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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 iniStaphylococcus epidermidis/icolonization was observed on both polished and passivated samples, which was linked to high surface free energy donor γsup-/supvalues in the acid-base, γsupAB/supcomponent. 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 iniS. epidermidis/icolonization, 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.

Hexametaphosphate (HMP) is an inorganic condensed phosphate, which has been used in a wide variety of industries for nearly a century, originally patented to deflocculate clay and soften hard water...

Water is a fundamental component of many biological systems. The ability to detect water therefore provides great insight into system functionality, particularly in the development of disease. In this work, the high interaction of terahertz radiation with water, paired with the dependence of the dynamics of water molecules with varying temperature, is utilised to monitor changes in the composition of bone tissue. Heterotopic ossification (HO) bone samples and deionised free water are measured using terahertz time-domain spectroscopy for varying environmental temperatures, for prospective use in disease diagnosis.

The incidence of kidney stones is increasing worldwide, and recurrence is common (50% within 5 years). Citrate, the current gold standard therapy, which is usually given as potassium or sodium salts, is used because it raises urine pH and chelates calcium, the primary component of up to 94% of stones. In this study hexametaphosphate (HMP), a potent calcium chelator, was found to be 12 times more effective at dissolving calcium oxalate, the primary component of kidney stones, than citrate. HMP was also observed to be effective against other common kidney stone components, namely calcium phosphate and struvite (magnesium ammonium phosphate). Interestingly, HMP was capable of raising the zeta potential of calcium oxalate particles from -15.4 to -34.6 mV, which may prevent stone growth by aggregation, the most rapid growth mechanism, and thus avert occlusion. Notably, HMP was shown to be up to 16 times as effective as citrate at dissolving human kidney stones under simulated physiological conditions. It may thus be concluded that HMP is a promising potential therapy for calcium and struvite kidney stones.

Structured fluid biomaterials, including gels, creams, emulsions and particle suspensions, are used extensively across many industries, including great interest within the medical field as controlled release vehicles to improve the therapeutic benefit of delivered drugs and cells. Colloidal forces within these materials create multiscale cohesive interactions, giving rise to intricate microstructures and physical properties, exemplified by increasingly complex mathematical descriptions. Yield stresses and viscoelasticity, typically arising through the material microstructure, vastly improve site-specific retention, and protect valuable therapeutics during application. One powerful application route is spraying, a convenient delivery method capable of applying a thin layer of material over geometrically uneven surfaces and hard-to-reach anatomical locations. The process of spraying is inherently disruptive, breaking a bulk fluid in successive steps into smaller elements, applying multiple forces over several length scales. Historically, spray research has focused on simple, inviscid solutions and dispersions, far from the complex microstructures and highly viscoelastic properties of concentrated colloidal biomaterials. The cohesive forces in colloidal biomaterials appear to conflict with the disruptive forces that occur during spraying. This review explores the physical bass and mathematical models of both the multifarious material properties engineered into structured fluid biomaterials and the disruptive forces imparted during the spray process, in order to elucidate the challenges and identify opportunities for rational design of sprayable, structured fluid biomaterials.

The treatment of spinal cord injury (SCI) is a complex challenge in regenerative medicine, complicated by the low intrinsic capacity of CNS neurons to regenerate their axons and the heterogeneity in size, shape and extent of human injuries. For example, some contusion injuries do not compromise the dura mater and in such cases implantation of preformed scaffolds or drug delivery systems may cause further damage. Injectable in situ thermosensitive scaffolds are therefore a less invasive alternative. In this study, we report the development of a novel, flowable, thermosensitive, injectable drug delivery system comprising bovine collagen (BC) and fibrinogen (FB) that forms a solid BC/FB gel (Gel) immediately upon exposure to physiological conditions and can be used to deliver reparative drugs, such as the naturally occurring anti-inflammatory, anti-scarring agent Decorin, into adult rat spinal cord lesion sites. In dorsal column lesions of adult rats treated with the Gel + Decorin, cavitation was completely suppressed and instead lesion sites became filled with injury-responsive cells and extracellular matrix materials, including collagen and laminin. Decorin increased the intrinsic potential of dorsal root ganglion neurons (DRGN) by increasing their expression of regeneration associated genes (RAGs), enhanced local axon regeneration/sprouting, as evidenced both histologically and by improved electrophysiological, locomotor and sensory function recovery. These results suggest that this drug formulated, injectable hydrogel has the potential to be further studied and translated into the clinic.

Despite its great potential, the realisation of terahertz dielectric imaging for biomedical application is limited by experimental challenges, such as reference displacements and Fabry-Perot reflections in thin samples. In this work, an algorithm is developed to overcome such complications for time-domain spectroscopy measurements in reflection configuration. The algorithm is demonstrated on human bone slices without encapsulation, showing great promise for application in extracting biometric information from a broad range of structures.

The realisation of hyperspectral terahertz imaging is a significant step towards understanding of the life sciences on all scales. A key to this understanding is the retrieval of dielectric properties from such images, a task which is plagued by experimental limitations, challenging the terahertz community for more than two decades. In this contribution, we propose a new combined retrieval methodology to overcome misalignments and Fabry-Perot effects on the extraction of the dielectric properties of human bone samples through the combination of the Kramers-Kronig relations and Fabry-Perot reflection modelling. Results extracted from ∼100 µm human bone slices composed largely of collagen are consistent with those measured for pristine collagen samples. This represents another stepping-stone towards the adoption of terahertz imaging into pre- and clinical practice.

Nanostructured, inorganic microspheres have many industrial applications, including catalysis, electronics, and particularly drug delivery, with several advantages over their organic counterparts. However, many current production methods require high energy input, use of harmful chemicals, and extensive processing. Here, the self-assembly of calcium pyrophosphate into nanofibre microspheres is reported. This process takes place at ambient temperature, with no energy input, and only salt water as a by-product. The formation of these materials is examined, as is the formation of nanotubes when the system is agitated, from initial precipitate to crystallisation. A mechanism of formation is proposed, whereby the nanofibre intermediates are formed as the system moves from kinetically favoured spheres to thermodynamically stable plates, with a corresponding increase in aspect ratio. The functionality of the nanofibre microspheres as targeted enteric drug delivery vehicles is then demonstrated in vitro and in vivo, showing that the microspheres can pass through the stomach while protecting the activity of a model protein, then release their payload in intestinal conditions.

