Improving the bioactivity and mechanical properties of poly(ethylene glycol)-based hydrogels through a supramolecular support network.

Most synthetic hydrogels are formed through radical polymerization to yield a homogenous covalent meshwork. In contrast, natural hydrogels form through mechanisms involving both covalent assembly and supramolecular interactions. In this communication, we expand the capabilities of covalent poly(ethylene glycol) (PEG) networks through co-assembly of supramolecular peptide nanofibers.

Mechanical and biological behavior of double network hydrogels reinforced with alginate versus gellan gum.

Alginate and gellan gum have both been used by researchers as reinforcing networks to create tough and biocompatible polyethylene glycol (PEG) based double network (DN) hydrogels; however, the relative advantages and disadvantages of each approach are not understood. This study directly compares the mechanical and biological properties of polyethylene glycol di-methacrylate (PEGDMA) hybrid DN hydrogels reinforced with either gellan gum or sodium alginate using PEGDMA concentrations from 10 to 20 wt% and reinforcing network concentrations of 1 and 2 wt%. The findings demonstrate that gellan gum reinforcement is more effective at increasing the strength, stiffness, and toughness of PEGDMA DN hydrogels.

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.

Magnetic Nanofibrous Hydrogels for Dynamic Control of Stem Cell Differentiation.

The extracellular matrix in tissue consists of complex heterogeneous soft materials with hierarchical structure and dynamic mechanical properties dictating cell and tissue level function. In many natural matrices, there are nanofibrous structures that serve to guide cell activity and dictate the form and function of tissue. Synthetic hydrogels with integrated nanofibers can mimic the structural properties of native tissue; however, model systems with dynamic mechanical properties remain elusive.

: a computer program for extracting a pair distribution function from an electron diffraction pattern for the structural analysis of materials.

Pair distribution function (PDF) analysis is a powerful technique to understand atomic scale structure in materials science. Unlike X-ray diffraction (XRD)-based PDF analysis, the PDF calculated from electron diffraction patterns (EDPs) using transmission electron microscopy can provide structural information from specific locations with high spatial resolution. The present work describes a new software tool for both periodic and amorphous structures that addresses several practical challenges in calculating the PDF from EDPs.

Defect Engineering of a High-Entropy Metallic Glass Surface for High-Performance Overall Water Splitting at Ampere-Level Current Densities.

Platinum-based electrocatalysts possess high water electrolysis activity and are essential components for hydrogen evolution reaction (HER). A major challenge, however, is how to break the cost-efficiency trade-off. Here, a novel defect engineering strategy is presented to construct a nanoporous (FeCoNiB ) Pt (atomic %) high-entropy metallic glass (HEMG) with a nanocrystalline surface structure that contains large amounts of lattice distortion and stacking faults to achieve excellent electrocatalytic performance using only 3 at% of Pt.

Synthesis of Submicrometric Chitosan Particles Loaded with Calcium Phosphate for Biomedical Applications.

Chitosan particles loaded with dibasic calcium phosphate anhydrous (DCPA) is a promising strategy for combining antimicrobial and osteoconduction properties in regenerative medicine. However, mostly micrometer-sized particles have been reported in the literature, limiting their use and reducing their effect in the biomedical field. We have recently overcome this limitation by developing submicrometer-sized particles with electrospray technique.

Fatigue and wear of human tooth enamel: A review.

Human tooth enamel must withstand the cyclic contact forces, wear, and corrosion processes involved with typical oral functions. Furthermore, unlike other human tissues, dental enamel does not have a significant capacity for healing or self-repair and thus the longevity of natural teeth in the oral environment depends to a large degree on the fatigue and wear properties of enamel. The purpose of this review is to provide an overview of our understanding of the fatigue and wear mechanisms of human enamel and how they relate to in vivo observations of tooth damage in the complex oral environment.

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).

Structural aspects controlling the mechanical and biological properties of tough, double network hydrogels.

Anticipating an increasing demand for hybrid double network (DN) hydrogels in biomedicine and biotechnology, this study evaluated the effects of each network on the mechanical and biological properties. Polyethylene glycol (PEG) (meth)acrylate hydrogels with varied monomer molecular weights and architectures (linear vs. 4-arm) were produced with and without an added ionically bonded alginate network and their mechanical properties were characterized using compression testing.

Enhanced perfusion of elliptical wound closures using a novel adhesive suture retention device.

