Bioceramic Surfaces Research Articles

Characterization and biological properties of copper nanoparticle-deposited calcium-based bioceramic surfaces fabricated on zirconium

Characterization and biological properties of copper nanoparticle-deposited calcium-based bioceramic surfaces fabricated on zirconium

Mineral matrix deposition of MC3T3-E1 pre-osteoblastic cells exposed to silicocarnotite and nagelschmidtite bioceramics: In vitro comparison to hydroxyapatite.

This work presents the effect of the silicocarnotite (SC) and nagelschmidtite (Nagel) phases on in vitro osteogenesis. The known hydroxyapatite of biological origin (BHAp) was used as a standard of osteoconductive characteristics. The evaluation was carried out in conventional and osteogenic media for comparative purposes to assess the osteogenic ability of the bioceramics. First, the effect of the material on cell viability at 24 h, 7 and 14 days of incubation was evaluated. In addition, cell morphology and attachment on dense bioceramic surfaces were observed by fluorescence microscopy. Specifically, alkaline phosphatase (ALP) activity was evaluated as an osteogenic marker of the early stages of bone cell differentiation. Mineralized extracellular matrix was observed by calcium phosphate deposits and extracellular vesicle formation. Furthermore, cell phenotype determination was confirmed by scanning electron microscope. The results provided relevant information on the cell attachment, proliferation, and osteogenic differentiation processes after 7 and 14 days of incubation. Finally, it was demonstrated that SC and Nagel phases promote cell proliferation and differentiation, while the Nagel phase exhibited a superior osteoconductive behavior and could promote MC3T3-E1 cell differentiation to a higher extent than SC and BHAp, which was reflected in a higher number of deposits in a shorter period for both conventional and osteogenic media.

Al2O3-Phosphate Bioceramic Fabrication via Spark Plasma Sintering-Reactive Synthesis: In Vivo and Microbiological Investigation

This research introduces a method to enhance the biocompatibility of bioinert Al2O3-based ceramics by incorporating calcium phosphates (hydroxyapatite (HAp) and tricalcium phosphate (TCP)) into alumina via spark plasma sintering-reactive sintering (SPS-RS). TGA/DTG/DTA and XRD revealed phase formation of HAp and TCP and determined the main temperature points of solid-phase reactions occurring in situ during the sintering of the CaO-CaHPO4 mixture within the volume of Al2O3 under SPS-RS conditions in the range of 900–1200 °C. SEM, EDX, low temperature, and nitrogen physisorption were used to monitor changes in the morphology, structure, and elemental composition of bioceramics. Structural meso- and macroporosity, with a mean mesopore size of 10 nm, were revealed in the ceramic volume, while sintering temperature was shown to play a destructive role towards the porous inorganic framework. The physico-chemical characterization demonstrated increased relative density (up to 95.1%), compressive strength (640 MPa and above), and Vickers microhardness (up to 700 HV) depending on the HAp and TCP content and sintering temperature. Four bioceramic samples with different contents of HAP (20 and 50 wt.%) were bio-tested in in vivo models. The samples were implanted into the soft tissues under the superficial fascia of the thorax of a laboratory animal (a New Zealand White rabbit, female) in the area of the trapezius muscle and the broadest muscle of the back. Based on the results of the assessment of the surrounding tissue reaction, the absence of specific inflammation, necrosis, and tumor formation in the tissues during the implantation period of 90 days was proven. Microbial tests and dynamics of Pseudomonas aeruginosa bacterial film formation on bioceramic surfaces were studied with respect to HAp content (20 and 50 wt.%) and holding time (18, 24, and 48 h) in the feed medium.

