Biomineralization of bone tissue: calcium phosphate-based inorganics in collagen fibrillar organic matrices

Incorporation of metal-doped silicate microparticles into collagen scaffolds combines chemical and architectural cues for endochondral bone healing

Regeneration of large bone defects remains a clinical challenge until today. While existing biomaterials are predominantly addressing bone healing via direct, intramembranous ossification (IO), bone tissue formation via a cartilage phase, so-called endochondral ossification (EO) has been shown to be a promising alternative strategy. However, pure biomaterial approaches for EO induction are sparse and the knowledge how material components can have bioactive contribution to the required cartilage formation is limited. Here, we combined a previously developed purely architecture-driven biomaterial approach with the release of therapeutic metal ions from tailored silicate microparticles. The delivery platform was free of calcium phosphates (CaP) that are known to support IO but not EO and was employed for the release of lithium (Li), magnesium (Mg), strontium (Sr) or zinc (Zn) ions. We identified an ion-specific cellular response in which certain metal ions strongly enhanced cell recruitment into the material and showed superior chondrogenesis and deposition collagen II by human mesenchymal stromal cells (MSCs). At the same time, in some cases microparticle incorporation altered the mechanical properties of the biomaterial with consequences for cell-induced biomaterial contraction and scaffold wall deformation. Collectively, the results suggest that the incorporation of metal-doped silicate microparticles has the potential to further improve the bioactivity of architectured biomaterials for bone defect healing via EO. STATEMENT OF SIGNIFICANCE: Endochondral bone healing, a process that resembles embryonic skeletal development, has gained prominence in regenerative medicine. However, most therapeutic biomaterial strategies are not optimized for endochondral bone healing but instead target direct bone formation through IO. Here, we report on a novel approach to accelerate biomaterial-guided endochondral bone healing by combining cell-guiding collagen scaffolds with therapeutic metal-doped silicate microparticles. While other strategies, such as hypoxia-mimic drugs and iron-chelating biomaterials, have been documented in the literature before to enhance EO, our approach uniquely implements enhanced bioactivity into a previously developed biomaterial strategy for bone defect regeneration. Enhanced cell recruitment into the material and more pronounced chondrogenesis were observed for specific hybrid scaffold formulations, suggesting a high relevance of this new biomaterial for improved endochondral bone healing.

Plasma-electrolytic oxidation: A rapid single step post processing approach for additively manufactured biomedical implants

Laser-powder bed fusion (PBF-LB) has enabled production of customised skeletal implants that incorporate porous lattices structures to enable bone ingrowth. However, the inherent surface roughness of PBF-LB, characterised by partially adhered particles and undulating sub-topography, remains a barrier to adoption. As such PBF-LB surfaces require several time-consuming post-processing steps, nevertheless, conventional finishing techniques are often limited by geometrical part complexity, making them unsuitable for porous PBF-LB parts. Herein we explore the possibility to utilise plasma-electrolytic oxidation (PEO) as a rapid, single step surface finishing method not constrained by implant design. Specifically, PEO treatment was performed in a phosphate-based electrolyte on as-printed and polished Ti-6Al-4V PBF-LB samples with complete surface coverage and chemical functionalisation, as observed by optical profilometry, SEM-EDX, XRD and XRF, achieved after only 20 min. To test the lack of geometric constraints brought by PEO, clinically relevant BCC porous lattices were also successfully PEO treated accomplishing a coating that either masked or removed surface adhered particles throughout the structure. Promisingly for medical application, no cytotoxicity was noted for MC3T3-E1 murine osteoblasts over 7 days and significantly more (p < 0.05) mineralisation was observed after 21 days compared with as-printed and polished PBF-LB controls. Still, an enhanced pro-inflammatory response, iNOS and TNF-α, was observed in murine RAW261 macrophages seeded on PEO surfaces, indicating further optimisation is required to guide the inflammatory process. Overall, these findings showcase the widespread opportunity to robustly ensure PBF-LB implant safety by using PEO to tackle partially adhered particles while also offering new avenues to enhance functionality through variations in coating chemistry.

Thioether functionalized degradable poly(amino acids) and its calcium sulfate/calcium hydrogen phosphate composites: Reducing oxidative stress and promoting osteogenesis

The imbalance of redox homeostasis, especially the abnormal levels of reactive oxygen species (ROS), is a key obstacle in the bone repair process. Therefore, developing materials capable of scavenging ROS and modulating the microenvironment of bone defects is crucial for promoting bone repair. In this study, to endow poly(amino acids) (PAA) and its composites with anti-oxidative stress properties and enhanced osteogenic differentiation, we designed and prepared a calcium sulfate/calcium hydrogen phosphate/poly(amino acids) (PCDM) composite material with a thioether structure (-S-) in the molecular chain of PAA matrix through situ polymerization and physical blending method. The results showed that the thioether was successfully introduced into the polymer, and the intrinsic viscosities of the poly(amino acids) ranged from 0.27 to 0.73 dL/g. PCDM materials exhibited good mechanical properties, with a compressive strength ranging from 16.28 to 33.83 MPa. The degradation performance results showed that the composite materials had a weight loss of 23.9-35.3 % after four weeks. The antioxidant stress results showed that the PCDM composite materials scavenged 67.6 %-78.3 % of DPPH radicals after 24 h and 61.4 %-93.6 % of ABTS radicals after 4 h, effectively reducing ROS levels in mouse bone mesenchymal stem cells. The cytotoxicity and osteogenic differentiation results showed that the materials had cytocompatibility and could promote alkaline phosphatase secretion and mineralized nodule formation. In conclusion, PCDM materials might broaden the application of poly(amino acids) composites in bone defect repair by regulating the ROS microenvironment and promoting the osteogenic differentiation of stem cells.

