Biomaterials Advances

Multiple Sclerosis (MS) is a chronic, inflammatory disease of the central nervous system. Despite the pharmacological arsenal approved for MS, there are treatment-reluctant patients for whom cell therapy appears as the only therapeutic alternative. Myeloid-derived suppressor cells (MDSCs) are immature cells of the innate immune response able to immunosuppress T lymphocytes and to promote oligodendroglial differentiation in experimental autoimmune encephalomyelitis (EAE), a preclinical model for MS. Culture devices need to be designed so that MDSCs maintain a state of immaturity and immunosuppressive function similar to that exerted in the donor organism. Graphene oxide (GO) has been described as a biocompatible material with the capacity to biologically modulate different cell types, including immune cells. In the present work, we show how MDSCs isolated from immune organs of EAE mice maintain an immature phenotype and highly immunosuppressive activity on T lymphocytes after being cultured on 2D reduced GO films (rGO200) compared to those grown on glass. This activity is depleted when MDSCs are exposed to slightly rougher and more oxidized GO substrates (rGO90). The greater reduction in cell size of cells exposed to rGO90 compared to rGO200 is associated with the activation of apoptosis processes. Taken together, the exposure of MDSCs to GO substrates with different redox state and roughness appears as a good strategy to control MDSC activity in vitro. This versatility of GO nanomaterials and the impact of their physico-chemical properties in immunomodulation open the door to its possible selective therapeutic use for pathologies where MDSCs need to be enhanced or inhibited.

Oral diseases represent a significant public health challenge, particularly periodontal and peri-implant diseases that result in considerable bone loss and diminished quality of life. To address these issues, tissue engineering techniques such as guided bone regeneration (GBR) utilize barrier membranes to promote bone defect healing. This study introduces a novel membrane employing Ganoderma sessile mycelium as a microstructural director for osteogenic biomaterials, achieving a mycelium-alginate-nanohydroxyapatite (My-ALG-HA) composite. This innovative strategy addresses the limitations of conventional biomaterials, including inadequate management of chewing forces, limited blood supply and microbial contamination. This approach uses the unique hierarchical structure and hydrophobic properties of Ganoderma mycelium alongside the biocompatibility and hydrophilicity of the ALG-HA system to improve the structural integrity and biological functionality. The mycelium colonizes the ALG-HA substrate, forming a porous trabecular bone-like network. Water contact angle assays indicated an anisotropic interaction behavior, and tensile testing confirmed the material ductility. Incorporating mycelium-derived molecules contributes to its hydrophobicity and resistance to degradation in simulated physiological conditions. Additionally, the My-ALG-HA biomaterial demonstrates human blood hemocompatibility and osteoblast-like cell (MC3T3-E1) cytocompatibility, highlighting its potential as an advanced solution for bone tissue regeneration in regenerative medicine.

In this work, we studied the generation and rising of polyploid cancer cells as a product of mechanical stress. To this purpose, MCF7 breast cancer cells were cultured on 2D (i.e. flasks, or flat hydrogels), and in 3D milieus (i.e. Spheroids, or immobilized within alginate-gelatin microbeads, named in this work as tumor-like microcapsules), and further analyzed by biophysical and genetic methods (i.e. single-cell Traction Force Microscopy and RNA-seq respectively). Our results show that MCF7 cells preconditioned onto 2D surfaces exhibit a low number of polynucleated cells, while their culture in 3D environments triggered their progressive generation with time. Genetic studies enabled us to determine that polyploid cells found in tumor-like microcapsules are likely originated by cell-cell fusion and disrupted cytokinesis, showing most of the genetic markers for Polyploid Giant Cancer Cell, while cells cultured as spheroids seem to be likely generated by other mechanisms, such as cell cannibalisms, entosis, or emperipolesis. Our outcomes strongly suggest that both mechanical stress and confinement are required to stimulate cell polyploidy, which can be easily addressed by the immobilization of breast cancer cells in tumor-like microcapsules.