New Approach to Identify the Physiological State of Bone Cells at the Surface of Hydroxyapatite Bioceramics

The aim of this work was to identify robust and reproducible signatures characterizing the different steps of bone cell differentiation, from precursors to mature bone cells, using approaches allowing characterization by label-free imaging. Human mesenchymal stromal cells (hMSCs) were cultured either in a growth medium (GM), unable to induce cell differentiation by itself, or in an osteogenic differentiation medium (ODM) on hydroxyapatite ceramics or borosilicate glass. Cell density as well as cell structure, size, and morphology were investigated. A fluorescence microscopy-based approach was followed, using fluorescent labelling of cell features. Some early morphological changes of hMSC during osteogenic differentiation were identified as soon as 48h that were accentuated after 7 days of culture. Cell density was higher when cells were cultured in GM and the cells exhibited significantly smaller nuclei (size ratio about 1.3-1.5) than those cultured in ODM, regardless of the culture support. In ODM, the cells were also of bigger size (1.2 to 1.5 times) and their focal adhesions were reinforcedType I collagen, a gold standard marker of osteogenic differentiation, appeared more intense in ODM. These cell features can be determined using multimodal label-free imaging methods to characterize the differentiation state of hMSCs at the biomaterial surface. They give rise to new cost-effective approaches to investigate cell behavior by suppressing the chemical markers and reducing both the number of needed samples and the requested time to do so.

Calcium phosphate bioceramics: From cell behavior to chemical-physical properties

Calcium phosphate ceramics, including hydroxyapatite (HA), have been used as bone substitutes for more than 40 years. Their chemical composition, close to that of the bone mineral, confers them good biological and physical properties. However, they are not sufficient to meet all the needs in bone regenerative medicine, such as in the context of critical bone lesions. Therefore, it is essential to improve their biological performances in order to extend their application domains. In this aim, three approaches are mainly followed on the assumption that the biological response can be tuned by modifications of the chemical physical properties of the ceramic: 1) Incorporation of specific chemical species into the calcium phosphate crystalline lattice of chemical elements to stimulate bone repair. 2) Modulation of the bioceramic architecture to optimize the cellular responses at the interface. 3) Functionalization of the bioceramic surface with bioactive molecules. These approaches are supposed to act on separate parameters but, as they are implemented during different steps of the ceramic processing route, they cannot be considered as exclusive. They will ineluctably induces changes of several other physical chemical properties of the final ceramic that may also affect the biological response. Using examples of recent works from our laboratory, the present paper aims to describe how biology can be affected by the bioceramics modifications according to each one of these approaches. It shows that linking biological and chemical physical data in a rational way makes it possible to identify pertinent parameters and related processing levers to target a desired biological response and then more precisely tune the biological performance of ceramic biomaterials. This highlights the importance of integrating the biological evaluation into the heart of the processes used to manufacture optimized biomaterials.

Microbially Catalyzed Biomaterials for Bone Regeneration

Bone is a complex mineralized tissue composed of various organic (proteins, cells) and inorganic (hydroxyapatite, calcium carbonate) substances with micro/nanoscale structures. To improve interfacial bioactivity of bone-implanted biomaterials, extensive efforts are being made to fabricate favorable biointerface via surface modification. Inspired by microbially catalyzed mineralization, a novel concept to biologically synthesize the micro/nanostructures on bioceramics, microbial-assisted catalysis, is presented. It involves three processes: bacterial adhesion on biomaterials, production of CO3 2- assisted by bacteria, and nucleation and growth of CaCO3 nanocrystals on the surface of bioceramics. The microbially catalyzed biominerals exhibit relatively uniform micro/nanostructures on the surface of both 2D and 3D α-CaSiO3 bioceramics. The topographic and chemical cues of the grown micro/nanostructures present excellent in vitro and in vivo bone-forming bioactivity. The underlying mechanism is closely related to the activation of multiple biological processes associated with bone regeneration. The study offers a microbially catalytic concept and strategy of fabricating micro/nanostructured biomaterials for tissue regeneration.

Development of mesoporous bioactive glass‐containing macroporous titanium for controlled release of antimicrobial drugs

AbstractBiofilm‐associated infections pose a serious threat to the long‐term survival of metal‐based bone implants, which can potentially be resolved by the controlled delivery of antimicrobial agents locally at the implant surface. Mesoporous bioactive glasses (BAGs) are multifunctional materials able to combine bone‐bonding properties with such a drug release functionality. Here, we propose for the first time to modify a macroporous Ti implant material with an antimicrobial‐releasing BAG phase. The feasibility of a sol‐gel synthesis route, including the structure‐directing agent (SDA) Pluronic F127, and its effect on the mesoporous structure and concomitant drug release performance was evaluated. Mesopore sizes ranged from 3.4 nm for SDA‐free to 3.7 nm for SDA‐derived BAG, thereby both enabling configurational diffusion of the antiseptic chlorhexidine (CHX), but the latter showed a more narrow pore size distribution leading to a slower, more controlled release. Adjusting the feed concentration allowed fine‐tuning the daily CHX release through the SDA‐derived Ti/BAG composite to 1.4 μM. Even though just below the biofilm inhibitory concentration, this daily release rate was sufficient to effectively prevent Streptococcus mutans biofilm formation on the surface of the material. This proof‐of‐concept for a temporary antimicrobial‐releasing bioceramic surface modification on Ti can be of interest for orthopedic implants.

