Biomaterial Components Research Articles

Heat Transfer Modeling in Bone Tumour Hyperthermia Induced by Hydroxyapatite Magnetic Thermo-Seeds

Background: Hyperthermia is an adjuvant oncologic thermal therapy. In the case of deep-seated bone cancers, the interstitial hyperthermia treatment can be performed using thermo-seeds, implanted biomaterial components that are able to convert external electromagnetic power into thermal one. Several magnetic biomaterials have been synthesized for thermal treatments of cancer. However, less attention has been paid to the modeling description of the therapy, especially when the bio-heat transfer process is coupled to the electromagnetic heating. Objective: In this work, a comparison between the available analytical and numerical models is presented. Methods: A non-linear multiphysics model is used to study and describe the performance of cylindrical magnetic hydroxyapatite thermo-seeds to treat residual cancer cells of bone tumours. Results: The thermal dynamics and treatment outcome are carefully evaluated. Under the exposure of a magnetic field of 30 mT, working at 300 kHz, it was found that magnetic hydroxyapatite implants with a size of 10 mm × 10 mm could increase the temperature above 42 °C for 60 min. Conclusion: The proposed model overcomes the limitations of the available theoretical frameworks, and the results reveal the relevancy of the implant geometry to the effectiveness of the hyperthermia treatment.

Chemical Tuning of Fibers Drawn from Extensible Hyaluronic Acid Networks.

Polymer fibers with specific chemical and mechanical properties are key components of many biomaterials used for regenerative medicine and drug delivery. Here, we develop a bioinspired, low-energy process to produce mechanically tunable biopolymer fibers drawn from aqueous solutions. Hyaluronic acid (HA) forms dynamic cross-links with branched polyethylene glycol polymers end-functionalized with boronic acids of varied structure to produce extensible polymer networks. This dynamic fiber precursor (DFP) is directly drawn by pultrusion into HA fibers that display high aspect ratios, ranging from 4 to 20 μm in diameter and up to ∼10 m in length. Dynamic rheology measurements of the DFP and tensile testing of the resulting fibers reveal design considerations to tune the propensity for fiber formation and fiber mechanical properties, including the effect of polymer structure and concentration on elastic modulus, tensile strength, and ultimate strain. The materials' humidity-responsive contractile behavior, a unique property of spider silks rarely observed in synthetic materials, highlights possibilities for further biomimetic and stimulus-responsive fiber applications. This work demonstrates that chemical modification of dynamic interactions can be used to tune the mechanical properties of pultrusion-based fibers and their precursors.

Co-Immobilization of Ce6 Sono/Photosensitizer and Protonated Graphitic Carbon Nitride on PCL/Gelation Fibrous Scaffolds for Combined Sono-Photodynamic Cancer Therapy.

Aiming at developing a moderate and efficient sono-photodynamic therapy for breast cancer, tissue engineering scaffolds may provide an easy and efficient strategy to eliminate serious side effects in conventional surgery or chemotherapy, and thus, they are highly desired. However, the development of ideal sono-photodynamic therapeutic scaffolds is always hindered by the poor stability and incompatibility between the different biomaterial components. Herein, the Food and Drug Administration (FDA)-approved sono/photosensitizer Chlorin e6 (Ce6) was successfully and tightly incorporated into electrospun polycaprolactone/gelatin (PG) scaffolds via positively charged protonated g-C3N4 nanosheets (pCN). The PG fibers were precoated with graphene oxide (GO) to enable the assembly of pCN on the surface through electrostatic interactions. The Ce6@pCN-GO-PG composite scaffolds exhibited good cytocompatibility and excellent sono-photodynamic activity, leading to distinctly boosted reactive oxygen species (ROS) generation and a 95.8% inactivation rate of breast cancer cells through a synergistic sono-photodynamic process triggered by an 808 nm laser and 1 MHz ultrasound (US) excitation, within the clinical therapeutic dose. The as-developed scaffolds with unique ultrasound cavitation therapeutic effects can be used not only for complete eradication of tumor cells after surgery but also as a cell behavior observation platform of sono-photodynamic cancer therapy.