Highlights • Subjective scar measures have poor reliability unless repeated by more than one assessor. • Objective scar measures have been demonstrated to have good to excellent reliability. • Physical symptoms of scars such as pain and itch were found to be more important to patients compared to surface, area and colour although this finding was not sustained when corrected for multiple comparisons., Background Research into the treatment of hypertrophic burn scar is hampered by the variability and subjectivity of existing outcome measures. This study aims to measure the inter- and intra-rater reliability of a panel of subjective and objective burn scar measurement tools. Methods Three independent assessors evaluated 55 scar and normal skin sites using subjective (modified Vancouver Scar Scale [mVSS] & Patient and Observer Scar Assessment Scale [POSAS]) and objective tools. The intra-class correlation coefficient was utilised to measure reliability (acceptable when >0.70). Patient satisfaction with the different tools and scar parameter importance were assessed via questionnaires. Results The inter-rater reliabilities of the mVSS and POSAS were below the acceptable limit. For erythema and pigmentation, all of the Scanoskin and DSM II measures (except the b* value) had acceptable to excellent intra and inter-rater reliability. The Dermascan ultrasound (dermal thickness, intensity) had excellent intra- and inter-rater reliability (>0.90). The Cutometer R0 (firmness) had acceptable reliability but not R2 (gross elasticity). All objective measurement tools had good overall satisfaction scores. Patients rated scar related pain and itch as more important compared to appearance although this finding was not sustained when corrected for multiple comparisons. Conclusion The objective scar measures demonstrated acceptable to excellent intra- and inter-rater reliability and performed better than the subjective scar scales.

Study Design An observational descriptive study based on a single cohort of patients. Objective To determine whether spinal facet osteoblasts at the curve apex display a different phenotype to osteoblasts from outside the curve in adolescent idiopathic scoliosis (AIS) patients. Summary of Background Data Intrinsic differences in the phenotype of spinal facet bone tissue and in spinal osteoblasts have been implicated in the pathology of AIS. However, no study has compared the phenotype of facet osteoblasts at the curve apex compared with outside the curve in AIS patients. Methods Facet spinal tissue was collected perioperatively from three sites, the concave and convex side at the curve apex and from outside the curve (noncurve) from three AIS female patients aged 13–16 years. Spinal tissue was analyzed by micro–computed tomography to determine bone mineral density (BMD) and trabecular structure. Primary osteoblasts were cultured from concave, convex, and noncurve facet bone chips. The phenotype of osteoblasts was determined by assessment of cellular proliferation, cellular metabolism (alkaline phosphatase and Seahorse Analyzer), bone nodule mineralization (Alizarin red assay), and the mRNA expression of Wnt signaling genes (quantitative reverse transcriptase polymerase chain reaction). Results Convex facet tissue exhibited greater BMD and trabecular thickness, compared with concave facet tissue. Osteoblasts at the convex side of the curve apex exhibited a significantly higher proliferative and metabolic phenotype and a greater capacity to form mineralized bone nodules, compared with concave osteoblasts. mRNA expression of SKP2 was significantly greater in both concave and convex osteoblasts, compared with noncurve osteoblasts. The expression of SFRP1 was significantly downregulated in convex osteoblasts, compared with either concave or noncurve. Conclusions Intrinsic differences that affect osteoblast function are exhibited by spinal facet osteoblasts at the curve apex in AIS patients. Level of Evidence Level IV, Prognostic.

Autologous cell transplantation was introduced to clinical practice nearly four decades ago to enhance burn wound re-epithelialisation. Autologous cultured or uncultured cells are often delivered to the surface in saline-like suspensions. This delivery method is limited because droplets of the sprayed suspension form upon deposition and run across the wound bed, leading to uneven coverage and cell loss. One way to circumvent this problem would be to use a gel-based material to enhance surface retention. Fibrin systems have been explored as co-delivery system with keratinocytes or as adjunct to 'seal' the cells following spray delivery, but the high costs and need for autologous blood has impeded its widespread use. Aside from fibrin gel, which can exhibit variable properties, it has not been possible to develop a gel-based carrier that solidifies on the skin surface. This is because it is challenging to develop a material that is sprayable but gels on contact with the skin surface. The manuscript reports the use of an engineered carrier device to deliver cells via spraying, to enhance retention upon a wound. The device involves shear-structuring of a gelling biopolymer, gellan, during the gelation process; forming a yield-stress fluid with shear-sensitive behaviours, known as a fluid gel. In this study, a formulation of gellan gum fluid gels are reported, formed with from 0.75 or 0.9% (w/v) polymer and varying the salt concentrations. The rheological properties and the propensity of the material to wet a surface were determined for polymer modified and non-polymer modified cell suspensions. The gellan fluid gels had a significantly higher viscosity and contact angle when compared to the non-polymer carrier. Viability of cells was not impeded by encapsulation in the gellan fluid gel or spraying. The shear thinning property of the material enabled it to be applied using an airbrush and spray angle, distance and air pressure were optimised for coverage and viability. STATEMENT OF SIGNIFICANCE: Spray delivery of skin cells has successfully translated to clinical practice. However, it has not yet been widely accepted due to limited retention and disputable cell viability in the wound. Here, we report a method for delivering cells onto wound surfaces using a gellan-based shear-thinning gel system. The viscoelastic properties allow the material to liquefy upon spraying and restructure rapidly on the surface. Our results demonstrate reduced run-off from the surface compared to currently used low-viscosity cell carriers. Moreover, encapsulated cells remain viable throughout the process. Although this paper studies the encapsulation of one cell type, a similar approach could potentially be adopted for other cell types. Our data supports further studies to confirm these results in in vivo models.