Polylactic acid interactions with bioceramic surfaces

Polylactic acid interactions with bioceramic surfaces

In vitro biological and antimicrobial properties of chitosan-based bioceramic coatings on zirconium

Ca-based porous and rough bioceramic surfaces were coated onto zirconium by micro-arc oxidation (MAO). Subsequently, the MAO-coated zirconium surfaces were covered with an antimicrobial chitosan layer via the dip coating method to develop an antimicrobial, bioactive, and biocompatible composite biopolymer and bioceramic layer for implant applications. Cubic ZrO2, metastable Ca0.15Zr0.85O1.85, and Ca3(PO4)2 were detected on the MAO surface by powder-XRD. The existence of chitosan on the MAO-coated Zr surfaces was verified by FTIR. The micropores and thermal cracks on the bioceramic MAO surface were sealed using a chitosan coating, where the MAO surface was porous and rough. All elements such as Zr, O, Ca, P, and C were homogenously distributed across both surfaces. Moreover, both surfaces indicated hydrophobic properties. However, the contact angle of the MAO surface was lower than that of the chitosan-based MAO surface. In vitro bioactivity on both surfaces was investigated via XRD, SEM, and EDX analyses post-immersion in simulated body fluid (SBF) for 14 days. In vitro bioactivity was significantly enhanced on the chitosan-based MAO surface with respect to the MAO surface. In vitro microbial adhesions on the chitosan-based MAO surfaces were lower than the MAO surfaces for Staphylococcus aureus and Escherichia coli.

Activity and Mechanism of Action of the Bioceramic Silicon Nitride as an Environmentally Friendly Alternative for the Control of the Grapevine Downy Mildew Pathogen Plasmopara viticola.

Downy mildew of grapevine, caused by Plasmopara viticola (Berk. and Curt.) Berl. and de Toni, is one of the most devastating diseases of grapevine, severely affecting grape and wine production and quality worldwide. Infections are usually controlled by the intensive application of synthetic fungicides or by copper-based products in organic farming, rising problems for soil contamination and adverse impacts on environment and human health. While strict regulations attempt to minimize their harmful consequences, the situation calls for the development of alternative fungicidal strategies. This study presents the unprecedented case of a bioceramic, silicon nitride, with antimicrobial properties against P. viticola, but without adverse effects on human cells and environment, opening the way to the possible extension of silicon nitride applications in agriculture. Raman spectroscopic assessments of treated sporangia in conjunction with microscopic observations mechanistically showed that the nitrogen-chemistry of the bioceramic surface affects pathogen’s biochemical components and cell viability, thus presenting a high potential for host protection from P. viticola infections.

Nature-inspired topographies on hydroxyapatite surfaces regulate stem cells behaviour

Surface topography is one of the key factors in regulating interactions between materials and cells. While topographies presented to cells in vivo are non-symmetrical and in complex shapes, current fabrication techniques are limited to replicate these complex geometries. In this study, we developed a microcasting technique and successfully produced imprinted hydroxyapatite (HAp) surfaces with nature-inspired (honeycomb, pillars, and isolated islands) topographies. The in vitro biological performance of the developed non-symmetrical topographies was evaluated using adipose-derived stem cells (ADSCs). We demonstrated that ADSCs cultured on all HAp surfaces, except honeycomb patterns, presented well-defined stress fibers and expressed focal adhesion protein (paxillin) molecules. Isolated islands topographies significantly promoted osteogenic differentiation of ADSCs with increased alkaline phosphatase activity and upregulation of key osteogenic markers, compared to the other topographies and the control unmodified (flat) HAp surface. In contrast, honeycomb topographies hampered the ability of the ADSCs to proliferate and differentiate to the osteogenic lineage. This work presents a facile technique to imprint nature-derived topographies on the surface of bioceramics which opens up opportunities for the development of bioresponsive interfaces in tissue engineering and regenerative medicine.

