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In this study, we present a hydrogel fabrication utilizing a water-insoluble, low-molecular-weight organogelator by the surfactant-mediated gelation (SMG). Specifically, we employed a nonionic surfactant (poly(oxyethylene) sorbitan monooleate, Tween 80) and an organogelator (12-hydroxyoctadecanoic acid, 12-HOA) to produce hydrogels. Gelation experiments conducted at varying concentrations of surfactant and gelator demonstrated successful hydrogel formation in the water/Tween 80/12-HOA system. Moreover, we observed a significant dependence of surfactant concentration on gelation ability. The sol-gel transition temperature was found to be influenced by both the gelator and surfactant concentrations. Optical and electron microscopy analyses revealed that the SMG hydrogels comprised an entangled network of fibers with micrometer-scale widths, formed as bundles of submicron-wide fibers, and further composed of fine fibers measuring several tens of nanometers in width. These fine fibers exhibited a left-handed helical structure. Small- and wide-angle X-ray scattering corroborated the presence of a lamellar structure within the fine fibers, displaying a triclinic subcell morphology. The coexistence of micelles with the fiber network was confirmed through small-angle neutron scattering and UV–vis spectroscopy. Furthermore, dynamic viscoelasticity tests demonstrated that the SMG hydrogels exhibited typical solid-like properties indicative of gel behavior.

The porosity in minerals contributes to enhanced permeability for fluid flow in natural systems and engineering processes. Porosity can be created by fluid-mediated mineral replacement reactions. Such reaction-induced porosity can evolve with time, yet the mechanisms and kinetics of porosity creation and evolution remain poorly understood. This thesis presents experimental investigations on the creation and evolution of mineral porosity in two model replacement reactions, i.e., the replacement of calcite by gypsum and anhydrite with a positive volume change and the replacement of pentlandite by violarite and millerite with a negative volume change. These replacement reactions were conducted under mildly acidic hydrothermal conditions for up to 18 months, and the mineralogy, microstructure and porosity of the reaction products were quantitatively analysed by powder X-ray diffraction, (ultra) small-angle neutron scattering, high resolution scanning electron microscopy, focused-ion beam scanning electron microscopy, and X-ray micro-tomography. The results showed that porosity creation and evolution are highly dependent on mineral systems and reaction conditions. In the calcite-gypsum-anhydrite mineral system, the experiments at 25-60 °C produced intragranular nanopores in gypsum replacing calcite. Because of the positive volume change, gypsum overgrowth also occurred on the grain surface, and the gypsum in the overgrowth region contained intergranular micropores. Porosity coarsening was rapid (a few weeks) in the replacement region, leading to the formation of micro-voids in the core of gypsum grains. The replacement reaction was sensitive to temperature. When the experiments were conducted at a higher temperature of 220 °C, anhydrite was formed instead of gypsum. Porosity evolution in anhydrite was different when compared to gypsum at lower temperatures. In the pentlandite-violarite-millerite mineral system, only replacement occurred, likely because the negative volum

The porosity in minerals contributes to enhanced permeability for fluid flow in natural systems and engineering processes. Porosity can be created by fluid-mediated mineral replacement reactions. Such reaction-induced porosity can evolve with time, yet the mechanisms and kinetics of porosity creation and evolution remain poorly understood. This thesis presents experimental investigations on the creation and evolution of mineral porosity in two model replacement reactions, i.e., the replacement of calcite by gypsum and anhydrite with a positive volume change and the replacement of pentlandite by violarite and millerite with a negative volume change. These replacement reactions were conducted under mildly acidic hydrothermal conditions for up to 18 months, and the mineralogy, microstructure and porosity of the reaction products were quantitatively analysed by powder X-ray diffraction, (ultra) small-angle neutron scattering, high resolution scanning electron microscopy, focused-ion beam scanning electron microscopy, and X-ray micro-tomography. The results showed that porosity creation and evolution are highly dependent on mineral systems and reaction conditions. In the calcite-gypsum-anhydrite mineral system, the experiments at 25-60 °C produced intragranular nanopores in gypsum replacing calcite. Because of the positive volume change, gypsum overgrowth also occurred on the grain surface, and the gypsum in the overgrowth region contained intergranular micropores. Porosity coarsening was rapid (a few weeks) in the replacement region, leading to the formation of micro-voids in the core of gypsum grains. The replacement reaction was sensitive to temperature. When the experiments were conducted at a higher temperature of 220 °C, anhydrite was formed instead of gypsum. Porosity evolution in anhydrite was different when compared to gypsum at lower temperatures. In the pentlandite-violarite-millerite mineral system, only replacement occurred, likely because the negative volum

Bovine milk aS2-casein, an intrinsically disordered protein, readily forms amyloid fibrils in vitro and is implicated in the formation of amyloid fibril deposits in mammary tissue. Its two cysteine residues participate in the formation of either intra- or intermolecular disulphide bonds, generating monomer and dimer species. X-ray solution scattering measurements indicated that both forms of the protein adopt large, spherical oligomers at 20C. Upon incubation at 37C, the disulphide-linked dimer showed a significantly greater propensity to form amyloid fibrils than its monomeric counterpart. Thioflavin T fluorescence, circular dichroism and infrared spectra were consistent with one or both of the dimer isomers (in a parallel or antiparallel arrangement) being predisposed toward an ordered, amyloid-like structure. Limited proteolysis experiments indicated that the region from Ala^81 to Lys^113 is incorporated into the fibril core, implying that this region, which is predicted by several algorithms to be amyloidogenic, initiates fibril formation of aS2-casein. The partial conservation of the cysteine motif and the frequent occurrence of disulphide-linked dimers in mammalian milks despite the associated risk of mammary amyloidosis, suggest that the dimeric conformation of aS2-casein is a functional, yet amyloidogenic, structure.

Biomimetic hydrogels offer a new platform for hierarchical structure-controlled, tough, biocompatible, mechanically tunable, and printable gels for regenerative medicine. Herein, we report for the first time the detailed effects of various kinds of nanocellulose, namely, bacterial nanocellulose, cellulose nanofibers, and cellulose nanocrystals on the morphology, structure-property relationship, and 3D printability of the photochemically cross-linked regenerated silk fibroin (RSF)/nanocellulose composite hydrogels. The hierarchical structure of fabricated biomimetic hydrogels was both qualitatively and quantitatively investigated by scanning electron microscopy and small/ultrasmall-angle neutron scattering, whereas their mechanical properties were assessed using rheology, tensile, and indentation tests. The micropore size and interhydrophobic domain distance of fabricated hydrogels were tuned in the range of 1.8-9.2 μm and 4.5-17.7 nm, respectively. The composite hydrogels exhibit superior viscoelastic, compressive, and tensile mechanical properties compared to pristine RSF hydrogel, where the shear storage modulus, compression modulus, young's modulus, and tensile toughness were tuned in the range of 0.4-1.4, 1.3-3.6, 2.2-14.0 MPa, and 16.7-108.3 kJ/m3, respectively. Moreover, the obtained mechanical modulus of the composite hydrogels in terms of shear, tensile, and compression are comparable to articular cartilage (0.4-1.6 MPa), native femoral artery (∼9.0 MPa), and human medial meniscus (∼1.0 MPa) tissues, respectively, which demonstrate their potential for a wide range of tissue engineering applications. The whisker form of nanocellulose was observed to enhance the printability of composite hydrogels, whereas the fiber form enhanced the overall toughness of the composite hydrogels and promoted the fibroblast cell attachment, viability, and proliferation. The results presented here have implications for both fundamental understanding and potential applications of