Repair of Osteoporotic Bone Defects in Rats via the Sirtuin 1-Wnt/β-catenin Signaling Pathway by Novel Icariin/Porous Magnesium Alloy Scaffolds

The slow rate of bone regeneration and repair in osteoporotic defects is one of the difficulties of clinical work. To prepare a novel icariin (ICA)/porous magnesium alloy scaffold and to investigate its effectiveness and possible mechanism in repairing osteoporotic bone defects, bilateral ovariectomy was performed on Sprague-Dawley rats. Then, a cylindrical bone defect was created in the model, and a novel ICA/porous magnesium alloy scaffold was prepared and implanted into the defect. Eight or 12 weeks after repairing, specimens and micro-computed tomography (CT) data were collected. Microscopic observation was fulfilled through hematoxylin and eosin, Goldner, Masson, periodic acid-Schiff, and Sirius red staining. The expression of proteins was detected by immunohistochemical staining. The novel ICA/porous magnesium alloy scaffold was noncytotoxic and biologically safe. After it was implanted into the defect for 8 or 12 weeks, the surface color and smoothness, depth, and area of the defect were better than those in the control group. Besides, there was sufficient osteoid tissue, more mineralized bones, more collagen fibers, and more polysaccharide components in the defect repaired with the ICA/porous magnesium alloy scaffold. These conditions are closer to those of real bones. Moreover, the repair effect improved with the repair time. Compared with those in the control group, the expression levels of Sirtuin 1(SIRT1), Wnt5a, β-catenin, glycogen synthase kinase 3β, alkaline phosphatase, runt-related transcription factor 2, bone morphogenetic protein-2, and osteocalcin proteins were elevated in bone tissue after the scaffold was implanted into the defect for 8 weeks (all P < 0.05). The novel ICA/porous magnesium alloy scaffold promotes the repair of osteoporotic bone defects in rats, a process that may be achieved through activation of the SIRT1-Wnt/β-catenin signaling pathway.

Principles of Fracture Healing and Fixation: A Literature Review

Bone healing is a complex, dynamic process involving a series of well-coordinated stages, influenced by both mechanical and biological factors. The skeletal system, composed of inorganic (36%), organic (36%), and water (28%) components by volume, plays a crucial role in maintaining structural integrity and mineral homeostasis. Bone is classified into two main types based on microstructure: lamellar and woven bone, with lamellar bone being stronger and more durable. Factors such as inflammation, the periosteum, vascularity, and infection significantly impact healing outcomes. Moreover, fracture fixation is fundamental to optimal healing, guided by principles of anatomical reduction, stable fixation, blood supply preservation, and early mobilisation. Perren's strain theory emphasises the importance of strain at the fracture site, which can determine whether primary or secondary healing occurs. Rigid fixation provides an environment which promotes primary bone healing, while flexible fixation promotes secondary healing through controlled motion. Internal and external fixation methods, including plates, screws, and intramedullary nails, offer varying degrees of stability, supporting bone healing. Overall, optimal fracture fixation, combined with an understanding of bone biology, enhances healing and functional recovery.

Commercially available bioinks and state-of-the-art lab-made formulations for bone tissue engineering: A comprehensive review

Bioprinting and bioinks are two of the game changers in bone tissue engineering. This review presents different bioprinting technologies including extrusion-based, inkjet-based, laser-assisted, light-based, and hybrid technologies with their own strengths and weaknesses. This review will aid researchers in the selection and assessment of the bioink; the discussion ranges from commercially available bioinks to custom lab-made formulations mainly based on natural polymers, such as agarose, alginate, gelatin, collagen, and chitosan, designed for bone tissue engineering. The review is centered on technological advancements and increasing clinical demand within the rapidly growing bioprinting market. From this point of view, 4D, 5D, and 6D printing technologies promise a future where unprecedented levels of innovation will be involved in fabrication processes leading to more dynamic multifunctionalities of bioprinted constructs. Further advances in bioprinting technology, such as hybrid bioprinting methods are covered, with the promise to meet personalized medicine goals while advancing patient outcomes for bone tissues engineering applications.

The Influence of Juglans regia L. Extract and Ellagic Acid on Oxidative Stress, Inflammation, and Bone Regeneration Biomarkers

Bone regeneration is a highly dynamic and complex process that involves hematopoietic stem cells and mesenchymal cells, collagen fibers, non-collagenous proteins and biomolecules from extracellular matrices, and different cytokines and immune cells, as well as growth factors and hormones. Some phytochemicals due to antioxidant and anti-inflammatory effects can modulate the bone signaling pathways and improve bone healing and thus can be a good candidate for osteoregeneration. The aim of this study was to analyze the impact of Juglans regia L. extract compared to ellagic acid on bone neoformation in rats. The animals with a 5 mm calvaria defect were divided into four groups (n = 10): group 1 was treated with ellagic acid 1% (EA), group 2 was treated with Juglans regia L. extract 10% (JR), group 3 was treated with a biphasic mix of hydroxyapatite and tricalcium phosphate (Ceraform), and group 4 was treated with vehicle inert gel with carboxymethylcellulose (CMC). After 3 weeks of treatment, blood samples were collected for oxidative stress and inflammation assessment. Additionally, the receptor activator of nuclear factor kappa-Β ligand (RANKL) and hydroxyproline levels were quantified in blood. The skull samples were analyzed by scanning electron microscopy in order to detect the modifications in the four groups. The results suggested that JR extract had relevant anti-oxidant effect and bone protective activity and generated the accumulation of Ca and P, demonstrating the potential therapeutic abilities in bone regeneration.

Biomimetic Morphogenesis of Strontium Chitosan-Gelatin Composite Aggregates via EPD and Biomineralization in vitro and in vivo

Introduction

Biomineralization has been increasingly adopted for the synthesis of advanced materials with superior properties. Hierarchical architecture growth mimicking biomineralization has been studied using various organic molecules to template inorganic materials with controlled morphology. In our previous study, self-assembled Sr/CS/G(SrCO3-chitosan-gelatin) aggregates were fabricated using electrophoretic deposition (EPD). This study is a further step toward understanding the morphogenesis of Sr/CS/G aggregates and its biomineralization.

Methods

Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to investigate the biomimetic morphogenesis of Sr/CS/G composite under various EPD parameters, such as polymer concentration, time, and voltage. The Sr/CS/G aggregates were immersed in H2O, phosphate-buffered saline (PBS), and simulated body fluid (SBF) to study the bioactive apatite formation ability. In addition, biocompatibility of the composites were evaluated by Fluorescence staining, SEM in vitro. The osteogenic ability of the coatings induced by PBS were tested in vivo.