The rise of antibiotic resistant bacterial species is driving the requirement for medical devices that minimise infection risks. Antimicrobial functionality may be achieved by modifying the implant design to incorporate a reservoir that locally releases a therapeutic. For this approach to be successful it is critical that mechanical functionality of the implant is maintained. This study explores the opportunity to exploit the design flexibilities possible using additive manufacturing to develop porous lattices that maximise the volume available for drug loading while maintaining load-bearing capacity of a hip implant. Eight unit cell types were initially investigated and a volume fraction of 30% was identified as the lowest level at which all lattices met the design criteria in ISO 13314. Finite element analysis (FEA) identified three lattice types that exhibited significantly lower displacement (10-fold) compared with other designs; Schwartz primitive, Schwartz primitive pinched and cylinder grid. These lattices were additively manufactured in Ti-6Al-4V using selective laser melting. Each design exceeded the minimum strength requirements for orthopaedic hip implants according to ISO 7206-4. The Schwartz primitive (Pinched) lattice geometry, with 10% volume fill and a cubic unit cell period of 10, allowed the greatest void volume of all lattice designs whilst meeting the fatigue requirements for use in an orthopaedic implant (ISO 7206-4). This paper demonstrates an example of how additive manufacture may be exploited to add additional functionality to medical implants.

Humans utilise biomineralisation in the formation of bone and teeth. Human biomineralisation processes are defined by the transformation of an amorphous phosphate-based precursor to highly organised nanocrystals. Interestingly, ionic phosphate species not only provide a fundamental building block of biological mineral, but rather exhibit several diverse roles in mediating mineral formation in the physiological milieu. In this review, we focus on elucidating the complex roles of phosphate ions and molecules within human biomineralisation pathways, primarily referring to the nucleation and crystallisation of bone mineral.

Objective The study aims were to determine whether BST-CarGel, a chitosan scaffold for cartilage repair, can be mixed with bone marrow aspirate concentrate (BMAC) to create a cell seeded implant with comparative properties to standard BST-CarGel mixed with blood. Design Whole blood and bone marrow were harvested from 12 patients who underwent cartilage repair surgery using BMAC after informed consent. A validated in vitro testing model was used to assess the following 6 conditions: (1) BST-CarGel mixed with whole blood (CG-WB), (2) BST-CarGel mixed with bone marrow (CG-BM), (3) BST-CarGel mixed with bone marrow concentrate (CG-BMAC), (4) whole blood (WB), (5) bone marrow (BM), and (6) bone marrow concentrate and batroxobin (BMAC-BTX). Cell retention and viability within the BST-CarGel/BMAC clots were investigated. Results In our study, BM and BMAC (processed using the Harvest, SmartPrep2 system and reactivated with batroxibin) when combined with BST-CarGel produced a product that had similar clot contraction, macroscopic properties, and histological appearance to standard BSTCarGel mixed with blood. Mononucleated cells from the BMAC were retained within the scaffold and remained viable until clot dissolution in vitro. Conclusions By combining BST-CarGel with BMAC in the manner described, bone marrow–derived mononucleated cells can be retained within the chondral defect potentially negating the need for microfracture. Further in vivo work is required to confirm these potential benefits and determine if this combination will result in more durable cartilage repair and improved clinical outcomes.

Powder bed fusion techniques enable the production of customized and complex devices that meet the requirements of the end user and target application. The medical industry relies on these additive manufacturing technologies for the advantages that these methods offer to accurately fit the patients’ needs. Besides the recent improvements, the production process of 3D printed bespoke implants still requires optimization to achieve the optimal properties that can mimic both the chemical and mechanical characteristics of the anatomical region of interest. In particular, the surface properties of an implant device are crucial to obtain a strong interface and connection with the physiological environment. The layer by layer manufacturing processes lead to the production of complex and high-performance substrates but always require surface treatments during post-processing to improve the implant interaction with the natural tissues and promote a shorter assimilation for the fast recovery and wellness of the patient. Although the surface finishing can be tailored to enhance cells adhesion, proliferation and differentiation in contact with a metal implant, the same surface properties can have a different outcome when dealing with bacteria. This work aims to provide a preliminary analysis on how different post-processing techniques have distinct effects on cells and bacteria colonization of 3D printed titanium implants. The goal of the paper is to highlight the importance of the identification of an optimized methodology for the surface treatment of Ti6Al4V samples produced by Selective Laser Melting (SLM) that improves the implant antimicrobial properties and promotes the osseointegration in a long-term period.

The COVID-19 global pandemic, as well as the widespread persistence of influenza and the common cold, create the need for new medical devices such as nasal sprays to prevent viral infection and transmission. Carrageenan, a sulfated polysaccharide, has a broad, non-pharmacological antiviral capacity, however it performs poorly in two key areas; spray coverage and mucoadhesion. Therefore gellan, another polysaccharide, was investigated as an excipient to improve these properties. It was found that viscoelastic relaxation time was the key predictor of spray coverage, and by reducing this value from 2.5 to 0.25 s, a mix of gellan and carrageenan gave more than four times the coverage of carrageenan alone (p < 0.0001). Gellan also demonstrated enhanced adhesion to a mucus analog that increased significantly with time (p < 0.0001), suggesting the development of specific gellan–mucin interactions. This property was conferred to carrageenan on mixing the two polymers. Together, this data suggests that gellan is a promising excipient to improve both sprayability and mucoadhesion of carrageenan for use in antiviral nasal sprays.

