Effect of Physicochemical Surface Properties of Silicon-Substitute hydroxyapatite on Angiogenesis.

Synthetic hydroxyapatite (HA) is a widely studied bioceramic for bone tissue engineering (BTE) due to its similarity to the mineral component of bone. As bone mineral contains various ionic substitutions that play a crucial role in bone metabolism, the bioactivity of HA can be improved by adding small amounts of physiologically relevant ions into its crystal structure, with silicate-substituted HA (Si-HA) showing particularly promising results. Nevertheless, it remains unclear how distinct material characteristics influence the bioactivity due to the intertwined nature of surface properties. A co-culture methodology was optimised and applied for in vitro quantification of the biological response. Initially, HA and Si-HA samples were produced and characterised. To compare the bioactivity of the samples, a method was developed to measure interactions in an increasingly complex environment, first including fibronectin (FN) adsorption and subsequently cell adhesion in mono- and co-culture using primary human osteoblasts (hOBs) and human dermal microvascular endothelial cells (HDMECs), with- and without FN pre-coating. An experimental set-up was designed to assess to what extent different surface features of the samples contribute to the induced biological response. An 8 nm gold-sputter coating was applied to eradicate the electrochemical differences and polishing and abrading was used to reduce the differences in surface topographies. Overall, 1.25wt%Si-HA exhibited most nano-scale variations in surface potential. In terms of bioactivity, 1.25wt%Si-HA samples induced the highest osteoblast attachment and vessel formation. Additionally, in vitro vessel formation was established on Si-HA surfaces using a hOB;HDMEC cell ratio of 70:30 and a methodology was established that enabled the assessment of the relative effect of topographical and electrochemical features induced by silicon substitution in the HA lattice on their bioactivity. It was found that the difference in the amount of protein attached to HA and 1.25wt%Si-HA after 2 hours was affected by topographical differences. Conversely, electrochemical differences induced different vessel-like structure formation in co-culture with a FN pre-coating. Without a FN pre-coating, both topographical and electrochemical differences dictated the differences in angiogenic response. Overall, 1.25wt%Si-HA surface features appear to induce the most favourable protein adsorption and cell adhesion in mono- and co-culture with- and without FN pre-coating.

The diazirine-mediated photo-crosslinking of collagen improves biomaterial mechanical properties and cellular interactions.

In tissue engineering, crosslinking with carbodiimides such as EDC is omnipresent to improve the mechanical properties of biomaterials. However, in collagen biomaterials, EDC reacts with glutamate or aspartate residues, inactivating the binding sites for cellular receptors and rendering collagen inert to many cell types. In this work, we have developed a crosslinking method that ameliorates the rigidity, stability, and degradation rate of collagen biomaterials, whilst retaining key interactions between cells and the native collagen sequence. Our approach relies on the UV-triggered reaction of diazirine groups grafted on lysines, leaving critical amino acid residues intact. Notably, GxxGER recognition motifs for collagen-binding integrins, ablated by EDC crosslinking, were left unreacted, enabling cell attachment, spreading, and colonization on films and porous scaffolds. In addition, our procedure conserves the architecture of biomaterials, improves their resistance to collagenase and cellular contraction, and yields material stiffness akin to that obtained with EDC. Importantly, diazirine-crosslinked collagen can host mesenchymal stem cells, highlighting its strong potential as a substrate for tissue repair. We have therefore established a new crosslinking strategy to modulate the mechanical features of collagen porous scaffolds without altering its biological properties, thereby offering an advantageous alternative to carbodiimide treatment. STATEMENT OF SIGNIFICANCE: This article describes an approach to improve the mechanical properties of collagen porous scaffolds, without impacting collagen's natural interactions with cells. This is significant because collagen crosslinking is overwhelmingly performed using carbodiimides, which results in a critical loss of cellular affinity. By contrast, our method leaves key cellular binding sites in the collagen sequence intact, enabling cell-biomaterial interactions. It relies on the fast, UV-triggered reaction of diazirine with collagen, and does not produce toxic by-products. It also supports the culture of mesenchymal stem cells, a pivotal cell type in a wide range of tissue repair applications. Overall, our approach offers an attractive option for the crosslinking of collagen, a prominent material in the growing field of tissue engineering.

Controlling the Architecture of Freeze-Dried Collagen Scaffolds with Ultrasound-Induced Nucleation.

