Recent Advances in Hydroxyapatite-Based Biocomposites for Bone Tissue Regeneration in Orthopedics

Visible light-induced simultaneous bioactive amorphous calcium phosphate mineralization and in situ crosslinking of coacervate-based injectable underwater adhesive hydrogels for enhanced bone regeneration

The field of bone tissue engineering is vital due to increasing bone disorders and limitations of traditional grafts. Injectable hydrogels offer minimally invasive solutions but often lack mechanical integrity and biological functionality, including osteoinductive capacity and structural stability under physiological conditions. To address these issues, we propose a coacervate-based injectable adhesive hydrogel that utilizes the dual functionality of in situ photocrosslinking and osteoinductive amorphous calcium phosphate formation, both of which are activated simultaneously by visible light irradiation. The developed hydrogel formulation integrated a photoreactive agent with calcium ions and phosphonodiol in a matrix of tyramine-conjugated alginate and RGD peptide-fused bioengineered mussel adhesive protein, promoting rapid setting, robust underwater adhesion, and bioactive mineral deposition. The hydrogel also exhibited superior mechanical properties, including enhanced underwater tissue adhesive strength and compressive resistance. In vivo evaluation using a rat femoral tunnel defect model confirmed the efficacy of the developed adhesive hydrogel in facilitating easy application to irregularly shaped defects through injection, rapid bone regeneration without the addition of bone grafts, and integration within the defect sites. This injectable adhesive hydrogel system holds significant potential for advancing bone tissue engineering, providing a versatile, efficient, and biologically favorable alternative to conventional bone repair methodologies.

A Sr@Ag-based spatiotemporal and step-release scaffold against chronic osteomyelitis, fabricated by coaxial 3D-printing

Chronic osteomyelitis (OM) represents a severe and persistent infectious bone disease. Effective treatment requires controlled anti-inflammatory releases and bone regeneration across disease phases. A Sr@Ag-based scaffold was successfully printed, featuring micron-scale coaxial fibers containing Ag-doped hydroxyapatite (HA) in the outer layer of PLLA and Sr-doped HA in the inner layer of PLLA, facilitating the spatiotemporal and sequential release of Ag and Sr ions during OM treatment. Most antibacterial agent (Ag) was released during the first 20 days, followed by a slow-release plateau over the next 40 days in phosphate-buffered saline solution (PBS). Meanwhile, the pro-angiogenic agent (Sr) was released in minimal amounts during the initial 20 days, followed by a rapid and considerable release in the following 40 days. The coaxial design effectively inhibited the growth of Staphylococcus aureus and Escherichia coli while preserving the viability of bone cells. The ion-based scaffold exhibited broad-spectrum antibacterial effects and enhanced bone-regenerating gene expression in a complex air-bacteria environment. The Sr@Ag-based coaxial scaffold demonstrated effective antibacterial activity during the early stage and exhibited excellent non-toxic bone regeneration results during the middle and late stages in vivo. This work offered a promising treatment strategy through sequential anti-inflammatory and pro-osteogenic effects for infectious bone-defect diseases.

Waste-to-resource: Extraction and transformation of aquatic biomaterials for regenerative medicine

The fisheries and aquaculture industry are known for generating substantial waste or by-products, often underutilized, or relegated to low-value purposes. However, this overlooked segment harbors a rich repository of valuable bioactive materials of which have a broad-spectrum of high-value applications. As the blue economy gains momentum and fisheries expand, sustainable exploitation of these aquatic resources is increasingly prioritized. In this review, we present a comprehensive overview of technology-enabled methods for extracting and transforming aquatic waste into valuable biomaterials and their recent advances in regenerative medicine applications, focusing on marine collagen, chitin/chitosan, calcium phosphate and bioactive-peptides. We discuss the inherent bioactive qualities of these "waste-to-resource" aquatic biomaterials and identify opportunities for their use in regenerative medicine to advance healthcare while achieving the Sustainable Development Goals.

Poly(L-lactide)/nano-hydroxyapatite piezoelectric scaffolds for tissue engineering

The development of bone tissue engineering, a field with significant potential, requires a biomaterial with high bioactivity. The aim of this manuscript was to fabricate a nanofibrous poly(L-lactide) (PLLA) scaffold containing nano-hydroxyapatite (nHA) to investigate PLLA/nHA composites, particularly the effect of fiber arrangement and the addition of nHA on the piezoelectric phases and piezoelectricity of PLLA samples. In this study, we evaluated the effect of nHA particles on a PLLA-based electrospun scaffold with random and aligned fiber orientations. The addition of nHA increased the surface free energy of PLLA/nHA (42.9 mN/m) compared to PLLA (33.1 mN/m) in the case of aligned fibers. WAXS results indicated that at room temperature, all the fibers are in an amorphous state indicated by a lack of diffraction peaks and amorphous halo. DSC analysis showed that all samples located in the amorphous/disordered alpha' phase crystallize intensively at temperatures just above the Tg and recrystallize on further heating, achieving significantly higher crystallinity for pure PLLA than for doped nHA, 70 % vs 40 %, respectively. Additionally, PLLA/nHA fibers show a lower heat capacity for PLLA in the amorphous state, indicating that nHA reduces the molecular mobility of PLLA. Moreover, piezoelectric constant d33 was found to increase with the addition of nHA and for the aligned orientation of the fibers. In vitro tests confirmed that the addition of nHA and the aligned orientation of nanofibers increased osteoblast proliferation.

Fluorinated Porcine Bone-Derived Hydroxyapatite Promotes Vascularized Osteogenesis by Coordinating Human Bone Marrow Mesenchymal Stem Cell/Human Umbilical Vein Endothelial Cell Complexes

Biogenic hydroxyapatite is known for its osteoinductive potential due to its similarity to human bone and biocompatibility, but insufficient vascularization compared to autogenous bone during early implantation limits bone integration and osteogenesis. Fluorine has been shown to improve hydroxyapatite's mechanical properties and the coupling of osteogenic and angiogenic cells. In this study, fluorine-modified biogenic hydroxyapatite (FPHA) with varying fluorine concentrations was prepared and tested for its ability to promote vascularized osteogenesis. FPHA prepared in this study retained the natural porous structure of biological cancellous bone and released F- ions when immersed in cell culture medium. The extraction solutions of FPHA0.25 and FPHA0.50 promoted the formation of capillary-like tubes by human umbilical vein endothelial cells (HUVECs), with FPHA0.25 significantly upregulating vegf mRNA and VEGF protein levels in co-cultured human bone marrow mesenchymal stem cells (HBMSCs). Additionally, FPHA0.25 and FPHA0.50 upregulated pdgf-bb mRNA and PDGF-BB protein levels in HUVECs. In vivo experiments using a rabbit cranial defect model demonstrated that FPHA0.25 promoted early bone formation and angiogenesis in the defect area, enhanced VEGF secretion, and increased PDGFR-β expression in endothelial and mesenchymal cells. These findings suggest that fluorine-modified biogenic hydroxyapatite with an optimal fluorine concentration (FPHA0.25) may offer a promising strategy to enhance the body's innate bone-healing potential by accelerating vascularization.

Femtosecond laser direct writing Bombyx mori sericin-based nanocomposites into intrinsically soft wearable micro-/nano-electronics

Intrinsically flexible micro-/nano-electronics are increasingly in demand for wearable/implantable bio-machine interfacing optical electronics and soft robots. In this work, we developed intrinsically flexible and soft wearable micro-/nano-electronics by femtosecond laser direct writing Bombyx mori sericin-based nanocomposites. Sericin was used as the biomacromolecular reductant to photo-reduce metal ions into nanoparticles and the molecular matrix for in situ nano-compositing. The two/three-dimensional fabrication realized ∼350 nm minimum line width, customizable Young's modulus (∼0.22-3.35 GPa in air), and nano-scale morphology (∼12.1 nm average roughness). The electrical percolation and adjustable conductivity up to 105 S m-1 were studied. Within the sericin/Ag-nanocomposite percolation-threshold range, a miniaturized electro-mechano-sensor was prototyped with gauge factors (GF ∼ 16.95) and linearity (R2 ∼ 0.996), short response/recovery time (200 ms/120 ms), low detection limit (∼0.06% deformation) and power consumption (<0.1 mW), and remarkable intrinsic flexible performances (e.g., ∼104 time outward bendings). Cell/skin biocompatibilities and detections of human muscle/joint movements and sounds were demonstrated, promising its practical potential towards in vivo or in vitro bio-integrated electronics.