Elastic and biodegradable chitosan/agarose film revealing slightly acidic pH for potential applications in regenerative medicine as artificial skin graft

The aim of this work was to develop new method for the production of chitosan/agarose (CHN/A) film that could serve as a potential artificial skin substitute for regenerative medicine applications. Within this new production method, the concentrations of biomaterial components (chitosan in CH3COOH and agarose in NaOH) were optimized to provide neutralization of the resultant mixture up to pH approx. 6.0 without uncontrolled precipitation (gelation) of chitosan constituent. Produced thin film was subjected to comprehensive evaluation of its biomedical potential by determination of mechanical, physicochemical, and biological properties. It was demonstrated that the developed CHN/A film reveals slightly acidic pH of 5.98 known to support skin regeneration, high exudate absorption capacity, and is prone to biodegradation in simulated enzymatic wound environment. Performed tensile test proved high elastic deformations of the film (Young's modulus = 0.02 MPa, elongation at break = 23%) in a wet state, which would allow suitable stretching after application at the wound site. Moreover, novel biomaterial is non-toxic and supports fibroblast growth on its surface. Based on the obtained results it may be concluded that the produced CHN/A film possesses all necessary features of the artificial skin substitute.

In vitro effects of dental monomer exposure - Dependence on the cell culture model

Methacrylate monomers are major components of resin-based biomaterials. The polymerization of these materials is never complete, and methacrylates leaking from cured materials cause exposure of patients. Only some selected methacrylates have thoroughly been tested for possible interaction with living cells. In the current study, we compared the effects of 2-hydroxyethyl-methacrylate (HEMA; a carefully studied methacrylate) and hydroxypropyl-methacrylate (HPMA; a scarcely investigated methacrylate). Five cell lines differing in both source and cell type were used.The cells were exposed to methacrylates (1–8 mM). Cell viability, cell death, glutathione levels, reactive oxygen species (ROS), and cell growth pattern were measured.Both methacrylates reduced cell viability, and glutathione depletion was observed in all cell lines. The cell death pattern varied among the cell lines. The ROS levels and cell growth pattern also differed between the cell lines after exposure to methacrylate monomers. No difference between HEMA and HPMA exposures were observed in any of the cell lines.The variation between cell lines shows that the measured methacrylate toxicity depends heavily on the test system chosen. Further, the conformity between HEMA and HPMA effects suggests that the two methacrylates similarly affect living cells.

Self-healing injectable gelatin hydrogels for localized therapeutic cell delivery.

Self-healing injectable hydrogel biomaterials uniquely enable precise therapeutic deposition and deployment at specific bodily locations through versatile and minimally invasive processes that can preserve cargo integrity and cell viability. Despite the distinct advantages that injectable hydrogels offer in tissue engineering and therapeutic delivery, exceptionally few have been created using components naturally present in the cellular niche. In this work, we introduce a shear-thinning hydrogel based on guest-host complexation of gelatin. As a biocompatible, biodegradable, and nonimmunogenic biopolymer derived from the most abundant extracellular matrix protein (collagen), gelatin offers great utility as the structural component of biomaterials. Taking advantage of reversible guest-host interactions between β-cyclodextrin (CD) and adamantane (AD) on modified gelatins, we report the first strategy to afford a self-healing material based solely on a functionalized extracellular matrix protein. By varying the initial material formulation, hydrogels were synthesized with variable moduli and shear-thinability across a broad range. Gels were demonstrated to exhibit shear-thinning and self-healing properties, supporting protection of clinically relevant stem-cell-derived cardiomyocytes during injection. These materials are expected to expand clinical opportunities in cell delivery for in vivo tissue regeneration.

Impact of Varied Factors on Iron, Nickel, Molybdenum and Vanadium Concentrations in the Knee Joint.

