Telocytes: current methods of research, challenges and future perspectives.

Telocytes (TCs) are CD34-positive interstitial cells that have long cytoplasmic projections, called telopodes; they have been identified in several organs and in various species. These cells establish a complex communication network between different stromal and epithelial cell types, and there is growing evidence that they play a key role in physiology and pathology. In many tissues, TC network impairment has been implicated in the onset and progression of pathological conditions, which makes the study of TCs of great interest for the development of novel therapies. In this review, we summarise the main methods involved in the characterisation of these cells as well as their inherent difficulties and then discuss the functional assays that are used to uncover the role of TCs in normal and pathological conditions, from the most traditional to the most recent. Furthermore, we provide future perspectives in the study of TCs, especially regarding the establishment of more precise markers, commercial lineages and means for drug delivery and genetic editing that directly target TCs.

Laser texturing of additively manufactured implants: A tool to programme biological response.

The advent of additive manufacturing (AM) is rapidly shaping healthcare technologies pushing forward personalisation and enhanced implant functionalisation to improve clinical outcomes. AM techniques such as powder bed fusion (PBF) have been adopted despite the need to modify the as-built surface post manufacture. Medical device manufacturers have focused their efforts on refining various physical and chemical surface finishing approaches, however there is little consensus and some methods risk geometry alteration or contamination. This has led to a growing interest in laser texturing technologies to engineer the device surface. Herein, several bioinspired micro and nano textures were applied to laser PBF Ti-6Al-V4 substrates to alter physicochemical properties and in-turn we sought to understand what influences these alterations had on a human osteosarcoma cell line (MG63). Significant variations in roughness and time dependent contact angles were revealed between different patterns provide a tool to elicit desired biological responses. All surface treatments effectively enhanced early cell behaviour and in particular coverage was increased for the micro-textures. Influence of the patterns on cell differentiation was less consistent with alkaline phosphatase content increased only for the channel, grid and dual textures. While long term (21 days) mineralisation was found to be significantly enhanced in grids, dual, triangles and shark skin textures. Further regression analysis of all physicochemical and biological variables indicated that several properties should be used to strongly correlate cell behaviour, resulting in 82 % of the 21 day mineralisation dataset explained through a combination of roughness kurtosis and glycerol contact angle. Overall, this manuscript demonstrates the ability of laser texturing to offer tailored cell-surface interactions, which can be tuned to offer a tool to drive functional customisation of anatomically customised medical devices.

Development and experimental validation of a dynamic numerical model for human articular cartilage.

The purpose of this study was to create a preliminary set of experimentally validated Finite Element Analysis (FEA) models, in order to predict the dynamic mechanical behaviour of human articular cartilage (AC). Current models consider static loading with limited independent experimental validation, while the models for this study assess dynamic loading of AC, with direct comparison and validation to physical testing. Three different FEA models of AC were constructed, which considered both linear elastic and hyperelastic models; Neo-Hookean and Ogden. Models were validated using the data collected from compression testing of human femoral heads across 0-1.7 MPa (quasi-static tests and dynamic mechanical analysis). The linear elastic model was inadequate, with a 10-fold over prediction of the displacement dynamic amplitude. The Neo-Hookean model accurately predicted the dynamic amplitude but failed to predict the initial compression of the cartilage, with a 10 times overprediction. The Ogden model provided the best results, with both the initial compression lying within one standard deviation of that observed in the validation data set, and the dynamic amplitude of the same order of magnitude. In conclusion, this study has found that the fast dynamic response of human AC is best represented by a third order Ogden model.

Epigenetic Reprogramming via Synergistic Hypomethylation and Hypoxia Enhances the Therapeutic Efficacy of Mesenchymal Stem Cell Extracellular Vesicles for Bone Repair.

