Cerium (III) and (IV) containing mesoporous glasses/alginate beads for bone regeneration: bioactivity, biocompatibility and reactive oxygen species activity

Cerium-doped mesoporous bioactive glass nanoparticles reduce oxidative stress and adipogenic differentiation in human bone marrow-derived mesenchymal stromal cells

Increased levels of reactive oxygen species (ROS) favor adipogenic over osteogenic differentiation in human bone-marrow derived mesenchymal stromal cells (BMSCs). Therefore, biomaterials containing ROS-suppressing elements such as Cerium (Ce) have been introduced to cell-based bone-tissue-engineering (BTE) approaches. This study was conducted to assess the efficacy of Ce-doped mesoporous bioactive glass nanoparticles (MBGNs) in reducing ROS levels and subsequently inhibiting the adipogenic differentiation of BMSCs. To this end, BMSCs were cultivated in adipogenesis inducing medium (AIM) and exposed to ions released from Ce-free MBGNs (composition in mol%: 86SiO2-14CaO), Low-Ce-MBGNs (composition in mol%: 86.6SiO2-12.1CaO-1.3CeO2) and High-Ce-MBGNs (composition in mol%: 86.0SiO2-11.8CaO-2.2CeO2). The influence of the different MBGNs on the expression of adipogenic and ROS-scavenging genes was assessed as well as their influence on lipid formation and the physical presence of ROS. Ce-MBGNs significantly reduced lipid production and the expression of adipogenic marker genes when compared to BMSCs cultivated in the presence of MBGNs or AIM alone. Furthermore, ROS levels were decreased by Ce-MBGNs alongside an upregulation of the expression of genes encoding for ROS-scavenging enzymes. Ce-MBGNs have proven their antioxidative potential. Mediated by the reduction of ROS, the undesired differentiation of BMSCs towards adipogenic lineage within BTE applications has been effectively suppressed. Ce-MBGNs target differentiation pathways in BMSCs precisely and therefore constitute an attractive biomaterial in the field of ion-based BTE.

Advancements in mesoporous bioactive glasses for effective bone cancer therapy: Recent developments and future perspectives

This review focuses on recent advancements in the effective use of mesoporous bioactive glasses (MBG) in the treatment of bone cancer, focusing on Osteosarcoma (OS). Bone cancers are rare but are associated with significant morbidity and mortality; often, aggressive treatment is required. Conventional treatments such as surgery, radiation, and chemotherapy are often not enough. This is because surgery cannot completely remove the tumor, without creating a critical size which are defects larger than 2 cm that cannot be repaired by physiological mechanisms. As a result, patients often face the additional burden of radiation and chemotherapy. Scientists have been exploring new treatments, including hyperthermia-targeted therapy, polymeric nanoparticles, and stem cell therapy. This could potentially negatively impact healthy tissues and organs. MBG offers a promising alternative to chemotherapeutic agents and ions for disease treatment as it acts as a multifunctional drug delivery system (DDS). In addition, MBG can also be engineered into scaffolds to facilitate local delivery of growth factors and drugs, thus promoting the efficiency of bone healing and restoration. Therefore, the current review highlights various MBG types reported in the past decade and explores potential future paths to enhance their use in bone cancer treatment while also giving insight on the already commercially available BGs that are used in different bone-related disease.

Evaluation of the Properties of Bioactive Mesoporous Glasses Doped with Cerium and Loaded with Polyphenols

(1) Background: The onset of inflammation and oxidative stress after biomaterial implantation can lead to complications and prolonged recovery times. To address this, bioactive mesoporous glasses doped with cerium (0, 3.6 and 5.3 mol%) were loaded with three different biomolecules-3-hydroxyflavone, quercetin and morin hydrate-to enhance antioxidant properties while preserving bioactivity. (2) Methods: Elemental analysis, specific surface area determination, spectroscopic techniques, evaluation of antioxidant activity and in vitro bioactivity assessment were performed to characterize mesoporous glass loaded with biomolecules. (3) Results: Biomolecule loading gives values in the range of 0.5-2.0% and 10.3-39.6% for loading content and loading efficiency, respectively. The loading order is quercetin > morine hydrate > 3-hydroxyflavone, and a cerium percentage of 3.6 seems to be a good compromise. The antioxidant properties evaluated on both solids and solutions in contact with simulated biological fluids improve markedly over loaded glasses, and the most promising results are obtained with quercetin. In the most efficient systems, the bioactivity results were delayed and more evident at longer times (168 h) but were still retained. (4) Conclusions: We obtained new materials still bioactive with improved antioxidant properties that can be proposed for the regeneration of both hard and soft tissues.

Bioactive Glass in Tissue Regeneration: Unveiling Recent Advances in Regenerative Strategies and Applications

Bioactive glass (BG) is a class of biocompatible, biodegradable, multifunctional inorganic glass materials, which is successfully used for orthopedic and dental applications, with several products already approved for clinical use. Apart from exhibiting osteogenic properties, BG is also known to be angiogenic and antibacterial. Recently, BG's role in immunomodulation has been gradually revealed. While the therapeutic effect of BG is mostly reported in the context of bone and skin-related regeneration, its application in regenerating other tissues/organs, such as muscle, cartilage, and gastrointestinal tissue, has also been explored recently. The strategies of applying BG have also expanded from powder or cement form to more advanced strategies such as fabrication of composite polymer-BG scaffold, 3D printing of BG-loaded scaffold, and BG-induced extracellular vesicle production. This review presents a concise overview of the recent applications of BG in regenerative medicine. Various regenerative strategies of BG will be first introduced. Next, the applications of BG in regenerating various tissues/organs, such as bone, cartilage, muscle, tendon, skin, and gastrointestinal tissue, will be discussed. Finally, clinical applications of BG for tissue regeneration will be summarized, and future challenges and directions for the clinical translation of BG will be outlined.

Enhancing orthopaedic implant efficacy: the development of cerium-doped bioactive glass and polyvinylpyrrolidone composite coatings via MAPLE technique

This study investigates the potential of combining Cerium-doped bioactive glass (BBGi) with Polyvinylpyrrolidone (PVP) to enhance the properties of titanium (Ti) implant surfaces using the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The primary focus is on improving osseointegration, corrosion resistance, and evaluating the cytotoxicity of the developed thin films towards host cells. The innovative approach involves synthesizing a composite thin film comprising BBGi and PVP, leveraging the distinct benefits of both materials: BBGi's biocompatibility and osteoinductive capabilities, and PVP's film-forming and biocompatible properties. Results demonstrate that the BBGi + PVP coatings significantly enhance hydrophilicity, indicating improved cell-material interaction potential. The electrochemical analysis reveals superior corrosion resistance of the BBGi + PVP films compared to BBGi alone, which is critical for long-term implant stability. The mechanical adherence tests confirm the robust attachment of the coatings to Ti substrates, surpassing the ISO standards for implant materials. Biocompatibility tests show promising cell viability and negligible cytotoxic effects, with a controlled inflammatory response, underscoring the potential of BBGi + PVP coatings for orthopedic applications. The study concludes that the synergistic combination of BBGi and PVP, applied through the MAPLE technique, offers a promising route to fabricate bioactive and corrosion-resistant coatings for Ti implants, potentially enhancing osseointegration and longevity in clinical settings.