Background And Aims: The purpose of this investigation was to test the hypothesis that a novel adhesive retention suture device (ARSD) can increase perfusion at elliptical wound closures by distributing stress away from the suture site.

Methods: Stress in the skin around a suture both with and without support from an ARSD was evaluated using a finite element model. A single-center, randomized split-scar comparison trial using laser speckle contrast analysis was used to quantify the perfusion at elliptical wound closures in human patients both with and without an ARSD.

Force-mediated molecule release from double network hydrogels.

The incorporation of mechanosensitive linkages into polymers has led to materials with dynamic force responsivity. Here we report oxanorbornadiene cross-linked double network hydrogels that release molecules through a force-mediated retro Diels-Alder reaction. The molecular design and tough double network of polyacrylamide and alginate promote significantly higher activation at substantially less force than pure polymer systems.

Fiber reinforcement of a resin modified glass ionomer cement.

Objectives: Understand how discontinuous short glass fibers and braided long fibers can be effectively used to reinforce a resin modified glass ionomer cement (RMGIC) for carious lesion restorations.

Methods: Two control groups (powder/liquid kit and capsule) were prepared from a light cured RMGIC. Either discontinuous short glass fibers or braided polyethylene fiber ribbons were used as a reinforcement both with and without pre-impregnation with resin.

Anisotropic fracture resistance of avian eggshell.

In order to understand the fracture toughness anisotropy of avian eggshells, we have investigated eggshells of the emu (Dromaius novaehollandiae) whereby the large size (~13 cm × 9.5 cm) enabled the fabrication of beam samples in various orientations. The emu eggshell was found to have a hierarchical microstructure similar to chicken eggshell, with the only significant difference being the absence of a continuous cuticle layer.

Role of Boron in Enhancing Electron Delocalization to Improve Catalytic Activity of Fe-Based Metallic Glasses for Persulfate-Based Advanced Oxidation.

Metallic glasses (MGs) with superior catalytic performance have recently been recognized as attractive candidates for wastewater treatment. However, further improving their performance will require knowledge of how to precisely regulate their electronic structures via compositional control. Here, two Fe-based MGs (FeSiB and FeSiB) were prepared to compare how slightly altering boron content affected their electronic structure and catalytic performance.

Development of novel dental restorative composites with dibasic calcium phosphate loaded chitosan fillers.

Unlabelled: The incorporation of antimicrobial agents in restorative dental composites has the potential to slow the development of carious lesions.

Objective: The objectives of the present study were to develop experimental composite resins with chitosan or chitosan loaded with dibasic calcium phosphate anhydrous (DCPA) particles and to demonstrate their antimicrobial potential without loss of mechanical properties or biocompatibility.

Methods: Chitosan and chitosan/DCPA particles were synthetized by the electrospray method.

A diet high in fat and fructose adversely affects osseointegration of titanium implants in rats.

Objectives: Diet-induced metabolic dysfunction such as type 2 diabetes mellitus increases the risk of implant failure in both dental and orthopaedic settings. We hypothesised that a diet high in fat and fructose would adversely affect peri-implant bone structure and function including osseointegration.

Materials And Methods: Thirty female Sprague-Dawley rats were divided into three groups (n = 10), control group (normal chow) and two intervention groups on a high-fat (60%), high-fructose (20%; HFHF) diet.

Forces on sutures when closing excisional wounds using the rule of halves.

Background: To close elliptical excisions, surgeons commonly use the rule of halves which involves initially closing of the middle portion of the wound, followed by closure of the remaining halves. Understanding the forces required for suturing such wounds can aid excisional surgery planning to decrease complications and improve wound healing.

Methods: Following full thickness excision for removal of skin cancers, back wounds with 3:1 ratio of length-to-width were closed using the rule of halves.

Effect of cooling protocol on mechanical properties and microstructure of dental veneering ceramics.

Objectives: Understand how cooling protocols control the microstructure and mechanical properties of veneering porcelains.

Methods: Two porcelain powders were selected, one used to veneer metallic frameworks (VM13) and one for zirconia frameworks (VM9). After the last firing cycle, the monolithic specimens were subjected to two cooling protocols: slow and fast.

In vivo stress relaxation of human scalp.

Objective: Conduct a first in vivo study on the large deformation stress relaxation behavior of the human scalp.

Methods: This study was conducted during Mohs micrographic surgery of the scalp of 14 patients aged 59-90 with wounds initially ranging from 9 to 41 mm wide. The initial wound diameter was measured under zero applied force.