Mesenchymal stem cells (MSCs) are a promising cell population for regenerative medicine applications, where paracrine signalling through the extracellular vesicles (EVs) regulates bone tissue homeostasis and development. MSCs are known to reside in low oxygen tension, which promotes osteogenic differentiation via hypoxia-inducible factor-1α activation. Epigenetic reprogramming has emerged as a promising bioengineering strategy to enhance MSC differentiation. Particularly, the process of hypomethylation may enhance osteogenesis through gene activation. Therefore, this study aimed to investigate the synergistic effects of inducing hypomethylation and hypoxia on improving the therapeutic efficacy of EVs derived from human bone marrow MSCs (hBMSCs). The effects of the hypoxia mimetic agent deferoxamine (DFO) and the DNA methyltransferase inhibitor 5-azacytidine (AZT) on hBMSC viability was assessed by quantifying the DNA content. The epigenetic functionality was evaluated by assessing histone acetylation and histone methylation. hBMSC mineralisation was determined by quantifying alkaline phosphate activity, collagen production and calcium deposition. EVs were procured from AZT, DFO or AZT/DFO-treated hBMSCs over a two-week period, with EV size and concentration defined using transmission electron microscopy, nanoflow cytometry and dynamic light scattering. The effects of AZT-EVs, DFO-EVs or AZT/DFO-EVs on the epigenetic functionality and mineralisation of hBMSCs were evaluated. Moreover, the effects of hBMSC-EVs on human umbilical cord vein endothelial cells (HUVECs) angiogenesis was assessed by quantifying pro-angiogenic cytokine release. DFO and AZT caused a time-dose dependent reduction in hBMSC viability. Pre-treatment with AZT, DFO or AZT/DFO augmented the epigenetic functionality of the MSCs through increases in histone acetylation and hypomethylation. AZT, DFO and AZT/DFO pre-treatment significantly enhanced extracellular matrix collagen production and mineralisation in hBMSCs. EVs derived from AZT/DFO-preconditioned hBMSCs (AZT/DFO-EVs) enhanced the hBMSC proliferation, histone acetylation and hypomethylation when compared to EVs derived from AZT-treated, DFO-treated and untreated hBMSCs. Importantly, AZT/DFO-EVs significantly increased osteogenic differentiation and mineralisation of a secondary hBMSC population. Furthermore, AZT/DFO-EVs enhanced the pro-angiogenic cytokine release of HUVECs. Taken together, our findings demonstrate the considerable utility of synergistically inducing hypomethylation and hypoxia to improve the therapeutic efficacy of the MSC-EVs as a cell-free approach for bone regeneration.

Bioengineering extracellular vesicles: smart nanomaterials for bone regeneration.

In the past decade, extracellular vesicles (EVs) have emerged as key regulators of bone development, homeostasis and repair. EV-based therapies have the potential to circumnavigate key issues hindering the translation of cell-based therapies including functional tissue engraftment, uncontrolled differentiation and immunogenicity issues. Due to EVs' innate biocompatibility, low immunogenicity, and high physiochemical stability, these naturally-derived nanoparticles have garnered growing interest as potential acellular nanoscale therapeutics for a variety of diseases. Our increasing knowledge of the roles these cell-derived nanoparticles play, has made them an exciting focus in the development of novel pro-regenerative therapies for bone repair. Although these nano-sized vesicles have shown promise, their clinical translation is hindered due to several challenges in the EV supply chain, ultimately impacting therapeutic efficacy and yield. From the biochemical and biophysical stimulation of parental cells to the transition to scalable manufacture or maximising vesicles therapeutic response in vivo, a multitude of techniques have been employed to improve the clinical efficacy of EVs. This review explores state of the art bioengineering strategies to promote the therapeutic utility of vesicles beyond their native capacity, thus maximising the clinical potential of these pro-regenerative nanoscale therapeutics for bone repair.

Surface Free Energy Dominates the Biological Interactions of Postprocessed Additively Manufactured Ti-6Al-4V.