Collagen is a naturally occurring polymer that can be freeze-dried to create 3D porous scaffold architectures for potential application in tissue engineering. The process comprises the freezing of water in an aqueous slurry followed by sublimation of the ice via a pre-determined temperature-pressure regime and these parameters determine the arrangement, shape and size of the ice crystals. However, ice nucleation is a stochastic process, and this has significant and inherent limitations on the ability to control scaffold structures both within and between the fabrication batches. In this paper, we demonstrate that it is possible to overcome the disadvantages of the stochastic process via the use of low-frequency ultrasound (40 kHz) to trigger nucleation, on-demand, in type I insoluble bovine collagen slurries. The application of ultrasound was found to define the nucleation temperature of collagen slurries, precisely tailoring the pore architecture and providing important new structural and mechanistic insights. The parameter space includes reduction in average pore size and narrowing of pore size distributions while maintaining the percolation diameter. A set of core principles are identified that highlight the huge potential of ultrasound to finely tune the scaffold architecture and revolutionise the reproducibility of the scaffold fabrication protocol.

Extracellular macrostructure anisotropy improves cardiac tissue-like construct function and phenotypic cellular maturation.

Regenerative cardiac tissue is a promising field of study with translational potential as a therapeutic option for myocardial repair after injury, however, poor electrical and contractile function has limited translational utility. Emerging research suggests scaffolds that recapitulate the structure of the native myocardium improve physiological function. Engineered cardiac constructs with anisotropic extracellular architecture demonstrate improved tissue contractility, signaling synchronicity, and cellular organization when compared to constructs with reduced architectural order. The complexity of scaffold fabrication, however, limits isolated variation of individual structural and mechanical characteristics. Thus, the isolated impact of scaffold macroarchitecture on tissue function is poorly understood. Here, we produce isotropic and aligned collagen scaffolds seeded with embryonic stem cell derived cardiomyocytes (hESC-CM) while conserving all confounding physio-mechanical features to independently assess the effects of macroarchitecture on tissue function. We quantified spatiotemporal tissue function through calcium signaling and contractile strain. We further examined intercellular organization and intracellular development. Aligned tissue constructs facilitated improved signaling synchronicity and directional contractility as well as dictated uniform cellular alignment. Cells on aligned constructs also displayed phenotypic and genetic markers of increased maturity. Our results isolate the influence of scaffold macrostructure on tissue function and inform the design of optimized cardiac tissue for regenerative and model medical systems.

Mimicking Transmural Helical Cardiomyofibre Orientation Using Bouligand-like Pore Structures in Ice-Templated Collagen Scaffolds.

The helical arrangement of cardiac muscle fibres underpins the contractile properties of the heart chamber. Across the heart wall, the helical angle of the aligned fibres changes gradually across the range of 90-180°. It is essential to recreate this structural hierarchy in vitro for developing functional artificial tissue. Ice templating can achieve single-oriented pore alignment via unidirectional ice solidification with a flat base mould design. We hypothesise that the orientation of aligned pores can be controlled simply via base topography, and we propose a scalable base design to recapitulate the transmural fibre orientation. We have utilised finite element simulations for rapid testing of base designs, followed by experimental confirmation of the Bouligand-like orientation. X-ray microtomography of experimental samples showed a gradual shift of 106 ± 10°, with the flexibility to tailor pore size and spatial helical angle distribution for personalised medicine.

In vitro angiogenesis in response to biomaterial properties for bone tissue engineering: a review of the state of the art.

Bone tissue engineering (BTE) aims to improve the healing of bone fractures using scaffolds that mimic the native extracellular matrix. For successful bone regeneration, scaffolds should promote simultaneous bone tissue formation and blood vessel growth for nutrient and waste exchange. However, a significant challenge in regenerative medicine remains the development of grafts that can be vascularized successfully. Amongst other things, optimization of physicochemical conditions of scaffolds is key to achieving appropriate angiogenesis in the period immediately following implantation. Calcium phosphates and collagen scaffolds are two of the most widely studied biomaterials for BTE, due to their close resemblance to inorganic and organic components of bone, respectively, and their bioactivity, tunable biodegradability and the ability to produce tailored architectures. While various strategies exist to enhance vascularization of these scaffolds in vivo, further in vitro assessment is crucial to understand the relation between physicochemical properties of a biomaterial and its ability to induce angiogenesis. While mono-culture studies can provide evidence regarding cell-material interaction of a single cell type, a co-culture procedure is crucial for assessing the complex mechanisms involved in angiogenesis. A co-culture more closely resembles the natural tissue both physically and biologically by stimulating natural intercellular interactions and mimicking the organization of the in vivo environment. Nevertheless, a co-culture is a complex system requiring optimization of various parameters including cell types, cell ratio, culture medium and seeding logistics. Gaining fundamental knowledge of the mechanism behind the bioactivity of biomaterials and understanding the contribution of surface and architectural features to the vascularization of scaffolds, and the biological response in general, can provide an invaluable basis for future optimization studies. This review gives an overview of the available literature on scaffolds for BTE, and trends are extracted on the relationship between architectural features, biochemical properties, co-culture parameters and angiogenesis.