In tissue engineering, it is important to conceive and construct artificial bio-mimetic scaffolds able to foster cell migration as this is a fundamental process in wound healing and tissue regeneration. In order to do that, cubically symmetric and triply periodic porous structures have been identified as promising candidates for instance for the reconstruction of artificial cartilages and bones, also due to their tunable mechanical characteristics and highly inter-connected porous architectures that mimic the trabecular bone hyperboloidal topography. We propose here a mathematical approach that might be helpful to identify what are the best geometrical characteristics of such scaffolds, in order to promote cell migration into the porous structures and speed-up their re-population. The method is based on the observation that cell nucleus deformations should be avoided, yet assuring a good possibility for the cell to reach the wall of the porous structure. Mathematically speaking, this leads to the problem of identifying the size of the largest sphere that can pass, without being stuck, through the pores of the bio-mimetic scaffold.

Cells can respond to the physical stimulus that comes from their micro-environments. There are several strategies to alter cell behavior. Several tissues like bone and cartilage, which are the point of interest of regenerative medicine, are under significant degrees of mechanical stress in real life. Within this stress, the arising mechanotransduction effect may trigger several behavioral responses on cells. As a novel and efficient way, magnetic nanoparticles can be used to make such a mechanotransductive effect on cells. In this study, pre-functionalized Fe3O4 superparamagnetic magnetite nanoparticles were synthesized and used to fabricate gelatin-based magnetic cryogels. Cell growth, tissue-specific metabolic activities, differentiation potential to the bone, and cartilage under static magnetic field at different magnetic field strength (1000-4000G) were investigated. Results indicated that there was a better induction in considerable higher magnetic field among all others and magnetic cryogels helps to mediate mesenchymal stem cell behaviour, promote their growth and induce osteogenic and chondrogenic differentiation.

Although silicon is a widespread constituent in dental materials, its possible influence on teeth formation and repair remains largely unexplored. Here we have studied the effect of two silicic acid-releasing nanomaterials, silica and bioglass, on a living model of pulp consisting of dental pulp stem cells seeded in dense type I collagen hydrogels. Silica nanoparticles and released silicic acid had little effect on cell viability and mineralization efficiency but impacted metabolic activity, delayed matrix remodeling and led to heterogeneous cell distribution. Bioglass improved cell metabolic activity and led to a homogenous dispersion of cells and mineral deposits within the scaffold. These results suggest that the presence of calcium ions in bioglass is not only favorable to cell proliferation but can also counter-balance the negative effects of silica and silicic acid. Both chemical and biological processes should therefore be considered when investigating the effect of silicon-containing materials on dental tissues.

Traumatic dental injury impacts approximately 1 in 10 people globally and it is further challenging to treat with the complications such as inflammation, infection and dynamic oral pH which collectively slow down the dental bone healing. Currently existing approaches address these complications individually which results in suboptimal regenerative outcomes. Our study focuses on developing a multifunctional dental scaffold engineered to tackle inflammation and infection simultaneously and enhance bone regeneration through a dual drug delivery strategy and integration of Bioglass. A novel citric acid mediated process was used to produce bioglass which was further characterized using XRD and SEM analyses. The bioglass was capped with antibiotic and integrated into the alginate scaffold which was further subjected to surface coating of painkiller to enable rapid anti-inflammatory action and sustained antimicrobial release. The composite scaffold was further assessed for its physiochemical properties using swelling and degradation analysis, SEM was carried out to understand the structure and morphology of the scaffold. MTT assays were carried out on osteoblastic and fibroblastic cell lines to understand the cytocompatibility of the scaffold, while the osteogenic property was evaluated through biomineralization assay. The results showed successful synthesis and homogenous integration of bioglass, leading to increased swelling potential, controlled degradation and excellent biocompatibility. Robust osteogenic differentiation validated the scaffolds capacity as an advanced platform for dental bone tissue engineering and effective management of traumatic dental injuries. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/698929v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@6b7ed8org.highwire.dtl.DTLVardef@154b0c4org.highwire.dtl.DTLVardef@1212c22org.highwire.dtl.DTLVardef@d89dff_HPS_FORMAT_FIGEXP M_FIG C_FIG