Results

The CS/G weight ratio, EPD time, and voltage were found to influence the morphogenesis of Sr/CS/G aggregates. SEM and TEM results showed that the Sr/CS/G aggregates exhibited fractal growth characteristics and morphological self-similarity. XRD results confirmed the formation of SrCO3 crystals within the framework of chitosan and gelatin organic templates. Chitosan played a vital role in branching growth of the crystals, whereas gelatin guided the formation of composite spheres. The microstructural and compositional results reveal that the Sr/CS/G-induced apatite coating yielded a large quantity of apatite. These apatite coatings promote the cytocompatibility and osteogenesis of rat bone marrow mesenchymal stem cells (rBMSCs) in vitro. The coatings induced by PBS enhanced proliferation and mineralization in vitro, and enhanced angiogenesis and osteogenesis in vivo.

Conclusion

Sr/CS/G composites prepared via EPD are promising organic-inorganic templates for biomineralization. These findings provide important insights into understanding the mineralization process and optimizing the design of advanced biological materials.

Evaluation of mineral induction ability and cytotoxicity of carbonated hydroxyapatite for pulp tissue regeneration: an in vitro study

Objectives

This study aimed to evaluate carbonated hydroxyapatite (CHA)'s ability for mineral induction and its in vitro cytotoxicity with human dental pulp cells.

Materials and Methods

Precursors for the study include di-ammonium hydrogen phosphate and calcium nitrate tetrahydrate, with sodium hydrogen carbonate added to achieve different levels of carbonate substitution. The synthesized CHA samples are characterized using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Scanning electron microscopy (SEM) was used to observe morphology. For 14 days at 37°C, samples were submerged in simulated body fluid to assess their mineral induction capabilities. SEM was used to confirm apatite formation on sample surfaces. The cytotoxicity assay was used to assess the vitality of the cells following their exposure to various concentrations of CHA.

Results

The Joint Committee on Powder Diffraction Standards data for HA aligned well with the results from X-ray diffraction analysis of CHA across 3 different concentrations, indicating strong agreement. Fourier transform infrared spectra indicated the presence of phosphate, hydroxyl, and carbonate groups within the samples. SEM and Energy-dispersive X-ray analysis show agglomerated and flaky nanoparticles. All the samples are bioactive, but the formation of apatite differs from one another. In vitro cytotoxicity assay showed that over 70% of cells maintain viability.

Conclusions

The results of this study may provide insight into the potential use of carbonated HA as a dental pulp-capping material for vital pulp therapy.

Hybrid Hydroxyapatite-Metal Complex Materials Derived from Amino Acids and Nucleobases

Calcium phosphates (CaPs) and their substituted derivatives encompass a large number of compounds with a vast presence in nature that have aroused a great interest for decades. In particular, hydroxyapatite (HAp, Ca10(OH)2(PO4)6) is the most abundant CaP mineral and is significant in the biological world, at least in part due to being a major compound in bones and teeth. HAp exhibits excellent properties, such as safety, stability, hardness, biocompatibility, and osteoconductivity, among others. Even some of its drawbacks, such as its fragility, can be redirected thanks to another essential feature: its great versatility. This is based on the compound's tendency to undergo substitutions of its constituent ions and to incorporate or anchor new molecules on its surface and pores. Thus, its affinity for biomolecules makes it an optimal compound for multiple applications, mainly, but not only, in biological and biomedical fields. The present review provides a chemical and structural context to explain the affinity of HAp for biomolecules such as proteins and nucleic acids to generate hybrid materials. A size-dependent criterium of increasing complexity is applied, ranging from amino acids/nucleobases to the corresponding macromolecules. The incorporation of metal ions or metal complexes into these functionalized compounds is also discussed.

Osteoinductive and regenerative potential of premixed calcium-silicate bioceramic sealers on vascular wall mesenchymal stem cells

AIM

The osteogenic potential of new premixed calcium-silicate-containing bioceramic sealers (Ca-Si sealers) was tested with porcine vascular wall-mesenchymal stem cells (pVW-MSCs).

METHODOLOGY

Two Ca-Si-containing sealers: Ceraseal (MetaBiomed, Cheong-si, South Korea) and AH Plus Bioceramic (Maruchi, Wonju-si, South Korea), and an epoxy resin sealer (AH Plus; Dentsply, Konstanz, Germany) as a control, were prepared according to the manufacturers' indications. All samples were allowed to set for 100% of their setting time in a sterile humid cabinet at 37°C and 95% relative humidity. pVW-MSC seeding efficiency and osteogenic differentiation were analysed as marker of gene/protein expression for up to 12 days. Mineralization assay and immunofluorescence staining were performed and evaluated over a period of 21 days. Statistical analyses were conducted using one-way analysis of variance (p < .05). Additional samples were prepared and stored under the same conditions and inspected using an environmental scanning electron microscope equipped with an energy dispersive X-ray spectroscopy system.

RESULTS

Significantly higher cell seeding efficiency (p < .05) was observed for both Ca-Si sealers from day 8. pVW-MSCs showed a significant shift towards the osteogenic lineage only when seeded in contact with Ca-Si sealers. Gene expression of osteopontin was upregulated significantly. Collagen I and osteocalcin were clearly expressed by cells in contact with Ca-Si sealers. Mineralization granules were observed in Alizarin red assays and confocal laser scanning microscopy analysis of both Ca-Si sealers. No gene expression or granule mineralization were observed on the epoxy resin sealer.

CONCLUSIONS

Premixed Ca-Si sealers displayed a higher potential for osteogenic activity on pVW-MSCs. Epoxy resin sealer was unable to induce any osteogenic activity. The properties of both Ca-Si sealers suggest their potential as osteoinductive platforms for vascular MSCs in periapical bone.