Adjusting the physico-chemical properties of collagen scaffolds to accommodate primary osteoblasts and endothelial cells.

Collagen-based biomaterials are used widely as tissue engineering scaffolds because of their excellent bioactivity and their similarity to the natural ECM. The regeneration of healthy bone tissue requires simultaneous support for both osteoblasts and, where angiogenesis is intended, endothelial cells. Hence it is important to tailor carefully the biochemical and structural characteristics of the scaffold to suit the needs of each cell type. This work describes for the first time a systematic study to gain insight into the cell type-specific response of primary human osteoblast (hOBs) and human dermal microvascular endothelial cells (HDMECs) to insoluble collagen-based biomaterials. The behaviour was evaluated on both 2D films and 3D scaffolds, produced using freeze-drying. The collagen was cross-linked at various EDC/NHS concentrations and mono-cultured with hOBs and HDMECs to assess the effect of architectural features and scaffold stabilization on cell behaviour. It was observed that 3D scaffolds cross-linked at 30% of the standard conditions in literature offered an optimal combination of mechanical stiffness and cellular response for both cell types, although endothelial cells were more sensitive to the degree of cross-linking than hOBs. Architectural features have a time-dependent impact on the cell migration profile, with alignment being the most influential parameter overall.

Modulating Drug Release from Short Poly(ethylene glycol) Block Initiated Poly(L-lactide) Di-block Copolymers.

This paper investigates drug release from a novel series of mPEG-functionalised PLLA polymers whose individual components (PEG and PLLA) have regulatory FDA approval. Two processing methods were explored to understand their effect on the morphology and drug release profiles of the polymers, with and without mPEG functionalisation. In the first method the polymer and Propranolol.HCl drug powders were mixed together before injection moulding. In the second method, supercritical CO2 was used to mix the polymer and drug before injection moulding. When non-functionalised PLLA was processed through injection moulding alone, there were no signs of polymer-drug interaction, and the drug was confined to crystals on the surface. This resulted in up to 85 wt% burst release of propranolol.HCl after one day of incubation. By contrast, injection moulding of mPEG-functionalised polymers resulted in the partial dissolution of drug in the polymer matrix and a smaller burst (50 wt% drug) followed by sustained release. This initial burst release was completely eliminated from the profile of mPEG-functionalised polymers processed via supercritical CO2. The addition of mPEG facilitated the distribution of the drug into the bulk matrix of the polymer. Paired with supercritical CO2 processing, the drug release profile showed a slow, sustained release throughout the 4 months of the study.

Exploring community enabling factors associated with recent HIV testing in a regional sample of gay, bisexual, and other men who have sex with men.

HIV testing and diagnosis are the gateway into treatment and eventual viral suppression. With gay, bisexual, and other men who have sex with men (GBMSM) persistently over-representing new HIV diagnoses in Canada, combined with the evolving nature of community social connection, an exploration of factors associated with recent HIV testing is warranted. As most studies of GBMSM rely on samples obtained from larger metropolitan regions, examining HIV testing from an under-researched region is necessary. With data collected from an online survey of LGBTQ+ persons 16 or older living, working, or residing in the Region of Waterloo, Ontario, Canada, we used multinomial logistic regression to explore socio-demographic, behavioural, and psychosocial factors associated with recent HIV testing for GBMSM. In the final multivariate multinomial logistic regression model: sense of belonging was associated with more recently testing, as was having an increasing proportion of LGBT friends, app use to find sex partners in the past 12 months, access to the local AIDS service organization, and general sense of belonging to local community, among other. This analysis highlights the continued importance of enabling and need factors when accessing testing, and suggests areas for further testing promotion in physical and virtual spaces frequented by GBMSM.