Prophylactic antibiotic bone cements are extensively used in orthopaedics. However, the development of antimicrobial resistance to antibiotics, demonstrates a need to find alternative treatments. Herein, an antimicrobial honey (SurgihoneyRO-SHRO) has been successfully incorporated into a calcium sulphate (CS) based cement to produce a hard tissue scaffold with the ability to inhibit bacterial growth. Antimicrobial properties elicited from SHRO are predominantly owed to the water-initiated production of reactive oxygen species (ROS). As an alternative to initially loading CS cement with SHRO, in order to prevent premature activation, SHRO was added into the already developing cement matrix, locking available water into the CS crystal structure before SHRO addition. Promisingly, this methodology produced > 2.5 times (715.0 ± 147.3 μM/mL/g) more ROS over 24 h and exhibited a compressive strength (32.2 ± 5.8 MPa) comparable to trabecular bone after 3 weeks of immersion. In-vitro the SHRO loaded CS scaffolds were shown to inhibit growth of clinically relevant organisms, Staphylococcus aureus and Pseudomonas aeruginosa, with comparable potency to equivalent doses of gentamicin. Encouragingly, formulations did not inhibit wound healing or induce an inflammatory response from osteoblasts. Overall this study highlights the prophylactic potential of CS-SHRO cements as an alternative to traditional antibiotics.

This study presents experimental data of a fluidized-bed bioreactor for the cultivation of encapsulated pancreatic beta-cells. The fluidization quality for the bioreactor was evaluated at different flow rate using bed-expansion parameters. Homogeneous distribution of microcapsules was achieved at a flow rate of 2000 μL/min. This enabled efficient contact between the encapsulated cells and medium, which contributed to high cell viability. Microcapsule breakage was

Airborne pathogens pose high risks in terms of both contraction and transmission within the respiratory pathways, particularly the nasal region. However, there is little in the way of adequate intervention that can protect an individual or prevent further spread. This study reports on a nasal formulation with the capacity to combat such challenges, focusing on severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). Formulation of a polysaccharide‐based spray, known for its mucoadhesive properties, is undertaken and it is characterized for its mechanical, spray distribution, and antiviral properties. The ability to engineer key mechanical characteristics such as dynamic yield stresses and high coverage is shown, through systematic understanding of the composite mixture containing both gellan and λ‐carrageenan. Furthermore, the spray systems demonstrate highly potent capacities to prevent SARS‐CoV‐2 infection in Vero cells, resulting in complete inhibition when either treating, the cells, or the virus, prior to challenging for infection. From this data, a mechanism for both prophylaxis and prevention is proposed; where entrapment within a polymeric coating sterically blocks virus uptake into the cells, inactivating the virus, and allowing clearance within the viscous medium. As such, a fully preventative spray is formulated, targeted at protecting the lining of the upper respiratory pathways against SARS‐CoV‐2., There is a high risk of transmission of airborne pathogens through the nasal epithelium. This study reports a novel nasal spray, which is designed to maximize surface coverage and prevent infection through physical entrapment and inhibition of infection by severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2).

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.

The growing threat of bacterial resistance to antibiotics is driving an increasing need for new antimicrobial strategies. This work demonstrates the potential of magnesium oxychloride cements (MOC) to be used as inorganic antimicrobial biomaterials for bone augmentation. An injectable formulation was identified at a powder to liquid ratio of 1.4 g mL−1, with an initial setting time below 30 mins and compressive strength of 35 ± 9 MPa. Supplementation with Ag3PO4 to enhance the antimicrobial efficacy of MOC was explored, and shown via real time X-ray diffraction to retard the formation of hydrated oxychloride phases by up to 30%. The antimicrobial efficacy of MOC was demonstrated in vitro against Staphylococcus aureus and Pseudomonas aeruginosa, forming zones of inhibition and significantly reducing viability in broth culture. Enhanced efficacy was seen for silver doped formulations, with complete eradication of detectable viable colonies within 3 h, whilst retaining the cytocompatibility of MOC. Investigating the antimicrobial mode of action revealed that Mg and Ag release and elevated pH contributed to MOC efficacy. Sustained silver release was demonstrated over 14 days, suggesting the Ag3PO4 modified formulation offers two mechanisms of infection treatment, combining the inherent antimicrobial properties of MOC with controlled release of inorganic antimicrobials.

The capacity to study the deposition of mineral within a hydrogel structure is of significant interest to a range of therapies that seek to replace the hard tissues and the hard-soft tissue interface. Here, a method is presented that utilises Confocal Raman microscopy as a tool for monitoring mineralisation within hydrogels. Synthetic hard-soft material interfaces were fabricated by apposing brushite (a sparingly soluble calcium phosphate) and biopolymer gel monoliths. The resulting structures were matured over a period of 28 days in phosphate buffered saline. Confocal Raman microscopy of the interfacial region showed the appearance of calcium phosphate salt deposits away from the original interface within the biopolymeric structures. Furthermore, the appearance of octacalcium phosphate and carbonated hydroxyapatite was observed in the region of the brushite cement opposing the biopolymer gel. This study describes not only a method for analysing these composite structures, but also suggests a method for recapitulating the graduated tissue structures that are often found in vivo.

Injectable biomaterials are becoming increasingly popular for the minimally invasive delivery of drugs and cells. These materials are typically more viscous than traditional aqueous injections and may be semi-solid, therefore, their injectability cannot be assumed. This protocol describes a method to objectively assess the injectability of these materials using a standard mechanical tester. The syringe plunger is compressed by the crosshead at a set rate, and the force is measured. The maximum or plateau force value can then be used for comparison between samples, or to an absolute force limit. This protocol can be used with any material, and any syringe and needle size or geometry. The results obtained may be used to make decisions about formulations, syringe and needle sizes early in the translational process. Further, the effects of altering formulations on injectability may be quantified, and the optimum time to inject temporally changing materials determined. This method is also suitable as a reproducible way to examine the effects of injection on a material, to study phenomena such as self-healing and filter pressing or study the effects of injection on cells. This protocol is faster and more directly applicable to injectability than rotational rheology, and requires minimal post processing to obtain key values for direct comparisons.