Biomimetic Scaffolds of Calcium-Based Materials for Bone Regeneration

Calcium-based materials, such as calcium carbonate, calcium phosphate, and calcium silicate, have attracted significant attention in biomedical research, owing to their unique physicochemical properties and versatile applications. The distinctive characteristics of these materials, including their inherent biocompatibility and tunable structures, hold significant promise for applications in bone regeneration and tissue engineering. This review explores the biomedical applications of calcium-containing materials, particularly for bone regeneration. Their remarkable biocompatibility, tunable nanostructures, and multifaceted functionalities make them pivotal for advancing regenerative medicine, drug delivery system, and biomimetic scaffold applications. The evolving landscape of biomedical research continues to uncover new possibilities, positioning calcium-based materials as key contributors to the next generation of innovative biomaterial scaffolds.

Collagen structures of demineralized bone paper direct mineral metabolism

Bone is a dynamic mineralized tissue that undergoes continuous turnover throughout life. While the general mechanism of bone mineral metabolism is documented, the role of underlying collagen structures in regulating osteoblastic mineral deposition and osteoclastic mineral resorption remains an active research area, partly due to the lack of biomaterial platforms supporting accurate and analytical investigation. The recently introduced osteoid-inspired demineralized bone paper (DBP), prepared by 20-μm thin sectioning of demineralized bovine compact bone, holds promise in addressing this challenge as it preserves the intrinsic bony collagen structure and retains semi-transparency. Here, we report on the impact of collagen structures on modulating osteoblast and osteoclast-driven bone mineral metabolism using vertical and transversal DBPs that exhibit a uniaxially aligned and a concentric ring collagen structure, respectively. Translucent DBP reveals these collagen structures and facilitates longitudinal tracking of mineral deposition and resorption under brightfield microscopy for at least 3 wk. Genetically labeled primary osteogenic cells allow fluorescent monitoring of these cellular processes. Osteoblasts adhere and proliferate following the underlying collagen structures of DBPs. Osteoblastic mineral deposition is significantly higher in vertical DBP than in transversal DBP. Spatiotemporal analysis reveals notably more osteoblast adhesion and faster mineral deposition in vascular regions than in bone regions. Subsequent osteoclastic resorption follows these mineralized collagen structures, directing distinct trench and pit-type resorption patterns. In vertical DBP, trench-type resorption occurs at an 80% frequency, whereas transversal DBP shows 35% trench-type and 65% pit-type resorption. Our studies substantiate the importance of collagen structures in regulating mineral metabolism by osteogenic cells. DBP is expected to serve as an enabling biomaterial platform for studying various aspects of cellular and extracellular bone remodeling biology.

Evaluating osteogenic potential of a 3D-printed bioceramic-based scaffold for critical-sized defect treatment: an in vivo and in vitro investigation

The integration of precision medicine principles into bone tissue engineering has ignited a wave of research focused on customizing intricate scaffolds through advanced 3D printing techniques. Bioceramics, known for their exceptional biocompatibility and osteoconductivity, have emerged as a promising material in this field. This article aims to evaluate the regenerative capabilities of a composite scaffold composed of 3D-printed gelatin combined with hydroxyapatite/tricalcium phosphate bioceramics (G/HA/TCP), incorporating human dental pulp-derived stem cells (hDPSCs). Using 3D powder printing, we created cross-shaped biphasic calcium phosphate scaffolds with a gelatin layer. The bone-regenerating potential of these scaffolds, along with hDPSCs, was assessed through in vitro analyses and in vivo studies with 60 rats and critical-sized calvarial defects. The assessment included analyzing cellular proliferation, differentiation, and alkaline phosphatase activity (ALP), and concluded with a detailed histological evaluation of bone regeneration. Our study revealed a highly favorable scenario, displaying not only desirable cellular attachment and proliferation on the scaffolds but also a notable enhancement in the ALP activity of hDPSCs, underscoring their pivotal role in bone regeneration. However, the histological examination of calvarial defects at the 12-wk mark yielded a rather modest level of bone regeneration across all experimental groups. The test and cell group exhibited significant bone formation compared to all other groups except the control and cell group. This underscores the complexity of the regenerative process and paves the way for further in-depth investigations aimed at improving the potential of the composite scaffolds.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

In vitro and in vivo degradation, biocompatibility and bone repair performance of strontium-doped montmorillonite coating on Mg-Ca alloy

Poor bone growth remains a challenge for degradable bone implants. Montmorillonite and strontium were selected as the carrier and bone growth promoting elements to prepare strontium-doped montmorillonite coating on Mg-Ca alloy. The surface morphology and composition were characterized by SEM, EDS, XPS, FT-IR and XRD. The hydrogen evolution experiment and electrochemical test results showed that the Mg-Ca alloy coated with Sr-MMT coating possessed optimal corrosion resistance performance. Furthermore, in vitro studies on cell activity, ALP activity, and cell morphology confirmed that Sr-MMT coating had satisfactory biocompatibility, which can significantly avail the proliferation, differentiation, and adhesion of osteoblasts. Moreover, the results of the 90-day implantation experiment in rats indicated that, the preparation of Sr-MMT coating effectively advanced the biocompatibility and bone repair performance of Mg-Ca alloy. In addition, The Osteogenic ability of Sr-MMT coating may be due to the combined effect of the precipitation of Si4+ and Sr2+ in Sr-MMT coating and the dissolution of Mg2+ and Ca2+ during the degradation of Mg-Ca alloy. By using coating technology, this study provides a late-model strategy for biodegradable Mg alloys with good corrosion resistance, biocompatibility. This new material will bring more possibilities in bone repair.