Fast bone regeneration using injectable fully biomimetic organoids with biomineralized and organic microenvironments

Bone defects and congenital bone deficiencies are common clinical conditions. However, conventional non-degradable artificial materials often lead to serious complications, such as severe infections and material displacement. The emergence of tissue engineering and the organoid concept presents a promising approach for the repair of bone defects, facilitating physiological reconstruction while minimizing complications. Nevertheless, previous studies have not developed injectable organoids that incorporate fully mineralized and organic microenvironments to achieve rapid osteogenesis and convenient application in bone regeneration. Therefore, it is imperative to devise an effective strategy to address these challenges. This study first prepared injectable GL scaffolds with varying concentrations and identified the optimal GL concentration (0.8%) for osteogenesis through systematic evaluation of the osteogenic efficiency. Subsequently, 30% mixture of inorganic salts of native bone (NBIS) and extracellular matrix from the periosteum (pECM) was integrated into the optimal GL scaffold at a ratio of NBIS : pECM = 7 : 3 to create an injectable scaffold featuring biomimetic mineralized and organic microenvironments. This scaffold was further utilized for in vitro analysis of osteogenic mechanisms and injected subcutaneously into rabbits for only four weeks to assess its osteogenic efficacy in vivo. The results indicated that the incorporation of NBIS and pECM significantly enhanced the osteogenic efficacy by actively regulating ossification and ECM-receptor interaction signaling pathways, as well as upregulating RUNX2, ALP, COL1, and LAMA. This study introduces a promising injectable strategy for rapid osteogenesis using fully mineralized and organic biomimetic organoids.

Clinical challenges in bone tissue engineering - A narrative review

Bone tissue engineering (BTE) has emerged as a promising approach to address large bone defects caused by trauma, infections, congenital malformations, and tumors. This review focuses on scaffold design, cell sources, growth factors, and vascularization strategies, highlighting their roles in developing effective treatments. We explore the complexities of balancing mechanical properties, porosity, and biocompatibility in scaffold materials, alongside optimizing mesenchymal stem cell delivery methods. The critical role of growth factors in bone regeneration and the need for controlled release systems are discussed. Vascularization remains a significant hurdle, with strategies such as angiogenic factors, co-culture systems, and bioprinting under investigation. Mechanical challenges, tissue responses, and inflammation management are examined, alongside gene therapy's potential for enhancing osteogenesis and angiogenesis via both viral and non-viral delivery methods. The review emphasizes the impact of patient-specific factors on bone healing outcomes and the importance of personalized approaches. Future directions are described, emphasizing the necessity of interdisciplinary cooperation to advance the field of BTE and convert laboratory results into clinically feasible solutions.

Composites of hydroxyapatite and their application in adsorption, medicine and as catalysts

Composites of hydroxyapatite, recognized by its peculiar crystal architecture and distinctive attributes showcased the potential in adsorbing heavy metal ions and radioactive elements as well as selected organic substances. In this paper, the intrinsic mechanism of adsorption by composites hydroxyapatite was proved for the first time. Subsequently, selectivity and competitiveness of composites of hydroxyapatite for a variety of environments containing various interferences from cations, anions, and organic molecules are elucidated. Next, composites of hydroxyapatite were further categorized according to their morphological dimensions. Adsorption properties and intrinsic mechanisms were investigated based on different morphologies. It was shown that although composites of hydroxyapatite were characterized by excellent adsorption capacity and cost-effectiveness, their application is often challenging due to inherent fragility and agglomeration, technical problems required for their handling as well as difficulty in recycling. Finally, to address these issues, the paper discusses the tendency of hydroxyapatite composites to adsorb heavy metal ions and radioactive elements as well as the limitations of their applications. Summarizing the limitations and future directions of modification of HAP in the field of heavy metal ions and different substances contamination abatement, the paper provides insightful perspectives for its gradual improvement and rational application.

Preferred Orientation of Hydroxyapatite Ceramics Along the c-Axis Promotes Osteoblast Differentiation

Hydroxyapatite (HAp) is similar to the main inorganic components of bone and tooth enamel. Furthermore, it possesses biocompatibility, making it suitable for clinical use in artificial bones. This study aimed to verify whether the preferred orientation of HAp influences osteogenesis. Using the templated grain growth method, we successfully fabricated HAp ceramics with a preferred orientation to m (a)-planes (aHAp) and examined the effects of this orientation on bone differentiation. Osteosarcoma-derived osteoblasts (MG-63) were cultured on aHAp and HAp ceramics made from commercially available powder (iHAp). Electron backscatter diffraction analysis revealed the crystal orientation distribution of HAp ceramics and the numerous exposed a-planes of aHAp. The MG-63 cultured on aHAp exhibited significantly higher alkaline phosphatase activity, a marker of early bone differentiation, compared to iHAp. Furthermore, the two-dimensional electrophoresis results indicated that the expressed proteins differed between aHAp and iHAp. These results indicate that controlling HAp's crystal structure may promote the osteogenic potential of osteoblasts. In this study, we propose that the a-plane of HAp promotes bone differentiation during the early stages, presenting a promising approach for novel biomaterials, such as high-performance artificial bones.

Investigate the in vitro biocompatibility, biodegradation, cytotoxicity, and differentiation potential of 3-D gelatin-nanocellulose composite scaffolds loaded with nanohydroxyapatite and simvastatin

Bone tissue engineering has been proposed as a promising solution for healing of bone fractures. An important aspect of bone tissue engineering is the implantable scaffolds that participate in the regeneration and repair of bone tissue. In this study, the composite scaffolds of gelatin- nanocellulose loaded with nanohydroxyapatite and simvastatin (as the osteoinductive component) were fabricated using freeze- drying method. Scaffolds were characterized in terms of morphology, mechanical, biodegradability, water absorption capacity, and simvastatin release characteristics. Also, the biocompatibility and differentiation potential of the scaffolds were evaluated on human bone marrow-derived mesenchymal stem cells using the MTT assay and alizarin red staining, respectively. The simvastatin loaded scaffolds showed a sustained release profile in vitro up to 216 h. The results of BMSCs differentiation by alizarin red staining showed significant differences between the simvastatin loaded group and other groups. Moreover, the results of MTT assay verified cytocompatibility and non-toxicity of the scaffolds. Therefore, the gelatin-nano cellulose composite scaffolds loaded with hydroxyapatite and simvastatin may be considered promising for use in bone tissue engineering.

Could CH3-M6P Be a Potential Dual-Functioning Candidate for Bone Regeneration?

Background: CI-RM6P has different binding sites with affinities for both M6P and IGF2, plays a role in the regulation of the TGF-β and IGF pathways that is important for controlling cell growth and differentiation. We hypothesize that previously synthesised derivative of M6P could be an alternative candidate for bone tissue regeneration in terms of higher binding affinity, stability in human serum, low cost and temporal delivery. Methods: CH3-M6P is synthesised based on previously described protocol; mesenchymal origin of isolated DPSCs was assessed by flow cytometry and AR staining prior to alkaline phosphatase (ALP) activity test, qPCR to evaluate differentiation specific marker expression, immunofluoresence, and SEM/EDS to evaluate organic and inorganic matrix formation; and rat aortic ring model to evaluate angiogenic effect of molecule. Results: CH3-M6P upregulated ALP activity, the expression of the ALP, Col1, RunX2, Mef2C, TGFβ1, TGFβ1R, TGFβ2, and Smad3 genes under osteogenic conditions. The results of immunofluorescence and SEM/EDS studies did not show enhancing effect on matrix formation. As we observed, the induction effect of CH3-M6P on the expression of angiogenic genes such as SMAD3 and TGFβ1R, even under osteogenic conditions, within the scope of research, we checked the angiogenic effect of the molecule and compared it to VEGF, showing that the CH3-M6P is really angiogenic. Conclusions: Our findings provide an important clue for the further exploration of the molecule, which can be necessary to enhance the capability of the commonly used osteomedium, possibly leading to the development of bone-forming drugs and has the potential to be a dual-functioning molecule for bone tissue engineering.