The aim of this study was to determine the concentrations of iron, nickel, molybdenum, and vanadium in the knee joint. We also examined the relationships between the concentrations of these metals in the knee joint and the influence of varied factors on the concentration of Fe, Ni, Mo, and V. The study of these trace elements is important, because these elements are used alone and in combination in diet supplements, and they are components of biomaterials implanted in medicine. The study materials, consisting of the spongy bone, cartilage, meniscus, anterior cruciate ligament (ACL), and infrapatellar fat pad, were obtained from 34 women and 12 men from northwestern Poland. The concentrations of Ni, Fe, Mo, and V were determined using spectrophotometric atomic absorption in inductively coupled argon plasma (ICP-AES). We found significantly higher Mo concentrations in the ACL of women than men. There was a significant difference in the Mo concentration in the spongy bone between patients from cities with fewer than 100,000 inhabitants and patients from cities with more than 100,000 residents. Iron concentrations in the spongy bone were higher in non-smoking patients and those who did not consume alcohol. Vanadium concentrations were higher in the infrapatellar fat pads in abstainers. In patients who had not undergone arthroscopy surgery, V concentration was lower in cartilage. The concentrations of V in the cartilage and infrapatellar fat pad were higher in osteoporotic patients than in non-osteoporotic patients. There were significant differences in Fe concentrations in the meniscus, with the lowest in osteoporotic patients. We noted lower Mo concentrations in the spongy bone of patients with rheumatoid arthritis. Furthermore, we noted some new interactions among metals in the studied structures of the knee joint. The results reported in this study show the influence of gender, place of residence, smoking, consumption of alcohol, arthroscopy surgery, osteoporosis, and rheumatoid arthritis on the Fe, Ni, Mo, and V concentrations in the studied structures of the knee joint.

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers.

Tough mechanical properties are generally required for tissue substitutes used in regeneration of damaged tissue, as these substitutes must be able to withstand the external physical force caused by stretching. Gelatin, a biopolymer derived from collagen, is a biocompatible and cell adhesive material, and is thus widely utilized as a component of biomaterials. However, the application of gelatin hydrogels as a tissue substitute is limited owing to their insufficient mechanical properties. Chemical cross-linking is a promising method to improve the mechanical properties of hydrogels. We examined the potential of the chemical cross-linking of gelatin hydrogels with carboxy-group-modified polyrotaxanes (PRXs), a supramolecular polymer comprising a poly(ethylene glycol) chain threaded into the cavity of α-cyclodextrins (α-CDs), to improve mechanical properties such as stretchability and toughness. Cross-linking gelatin hydrogels with threading α-CDs in PRXs could allow for freely mobile cross-linking points to potentially improve the mechanical properties. Indeed, the stretchability and toughness of gelatin hydrogels cross-linked with PRXs were slightly higher than those of the hydrogels with the conventional chemical cross-linkers 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS). In addition, the hysteresis loss of gelatin hydrogels cross-linked with PRXs after repeated stretching and relaxation cycles in a hydrated state was remarkably improved in comparison with that of conventional cross-linked hydrogels. It is considered that the freely mobile cross-linking points of gelatin hydrogels cross-linked with PRXs attenuates the stress concentration. Accordingly, gelatin hydrogels cross-linked with PRXs would provide excellent mechanical properties as biocompatible tissue substitutes exposed to a continuous external physical force.

Stretched, mangled, and torn: Responses of the Ediacaran fossil Dickinsonia to variable forces

AbstractDickinsonia is one of the oldest macroscopic metazoans in the fossil record. Determining the biological characters of this extinct taxon is critical to our understanding of the early evolution of life. Preservation of abundant specimens from the Ediacara Member (Rawnsley Quartzite), South Australia, in a variety of taphonomic states allows the unparalleled opportunity to compare the biomechanical responses of Dickinsonia tissue to various forces with those typical of modern organisms. Dickinsonia are found as lifted, transported, folded, rolled, ripped, and expanded or contracted individuals, while maintaining diagnostic morphology. This suite of characters indicates that Dickinsonia was composed of material that was flexible, difficult to rip, and capable of elastic and plastic deformation. While none of these traits are diagnostic of a single biomaterial component, we find many similarities with modern biopolymers, particularly collagen, keratin, and elastin. Maintenance of significant relief following complete tearing suggests that Dickinsonia was composed of relatively thick tissues, signifying higher oxygen requirements than previously hypothesized. The ability to be transported and still be preserved as recognizable fossils is unique amongst the Ediacara Biota and demonstrates that Dickinsonia was a taphonomic elite. Combined with discovery in multiple environmental settings, this indicates that the absence of Dickinsonia represents the likely extinction of this organism prior to the Nama assemblage, possibly due to a decrease in the global availability of oxygen in the latest Ediacaran.