Calcium phosphates are used widely as orthopaedic implants and in nanocrystalline form to enable the transfer of genetic material into cells. Despite widespread use, little is known about their fate after they have crossed the cell membrane. Here we present a method of surface modification of silicon-substituted hydroxyapatite (SiHA) through a silane group, which enables the engraftment of a fluorescent dye to facilitate real-time biological tracking. Surface modification of the nanocrystal surface was undertaken using (3-mercaptopropyl)trimethoxysilane (MPTS), which presented a thiol for the further attachment of a fluorophore. Successful modification of the surface was demonstrated using zeta potential measurements and fluorescence microscopy and the number of thiol groups at the surface was quantified using Ellman's reagent. In vitro experiments using the fluorescently modified particles enabled the discrimination of the calcium phosphate particulate from other biological debris following internalisation by a population of MC3T3 (pre-osteoblast) cells and the particles were shown to maintain fluorescence for 24 hours without quenching. The successful modification of the surface of SiHA with thiol groups offers the tantalising possibility of the intracellular growth factor delivery.

The growing threat of bacterial resistance to antibiotics is driving an increasing need for new antimicrobial strategies. This work demonstrates the potential of magnesium oxychloride cements (MOC) to be used as inorganic antimicrobial biomaterials for bone augmentation. An injectable formulation was identified at a powder to liquid ratio of 1.4 g mL-1, with initial setting time below 30 mins and compressive strength of 35 MPa. Supplementation with Ag3PO4 to enhance antimicrobial efficacy of MOC was considered, and shown via real-time X-ray diffraction to retard formation of hydrated oxychloride phases by up to 30%. The antimicrobial efficacy of MOC was demonstrated in vitro against Staphylococcus aureus, with cement extracts after 72 hours of aging reducing the concentration of viable bacteria by a factor 107 CFU mL-1 after 24 hours culture. Enhanced efficacy was seen for silver doped formulations, with complete eradication of detectable viable colonies within 3 hours. Investigating the antimicrobial mode of action revealed that Mg and Ag release and elevated pH contributed to efficacy. Interestingly, sustained silver release was demonstrated over 14 days, suggesting the Ag3PO4 modified formulation offers two mechanisms of infection treatment, combining the inherent antimicrobial properties of MOC with controlled release of inorganic antimicrobials.

The incidence of blast injuries is increasing, in both the civilian and combat settings. Heterotopic ossification (HO), the aberrant growth of bone outside of the skeleton, is a common complication as a consequence of these injuries. HO can cause chronic pain and skin ulceration and prevent prosthetic limb fitting, significantly delaying rehabilitation in these patients. Current preventions, which were developed for HO formed following hip surgery, show inconsistent efficacy and side effects that make them intolerable for patients with high-energy injuries. This leaves surgical excision as the only available treatment. The biological processes behind HO are complex, with several cell types able to differentiate down HO tissue lineages, and it is likely that several pathways exist concurrently. However, as the biological mechanisms are becoming clearer, new targets are being identified and novel drugs developed for HO prophylaxis. The goal of these advances is to provide new therapies to prevent HO and improve the quality of life for blast-injured patients.

A diverse range of complex patterns and mineralised hierarchical microstructures can be derived from chemobrionic systems, with formation driven by complex reaction-diffusion mechanisms far from thermodynamic equilibrium. In these experiments, self-assembling calcium phosphate tubes are generated using hydrogels made with 1 M calcium solutions layered with solutions of dibasic sodium phosphate over a range of concentrations between 0.2-1 M. Self-assembling structures prepared using 0.8 M dibasic sodium phosphate solutions were selected to assess cell-material interactions. Candidate chemobrionic scaffolds were characterised by micro-X-Ray fluorescence (μ-XRF) spectroscopy, Raman spectroscopy, powder X-ray diffraction (XRD), helium pycnometry and scanning electron microscopy (SEM). As prepared tubes were formed from non-stoichiometric hydroxyapatite (HA, Ca10-x(PO4)6-x(HPO4)x(OH)2-x (0 ≤x≤ 1)), which was confirmed as calcium deficient hydroxyapatite (CDHA, Ca9(PO4)5HPO4OH). Thermal treatment of tubes in air at 650 °C for 4 h converted the structures to beta tricalcium phosphate (β-TCP, β-Ca3(PO4)2). The potential of these scaffolds to support the attachment of bone marrow derived mesenchymal stem cells (BMSCs) was investigated for the first time, and we demonstrate cell attachment and elongation on the fabricated tubular structures.

Magnetic Resonance Imaging (MRI) is critical in diagnosing post-operative complications following implant surgery and imaging anatomy adjacent to implants. Increasing field strengths and use of gradient-echo sequences have highlighted difficulties from susceptibility artefacts in scan data. Artefacts manifest around metal implants, including those made from titanium alloys, making detection of complications (e.g. bleeding, infection) difficult and hindering imaging of surrounding structures such as the brain or inner ear. Existing research focusses on post-processing and unorthodox scan sequences to better capture data around these devices. This study proposes a complementary up-stream design approach using lightweight structures produced via additive manufacturing (AM). Strategic implant mass reduction presents a potential tool in managing artefacts. Uniform specimens of Ti-6Al-4V structures, including lattices, were produced using the AM process, selective laser melting, with various unit cell designs and relative densities (3.1%–96.7%). Samples, submerged in water, were imaged in a 3T MRI system using clinically relevant sequences. Artefacts were quantified by image analysis revealing a strong linear relationship (RR2 = 0.99) between severity and relative sample density. Likewise, distortion due to slice selection errors showed a squared relationship (RR2 = 0.92) with sample density. Unique artefact features were identified surrounding honeycomb samples suggesting a complex relationship exists for larger unit cells. To demonstrate clinical utility, a honeycomb design was applied to a representative cranioplasty. Analysis revealed 10% artefact reduction compared to traditional solid material illustrating the feasibility of this approach. This study provides a basis to strategically design implants to reduce MRI artefacts and improve post-operative diagnosis capability. Statement of Significance MRI susceptibility artefacts surrounding metal implants present a clinical challenge for the diagnosis of post-operative complications relating to the implant itself or underlying anatomy. In this study for the first time we demonstrate that additive manufacturing may be exploited to create lattice structures that predictably reduce MRI image artefact severity surrounding titanium alloy implants. Specifically, a direct correlation of artefact severity, both total signal loss and distortion, with the relative material density of these functionalised materials has been demonstrated within clinically relevant MRI sequences. This approach opens the door for strategic implant design, utilising this structurally functionalised material, that may improve post-operative patient outcomes and compliments existing efforts in this area which focus on data acquisition and post-processing methods.