Dynamic-Cross-Linked, Regulated, and Controllable Mineralization Degree and Morphology of Collagen Biomineralization

The cross-linking process of collagen is one of the more important ways to improve the mineralization ability of collagen. However, the regulatory effect of dynamic cross-linking on biomineralization in vitro remains unclear. Dynamic-cross-linked mineralized collagen under different cross-linking processes, according to the process of cross-linking and mineralization of natural bone, was prepared in this study. Mineralization was performed for 12 h at 4, 8, and 12 h of collagen cross-linking. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the characteristics of dynamic-cross-linked mineralization in terms of morphological transformation and distribution. Fourier transform infrared spectroscopy (FTIR) analysis showed the crystallinity characteristics of the hydroxyapatite (HA) crystal formation. Pre-cross-linked dynamic-cross-linked mineralization refers to the process of cross-linking for a period of time and then side cross-linked mineralization. The mineral content, enzyme stability, and mechanical properties of mineralized collagen were improved through a dynamic cross-linking process of pre-cross-linking. The swelling performance was reduced through the dynamic cross-linking process of pre-cross-linking. This study suggests that the dynamic cross-linking process through pre-cross-linking could make it easier for minerals to permeate and deposit between collagen fibers, improve mineralization efficiency, and, thus, enhance the mechanical strength of biomineralization. This study can provide new ideas and a theoretical basis for designing mineralized collagen scaffolds with better bone repair ability.

A review of computational optimization of bone scaffold architecture: methods, challenges, and perspectives

The design and optimization of bone scaffolds are critical for the success of bone tissue engineering (BTE) applications. This review paper provides a comprehensive analysis of computational optimization methods for bone scaffold architecture, focusing on the balance between mechanical stability, biological compatibility, and manufacturability. Finite element method (FEM), computational fluid dynamics (CFD), and various optimization algorithms are discussed for their roles in simulating and refining scaffold designs. The integration of multiobjective optimization and topology optimization has been highlighted for developing scaffolds that meet the multifaceted requirements of BTE. Challenges such as the need for consideration of manufacturing constraints and the incorporation of degradation and bone regeneration models into the optimization process have been identified. The review underscores the potential of advanced computational tools and additive manufacturing techniques in evolving the field of BTE, aiming to improve patient outcomes in bone tissue regeneration. The reliability of current optimization methods is examined, with suggestions for incorporating non-deterministic approaches andin vivovalidations to enhance the practical application of optimized scaffolds. The review concludes with a call for further research into artificial intelligence-based methods to advance scaffold design and optimization.

Impact of Particle Size and Sintering Temperature on Calcium Phosphate Gyroid Structure Scaffolds for Bone Tissue Engineering

Due to the chemical composition and structure of the target tissue, autologous bone grafting remains the gold standard for orthopedic applications worldwide. However, ongoing advancements in alternative grafting materials show that 3D-printed synthetic biomaterials offer many advantages. For instance, they provide high availability, have low clinical limitations, and can be designed with a chemical composition and structure comparable to the target tissue. This study aimed to compare the influences of particle size and sintering temperature on the mechanical properties and biocompatibility of calcium phosphate (CaP) gyroid scaffolds. CaP gyroid scaffolds were fabricated by 3D printing using powders with the same chemical composition but different particle sizes and sintering temperatures. The physicochemical characterization of the scaffolds was performed using X-ray diffractometry, scanning electron microscopy, and microtomography analyses. The immortalized human mesenchymal stem cell line SCP-1 (osteoblast-like cells) and osteoclast-like cells (THP-1 cells) were seeded on the scaffolds as mono- or co-cultures. Bone cell attachment, number of live cells, and functionality were assessed at different time points over a period of 21 days. Improvements in mechanical properties were observed for scaffolds fabricated with narrow-particle-size-distribution powder. The physicochemical analysis showed that the microstructure varied with sintering temperature and that narrow particle size distribution resulted in smaller micropores and a smoother surface. Viable osteoblast- and osteoclast-like cells were observed for all scaffolds tested, but scaffolds produced with a smaller particle size distribution showed less attachment of osteoblast-like cells. Interestingly, low attachment of osteoclast-like cells was observed for all scaffolds regardless of surface roughness. Although bone cell adhesion was lower in scaffolds made with powder containing smaller particle sizes, the long-term function of osteoblast-like and osteoclast-like cells was superior in scaffolds with improved mechanical properties.

Influence of Hydroxyapatite and Gelatin Content on Crosslinking Dynamics and HDFn Cell Viability in Alginate Bioinks for 3D Bioprinting

This study investigates how varying concentrations of hydroxyapatite (OHAp) and the addition of gelatin influence the ionic crosslinking time of alginate-based bioinks, as well as the shear stress experienced by neonatal human dermal fibroblasts (HDFn) during extrusion. These factors are crucial for validating bioinks and developing viable 3D bioprinted models. Four bioink formulations were created with a 50/50 ratio of alginate to gelatin, incorporating different calcium phosphate concentrations (0%, 1%, 5%, and 10%). The bioink compositions were confirmed via Fourier Transform Infrared (FT-IR) spectroscopy, and rheological analyses evaluated their pseudoplastic behavior, printability limits, and crosslinking times. The results indicated a notable increase in the consistency index (k) from 0.32 for the 0% OHAp formulation to 0.48 for the 10% OHAp formulation, suggesting improved viscoelastic properties. The elastic modulus recovery after crosslinking rose significantly from 245 Pa to 455 Pa. HDFn experienced a shear stress of up to 1.5436 Pa at the tip during extrusion with the HDFn-ALG5-GEL5-OHAp10 bioinks, calculated at a shear rate as low as 2 s-1. Viability assays confirmed over 70% cell viability 24 h post-extrusion and 92% viability after 7 days for the 10% OHAp formulation, highlighting the potential of hydroxyapatite-enhanced bioinks in tissue engineering applications.

Biocompatible nanocomposite hydroxyapatite-based granules with increased specific surface area and bioresorbability for bone regenerative medicine applications

Hydroxyapatite (HA) granules are frequently used in orthopedics and maxillofacial surgeries to fill bone defects and stimulate the regeneration process. Optimal HA granules should have high biocompatibility, high microporosity and/or mesoporosity, and high specific surface area (SSA), which are essential for their bioabsorbability, high bioactivity (ability to form apatite layer on their surfaces) and good osseointegration with the host tissue. Commercially available HA granules that are sintered at high temperatures (≥ 900 °C) are biocompatible but show low porosity and SSA (2-5 m2/g), reduced bioactivity, poor solubility and thereby, low bioabsorbability. HA granules of high microporosity and SSA can be produced by applying low sintering temperatures (below 900 °C). Nevertheless, although HA sintered at low temperatures shows significantly higher SSA (10-60 m2/g) and improved bioabsorbability, it also exhibits high ion reactivity and cytotoxicity under in vitro conditions. The latter is due to the presence of reaction by-products. Thus, the aim of this study was to fabricate novel biomaterials in the form of granules, composed of hydroxyapatite nanopowder sintered at a high temperature (1100 °C) and a biopolymer matrix: chitosan/agarose or chitosan/β-1,3-glucan (curdlan). It was hypothesized that appropriately selected ingredients would ensure high biocompatibility and microstructural properties comparable to HA sintered at low temperatures. Synthesized granules were subjected to the evaluation of their biological, microstructural, physicochemical, and mechanical properties. The obtained results showed that the developed nanocomposite granules were characterized by a lack of cytotoxicity towards both mouse preosteoblasts and normal human fetal osteoblasts, and supported cell adhesion to their surface. Moreover, produced biomaterials had the ability to induce precipitation of apatite crystals after immersion in simulated body fluid, which, combined with high biocompatibility, should ensure good osseointegration after implantation. Additionally, nanocomposite granules possessed microstructural parameters similar to HA sintered at a low temperature (porosity approx. 50%, SSA approx. 30 m²/g), Young's modulus (5-8 GPa) comparable to cancellous bone, and high fluid absorption capacity. Moreover, the nanocomposites were prone to biodegradation under the influence of enzymatic solution and in an acidic environment. Additionally, it was noted that the hydroxyapatite nanoparticles remaining after the physicochemical dissolution of the biomaterial were easily phagocytosed by mouse macrophages, mouse preosteoblasts, and normal human fetal osteoblasts (in vitro studies). The obtained materials show great potential as bone tissue implantation biomaterials with improved bioresorbability. The obtained materials show great potential as bone tissue implantation biomaterials with improved bioresorbability.