Titanium coated with poly(lactic-co-glycolic) acid incorporating simvastatin: Biofunctionalization of dental prosthetic abutments.

To propose a biofunctionalized prosthetic abutment by analyzing physico-chemical and morphological properties, simvastatin (SIM) release, and biocompatibility of titanium (Ti) disks coated with poly(lactic-co-glycolic) acid (PLGA) incorporating SIM. Titanium disks (8×3mm) were distributed into four groups: Ti: pure Ti; Ti+PLGA: Ti coated with PLGA; Ti+PLGA+SIM6%: Ti+PLGA with 6% SIM; and Ti+PLGA+SIM0.6%: Ti+PLGA incorporating 0.6% SIM. PLGA was prepared through chloroform evaporation technique. After complete dissolution of PLGA, SIM was diluted in the solution. Ti+PLGA, Ti+PLGA+SIM6%, and Ti+PLGA+SIM0.6% were dip coated with PLGA and PLGA+SIM, respectively. Samples were sterilized by ethylene oxide. For SIM release assay, disks were submerged in PBS, pH 7.4, 37°C, 30rpm up to 600hours. At different time intervals, SIM was quantified by spectrophotometry (238nm). For characterization of the biomaterial components, it was performed Fourier-transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy (SEM), optical profilometry, and atomic force microscopy. Biocompatibility analyses were performed by MTS colorimetric assay on murine fibroblasts L929, human gingival fibroblasts (HGFs), and stem cells from human exfoliated deciduous teeth (SHEDs). Absorbance was measured at 490nm, and percentages of viable cells were calculated in relation to positive control (Ti). SEM images were obtained to verify cell adhesion and morphology. One-way ANOVA followed by Tukey's post hoc test was applied (P<0.05) for statistical analyses. SIM release was slow and continuous, reaching about 21% of the incorporated SIM after 600hours. Topographical analyses revealed success in coating Ti disks with PLGA incorporating SIM. Regarding biocompatibility test, Ti+PLGA+SIM0.6% showed the highest percentage of L929 viability at days 3 and 7. There was no significant difference for Ti, Ti+PLGA, and Ti+PLGA+SIM0.6% groups on cell viability of both SHEDs and HGFs at days 3 and 7. SEM corroborates that SHEDs and HGFs were able to adhere and proliferate on Ti, Ti+PLGA, and Ti+PLGA+SIM0.6% surfaces. A slow and controlled release of SIM was achieved, attributed to a diffusional mass transfer mechanism. Moreover, a homogenous coating topography was obtained. Additionally, 0.6% SIM incorporated into PLGA coating improved fibroblasts L929 viability compared to titanium or PLGA. Also, 0.6% SIM incorporated into PLGA promoted cell viability of about 100% for HGFs and approximately 150% for human mesenchymal stem cells. Therefore, this study allows to consider the use of PLGA-coated titanium incorporating SIM as a biofunctionalized abutment for dental implants.

Adsorption of Phospholipids at the Air-Water Surface

Phospholipids are ubiquitous components of biomembranes and common biomaterials used in many bioengineering applications. Understanding adsorption of phospholipids at the air-water surface plays an important role in the study of pulmonary surfactants and cell membranes. To date, however, the biophysical mechanisms of phospholipid adsorption are still unknown. It is challenging to reveal the molecular structure of adsorbed phospholipid films. Using combined experiments with constrained drop surfactometry and molecular dynamics simulations, here, we studied the biophysical mechanisms of dipalmitoylphosphatidylcholine (DPPC) adsorption at the air-water surface. It was found that the DPPC film adsorbed from vesicles showed distinct equilibrium surface tensions from the DPPC monolayer spread via organic solvents. Our simulations revealed that only the outer leaflet of the DPPC vesicle is capable of unzipping and spreading at the air-water surface, whereas the inner leaflet remains intact and forms an inverted micelle to the interfacial monolayer. This inverted micelle increases the local curvature of the monolayer, thus leading to a loosely packed monolayer at the air-water surface and hence a higher equilibrium surface tension. These findings provide novel insights, to our knowledge, into the mechanism of the phospholipid and pulmonary surfactant adsorption and may help understand the structure-function correlation in biomembranes.

