Oxide glasses are an integral part of the modern world, but their usefulness can be limited by their characteristic brittleness at room temperature. We show that amorphous aluminum oxide can permanently deform without fracture at room temperature and high strain rate by a viscous creep mechanism. These thin-films can reach flow stress at room temperature and can flow plastically up to a total elongation of 100%, provided that the material is dense and free of geometrical flaws. Our study demonstrates a much higher ductility for an amorphous oxide at low temperature than previous observations. This discovery may facilitate the realization of damage-tolerant glass materials that contribute in new ways, with the potential to improve the mechanical resistance and reliability of applications such as electronic devices and batteries.

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Typical silicate bioactive glasses are known to crystallize readily during the processing of porous scaffolds. While such crystallization does not fully suppress the bioactivity, the presence of significantly large amounts of crystals leads to a decrease in the rate of reaction of the glass and an uncontrolled release of ions. Furthermore, due to the non-congruent dissolution of silicate glasses, these materials have been shown to remain within the surgical site even 14 years postoperation. Therefore, a need for bioactive materials that can dissolve with higher conversion rates and more effectively are required. Within this work, boron was introduced, in the FDA approved S53P4 glass, at the expense of SiO2. The crystallization and sintering-ability of the newly developed glasses were investigated by differential thermal analysis. All the glasses were found to crystallize primarily from the surface, and the crystal phase precipitating was dependent upon the quantity of B2O3 incorporated. The rate of crystallization was found to be lower for the glasses were 25, 50 and 75 % of the SiO2 was replaced with B2O3. These glasses were further sintered into porous scaffolds using simple heat sintering. The impact of glass particles size and heat treatment temperature on the scaffolds porosity and average pore size was investigated. Scaffolds with porosity ranging from 10 to 60 % with compressive strength ranging from 1 to 35 MPa, were produced. The scaffolds remained amorphous during processing and their ability to rapidly precipitate hydroxycarbonated apatite was maintained. This is of particular interest in the field of tissue engineering as the scaffolds degradation and reaction was generally faster and offers higher controllability as opposed to current partially/fully crystallized scaffolds obtained from the FDA approved bioactive glasses. IntroductionAs of today, autografts are still the gold standard for the repair of large bone defects. However, with the aging and growing population, the number of surgical intervention to regenerate bone defects are increasing. The limited supply and patient site morbidity is a well-known disadvantage and problem [1][2]. Allografts are an option. However, the limited tissue bank as well as the higher risk for infection and cellular and humoral immune reactions limits their usage [3]. The quest for synthetic biomaterials to replace the autografts is more than two decades old. However, as of today no materials have shown as promising a result as autografts. Q. Chen et al. have reported the optimum characteristic that the synthetic materials should have to find great potential as bone grafts [4]. The bone graft should be a 3D construct (3D scaffold) not only biocompatible, but ultimately biodegradable and osteoconductive with highly interconnected porosity. Pore size should be no less than 100 µm to allow cell and fluid penetration as well as angiogenesis. In general, interconnected pores of at least 100 µm and an open porosity of over 50% is considered the minimum requirement for ti...

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Biopolymers are attractive candidates to fabricate biocompatible hydrogels, but the low water solubility of most of them at physiological pH has hindered their applications. To prepare a water-soluble derivative of chitosan (WSC) biopolymer, it was grafted with a small anionic amino acid, l-glutamic acid, using a single-step 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide coupling reaction. This resulted in a zwitterion-tethered structure onto the polymer backbone. The degree of substitution range was 13-16 ± 1.25%, which was controlled by varying the feeding reagent ratios. Differential scanning calorimetry- and X-ray diffraction-based analysis confirmed a transition from  amorphous into a moderately amorphous/crystalline morphology after amino acid grafting, which made the derivative water-soluble at physiological pH. Composite hydrogels gelated within 60 s when using this WSC together with benzaldehyde-terminated 4-arm poly(ethylene glycol) as cross-linker. The compressive modulus of these hydrogels could be easily tuned between 4.0 ± 1.0 and 31 ± 2.5 kPa, either by changing the cross-linker concentration or total solid content in the final gel. The gels were injectable at the lowest cross-linker as well as total solid content, due to the enhanced elastic behavior. These hydrogels showed biodegradability during a 1 month incubation period in phosphate-buffered saline with weight remaining of 60 ± 1.5 and 44 ± 1.45% at pHs 7.4 and 6.5, respectively. The cytocompatibility of the gels was tested using the fibroblast cell line (i.e., WI-38), which showed good cell viability on the gel surface. Therefore, these hydrogels could be an important injectable biomaterial for delivery purpose in the future.

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