Alginate hydrogels are biocompatible, biodegradable, low-cost, and widely used as bioinks, cell encapsulates, three-dimensional culture matrices, drug delivery systems, and scaffolds for tissue engineering. Nevertheless, their limited stiffness hinders their use for certain biomedical applications. Many research groups have tried to address this problem by reinforcing alginate hydrogels with graphene, carbon nanotubes, or silver nanoparticles. However, these materials present nanotoxicity issues, limiting their use for biomedical applications. Other studies show that electrospinning or wet spinning can be used to fabricate biocompatible, micro- and nanofibers to reinforce hydrogels. As a relatively simple and cheap alternative, in this study we used bioengineered bacteria to fabricate amyloid curli fibers to enhance the stiffness of alginate hydrogels. We have fabricated for the first time bioengineered amyloid curli fibers–hydrogel composites and characterized them by a combination of (i) atomic force microscopy (AFM) to measure the Young’s modulus of the bioengineered amyloid curli fibers and study their topography, (ii) nanoindentation to measure the Young’s modulus of the amyloid curli fibers–alginate nanocomposite hydrogels, and (iii) Fourier-transform infrared spectroscopy (FTIR) to analyze their composition. The fabricated nanocomposites resulted in a highly improved Young’s modulus (up to 4-fold) and showed very similar physical and chemical properties, opening the window for their use in applications where the properties alginate hydrogels are convenient but do not match the stiffness needed.

AFM-based maps of elastic modulus superimposed on topography for the case with and without asphaltene inhibitor.

Embryonic muscle forces are necessary for normal vertebral development and spinal curvature, but their involvement in intervertebral disc (IVD) development remains unclear. The aim of the current study was to determine how muscle contractions affect (1) notochord involution and vertebral segmentation, and (2) IVD development including the mechanical properties and morphology, as well as collagen fibre alignment in the annulus fibrosus. Muscular dysgenesis (mdg) mice were harvested at three prenatal stages: at Theiler Stage (TS)22 when notochord involution starts, at TS24 when involution is complete, and at TS27 when the IVD is formed. Vertebral and IVD development were characterised using histology, immunofluorescence, and indentation testing. The results revealed that notochord involution and vertebral segmentation occurred independently of muscle contractions between TS22 and TS24. However, in the absence of muscle contractions, we found vertebral fusion in the cervical region at TS27, along with (i) a displacement of the nucleus pulposus towards the dorsal side, (ii) a disruption of the structural arrangement of collagen in the annulus fibrosus, and (iii) an increase in viscous behaviour of the annulus fibrosus. These findings emphasise the important role of mechanical forces during IVD development, and demonstrate a critical role of muscle loading during development to enable proper annulus fibrosus formation. They further suggest a need for mechanical loading in the creation of fibre-reinforced tissue engineering replacement IVDs as a therapy for IVD degeneration.

Fouling of oil-exposed surfaces remains a crucial issue due to the continued importance of oil as the world's primary energy source. The key perpetrators in crude oil fouling have been identified as asphaltenes, a poorly-described mixture of diverse polyfunctional molecules that form part of the heaviest fractions of oil.Asphaltenes are responsible for a decrease in oil production and energy efficiency, and an increase in the risk of environmental hazards. Hence, understanding and managing systems that are prone to fouling is of great value but constitutes a 2 Confidential challenge due to their complexity. In an effort to reduce that complexity, a study of a synthesised foulant of archipelago structure is presented. An alternative perspective on previously described solubility and aggregation mechanisms (eg. Critical Nanoaggrerate Concentration, Critical Clustering Concentration) is offered since the characterised system favours a continuous distribution of n-mers instead.A battery of experimental and modelling techniques have been employed to link the bulk and interfacial behaviour of a representative foulant monomer to effective fouling mitigation strategies. This systematic approach defines a new multiscale methodology in the investigation of fouling systems.

Many insects use adhesive organs to climb. The ability to cling to surfaces is advantageous but is increasingly challenged as animals grow, due to the associated reduction in surface-to-volume ratio. Previous work has demonstrated that some climbing animals overcome this scaling problem by systematically altering the maximum force per area that their adhesive pads can sustain; their adhesive organs become more efficient as they grow, an observation which is also of substantial relevance for the design of bioinspired adhesives. What is the origin of this change in efficiency? In insects, adhesive contact is mediated by a thin film of a liquid, thought to increase adhesive performance via capillary and viscous forces. Here, we use interference reflection microscopy and dewetting experiments to measure the contact angle and dewetting speed of the secretion of pre-tarsal adhesive pads of Indian stick insects, varying in mass by over two orders of magnitude. Neither contact angle nor dewetting speed change significantly with body mass, suggesting that the key physical properties of the pad secretion—its surface tension and viscosity—are size-invariant. Thus, the observed change in pad efficiency is unlikely to arise from systematic changes of the physical properties of the pad secretion; the functional role of the secretion remains unclear.

Carbonaceous deposits in oil exposed surfaces are responsible for compromising performance and reducing profitability across the hydrocarbons value chain. In particular, in upstream operation, fouling between the well and the production facility has been found to reduce flow, availability and reliability resulting in lost production. Thus, a better understanding of the processes leading to the deposition of these complex and heavy organic compounds is required, since it is unclear whether they primarily aggregate in the liquid phase or at the liquid-solid interface. In an effort to understand the mechanisms behind deposition, this study uses different modalities of atomic force microscopy (AFM) to characterise relevant metallic, oil exposed surfaces with deposits already on them. More specifically, in this post-mortem analysis, surfaces exposed to oil with and without the presence of an inhibitor are imaged in an effort to pinpoint the effect of the inhibitor on deposition.

No abstract

No abstract