ObjectiveRegenerative endodontics procedures show promise in treating immature teeth with necrotic pulp and apical periodontitis. This procedure involves the replacement of damaged and infected pulp tissue with viable tissue that restores the normal tooth structure and function. Antimicrobials are currently used to control the infection; however, they are cytotoxic to stem cells of the apical papilla (SCAP) and can lead to root canal calcification. Management of these teeth requires a scaffold that can control root canal infection, wick the blood into the canal, and support the viability and differentiation of SCAP while inhibiting intracanal calcification. This study aims to develop a composite scaffold made of polyphosphate, a calcium binding inorganic polymer shown to promote cell proliferation and tissue regeneration, chitosan, a natural antimicrobial polymer that supports stem cell viability and activity, and copper, a metal ion with bactericidal properties. MethodologyThe scaffold was prepared by adding copper (Cu) to chitosan solution, followed by polyphosphate. The resulting scaffold was then freeze-dried and analyzed for elemental composition, chemical structure, release of Cu, antibacterial properties, cytotoxicity, as well as differentiation and mineralization assays. Data were analysed by a two-way analysis of variance (ANOVA) followed by the Tukey post hoc test. ResultThis study demonstrates that, by combining polyphosphate and chitosan, we could fabricate a scaffold that inhibits bacterial growth by 40 % and supports the viability of fibroblast and SCAP. Adding copper to this scaffold further increased bacterial growth inhibition by up to 68% while preserving cell viability. The immunocytochemistry and Alizarin Red staining revealed that this scaffold also supports the odontogenic differentiation of these stem cells while inhibiting their mineralization potential. Furthermore, this scaffold can be fabricated as a 3D cone-shaped scaffold with a strong vertical wicking ability at a rate of 0.5 mm/s and excellent degradability, with 53 % of the scaffold degraded after 28 days. ConclusionsThis study shows that a copper-loaded chitosan-polyphosphate scaffold combines biocompatibility, antibacterial activity, wicking ability, and biodegradability and has great potential as an endodontic regenerative scaffold.

Analyzing the differentiation potential of cells in contact with newly developed materials is essential for assessing their ability to integrate into biological tissues and promote functional regeneration. Material properties such as rigidity, topography, and wettability significantly influence stem cell differentiation and are therefore optimized in implants. In this context, surface potential has been repeatedly, albeit inadvertently, shown to enhance osteogenesis. Here, we demonstrate that this surface property modulates cellular mechanosensing by altering the cells perception of substrate rigidity. Specifically, we show that human bone marrow-derived mesenchymal stem cells (hBM-MSCs) on surfaces with a net zero charge, coated with collagen type I, exhibit characteristics typical of cells adhering to compliant substrates. Conversely, mesenchymal stem cells on polarized surfaces activate mechanoresponsive pathways that promote osteogenesis, as evidenced by large spreading areas, enhanced contractility, and Yes-associated protein (YAP) translocation into the nucleus. Furthermore, our data suggest that negative net surface potentials lead to the local accumulation of calcium ions, which further facilitates osteogenic differentiation. Collectively, our findings reveal that biomaterials surface potential, a previously uncharacterized mediator of cellular mechanotransduction, should be considered in the design of next-generation biomaterials for tissue regeneration applications.

Bone disorders represent a significant global health challenge. Extracellular vesicles (EVs) are emerging as a promising nanotherapeutic approach for bone regeneration, addressing the translation barriers associated with cell-based therapies. Despite their immense potential, the clinical application of EVs is limited by low production yields and inconsistent quality. Magnetic Ion Channel Activation (MICA) utilises remote magnetic fields to stimulate mechano-sensitive ion channels through magnetic nanoparticles (MNPs). This study explores the potential of utilising MICA to enhance the production yield and therapeutic efficacy of EVs for bone regeneration. The findings demonstrate that MICA significantly increased the production yield of EVs from MC3T3 pre-osteoblasts compared to magnetic stimulation or TREK1 functionalised graphene oxide-MNP particles alone. The obtained EVs exhibited typical size distribution, morphology, and EV protein expression consistent with nano-sized vesicles. Furthermore, MICA/TREK EVs treatment considerably enhanced human bone marrow-derived mesenchymal stem cells osteogenic differentiation and mineralisation compared to EVs derived from MICA, TREK, or untreated groups. Proteomics analysis revealed the enrichment of proteins involved in mechanotransduction and osteogenic differentiation within MICA/TREK EVs. In summary, these findings highlight the substantial potential of MICA as a platform to enhance the scalable production and therapeutic application of pro-regenerative EVs for bone augmentation strategies.