Bone-like apatite formation in biocompatible phosphate-crosslinked bacterial cellulose-based hydrogels for bone tissue engineering applications

Addressing major bone injuries is a challenge in bone regeneration, necessitating innovative 3D hydrogel-based therapeutic approaches to enhance scaffold properties for better bioactivity. Bacterial cellulose (BC) is an excellent scaffold for bone tissue engineering due to its biocompatibility, high porosity, substantial surface area, and remarkable mechanical strength. However, its practical application is limited due to a lack of inherent osteogenic activity and biomineralization ability. In this study, we synthesized bone-like apatite in biocompatible BC hydrogel by introducing phosphate groups. Hydrogels were prepared using fibrous BC, acrylamide (AM), and bis [2-methacryloyloxy] ethyl phosphate (BMEP) as a crosslinker through free radical polymerization (P-BC-PAM). P-BC-PAM hydrogels exhibited outstanding compressive mechanical properties, highly interconnected porous structures, good swelling, and biodegradable properties. BMEP content significantly influenced the physicochemical and biological properties of the hydrogels. Increasing BMEP content enhanced the fibrous structure, porosity from 85.1 % to 89.5 %, and compressive mechanical strength. The optimized hydrogel (2.0P-BC-PAM) displayed maximum compressive stress, toughness, and elastic modulus at 75 % strain: 221 ± 0.08 kPa, 24,674.2 ± 978 kPa, and 11 ± 0.47 kPa, respectively. P-BC-PAM hydrogels underwent biomineralization in simulated body fluid (SBF) for 14 days, forming bone-like apatite with a Ca/P ratio of 1.75, similar to hydroxyapatite. Confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM), this suggests their potential as scaffolds for bone tissue engineering. MC3T3-E1 osteoblast cells effectively attached and proliferated on P-BC-PAM. In summary, this study contributes insights into developing phosphate-functionalized BC-based hydrogels with potential applications in bone tissue engineering.

Multifunctional hydrogel/platelet-rich fibrin/nanofibers scaffolds with cell barrier and osteogenesis for guided tissue regeneration/guided bone regeneration applications

Periodontal defect seriously affects people's life health and quality. Guided tissue regeneration (GTR) and guided bone regeneration (GBR) have made great progress in periodontal disease treatment, but some deficiencies existed in commercial materials of GTR and GBR. For obtaining better therapeutic effects, multifunctional composite scaffolds containing different biological macromolecules were developed in this study. Chitosan/poly (γ-glutamic acid)/nano-hydroxyapatite hydrogels (CP/nHA) made by electrostatic interactions and lyophilization were filled in the bone defects to achieve osteogenesis. Platelet-rich fibrin (PRF) extracted from blood could accelerate bone formation by releasing various bioactive substances as middle layer of composite scaffolds. Polycaprolactone/gelatin nanofibers (PG) prepared by electrospinning were attached to the junction of soft and hard tissue, which could prevent fibrous tissue from infiltrating into bone defects. The composite scaffolds showed good morphology, biocompatibility, cell barriers and osteogenic differentiation in vitro. The excellent ability of bone formation was verified by implantation of triple-layered composite scaffolds into alveolar bone defects in rabbit in vivo. The hierarchical structure was conducive to personalized customization to meet the needs of different defects. All in all, the multifunctional scaffolds could play important roles of GTR and GBR in alveolar bone regeneration and provide good application prospect for bone repair in clinic.

Enhancement of properties of a cell-laden GelMA hydrogel-based bioink via calcium phosphate phase transition

To improve the properties of the hydrogel-based bioinks, a calcium phosphate phase transition was applied, and the products were examined. We successfully enhanced the mechanical properties of the hydrogels by adding small amounts (< 0.5 wt%) of alpha-tricalcium phosphate (α-TCP) to photo-crosslinkable gelatin methacrylate (GelMA). As a result of the hydrolyzing calcium phosphate phase transition involvingα-TCP, which proceeded for 36 h in the cell culture medium, calcium-deficient hydroxyapatite was produced. Approximately 18 times the compressive modulus was achieved for GelMA with 0.5 wt%α-TCP (20.96 kPa) compared with pure GelMA (1.18 kPa). Although cell proliferation decreased during the early stages of cultivation, both osteogenic differentiation and mineralization activities increased dramatically when the calcium phosphate phase transition was performed with 0.25 wt%α-TCP. The addition ofα-TCP improved the printability and fidelity of GelMA, as well as the structural stability and compressive modulus (approximately six times higher) after three weeks of culturing. Therefore, we anticipate that the application of calcium phosphate phase transition to hydrogels may have the potential for hard tissue regeneration.

Glucose oxidase and metal catalysts combined tumor synergistic therapy: mechanism, advance and nanodelivery system

Cancer has always posed a significant threat to human health, prompting extensive research into new treatment strategies due to the limitations of traditional therapies. Starvation therapy (ST) has garnered considerable attention by targeting the primary energy source, glucose, utilized by cancer cells for proliferation. Glucose oxidase (GOx), a catalyst facilitating glucose consumption, has emerged as a critical therapeutic agent for ST. However, mono ST alone struggles to completely suppress tumor growth, necessitating the development of synergistic therapy approaches. Metal catalysts possess enzyme-like functions and can serve as carriers, capable of combining with GOx to achieve diverse tumor treatments. However, ensuring enzyme activity preservation in normal tissue and activation specifically within tumors presents a crucial challenge. Nanodelivery systems offer the potential to enhance therapy effectiveness by improving the stability of therapeutic agents and enabling controlled release. This review primarily focuses on recent advances in the mechanism of GOx combined with metal catalysts for synergistic tumor therapy. Furthermore, it discusses various nanoparticles (NPs) constructs designed for synergistic therapy in different carrier categories. Finally, this review provides a summary of GOx-metal catalyst-based NPs (G-M) and offers insights into the challenges associated with G-M therapy, delivery design, and oxygen (O2) supply.