Advances in 3D printing technology for preparing bone tissue engineering scaffolds from biodegradable materials

Introduction

Bone tissue engineering (BTE) provides an effective repair solution by implanting osteoblasts or stem cells into biocompatible and biodegradable scaffolds to promote bone regeneration. In recent years, the rapid development of 3D bioprinting has enabled its extensive application in fabricating BTE scaffolds. Based on three-dimensional computer models and specialized "bio-inks," this technology offers new pathways for customizing BTE scaffolds. This study reviews the current status and future prospects of scaffold materials for BTE in 3D bioprinting.

Methods

This literature review collected recent studies on BTE and 3D bioprinting, analyzing the advantages and limitations of various scaffold materials for 3D printing, including bioceramics, metals, natural polymers, and synthetic polymers. Key characteristics like biocompatibility, mechanical properties, and degradation rates of these materials were systematically compared.

Results

The study highlights the diverse performances of materials used in BTE scaffolds. Bioceramics exhibit excellent biocompatibility but suffer from brittleness; metals offer high strength but may induce chronic inflammation; natural polymers are biocompatible yet have poor mechanical properties, while synthetic polymers offer strong tunability but may produce acidic by-products during degradation. Additionally, integrating 3D bioprinting with composite materials could enhance scaffold biocompatibility and mechanical properties, presenting viable solutions to current challenges.

Discussion

This review summarizes recent advances in 3D bioprinting for BTE scaffold applications, exploring the strengths and limitations of various materials and proposing composite material combinations to improve scaffold performance. By optimizing material selection and combinations, 3D bioprinting shows promise for creating customized scaffolds, offering a new technical route for clinical applications of BTE. This research provides a unique perspective and theoretical support for advancing 3D bioprinting technology in bone regeneration, outlining future directions for BTE materials and 3D bioprinting technology development.

In Situ Synthesis and Characterizations of a Strontium-Substituted Dicalcium Phosphate Anhydrous/Hydroxyapatite Biphasic Whisker and Its Properties Evaluation

Dicalcium phosphate anhydrous (DCPA) presents good biomineralization ability, the strontium element is known for superior bone affinity, and a whisker possesses good mechanical strength; all these are beneficial for improving the drawbacks of hydroxyapatite (HAP) like weaker mechanical properties, poor biomineralization, and slower degradation/absorption. Therefore, a homogeneous precipitation was adopted to synthesize Sr-substituted and DCPA and HAP coexisting whiskers. The composition, structure, and morphology based on urea dosage and substitution content were characterized, and the roles of DCPA, Sr, and whisker shape were investigated. It turned out that Sr-DCPA/HAP biphasic products contained about 19% DCPA and 81% HAP, and both phases occupied the outer and inner parts of the whisker, respectively. Increasing the urea dosage made the morphology transform from a sea urchin shape to fiber clusters and then whiskers, while Sr substitution brought the whisker back to the porous microsphere shape. Only 5% of Sr content and 15 g of urea could maintain the whisker shape. Sr could promote the proliferation of MC3T3-E1 cells even at a higher extract concentration of 10 mg/mL. The cells stayed in a healthy state whether cocultured with the whisker or the microsphere. The unstable DCPA combined with the decreased crystallinity brought by Sr doping contributed to shortening the apatite deposition period to within 7 days. The whisker morphology enhanced the compressive strength of acrylic resin, and the apatite layer helped to reduce the strength loss during soaking. The Sr-DCPA/HAP biphasic whisker with enhanced overall properties possessed more promising potential for biomedical application.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Hydroxyapatite/Silk Fibroin Composite Scaffold with a Porous Structure and Mechanical Strength Similar to Cancellous Bone by Electric Field-Induced Gel Technology

Repair and regeneration of bone tissue defects is a multidimensional process that has been highly challenging to date. The artificial bone scaffold materials, which play a core role, still face the conflict that a biofriendly porous structure will reduce the mechanical performance and accelerate degradation. Herein, a multistage porous structured hydroxyapatite (HA)/silk fibroin (SF) composite scaffold (e-HA/SF) was successfully constructed by cleverly utilizing electric field-induced gel technology. The results indicated that the prepared e-HA/SF scaffolds possess biomimetic hierarchical porous structures with a suitable porosity similar to that of cancellous bone. The HA nanocrystals were uniformly encapsulated in the three-dimensional space of the composite scaffold, thus endowing the e-HA/SF composite scaffolds with an enhanced mechanical performance. Notably, the maximum compression stress and Young's modulus of e-HA/SF-2 scaffolds can reach 24.66 ± 0.88 and 28.91 ± 3.19 MPa, respectively, which are equivalent to those of cancellous bone. Such mechanical performance enhancement was previously unattainable through conventional freeze-drying strategies. Moreover, the introduction of bioactive nano-HA can trigger the optimal cell response in both static and dynamic cell culture experiments in vitro. The e-HA/SF composite scaffold developed in this study can better balance the conflict between the porous structure and mechanical and degradation properties of porous scaffolds.

Polysaccharide-based chondroitin sulfate macromolecule loaded hydrogel/scaffolds in wound healing- A comprehensive review on possibilities, research gaps, and safety assessment

Wound healing is an intricate multifactorial process that may alter the extent of scarring left by the wound. A substantial portion of the global population is impacted by non-healing wounds, imposing significant financial burdens on the healthcare system. The conventional dosage forms fail to improve the condition, especially in the presence of other morbidities. Thus, there is a pressing requirement for a type of wound dressing that can safeguard the wound site and facilitate skin regeneration, ultimately expediting the healing process. In this context, Chondroitin sulfate (CS), a sulfated glycosaminoglycan material, is capable of hydrating tissues and further promoting the healing. Thus, this comprehensive review article delves into the recent advancement of CS-based hydrogel/scaffolds for wound healing management. The article initially summarizes the various physicochemical characteristics and sources of CS, followed by a brief understanding of the importance of hydrogel and CS in tissue regeneration processes. This is the first instance of such a comprehensive summarization of CS-based hydrogel/scaffolds in wound healing, focusing more on the mechanistic wound healing process, furnishing the recent innovations and toxicity profile. This contemporary review provides a profound acquaintance of strategies for contemporary challenges and future direction in CS-based hydrogel/scaffolds for wound healing.

