molecular complexes, are closely related to pH, solvation, and the presence of ions. In the context of synovial fluid, it is relevant to describe the possible interactions between albumin and hyaluronate, taking into account solution composition effects. In this study, the influence of Na⁺, Mg²⁺, and Ca²⁺ ions on human serum albumin–hyaluronan interactions were examined using molecular dynamics tools. It was established that the presence of divalent cations, and especially Ca²⁺, contributes mostly to the increase of the affinity between hyaluronan and albumin, which is associated with charge compensation in negatively charged hyaluronan and albumin. Furthermore, the most probable binding sites were structurally and energetically characterized. The indicated moieties exhibit a locally positive charge which enables hyaluronate binding (direct and water mediated).

Synthesis of graphene in 2004 stimulated wide interest in potential application of 2D materials in catalysis, optoelectronics, biotechnology and construction of sensing devices. In the presented study interactions between graphene sheets and phospholipid bilayers are examined using steered molecular dynamics simulations. Graphene sheets of different sizes were inserted into bilayer and subsequently withdrawn from it at two different rates (1 m/s and 2 m/s). In some cases, nanoindentation led to substantial damage of the phospholipid bilayer, however an effective self-sealing process occurred even after significant degradation. The average force and work, deflection of the membrane during indentation, withdrawal processes, and structural changes caused by moving sheets are discussed. These quantities are utilized to estimate the suitability of graphene sheets for targeted drug delivery or other nanomedicine tools. The results are compared with those obtained for other nanostructures such as homogeneous and heterogeneous nanotubes.