Viability of Collagen Matrix Grafts Associated with Nanohydroxyapatite and Elastin in Bone Repair in the Experimental Condition of Ovariectomy

Bone lesions have the capacity for regeneration under normal conditions of the bone metabolism process. However, due to the increasing incidence of major traumas and diseases that cause bone-mineral deficiency, such as osteoporosis, scaffolds are needed that can assist in the bone regeneration process. Currently, natural polymeric scaffolds and bioactive nanoparticles stand out. Therefore, the objective of the study was to evaluate the osteoregenerative potential in tibiae of healthy and ovariectomized rats using mineralized collagen and nanohydroxyapatite (nHA) scaffolds associated with elastin. The in-vivo experimental study was performed with 60 20-week-old Wistar rats, distributed into non-ovariectomized (NO) and ovariectomized (O) groups, as follows: Controls (G1-NO-C and G4-O-C); Collagen with nHA scaffold (G2-NO-MSH and G5-O-MSH); and Collagen with nHA and elastin scaffold (G3-NO-MSHC and G6-O-MSHC). The animals were euthanized 6 weeks after surgery and the samples were analyzed by macroscopy, radiology, and histomorphometry. ANOVA and Tukey tests were performed with a 95% CI and a significance index of p < 0.05. In the histological analyses, it was possible to observe new bone formed with an organized and compact morphology that was rich in osteocytes and with maturity characteristics. This is compatible with osteoconductivity in both matrices (MSH and MSHC) in rats with normal conditions of bone metabolism and with gonadal deficiency. Furthermore, they demonstrated superior osteogenic potential when compared to control groups. There was no significant difference in the rate of new bone formation between the scaffolds. Ovariectomy did not exacerbate the immune response but negatively influenced the bone-defect repair process.

Tissue-specific expression of senescence biomarkers in spontaneously hypertensive rats: evidence of premature aging in hypertension

Background

Cellular senescence is an age-related physiological process that contributes to tissue dysfunction and accelerated onset of chronic metabolic diseases including hypertension. Indeed, elevation of blood pressure in hypertension coincides with premature vascular aging and dysfunction. In addition, onsets of metabolic disturbance and osteopenia in patients with hypertension have also been reported. It is possible that hypertension enhances premature aging and causes progressive loss of function in multiple organs. However, the landscape of cellular senescence in critical tissues affected by hypertension remains elusive.

Materials and Methods

Heart, liver, bone, hypothalamus, and kidney were collected from spontaneously hypertensive rats (SHR) and age- and sex-matched normotensive Wistar rats (WT) at 6, 12, 24 and 36 weeks of age (n = 10 animals/group). Changes in mRNA levels of senescence biomarkers namely cyclin-dependent kinase (CDK) inhibitors (CDKIs), i.e., Cdkn2a (encoding p16Ink4a) and Cdkn1a (encoding p21cip1) as well as senescence-associated secretory phenotypes (SASPs), i.e., Timp1, Mmp12, Il6 and Cxcl1, were determined. Additionally, bone collagen alignment and hydroxy apatite crystal dimensions were determined by synchrotron radiation small- and wide-angle X-ray scattering (SAXS/WAXS) techniques.

Results

Real-time PCR revealed that transcript levels of genes encoding CDKIs and SASPs in the heart and liver were upregulated in SHR from 6 to 36 weeks of age. Expression of Timp1 and Cxcl1 was increased in bone tissues isolated from 36-week-old SHR. In contrast, we found that expression levels of Timp1 and Il6 mRNA were decreased in hypothalamus and kidney of SHR in all age groups. Simultaneous SAXS/WAXS analysis also revealed misalignment of bone collagen fibers in SHR as compared to WT.

Conclusion

Premature aging was identified in an organ directly affected by high blood pressure (i.e., heart) and those with known functional defects in SHR (i.e., liver and bone). Cellular senescence was not evident in organs with autoregulation of blood pressure (i.e., brain and kidney). Our study suggested that cellular senescence is induced by persistently elevated blood pressure and in part, leading to organ dysfunction. Therefore, interventions that can both lower blood pressure and prevent cellular senescence should provide therapeutic benefits for treatment of cardiovascular and metabolic consequences.

A Comparative Study of HA/DBM Compounds Derived from Bovine and Porcine for Bone Regeneration

This comparative study investigated the tissue regeneration and inflammatory response induced by xenografts comprised of hydroxyapatite (HA) and demineralized bone matrix (DBM) extracted from porcine (P) and bovine (B) sources. First, extraction of HA and DBM was independently conducted, followed by chemical and morphological characterization. Second, mixtures of HA/DBM were prepared in 50/50 and 60/40 concentrations, and the chemical, morphological, and mechanical properties were evaluated. A rat calvarial defect model was used to evaluate the tissue regeneration and inflammatory responses at 3 and 6 months. The commercial allograft DBM Puros® was used as a clinical reference. Different variables related to tissue regeneration were evaluated, including tissue thickness regeneration (%), amount of regenerated bone area (%), and amount of regenerated collagen area (%). The inflammatory response was evaluated by quantifying the blood vessel area. Overall, tissue regeneration from porcine grafts was superior to bovine. After 3 months of implantation, the tissue thickness regeneration in the 50/50P compound and the commercial DBM was significantly higher (~99%) than in the bovine materials (~23%). The 50/50P and DBM produced higher tissue regeneration than the naturally healed controls. Similar trends were observed for the regenerated bone and collagen areas. The blood vessel area was correlated with tissue regeneration in the first 3 months of evaluation. After 6 months of implantation, HA/DBM compounds showed less regenerated collagen than the DBM-only xenografts. In addition, all animal-derived xenografts improved tissue regeneration compared with the naturally healed defects. No clinical complications associated with any implanted compound were noted.

Evaluation and Application of Silk Fibroin Based Biomaterials to Promote Cartilage Regeneration in Osteoarthritis Therapy

Osteoarthritis (OA) is a common joint disease characterized by cartilage damage and degeneration. Traditional treatments such as NSAIDs and joint replacement surgery only relieve pain and do not achieve complete cartilage regeneration. Silk fibroin (SF) biomaterials are novel materials that have been widely studied and applied to cartilage regeneration. By mimicking the fibrous structure and biological activity of collagen, SF biomaterials can promote the proliferation and differentiation of chondrocytes and contribute to the formation of new cartilage tissue. In addition, SF biomaterials have good biocompatibility and biodegradability and can be gradually absorbed and metabolized by the human body. Studies in recent years have shown that SF biomaterials have great potential in treating OA and show good clinical efficacy. Therefore, SF biomaterials are expected to be an effective treatment option for promoting cartilage regeneration and repair in patients with OA. This article provides an overview of the biological characteristics of SF, its role in bone and cartilage injuries, and its prospects in clinical applications to provide new perspectives and references for the field of bone and cartilage repair.