IntroductionBoth developing and developed nations have made the creation of innovative wound-healing nanomaterials based on natural extracts a top research goal. The objective of this research was to create a gel containing collagen nanoparticles and evaluate its therapeutic potential for skin lesions. MethodsCollagen nanoparticles from fish scales were produced for the first time using desolvation techniques. Using Fourier transform infrared spectroscopy (FTIR), the structure of the isolated collagen and its similarities to collagen type 1 were identified. The surface morphology of the isolated collagen and its reformulation into nanoparticles were examined using transmission and scanning electron microscopy. Human skin fibroblast cells were employed to examine the cytotoxicity of the nanomaterials, and an experimental model was used to evaluate the wound healing capability. ResultsCollagen nanoparticles formulation was confirmed using FTIR, SEM and TEM analysis. Cytotoxicity studies demomstrated that the manufactured nanoparticles have minor toxicity at high concentrations on human skin fibroblast. Histological investigation proved that the fabricated fish scale collagen nanoparticles promoted the healing process in comparison to the saline group. ConclusionThe fabricated product is a highly influential wound healing product that can be applicable for commercial use. The nanoscale size of collagen nanoparticles, make them interesting candidates for biological applications. Key Summary PointsO_LIThe goal of this research was to create natural, effective wound remedies that could lower health-care costs while also providing pain relief and, ultimately, effective scar repair. C_LIO_LICollagen nanoparticles can be synthesized from fish scale utilizing various nanotechnology-based approaches to stimulate skin cell proliferation and promote wound healing. C_LIO_LICollagen nanoparticles have a rough surface, have a negative potential, and can be used for drug delivery and wound healing. C_LIO_LIHistological and macroscopical analysis showed that the synthesized nanoparticles promoted faster wound healing. C_LI

Bone tissue engineering involves the usage of metals, polymers, and ceramics as the base constituents in the fabrication of various biomaterial 3D scaffolds. Of late, the composite materials facilitating enhanced osteogenic differentiation/regeneration have been endorsed as the ideally suited bone grafts for addressing critical-sized bone defects. Here, we report the successful fabrication of 3D composite scaffolds with collagen type I (Col-I) in conjunction with three different crystalline phases of calcium-phosphate (CP) nanomaterials [hydroxyapatite (HAp), beta-tricalcium phosphate ({beta}TCP), biphasic hydroxyapatite ({beta}TCP-HAp or BCP)], obtained by altering the pH as the major variable. The fabricated 3D scaffolds consisting of [~]70 wt % CP nanomaterials and [~] 30 Wt % of Col-I did mimic the ECM of bone tissue. The different Ca/P ratio and the orientation of CP nanomaterials in CP/Col-I composite scaffolds altered the microstructure, surface area, porosity, and mechanical strength of the scaffolds and also influenced the bioactivity, biocompatibility, and osteogenic differentiation of gingival-derived mesenchymal stem cells (gMSCs). The microstructure of CP/Col-I 3D scaffolds assessed by Micro-CT analysis revealed randomly oriented interconnected pores with pore sizes ranging from 80-250, 125-380, and 100-450{micro}m respectively for {beta}TCP/Col-I, BCP/Col-I, and HAp/Col-I scaffolds. Among these, the BCP/Col-I achieved the highest surface area ([~] 42.6 m2/g) and porosity ([~]85%), demonstrated improved bioactivity and biocompatibility, and promoted osteogenic differentiation of gMSCs. Interestingly, the Ca2+ ions (3 mM) released from scaffolds could also facilitate the osteocyte differentiation of gMSCs sans osteoinduction. Collectively, our study has demonstrated the ECM mimicking biphasic CP/Col-I 3D scaffold as an ideally suited tissue-engineered bone graft.

