Co-incorporation of strontium and fluorine into diopside scaffolds: Bioactivity, biodegradation and cytocompatibility evaluations

Development and characterization of nano-hydroxyapatite/gelatin/PVA/alginate-based multifunctional active scaffolds for bone regeneration: An in vitro and in vivo study

Multifunctional porous bone scaffolds that combine reparative and therapeutic features are promising for bone tissue engineering applications. Therefore, we developed freeze-dried scaffolds based on the in situ synthesis of hydroxyapatite nanoparticles (HAp NPs) within a gelatin-polyvinyl alcohol (PVA)-alginate matrix using a co-precipitation method. Ceftazidime and 5-fluorouracil (5-FU) were used as drug models and were separately loaded into the fabricated scaffolds. The hybrid scaffolds exhibited an ultimate compressive strength of 1.1 MPa and flexible behavior favored for fitting irregular bone defects. 5-FU-loaded scaffolds showed higher bioactive potential within 3 days compared to ceftazidime-loaded scaffolds. The scaffolds exhibited a long-term degradation rate, and thereby prolonged release of ceftazidim and 5-FU for up to 28 days. 5-FU-loaded scaffolds showed excellent nearly equal antibacterial activity to ceftazidime-loaded scaffolds against Staphylococcus epidermidis and Escherichia coli strains. Osteosarcoma cell death was achieved by increased concentrations of ceftazidime and 5-FU treatment above 300 μg/mL and 250 μg/mL, respectively. The developed scaffolds displayed higher bone formation ability with better osteogenesis in a femoral rat bone defect model compared to the control sample. This work represents a promising solution for bone defect repair and provides insight into the development of multifunctional scaffolds for local chemotherapy and bone tissue engineering applications.

Surface prereacted glass-ionomer particles incorporated into resin composites promote biocompatibility for restoration of subgingival dental defects

Subgingival dental defects are common in clinical practice among patients with deep dental caries and dental fractures. These defects commonly accompany lesions involving marginal alveolar bone loss and gingival recession, and their clinical management is challenging. Restoring gingival adhesion and activating the regeneration of periodontal tissue are important for a better prognosis in these cases. However, there is no effective resin material for complex restorations involving the destruction of subgingival tissue. To achieve greater biocompatibility, resins are generally modified with bioactive particles that can release specific components. Surface prereacted glass ionomer (S-PRG) is a novel glass particle characterized by a three-layered structure and the release of multiple ions with bioactive potential. Therefore, in this study, we incorporated S-PRG filler into resin-based composites to investigate their effectiveness in the restoration of subgingival defects. Resin composites containing 0, 10, 30, 50, or 70 wt% S-RPG filler were fabricated and formed into material discs, where a commercial resin composite served as the control group. The microstructure and elemental distribution were characterized by scanning electronic microscopy and energy-dispersive spectroscopy. The resin composites containing 50 or 70 wt% S-PRG fillers exhibited comprehensively better physicochemical properties, including flexural modulus, compressive strength, and water sorption. The ion release profile and environmental pH of the resins were measured with material extracts. Periodontal ligament stem cells were considered as seed cells that harbored great potential for periodontal regeneration. Cellular experiments suggested that S-PRG promotes cell proliferation and adhesion, induces cell migration, and stimulates vascularized osteogenesis. The feasibility of using S-PRG-containing resin composite to rectify subgingival dental defects was confirmed in vivo. After restoration with the S-PRG-filled resin material, intact epithelial tissue adhered to the resin surface with no visible inflammation. In conclusion, S-PRG-filled resin composites showed some biocompatibility as an alternative material for clinical applications.