Articular cartilage is a viscoelastic tissue whose structural integrity is important in maintaining joint health. To restore the functionality of osteoarthritic joints it is vital that regenerative strategies mimic the dynamic loading response of cartilage and bone. Here, a rotating simplex model was employed to optimise the composition of agarose and gellan hydrogel constructs structured with hydroxyapatite (HA) with the aim of obtaining composites mechanically comparable to human cartilage in terms of their ability to dissipate energy. Addition of ceramic particles was found to reinforce both matrices up to a critical concentration (< 3w/v%). Beyond this, larger agglomerates were formed, as evidenced by micro computed tomography data, which acted as stress risers and reduced the ability of composites to dissipate energy demonstrated by a reduction in tan δ values. A maximum compressive modulus of 450.7±24.9 kPa was achieved with a composition of 5.8w/v% agarose and 0.5w/v% HA. Interestingly, when loaded dynamically (1-20Hz) this optimised formulation did not exhibit the highest complex modulus instead a sample with a higher concentration of mineral was identified (5.8w/v% agarose and 25w/v% HA). Thus, demonstrating the importance of examining the mechanical behaviour of biomaterials under conditions representative of physiological environments. While the complex moduli of the optimised gellan (1.0 ± 0.2MPa at 1Hz) and agarose (1.7 ± 0.2MPa at 1Hz) constructs did not match the complex moduli of healthy human cartilage samples (26.3 ± 6.5MPa at 1Hz), similar tan δ values were observed between 1 and 5Hz. This is promising since these frequencies represent the typical heel strike time of the general population. In summary, this study demonstrates the importance of considering more than just the strength of biomaterials since tissues like cartilage play a more complex role.

The use of drug-delivering implants can minimise implant failure due to infection through a controlled medication release into the surrounding tissues. In this study, selective laser melting (SLM) was employed to manufacture Ti-6Al-4 V samples, with internal reservoirs and releasing Micro-channels (MCs) to simulate what could be a drug-delivering orthopaedic or dental implant. Investigations were performed to optimise the design and SLM process parameters required to create the releasing MCs with minimum dimensional deviation to allow a controlled dosing of the drugs, while considering the process impact on the surface roughness and porosity of the builds. The build orientation, internal contour spacing, and laser process parameters were varied to assess their effect on the resolution of the MCs with diameters of ∼200–500 μm. It was found that, vertically oriented channels were found to have the least dimensional deviation from the target dimensions compared with horizontally-oriented or inclined channels. The dimensional deviation of the MCs was found in range of 220–427 μm, while the horizontal surface roughness (Ra) was in range of 1.46–11.46 μm and the vertical surface roughness (Ra) was in range of 8.5–13.23 μm when applying energy density varying from of 27–200 J/mm3. It was found that, there was a clear correlation between the energy density with both dimensional deviation and horizontal surface roughness, while no correlation was found for the vertical’ surface roughness. The study identified the optimum conditions to manufacture drug-delivering metallic implants, creating hollow samples with releasing MCs equivalent diameter of ∼271 μm, horizontal surface roughness (Ra) of 4.4 μm, vertical surface roughness of (Ra) 9.2 μm, and build porosity of 1.4% using an internal contour of 150 μm and energy density of 35.7 J/mm3.

Glaucoma is a leading cause of irreversible blindness globally, with primary open angle glaucoma (POAG) being the most common subset. Raised intraocular pressure is an important risk factor for POAG and is caused by a reduction in aqueous humour (AqH) outflow due to dysfunctional cellular and matrix dynamics in the eye’s main drainage site, the trabecular meshwork (TM) and Schlemm’s canal (SC). The TM/SC are highly specialised tissues that regulate AqH outflow; however, their exact mechanisms of AqH outflow control are still not fully understood. Emulating physiologically relevant 3D TM/S in vitro models poses challenges to accurately mimic the complex biophysical and biochemical cues that take place in healthy and glaucomatous TM/SC in vivo. With development of such models still in its infancy, there is a clear need for more well-defined approaches that will accurately contrast the two central regions that become dysfunctional in POAG; the juxtacanalicular tissue (JCT) region of the TM and inner wall endothelia of the Schlemm’s canal (eSC). This review will discuss the unique biological and biomechanical characteristics that are thought to influence AqH outflow and POAG progression. Further consideration into fundamental biomaterial attributes for the formation of a biomimetic POAG/AqH outflow model will also be explored for future success in pre-clinical drug discovery and disease translation.

This study reports the first fully synthetic fluid gel (SyMGels) using a simple poly(ethylene glycol) polymer. Fluid gels are an interesting class of materials: structured during gelation via shear-confinement to form microparticulate suspensions, through a bottom-up approach. Structuring in this way, when compared to first forming a gel and subsequently breaking it down, results in the formation of a particulate dispersion with particles “grown” in the shear flow. Resultantly, systems form a complex microstructure, where gelled particles concentrate remaining non-gelled polymer within the continuous phase, creating an amorphous-like interstitial phase. As such, these materials demonstrate mechanical characteristics typical of colloidal glasses, presenting solid-like behaviors at rest with defined yielding; likely through intrinsic particle-particle and particle-polymer interactions. To date, fluid gels have been fabricated using polysaccharides with relatively complex chemistries, making further modifications challenging. SyMGels are easily functionalised, using simple click-chemistry. This chemical flexibility, allows the creation of microenvironments with discrete biological decoration. Cellular control is demonstrated using MSC (mesenchymal stem cells)/chondrocytes and enables the regulation of key biomarkers such as aggrecan and SOX9. These potential therapeutic platforms demonstrate an important advancement in the biomaterial field, underpinning the mechanisms which drive their mechanical properties, and providing a versatile delivery system for advanced therapeutics.