Complex architectural control of ice-templated collagen scaffolds using a predictive model.

The architectural and physiomechanical properties of regenerative scaffolds have been shown to improve engineered tissue function at both a cellular and tissue level. The fabrication of regenerative three-dimensional scaffolds that precisely replicate the complex hierarchical structure of native tissue, however, remains a challenge. The aim of this work is therefore two-fold: i) demonstrate an innovative multidirectional freeze-casting system to afford precise architectural control of ice-templated collagen scaffolds; and ii) present a predictive simulation as an experimental design tool for bespoke scaffold architecture. We used embedded heat sources within the freeze-casting mold to manipulate the local thermal environment during solidification of ice-templated collagen scaffolds. The resultant scaffolds comprised complex and spatially varied lamellar orientations that correlated with the imposed thermal environment and could be readily controlled by varying the geometry and power of the heat sources. The complex macro-architecture did not interrupt the hierarchical features characteristic of ice-templated scaffolds, but pore orientation had a significant impact on the stiffness of resultant structures under compression. Furthermore, our finite element model (FEM) accurately predicted the thermal environment and illustrated the freezing front topography within the mold during solidification. The lamellar orientation of freeze-cast scaffolds was also predicted using thermal gradient vector direction immediately prior to phase change. In combination our FEM and bespoke freeze-casting system present an exciting opportunity for tailored architectural design of ice-templated regenerative scaffolds that mimic the complex hierarchical environment of the native extracellular matrix. STATEMENT OF SIGNIFICANCE: Biomimetic scaffold structure improves engineered tissue function, but the fabrication of three-dimensional scaffolds that precisely replicate the complex hierarchical structure of native tissue remains a challenge. Here, we leverage the robust relationship between thermal gradients and lamellar orientation of ice-templated collagen scaffolds to develop a multidirectional freeze-casting system with precise control of the thermal environment and consequently the complex lamellar structure of resultant scaffolds. Demonstrating the diversity of our approach, we identify heat source geometry and power as control parameters for complex lamellar orientations. We simultaneously present a finite element model (FEM) that describes the three-dimensional thermal environment during solidification and accurately predicts lamellar structure of resultant scaffolds. The model serves as a design tool for bespoke regenerative scaffolds.

'Getting shut down and shut out': Exploring ACB patient perceptions on healthcare access at the physician-patient level in Canada.

PURPOSE: The experiences of African, Caribbean and Black (ACB) Canadians are seldom explored in the Canadian context. Family physicians act as a gateway to the rest of the healthcare system and are necessary to provide proper patient care. However, Canada's history with colonialism may impact the socio-cultural context in which patients receive care. METHOD: 41 participants from Waterloo Region, Ontario, were engaged in eight focus groups to discuss their experiences in the healthcare system. Data were analysed following thematic analysis. RESULTS: Style of care, racism and discrimination and a lack of cultural competence hindered access. oor Inadequate cultural competence was attributed to western and biomedical approaches, poor understanding of patients' context, physicians failing to address specific health concerns, and racism and discrimination. Participants highlighted that the two facilitators to care were having an ACB family physician and fostering positive relationships with physicians. CONCLUSION: Participants predominantly expressed dissatisfaction in physicians' approaches to care, which were compounded by experiences of racism and discrimination. Findings demonstrate how ACB patients are marginalized and excluded from the healthcare syste Iimplications for better access to care included utilizing community healthcare centres, increasing physicians' capacity around culturally inclusive care, and increasing access to ACB physicians.

Experiences of trans patients in primary care settings: findings from The OutLook Study.

BACKGROUND: Relationships between primary care providers (PCP) and trans patients remain important, necessitating discussions about gender identity, health and their intersections. METHODS: Using an online survey, we explored socio-demographic and psycho-social factors associated with: (1) disclosing gender identity; (2) discussing gender identity-related health issues; and (3) comfort sharing gender identity with PCPs, among trans people (n =112) over 16years of age, sampled in Waterloo, Ontario, Canada. Bivariate and multivariate methods using modified Poisson regression generated effect estimates. RESULTS: Age, birth presumed gender, employment status, family support, and transphobia were significantly associated with disclosing gender identity, discussing gender identity-related health issues, and comfortability sharing gender identity with PCPs. CONCLUSION: Increasing PCPs' knowledge of trans-related health issues is stressed to improve access and quality for trans patients.