Nano-scaffold-based delivery systems of antimicrobial agents in the treatment of osteomyelitis ; a narrative review

Osteomyelitis caused by drug-resistant pathogens is one of the most important medical challenges due to high rates of mortality and morbidity, and limited therapeutical options. The application of novel nano-scaffolds loaded with antibiotics has widely been studied and extensively evaluated for in vitro and in vivo inhibition of pathogens, regenerating damaged bone tissue, and increasing bone cell proliferation. The treatment of bone infections using the local osteogenic scaffolds loaded with antimicrobial agents may efficiently overcome the problems of the systemic use of antimicrobial agents and provide a controlled release and sufficient local levels of antibiotics in the infected sites. The present study reviewed various nano-scaffolds delivery systems of antimicrobial drugs evaluated to treat osteomyelitis. Nano-scaffolds offer promising approaches because they simulate natural tissue regeneration in terms of their mechanical, structural, and sometimes chemical properties. The potential of several nano-scaffolds prepared by natural polymers such as silk, collagen, gelatin, fibrinogen, chitosan, cellulose, hyaluronic, alginate, and synthetic compounds such as polylactic acid, polyglycolic acid, poly (lactic acid-co-glycolic acid), poly-ɛ-caprolactone have been studied for usage as drug delivery systems of antimicrobial agents to treat osteomyelitis. In addition to incorporated antimicrobial agents and the content of scaffolds, the physical and chemical characteristics of the prepared delivery systems are a determining factor in their effectiveness in treating osteomyelitis.

Harnessing cerium-based biomaterials for the treatment of bone diseases

Bone, an actively metabolic organ, undergoes constant remodeling throughout life. Disturbances in the bone microenvironment can be responsible for pathologically bone diseases such as periodontitis, osteoarthritis, rheumatoid arthritis and osteoporosis. Conventional bone tissue biomaterials are not adequately adapted to complex bone microenvironment. Therefore, there is an urgent clinical need to find an effective strategy to improve the status quo. In recent years, nanotechnology has caused a revolution in biomedicine. Cerium(III, IV) oxide, as an important member of metal oxide nanomaterials, has dual redox properties through reversible binding with oxygen atoms, which continuously cycle between Ce(III) and Ce(IV). Due to its special physicochemical properties, cerium(III, IV) oxide has received widespread attention as a versatile nanomaterial, especially in bone diseases. This review describes the characteristics of bone microenvironment. The enzyme-like properties and biosafety of cerium(III, IV) oxide are also emphasized. Meanwhile, we summarizes controllable synthesis of cerium(III, IV) oxide with different nanostructural morphologies. Following resolution of synthetic principles of cerium(III, IV) oxide, a variety of tailored cerium-based biomaterials have been widely developed, including bioactive glasses, scaffolds, nanomembranes, coatings, and nanocomposites. Furthermore, we highlight the latest advances in cerium-based biomaterials for inflammatory and metabolic bone diseases and bone-related tumors. Tailored cerium-based biomaterials have already demonstrated their value in disease prevention, diagnosis (imaging and biosensors) and treatment. Therefore, it is important to assist in bone disease management by clarifying tailored properties of cerium(III, IV) oxide in order to promote the use of cerium-based biomaterials in the future clinical setting. STATEMENT OF SIGNIFICANCE: In this review, we focused on the promising of cerium-based biomaterials for bone diseases. We reviewed the key role of bone microenvironment in bone diseases and the main biological activities of cerium(III, IV) oxide. By setting different synthesis conditions, cerium(III, IV) oxide nanostructures with different morphologies can be controlled. Meanwhile, tailored cerium-based biomaterials can serve as a versatile toolbox (e.g., bioactive glasses, scaffolds, nanofibrous membranes, coatings, and nanocomposites). Then, the latest research advances based on cerium-based biomaterials for the treatment of bone diseases were also highlighted. Most importantly, we analyzed the perspectives and challenges of cerium-based biomaterials. In future perspectives, this insight has given rise to a cascade of cerium-based biomaterial strategies, including disease prevention, diagnosis (imaging and biosensors) and treatment.

Cerium doping of 45S5 bioactive glass improves redox potential and cellular bioactivity

45S5 Bioglass (BG) is composed of a glass network with silicate based on the component and can be doped with various therapeutic ions for the enhancement of hard tissue therapy. Nanoceria (CeO2) has been shown to indicate redox reaction and enhance the biological response. However, few studies focus on the proportion of CeO2-doped and its effect on the cellular bioactivity of CeO2-doped BG (CBG). In this study, we synthesized the CBG series with increasing amounts of doping CeO2 ranging (1 to 12) wt.%. The synthesized CBG series examined the characterization, mineralization capacity, and cellular activity against BG. Our results showed that the CBG series exhibited a glass structure and indicated the redox states between Ce3+ and Ce4+, thus they showed the antioxidant activity by characterization of Ce. The CBG series had a stable glass network structure similar to BG, which showed the preservation of bioactivity by exhibiting mineralization on the surface. In terms of biological response, although the CBG series showed the proliferative activity of pre-osteoblastic cells similar to BG, the CBG series augmented not only the alkaline phosphatase activity but also the osteogenic marker in the mRNA level. As stimulated the osteogenic activity, the CBG series improved the biomineralization. In conclusion, the CBG series might have a potential application for hard tissue therapeutic purposes.

Bifunctional mesoporous glasses for bone tissue engineering: Biological effects of doping with cerium and polyphenols in 2D and 3D in vitro models

This study evaluates the cytocompatibility of cerium-doped mesoporous bioactive glasses (Ce-MBGs) loaded with polyphenols (Ce-MBGs-Poly) for possible application in bone tissue engineering after tumour resection. We tested MBGs powders and pellets on 2D and 3D in vitro models using human bone marrow-derived mesenchymal stem cells (hMSCs), osteosarcoma cells (U2OS), and endothelial cells (EA.hy926). Promisingly, at a low concentration in culture medium, Poly-loaded MBGs powders containing 1.2 mol% of cerium inhibited U2OS metabolic activity, preserved hMSCs viability, and had no adverse effects on EA.hy926 migration. Moreover, the study discussed the possible interaction between cerium and Poly, influencing anti-cancer effects. In summary, this research provides insights into the complex interactions between Ce-MBGs, Poly, and various cell types in distinct 2D and 3D in vitro models, highlighting the potential of loaded Ce-MBGs for post-resection bone tissue engineering with a balance between pro-regenerative and anti-tumorigenic activities.

Doxorubicin loaded cerium substituted hydroxyapatite nanoparticles: A promising new therapeutic approach for bone regeneration, doxorubicin delivery, and cancer treatment

The current study used the precipitation method to prepare pure calcium hydroxyapatite (HA) and cerium-substituted hydroxyapatite (Ce-HA) nanoparticles, where cerium ions were exchanged into the HA structure at different concentrations ranging from 3 to 7 wt%. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, and zeta potential were used to examine the structural characteristics of the nanoparticles. Additionally, the antibacterial and antifungal effects of the produced materials on Gram-positive, Gram-negative, and fungal bacterial species were studied. Nanoparticles with cerium doping showed effective antibacterial and antifungal properties. All samples were tested for bioactivity in simulated body fluid (SBF), and the formation of an apatite layer on their surfaces was highlighted using SEM in conjunction with energy-dispersive X-rays (EDX).Doxorubicin (DOX) release from Ce-HA nanoparticles and pure HA was tested in phosphate-buffered saline (PBS) for up to 28 days. Both nanoparticles were able to release the drug while still being semi-fully loaded. Similarly, the cytotoxic effect of all produced samples on the MG-63 cell line was evaluated, and all samples showed good cytocompatibility. The cytotoxic effect of doxorubicin-loaded nanoparticles showed promising anticancer activity against bone cancer cells, especially samples with high cerium content. The resulting nanoparticles show excellent promising ability for the delivery of doxorubicin to bone cancer with the capacity for bone regeneration.