The field of bone tissue engineering seeks to mimic the bone extracellular matrix composition, balancing the organic and inorganic components. In this regard, additive manufacturing (AM) of highly loaded polymer-calcium phosphate (CaP) composites holds great promise towards the design of bioactive scaffolds. Yet, the biological performance of such scaffolds is still poorly characterized. In this study, melt extrusion AM (ME-AM) was used to fabricate poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT)-nanohydroxyapatite (nHA) scaffolds with up to 45 wt% nHA, which presented significantly enhanced compressive mechanical properties, to evaluate their in vitro osteogenic potential as a function of nHA content. While osteogenic gene upregulation and matrix mineralization were observed on all scaffold types when cultured in osteogenic media, human mesenchymal stromal cells did not present an explicitly clear osteogenic phenotype, within the evaluated timeframe, in basic media cultures (i.e. without osteogenic factors). Yet, due to the adsorption of calcium and inorganic phosphate ions from cell culture media and simulated body fluid, the formation of a CaP layer was observed on PEOT/PBT-nHA 45 wt% scaffolds, which is hypothesized to account for their osteoinductivity in the long term in vitro, and osteoconductivity in vivo.

Dysregulated macrophage function is implicated in a wide range of disorders. In vitro hydrogel culture systems are often used as matrices to model and explore the effect of various external stimuli on macrophage polarization and behaviour. Here, we show that 3D alginate hydrogels are not "macrophage inert" and instead help to direct the maturation of primary human macrophages towards specific phenotypes. We compared polarization of M1-like and M2-like cells activated on planar substrates or in 3D alginate hydrogels (with or without adhesion motifs (RGD)). We show that culture in 3D alginate systems selectively alters M2 polarisation following activation; cells show a 2.6-fold increase in CD86 expression compared to cells matured on planar controls, and increase IL1{beta} cytokine secretion even in response to an M2-like stimulus (LPS alone in the absence of IFN{gamma}). Our results suggest that alginate materials may intrinsically stimulate M2 macrophages to acquire a unique polarization state (resembling M2b), characterized by enhanced expression of CD86 and IL1{beta} secretion while retaining low IL12 and high IL10 secretion typical for M2 macrophages. This has important implications for researchers using alginate hydrogels to study macrophage behavior in culture and co-culture systems, as alginate itself may induce direct phenotypic changes independently or in conjunction with other stimuli.

Graphene-reinforced bioactive glass scaffolds have gained significant attention in the field of bone tissue engineering due to their unique combination of mechanical strength, bioactivity, and electrical conductivity. Additive manufacturing techniques, such as 3D printing, provide a versatile platform for fabricating these scaffolds with precise control over their architecture and composition. Consequently, in this work, we have fabricated graphene oxide (GO)-reinforced 13-93B1 bioactive glass scaffold using the direct ink writing technique. A Pluronic F-127- based ink was prepared for scaffold fabrication, and its rheological properties were assessed for shear thinning behaviour, structural support, and recovery. Further, the fabricated scaffolds were characterized using micro-computed tomography, scanning electron microscopy, and energy dispersive x-ray spectroscopy. Additionally, computational fluid dynamics simulations with Dulbeccos modified eagle medium and blood were performed to evaluate the perfusion kinetics of the scaffolds. The inclusion of GO enhanced the compressive strength of the fabricated scaffolds by [~]225%. The morphological characterization based on micro-computed tomography showed that additively manufactured scaffolds have appropriate porosity, pore size, pore throat size, and interconnectivity. The live-dead assay results showed no cytotoxicity towards C2C12 mouse myoblast cells. Also, cell adhesion and cell viability results show better cell growth on the nanocomposite scaffolds. Overall, the fabricated scaffold is found suitable for bone tissue engineering applications.