Experiences of discrimination and its impacts on well-being among racialised LGBTQ+ newcomers living in Waterloo region, Ontario, Canada.

Discrimination (i.e. racism, homo/bi/transphobia) at both the individual and systemic levels may negatively impact the well-being of racialised LGBTQ+ newcomers living in Waterloo Region, Ontario, Canada. Current research about the experiences of LGBTQ+ newcomers focuses predominantly on homogeneous samples of gay men living in large metropolitan city centres. The present study aims to extend the current literature by exploring the experiences of discrimination and its impacts on well-being among racialised LGBTQ+ newcomers living in a small urban area and representing a variety of intersecting identities (i.e. ethno-racial background, LGBTQ+ identity, newcomer status). Using a qualitative method, 10 individuals were invited to complete a semistructured interview between fall 2019 and summer 2020 about their experiences of discrimination in Waterloo Region, and how such experiences impact their well-being. Using an intersectional lens, a thematic analysis revealed that racialised LGBTQ+ newcomers experienced discrimination before and after settlement in Waterloo Region. Prior to settlement, participants spoke predominantly about experiences of homo/biphobia and the associated feelings of internalised oppression. Alternatively, upon settling in Waterloo Region, experiences of discrimination were predominantly racism, and, in particular, systemic racism, which manifested as an inability to access adequate services and a lack of representation in various spaces throughout Waterloo Region. These results extend previous research by identifying the service barriers experienced by racialised LGBTQ+ newcomers living in a small urban area and can be used to inform best practices for addressing these barriers in Waterloo Region and other small urban areas with similar demographics. Implications and limitations are discussed.

Avoiding artefacts in MicroCT imaging of collagen scaffolds: Effect of phosphotungstic acid (PTA)-staining and crosslink density.

X-ray micro-computed tomography (µ-CT) can be used to provide both qualitative and quantitative information on the structure of three-dimensional (3D) bioactive scaffolds. When performed in a dry state, µ-CT accurately reflects the structure of collagen-based scaffolds, but imaging in a wet state offers challenges with radiolucency. Here we have used phosphotungstic acid (PTA) as a contrast agent to visualise fully hydrated collagen scaffolds in a physiologically relevant environment. A systematic investigation was performed to understand the effects of PTA on the results of µ-CT imaging by varying sample processing variables such as crosslinking density, hydration medium and staining duration. Immersing samples in 0.3% PTA solution overnight completely stained the samples and the treatment provided a successful route for µ-CT analysis of crosslinked samples. However, significant structural artefacts were observed for samples which were either non-crosslinked or had low levels of crosslinking, which had a heterogeneous interior architecture with collapsed pores at the scaffold periphery. This work highlights the importance of optimising the choice of processing and staining conditions to ensure accurate visualisation for hydrated 3D collagen scaffolds in an aqueous medium.

Tailoring the biofunctionality of collagen biomaterials via tropoelastin incorporation and EDC-crosslinking.

Recreating the cell niche of virtually all tissues requires composite materials fabricated from multiple extracellular matrix (ECM) macromolecules. Due to their wide tissue distribution, physical attributes and purity, collagen, and more recently, tropoelastin, represent two appealing ECM components for biomaterials development. Here we blend tropoelastin and collagen, harnessing the cell-modulatory properties of each biomolecule. Tropoelastin was stably co-blended into collagen biomaterials and was retained after EDC-crosslinking. We found that human dermal fibroblasts (HDF), rat glial cells (Rugli) and HT1080 fibrosarcoma cells ligate to tropoelastin via EDTA-sensitive and EDTA-insensitive receptors or do not ligate with tropoelastin, respectively. These differing elastin-binding properties allowed us to probe the cellular response to the tropoelastin-collagen composites assigning specific bioactivity to the collagen and tropoelastin component of the composite material. Tropoelastin addition to collagen increased total Rugli cell adhesion, spreading and proliferation. This persisted with EDC-crosslinking of the tropoelastin-collagen composite. Tropoelastin addition did not affect total HDF and HT1080 cell adhesion; however, it increased the contribution of cation-independent adhesion, without affecting the cell morphology or, for HT1080 cells, proliferation. Instead, EDC-crosslinking dictated the HDF and HT1080 cellular response. These data show that a tropoelastin component dominates the response of cells that possess non-integrin based tropoelastin receptors. EDC modification of the collagen component directs cell function when non-integrin tropoelastin receptors are not crucial for cell activity. Using this approach, we have assigned the biological contribution of each component of tropoelastin-collagen composites, allowing informed biomaterial design for directed cell function via more physiologically relevant mechanisms. STATEMENT OF SIGNIFICANCE: Biomaterials fabricated from multiple extracellular matrix (ECM) macromolecules are required to fully recreate the native tissue niche where each ECM macromolecule engages with a specific repertoire of cell-surface receptors. Here we investigate combining tropoelastin with collagen as they interact with cells via different receptors. We identified specific cell lines, which associate with tropoelastin via distinct classes of cell-surface receptor. These showed that tropoelastin, when combined with collagen, altered the cell behaviour in a receptor-usage dependent manner. Integrin-mediated tropoelastin interactions influenced cell proliferation and non-integrin receptors influenced cell spreading and proliferation. These data shed light on the interplay between biomaterial macromolecular composition, cell surface receptors and cell behaviour, advancing bespoke materials design and providing functionality to specific cell populations.