Swelling, erosion, deformation and consolidation properties can affect the performance of cellulose ethers, the most commonly used matrix former in hydrophilic sustained tablet formulations. The present study was designed to comparatively evaluate the swelling, erosion, compression, compaction and relaxation properties of the cellulose ethers in a comprehensive study using standardised conditions. The interrelationship between various compressional models and the inherent deformation and consolidation properties of the polymers on the derived swelling and erosion parameters are consolidated. The impact of swelling (Kw) on erosion rates (KE) and the inter-relationship between Heckel and Kawakita plasticity constants was also investigated. It is evident from the findings that the increases in both substitution and polymer chain length led to higher Kw, but a lower KE; this was also true for all particle size fractions regardless of polymer grade. Smaller particle size and high substitution levels tend to increase the relative density of the matrix but reduce porosity, yield pressure (Py), Kawakita plasticity parameter (b-1) and elastic relaxation. Both KW vs KE (R2 = 0.949-0.980) and Py vs b-1 correlations (R2 = 0.820-0.934) were reasonably linear with regards to increasing hydroxypropyl substitution and molecular size. Hence, it can be concluded that the combined knowledge of swelling and erosion kinetics in tandem with the in and out-of-die compression findings can be used to select a specific polymer grade and further to develop and optimise formulations for oral controlled drug delivery applications.

Mica glass-ceramics usually have high melting temperatures. In this work, mica glass-ceramics were prepared by the combination of melting and powder metallurgy at low temperatures. Firstly, a SiO 2 -CaO-B 2 O 3 -MgO-Na 2 O-ZnO glass powder with a melting temperature as low as 1000 °C was prepared. Subsequently, the glass powder mixed with different contents of fluorphlogopite was remelted at 1300 °C to synthesize the ultimate glass frit. After disintegration, the mica glass-ceramic powder can be sintered at low temperatures of 800–950 °C, and a relative density as high as 90% can be obtained. The phase constitutions and microstructures of the bulk glass-ceramics were characterized by X-ray diffraction and scanning electron microscopy. The results illustrated that the glass-ceramics were mainly made up of flake-like fluormica and columnar nepheline, accompanied by augite, forsterite and some other minor phases. The transverse rupture strength and the hardness of mica glass-ceramics were both low at 800 °C for the high porosity, and decreased with the increase of mica phase at 850 °C. Nevertheless, the highest strength of the glass-ceramic with 30% mica reached 97.42 ± 10.2 MPa, which can be potentially applied for engineering applications.

Heterotopic ossification (HO) is a debilitating condition defined by the rapid formation of bone in soft tissues. What makes HO fascinating is firstly the rate at which bone is deposited, and secondly the fact that this bone is structurally and compositionally similar to that of a healthy adult. If the mechanisms governing HO are understood, they have the potential to be exploited for the development of potent osteoinductive therapies. With this aim, we utilised a tissue engineered skeletal muscle model to better understand the role of inflammation on this debilitating phenomenon. We showed myoblasts could be divided into two distinct populations, myogenic cells and undifferentiated "reserve" cells. Gene expression analysis of myogenic and osteo-regulatory markers confirmed that "reserve" cells were primed for osteogenic differentiation, but had a reduced capacity for myogenesis. Osteogenic differentiation was significantly enhanced in the presence of PDGF-BB and BMP2, and correlated with conversion to a Sca-1(+) /CD73(+) phenotype. Alizarin red staining showed that PDGF-BB promoted significantly more mineral deposition than BMP2. Finally, we showed that PDGF-induced mineralisation was blocked in the presence of the pro-inflammatory cytokines TNFα and IL1. In conclusion, the present study identified that PDGF-BB is a potent osteoinductive factor in a model of tissue engineered skeletal muscle, and that the osteogenic capacity of this protein was modulated in the presence of pro-inflammatory cytokines. These findings reveal a possible mechanism by which HO develops following trauma. Importantly, these findings have implications for the induction and control of bone formation for regenerative medicine.

Die wichtige Rolle von Vesikeln in vielen Bereichen der Zellfunktion ist gut bekannt, aber erst seit kurzem offenbart sich mithilfe neuer, komplexerer Bildgebungsverfahren ihre Allgegenwart in der Natur. Wahrend die biologischen Eigenschaften von Vesikeln und ihre physiologischen Funktionen immer besser verstanden werden, werden auch vermehrt sehr elegante, kunstliche Vesikel fur eine Reihe technischer Anwendungen und die Grundlagenforschung entwickelt. Hier wollen wir den Stand der Technik von biologischen und synthetischen Vesikeln darstellen und ihre biologischen Eigenschaften in Zusammenhang mit aktuellen Syntheseentwicklungen bringen, um so einen Uberblick uber diese komplexen, rasch aufstrebenden Fachgebiete zu geben. Daruber hinaus werden die Herausforderungen und Moglichkeiten fur die zukunftige biologische und praparative Entwicklung von Vesikeln prasentiert.

Sodium alginate was successfully utilized to improve cohesion and limit particulate debris of a premixed calcium phosphate cement (pCPC) that following the exchange of water set to form monetite. Modified pastes using glycerol and 2 wt% alginate exhibited initial and final setting times of 60 ± 9 and 1355 ± 105 minutes, respectively. Despite these setting times being significantly longer than clinically recommended the improved washout resistance of this formulation would allow for wound closure during setting. Set monetite pastes exhibited a maximum compressive strength of 8.6 ± 3.5 MPa with a corresponding porosity of 59% compared to 15.6 ± 5.8 MPa and 25% for the unmodified aqueous brushite cement. Storage of the pCPC paste at 4°C for 14 days was shown to significantly (P 20 mm did not reach full saturation after 10 days of immersion, which for the first time suggests an upper volume limit that will form a homogeneous cement highlighting an important consideration for clinical translation of pCPCs.