Bioinspired 3D scaffolds with antimicrobial, drug delivery, and osteogenic functions for bone regeneration

A major clinical challenge today is the large number of bone defects caused by diseases or trauma. The development of three-dimensional (3D) scaffolds with adequate properties is crucial for successful bone repair. In this study, we prepared biomimetic mesoporous bioactive glass (MBG)-based scaffolds with and without ceria addition (up to 3 mol %) to explore the biological structure and chemical composition of the marine sponge Spongia Agaricina (SA) as a sacrificial template. Micro-CT examination revealed that all scaffolds exhibited a highly porous structure with pore diameters primarily ranging from 143.5 μm to 213.5 μm, facilitating bone ingrowth. Additionally, smaller pores (< 75 μm), which are known to enhance osteogenesis, were observed. The undoped scaffold displayed the highest open porosity value of 90.83%. Cytotoxicity assessments demonstrated that all scaffolds were noncytotoxic and nongenotoxic toward osteoblast cells. Moreover, scaffolds with higher CeO2 content promoted osteogenic differentiation of dental pulp stem cells, stimulating calcium and osteocalcin secretion. The scaffolds also exhibited antimicrobial and antibiofilm effects against Staphylococcus aureus (S. aureus) as well as drug delivery ability. Our research findings indicated that the combination of MBG, natural biological structure, and the addition of Ce exhibited a synergistic effect on the structure and biological properties of scaffolds for applications in bone tissue engineering.

Engineering mesoporous bioactive glasses for emerging stimuli-responsive drug delivery and theranostic applications

Mesoporous bioactive glasses (MBGs), which belong to the category of modern porous nanomaterials, have garnered significant attention due to their impressive biological activities, appealing physicochemical properties, and desirable morphological features. They hold immense potential for utilization in diverse fields, including adsorption, separation, catalysis, bioengineering, and medicine. Despite possessing interior porous structures, excellent morphological characteristics, and superior biocompatibility, primitive MBGs face challenges related to weak encapsulation efficiency, drug loading, and mechanical strength when applied in biomedical fields. It is important to note that the advantageous attributes of MBGs can be effectively preserved by incorporating supramolecular assemblies, miscellaneous metal species, and their conjugates into the material surfaces or intrinsic mesoporous networks. The innovative advancements in these modified colloidal inorganic nanocarriers inspire researchers to explore novel applications, such as stimuli-responsive drug delivery, with exceptional in-vivo performances. In view of the above, we outline the fabrication process of calcium-silicon-phosphorus based MBGs, followed by discussions on their significant progress in various engineered strategies involving surface functionalization, nanostructures, and network modification. Furthermore, we emphasize the recent advancements in the textural and physicochemical properties of MBGs, along with their theranostic potentials in multiple cancerous and non-cancerous diseases. Lastly, we recapitulate compelling viewpoints, with specific considerations given from bench to bedside.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

Recent Advances on Cerium Oxide-Based Biomaterials: Toward the Next Generation of Intelligent Theranostics Platforms

Disease or organ damage due to unhealthy living habits, or accidents, is inevitable. Discovering an efficient strategy to address these problems is urgently needed in the clinic. In recent years, the biological applications of nanotechnology have received extensive attention. Among them, as a widely used rare earth oxide, cerium oxide (CeO2 ) has shown good application prospects in biomedical fields due to its attractive physical and chemical properties. Here, the enzyme-like mechanism of CeO2 is elucidated, and the latest research progress in the biomedical field is reviewed. At the nanoscale, Ce ions in CeO2 can be reversibly converted between +3 and +4. The conversion process is accompanied by the generation and elimination of oxygen vacancies, which give CeO2 the performance of dual redox properties. This property facilitates nano-CeO2 to catalyze the scavenging of excess free radicals in organisms, hence providing a possibility for the treatment of oxidative stress diseases such as diabetic foot, arthritis, degenerative neurological diseases, and cancer. In addition, relying on its excellent catalytic properties, customizable life-signaling factor detectors based on electrochemical techniques are developed. At the end of this review, an outlook on the opportunities and challenges of CeO2 in various fields is provided.

Development and Characterization of Electrospun Composites Built on Polycaprolactone and Cerium-Containing Phases

The current study reports on the fabrication of composite scaffolds based on polycaprolactone (PCL) and cerium (Ce)-containing powders, followed by their characterization from compositional, structural, morphological, optical and biological points of view. First, CeO2, Ce-doped calcium phosphates and Ce-substituted bioglass were synthesized by wet-chemistry methods (precipitation/coprecipitation and sol-gel) and subsequently loaded on PCL fibres processed by electrospinning. The powders were proven to be nanometric or micrometric, while the investigation of their phase composition showed that Ce was present as a dopant within the crystal lattice of the obtained calcium phosphates or as crystalline domains inside the glassy matrix. The best bioactivity was attained in the case of Ce-containing bioglass, while the most pronounced antibacterial effect was visible for Ce-doped calcium phosphates calcined at a lower temperature. The scaffolds were composed of either dimensionally homogeneous fibres or mixtures of fibres with a wide size distribution and beads of different shapes. In most cases, the increase in polymer concentration in the precursor solution ensured the achievement of more ordered fibre mats. The immersion in SBF for 28 days triggered an incipient degradation of PCL, evidenced mostly through cracks and gaps. In terms of biological properties, the composite scaffolds displayed a very good biocompatibility when tested with human osteoblast cells, with a superior response for the samples consisting of the polymer and Ce-doped calcium phosphates.

Very Large Pores Mesoporous Silica as New Candidate for Delivery of Big Therapeutics Molecules, Such as Pharmaceutical Peptides

The synthesis of a scaffold that can accommodate big molecules with a pharmaceutical role is important to shield them and maintain their biological activity. In this field, silica particles with large pores (LPMS) are innovative supports. Large pores allow for the loading of bioactive molecules inside the structure and contemporarily their stabilization and protection. These purposes cannot be achieved using classical mesoporous silica (MS, pore size 2-5 nm), because their pores are not big enough and pore blocking occurs. LPMSs with different porous structures are synthesized starting from an acidic water solution of tetraethyl orthosilicate reacting with pore agents (Pluronic^® F127 and mesitylene), performing hydrothermal and microwave-assisted reactions. Time and surfactant optimization were performed. Loading tests were conducted using Nisin as a reference molecule (polycyclic antibacterial peptide, with dimensions of 4-6 nm); UV-Vis analyses on loading solutions were performed. For LPMSs, a significantly higher loading efficiency (LE%) was registered. Other analyses (Elemental Analysis, Thermogravimetric Analysis and UV-Vis) confirmed the presence of Nisin in all the structures and its stability when loaded on them. LPMSs showed a lower decrease in specific surface area if compared to MS; in terms of the difference in LE% between samples, it is explained considering the filling of pores for LPMSs, a phenomenon that is not allowed for MSs. Release studies in simulated body fluid highlight, only for LPMSs, a controlled release, considering the longer time scale of release. Scanning Electron Microscopy images acquired before and after release tests shows the LPMSs' maintenance of the structure, demonstrating strength and mechanical resistance of structures. In conclusion, LPMSs were synthesized, performing time and surfactant optimization. LPMSs showed better loading and releasing properties with respect to classical MS. All collected data confirm a pore blocking for MS and an in-pore loading for LPMS.