Additive manufacturing (AM) has emerged as a disruptive technique within healthcare because of its ability to provide personalized devices; however, printed metal parts still present surface and microstructural defects, which may compromise mechanical and biological interactions. This has made physical and/or chemical postprocessing techniques essential for metal AM devices, although limited fundamental knowledge is available on how alterations in physicochemical properties influence AM biological outcomes. For this purpose, herein, powder bed fusion Ti-6Al-4V samples were postprocessed with three industrially relevant techniques: polishing, passivation, and vibratory finishing. These surfaces were thoroughly characterized in terms of roughness, chemistry, wettability, surface free energy, and surface ζ-potential. A significant increase in Staphylococcus epidermidis colonization was observed on both polished and passivated samples, which was linked to high surface free energy donor γ- values in the acid-base, γAB component. Early osteoblast attachment and proliferation (24 h) were not influenced by these properties, although increased mineralization was observed for both these samples. In contrast, osteoblast differentiation on stainless steel was driven by a combination of roughness and chemistry. Collectively, this study highlights that surface free energy is a key driver between AM surfaces and cell interactions. In particular, while low acid-base components resulted in a desired reduction in S. epidermidis colonization, this was followed by reduced mineralization. Thus, while surface free energy can be used as a guide to AM device development, optimization of bacterial and mammalian cell interactions should be attained through a combination of different postprocessing techniques.

Stakeholder Perspectives on the Current and Future of Additive Manufacturing in Healthcare.

Additive manufacturing (AM) technologies have disrupted many supply chains by making new designs and functionalities possible. The opportunity to realize complex customized structures has led to significant interest within healthcare; however, full utilization critically requires the alignment of the whole supply chain. To offer insights into this process, a survey was conducted to understand the views of different medical AM stakeholders. The results highlighted an agreement between academics, designers, manufacturers, and medical experts, that personalization and design control are the main benefits of AM. Interestingly, surface finish was consistently identified as an obstacle. Nevertheless, there was a degree of acceptance that post-processing was necessary to achieve appropriate quality control. Recommendations were made for extending the use of in situ process monitoring systems to support improved reproducibility. Variations in the future vision of AM were highlighted between stakeholder groups and areas of interest for development noted for each stakeholder. Collectively, this survey indicates that medical stakeholders agree on the capabilities of AM but have different priorities for its implementation and progression. This highlights a degree of disconnection among the supply chain at a ground level; thus, collaboration on AM specific standards and enhancement of communication between stakeholders from project inception is recommended.

In-vitro viability of bone scaffolds fabricated using the adaptive foam reticulation technique.

The adaptive foam reticulation technique combines the foam reticulation and freeze casting methodologies of fabricating bone reparative scaffolds to offer a potential alternative to autografts. For the first time this paper studies the effect of processing on the mechanical properties and in-vitro cell growth of controllably generating a hierarchical structure of macro- (94 ± 6 to 514 ± 36 µm) and microporosity (2-30 µm) by the inclusion of camphene as a porogen during processing. Scaffolds were produced with porogen additions of 0-25 wt%. Porosity values of the structures of 85-96% were determined using the Archimedes technique and verified using X-ray Computed Tomography. The strength of the hydroxyapatite scaffolds, 5.70 ± 1.0 to 159 ± 61 kPa, correlated to theoretically determined values, 3.71 ± 0.8 to 134 ± 12 kPa, calculated by the novel incorporation of a shape factor into a standard equation. Fibroblast (3T3) and pre-osteoblast (MC3T3) cell growth was found to be significantly (P < 0.005) improved using 25 wt% porogen. This was supported by increased levels of alkaline phosphatase and was thought to result from greater dissolution as quantified by increased calcium levels in incubating media. The combination of these properties renders adaptive foam reticulation-fabricated scaffolds suitable for non-structural bone regenerative applications in non-load bearing bone defects.

Microstructural Evolution, Mechanical Properties, and Preosteoblast Cell Response of a Post-Processing-Treated TNT5Zr ß Ti Alloy Manufactured via Selective Laser Melting.