Langmuir-Blodgett films of membrane lipid in the presence of hybrid silsesquioxane, a promising component of biomaterials.

Functionalized polyhedral oligomeric silsesquioxanes (POSS) derivatives have great potential in biomedical applications such as tissue engineering, drug delivery, biosensors, dental composites and biomedical devices. Having the above in mind, in this paper, the study of the surface characteristics of binary Langmuir-Blodgett films consisting of an open cage silsesquioxane POSS-poly (ethylene glycol) (POSS-PEG) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), as a representative of phospholipid was conducted based on contact angle measurements of three liquids. The measured values of the contact angle (with water, formamide and diiodomethane as the wetting liquids) allowed to calculate surface free energy of the films from van Oss et al. approach. The film structure of the deposited layers was evaluated using an atomic force microscope. Analysis of the obtained results led to the conclusion, that the pure DMPE molecules create agglomerates onto a solid substrate, whereas the POSS-PEG molecules form a homogenous monolayer. After an addition of POSS-PEG to lipid film, changes in the surface properties are visible. The wettability as well as surface free energy depend on the molar ratio of both components. The AFM images shed more light on the changes of the DMPE monolayer topography caused by the POSS-PEG addition.

Screening of perfused combinatorial 3D microenvironments for cell culture

Biomaterials combining biochemical and biophysical cues to establish close-to-extracellular matrix (ECM) models have been explored for cell expansion and differentiation purposes. Multivariate arrays are used as material-saving and rapid-to-analyze platforms, which enable selecting hit-spotted formulations targeting specific cellular responses. However, these systems often lack the ability to emulate dynamic mechanical aspects that occur in specific biological milieus and affect physiological phenomena including stem cells differentiation, tumor progression, or matrix modulation. We report a tailor-made strategy to address the combined effect of flow and biochemical composition of three-dimensional (3D) biomaterials on cellular response. We suggest a simple-to-implement device comprising (i) a perforated platform accommodating miniaturized 3D biomaterials and (ii) a bioreactor that enables the incorporation of the biomaterial-containing array into a disposable perfusion chamber. The system was upscaled to parallelizable setups, increasing the number of analyzed platforms per independent experiment. As a proof-of-concept, porous chitosan scaffolds with 1 mm diameter were functionalized with combinations of 5 ECM and cell-cell contact-mediating proteins, relevant for bone and dental regeneration, corresponding to 32 protein combinatorial formulations. Mesenchymal stem cells adhesion and production of an early osteogenic marker were assessed on-chip on static and under-flow dynamic perfusion conditions. Different hit-spotted biomaterial formulations were detected for the different flow regimes using direct image analysis. Cell-binding proteins still poorly explored as biomaterials components – amelogenin and E-cadherin – were here shown as relevant cell response modulators. Their combination with ECM cell-binding proteins – fibronectin, vitronectin, and type 1 collagen – rendered specific biomaterial combinations with high cell adhesion and ALP production under flow. The developed versatile system may be targeted at widespread tissue regeneration applications, and as a disease model/drug screening platform. Statement of SignificanceA perfusion system that enables cell culture in arrays of three-dimensional biomaterials under dynamic flow is reported. The effect of 31 cell-binding protein combinations in the adhesion and alkaline phosphatase (ALP) production of mesenchymal stem cells was assessed using a single bioreactor chamber. Flow perfusion was not only assessed as a classical enhancer/accelerator of cell growth and early osteogenic differentiation. We hypothesized that flow may affect cell-protein interactions, and that key components driving cell response may differ under static or dynamic regimes. Indeed, hit-spotted formulations that elicited highest cell attachment and ALP production on static cell culture differed from the ones detected for dynamic flow assays. The impacting role of poorly studied proteins as E-cadherin and amelogenin as biomaterial components was highlighted.