Flexible organic–inorganic hybrid bioceramic for bone tissue regeneration

Development of novel biomaterials for bone regeneration is based on the sufficient bone-bonding ability, bioactivity and biocompatibility. In this study, novel flexible poly(butylene succinate)/polydimethysiloxane-modified bioactive glass/nano-hydroxyapatite (PBSu/PDMS-BG/nHA) hybrid bioceramic with various nHA concentration on the in vitro bone-like hydroxyapatite (HA) formation, biomineralization activity and osteoblast cell biocompatibility were investigated. The rapid precipitation of HA on the hybrid bioceramic surfaces was found after being immersed in simulated body fluid (SBF) for seven days. Results show that the amount of HA deposition increased with the increase of nHA concentration. The optimized PBSu/PDMS-BG/nHA hybrid bioceramic exhibited good flexibility, high biomineralization activity and good osteoblast cell biocompatibility.

The effect of natural fibres template on the chemical and structural properties of Biphasic Calcium Phosphate scaffold

Porous biphasic bioceramics that contain hydroxyapatite and tricalcium phosphate were synthesized in this study using luffa cylindrical fibres (LCF) as the template. In addition to improving the pore structure, using this template led to a chemical coating of the pores´ internal surfaces by important minerals such as magnesium and phosphorous from the LCF residue. Evaluation of our preliminary results suggests promising applications in bone tissue engineering. The synthesized porous bioceramics were characterized in view of their microstructural, physical, and in vitro features. They showed a trimodal pore system comprising a nano-pore network, smaller macropore with diameters of 5 to 100 μm, and cylindrical macropores with diameters from 100 to 400 μm; and 75% of interconnected porosity was confirmed by Mercury intrusion porosimetry and SEM images. Enhanced cell adhesion of the internal pore surfaces generated long and extended cells inside the macropores. SEM images show how the cells adhered to bioceramic surfaces and developed cytoplasmic extensions. Their proliferation in vitro demonstrates that the scaffold architecture and mineral composition are suitable for mesenchymal stem cell seeding and growth.

Shape Matters: Crystal Morphology and Surface Topography Alter Bioactivity of Bioceramics in Simulated Body Fluid

For bioactive biomaterials such as bioceramics and bioglass, it is generally accepted that, apart from acting as heterogeneous nucleators, it is their solubility and the resulting release of relevant ions such as calcium or basic anions which mainly governs the biomaterial's bioactivity. This contribution reveals that this bioactivity, as assessed by simulated body fluid (SBF), can also be considerably modified by the bioceramic's morphology, i.e., bioactivity is also governed by microstructure and surface morphology. When crystals are forced to adopt out‐of‐equilibrium crystal habit, this simple change in morphology converts an essentially bioinert material, here calcite, into a bioceramic which shows bioactivity in SBF. On larger length scales, already simple morphological changes, such as scratches, can have inverse effects. Limited mass transport into grooves and pits on a bioceramic surface can lead to local ion depletion which, in turn, causes reduced bioactivity of bioceramics which, otherwise, show distinct bioactivity in SBF. This contribution emblematically illustrates the unforeseen importance of even minor morphology changes on different length scales when assessing and designing a biomaterial's bioactivity through SBF assays.

Rapid fabrication of ultra-smooth Y-TZP bioceramic surfaces by dual-axis wheel polishing: process development and tribological characterization

The existing artificial joint implants using bioceramic materials face problems of difficulty in manufacturing and premature failure due to wear. This paper investigated a rapid preparing process of ultra-smooth surfaces of yttria-stabilized tetragonal zirconia polycrystal bioceramics based on the dual-axis wheel polishing (DAWP) system. Friction and wear tests were conducted to prove that the prepared ultra-smooth surface can effectively reduce wear. The effects of process parameters on polishing performances were investigated. The XRD and SEM analysis and micro-hardness testing were used to characterize the prepared surface in material behaviors. Tribological tests were carried out on a ball-on-plate reciprocating tribometer to comparatively study the tribological behavior and wear mechanism of the prepared ultra-smooth surfaces and the conventional surface at sub-microscale. The used finishing technology can steadily achieve fast preparation of ultra-smooth bioceramic surfaces, and with a high material removal rate (the highest value was 1.14 mg/min). Besides, in contrast to the conventional surface (Ra 129 nm), the prepared ultra-smooth surface (Ra 0.38 nm) achieved a much smaller friction coefficient, and much less wear volume, indicating that the wear resistance of the ultra-smooth surface was significantly improved.