A Ti-34Nb-13Ta-5Zr (TNT5Zr) ß Ti alloy with a high strength-to-modulus ratio has been developed, showing its potential to become another candidate material in load-bearing implant applications. This work mainly investigates the microstructural evolution, mechanical properties, and biocompatibility of a post-processing-treated TNT5Zr alloy manufactured via selective laser melting (SLM). Transmission electron microscopy observation shows the existence of the single beta grain matrix and alpha precipitates along the grain boundary in the SLM + HIP manufactured TNT5Zr alloy (TNT5Zr-AF + HIP), and ellipsoidal nano-sized intragranular α″ precipitates (approx. 5-10 nm) were introduced after the subsequent low-temperature aging treatment. The precipitation strengthening enables the SLM + HIP + aging manufactured TNT5Zr (TNT5Zr-AF + HIPA) alloy to show a comparable ultimate tensile strength (853 ± 9 MPa) to that of the reference material (Ti64-AF + HIP, 926 ± 23 MPa). Including the inferior notch-like surface of the test pieces, the slip-band cracking that occurs in this ductile TNT5Zr-AF + HIPA alloy is regarded as the main factor in determining its fatigue strength (170 MPa). In vitro short-term biocompatibility evaluation reveals almost no significant difference in the preosteoblast viability, differentiation, and mineralization between TNT5Zr-AF + HIPA and the reference biomaterial (Ti64-AF + HIP).

An ECM-Mimetic Hydrogel to Promote the Therapeutic Efficacy of Osteoblast-Derived Extracellular Vesicles for Bone Regeneration.

The use of extracellular vesicles (EVs) is emerging as a promising acellular approach for bone regeneration, overcoming translational hurdles associated with cell-based therapies. Despite their potential, EVs short half-life following systemic administration hinders their therapeutic efficacy. EVs have been reported to bind to extracellular matrix (ECM) proteins and play an essential role in matrix mineralisation. Chitosan and collagen type I are naturally-derived pro-osteogenic biomaterials, which have been demonstrated to control EV release kinetics. Therefore, this study aimed to develop an injectable ECM-mimetic hydrogel capable of controlling the release of osteoblast-derived EVs to promote bone repair. Pure chitosan hydrogels significantly enhanced compressive modulus (2.48-fold) and osteogenic differentiation (3.07-fold), whilst reducing gelation times (2.09-fold) and proliferation (2.7-fold) compared to pure collagen gels (p ≤ 0.001). EV release was strongly associated with collagen concentration (R2 > 0.94), where a significantly increased EV release profile was observed from chitosan containing gels using the CD63 ELISA (p ≤ 0.001). Hydrogel-released EVs enhanced human bone marrow stromal cells (hBMSCs) proliferation (1.12-fold), migration (2.55-fold), and mineralisation (3.25-fold) compared to untreated cells (p ≤ 0.001). Importantly, EV-functionalised chitosan-collagen composites significantly promoted hBMSCs extracellular matrix mineralisation when compared to the EV-free gels in a dose-dependent manner (p ≤ 0.001). Taken together, these findings demonstrate the development of a pro-osteogenic thermosensitive chitosan-collagen hydrogel capable of enhancing the therapeutic efficacy of osteoblast-derived EVs as a novel acellular tool for bone augmentation strategy.

Photocurable antimicrobial silk-based hydrogels for corneal repair.

Corneal transplantation is the current gold standard treatment to restore visual acuity to patients with severe corneal diseases and injuries. Due to severe donor tissue shortage, efforts to develop a corneal equivalent have been made but the challenge remains unmet. Another issue of concern in ocular surgery is the difficult instillation and fast drainage of antibiotic ocular eye drops as bacterial infections can jeopardize implant success by delaying or impairing tissue healing. In this study, we developed antimicrobial silk-based hydrogels that have the potential to be photoactivated in situ, fully adapting to the corneal injury shape. Gentamicin-loaded methacrylated-silk (SilkMA) hydrogels were prepared within minutes using low UV intensity (3 mW/cm2 ). SilkMA gels provided a Young's modulus between 21 and 79 kPa together with a light transmittance spectrum and water content (83%-90%) similar to the human cornea. Polymer concentration (15%-25%) was found to offer a tool for tailoring the physical properties of the hydrogels. We confirmed that the methacrylation did not affect the material's in vitro degradation and biocompatibility by observing fibroblast adhesion and proliferation. Importantly, agar diffusion tests showed that the synthesized hydrogels were able to inhibit Staphylococcus aureus and Pseudomonas aeruginosa growth for 72 h. These characteristics along with their injectability and viscoelasticity demonstrate the potential of SilkMA hydrogels to be applied in several soft tissue engineering fields. As such, for the first time we demonstrate the potential of photocurable antimicrobial SilkMA hydrogels as a novel biomaterial to facilitate corneal regeneration.

