Impact of heavy alcohol consumption on cortical bone mechanical properties in male rhesus macaques.

Chronic heavy alcohol consumption may influence the skeleton by suppressing intracortical bone remodeling which may impact the quality of bone and its mechanical properties. However, this aspect has not been thoroughly assessed in either humans or animal models whose cortical bone microstructure resembles the microstructure of human cortical bone. The current study is the first to investigate the effects of chronic heavy alcohol consumption on various mechanical properties of bone in a non-human primate model with intracortical remodeling.

Effect of gamma irradiation and supercritical carbon dioxide sterilization with Novakill™ or ethanol on the fracture toughness of cortical bone.

Sterilization of structural bone allografts is a critical process prior to their clinical use in large cortical bone defects. Gamma irradiation protocols are known to affect tissue integrity in a dose dependent manner. Alternative sterilization treatments, such as supercritical carbon dioxide (SCCO ), are gaining popularity due to advantages such as minimal exposure to denaturants, the lack of toxic residues, superior tissue penetration, and minor impacts on mechanical properties including strength and stiffness.

Impact of test environment on the fracture resistance of cortical bone.

Water is a crucial component of bone, affecting the interplay of collagen and minerals and contributing to bone's high strength and ductility. Dehydration has been shown to significantly effect osseous mechanical properties; however, studies comparing the effects of various dehydrating environments on fracture toughness of bone are scarce. Accordingly, the crack resistance curve (R-curve) behavior of human and sheep cortical bone was characterized in a bio-bath, in ambient pressure air, and in scanning electron microscopes (SEMs) under three different environmental conditions (water vapor pressure, air pressure, and high-vacuum).

Challenges and solutions for fabrication of three-dimensional cocultures of neural cell-loaded biomimetic constructs.

Fabrication of three-dimensional (3D) constructs to model body tissues and organs can contribute to research into tissue development and models for studying disease, as well as supporting preclinical drug screening in vitro. Furthermore, 3D constructs can also be used for diagnosis and therapy of disease conditions via lab on a chip and microarrays for diagnosis and engineered products for tissue repair, replacement, and regeneration. While cell culture approaches for studying tissue development and disease in two dimensions are long-established, the translation of this knowledge into 3D environments remains a fertile field of research.

Fucoidan- and carrageenan-based biosynthetic poly(vinyl alcohol) hydrogels for controlled permeation.

Since the permeation of the inflammatory cytokines into hydrogel scaffolds has been shown to cause dysfunction of encapsulated cells, appropriate design strategies to circumvent this are essential. In the present work, it was hypothesized that highly crosslinked PVA-fucoidan and PVA-carrageenan hydrogels can control permeation of the trefoil-shaped inflammatory cytokine IL-1β while allowing the permeation of the globular protein albumin. PVA, fucoidan, and carrageenans were functionalized with methacrylate groups and the functionalized polymers were co-crosslinked by UV photopolymerization.

Visible light mediated PVA-tyramine hydrogels for covalent incorporation and tailorable release of functional growth factors.

The translation of growth factors (GFs) into clinical applications is limited by their low stability in physiological environments. Controlled GF delivery through biomaterial vehicles provides protection from proteases, targeted delivery, and longer term release profiles. However, current methods used to incorporate GFs into biomaterials still present limitations.

Immunomodulatory properties of photopolymerizable fucoidan and carrageenans.

Innovative approaches to the control of immune response to tissue engineering scaffolds is of high priority. IL-10, an anti-inflammatory cytokine, has traditionally been conjugated to synthetic polymers for local immunomodulation. Marine-sulfated polysaccharides have been reported to possess anti-inflammatory properties.

Tissue engineered hydrogels supporting 3D neural networks.

Promoting nerve regeneration requires engineering cellular carriers to physically and biochemically support neuronal growth into a long lasting functional tissue. This study systematically evaluated the capacity of a biosynthetic poly(vinyl alcohol) (PVA) hydrogel to support growth and differentiation of co-encapsulated neurons and glia. A significant challenge is to understand the role of the dynamic degradable hydrogel mechanical properties on expression of relevant cellular morphologies and function.

Multiscale mechanisms of nutritionally induced property variation in spider silks.

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales.

Fitness consequences of plasticity in an extended phenotype.

Like regular phenotypes, extended phenotypes have demonstrable fitness advantages and their properties may vary plastically across environments. However, the fitness advantages of plasticity are only known for a select few extended phenotypes. It is known that the form and functions of spider orb webs can be manipulated by laboratory experiments.

Characteristics of a free-standing film from banana pseudostem nanocellulose generated from TEMPO-mediated oxidation.

Demand for bioplastic, especially for food packaging, increases as the consumers become more aware of the destructive effect of non-biodegradable plastics. Nanocellulose from banana pseudo-stem has great potential to be formed as a bioplastic. This study aimed to characterize the free-standing film produced from banana pseudo-stem nanocellulose that was prepared by TEMPO-mediated oxidation.

Interpenetrating Conducting Hydrogel Materials for Neural Interfacing Electrodes.

Conducting hydrogels (CHs) are an emerging technology in the field of medical electrodes and brain-machine interfaces. The greatest challenge to the fabrication of CH electrodes is the hybridization of dissimilar polymers (conductive polymer and hydrogel) to ensure the formation of interpenetrating polymer networks (IPN) required to achieve both soft and electroactive materials. A new hydrogel system is developed that enables tailored placement of covalently immobilized dopant groups within the hydrogel matrix.

Diet-induced co-variation between architectural and physicochemical plasticity in an extended phenotype.

The adaptive benefits of extended phenotypic plasticity are imprecisely defined due to a paucity of experiments examining traits that are manipulable and measurable across environments. Spider webs are often used as models to explore the adaptive benefits of variations in extended phenotypes across environments. Nonetheless, our understanding of the adaptive nature of the plastic responses of spider webs is impeded when web architectures and silk physicochemical properties appear to co-vary.

