1,509 research outputs found
Silicon Nitride and Metalized Halloysite Nanotube for Enhanced Bacteriostatic Activity, Wound Healing, and Tissue Regeneration
Metals such as titanium have been used in implants, but there are often cases of infection and rejection of the implant from the body. In the past decade, the use of metal nanoparticles has seen increasing demand as an alternative treatment for reducing microbial infections, leading to progress in orthopedic surgery and wound healing. Recent investigations have developed new biomaterial bone substitutes with novel structural, biological, and mechanical properties. Advanced ceramic materials, such as Si3N4, may fulfill all the requirements above and represent a promising alternative to metals or polymers. However, the above mentioned materials have limitations because they are not biodegradable, not biocompatible, and do not contain inherent antimicrobial properties. This research is subdivided into three projects. First, it aims to introduce antibacterial properties into fabricated 3D implants by combining antimicrobial and base polymer powders before processing, which will make the material biocompatible and biodegradable. Second, it aims to fabricate multifunctional antimicrobial blow-spun nanocomposite fiber to facilitate wound healing and reduce microbial infection. Third, it aims to fabricate a biodegradable nanocomposite hydrogel patch for the development of chronic wound healing treatment.
A patented electrodeposition process was used to coat magnesium (Mg) on the HNT outer surfaces to add additional antimicrobial properties. Gentamicin sulfate was vacuum loaded into the lumen of the HNTs, which had already been coated with Mg. Si3N4 was added to the gentamicin-loaded MgHNT to promote cell adhesion and differentiation, and the resulting composite was then 3D printed/blow-spun into the required shapes according to the testing protocol.
FTIR, XRD, and SEM images showed the presence of magnesium on halloysite. cytotoxicity tests show that the fabricated nanocomposites were not toxic to mammalian cells. The results of the antimicrobial activity showed a pronounced inhibition of bacterial growth in all fabricated nanocomposites. Cell proliferation assays showed that Si3N4 enhanced proliferation in all nanocomposites. The porosity test showed that the addition of Si3N4 does not affect the porosity and the cell attachment. The histological staining showed an increase in both calcium and mucopolysaccharides. The nanocomposite shows excellent mechanical properties and a lower contact angle after surface coating with protein. Nanocomposites degraded slowly during the biodegradation test, enabling the growth of new bone cells. Si3N4 gives the cellular surface roughness structure, hydrophilicity, and protein adsorption capability
Stem Cells in Domestic Animals
Stem cells are an attractive tool for cell-based therapies in regenerative medicine, both for humans and animals. The research and review articles published in this first book of the Collection “Stem Cells in Domestic Animals: Applications in Health and Production” are excellent examples of the recent advances made in the field of stem/stromal cell research in veterinary medicine. In this field, sophisticated and new treatments are now required for improving patients’ quality of life; in livestock animals, the goal of regenerative medicine is to improve not only animal welfare but also the quality of production, aiming to preserve human health. The contributions collected in this book concern both laboratory research and clinical applications of mesenchymal stem/stromal cells. The increasing knowledge of cell-based therapies may constitute an opportunity for researchers, veterinary practitioners, and animal owners to contribute to animal and human health and well-being
Biofidelic simulations of embryonic joint growth and morphogenesis
During skeletal development, the opposing surfaces in the joint mould into interlocking and reciprocal shapes in a process called morphogenesis. Morphogenesis is critical to the health and function of the joint, and yet, little is known about the process of joint morphogenesis. For example, how do different joints acquire their specific shapes? Which cellular processes underlie joint shaping and how are they regulated? However, it is known that fetal movements are critical to joint development, with alterations or absences of movement being implicated in multiple pre- and post-natal musculoskeletal conditions. This doctorate explored the cell-level dynamics governing joint growth and the implication of movements in regulating them, using novel biofidelic and mechanobiological models of joint growth.