Photocurable GelMA Adhesives for Corneal Perforations.

The current treatments for the management of corneal and scleral perforations include sutures and adhesives. While sutures are invasive, induce astigmatism and carry a risk of infection, cyanoacrylate glues are toxic, proinflammatory and form an opaque and rough surface that precludes vision. Consequently, the clinical need for a fast curing and strong tissue adhesive with minimised cytotoxicity and host inflammation remains unmet. In this paper, we engineer a gelatine methacryloyl (GelMA) adhesive that can be crosslinked in situ within 2 min using UV or visible light and a riboflavin (RF)/sodium persulfate (SPS) system. Optical coherence tomography (OCT) images demonstrated that the flowable GelMA adhesive could completely fill corneal wounds and restore the ocular curvature by forming a smooth contour on the ocular surface. Further, ex vivo studies in porcine eyes showed that GelMA bioadhesives exhibited burst pressures that were comparable to cyanoacrylates (49 ± 9 kPa), with the hydrogels exhibiting a transmittance (90%), water content (85%) and storage modulus (5 kPa) similar to the human cornea. Finally, using human dermal fibroblasts, we showed that our GelMA adhesive was non-toxic and could effectively support cell adhesion and proliferation. Taken together, the adhesive's performance, injectability and ease of administration, together with gelatin's availability and cost-effectiveness, make it a potential stromal filler or sealant for corneal and conjunctival applications.

Controlled Release of Epigenetically-Enhanced Extracellular Vesicles from a GelMA/Nanoclay Composite Hydrogel to Promote Bone Repair.

Extracellular vesicles (EVs) have garnered growing attention as promising acellular tools for bone repair. Although EVs' potential for bone regeneration has been shown, issues associated with their therapeutic potency and short half-life in vivo hinders their clinical utility. Epigenetic reprogramming with the histone deacetylase inhibitor Trichostatin A (TSA) has been reported to promote the osteoinductive potency of osteoblast-derived EVs. Gelatin methacryloyl (GelMA) hydrogels functionalised with the synthetic nanoclay laponite (LAP) have been shown to effectively bind, stabilise, and improve the retention of bioactive factors. This study investigated the potential of utilising a GelMA-LAP hydrogel to improve local retention and control delivery of epigenetically enhanced osteoblast-derived EVs as a novel bone repair strategy. LAP was found to elicit a dose-dependent increase in GelMA compressive modulus and shear-thinning properties. Incorporation of the nanoclay was also found to enhance shape fidelity when 3D printed compared to LAP-free gels. Interestingly, GelMA hydrogels containing LAP displayed increased mineralisation capacity (1.41-fold) (p ≤ 0.01) over 14 days. EV release kinetics from these nanocomposite systems were also strongly influenced by LAP concentration with significantly more vesicles being released from GelMA constructs as detected by a CD63 ELISA (p ≤ 0.001). EVs derived from TSA-treated osteoblasts (TSA-EVs) enhanced proliferation (1.09-fold), migration (1.83-fold), histone acetylation (1.32-fold) and mineralisation (1.87-fold) of human bone marrow stromal cells (hBMSCs) when released from the GelMA-LAP hydrogel compared to the untreated EV gels (p ≤ 0.01). Importantly, the TSA-EV functionalised GelMA-LAP hydrogel significantly promoted encapsulated hBMSCs extracellular matrix collagen production (≥1.3-fold) and mineralisation (≥1.78-fold) in a dose-dependent manner compared to untreated EV constructs (p ≤ 0.001). Taken together, these findings demonstrate the potential of combining epigenetically enhanced osteoblast-derived EVs with a nanocomposite photocurable hydrogel to promote the therapeutic efficacy of acellular vesicle approaches for bone regeneration.

Formulation of an antibacterial topical cream containing bioengineered honey that generates reactive oxygen species.