The biological functions of europium-containing biomaterials: A systematic review

The biological functions of rare-earth elements (REEs) have become a focus of intense research. Recent studies have demonstrated that ion doping or alloying of some REEs can optimize the properties of traditional biomaterials. Europium (Eu), which is an REE with low toxicity and good biocompatibility, has promising applications in biomedicine. This article systematically reviews the osteogenic, angiogenic, neuritogenic, antibacterial, and anti-tumor properties of Eu-containing biomaterials, thereby paving the way for biomedical applications of Eu. Data collection for this review was completed in October 2022, and 30 relevant articles were finally included. Most articles indicated that doping of Eu ions or Eu-compound nanoparticles in biomaterials can improve their osteogenic, angiogenic, neuritogenic, antibacterial, and anti-tumor properties. The angiogenic, antibacterial, and potential neuritogenic effects of Eu(OH)₃ nanoparticles have also been demonstrated.

Chitosan-polyethylene oxide/clay-alginate nanofiber hydrogel scaffold for bone tissue engineering: Preparation, physical characterization, and biomimetic mineralization

This study aimed to prepare a novel organic-mineral nanofiber/hydrogel of chitosan-polyethylene oxide (CS-PEO)/nanoclay-alginate (NC-ALG). The effects of NC particles on the mineralization and biocompatibility of the scaffold were investigated. A layer-by-layer scaffold composed of CS-PEO and NC-ALG was prepared. The morphological properties, swelling, biodegradation, and mechanical behaviors of the scaffolds were evaluated. Furthermore, scaffolds were characterized by the Fourier Transform Infrared (FTIR), the Field Emission Scanning Electron Microscope (FE-SEM), and X-Ray Diffraction (XRD) techniques. Bone-like apatite formation ability of the scaffolds was determined by the mineralization test in a simulated body fluid (M-SBF). In addition, the crystalline phase of bone-like apatite precipitates was investigated by XRD analysis. The cell compatibility of the scaffolds was also studied with osteoblastic cell line MC3T3-E1 by MTT assay. Notably, the incorporation of NC particles in CS-PEO/ALG scaffolds is suitable for bone tissue regeneration which enhances bone-like apatite formation. Further, the hemolysis and MTT assays demonstrated that CS-PEO/NC-ALG scaffold was compatible and safe for MC3T3 cells.

Thermosensitive PNIPAM-Based Hydrogel Crosslinked by Composite Nanoparticles as Rapid Wound-Healing Dressings

Chronic wounds are prone to produce excessive reactive oxygen species (ROS), which are the main reason for multiple bacterial infections and ulcers at the wound. Therefore, regulating ROS is the key in the process of wound healing. Herein, a new type of thermosensitive hydrogels is developed to improve the scavenging efficiency of ROS and accelerate wound repair. Nano-CeO₂ was uniformly dispersed on the surface of mesoporous silica (MSN). The nanocomposite particles were physically crosslinked with poly(N-isopropylacrylamide) (PNIPAM) to form a MSN-CeO₂@PNIPAM thermoresponsive hydrogel (PMCTH). The stability, temperature sensitivity, rheological properties, biocompatibility, and wound healing ability of the PMCTH were evaluated in detail. The results showed that the hydrogel could not only maintain the stability of the system for a long time with low biological toxicity but also have a phase transition temperature close to the human body temperature. In addition, the PMCTH was directly applied onto the skin surface. The MSN-CeO₂ nanoparticles would be dispersed in the hydrogel to restrict ROS exacerbation effects and promoted the formation of blood vessels as well as surrounding tissues, accelerating the wound healing. More importantly, animal experiments showed that when the mass ratio of CeO₂ to MSN was 40%, the wound healing rate reached up to 78% on the 10th day, which was far higher than that of other experimental groups. This study provides a new strategy and experimental basis for the applications of functional hydrogels in wound repair.

Mesoporous Materials Make Hydrogels More Powerful in Biomedicine

Scientists have been attempting to improve the properties of mesoporous materials and expand their application since the 1990s, and the combination with hydrogels, macromolecular biological materials, is one of the research focuses currently. Uniform mesoporous structure, high specific surface area, good biocompatibility, and biodegradability make the combined use of mesoporous materials more suitable for the sustained release of loaded drugs than single hydrogels. As a joint result, they can achieve tumor targeting, tumor environment stimulation responsiveness, and multiple therapeutic platforms such as photothermal therapy and photodynamic therapy. Due to the photothermal conversion ability, mesoporous materials can significantly improve the antibacterial ability of hydrogels and offer a novel photocatalytic antibacterial mode. In bone repair systems, mesoporous materials remarkably strengthen the mineralization and mechanical properties of hydrogels, aside from being used as drug carriers to load and release various bioactivators to promote osteogenesis. In hemostasis, mesoporous materials greatly elevate the water absorption rate of hydrogels, enhance the mechanical strength of the blood clot, and dramatically shorten the bleeding time. As for wound healing and tissue regeneration, incorporating mesoporous materials can be promising for enhancing vessel formation and cell proliferation of hydrogels. In this paper, we introduce the classification and preparation methods of mesoporous material-loaded composite hydrogels and highlight the applications of composite hydrogels in drug delivery, tumor therapy, antibacterial treatment, osteogenesis, hemostasis, and wound healing. We also summarize the latest research progress and point out future research directions. After searching, no research reporting these contents was found.

Alginate Beads Containing Cerium-Doped Mesoporous Glass and Curcumin: Delivery and Stabilization of Therapeutics

Cancer is a leading cause of death worldwide, its genesis and progression are caused by homeostatic errors, and reactive oxygen species play a major role in promoting aberrant cancer homeostasis. In this scenario, curcumin could be an interesting candidate due to its versatile antioxidant, anti-inflammatory, anti-tumor, anti-HIV, and anti-infection properties. Nonetheless, the major problem related to its use is its poor oral bioavailability, which can be overcome by encapsulating it into small particles, such as hydrogel beads containing mesoporous silica. In this work, various systems have been synthesized: starting from mesoporous silica glasses (MGs), cerium-containing MGs have been produced; then, these systems have been loaded with 4 to 6% of curcumin. Finally, various MGs at different compositions have been included in alginate beads. In vitro studies showed that these hybrid materials enable the stabilization and effective delivery of curcumin and that a synergic effect can be achieved if Ce³⁺/Ce⁴⁺ and curcumin are both part of the beads. From swelling tests, it is possible to confirm a controlled curcumin release compartmentalized into the gastrointestinal tract. For all beads obtained, a curcumin release sufficient to achieve the antioxidant threshold has been reached, and a synergic effect of cerium and curcumin is observed. Moreover, from catalase mimetic activity tests, we confirm the well-known catalytic activity of the couple Ce³⁺/Ce⁴⁺. In addition, an extremely good radical scavenging effect of curcumin has been demonstrated. In conclusion, these systems, able to promote an enzymatic-like activity, can be used as drug delivery systems for curcumin-targeted dosing.