Effect of the processing parameters on surface, physico-chemical and mechanical features of bioceramics synthesized from abundant carp fish bones

Aim of this research was to evaluate the effect of an improved processing thermal method of calcium phosphates obtained from a natural source of high availability (i.e. cyprinids bones). Thereby, the sinterability of the naturally-derived ceramics has been explored. The samples were characterized before and after sintering in terms of surface features (morphology, roughness, wettability and surface energy), weight loss, shrinking, composition, structure, and mechanical properties.The results showed that the initial processing has a significant effect on the sintering outcomes: the morphology and mechanical features were clearly influenced by the processing temperature, while minor effects were observed on the surface and structure properties. Therefore, the study unveils suitable strategies for controlling the characteristics of cost-effective bioceramics and opens up new perspectives for the sustainable manufacturing of highly valuable biomedical products from abundant carp fish bones.

Effects of surface roughness and texture on the bacterial adhesion on the bearing surface of bio-ceramic joint implants: An in vitro study

Reducing the bacterial adhesion to a bearing surface is crucial for increasing the success rate of joint replacement surgery and ensuring the service performance of joint replacement implants. In this study, the effects of the surface states (with a smoothness from the sub-micron to nano-scale level) on the adhesion of Staphylococcus aureus on yttria-stabilized zirconia bio-ceramic surfaces were considered. Ceramic surfaces with different surface states were prepared using various machining processes, and the surface characteristics, e.g., the surface roughness, surface topography, and wettability, were measured. It was found that achieving a nano-scale roughness on a bio-ceramic surface can significantly reduce the bacterial adhesion. The number of bacterial adhesion on a smooth surface with a roughness of Ra 1 nm is only 2% of that on a conventional surface with a roughness of Ra 205 nm; in addition, compared with a nano-scale surface with a unidirectional texture, achieving a uniform surface texture can further reduce the bacterial adhesion. As the surface roughness reduces from the sub-micron scale to the nano-scale level, the surface state gradually changes from hydrophobic to hydrophilic, and becomes unfavorable for the adhesion of hydrophobic S. aureus; in addition, the anchoring points for bacterial adhesion gradually decrease or even disappear, and hence the bacterial-surface bonding strength weakens. It was concluded that the preparation of a smooth nano-scale surface and the elimination of unidirectional surface textures can effectively inhibit the initial adhesion and proliferation of S. aureus on the bearing surfaces of a ceramic joint implant, which will reduce the occurrence of implant-related infections.

Activating macrophages for enhanced osteogenic and bactericidal performance by Cu ion release from micro/nano-topographical coating on a titanium substrate