Investigation to Understand the Role of Phase Variation in Red Emitting Eu3+-Doped Calcium Magnesium Silicate Phosphor for In Vitro Bioimaging

Eu3+-doped silicate phosphors are gaining significant attention for bioimaging and scaffold development due to their narrow red emission, high color purity, quantum yield (QY), and large Stokes shift. These phosphors offer several advantages over conventional imaging techniques, such as good selectivity and sensitivity, simpler operation, reduced data acquisition time, cost-effectiveness, and nondestructive imaging. The luminescence properties of these phosphors can be enhanced by modifying synthesis methods, annealing conditions, and hosts and introducing multiple dopants. This study explores a novel approach for improving luminescence by modifying the crystal structures of Eu3+ doped calcium magnesium silicate (CMS:Eu3+) phosphors for in vitro bioimaging and potential scaffold development. The synthesized diopside (CaMgSi2O6:xEu3+; x = 10, 15, and 20 mol %), merwinite (Ca3MgSi2O8:15 mol % Eu3+), and akermanite (Ca2MgSi2O7:15 mol % Eu3+) phases of CMS:Eu3+ exhibit distinct coordination environments for Eu3+, leading to unique excitation wavelength tunability from ultraviolet (UV) to the visible region, high emission intensity, decay time, QY > 40%, and color purity >83%. A comparative analysis of their structural and photoluminescence properties reveals the impact of phase modifications on luminescence for in vitro bioimaging by optimizing the dopant concentration. The results indicate that CaMgSi2O6: 15 mol % Eu3+ is the most efficient phosphor for in vitro bioimaging, with the highest relative emission intensity in the red region, decay time ∼2 ms, QY ∼ 77%, and color purity ∼86%. The unique morphology of Ca3MgSi2O8:15 mol %Eu3+ and Ca2MgSi2O7:15 mol % Eu3+ also supports cell adhesion, suggesting their potential in scaffold development. In brief, the study highlights the potential of CMS:Eu3+ phosphors for in vitro bioimaging and scaffold development by modifying phases and dopant concentrations.

Ion release, cytocompatibility and microbial inhibition of a novel varnish containing fluoride-doped bioactive glass ceramics: an in vitro study

OBJECTIVES

The study aimed to develop and evaluate in vitro a varnish containing fluoride-doped glass ceramics capable of inhibiting oral microorganisms, releasing hydroxyapatite-forming ions, and ensuring biocompatibility.

MATERIALS AND METHODS

For the production of the experimental varnish (VE), composed of hydrogenated rosin, 10% and 20% by weight of glass ceramics with composition S53P4 (CF0) and doped with F- ions (CF5 and CF10) were incorporated. The EVs were characterized by Rheology, Scanning Electron Microscopy (SEM), FTIR, ion release (fluoride and calcium ions), cytotoxicity on VERO cells, and antimicrobial effect on S. mutans, S. aureus and C. albicans and anti-biofilm effect on S. mutans. The data were analyzed by One-Way ANOVA and Kruskal-Wallis test (P = 0.05).

RESULTS

Homogeneous varnishes with good viscosity were obtained. Varnishes with 20% CF demonstrated biocompatibility and minimum inhibitory concentration (MIC) at concentrations lower than 10 mg/mL and 3.12 mg/mL, respectively, except for C. albicans. An anti-biofilm effect on S. mutans was observed for the varnishes with 20% CF. All varnishes with CF released more F- than the commercial varnish, with V20CF10 standing out, which released 4 times more F- ions in a quarter of the time.

CONCLUSIONS

The V20CF10 varnish is a promising material for dental use in the treatment of early caries lesions, due to its biocompatibility, antimicrobial properties, and release of hydroxyapatite-forming ions.

CLINICAL RELEVANCE

The use of a new varnish that combines antimicrobial properties with hydroxyapatite-forming ion release may prevent or halt the progression of dental caries lesions, offering greater efficacy than currently available varnishes.

Phase transformation and mechanical properties of new bioactive glass-ceramics derived from CaO-P2O5-Na2O-B2O3-SiO2 glass system

This work investigates the role of sintering temperature on bioactive glass-ceramics derived from the new composition CaO-P2O5-Na2O-B2O3-SiO2 glass system. The sintering behaviour of the samples' physical, structural, and mechanical properties is highlighted in this study. The experimental results indicated that the sintering process improved the crystallization and hardness of the final product. Results from XRD and FTIR showed the existence of carbonate apatite, pseudo-wollastonite, and wollastonite phases. From the results, the bioglass-ceramics sintered at 700 °C obtained the highest densification and optimum mechanical results. It had the value of 5.34 ± 0.21 GPa regarding microhardness and 2.99 ± 0.24 MPa m1/2 concerning fracture toughness, which falls in the range of the human enamel. Also, the sintered samples maintained their bioactivity and biodegradability after being tested in the PBS medium. The bioactivity does not affect but slows down the apatite formation rate. Overall results promoted the novel bioglass-ceramics as a candidate material for dental application.