Antioxidant Effects of Bioactive Glasses (BGs) and Their Significance in Tissue Engineering Strategies

Elevated levels of oxidative stress are usually observed following injuries, leading to impaired tissue repair due to oxidation-related chronic inflammation. Several attempts have been made to manage this unfavorable situation, and the use of biomaterials with antioxidant activity is showing great promise in tissue engineering and regenerative medicine approaches. Bioactive glasses (BGs) are a versatile group of inorganic substances that exhibit an outstanding regenerative capacity for both hard and soft damaged tissues. The chemical composition of BGs provides a great opportunity for imparting specific biological activities to them. On this point, BGs may easily become antioxidant substances through simple physicochemical modifications. For example, particular antioxidant elements (mostly cerium (Ce)) can be added to the basic composition of the glasses. On the other hand, grafting natural antioxidant substances (e.g., polyphenols) on the BG surface is feasible for making antioxidant substitutes with promising results in vitro. Mesoporous BGs (MBGs) were demonstrated to have unique merits compared with melt-derived BGs since they make it possible to load antioxidants and deliver them to the desired locations. However, there are actually limited in vivo experimental studies on the capability of modified BGs for scavenging free radicals (e.g., reactive oxygen species (ROS)). Therefore, more research is required to determine the actual potential of BGs in decreasing oxidative stress and subsequently improving tissue repair and regeneration. The present work aims to highlight the potential of different types of BGs in modulating oxidative stress and subsequently improving tissue healing.

Fabrication and characterization of novel polyhydroxybutyrate-keratin/nanohydroxyapatite electrospun fibers for bone tissue engineering applications

The role of scaffolds in bone regeneration is of great importance. Here, the electrospun scaffolds of poly (3-hydroxybutyrate)-keratin (PHB-K)/nanohydroxyapatite (nHA) with different morphologies (long nanorods (HAR) and very short nanorods (HAP)) and weight percentages (up to 10 w/w%) of nHA were fabricated and characterized. The fibers integrity, the porosity of above 80%, and increase in pore size up to 16 μm were observed by adding nHA. The nanofibers crystallinity increased by 13.5 and 22.8% after the addition of HAR and HAP, respectively. The scaffolds contact angle decreased by almost 20° and 40° after adding 2.5 w/w% HAR and HAP, respectively. The tensile strength of the scaffolds increased from 2.99 ± 0.3 MPa for PHB-K to 6.44 ± 0.16 and 9.27 ± 0.04 MPa for the scaffolds containing 2.5 w/w% HAR and HAP, respectively. After immersing the scaffolds into simulated body fluid (SBF), the Ca concentration decreased by 55% for HAR- and 73% for HAP-containing scaffolds, showing the bioactivity of nHA-containing scaffolds. The results of cell attachment, proliferation, and viability of MG-63 cells cultured on the nanocomposites showed the positive effects of nHA. The results indicate that the nanocomposite scaffolds, especially HAP-containing ones, can be suitable for bone tissue engineering applications.

Loading with Biomolecules Modulates the Antioxidant Activity of Cerium-Doped Bioactive Glasses

In order to identify new bioactive glasses (BGs) with optimal antioxidant properties, we carried out an evaluation of a series of cerium-doped BGs [Ce-BGs─H, K, and mesoporous bioactive glasses (MBGs)] loaded with different biomolecules, namely, gallic acid, polyphenols (POLY), and anthocyanins. Quantification of loading at variable times highlighted POLY on MBGs as the system with the highest loading. The ability to dismutate hydrogen peroxide (catalase-like activity) of the BGs evaluated is strongly correlated with cerium doping, while it is marginally decreased compared to the parent BG upon loading with biomolecules. Conversely, unloaded Ce-BGs show only a marginal ability to dismutate the superoxide anion (SOD)-like activity, while upon loading with biomolecules, POLY in particular, the SOD-like activity is greatly enhanced for these materials. Doping with cerium and loading with biomolecules give complementary antioxidant properties to the BGs investigated; combined with the persistent bioactivity, this makes these materials prime candidates for upcoming studies on biological systems.

Cerium-Containing Mesoporous Bioactive Glasses (MBGs)-Derived Scaffolds with Drug Delivery Capability for Potential Tissue Engineering Applications

Finding innovative solutions to improve the lives of people affected by trauma, bone disease, or aging continues to be a challenge worldwide. Tissue engineering is the most rapidly growing area in the domain of biomaterials. Cerium-containing MBG-derived biomaterials scaffolds were synthesized using polymethyl methacrylate (PMMA) as a sacrificial template. The obtained scaffolds were characterized by X-ray powder diffraction (XRPD), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The Ce4+/Ce3+ ratio in the scaffolds was estimated. In vitro testing revealed good cytocompatibility of the investigated scaffolds in mouse fibroblast cell line (NCTC clone L929). The results obtained regarding bioactivity, antibacterial activity, and controlled drug delivery functions recommend these scaffolds as potential candidates for bone tissue engineering applications.

Alginate-based Composites Microspheres: Preparations and Applications for Bone Tissue Engineering

Alginate-based biomaterials have been extensively studied for bone tissue engineering. Scaffolds, microspheres, and hydrogels can be developed using alginate, which is biocompatible, biodegradable, and able to deliver growth factors and drugs. Alginate microspheres can be produced using crosslinking, microfluidic, three-dimensional printing, extrusion, and emulsion methods. The sizes of the alginate microspheres range from 10 µm to 4 mm. This review describes the chemical characterization and mechanical assessment of alginate-based microspheres. Combinations of alginate with hydroxyapatite, chitosan, collagen, polylactic acid, polycaprolactone, and bioglass were discussed for bone tissue repair and regeneration. In addition, alginate combinations with bone morphogenetic proteins, vascular endothelial growth factor, transforming growth factor beta-3, other growth factors, cells, proteins, drugs, and osteoinductive drugs were analyzed for tissue engineering applications. Furthermore, the biocompatibility of developed alginate microspheres was discussed for different cell lines. Finally, alginate microsphere-based composites with stem cell interaction for bone tissue regeneration were presented. In the present review, we have assessed the preclinical research on in vivo models of alginate-based microspheres for bone tissue repair and regeneration. Overall, alginate-based microspheres are potential candidates for graft substitutes and the treatment of various bone-related diseases.

Understanding Reactive Oxygen Species in Bone Regeneration: A Glance at Potential Therapeutics and Bioengineering Applications

Although the complex mechanism by which skeletal tissue heals has been well described, the role of reactive oxygen species (ROS) in skeletal tissue regeneration is less understood. It has been widely recognized that a high level of ROS is cytotoxic and inhibits normal cellular processes. However, with more recent discoveries, it is evident that ROS also play an important, positive role in skeletal tissue repair, specifically fracture healing. Thus, dampening ROS levels can potentially inhibit normal healing. On the same note, pathologically high levels of ROS cause a sharp decline in osteogenesis and promote nonunion in fracture repair. This delicate balance complicates the efforts of therapeutic and engineering approaches that aim to modulate ROS for improved tissue healing. The physiologic role of ROS is dependent on a multitude of factors, and it is important for future efforts to consider these complexities. This review first discusses how ROS influences vital signaling pathways involved in the fracture healing response, including how they affect angiogenesis and osteogenic differentiation. The latter half glances at the current approaches to control ROS for improved skeletal tissue healing, including medicinal approaches, cellular engineering, and enhanced tissue scaffolds. This review aims to provide a nuanced view of the effects of ROS on bone fracture healing which will inspire novel techniques to optimize the redox environment for skeletal tissue regeneration.