Astaxanthin as a Potent Antioxidant for Promoting Bone Health: An Up-to-Date Review

In recent years, bone loss and its associated diseases have become a significant public health concern due to increased disability, morbidity, and mortality. Oxidative stress and bone loss are correlated, where oxidative stress suppresses osteoblast activity, resulting in compromised homeostasis between bone formation and resorption. This event causes upregulation of bone remodeling turnover rate with an increased risk of fractures and bone loss. Therefore, supplementation of antioxidants can be proposed to reduce oxidative stress, facilitate the bone remodeling process, suppress the initiation of bone diseases, and improve bone health. Astaxanthin (3,3'-dihydroxy-4-4'-diketo-β-β carotene), a potent antioxidant belonging to the xanthophylls family, is a potential ROS scavenger and could be a promising therapeutic nutraceutical possessing various pharmacological properties. In bone, astaxanthin enhances osteoblast differentiation, osteocytes numbers, and/or differentiation, inhibits osteoclast differentiation, cartilage degradation markers, and increases bone mineral density, expression of osteogenic markers, while reducing bone loss. In this review, we presented the up-to-date findings of the potential anabolic effects of astaxanthin on bone health in vitro, animal, and human studies by providing comprehensive evidence for its future clinical application, especially in treating bone diseases.

MMP13-Overexpressing Mesenchymal Stem Cells Enhance Bone Tissue Formation in the Presence of Collagen Hydrogel

BACKGROUND

Matrix metalloproteinases (MMPs) are proteins involved in the repair and remodeling the extracellular matrix (ECM). MMP13 is essential for bone development and healing through the remodeling of type I collagen (COL1), the main component of the ECM in bone tissue. Mesenchymal stem cells (MSCs)-based cell therapy has been considered a promising approach for bone regeneration because of their osteogenic properties. However, the approaches using MSC to completely regenerate bone tissue have been limited. To overcome the limitation, genetic engineering of MSC could be a strategy for promoting regeneration efficacy.

METHODS

We performed in vitro and in vivo experiments using MMP13-overexpressing MSCs in the presence of COL1. To examine MMP13-overexpressing MSCs in vivo, we prepared a fibrin/COL1-based hydrogel to encapsulate MSCs and subcutaneously implanted gel-encapsulated MSCs in nude mice. We found that the osteogenic marker genes, ALP and RUNX2, were upregulated in MMP13-overexpressing MSCs through p38 phosphorylation. In addition, MMP13 overexpression in MSCs stimulated the expression of integrin α3, which is up-stream receptor of p38, and substantially increased osteogenic differentiation potential of MSCs. Bone tissue formation in MMP13-overexpressing MSCs was significantly higher than that in control MSCs. Taken together, our findings demonstrate that MMP13 is not only an essential factor for bone development and bone healing but also has a pivotal role in promoting osteogenic differentiation of MSCs to induce bone formation.

CONCLUSION

MSCs Genetically engineered to overexpress MMP13, which have a powerful potential to differentiate into the osteogenic cells, might be beneficial in bone disease therapy.

Selective excitation with recoupling pulse schemes uncover properties of disordered mineral phases in bone-like apatite grown with bone proteins

Bone construction has been under intensive scrutiny for many years using numerous techniques. Solid-state NMR spectroscopy helped unravel key characteristics of the mineral structure in bone owing to its capability of analyzing crystalline and disordered phases at high-resolution. This has invoked new questions regarding the roles of persistent disordered phases in structural integrity and mechanical function of mature bone as well as regarding regulation of early events in formation of apatite by bone proteins which interact intimately with the different mineral phases to exert biological control. Here, spectral editing tethered to standard NMR techniques is employed to analyze bone-like apatite minerals prepared synthetically in the presence and absence of two non-collagenous bone proteins, osteocalcin and osteonectin. A ¹H spectral editing block allows excitation of species from the crystalline and disordered phases selectively, facilitating analysis of phosphate or carbon species in each phase by magnetization transfer via cross polarization. Further characterization of phosphate proximities using SEDRA dipolar recoupling, cross-phase magnetization transfer using DARR and T₁/T₂ relaxation times demonstrate that the mineral phases formed in the presence of bone proteins are more complex than bimodal. They reveal disparities in the physical properties of the mineral layers, indicate the layers in which the proteins reside and highlight the effect that each protein imparts across the mineral layers.

3D Spheroid Cultivation Alters the Extent and Progression of Osteogenic Differentiation of Mesenchymal Stem/Stromal Cells Compared to 2D Cultivation

Mesenchymal stem/stromal cells (MSC) are capable of progenitor cell fraction renewal or tissue-specific differentiation. These properties are maintained during in vitro cultivation, making them an interesting model system for testing biological and pharmacological compounds. Cell cultivation in 2D is commonly used to study cellular responses, but the 2D environment does not reflect the structural situation of most cell types. Therefore, 3D culture systems have been developed to provide a more accurate physiological environment in terms of cell–cell interactions. Since knowledge about the effects of 3D culture on specific differentiation processes is limited, we studied the effects on osteogenic differentiation and the release of factors affecting bone metabolism for up to 35 days and compared them with the effects in 2D culture. We demonstrated that the selected 3D model allowed the rapid and reliable formation of spheroids that were stable over several weeks and both accelerated and enhanced osteogenic differentiation compared with the 2D culture. Thus, our experiments provide new insights into the effects of cell arrangement of MSC in 2D and 3D. However, due to the different culture dimensions, various detection methods had to be chosen, which in principle limits the explanatory power of the comparison between 2D and 3D cultures.