Advanced applications of strontium-containing biomaterials in bone tissue engineering

Strontium (Sr) and strontium ranelate (SR) are commonly used therapeutic drugs for patients suffering from osteoporosis. Researches have showed that Sr can significantly improve the biological activity and physicochemical properties of materials in vitro and in vivo. Therefore, a large number of strontium containing biomaterials have been developed for repairing bone defects and promoting osseointegration. In this review, we provide a comprehensive overview of Sr-containing biomaterials along with the current state of their clinical use. For this purpose, the different types of biomaterials including calcium phosphate, bioactive glass, and polymers are discussed and provided future outlook on the fabrication of the next-generation multifunctional and smart biomaterials.

Core-shell bioceramic fiber-derived biphasic granules with adjustable core compositions for tuning bone regeneration efficacy

Silicate-based biomaterials-clinically applied fillers and promising candidates-can act as a highly biocompatible substrate for osteostimulative osteogenic cell growth in vitro and in vivo. These biomaterials have been proven to exhibit a variety of conventional morphologies in bone repair, including scaffolds, granules, coatings and cement pastes. Herein, we aim to develop a series of novel bioceramic fiber-derived granules with core-shell structures which have a hardystonite (HT) shell layer and changeable core components-that is, the chemical compositions of a core layer can be tuned to include a wide range of silicate candidates (e.g., wollastonite (CSi)) with doping of functional ions (e.g., Mg, P, and Sr). Meanwhile, it is versatile to control the biodegradation and bioactive ion release sufficiently for stimulating new bone growth after implantation. Our method employs rapidly gelling ultralong core-shell CSi@HT fibers derived from different polymer hydrosol-loaded inorganic powder slurries through the coaxially aligned bilayer nozzles, followed by cutting and sintering treatments. It was demonstrated that the nonstoichiometric CSi core component could contribute to faster bio-dissolution and biologically active ion release in tris buffer in vitro. The rabbit femoral bone defect repair experiments in vivo indicated that core-shell bioceramic granules with an 8% P-doped CSi-core could significantly stimulate osteogenic potential favorable for bone repair. It is worth concluding that such a tunable component distribution strategy in fiber-type bioceramic implants may develop new-generation composite biomaterials endowed with time-dependent biodegradation and high osteostimulative activities for a range of bone repair applications in situ.

Composite Fibers Based on Polycaprolactone and Calcium Magnesium Silicate Powders for Tissue Engineering Applications

The present work reports the synthesis and characterization of polycaprolactone fibers loaded with particulate calcium magnesium silicates, to form composite materials with bioresorbable and bioactive properties. The inorganic powders were achieved through a sol-gel method, starting from the compositions of diopside, akermanite, and merwinite, three mineral phases with suitable features for the field of hard tissue engineering. The fibrous composites were fabricated by electrospinning polymeric solutions with a content of 16% polycaprolactone and 5 or 10% inorganic powder. The physico-chemical evaluation from compositional and morphological points of view was followed by the biological assessment of powder bioactivity and scaffold biocompatibility. SEM investigation highlighted a significant reduction in fiber diameter, from around 3 μm to less than 100 nm after the loading stage, while EDX and FTIR spectra confirmed the existence of embedded mineral entities. The silicate phases were found be highly bioactive after 4 weeks of immersion in SBF, enriching the potential of the polymeric host that provides only biocompatibility and bioresorbability. Moreover, the cellular tests indicated a slight decrease in cell viability over the short-term, a compromise that can be accepted if the overall benefits of such multifunctional composites are considered.