A Novel Triad of Bio-Inspired Design, Digital Fabrication, and Bio-Derived Materials for Personalised Bone Repair

The emerging paradigm of personalised bone repair embodies a transformative triad comprising bio-inspired design, digital fabrication, and the exploration of innovative materials. The increasing average age of the population, alongside the rising incidence of fractures associated with age-related conditions such as osteoporosis, necessitates the development of customised, efficient, and minimally invasive treatment modalities as alternatives to conventional methods (e.g., autografts, allografts, Ilizarov distraction, and bone fixators) typically employed to promote bone regeneration. A promising innovative technique involves the use of cellularised scaffolds incorporating mesenchymal stem cells (MSCs). The selection of materials-ranging from metals and ceramics to synthetic or natural bio-derived polymers-combined with a design inspired by natural sources (including bone, corals, algae, shells, silk, and plants) facilitates the replication of geometries, architectures, porosities, biodegradation capabilities, and mechanical properties conducive to physiological bone regeneration. To mimic internal structures and geometries for construct customisation, scaffolds can be designed using Computer-aided Design (CAD) and fabricated via 3D-printing techniques. This approach not only enables precise control over external shapes and internal architectures but also accommodates the use of diverse materials that improve biological performance and provide economic advantages. Finally, advanced numerical models are employed to simulate, analyse, and optimise the complex processes involved in personalised bone regeneration, with computational predictions validated against experimental data and in vivo studies to ascertain the model's ability to predict the recovery of bone shape and function.

Sericin Protein: Structure, Properties, and Applications

Silk sericin, the glue protein binding fibroin fibers together, is present in the Bombyx mori silkworms' cocoons. In recent years, sericin has gained attention for its wide range of properties and possible opportunities for various applications, as evidenced by the meta-analysis conducted in this review. Sericin extraction methods have evolved over the years to become more efficient and environmentally friendly, preserving its structure. Due to its biocompatibility, biodegradability, anti-inflammatory, antibacterial, antioxidant, UV-protective, anti-tyrosinase, anti-aging, and anti-cancer properties, sericin is increasingly used in biomedical fields like drug delivery, tissue engineering, and serum-free cell culture media. Beyond healthcare, sericin shows promise in industries such as textiles, cosmetics, and food packaging. This review aims to highlight recent advancements in sericin extraction, research, and applications, while also summarizing key findings from earlier studies.

Chitosan biomineralized with ions-doped nano-hydroxyapatite tunes osteoblasts metabolism and DNA damage

Hydroxyapatite (HA) is a bioceramic material widely used as a bone biomimetic substitute and can be synthesized by biomineralization, according to which HA nanoparticles are formed on a polymer template. Nevertheless, little is known about the effect of ion doping and biomineralization on cell metabolism, oxidative stress, and DNA damage. In the present contribution, we report on synthesizing and characterizing biomineralized chitosan as a polymer template with HA nanoparticles doped with magnesium (MgHA) and iron ions (FeHA). The physical-chemical and morphological characterization confirmed the successful synthesis of low crystalline ions-doped HA nanoparticles on the chitosan template, whereas the biochemical activity of the resulting nanoparticles towards human osteoblasts-like cells (MG63 and HOBIT) was investigated considering their effect on cell metabolism, proliferation, colony formation, redox status, and DNA damage extent. Data obtained suggest that particles enhance cell metabolism but partially limit cell proliferation. The redox status of cells was measured suggesting a slight increase in Reactive Oxygen Species production with chitosan biomineralized with iron-doped HA, whereas no effect with magnesium-doped HA and no effect of all formulations on the oxidation level of Peroxiredoxin. On the other hand, DNA damage was investigated by COMET assay, and expression and foci γH2AX. These latter tests indicated that HA-based nanoparticles promote DNA damage which is enhanced by chitosan thus suggesting that chitosan favors the nanoparticles' internalization by cells and modulates their biological activity. The potential DNA damage should be considered - and potentially exploited for instance in anticancer treatment - when HA-based particles are used to devise biomaterials.

Mussel shell-derived biogenic hydroxyapatite as reinforcement on chitosan-loaded gentamicin composite for antibacterial activity and bone regeneration

In this study, hydroxyapatite (HAp) was synthesized from natural biowaste materials, specifically mussel shells, and combined with chitosan (CS) and gentamicin sulfate antibiotic (GA) using an in-situ method. The resulting composite material, designated HAp/CS-GA, has its physicochemical and structural properties characterized by Fourier transform infrared spectroscopy (FTIR) analysis. The structure was confirmed by X-ray diffraction (XRD) analysis. Additionally, field emission scanning electron microscopy (FE-SEM) equipped with the energy dispersive X-ray spectroscopic (EDX) technique was used to determine the surface topography and main components. The composite of HAp/CS-GA was analyzed using a drug release profile by UV-visible spectroscopy (UV-Vis). The fabricated composites antimicrobial behavior was examined against bone infection-causing Gram-positive and Gram-negative bacteria, showing potential activity against Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus compared to Escherichia coli, respectively. Simultaneously, the cytotoxicity of the composite was evaluated by MTT assay using an MG-63 osteoblast-like cell line that exhibited no toxicity in the prepared composite. After a 24 h incubation period, the MG-63 cells on the HAp/CS-GA composite showed good proliferation, according to Hoechst 33258 fluorescence staining results. The results suggested that the composite had excellent biocompatibility and antibacterial activity and enhanced the osteoblast cell proliferation. Therefore, the designed HAp/CS-GA composite would be a promising candidate for bone tissue engineering.

Construction Form and Application of Three-Dimensional Bioprinting Ink Containing Hydroxyapatite

With the increasing prevalence of bone tissue diseases, three-dimensional (3D) bioprinting applied to bone tissue engineering for treatment has received a lot of interests in recent years. The research and popularization of 3D bioprinting in bone tissue engineering require bioinks with good performance, which is closely related to ideal material and appropriate construction form. Hydroxyapatite (HAp) is the inorganic component of natural bone and has been widely used in bone tissue engineering and other fields due to its good biological and physicochemical properties. Previous studies have prepared different bioinks containing HAp and evaluated their properties in various aspects. Most bioinks showed significant improvement in terms of rheology and biocompatibility; however, not all of them had sufficiently favorable mechanical properties and antimicrobial activity. The deficiencies in properties of bioink and 3D bioprinting technology limited the applications of bioinks containing HAp in clinical trials. This review article summarizes the construction forms of bioinks containing HAp and its modifications in previous studies, as well as the 3D bioprinting techniques adopted to print bioink containing HAp. In addition, this article summarizes the advantages and underlying mechanisms of bioink containing HAp, as well as its limitations, and suggests possible improvement to facilitate the development of bone tissue engineering bioinks containing HAp in the future.

An Up-to-Date Review of Materials Science Advances in Bone Grafting for Oral and Maxillofacial Pathology

Bone grafting in oral and maxillofacial surgery has evolved significantly due to developments in materials science, offering innovative alternatives for the repair of bone defects. A few grafts are currently used in clinical settings, including autografts, xenografts, and allografts. However, despite their benefits, they have some challenges, such as limited availability, the possibility of disease transmission, and lack of personalization for the defect. Synthetic bone grafts have gained attention since they have the potential to overcome these limitations. Moreover, new technologies like nanotechnology, 3D printing, and 3D bioprinting have allowed the incorporation of molecules or substances within grafts to aid in bone repair. The addition of different moieties, such as growth factors, stem cells, and nanomaterials, has been reported to help mimic the natural bone healing process more closely, promoting faster and more complete regeneration. In this regard, this review explores the currently available bone grafts, the possibility of incorporating substances and molecules into their composition to accelerate and improve bone regeneration, and advanced graft manufacturing techniques. Furthermore, the presented current clinical applications and success stories for novel bone grafts emphasize the future potential of synthetic grafts and biomaterial innovations in improving patient outcomes in oral and maxillofacial surgery.