In situ formation of poly(vinyl alcohol)-heparin hydrogels for mild encapsulation and prolonged release of basic fibroblast growth factor and vascular endothelial growth factor.

Heparin-based hydrogels are attractive for controlled growth factor delivery, due to the native ability of heparin to bind and stabilize growth factors. Basic fibroblast growth factor and vascular endothelial growth factor are heparin-binding growth factors that synergistically enhance angiogenesis. Mild, in situ encapsulation of both basic fibroblast growth factor and vascular endothelial growth factor and subsequent bioactive dual release has not been demonstrated from heparin-crosslinked hydrogels, and the combined long-term delivery of both growth factors from biomaterials is still a major challenge.

A comparative study of enzyme initiators for crosslinking phenol-functionalized hydrogels for cell encapsulation.

Background: Dityrosine crosslinking in proteins is a bioinspired method of forming hydrogels. This study compares oxidative enzyme initiators for their relative crosslinking efficiency and cytocompatibility using the same phenol group and the same material platform. Four common enzyme and enzyme-like oxidative initiators were probed for resulting material properties and cell viability post-encapsulation.

Evidence of Decoupling Protein Structure from Spidroin Expression in Spider Dragline Silks.

The exceptional strength and extensibility of spider dragline silk have been thought to be facilitated by two spidroins, major ampullate spidroin 1 (MaSp1) and major ampullate spidroin 2 (MaSp2), under the assumption that protein secondary structures are coupled with the expressed spidroins. We tested this assumption for the dragline silk of three co-existing Australian spiders, Argiope keyserlingi, Latrodectus hasselti and Nephila plumipes. We found that silk amino acid compositions did not differ among spiders collected in May.

Producing 3D neuronal networks in hydrogels for living bionic device interfaces.

Hydrogels hold significant promise for supporting cell based therapies in the field of bioelectrodes. It has been proposed that tissue engineering principles can be used to improve the integration of neural interfacing electrodes. Degradable hydrogels based on poly (vinyl alcohol) functionalised with tyramine (PVA-Tyr) have been shown to support covalent incorporation of non-modified tyrosine rich proteins within synthetic hydrogels.

Tailoring Stimuli Responsiveness using Dynamic Covalent Cross-Linking of Poly(vinyl alcohol)-Heparin Hydrogels for Controlled Cell and Growth Factor Delivery.

Heparin-based hydrogels are attractive for cell encapsulation and drug delivery because of the ability of heparin to bind native proteins. However, heparin-based hydrogels have received little attention for their potential as stimuli-sensitive materials. Biosynthetic, poly(vinyl alcohol) (PVA)-heparin hydrogels were formed using dynamic, covalent cross-linking.

Copolymerization of an indazole ligand into the self-polymerization of dopamine for enhanced binding with metal ions.

5,6-Dihydroxy-1H-indazole (DHI) is able to self-polymerize through the same mussel-inspired chemistry responsible for generating poly(dopamine) (PDA), demonstrating the potential to expand this class of catecholamine-exclusive chemistry onto heterocyclic catechol derivatives for the preparation of functional materials. Although DHI exhibits slower polymerization kinetics compared to dopamine, the two chemical species are compatibly polymerizable under the same reaction conditions and allow the preparation of copolymer coatings in different molar ratios. Of these copolymers, the 1 : 3-copolymer (DHI-to-dopamine ratio) has demonstrated adequate structural stability as a polymer coating.

Promoting Cell Survival and Proliferation in Degradable Poly(vinyl alcohol)-Tyramine Hydrogels.

A photopolymerizable-tyraminated poly(vinyl alcohol) (PVA-Tyr) system that has the ability to covalently bind proteins in their native state was evaluated as a platform for cell encapsulation. However, a key hurdle to this system is the radicals generated during the cross-linking that can cause oxidative stress to the cells. This research hypothesized that incorporation of anti-oxidative proteins (sericin and gelatin) into PVA-Tyr gels would mitigate any toxicity caused by the radicals.

Bioactivity of permselective PVA hydrogels with mixed ECM analogues.

The presentation of multiple biological cues, which simulate the natural in vivo cell environment within artificial implants, has recently been identified as crucial for achieving complex cellular functions. The incorporation of two or more biological cues within a largely synthetic network can provide a simplified model of multifunctional ECM presentation to encapsulated cells. Therefore, the aim of this study was to examine the effects of simultaneously and covalently incorporating two dissimilar biological molecules, heparin and gelatin, within a PVA hydrogel.

In vivo delivery of functional Flightless I siRNA using layer-by-layer polymer surface modification.

Gene silencing using small interfering RNA has been proposed as a therapy for cancer, viral infections and other diseases. This study aimed to investigate whether layer-by-layer polymer surface modification could deliver small interfering RNA to decrease fibrotic processes associated with medical device implantation. Anti-green fluorescent protein labelled small interfering RNA was applied to tissue culture plates and polyurethane using a layer-by-layer technique with small interfering RNA and poly-L-lysine.

Structural and permeability characterization of biosynthetic PVA hydrogels designed for cell-based therapy.

Incorporation of extracellular matrix (ECM) components to synthetic hydrogels has been shown to be the key for successful cell encapsulation devices, by providing a biofunctional microenvironment for the encapsulated cells. However, the influence of adding ECM components into synthetic hydrogels on the permeability as well as the physical and mechanical properties of the hydrogel has had little attention. Therefore, the aim of this study was to investigate the effect of incorporated ECM analogues on the permeability performance of permselective synthetic poly(vinyl alcohol) (PVA) hydrogels in addition to examining the physico-mechanical characteristics.