Improvement of mechanical and antibacterial properties of porous nHA scaffolds by fluorinated graphene oxide

Nano-hydroxyapatite (nHA) is widely used as a bio-scaffold material due to its good bioactivity and biocompatibility. In this study, fluorinated graphene oxide (FG) was added to nHA to improve its poor formability, weak mechanical properties, undesirable antimicrobial activity and other disadvantages that affect its clinical application. FG was synthesized by a simple hydrothermal method. Novel porous composite scaffolds were prepared by adding different weight ratios (0.1 wt%, 0.5 wt% and 1 wt%) of FG to nHA using the 3D printing technique. The morphology, phase composition and mechanical properties of the composite scaffolds were characterized. In addition, the degradation performance of the composite scaffolds, antibacterial activity against Staphylococcus aureus and Escherichia coli, and cytocompatibility were also investigated. The results showed that the nHA/FG composite scaffold was successfully prepared with a uniform distribution of FG on the scaffold. The mechanical properties showed that the compression strength of the nHA/FG composite scaffold was significantly higher than that of the nHA scaffold (7.22 ± 1.43 MPa). The porosity of all composite scaffolds was above 70%. The addition of FG significantly improved the mechanical properties of the nHA scaffold without affecting the porosity of the scaffold. In addition, the 0.5 wt% nHA/FG scaffold exhibited satisfactory cytocompatibility and antibacterial properties. Therefore, the constructed nHA/FG composite scaffold can be considered as a novel antimicrobial bone substitute material with good application prospects.

Nano-hydroxyapatite (nHA) is widely used as a bio-scaffold material. In this study, fluorinated graphene oxide (FG) was added to nHA to improve its poor formability, weak mechanical properties and undesirable antimicrobial activity that affect its clinical application.

Nano-needle strontium-substituted apatite coating enhances osteoporotic osseointegration through promoting osteogenesis and inhibiting osteoclastogenesis

Implant loosening remains a major clinical challenge for osteoporotic patients. This is because osteoclastic bone resorption rate is higher than osteoblastic bone formation rate in the case of osteoporosis, which results in poor bone repair. Strontium (Sr) has been widely accepted as an anti-osteoporosis element. In this study, we fabricated a series of apatite and Sr-substituted apatite coatings via electrochemical deposition under different acidic conditions. The results showed that Ca and Sr exhibited different mineralization behaviors. The main mineralization products for Ca were CaHPO₄·2H₂O and Ca₃(PO₄)₂ with the structure changed from porous to spherical as the pH values increased. The main mineralization products for Sr were SrHPO₄ and Sr₅(PO₄)₃OH with the structure changed from flake to needle as the pH values increased. The in vitro experiment demonstrated that coatings fabricated at high pH condition with the presence of Sr were favorable to MSCs adhesion, spreading, proliferation, and osteogenic differentiation. In addition, Sr-substituted apatite coatings could evidently inhibit osteoclast differentiation and fusion. Moreover, the in vivo study indicated that nano-needle like Sr-substituted apatite coating could suppress osteoclastic activity, improve new bone formation, and enhance bone-implant integration. This study provided a new theoretical guidance for implant coating design and the fabricated Sr-substituted coating might have potential applications for osteoporotic patients.

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Ca²⁺ and Sr²⁺ showed different mineralization behaviors in acidic environments.

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Apatites fabricated at high pH conditions were beneficial to MSCs growth.

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Sr-substituted apatite exhibited superior anti-osteoclast activity ability.

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Sr-substituted apatite facilitated osteogenesis, bone growth, and osseointegration.

Drug-delivery Ca-Mg silicate scaffolds encapsulated in PLGA

The aim of this work is to develop dual-functional scaffolds for bone tissue regeneration and local antibiotic delivery applications. In this respect, bioresorbable bredigite (Ca₇MgSi₄O₁₆) porous scaffolds were fabricated by a foam replica method, loaded with vancomycin hydrochloride and encapsulated in poly lactic-co-glycolic acid (PLGA) coatings. Field emission scanning electron microscopy, Archimedes porosimetry and Fourier-transform infrared spectroscopy were used to characterize the structure of the scaffolds. The drug delivery kinetics and cytocompatibility of the prepared scaffolds were also studied in vitro. The bare sample exhibited a burst release of vancomycin and low biocompatibility with respect to dental pulp stem cells based on the MTT assay due to the fast bioresorption of bredigite. While keeping the desirable characteristics of pores for tissue engineering, the biodegradable PLGA coatings modified the drug release kinetics, buffered physiological pH and hence improved the cell viability of the vancomycin-loaded scaffolds considerably.