Direct, Broad-Spectrum Antimicrobial Activity of Ag+-Doped Hydroxyapatite against Fastidious Anaerobic Periodontal and Aerobic Dental Bacteria

Periodontitis and caries, while seemingly innocuous medical conditions, actually pose significant challenges because of their potential etiology with far more serious conditions. Efficacious treatment is hindered by bacterial antibiotic resistance. Standard AgNPs are ineffective against periodontal anaerobic bacteria, because they require oxidative dissolution to release Ag+ ions, which are the actual antimicrobial agents, but oxidation is not possible under anaerobic conditions. Prior studies on Ag-based periodontal antimicrobial materials either did not confirm a silver oxidation state or did not use strictly anaerobic growth media or both, causing spurious antimicrobial efficacy estimates. Here, we prove that silver ion-doped hydroxyapatite nanoparticles (AgHAp NPs) synthesized at various pHs contain an Ag+ oxidation state and directly release Ag+ even in a strictly anerobic medium. Thus, these AgHAp NPs exhibit direct antimicrobial activity against the fastidious anaerobic Gram-negative periodontal bacterium Fusobacterium nucleatum (F. nucleatum) and against caries-causing aerobic, Gram-positive bacterium Streptococcus mutans (S. mutans). The synthesis pH (6-11) correlates inversely with the Ag+ content (4.5-0.45 wt %) of AgHAp NPs and, hence, with antimicrobial efficacy, thus providing tunable efficacy for the target application. AgHAp NPs had greater antimicrobial efficacy than Ag0-containing AgNPs and were less cytotoxic to the mouse fibroblast L929 cell line. Thus, AgHAp NPs (especially AgHAp7) are superior to AgNPs as effective, broad-spectrum, biocompatible antimicrobials against both anaerobic periodontal and aerobic dental bacteria. AgHAp NP synthesis is also inexpensive and scalable, which are significant factors for treating large global populations of indigent people affected by periodontitis and dental caries.

Osteogenic potentials in canine mesenchymal stem cells: unraveling the efficacy of polycaprolactone/hydroxyapatite scaffolds in veterinary bone regeneration

BACKGROUND

The integration of stem cells, signaling molecules, and biomaterial scaffolds is fundamental for the successful engineering of functional bone tissue. Currently, the development of composite scaffolds has emerged as an attractive approach to meet the criteria of ideal scaffolds utilized in bone tissue engineering (BTE) for facilitating bone regeneration in bone defects. Recently, the incorporation of polycaprolactone (PCL) with hydroxyapatite (HA) has been developed as one of the suitable substitutes for BTE applications owing to their promising osteogenic properties. In this study, a three-dimensional (3D) scaffold composed of PCL integrated with HA (PCL/HA) was prepared and assessed for its ability to support osteogenesis in vitro. Furthermore, this scaffold was evaluated explicitly for its efficacy in promoting the proliferation and osteogenic differentiation of canine bone marrow-derived mesenchymal stem cells (cBM-MSCs) to fill the knowledge gap regarding the use of composite scaffolds for BTE in the veterinary orthopedics field.

RESULTS

Our findings indicate that the PCL/HA scaffolds substantially supported the proliferation of cBM-MSCs. Notably, the group subjected to osteogenic induction exhibited a markedly upregulated expression of the osteogenic gene osterix (OSX) compared to the control group. Additionally, the construction of 3D scaffold constructs with differentiated cells and an extracellular matrix (ECM) was successfully imaged using scanning electron microscopy. Elemental analysis using a scanning electron microscope coupled with energy-dispersive X-ray spectroscopy confirmed that these constructs possessed the mineral content of bone-like compositions, particularly the presence of calcium and phosphorus.

CONCLUSIONS

This research highlights the synergistic potential of PCL/HA scaffolds in concert with cBM-MSCs, presenting a multidisciplinary approach to scaffold fabrication that effectively regulates cell proliferation and osteogenic differentiation. Future in vivo studies focusing on the repair and regeneration of bone defects are warranted to further explore the regenerative capacity of these constructs, with the ultimate goal of assessing their potential in veterinary clinical applications.

The protective effects of chitosan and curcumin nanoparticles against the hydroxyapatite nanoparticles-induced neurotoxicity in rats

Hydroxyapatite nanoparticles (HANPs) have extensive applications in biomedicine and tissue engineering. However, little information is known about their toxicity. Here, we aim to investigate the possible neurotoxicity of HANPs and the possible protective role of chitosan nanoparticles (CNPs) and curcumin nanoparticles (CUNPs) against this toxicity. In our study, HANPs significantly reduced the levels of neurotransmitters, including acetylcholine (Ach), dopamine (DA), serotonin (SER), epinephrine (EPI), and norepinephrine (NOR). HANPs significantly suppressed cortical expression of the genes controlling mitochondrial biogenesis such as peroxisome proliferator activator receptor gamma coactivator 1α (PGC-1α) and mitochondrial transcription factor A (mTFA). Our findings revealed significant neuroinflammation associated with elevated apoptosis, lipid peroxidation, oxidative DNA damage and nitric oxide levels with significant decline in the antioxidant enzymes activities and glutathione (GSH) levels in HANPs-exposed rats. Meanwhile, co-supplementation of HANP-rats with CNPs and/or CUNPs significantly showed improvement in levels of neurotransmitters, mitochondrial biogenesis, oxidative stress, DNA damage, and neuroinflammation. The co-supplementation with both CNPs and CUNPs was more effective to ameliorate HANPs-induced neurotoxicity than each one alone. So, CNPs and CUNPs could be promising protective agents for prevention of HANPs-induced neurotoxicity.

Effectiveness of the Association of Fibrin Scaffolds, Nanohydroxyapatite, and Photobiomodulation with Simultaneous Low-Level Red and Infrared Lasers in Bone Repair

Biomaterials and biopharmaceuticals for correcting large bone defects are a potential area of translational science. A new bioproduct, purified from snake venom and fibrinogen from buffalo blood, aroused interest in the repair of venous ulcers. Expanding potential uses, it has also been used to form biocomplexes in combination with bone grafts, associated with physical therapies or used alone. The aim of this preclinical study was to evaluate low-level laser photobiomodulation (PBM) in critical defects in the calvaria of rats filled with nanohydroxyapatite (NH) associated with the heterologous fibrin biopolymer (HFB). Sixty animals were used, divided into six groups (n = 10 each): G1 (NH); G2 (HFB); G3 (NH + HFB); G4 (NH + PBM); G5 (HFB + PBM); G6 (NH + HFB + PBM). PBM simultaneously used red (R) and infrared (IR) light emission, applied intraoperatively and twice a week, until the end of the experiment at 42 days. Microtomography, bone formation can be seen initially at the margins of the defect, more evident in G5. Microscopically, bone formation demonstrated immature and disorganized trabeculation at 14 days, with remnants of grafting materials. At 42 days, the percentage of new bone formed was higher in all groups, especially in G5 (HFB, 45.4 ± 3.82), with collagen fibers at a higher degree of maturation and yellowish-green color in the birefringence analysis with Picrosirius-red. Therefore, it is concluded that the HFB + PBM combination showed greater effectiveness in the repair process and presents potential for future clinical studies.

Advances in hyaluronic acid: Bioactivity, complexed biomaterials and biological application: A review

Hyaluronic acid (HA) is a natural glycosaminoglycan found in the human body, particularly in the extracellular matrix of body fluids and tissues. It plays a critical role in cellular processes of living organisms by maintaining tissue hydration, cell proliferation, differentiation, and inflammatory response. HA exhibits significant biological activity in skin care, aesthetic anti-aging, medical orthopedic repair, gynecological cancer monitoring, and other pathological conditions. Due to its exceptional biocompatibility, biodegradability, lack of toxicity, non-immunogenicity, and its capacity to bond with other substances, various HA-based biomedical products like hydrogels, microneedles, and microspheres have been developed. These innovations have also been applied in various medical and health fields, such as bone and tissue regeneration, gels for medical aesthetic fillers, and gynecology-related cancer treatment, utilizing the HA drug delivery pathway. The interest in HA and its products is increasing due to their biological functions. Therefore, this review aimed to summarize the biological properties of HA and to focus on its applications in the bone tissue engineering and healthcare, for HA has some practical applications of HA-based complexes in biomedical materials, tissue repair, medical aesthetics, and gynecology. Through this review, we seek to offer theoretical research assistance for the development of HA-based bioproducts in the healthcare domain and provide innovative insights for human health.