Mesoporous Bioglasses Enriched with Bioactive Agents for Bone Repair, with a Special Highlight of María Vallet-Regí’s Contribution

Throughout her impressive scientific career, Prof. María Vallet-Regí opened various research lines aimed at designing new bioceramics, including mesoporous bioactive glasses for bone tissue engineering applications. These bioactive glasses can be considered a spin-off of silica mesoporous materials because they are designed with a similar technical approach. Mesoporous glasses in addition to SiO₂ contain significant amounts of other oxides, particularly CaO and P₂O₅ and therefore, they exhibit quite different properties and clinical applications than mesoporous silica compounds. Both materials exhibit ordered mesoporous structures with a very narrow pore size distribution that are achieved by using surfactants during their synthesis. The characteristics of mesoporous glasses made them suitable to be enriched with various osteogenic agents, namely inorganic ions and biopeptides as well as mesenchymal cells. In the present review, we summarize the evolution of mesoporous bioactive glasses research for bone repair, with a special highlight on the impact of Prof. María Vallet-Regí´s contribution to the field.

Rare earth smart nanomaterials for bone tissue engineering and implantology: Advances, challenges, and prospects

Bone grafts or prosthetic implant designing for clinical application is challenging due to the complexity of integrated physiological processes. The revolutionary advances of nanotechnology in the biomaterial field expedite and endorse the current unresolved complexity in functional bone graft and implant design. Rare earth (RE) materials are emerging biomaterials in tissue engineering due to their unique biocompatibility, fluorescence upconversion, antimicrobial, antioxidants, and anti-inflammatory properties. Researchers have developed various RE smart nano-biomaterials for bone tissue engineering and implantology applications in the past two decades. Furthermore, researchers have explored the molecular mechanisms of RE material-mediated tissue regeneration. Recent advances in biomedical applications of micro or nano-scale RE materials have provided a foundation for developing novel, cost-effective bone tissue engineering strategies. This review attempted to provide an overview of RE nanomaterials' technological innovations in bone tissue engineering and implantology and summarized the osteogenic, angiogenic, immunomodulatory, antioxidant, in vivo bone tissue imaging, and antimicrobial properties of various RE nanomaterials, as well as the molecular mechanisms involved in these biological events. Further, we extend to discuss the challenges and prospects of RE smart nano-biomaterials in the field of bone tissue engineering and implantology.

Anti-inflammatory and antibacterial activities of cerium-containing mesoporous bioactive glass nanoparticles for drug-free biomedical applications

Mesoporous bioactive glass nanoparticles (MBGNPs) are attracting significant attention as suitable materials for multifunctional biomedical applications. In this study, cerium was incorporated into MBGNPs using two different approaches. In the first approach, cerium was added to the glass system directly during the synthesis, while in the second approach, cerium was added to the as-synthesized MBGNPs via the template ion-exchange method. The influence of the method of synthesis on the physicochemical properties of nanoparticles was examined by SEM, TEM, XRD, FTIR, and N₂ adsorption-desorption analyses. The MBGNPs exhibited spheroidal morphology and disordered mesoporous structure. XRD analysis confirmed the amorphous nature of the nanoparticles. The chemical composition was determined by the acid digestion method using ICP-OES. The influence of the synthesis method on the specific surface area, mesoporosity, and solubility of synthesized nanoparticles in Tris/HCl (pH 7.4) and acetate (pH 4.5) buffer has also been studied. The obtained Ce containing MBGNPs were non-cytotoxic toward ​preosteoblast MC3T3-E1 cells in contact with nanoparticles in a concentration of up to 100 ​μg/mL. The anti-inflammatory effect of Ce containing MBGNPs was tested with lipopolysaccharides (LPS)-induced proinflammatory RAW 264.7 macrophage cells. Ce containing MBGNPs decreased the release of nitric oxide, indicating the anti-inflammatory response of macrophage cells. Ce containing MBGNPs also showed antibacterial activity against S. aureus and E. coli. The mentioned features of the obtained MBGNPs make them useful in a variety of biomedical applications, considering their biocompatibility, anti-inflammatory response, and enhanced antibacterial effect.

Cerium Containing Bioactive Glasses: A Review

Bioactive glasses (BGs) for biomedical applications are doped with therapeutic inorganic ions (TIIs) in order to improve their performance and reduce the side effects related to the surgical implant. Recent literature in the field shows a rekindled interest toward rare earth elements, in particular cerium, and their catalytic properties. Cerium-doped bioactive glasses (Ce-BGs) differ in compositions, synthetic methods, features, and in vitro assessment. This review provides an overview on the recent development of Ce-BGs for biomedical applications and on the evaluation of their bioactivity, cytocompatibility, antibacterial, antioxidant, and osteogenic and angiogenic properties as a function of their composition and physicochemical parameters.

Antioxidant cerium ions-containing mesoporous bioactive glass ultrasmall nanoparticles: Structural, physico-chemical, catalase-mimic and biological properties

The multifunctional biological properties of Ce ions including antioxidant, anti-inflammatory, antibacterial and anti-cancer effects are very encouraging for development of Ce-containing biomaterials with therapeutic properties. Herein, novel Ce³⁺/Ce⁴⁺ ions containing mesoporous bioactive glass ultrasmall nanoparticles (Ce-BGn) were prepared by a facile one-pot ultrasound-assisted sol-gel method. Interestingly, Ce₂O₃ incorporation exerted a significant influence on the particle size and textural properties of mesoporous BGn (SiO₂ - CaO binary glass system). Ce-BGn exhibited ultrasmall nanoparticle size (< 30 nm), mesoporous texture (pore size up to 2.82 nm and pore volume up to 0.191 cm³/g) and large specific surface area ca. 132.9 m²/g. Notably, in situ formation of CeO₂ nanospheres (3-6 nm) was detected at the surface and in the amorphous glass matrix of mesoporous Ce-BGn. Importantly, X-ray photoelectron spectroscopy (XPS) revealed the presence of 72.57 % Ce³⁺ and 27.43 % Ce⁴⁺ at the surface of mesoporous Ce-BGn with Ce³⁺/Ce⁴⁺ ratio = 2.66. Furthermore, mesoporous Ce-BGn exhibited high catalase-mimic activity and showed sustained release of Ce (2.5-32 ppm), Ca (85-327 ppm) and Si (54-200 ppm) ions within 4 weeks along with excellent bone-like hydroxyapatite formation. Finally, the in vitro biological behavior of mesoporous Ce-BGn in cell cultures of human skin fibroblasts (HSF) revealed that mesoporous Ce-BGn (with concentrations up to 300 μg/mL) possess good cyto-biocompatibility. Taken together, novel ultrasmall mesoporous Ce-BGn showed remarkable catalase-mimic activity via surface containing Ce³⁺/Ce⁴⁺ ions which can scavenge ROS (Ce³⁺↔ Ce⁴⁺) and decompose H₂O₂ molecules into H₂O and O₂. In addition to that, Ce-BGn demonstrated sustained release of bioactive ions (Ce, Ca and Si), excellent bone-like hydroxyapatite formation and good cyto-biocompatibility.