Cell-level data from wild type zebrafish larvae were tracked and synthesised in a biofidelic simulation of zebrafish jaw joint growth. Growth characteristics were quantified revealing a strong anisotropy (Chapter 3). Next, zebrafish larvae were immobilised using drug treatment. The material properties of the zebrafish jaw cartilage were measured using nano-indentation in the presence or absence of movement showing a delay in cartilage stiffening in immobilised larvae (Chapter 4). Then, I developed a novel mechanobiological model of zebrafish jaw joint growth, which identified a correlation between growth characteristics and the dynamic patterns of mechanical stimuli experienced by joint elements over jaw motion (Chapter 5). Finally, local growth rates were characterised in the mouse elbow in the presence or absence of skeletal muscles. Spatial heterogeneity in the growth rates correlated with the emergence of specific shape features at the level of the condyles. Immobilisation led to disruption of the local growth rates correlated with failed shape differentiation of the condyles. The relative contribution of key cell activities to growth such as cell volume expansion, cell number increases and extracellular matrix expansion, were shown to vary over time in both wild types and muscleless-limbs and to be altered in the absence of skeletal muscles (Chapter 6).
This research offers avenues for improvement in simulations of joint development and potentially other organs. It provides fundamental advance in our understanding of mechanoregulation in the developing joint and increases our understanding of the origins of musculoskeletal abnormalities.Open Acces
Biomaterials for Bone Tissue Engineering 2020
This book presents recent advances in the field of bone tissue engineering, including molecular insights, innovative biomaterials with regenerative properties (e.g., osteoinduction and osteoconduction), and physical stimuli to enhance bone regeneration
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Analysis of bendable osteochondral allograft treatment and investigations of articular cartilage wear mechanics
Osteoarthritis is a highly prevalent, debilitating disease characterized by the wear and degradation of articular cartilage. While many surgical interventions exist, few are consistently effective and those that are effective are not necessarily suitable for all patients. The objective of this dissertation is to improve patient care through the development of a new surgical technique and through basic science studies which seek to better understand articular cartilage wear initiation. Four studies, which address this objective are summarized below.
Osteochondral allograft transplantation provides a safe and effective treatment option for large cartilage defects, but its use is limited partly due to the difficulty of matching articular surface curvature between donor and recipient. We hypothesize that bendable osteochondral allografts may provide better curvature matching for patella transplants in the patellofemoral joint. The finite element study presented in Chapter 2 investigates patellofemoral joint congruence for unbent and bendable osteochondral allografts, at various flexion angles. Finite element models were created for 12 femur-patella osteochondral allograft pairings. Two grooves were cut into the bony substrate of each allograft, allowing the articular layer to bend. Patellofemoral joints with either unbent (OCA) or permanently bent (BOCA) allografts were articulated from 40 to 70 degrees flexion and contact area was calculated. OCAs and BOCAs were then shifted 6 mm distally toward the tibia (S-OCA, S-BOCA) to investigate the influence of proximal-distal alignment on congruence. On average, no significant difference in contact area was found between native patellofemoral joints and either OCAs or BOCAs (p > 0.25), indicating that both types of allografts restored native congruence. This result provides biomechanical support in favor of an emerging surgical procedure. S-BOCAs resulted in a significant increase in contact area relative to the remaining groups (p < 0.02). The fact that bendable osteochondral allografts produced equally good results implies that these bendable allografts may prove useful in future surgical procedures, with the possibility of transplanting them with a small distal shift. Surgeons who are reluctant to use osteochondral allografts for resurfacing patellae based on curvature matching capabilities may be more amenable to adopting bendable osteochondral allografts.