Periodontitis is an inflammatory infection caused by bacterial plaque accumulation that affects the periodontium, a complex structure of different tissues (cementum, periodontal ligament and alveolar bone) that surrounds and supports the teeth. Current treatments lack bioactive signals to induce tissue repair and coordinated regeneration of the periodontium, thus alternative strategies are needed to improve clinical outcomes. Cell-derived extracellular matrix (ECM) has been combined with biomaterials to enhance their biofunctionality for various tissue engineering (TE) applications. In this work, bioactive cell-derived ECM loaded electrospun polycaprolactone/chitosan (PCL/CTS) nanofibrous scaffolds were developed combining polymer solutions with lyophilized decellularized ECM (dECM) derived from human Periodontal Ligament Stem/Stromal Cells (PDLSCs). The works aims were to fabricate and characterize cell-derived ECM electrospun PCL/CTS scaffolds in terms of morphology, physico-chemical, thermal and mechanical properties and assess their ability to enhance the osteogenic differentiation of PDLSCs, envisaging periodontal TE applications. PDLSCs were cultured and used for dECM production. PDLSCs-derived dECM was characterized regarding morphology, protein expression, DNA removal efficiency, and glycosaminoglycans and collagen contents. Osteogenic differentiation of PDLSCs was performed on PCL, PCL/CTS and PCL/CTS/ECM electrospun scaffolds for 21 days. The obtained results demonstrate that PCL/CTS/ECM scaffolds promoted cell proliferation compared to PCL and PCL/CTS scaffolds, while maintaining similar physical and mechanical properties of PCL/CTS scaffolds. PCL/CTS/ECM scaffolds enhanced the osteogenic differentiation of PDLSCs, confirmed by increased alkaline phosphatase activity, calcium deposition, and bone-specific marker genes expression. Moreover, PCL/CTS scaffolds showed higher levels of cell mineralization than PCL scaffolds. Overall, this work describes the first use of lyophilized cell-derived ECM loaded electrospun scaffolds for periodontal TE applications and highlights its potential as a promising therapeutic strategy for periodontitis treatment.

"Green nanotechnologies have emerged as environmentally friendly alternatives against microbial multidrug-resistant biofilms. In this study, bactericidal "green" nanolayers (NL) were developed on Ti surfaces using two isomeric phytocompounds, carvacrol (Carv-Ti-NL) and thymol (TOH-Ti-NL). These NLs were fabricated using a one-step immersion treatment method based on a simple and spontaneous self-assembly process. Both NLs revealed strong antimicrobial activity, displaying anti-biofilm and biocidal effects. Notably, TOH-Ti-NL exhibited superior osteogenic performance compared to Carv-Ti-NL, as evidenced by enhanced pre-osteoblast cell attachment and growth, and the production of ALP, collagen type I and Ca2+ deposition. In contrast, fibroblastic cells exhibited reduced attachment on TOH-Ti-NL and enhanced proliferation on Carv-Ti-NL. Considering the biological differential effects, the physicochemical properties of these conformational isomers NLs were studied to elucidate potential differences that could impact on cell response. Although the ATR-FTIR spectra of the NLs were similar and indicated the spontaneous oxidation of Carv and TOH leading to ketonic structures, distinct contributions were observed after the electrooxidation of each NL. Slight differences in hydrophilicity were found for both nanostructures, but higher roughness was found for TOH-Ti-NL. Furthermore, the release curves of Carv and TOH from the NLs revealed distinct profiles over time. Overall, Carv and TOH formed self-assembled layers on Ti able to eradicate Staphylococcus aureus biofilms. Their different physical and chemical characteristics induced distinct responses from eukaryotic cells attached to the NLs. Given these characteristics one might envisage the use of either Carv-Ti-NL or TOH-Ti-NL in order to fine-tune specific chemical physical properties of Ti-based implants. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/610464v1_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@1c288f5org.highwire.dtl.DTLVardef@adc72corg.highwire.dtl.DTLVardef@ef2763org.highwire.dtl.DTLVardef@102d823_HPS_FORMAT_FIGEXP M_FIG C_FIG