Mesoporous bioactive glasses for regenerative medicine

Stem cells are the central element of regenerative medicine (RM). However, in many clinical applications, the use of scaffolds fabricated with biomaterials is required. In this sense, mesoporous bioactive glasses (MBGs) are going to play an important role in bone regeneration because of their striking textural properties, quick bioactive response, and biocompatibility. As other bioactive glasses, MBGs are mainly formed by silicon, calcium, and phosphorus oxides whose ions play an important role in cell proliferation as well as in homeostasis and bone remodeling process. A common improvement of bioactive glasses for RM is by adding small amounts of oxides of elements that confer them additional biological capacities, including osteogenic, angiogenic, antibacterial, anti-inflammatory, hemostatic, or anticancer properties. Moreover, MBGs are versatile in terms of the different ways in which they can be processed, such as scaffolds, fibers, coatings, or nanoparticles. MBGs are unique because their textural properties are so high that they still exhibit outstanding bioactive responses even after adding extra inorganic ions or being processed as scaffolds or nanoparticles. Moreover, they can be further improved by loading with biomolecules, drugs, and stem cells. This article reviews the state of the art and future perspectives of MBGs in the field of RM of hard tissues.

Improved osteogenesis and angiogenesis of theranostic ions doped calcium phosphates (CaPs) by a simple surface treatment process: A state-of-the-art study

Surface treatment of biomaterials could enable reliable and quick cellular responses and accelerate the healing of the host tissue. Here, a series of calcium phosphates (CaPs) were surface treated by hydrogen peroxide (H₂O₂) and the treatment effects were physicochemically and biologically evaluated. For this aim, as-synthesized CaPs doped with strontium (Sr²⁺), iron (Fe²⁺), silicon (Si⁴⁺), and titanium (Ti⁴⁺) ions were sonicated in H₂O₂ media. The results showed that the specific surface area and zeta potential values of the surface-treated CaPs were increased by ~50% and 25%, respectively. Moreover, the particle size and the band-gap (Eg) values of the surface-treated CaPs were decreased by ~25% and ~2-10%, respectively. The concentration of oxygen vacancies was increased in the surface-treated samples, which was confirmed by the result of ultraviolet (UV), photoluminescence (PL), Commission Internationale de l'éclairage (CIE 1931), and X-ray photoelectron spectroscopy (XPS) analyses. In vitro cellular assessments of surface-treated CaPs exhibited an improvement in cytocompatibility, reactive oxygen species generation (ROS) capacity, bone nodule formation, and the migration of cells up to ~8%, 20%, 35%, and 13%, respectively. Based on the obtained data, it can be stated that improved physicochemical properties of H₂O₂-treated CaPs could increase the ROS generation and subsequently enhance the biological activities. In summary, the results demonstrate the notable effect of the H₂O₂ surface treatment method on improving surface properties and biological performance of CaPs.

Cerium and gallium containing mesoporous bioactive glass nanoparticles for bone regeneration: Bioactivity, biocompatibility and antibacterial activity

In recent years, mesoporous bioactive glass nanoparticles (MBGNPs) have generated great attention in biomedical applications. In this study, cerium and gallium doped MBGNPs were prepared by microemulsion assisted sol-gel method in the binary SiO₂-CaO system. MBGNPs with spheroidal and pineal shaped morphology were obtained. Nitrogen sorption analysis elucidated the mesoporous structure of synthesized nanoparticles with high specific surface area. X-ray diffraction analysis confirmed the amorphous nature of the nanoparticles. The chemical compositions of all samples were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), which revealed that the contents of cerium and gallium could be tailored by adjusting the concentrations of the precursors used for the synthesis. All MBGNPs exhibited in vitro bioactivity when immersed in simulated body fluid, except the particles doped with higher amounts than 1 mol% of cerium. MBGNPs showed antibacterial activity against S. aureus and E. coli without exhibiting cytotoxicity towards MG-63 osteoblast-like cells. Mentioned features of the obtained Ce and Ga-doped MBGNPs make them useful for multifunctional applications such as drug delivery carriers or bioactive fillers for bone tissue engineering applications.

In vitro genotoxicity assessment and comparison of cerium (IV) oxide micro- and nanoparticles

Cerium (IV) oxide (CeO₂), which is used as a biomaterial, has wide application in areas such as the biomedical, glass polishing, electronic, automotive, and pharmacology industries. Comparing with the literature, in this study, the genotoxic effects of cerium (IV) oxide microparticles (COMPs) and cerium (IV) oxide nanoparticles (CONPs) were investigated for the first time in human peripheral blood cultures at concentrations of 0.78, 1.56, 3.125, 6.25, 12.5, 25, and 50 ppm for 72 h under in vitro conditions. Particle sizes of COMPs and CONPs were determined using scanning electron microscopic analysis. Micronucleus and chromosome aberration tests were used to determine the genotoxicity of COMPs and CONPs. The average particle sizes of COMPs and CONPs were approximately 148.25 and 25.30 nm, respectively. It was determined that CeO₂ particles in both micro and nano sizes were toxic at all concentrations compared to the negative control group (distilled water). Importantly, COMPs and CONPs were genotoxic even at the lowest concentration (0.78 ppm). Comparing particle sizes, the data indicated that COMPs were more toxic than CONPs. The results suggest that genotoxicity of COMPs and CONPs may be a function of applied concentrations and particle sizes.

Tellurium: A new active element for innovative multifunctional bioactive glasses

Bioactive glasses have been widely investigated for their ability to release ions with therapeutic effect. In this paper, a silica based bioactive glass was doped with a low amount of tellurium dioxide (1 and 5 mol%) to confer antibacterial and antioxidant properties. The obtained glasses were characterized in terms of morphology, composition, structure, characteristic temperatures and in vitro bioactivity. Moreover, comprehensive analyses were carried out to estimate the cytocompatibility, the antibacterial and antioxidant properties of Te-doped glasses. The performed characterizations demonstrated that the Te insertion did not interfere with the amorphous nature of the glass, the substitution of SiO₂ with TeO₂ led to a slight decrease in T_g and a TeO₂ amount higher than 1 mol% can induce a change in the primary crystal field. In vitro bioactivity test demonstrated the Te-doped glass ability to induce the precipitation of hydroxyapatite. Finally, the biological characterization showed a strong antibacterial and antioxidant effects of Te-containing glasses in comparison with the control glass, demonstrating that Te is a promising element to enhance the biological response of biomaterials.

Mesoporous Bioactive Glasses Cytocompatibility Assessment: A Review of In Vitro Studies

Thanks to their high porosity and surface area, mesoporous bioactive glasses (MBGs) have gained significant interest in the field of medical applications, in particular, with regards to enhanced bioactive properties which facilitate bone regeneration. The aim of this article is to review the state of the art regarding the biocompatibility evaluation of MBGs and provide a discussion of the various approaches taken. The research was performed using PubMed database and covered articles published in the last five years. From a total of 91 articles, 63 were selected after analyzing them according to our inclusion and exclusion criteria. In vitro methodologies and techniques used for biocompatibility assessment were investigated. Among the biocompatibility assessment techniques, scanning electron microscopy (SEM) has been widely used to study cell morphology and adhesion. Viability and proliferation were assessed using different assays including cell counting and/or cell metabolic activity measurement. Finally, cell differentiation tests relied on the alkaline phosphatase assay; however, these were often complemented by specific bimolecular tests according to the exact application of the mesoporous bioactive glass. The standardization and validation of all tests performed for MBG cytocompatibility is a key aspect and crucial point and should be considered in order to avoid inconsistencies, bias between studies, and unnecessary consumption of time. Therefore, introducing standard tests would serve an important role in the future assessment and development of MBG materials.