The recent development of bendable osteochondral allografts provides the potential for improved osteoarthritis treatment for joints whose current treatment is unsatisfactory. One such joint is the carpometacarpal joint in the thumb. While the current standard of care for carpometacarpal osteoarthritis, ligament reconstruction and tendon interposition, can reduce pain in the joint, it does not restore full joint function and mobility. A proposed alternative includes using an osteochondral allograft harvested from the femoral trochlea in a donor knee, machining grooves in the bone to allow the allograft to bend, and replacing the trapezium with this bent osteochondral allograft [1,2]. Chapter 3 of this dissertation discusses adjustments to the original design of the bendable allograft and the design of a custom surgical tool to perform the proposed surgery. Specification changes of the allograft included an overall size reduction in order to better fit within the carpometacarpal joint, minimum bone thickness requirements to avoid bone cracking during the surgical procedure, and a reduction from three grooves to two grooves, which provided sufficient bending yet avoided fracture of the allograft. The surgical tool was designed to be a custom forceps device, whose primary features included (1) jaws with an angled face to match the angle of allograft bending and (2) insertion holes for the Kirschner wire and compression screws used to anchor the allograft in the bent position. These customizations allow the tool to be used to bend the allograft, fix it in the bent configuration, and place the allograft in its proper position in the hand during anchoring of the bent allograft to the native trapezium.
The final two studies presented in this dissertation focus on furthering our current understanding of wear and structure-function relationships of articular cartilage. We hypothesize that cartilage wears due to fatigue failure in reciprocating compression instead of reciprocating friction. Chapter 4 compares reciprocating sliding of immature bovine articular cartilage against glass in two testing configurations: (1) a stationary contact area configuration (SCA), which results in static compression, interstitial fluid depressurization and increasing friction coefficient during reciprocating sliding, and (2) a migrating contact area configuration (MCA), which maintains fluid pressurization and low friction while producing reciprocating compressive loading during reciprocating sliding. Contact stress, sliding duration, and sliding distance were controlled to be similar between test groups. SCA tests exhibited an average friction coefficient of μ=0.084±0.032, while MCA tests exhibited a lower average friction coefficient of μ=0.020±0.008 (p<10^(-4)).
Despite the lower friction, MCA cartilage samples exhibited clear surface damage with a significantly greater average surface deviation from a fitted plane after wear testing (R_q=0.125±0.095 mm) than cartilage samples slid in a SCA configuration (R_q=0.044±0.017 mm, p=0.002), which showed minimal signs of wear. Polarized light microscopy confirmed that delamination damage occurred between the superficial and middle zones of the articular cartilage in MCA samples. The greatest wear was observed in the group with lowest friction coefficient, subjected to cyclical instead of static compression, implying that friction is not the primary driver of cartilage wear. Delamination between superficial and middle zones imply the main mode of wear is fatigue failure under cyclical compression, not fatigue or abrasion due to reciprocating frictional sliding.
The final study of this dissertation, presented in Chapter 5, investigates the importance of collagen fibril distribution in articular cartilage computational models. Finite element models were created to approximate a bovine humeral head and replicate previous experimental loading conditions [3]. Five different finite element analyses were run, each using a different fibril distribution model. Three of the models used two, four, or eight discrete fibril bundles, while two models used continuous fibril distributions with either isotropic or depth-dependent ellipsoidal distributions.
Two primary findings arose from this investigation. The first was the discovery that as the fibril distribution became more isotropic, the strain throughout the tissue decreased, even though the contact area between the articular surface and rigid platen remained relatively equal across distribution models. This suggests that computational models which approximate the collagen fibrils with an isotropic distribution may be underestimating the strain through the depth of the tissue. The second primary finding was that in the discrete distribution model with two fibril bundles, which followed the classically described Benninghoff structure [4], the greatest magnitude of shear strain during compressive loading was observed in the middle zone. However, the highest magnitude of shear strain observed in the isotropic fibril distribution model occurred in the deep zone near the subchondral surface. The observed results suggest that the type of fibril distribution used to model collagen in articular cartilage plays a role in depth-dependent strain magnitude and strain distribution
International consensus statement on allergy and rhinology: Allergic rhinitis – 2023
Background
In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document. Methods
ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work. Results
ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost. Conclusion
The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment
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