Citric acid modification of a polymer exhibits antioxidant and anti-inflammatory properties in stem cells and tissues.

Biomaterials can be used as carriers of antioxidant or drug to the oxidative injury site of tissue and decrease intracellular oxidative stress levels, however, low dosage delivery or unstable molecular structure of antioxidant or drug limited the long-term sustained release. A chemically stable antioxidant molecule is essential to serve as antioxidant structure components of biomaterials that may provide the relatively high antioxidant content and persisting local antioxidant release with the degradation of materials. In this study, we used citric acid modified polyvinyl alcohol (PVA-C) as a model biomaterial to investigate the role of citric acid on the material stimulated antioxidant and anti-inflammatory effects. In cellular-based assays, PVA-C extracts showed a protective effects on bone marrow mesenchymal stem cells (BMSCs) under oxidative stress. It could enhance the antiapoptotic ability of stem cells by inhibiting reactive oxygen species. Further studies revealed that PVA-C extracts upregulated the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) and superoxide dismutase [Mn] (SOD2). in vivo animal assays, PVA-C extracts showed significant inhibitory effects on the oxidative stress and inflammatory reaction which were induced by lipopolysaccharide (LPS). These findings suggest that the citric acid modified polymer can regulate the redox signaling of stem cells and tissues by the release of citric acid from materials, leading to enhanced oxidative stress-induced degenerative diseases and inflammatory diseases therapy.

3D Strain and Elasticity Measurement of Layered Biomaterials by Optical Coherence Elastography based on Digital Volume Correlation and Virtual Fields Method

The three-dimensional (3D) mechanical property characterization of biological tissues is essential for physiological and pathological studies. A digital volume correlation (DVC) and virtual fields method (VFM) based 3D optical coherence elastography (OCE) method is developed to quantitatively measure the 3D full-field displacements, strains and elastic parameters of layered biomaterials assuming the isotropy and homogeneity of each layer. The integrated noise-insensitive DVC method can obtain the 3D strain tensor with an accuracy of 10%. Automatic segmentation of the layered materials is realized based on the full field strain and strain gradient. With the strain tensor as input, and in combination with the segmented geometry, the Young’s modulus and Poison’s ratio of each layer of a double-layered material and a pork specimen are obtained by the VFM. This study provides a powerful experimental method for the differentiation of various components of heterogeneous biomaterials, and for the measurement of biomechanics.

Oligosaccharides Self-Assemble and Show Intrinsic Optical Properties.

Self-assembling peptides and oligonucleotides have given rise to synthetic materials with several applications in nanotechnology. Aggregation of synthetic oligosaccharides into well-defined architectures has not been reported even though natural polysaccharides, such as cellulose and chitin, are key structural components of biomaterials. Here, we report that six synthetic oligosaccharides, ranging from dimers to hexamers, self-assemble into nanostructures of varying morphologies and emit within the visible spectrum in an excitation-dependent manner. Well-defined differences in chain length, monomer modification, and aggregation methods yield glycomaterials with distinct shapes and properties. The excitation-dependent fluorescence in a broad range within the visible spectrum illustrates their potential for use in optical devices and imaging applications. We anticipate that our systematic approach of studying well-defined synthetic oligosaccharides will form the foundation of our understanding of carbohydrate interactions in nature.

Marine Polysaccharide-Collagen Coatings on Ti6Al4V Alloy Formed by Self-Assembly.