SurgihoneyRO™ (SHRO) is a bioengineered medicinal honey proven to eradicate multi-drug resistant strains of bacteria by delivering a controlled dose of reactive oxygen species (ROS). The urgent need for novel antimicrobial therapies capable of tackling pathogens that have developed resitance to existing antimicrobial medicines, such as antibiotics, makes SHRO a highly desirable biomaterial. However, its application is currently limited in the medical field due to undesirable material properties. This study aims to formulate the honey into a clinically viable topical cream whilst maintaining antimicrobial efficacy. SHRO droplets were emulsified to protect the active until activation in-situ. Xanthan gum (XG) and fumed silica (FS) thickener systems were explored, with both formulations able to inhibit the growth of S. aureus in-vitro. However, FS formulations exhibited significantly higher hydrogen peroxide release over a period of 7 days and resulted in larger zones of inhibition (42%) than XG formulations. Selection of the optimum FS formulation was made based on evaluation of the material characteristics by means of rheology and texture analysis. In place of the sticky and highly viscous initial SHRO product, desirable material characteristics for a topical product were achieved, including thixotropic shear-thinning behaviour and significantly lower cohesiveness (15.3-22.4 N) than standard SHRO formulations (79.9 N). Furthermore, the product exhibited a low contact angle on porcine skin, indicating that these formulations would spread favourably on the skin surface, demonstrate a favourable sensory perception and be retained on the skin, making for a more clinically effective product. This work is the first report of an engineered cream system to controllably deliver ROS to a wound site and demonstrate its ability of eradicating clinically relevant bacteria in vitro.

Hydrostatic pressure promotes chondrogenic differentiation and microvesicle release from human embryonic and bone marrow stem cells.

Mechanical stimulation plays in an important role in regulating stem cell differentiation and their release of extracellular vesicles (EVs). In this study, effects of low magnitude hydrostatic pressure (HP) on the chondrogenic differentiation and microvesicle release from human embryonic stem cells (hESCs) and human bone marrow stem cells (hBMSCs) are examined. hESCs were differentiated into chondroprogenitors and then embedded in fibrin gels and subjected to HP (270 kPa, 1 Hz, 5 days per week). hBMSC pellets were differentiated in chondrogenic media and subjected to the same regime. HP significantly enhanced ACAN expression in hESCs. It also led to a significant increase in DNA content, sGAG content and total sGAG/DNA level in hBMSCs. Furthermore, HP significantly increased microvesicle protein content released from both cell types. These results highlight the benefit of HP bioreactor in promoting chondrogenesis and EV production for cartilage tissue engineering.

The influence of zirconium content on the microstructure, mechanical properties, and biocompatibility of in-situ alloying Ti-Nb-Ta based ß alloys processed by selective laser melting.

This study investigates Ti-Nb-Ta based ß alloys with different zirconium additions (0, 5, 9 wt%) manufactured by SLM. A low level of as-fabricated defects is obtained: the relative density of TNT (Z) alloys is >99.97% with the keyhole size in a range of 3-20 µm. BF TEM images combining SAD patterns of TNT(Z) alloys show single ß phase obtained inside the beta matrix; BF-STEM images reveal potential nano-scale grain boundary alpha phase precipitation. Zirconium functions as a neutral element in these high ß-stabilized Ti-Nb-Ta based alloys. An increase in Vickers hardness and UTS caused by zirconium additions is observed, which is explained by beta grain refinement because higher degree of undercooling occurs. Corrosion ions of TNT(Z) alloys released from immersion testing at each time intervals show extremely small concentrations (<10 µg/L). It indicated that good biocompatibility during culture with the negligible corrosion ions. High strength-to-modulus ratio ß Ti alloys together with excellent biological response show their prospect for biomedical applications.

Development of a Bone-Mimetic 3D Printed Ti6Al4V Scaffold to Enhance Osteoblast-Derived Extracellular Vesicles' Therapeutic Efficacy for Bone Regeneration.