Prospective applications of bioactive materials in orthopedic therapies: A review

The biomedical application of biodegradable polymers for addressing bone-related diseases has garnered considerable attention in recent years. Advances in material technology have expanded the repertoire of materials suitable for orthopedic implants, with nanomaterials playing a pivotal role in replicating crucial surface properties akin to natural tissues. This comprehensive review explores the evaluation of bioactive glass ceramics, shedding light on their properties and applications. The synthesis of composites through composite manufacturing has emerged as a strategy to enhance biocompatibility and biomechanical characteristics. They are addressing challenges associated with conventional implants and nanomaterials, whether in the form of functional nano coatings or nanostructured surfaces, present opportunities to refine implant techniques. Novel developments in orthopedic biomaterials, such as smart biomaterials, porous structures, and 3D implants, offer stimuli-responsive behavior to achieve desired implant shapes and characteristics. Bioactive and biodegradable porous polymer/inorganic composite materials are explored for bone tissue engineering scaffolds, aiming to promote bone formation and regeneration. As a prospective direction, the integration of stem cells into scaffolds hints at the creation of next-generation synthetic/living hybrid biomaterials, displaying high adaptability in biological settings. This review establishes a foundation for nanotechnology-driven biomaterials by elucidating fundamental design factors crucial for orthopedic implant performance and their response to cell differentiation, proliferation, and adhesion.

Hydroxyapatite-Based Natural Biopolymer Composite for Tissue Regeneration

Hydroxyapatite (HAp) polymer composites have gained significant attention due to their applications in bone regeneration and tooth implants. This review examines the synthesis, properties, and applications of Hap, highlighting various manufacturing methods, including wet, dry, hydrothermal, and sol-gel processes. The properties of HAp are influenced by precursor materials and are commonly obtained from natural calcium-rich sources like eggshells, seashells, and fish scales. Composite materials, such as cellulose-hydroxyapatite and gelatin-hydroxyapatite, exhibit promising strength and biocompatibility for bone and tissue replacement. Metallic implants and scaffolds enhance stability, including well-known titanium-based and stainless steel-based implants and ceramic body implants. Biopolymers, like chitosan and alginate, combined with Hap, offer chemical stability and strength for tissue engineering. Collagen, fibrin, and gelatin play crucial roles in mimicking natural bone composition. Various synthesis methods like sol-gel, hydrothermal, and solution casting produce HAp crystals, with potential applications in bone repair and regeneration. Additionally, the use of biowaste materials, like eggshells and snails or seashells, not only supports sustainable HAp production but also reduces environmental impact. This review emphasizes the significance of understanding the properties of calcium-phosphate (Ca-P) compounds and processing methods for scaffold generation, highlighting novel characteristics and mechanisms of biomaterials in bone healing. Comparative studies of these methods in specific applications underscore the versatility and potential of HAp composites in biomedical engineering. Overall, HAp composites offer promising solutions for improving patient outcomes in bone replacement and tissue engineering and advancing medical practices.

Collagen-hydroxyapatite based scaffolds for bone trauma and regeneration: recent trends and future perspectives

Regenerative therapy, a key area of tissue engineering, holds promise for restoring damaged organs, especially in bone regeneration. Bone healing is natural to the body but becomes complex under stress and disease. Large bone deformities pose significant challenges in tissue engineering. Among various methods, scaffolds are attractive as they provide structural support and essential nutrients for cell adhesion and growth. Collagen and hydroxyapatite (HA) are widely used due to their biocompatibility and biodegradability. Collagen and nano-scale HA enhance cell adhesion and development. Thus, nano HA/collagen scaffolds offer potential solutions for bone regeneration. This review focuses on the use and production of nano-sized HA/collagen composites in bone regeneration.

Recent advances of bone tissue engineering: carbohydrate and ceramic materials, fundamental properties and advanced biofabrication strategies ‒ a comprehensive review

Bone is a dynamic tissue that can always regenerate itself through remodeling to maintain biofunctionality. This tissue performs several vital physiological functions. However, bone scaffolds are required for critical-size damages and fractures, and these can be addressed by bone tissue engineering. Bone tissue engineering (BTE) has the potential to develop scaffolds for repairing critical-size damaged bone. BTE is a multidisciplinary engineered scaffold with the desired properties for repairing damaged bone tissue. Herein, we have provided an overview of the common carbohydrate polymers, fundamental structural, physicochemical, and biological properties, and fabrication techniques for bone tissue engineering. We also discussed advanced biofabrication strategies and provided the limitations and prospects by highlighting significant issues in bone tissue engineering. There are several review articles available on bone tissue engineering. However, we have provided a state-of-the-art review article that discussed recent progress and trends within the last 3-5 years by emphasizing challenges and future perspectives.

Synthetic or Natural (Bio-Based) Hydroxyapatite? A Systematic Comparison between Biomimetic Nanostructured Coatings Produced by Ionized Jet Deposition

Calcium phosphate (CaP)-based materials are largely explored in orthopedics, to increase osseointegration of the prostheses and specifically in spine surgery, to permit better fusion. To address these aims, nanostructured biogenic apatite coatings are emerging, since they better mimic the characteristics of the host tissue, thus potentially being better candidates compared to their synthetic counterpart. Here, we compare hydroxyapatite (HA) nanostructured coatings, obtained by ionized jet deposition, starting from synthetic and natural sources. The starting materials and the corresponding films are characterized and compared from a compositional and morphological point of view, then their stability is studied after post-treatment annealing. Although all the films are formed by globular aggregates and show morphological features at different scales (from nano to micro), significant differences are found in composition between the synthetic and naturally derived HA in terms of magnesium and sodium content, carbonate substitution and Ca/P ratio, while differences between the coatings obtained by the different natural HA sources are minor. In addition, the shape of the aggregates is also target-dependent. All coatings have a good stability after over 14 days of immersion in medium, with natural apatite coatings showing a better behavior, as no cracking and detachments are observed during immersion. Based on these results, both synthetic and naturally derived apatitic materials appear promising for applications in spine surgery, with coatings from natural sources possessing physiochemical properties more similar to the mineral phase of the human bone tissue.

Are We Overlooking Harms of BDDE-Cross-Linked Dermal Fillers? A Scoping Review

1,4-Butanediol ether (BDDE) is widely used as a cross-linker for hyaluronic acid in dermal fillers. The purpose of this scoping review was to determine the state of knowledge about the behaviour of cross-linked substances and safety of BDDE application. The rationale behind the review came from the clinical experience of one of the authors (KS), who noticed adverse reactions after BDDE-linked hyaluronan application. The scoping review was conducted according to PRISMA-ScR guidelines. Out of 399 articles, 52 met the inclusion criteria. Data on study design, sample/population, aims, methodology, outcomes and funding were extracted. Results were charted according to 6 subtopics: rheological properties, hydrogel stability, BDDE toxicity, immunogenicity, tissue interactions and clinical studies. In vitro, cross-linked hydrogels were characterized as effective fillers in terms of viscosity and elasticity; however, previously uncharacterized by-products of the cross-linking reaction were found. Most in vivo studies reported increased dermis regeneration, vascularization and anti-inflammatory cytokine release after implantation of BDDE-cross-linked substances. In clinical studies, BDDE was shown to sensitize subjects to 1,6-hexanediol ether and other substances found in epoxy resin systems. Occupational dermatitis and hypersensitivity reactions were documented. Our review shows that BDDE may have long-term adverse effects, which are overlooked in the safety assessment of fillers. Reviews on BDDE conducted so far have mostly been sponsored by the industry, potentially leading to incomplete reporting of adverse effects. A review of the occurrence of allergic reactions after commercial dermal filler use and analysis of possibly harmful by-products of BDDE hyaluronan degradation are needed.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Synthetic composites versus calcium phosphate cements in bone regeneration: A narrative review

BACKGROUND

When the natural process of bone remodeling is disturbed, the need arises for a stimulant material in order to enhance the formation of a new healthy and strong osseous tissue to replace the damaged one. Recent studies have reported synthetic biomaterials to be a very good option for supporting bone regeneration.