In the field of orthopaedics, inflammation-modulatory biomaterials are receiving increasing attentions due to their abilities to regulate innate immune response and mediate wound healing. In the current work, a Cu-containing micro/nano-topographical bio-ceramic surface (Cu-Hier-Ti surface) was employed as material model to explore the role played by Cu2+ release or material surface in regulating macrophage polarization as well as macrophage-mediated osteogenic and bactericidal effect. A Cu-free micro-topographical surface (Micro-Ti surface) generated by micro-arc oxidation was employed as control. The results showed that Cu2+ supplemented directly into the culture medium or released from Cu-Hier-Ti surface could polarize macrophages to pro-inflammatory M1 phenotype by activating Cu-transport signaling (copper transporter 1 (CTR1) and ATP7A) in macrophages, while the material characteristics exhibited anti-inflammatory effect to some extent by regulating integrin (α5, αM, β1 and β2) and TLR (TLR-3, TLR-4, Myd88 and Ticam-1/2) signaling. Macrophages grown on Cu-Hier-Ti surface or treated by Cu2+ could create a favorable inflammatory microenvironment for osteoblast-like SaOS-2 cell proliferation and differentiation. Moreover, Cu-Hier-Ti surface promoted macrophage capacity to engulf and kill bacteria, even though it did not show direct bactericidal effect against Staphylococcus aureus. In vivo results showed that Cu-Hier-Ti surface could lead to promoted osteointegraion and enhanced expression levels of M1 surface marker CD11c, growth factor BMP-6 and osteogenic makers including osteocalcin (OCN) and Runx-2 at the biomaterial/bone tissue interface in a rat model. The results indicate that Cu could be employed as a promising inflammation-modulatory agent to activate macrophages for enhanced osteogenic and bactericidal effect. Statement of significanceThe next generation of bone biomaterials should be active to regulate the local inflammatory environment such that it favors bone regeneration. For the design and development of Cu-containing inflammation-modulatory biomaterials, it is of great importance to recognize the exact role played by Cu2+ release or material surface characteristics. So far, relatively little is known about the regulatory role of Cu2+ or micro/nano-topographical surface on macrophages. The results in the current work suggest that Cu2+ release and material surface characteristics of Cu-containing micro/nano-topographical coating could activate distinct signaling pathways in macrophages. The activated M1 macrophages exhibited stimulatory effect on osteoblast maturation and enhanced bactericidal capacity against Staphylococcus aureus. This study might provide new thoughts for the development of multi-functional Cu-containing biomaterials.

In situ molecular vibration insights into the antibacterial behavior of silicon nitride bioceramic versus gram-negative Escherichia coli.

Gram-negative bacteria represent a substantial fraction of pathogens responsible for periprosthetic infections. Given the increasing resistance of such bacteria to antibiotics, significant efforts are nowadays paid in developing new biomaterial surfaces, which offer resistance against bacterial adhesion and/or possess inherent antibacterial effects. Non-oxide silicon nitride (Si3N4) bioceramic in its polycrystalline form is a biomaterial with inherent antibacterial properties. Building upon previous phenomenological findings, the present study focuses on vibrational analyses of the metabolic response of Escherichia coli at the molecular level. A time-lapse study is conducted upon exposing the bacteria in vitro to Si3N4 bioceramic surfaces. A comparison is carried out with the as-cultured bacterial strain and with bacteria exposed to other commercially available biomaterials, namely, Ti-alloy (Ti6Al4V-ELI) and zirconia-toughened alumina (ZTA) oxide bioceramic tested under exactly the same experimental conditions. The metabolic pathways before and after exposure to different substrates were monitored by means of Raman and FTIR spectroscopies. Results indicated the development of significant osmotic stress in the bacterial strain and constant concentration decreases of its cellular compounds markers over time upon exposure to Si3N4. This ultimately led to bacterial lysis (also confirmed by conventional fluorescence microscopy assays). The main antibacterial effect was of chemical origin and driven by the elution of nitrogen ions from the Si3N4 surface, successively converted into ammonia (NH3) or ammonium (NH4)+ in aqueous solution, depending on environmental pH. The presence of these nitrogen species created osmotic stress in the cytoplasmic space. In answer to the osmotic stress, metabolic rates changed rapidly, the bacterial membrane was damaged, and lysis occurred almost completely within 48 h exposure. The antibacterial behavior exerted by the Si3N4 substrate on E. coli was more effective than that observed on the biomedical Ti6Al4V alloy. Conversely, no lysis but bacterial proliferation was recorded for E. coli exposed to ZTA bioceramic oxide substrates.

Novel strategy for toughening robocast bioceramic scaffolds using polymeric cores

Abstract A novel method for the fabrication of hybrid polymer/ceramic porous scaffolds with core/shell struts is developed. Robocasting with coaxial needles is used to deposit beta-tricalcium phosphate scaffolds with hollow rods, which are subsequently filled with a polycaprolactone melt by suction. The polymeric core provides outstanding improvement of the toughness of the structure in bending, with strain energy density increasing nearly two orders of magnitude and continuous polymeric fibres holding the structure together even after large deflections. Moreover, flexural strength is not significantly reduced compared to dense-strut structures; and the macroporosity of the scaffold and osteoconductivity of bioceramic surfaces are preserved.