A technique for improving dispersion within polymer-glass composites using polymer precipitation.

Particulate reinforcement of polymeric matrices is a powerful technique for tailoring the mechanical and degradation properties of bioresorbable implant materials. Dispersion of inorganic particles is critical to achieving optimal properties, however established techniques such as twin-screw extrusion or solvent casting can have significant drawbacks including excessive thermal degradation or particle agglomeration. We present a facile method for production of polymer-inorganic composites that reduces the time at elevated temperature and the time available for particle agglomeration. Glass slurry was added to a dissolved PLLA solution, and ethanol was added to precipitate polymer onto the glass particles. Characterisation of parts formed by subsequent micro-injection moulding of composite precipitate revealed a significant reduction in agglomeration, with d0.9 reduced from 170 to 43 µm. This drastically improved the ductility (ɛB) from 7% to 120%, without loss of strength or stiffness. The method is versatile and applicable to a wide range of polymer and filler materials.

The effects of despeckling filters on pore size measurements in collagen scaffold micro-CT data.

Micro-CT is often used to assess the characteristics of porous structures such as tissue engineering scaffolds and trabecular bone. Prior to analysis, micro-CT images can be thresholded and filtered to remove noise. Scaffold pore size affects mechanical properties and biological cell behaviour and is a frequently assessed parameter. This paper identifies and characterizes an artefact affecting a commonly used filter which erroneously increases mean pore size. The 3D sweep despeckling filter removes all but the largest object within a volume of interest, and therefore deletes any disconnected objects located at the periphery, increasing measured mean pore size. This artefact is characterized, and effective methods to mitigate its effects are devised, involving despeckling a sufficiently large volume of interest, then reducing the volume of interest in size to remove the error prior to analysis. Techniques to effectively apply this method to other data sets are described. This method eliminates the artefact but is time-consuming and computationally expensive. Alternative, more economical filters which remove objects below a specified size are also assessed but are shown to be affected by the same artefact. These results will help to guide the implementation of future studies investigating the effects of pore size.

Micro-CT is an imaging technique commonly used to assess the characteristics of porous structures, such as medical tissue engineering scaffolds and bone. Prior to analysis micro-CT images are often processed by thresholding and filtering to improve the image quality. Scaffold pore size affects biological cell behaviour and mechanical properties, and is a frequently assessed parameter when evaluating medical scaffolds. This paper identifies and characterises an artefact affecting a commonly used filter which erroneously increases measured peripheral mean pore size. The artefact affects the periphery of volumes of interest which have been filtered by a technique called 3D sweep despeckling. This filter removes all but the largest object in the volume of interest, and therefore also deletes small disconnected objects located at the volume of interest periphery. This paper characterises the artefact, and effective methods to mitigate its effects are devised, involving despeckling a sufficiently large volume of interest, then reducing the volume of interest in size to remove the error prior to analysis. Techniques to ascertain the parameters required to effectively apply this artefact reduction method to other datasets are described. This method eliminates the artefact, but is time consuming and computationally expensive. Alternative, more economical despeckling filters are assessed for their ability to remove the error. Of these, a filter which deletes objects below a prescribed area was found to be most effective when performing 2D pore analysis on scaffolds, and the same filter applied to objects below a set volume was best when 3D pore analysis was used. This filter was found to be afflicted by the same artefact as sweep despeckling. These results will help guide the implementation of future studies investigating the effects of pore size.

