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Highlights • A new method for determining the in situ surface dilational rate was developed. • Dynamic surface dilational rate of an impinging drop of Triton X-100 solution was obtained. • Surface dilational rate showed a strong oscillation at the initial stage of impact. • Dynamic surface dilational rates of water and Triton X-100 solution drops were compared. Abstract The impact dynamics of a solution drop of Triton X-100 impinging on a paraffin film was studied, specifically to develop a new method for evaluating the in situ surface dilational rate, λ. The drop images (side and top views) during the impingement process were sequentially digitized and used to calculate the interfacial areas of the liquid-air and liquid-solid interfaces. The data of interfacial area were then used to calculate the relaxation of λ. The surface dilational rate showed a strong oscillation at the beginning of the drop impact. It oscillated from 0 down to −390/s, up to 290/s, and then down to −200/s. This surface dilational rate is far above 2.4/s, which is the lower limit of λ for an expanding pendant bubble in a Triton X-100 solution with an isolated air-liquid surface (Lin et al., 2017). A simple but useful theoretical framework is given for the calculation of the dynamic surface dilational rate, surface concentration and surface tension of an impinging drop of surfactant solution. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Muscular disease has debilitating effects with severe damage leading to death. Our knowledge of muscle biology, disease and treatment is largely derived from non-human cell models, even though non-human cells are known to differ from human cells in their biochemical responses. Attempts to develop highly sought after in vitro human cell models have been plagued by early cell delamination and difficulties in achieving human myotube culture in vitro. In this work, we developed polyurethane acrylate (PUA) materials to support long-term in vitro culture of human skeletal muscle tissue. Using a constant base with modulated crosslink density we were able to vary the material modulus while keeping surface chemistry and roughness constant. While previous studies have focused on materials that mimic soft muscle tissue with stiffness ca. 12 kPa, we investigated materials with tendon-like surface moduli in the higher 150 MPa to 2.4 GPa range, which has remained unexplored. We found that PUA of an optimal modulus within this range can support human myoblast proliferation, terminal differentiation and sustenance beyond 35 days, without use of any extracellular protein coating. Results show that PUA materials can serve as effective substrates for successful development of human skeletal muscle cell models and are suitable for long-term in vitro studies. Statement of Significance We developed polyurethane acrylates (PUA) to modulate the human skeletal muscle cell growth and maturation in vitro by controlling surface chemistry, morphology and tuning material’s stiffness. PUA was able to maintain muscle cell viability for over a month without any detectable signs of material degradation. The best performing PUA prevented premature cell detachment from the substrate which often hampered long-term muscle cell studies. It also supported muscle cell maturation up to the late stages of differentiation. The significance of these findings lies in the possibility to advance studies on muscle cell biology, disease and therapy by using human muscle cells instead of relying on the widely used animal-based in vitro models. [ABSTRACT FROM AUTHOR]

Abstract: We have prepared a number of silicone-based thermoplastic polyurethane (TPU) nanocomposites and demonstrated an enhancement of in vitro biostability against metal-ion-induced oxidation for potential use in long-term implantable medical devices. Organoclays based on both low-aspect-ratio hectorites and high-aspect-ratio fluoromicas were evaluated after being dual-modified with two quaternary alkyl ammonium salts with differing degrees of polarity. The resultant nanocomposites were tested for in vitro biostability using physiologically relevant oxidizing conditions. Subsequently, the effects of oxidative treatment on the surface degradation and bulk mechanical integrity of the nanocomposites were investigated and compared with the parent TPUs to identify nanocomposites with the most desirable features for long-term implantation. Here, we demonstrate that the low-aspect-ratio organohectorite was delaminated and well dispersed in the nanocomposites. Importantly, these factors gave rise to the enhanced oxidative stability. In addition, the mechanical properties of all nanocomposites were less adversely affected by the oxidative treatment compared to their parent TPUs. These results suggest the potential for improved mechanical integrity and biostability when suitable dual modified organoclays are incorporated in a silicone-based TPU. [Copyright &y& Elsevier]