Extracellular Vesicles (EVs) are considered promising nanoscale therapeutics for bone regeneration. To date, EVs are typically procured from cells on 2D tissue culture plastic, an artificial environment that limits cell growth and does not replicate in situ biochemical or biophysical conditions. This study investigated the potential of 3D printed titanium scaffolds coated with hydroxyapatite to promote the therapeutic efficacy of osteoblast-derived EVs. Ti6Al4V titanium scaffolds with different pore sizes (500 and 1000 µm) and shapes (square and triangle) were fabricated by selective laser melting. A bone-mimetic nano-needle hydroxyapatite (nnHA) coating was then applied. EVs were procured from scaffold-cultured osteoblasts over 2 weeks and vesicle concentration was determined using the CD63 ELISA. Osteogenic differentiation of human bone marrow stromal cells (hBMSCs) following treatment with primed EVs was evaluated by assessing alkaline phosphatase activity, collagen production and calcium deposition. Triangle pore scaffolds significantly increased osteoblast mineralisation (1.5-fold) when compared to square architectures (P ≤ 0.001). Interestingly, EV yield was also significantly enhanced on these higher permeability structures (P ≤ 0.001), in particular (2.2-fold) for the larger pore structures (1000 µm). Furthermore osteoblast-derived EVs isolated from triangular pore scaffolds significantly increased hBMSCs mineralisation when compared to EVs acquired from square pore scaffolds (1.7-fold) and 2D culture (2.2-fold) (P ≤ 0.001). Coating with nnHA significantly improved osteoblast mineralisation (>2.6-fold) and EV production (4.5-fold) when compared to uncoated scaffolds (P ≤ 0.001). Together, these findings demonstrate the potential of harnessing bone-mimetic culture platforms to enhance the production of pro-regenerative EVs as an acellular tool for bone repair.

A feasible route for the design and manufacture of customised respiratory protection through digital facial capture.

The World Health Organisation has called for a 40% increase in personal protective equipment manufacturing worldwide, recognising that frontline workers need effective protection during the COVID-19 pandemic. Current devices suffer from high fit-failure rates leaving significant proportions of users exposed to risk of viral infection. Driven by non-contact, portable, and widely available 3D scanning technologies, a workflow is presented whereby a user's face is rapidly categorised using relevant facial parameters. Device design is then directed down either a semi-customised or fully-customised route. Semi-customised designs use the extracted eye-to-chin distance to categorise users in to pre-determined size brackets established via a cohort of 200 participants encompassing 87.5% of the cohort. The user's nasal profile is approximated to a Gaussian curve to further refine the selection in to one of three subsets. Flexible silicone provides the facial interface accommodating minor mismatches between true nasal profile and the approximation, maintaining a good seal in this challenging region. Critically, users with outlying facial parameters are flagged for the fully-customised route whereby the silicone interface is mapped to 3D scan data. These two approaches allow for large scale manufacture of a limited number of design variations, currently nine through the semi-customised approach, whilst ensuring effective device fit. Furthermore, labour-intensive fully-customised designs are targeted as those users who will most greatly benefit. By encompassing both approaches, the presented workflow balances manufacturing scale-up feasibility with the diverse range of users to provide well-fitting devices as widely as possible. Novel flow visualisation on a model face is presented alongside qualitative fit-testing of prototype devices to support the workflow methodology.

Methacrylated Silk Fibroin Hydrogels: pH as a Tool to Control Functionality.

The last decade has witnessed significant progress in the development of photosensitive polymers for in situ polymerization and 3D printing applications. Light-mediated sol-gel transitions have immense potential for tissue engineering applications as cell-laden materials can be crosslinked within minutes under mild environmental conditions. Silk fibroin (SF) is extensively explored in regenerative medicine applications due to its ease of modification and exceptional mechanical properties along with cytocompatibility. To efficiently design SF materials, the in vivo assembly of SF proteins must be considered. During SF biosynthesis, changes in pH, water content, and metal ion concentrations throughout the silkworm gland divisions drive the transition from liquid silk to its fiber form. Herein, we study the effect of the glycidyl-methacrylate-modified SF (SilkMA) solution pH on the properties and secondary structure of SilkMA hydrogels by testing formulations prepared at pH 5, 7, and 8. Our results demonstrate an influence of the prepolymer solution pH on the hydrogel rheological properties, compressive modulus, optical transmittance, and network swellability. The hydrogel pH did not affect the in vitro viability and morphology of human dermal fibroblasts. This work demonstrates the utility of the solution pH to tailor the SilkMA conformational structure development toward utility and function and shows the need to strictly control the pH to reduce batch-to-batch variability and ensure reproducibility.