Collagen Film Activation with Nanoscale IKVAV-Capped Dendrimers for Selective Neural Cell Response.

Biocompatible neural guidance conduits are alternatives to less abundant autologous tissue grafts for small nerve gap injuries. To address larger peripheral nerve injuries, it is necessary to design cell selective biomaterials that attract neuronal and/or glial cells to an injury site while preventing the intrusion of fibroblasts that cause inhibitory scarring. Here, we investigate a potential method for obtaining this selective cellular response by analysing the responses of rat Schwann cells and human dermal fibroblasts to isoleucine-lysine-valine-alanine-valine (IKVAV)-capped dendrimer-activated collagen films. A high quantity of nanoscale IKVAV-capped dendrimers incorporated onto pre-crosslinked collagen films promoted rat Schwann cell attachment and proliferation, and inhibited human dermal fibroblast proliferation. In addition, while pre-crosslinked dendrimer-activated films inhibited fibroblast proliferation, non-crosslinked dendrimer-activated films and films that were crosslinked after dendrimer-activation (post-crosslinked films) did not. The different cellular responses to pre-crosslinked and post-crosslinked films highlight the importance of having fully exposed, non-covalently bound biochemical motifs (pre-crosslinked films) directing certain cellular responses. These results also suggest that high concentrations of nanoscale IKVAV motifs can inhibit fibroblast attachment to biological substrates, such as collagen, which inherently attract fibroblasts. Therefore, this work points toward the potential of IKVAV-capped dendrimer-activated collagen biomaterials in limiting neuropathy caused by fibrotic scarring at peripheral nerve injury sites.

Modulating hESC-derived cardiomyocyte and endothelial cell function with triple-helical peptides for heart tissue engineering.

In this study, we investigated the role of cardiomyocyte (CM) and endothelial cell (EC) specific interactions with collagen in the assembly of an operational myocardium in vitro. Engineered cardiac patches represent valuable tools for myocardial repair following infarction and are generally constituted of a suitable biomaterial populated by CMs and supportive cell types. Among those, ECs are required for tissue vascularization and positively modulate CM function. To direct the function of human embryonic stem cell (hESC)-derived CM and EC seeded on biomaterials, we replicated cell-collagen interactions, which regulate cellular behaviour in the native myocardium, using triple-helical peptides (THPs) that are ligands for collagen-binding proteins. THPs enhanced proliferation and activity of CMs and ECs separately and in co-culture, drove CM maturation and enabled coordinated cellular contraction on collagen films. These results highlight the importance of collagen interactions on cellular response and establish THP-functionalized biomaterials as novel tools to produce engineered cardiac tissues.

Experiences of Transgender Participants in Emergency Departments: Findings from the OutLook Study.

Purpose: Even in cases of medical emergency, mistreatment and negative experiences in life or in medical settings can deter trans patients from seeking necessary care. The purpose of this study was to identify factors associated with trans persons' emergency department (ED) avoidance in the mixed urban-rural Region of Waterloo, Ontario, Canada. Methods: The OutLook Study was a community-based partnership that created an online, cross-sectional questionnaire for lesbian, gay, bisexual, transgender, and other sexual and gender minority community members. Participants in this analysis were 16 years of age or older, lived, worked, or attended school in Waterloo Region, and identified as trans (n=112). Binary logistic regression was used to test associations between sociodemographic, resilience, and risk variables, and ED avoidance. Sociodemographic variables statistically significant at p<0.05 at the bivariate level were included as controls to explore different combinations of resilience and risk factor in multivariable models. Results: Participants reporting complete or partially complete medical transitions were more likely to report ED avoidance, compared to those who had not initiated medical transition. Elevated transphobia was associated with greater likelihood of avoidance. However, increasing levels of social support decreased the likelihood of avoidance. In multivariable models, social support, support from a special person, and transphobia were always significant, regardless of controlled variables. Conclusion: Transphobia-enacted in the contexts of everyday life and health care-can deter patients from seeking care. Patient-centered care requires careful attention to trans identity and health needs, especially in emergency settings. In the absence of structural changes, providers can take steps to mitigate the erasure and discrimination trans patients experience and anticipate when accessing EDs.