There were studied four types of powder filler materials for polyolefin composite parts production for automotive and aerospace industry. There was confirmed, that the particle shape has a strong effect on the acoustic and mechanical properties of the powder bed as influenced by the varying packing density. The calcium carbonate spherical hollow particles exhibited the best aerodynamic performance when aerated and were completely fluidised. Simultaneously they were exhibiting the easy flowing behaviour as reflected in the observed flowability of 4.71. In contrary to this, the flat lamellar geometry of the precipitated calcium carbonate resulted in the worst fluidisation behaviour, as the aeration energy was 2.5× higher in comparison to the spherical particles. Remaining samples under study, i.e. flash calcined kaolin and dolomite powder, exhibited cohesive rheological behaviour as reflected in the observed flowability. There was found a clear correlation between powder rheological and electrostatic charge data with the observed acoustic performance as reflected in the frequency dependence of the normal incident sound damping coefficient. This was demonstrated by a relatively high increase in the damping efficiency with increasing porosity of the powder bed as reflected in the decreasing packing density. However the best fit was found between the absolute value of the electrostatic charge values and the sound damping properties.

Precision medicine has been adopted in a range of clinical settings where omics data have led to greater characterisation of disease and stratification of patients into subcategories of phenotypes and pathologies. However, in orthopaedics, precision medicine lags behind other disciplines such as cancer. Joint registries have now amassed a huge body of data pertaining to implant performance which can be broken down into performance statistics for different material types in different cohorts of patients. The National Joint Registry of England, Wales and Northern Ireland (NJR) is now one of the largest datasets available. Other registries such as those from Sweden and Australia however contain longer follow-up. Together, these registries can provide a wealth of informative for the orthopaedics community when considering which implant to give to any particular patient. We aim to explore the benefits of combining multiple large data streams including joint registries, published data on osteoarthritis (OA) pathogenesis and pathology and data concerning performance of each implant material combination in terms of biocompatibility. We believe that this analysis will provide a comprehensive overview of implant performance hopefully aiding surgeons in making more informed choices about which implant should be used in which patient. Data from three joint registries were combined with established literature to highlight the heterogeneity of OA disease and the different clinical outcomes following arthroplasty with a range of material types. This review confirms that joint registries are unable to consider differences in arthritis presentation or underlying drivers of pathology. OA is now recognised to present with varying pathology with differing morbidity in different patient populations. Equally, just as OA is a heterogeneous disease, there are disparate responses to wear debris from different material combinations used in joint replacement surgery. This has been highlighted by recent high-profile scrutiny of early failure of metal-on-metal total hip replacement (THR) implants. Bringing together data from joint registries, biomarker analysis, phenotyping of OA patients and knowledge of how different patients respond to implant debris will lead to a truly personalised approach to treating OA patients, ensuring that the correct implant is given to the correct patient at the correct time.

Various injectable biomaterials are developed for the minimally invasive delivery of therapeutics. Typically, a mechanical tester is used to ascertain the force required to inject these biomaterials through a given syringe-needle system. However, currently there is no method to correlate the force measured in the laboratory to the perceived effort required to perform that injection by the end user. In this article, the injection force (F) for a variety of biomaterials, displaying a range of rheological properties, is compared with the effort scores from a 50 person panel study. The maximum injection force measured at crosshead speed 1 mm s-1 is a good proxy for injection effort, with an R2 of 0.89. This correlation leads to the following conclusions: participants can easily inject 5 mL of substance for F 64 N. These values may be used by developers of injectable biomaterials to make decisions about formulations and needle sizes early in the translational process.

Biological exposures to micro- and nano-scale exogenous metal particles generated as a consequence of in-service degradation of orthopaedic prosthetics can result in severe adverse tissues reactions. However, individual reactions are highly variable and are not easily predicted, due to in part a lack of understanding of the speciation of the metal-stimuli which dictates cellular interactions and toxicity. Investigating the chemistry of implant derived metallic particles in biological tissue samples is complicated by small feature sizes, low concentrations and often a heterogeneous speciation and distribution. These challenges were addressed by developing a multi-scale two-dimensional X-ray absorption spectroscopic (XAS) mapping approach to discriminate sub-micron changes in particulate chemistry within ex-vivo tissues associated with failed CoCrMo total hip replacements (THRs). As a result, in the context of THRs, we demonstrate much greater variation in Cr chemistry within tissues compared with previous reports. Cr compounds including phosphate, hydroxide, oxide, metal and organic complexes were observed and correlated with Co and Mo distributions. This variability may help explain the lack of agreement between biological responses observed in experimental exposure models and clinical outcomes. The multi-scale 2D XAS mapping approach presents an essential tool in discriminating the chemistry in dilute biological systems where speciation heterogeneity is expected. Significance: Metal implants are routinely used in healthcare but may fail following degradation in the body. Although specific implants can be identified as ‘high-risk’, our analysis of failures is limited by a lack of understanding of the chemistry of implant metals within the peri-prosthetic milieu. A new approach to identify the speciation and variability in speciation at sub-micron resolution, of dilute exogenous metals within biological tissues is reported; applied to understanding the failure of metallic (CoCrMo) total-hip-replacements widely used in orthopedic surgery. Much greater variation in Cr chemistry was observed compared with previous reports and included phosphate, hydroxide, oxide, metal and organic complexes. This variability may explain lack of agreement between biological responses observed in experimental exposure models and clinical outcomes.

Natural polymers have been widely used in a variety of biomedical applications such as pharmaceuticals, tissue regeneration scaffolds, drug delivery agents, and imaging agents. In wound care, they are used as dressings for acute or chronic wounds and as regeneration templates. Natural polymers can be derived from a wide variety of sources, from plants, animals, and microorganisms. Due to their similarity with the extracellular matrix, mechanical tunability, high biocompatibility, and high water holding capacity, natural polymers–based scaffolds are appealing for skin repair and regeneration purposes. A challenge for researchers is to select and modify the appropriate material for a scaffold that holds specific properties for the type of wound targeted. This chapter will discuss the desired properties of natural polymer–based acellular and cellular applications and currently available scaffolds for skin repair and regeneration, as well as give an overview of commonly used or promising natural polymers in wound healing.