Cell Proliferation to Evaluate Preliminarily the Presence of Enduring Self-Regenerative Antioxidant Activity in Cerium Doped Bioactive Glasses

(1) Background: a cell evaluation focused to verify the self-regenerative antioxidant activity is performed on cerium doped bioactive glasses. (2) Methods: the glasses based on 45S5 Bioglass^®, are doped with 1.2 mol%, 3.6 mol% and 5.3 mol% of CeO₂ and possess a polyhedral shape (~500 µm²). Glasses with this composition inhibit oxidative stress by mimicking catalase enzyme (CAT) and superoxide dismutase (SOD) activities; moreover, our previous cytocompatibility tests (neutral red (NR), 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Bromo-2-deoxyUridine (BrdU)) reveal that the presence of cerium promotes the absorption and vitality of the cells. The same cytocompatibility tests were performed and repeated, in two different periods (named first and second use), separated from each other by four months. (3) Results: in the first and second use, NR tests indicate that the presence of cerium promotes once again cell uptake and viability, especially after 72 h. A decrease in cell proliferation it is observed after MTT and BrdU tests only in the second use. These findings are supported by statistically significant results (4) Conclusions: these glasses show enhanced proliferation, both in the short and in the long term, and for the first time such large dimensions are studied for this kind of study. A future prospective is the implantation of these bioactive glasses as bone substitute in animal models.

Strontium- and Cobalt-Doped Multicomponent Mesoporous Bioactive Glasses (MBGs) for Potential Use in Bone Tissue Engineering Applications

Mesoporous bioactive glasses (MBGs) offer suitable platforms for drug/ion delivery in tissue engineering strategies. The main goal of this study was to prepare strontium (Sr)- and cobalt (Co)-doped MBGs; strontium is currently used in the treatment of osteoporosis, and cobalt is known to exhibit pro-angiogenic effects. Sr- and Co-doped mesoporous glasses were synthesized for the first time in a multicomponent silicate system via the sol-gel method by using P123 as a structure-directing agent. The glassy state of the Sr- and Co-doped materials was confirmed by XRD before immersion in SBF, while an apatite-like layer was detected onto the surface of samples post-immersion. The textural characteristics of MBGs were confirmed by nitrogen adsorption/desorption measurements. In vitro experiments including MTT assay, Alizarin red staining, and cell attachment and migration showed the cytocompatibility of all the samples as well as their positive effects on osteoblast-like cell line MG-63. Early experiments with human umbilical vein endothelial cells also suggested the potential of these MBGs in the context of angiogenesis. In conclusion, the prepared materials were bioactive, showed the ability to improve osteoblast cell function in vitro and could be considered as valuable delivery vehicles for therapeutics, like Co2+ and Sr2+ ions.

Cerium Dioxide Particles to Tune Radiopacity of Dental Adhesives: Microstructural and Physico-Chemical Evaluation

The insufficient radiopacity of dental adhesives applied under composite restorations makes the radiographic diagnosis of recurrent caries challenging. Consequently, the misdiagnosis may lead to unnecessary replacement of restorations. The aims of this study were to formulate experimental dental adhesives containing cerium dioxide (CeO₂) and investigate the effects of different loadings of CeO₂ on their radiopacity and degree of conversion for the first time. CeO₂ was characterized by X-ray diffraction analysis, Fourier transforms infrared spectroscopy, and laser diffraction for particle size analysis. Experimental dental adhesives were formulated with CeO₂ as the inorganic filler with loadings ranging from 0.36 to 5.76 vol.%. The unfilled adhesive was used as a control. The studied adhesives were evaluated for dispersion of CeO₂ in the polymerized samples_, degree of conversion, and radiopacity. CeO₂ presented a monoclinic crystalline phase, peaks related to Ce-O bonding, and an average particle size of around 16 µm. CeO₂ was dispersed in the adhesive, and the addition of these particles increased the adhesives’ radiopacity (p < 0.05). There was a significant decrease in the degree of conversion with CeO₂ loadings higher than 1.44 vol.%. However, all materials showed a similar degree of conversion in comparison to commercially available adhesives. CeO₂ particles were investigated for the first time as a promising compound to improve the radiopacity of the dental adhesives.

Antioxidant mesoporous Ce-doped bioactive glass nanoparticles with anti-inflammatory and pro-osteogenic activities

Mesoporous bioactive glass nanoparticles (MBGNs) are emerging biomaterials for bone repair/regeneration, considering their favorable pro-osteogenic and proangiogenic activities. To further improve their therapeutic effects, the endowment of MBGNs with additional antioxidant properties is of particular interest to target oxidative stress related to bone remodeling and diseases. To this end, we developed antioxidant cerium-containing MBGNs (Ce-MBGNs) (particle size of 100-300 ​nm) by using a postimpregnation strategy to incorporate Ce, through which the shape, pore structure, and dispersity of the nanoparticles were preserved. The incorporated amount of Ce could be tailored by adjusting the concentration of the Ce precursor solution. When impregnated at a relatively low temperature (20 ​°C), Ce-MBGNs containing either 1.8 or 2.8 ​mol% of Ce were produced, while the formation of by-product cerium oxide nanoparticles (nanoceria) could be avoided. In both developed Ce-MBGNs, the concentration of Ce4+ was higher than that of Ce3+, while the relative molar percentage of Ce4+ was similar (∼74%) in both Ce-MBGNs. The obtained Ce-MBGNs were evidenced to be non-cytotoxic against fibroblasts at the concentration of 1 ​mg/mL. Moreover, the incorporation of Ce into MBGNs significantly reduced the expression of oxidative stress-related genes in macrophages (J774a.1). Particularly in the presence of pro-oxidation agents, Ce-MBGNs could downregulate the expression of oxidative stress-related genes in comparsion with the polystyrene plates (control). When cultured with Ce-MBGNs, the expression of proinflammatory-related genes in macrophages could also be downregulated in comparsion with MBGNs and the control. Ce-MBGNs also exhibited pro-osteogenic activities through suppressing pro-osteoclastogenic responses. The obtained results highlight the great potential of the developed Ce-MBGNs in a variety of biomedical applications, particularly in treating bone defects under inflammatory conditions, considering their antioxidant, anti-inflammatory, and pro-osteogenesis activities.

P2O5-Free Cerium Containing Glasses: Bioactivity and Cytocompatibility Evaluation

(1) Background: valuation of the bioactivity and cytocompatibility of P₂O₅-free and CeO₂ doped glasses. (2) Methods: all glasses are based on the Kokubo (K) composition and prepared by a melting method. Doped glassed, K1.2, K3.6 and K5.3 contain 1.2, 3.6, and 5.3 mol% of CeO₂. Bioactivity and cytotoxicity tests were carried out in simulated body fluid (SBF) solution and murine osteocyte (MLO-Y4) cell lines, respectively. Leaching of ions concentration in SBF was determined by inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES). The surface of the glasses were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. (3) Results: P₂O₅-free cerium doped glasses are proactive according to European directives. Cerium increases durability and retards, but does not inhibit, (Ca₁₀(PO₄)₆(OH)₂, HA) formation at higher cerium amounts (K3.6 and K5.3); however, cell proliferation increases with the amount of cerium especially evident for K5.3. (4) Conclusions: These results enforce the use of P₂O₅-free cerium doped bioactive glasses as a new class of biomaterials.