Polysaccharides of marine origin are gaining interest as biomaterial components. Bacteria derived from deep-sea hydrothermal vents can produce sulfated exopolysaccharides (EPS), which can influence cell behavior. The use of such polysaccharides as components of organic, collagen fibril-based coatings on biomaterial surfaces remains unexplored. In this study, collagen fibril coatings enriched with HE800 and GY785 EPS derivatives were deposited on titanium alloy (Ti6Al4V) scaffolds produced by rapid prototyping and subjected to physicochemical and cell biological characterization. Coatings were formed by a self-assembly process whereby polysaccharides were added to acidic collagen molecule solution, followed by neutralization to induced self-assembly of collagen fibrils. Fibril formation resulted in collagen hydrogel formation. Hydrogels formed directly on Ti6Al4V surfaces, and fibrils adsorbed onto the surface. Scanning electron microscopy (SEM) analysis of collagen fibril coatings revealed association of polysaccharides with fibrils. Cell biological characterization revealed good cell adhesion and growth on bare Ti6Al4V surfaces, as well as coatings of collagen fibrils only and collagen fibrils enhanced with HE800 and GY785 EPS derivatives. Hence, the use of both EPS derivatives as coating components is feasible. Further work should focus on cell differentiation.

Mineralization of gellan gum hydrogels with calcium and magnesium carbonates by alternate soaking in solutions of calcium/magnesium and carbonate ion solutions.

Mineralization of hydrogels is desirable prior to applications in bone regeneration. CaCO3 is a widely used bone regeneration material, and Mg, when used as a component of calcium phosphate biomaterials, has promoted bone-forming cell adhesion and proliferation and bone regeneration. In this study, gellan gum hydrogels were mineralized with carbonates containing different amounts of calcium (Ca) and magnesium (Mg) by alternate soaking in, firstly, a calcium and/or magnesium ion solution and, secondly, a carbonate ion solution. This alternate soaking cycle was repeated five times. Five different calcium and/or magnesium ion solutions, containing different molar ratios of Ca to Mg ranging from Mg free to Ca free were compared. Carbonate mineral formed in all sample groups subjected to the alternate soaking cycle. Ca : Mg elemental ratio in the mineral formed was higher than in the respective mineralizing solution. Mineral formed in the absence of Mg was predominantly CaCO3 in the form of a mixture of calcite and vaterite. Increasing the Mg content in the mineral formed led to the formation of magnesian calcite and decreased the total amount of the mineral formed and its crystallinity. Hydrogel mineralization and increasing Mg content in mineral formed did not obviously improve proliferation of MC3T3-E1 osteoblast-like cells or differentiation after 7days.

Hyperspectral chemical imaging reveals spatially varied degradation of polycarbonate urethane (PCU) biomaterials

Hyperspectral chemical imaging (HCI) is an emerging technique which combines spectroscopy with imaging. Unlike traditional point spectroscopy, which is used in the majority of polymer biomaterial degradation studies, HCI enables the acquisition of spatially localised spectra across the surface of a material in an objective manner. Here, we demonstrate that attenuated total reflectance Fourier transform infra-red (ATR-FTIR) HCI reveals spatial variation in the degradation of implantable polycarbonate urethane (PCU) biomaterials. It is also shown that HCI can detect possible defects in biomaterial formulation or specimen production; these spatially resolved images reveal regional or scattered spatial heterogeneity. Further, we demonstrate a map sampling method, which can be used in time-sensitive scenarios, allowing for the investigation of degradation across a larger component or component area. Unlike imaging, mapping does not produce a contiguous image, yet grants an insight into the spatial heterogeneity of the biomaterial across a larger area. These novel applications of HCI demonstrate its ability to assist in the detection of defective manufacturing components and lead to a deeper understanding of how a biomaterial’s chemical structure changes due to implantation. Statement of significanceThe human body is an aggressive environment for implantable devices and their biomaterial components. Polycarbonate urethane (PCU) biomaterials in particular were investigated in this study. Traditionally one or a few points on the PCU surface are analysed using ATR-FTIR spectroscopy. However the selection of acquisition points is susceptible to operator bias and critical information can be lost. This study utilises hyperspectral chemical imaging (HCI) to demonstrate that the degradation of a biomaterial varies spatially. Further, HCI revealed spatial variations of biomaterials that were not subjected to oxidative degradation leading to the possibility of HCI being used in the assessment of biomaterial formulation and/or component production.

Advanced Functional Materials Solutions to Engineering the Neural Interface

Advanced Functional Materials Solutions to Engineering the Neural Interface