Designing Collagen-Binding Peptide with Enhanced Properties Using Hydropathic Free Energy Predictions

Collagen is fundamental to a vast diversity of health functions and potential therapeutics. Short peptides targeting collagen are attractive for designing modular systems for site-specific delivery of bioactive agents. Characterization of peptide-protein binding involves a larger number of potential interactions that require screening methods to target physiological conditions. We build a hydropathy-based free energy estimation tool which allows quick evaluation of peptides binding to collagen. Previous studies showed that pH plays a significant role in collagen structure and stability. Our design tool enables probing peptides for their collagen-binding property across multiple pH conditions. We explored binding features of currently known collagen-binding peptides, collagen type I alpha chain 2 sense peptide (TKKTLRT) and decorin LRR-10 (LRELHLNNN). Based on these analyzes, we engineered a collagen-binding peptide with enhanced properties across a large pH range in contrast to LRR-10 pH dependence. To validate our predictions, we used a quantum-dots-based binding assay to compare the coverage of the peptides on type I collagen. The predicted peptide resulted in improved collagen binding. Hydropathy of the peptide-protein pair is a promising approach to finding compatible pairings with minimal use of computational resources, and our method allows for quick evaluation of peptides for binding to other proteins. Overall, the free-energy-based tool provides an alternative computational screening approach that impacts protein interaction search methods.

Cooperative Calcium Phosphate Deposition on Collagen-Inspired Short Peptide Nanofibers for Application in Bone Tissue Engineering

In recent years, immense attention has been devoted over the production of osteoinductive materials. To this direction, collagen has a dominant role in developing hard tissues and plays a crucial role in the biomineralization of these tissues. Here, we demonstrated for the first time the potential of the shortest molecular pentapeptide domain inspired from collagen toward mineralizing hydroxyapatite on peptide fibers to develop bone-filling material. Our simplistic approach adapted the easy and facile route of introducing the metal ions onto the peptide nanofibers, displaying adsorbed glutamate onto the surface. This negatively charged surface further induces the nucleation of the crystalline growth of hydroxyapatite. Interestingly, nucleation and growth of the hydroxyapatite crystals lead to the formation of a self-supporting hydrogel to construct a suitable interface for cellular interactions. Furthermore, microscopic and spectroscopic investigations revealed the crystalline growth of the hydroxyapatite onto peptide fibers. The physical properties were also influenced by this crystalline deposition, as evident from the hierarchical organization leading to hydrogels with enhanced mechanical stiffness and improved thermal stability of the scaffold. Furthermore, the mineralized peptide fibers were highly compatible with osteoblast cells and showed increased cellular biomarkers production, which further reinforced the potential application toward effectively fabricating the grafts for bone tissue engineering.

Bioessential Inorganic Molecular Wire-Reinforced 3D-Printed Hydrogel Scaffold for Enhanced Bone Regeneration

Materials with physicochemical properties and biological activities similar to those of the natural extracellular matrix are in high demand in tissue engineering. In particular, Mo₃ Se₃ ^- inorganic molecular wire (IMW) is a promising material composed of bioessential minerals and possess nanometer-scale diameters, negatively charged surfaces, physical flexibility, and nanotopography characteristics, which are essential for interactions with cell membrane proteins. Here, an implantable 3D Mo₃ Se₃ ^- IMW enhanced gelatin-GMA/silk-GMA hydrogel (IMW-GS hydrogel) is developed for osteogenesis and bone formation, followed by biological evaluations. The mechanical properties of the 3D printed IMW-GS hydrogel are improved by noncovalent interactions between the Mo₃ Se₃ ^- IMWs and the positively charged residues of the gelatin molecules. Long-term biocompatibility with primary human osteoblast cells (HOBs) is confirmed using the IMW-GS hydrogel. The proliferation, osteogenic gene expression, collagen accumulation, and mineralization of HOBs improve remarkably with the IMW-GS hydrogel. In in vivo evaluations, the IMW-GS hydrogel implantation exhibits a significantly improved new bone regeneration of 87.8 ± 5.9% (p < 0.05) for 8 weeks, which is higher than that from the gelatin-GMA/silk-GMA hydrogel without Mo₃ Se₃ ^- IMW. These results support a new improved strategy with in vitro and in vivo performance of 3D IMW enhanced scaffolds in tissue engineering.

Remineralization of Demineralized Bone Matrixes with Preserved Fibrillary Structure as a Promising Approach to Obtain Highly Effective Osteoplastic Materials

The development of highly effective osteoplastic materials capable of providing bone tissue regeneration still remains an urgent and unresolved problem. In the presented work, an approach is proposed for the creation of biomimetic materials by the deposition of amorphous calcium phosphates on the surface of a xenogenic bone demineralized matrix under physiological conditions. Adsorption spectroscopy and scanning electron microscopy showed the efficiency of deposition of amorphous calcium phosphates on the trabeculae surface. The additional inclusion of the calcium-binding protein albumin was found to increase the efficiency of CPC adsorption on the trabeculae surface during DBM remineralization in vitro. In the model of heterotopic implantation for 7 weeks the osteoinductive properties of the obtained material were demonstrated, expressed in intrabecular mineralization of bone trabeculae, neovascularization and pronounced synthetic activity of osteoblasts (synthesis and structurization of neocollagen directly on the implanted material). The data obtained in the course of this work will be used to create new highly effective osteoplastic materials.

Mechanical Characteristics and Bioactivity of Nanocomposite Hydroxyapatite/Collagen Coated Titanium for Bone Tissue Engineering

In the present study, we have analyzed the mechanical characteristics and bioactivity of titanium coating with hydroxyapatite/bovine collagen. Hydroxyapatite (HAp) was synthesized from a Pinctada maxima shell and has a stoichiometry (Ca/P) of 1.72 and a crystallinity of 92%, suitable for coating materials according to ISO and Food and Drug Administration (FDA) standards. Titanium (Ti) substrate coatings were fabricated at HAp concentrations of 1% (Ti/HAp-1) and 3% (Ti/HAp-3) and a bovine collagen concentration of 1% (Ti/HAp/Coll) by the electrophoresis deposition (EPD) method. The compressive strength of Ti/HAp-1 and Ti/HAp-3 was 87.28 and 86.19 MPa, respectively, and it increased significantly regarding the control/uncoated Ti (46.71 MPa). Furthermore, the Ti/HAp-coll (69.33 MPa) has lower compressive strength due to collagen substitution (1%). The bioactivity of Ti substrates after the immersion into simulated body fluids (SBF) for 3-10 days showed a high apatite growth (Ca²⁺ and PO43-), according to XRD, FTIR, and SEM-EDS results, significantly on the Ti/HAp-coll.