Engineered living materials (ELMs) are gaining momentum for biomedical applications as self-replenishing drug depots, smart wound dressings, or as wearable sensors. Current studies on ELM-host interaction are mainly limited to the exchange of biochemical cues between ELMs and surrounding cells and tissues. Here we show that the genetically programmed mechanical properties of ELMs modulate mechanosignaling pathways in mammalian cells cultivated onto the living materials. To this aim, we genetically modulated curli fiber production in E. coli and analyzed the impact on the mechanical properties of the resulting ELMs. The living materials were used as matrix for the cultivation of mammalian cells engineered with a fluorescent reporter to indicate the activation of the mechano-responsive Hippo signaling pathway. We demonstrate that different genetically programmed ELM compositions translated into differential regulation of mechanosignaling in mammalian cells. These findings provide the perspective of using ELMs as extracellular matrix with genetically programmable mechanics for mammalian cells while also highlighting the need to consider the mechanical properties of therapeutic ELMs when assessing interaction with surrounding tissues. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=156 SRC="FIGDIR/small/620857v1_ufig1.gif" ALT="Figure 1"> View larger version (68K): org.highwire.dtl.DTLVardef@1a1ef9borg.highwire.dtl.DTLVardef@79c49forg.highwire.dtl.DTLVardef@5bb04dorg.highwire.dtl.DTLVardef@193a808_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOToC figureC_FLOATNO C_FIG

The morphological dynamics of microbial cell proliferation on an antimicrobial surface at an early growth stage was studied with Escherichia coli on the surface of a gel supplied with nanostructured AgNbO3 antimicrobial particles. We demonstrated an inhibitory surface concentration, analogous to minimum inhibitory concentration, beyond which the growth of colonies and formation of biofilm are inhibited. In contrast, at lower concentrations, colonies circumvent the antimicrobial activity of the particles and grow with a short lag time of a few hours. The applicability of these findings, in terms of estimating inhibitory surface concentration, was tested in the case of antimicrobial polymethyl methacrylate (PMMA) bone cement.

1Material micro-architecture and chemistry play pivotal roles in driving cell behaviour. Bone at a cellular level consists of arranged fibres with a cross-fibrillar mineral phase made up of curved nano-sized needle shaped crystals. This nano-structured mineral architecture can bind and stabilise proteins within bone for centuries and thus holds promise as a strategy for therapeutic delivery in regenerative medicine. Herein, we use melt electrowriting (MEW) technology to create fibrous 3D PCL micro-architectures. These scaffolds were further modified with an extrafibrillar coating of plate shaped micron-sized calcium phosphate crystals (pHA), or with a novel extrafibrillar coating of needle shaped nano-sized crystals (nnHA). A third scaffold was developed whereby nano-sized crystals were placed intrafibrillarly during the MEW process (iHA). X-ray diffraction revealed altered crystal structure and crystallinity between groups, with hydroxyapatite (HA) being the primary phase in all modifications. Water contact angle was investigated revealing increased hydrophilicity with extrafibrillar coatings, while tensile testing revealed enhanced stiffness in scaffolds fabricated with intrafibrillar HA. Biological characterisation demonstrated significantly enhanced human stem/stromal cell mineralisation with extrafibrillar coatings, with a 5-fold increase in mineral deposition with plate like structures and a 14-fold increase with a needle topography, demonstrating the importance of bone mimetic architectures. Given the protein stabilising properties of mineral, these materials were further functionalised with BMP2. Extrafibrillar coatings of nano-needles facilitated a controlled release of BMP2 from the scaffold which further enhanced mineral deposition by osteoprogenitors. This study thus outlines a method for fabricating scaffolds with precise fibrous micro-architectures and bone mimetic nano-needle HA extrafibrillar coatings which significantly enhance mesenchymal stem/stromal cell (MSC) osteogenesis and therapeutic delivery and thus hold great promise for bone tissue regeneration.