STUDY DESIGN

Narrative review.

OBJECTIVE

This review aims to provide a brief presentation of two of the most recently developed synthetic biomaterials, i.e. calcium phosphate cements and synthetic composites, that are currently being used in bone regeneration with promising results.

METHODS

Literature searches using broad terms such as "bone regeneration," "biomaterials," "synthetic composites" and "calcium phosphate cements" were performed using PubMed. The osteal cells state of the art was explored by searching topic-specific full text keywords using Google Scholar.

CONCLUSIONS

Synthetic polymers such as PCL (poly-ε-caprolactone) and PLGA (poly lactic-co-glycolic acid) can improve the effectiveness of biomaterials like HA (hydroxyapatite) and BG (bioglass). Calcium phosphate, although being a suitable material for stimulating bone regeneration, needs an adjuvant in order to be effective in larger bone defects.

Biomimetic Marine-Sponge-Derived Spicule-Microparticle-Mediated Biomineralization and YAP/TAZ Pathway for Bone Regeneration In Vivo

Marine-sponge-derived spicule microparticles (SPMs) possess unique structural and compositional features suitable for bone tissue engineering. However, significant challenges remain in establishing their osteogenic mechanism and practical application in animal models. This study explores the biomimetic potential of SPM in orchestrating biomineralization behavior and modulating the Yes-associated protein 1/transcriptional coactivator with PDZ-binding motif (YAP/TAZ) pathway both in vitro and in vivo. Characterization of SPM revealed a structure comprising amorphous silica oxide mixed with collagen and trace amounts of calcium and phosphate ions, which have the potential to facilitate biomineralization. Structural analysis indicated dynamic biomineralization from SPM to hydroxyapatite, contributing to both in vitro and in vivo osteoconductions. In vitro assessment demonstrated dose-dependent increases in osteogenic gene expression and bone morphogenetic protein-2 protein in response to SPM. In addition, focal adhesion mediated by silica diatoms induced cell spreading on the surface of SPM, leading to cell alignment in the direction of SPM. Mechanical signals from SPM subsequently increased the expression of YAP/TAZ, thereby inducing osteogenic mechanotransduction. The osteogenic activity of SPM-reinforced injectable hydrogel was evaluated in a mouse calvaria defect model, demonstrating rapid vascularized bone regeneration. These findings suggest that biomimetic SPM holds significant promise for regenerating bone tissue.

From electricity to vitality: the emerging use of piezoelectric materials in tissue regeneration

The unique ability of piezoelectric materials to generate electricity spontaneously has attracted widespread interest in the medical field. In addition to the ability to convert mechanical stress into electrical energy, piezoelectric materials offer the advantages of high sensitivity, stability, accuracy and low power consumption. Because of these characteristics, they are widely applied in devices such as sensors, controllers and actuators. However, piezoelectric materials also show great potential for the medical manufacturing of artificial organs and for tissue regeneration and repair applications. For example, the use of piezoelectric materials in cochlear implants, cardiac pacemakers and other equipment may help to restore body function. Moreover, recent studies have shown that electrical signals play key roles in promoting tissue regeneration. In this context, the application of electrical signals generated by piezoelectric materials in processes such as bone healing, nerve regeneration and skin repair has become a prospective strategy. By mimicking the natural bioelectrical environment, piezoelectric materials can stimulate cell proliferation, differentiation and connection, thereby accelerating the process of self-repair in the body. However, many challenges remain to be overcome before these concepts can be applied in clinical practice, including material selection, biocompatibility and equipment design. On the basis of the principle of electrical signal regulation, this article reviews the definition, mechanism of action, classification, preparation and current biomedical applications of piezoelectric materials and discusses opportunities and challenges for their future clinical translation.

Engineering Large-Scale Self-Mineralizing Bone Organoids with Bone Matrix-Inspired Hydroxyapatite Hybrid Bioinks

Addressing large bone defects remains a significant challenge owing to the inherent limitations in self-healing capabilities, resulting in prolonged recovery and suboptimal regeneration. Although current clinical solutions are available, they have notable shortcomings, necessitating more efficacious approaches to bone regeneration. Organoids derived from stem cells show great potential in this field; however, the development of bone organoids has been hindered by specific demands, including the need for robust mechanical support provided by scaffolds and hybrid extracellular matrices (ECM). In this context, bioprinting technologies have emerged as powerful means of replicating the complex architecture of bone tissue. The research focused on the fabrication of a highly intricate bone ECM analog using a novel bioink composed of gelatin methacrylate/alginate methacrylate/hydroxyapatite (GelMA/AlgMA/HAP). Bioprinted scaffolds facilitate the long-term cultivation and progressive maturation of extensive bioprinted bone organoids, foster multicellular differentiation, and offer valuable insights into the initial stages of bone formation. The intrinsic self-mineralizing quality of the bioink closely emulates the properties of natural bone, empowering organoids with enhanced bone repair for both in vitro and in vivo applications. This trailblazing investigation propels the field of bone tissue engineering and holds significant promise for its translation into practical applications.

Biomimetic Hydrogel Strategies for Cancer Therapy

Recent developments in biomimetic hydrogel research have expanded the scope of biomedical technologies that can be used to model, diagnose, and treat a wide range of medical conditions. Cancer presents one of the most intractable challenges in this arena due to the surreptitious mechanisms that it employs to evade detection and treatment. In order to address these challenges, biomimetic design principles can be adapted to beat cancer at its own game. Biomimetic design strategies are inspired by natural biological systems and offer promising opportunities for developing life-changing methods to model, detect, diagnose, treat, and cure various types of static and metastatic cancers. In particular, focusing on the cellular and subcellular phenomena that serve as fundamental drivers for the peculiar behavioral traits of cancer can provide rich insights into eradicating cancer in all of its manifestations. This review highlights promising developments in biomimetic nanocomposite hydrogels that contribute to cancer therapies via enhanced drug delivery strategies and modeling cancer mechanobiology phenomena in relation to metastasis and synergistic sensing systems. Creative efforts to amplify biomimetic design research to advance the development of more effective cancer therapies will be discussed in alignment with international collaborative goals to cure cancer.

Comparative Analysis of Osteointegration in Hydroxyapatite and Hydroxyapatite-Titanium Implants: An In Vivo Rabbit Model Study

The study evaluates the osteointegration of hydroxyapatite (HAp) and hydroxyapatite-titanium (HApTi) biocomposites implanted in the femurs of rabbits. The biocomposites were fabricated using powder metallurgy and subjected to a two-step sintering process. Scanning electron microscopy (SEM) was employed to analyze the morphology, while mesenchymal stem cells were cultured to assess cytotoxicity and proliferation. In vivo experiments involved the implantation of HAp in the left femur and HApTi in the right femur of twenty New Zealand white rabbits. Computed tomography (CT) scans, histological, immunohistochemical, and histomorphometric analyses were performed to assess bone density and osteoblast activity. Results demonstrated that HApTi implants showed superior osteointegration, with higher peri-implant bone density and increased osteoblast count compared to HAp implants. This study concluded that HApTi biocomposites have potential for enhanced bone healing and stability in orthopedic applications.

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Antitumoral-Embedded Biopolymeric Spheres for Implantable Devices

The bioactive surface modification of implantable devices paves the way towards the personalized healthcare practice by providing a versatile and tunable approach that increase the patient outcome, facilitate the medical procedure, and reduce the indirect or secondary effects. The purpose of our study was to assess the performance of composite coatings based on biopolymeric spheres of poly(lactide-co-glycolide) embedded with hydroxyapatite (HA) and methotrexate (MTX). Bio-simulated tests performed for up to one week evidenced the gradual release of the antitumor drug and the biomineralization potential of PLGA/HA-MTX sphere coatings. The composite materials proved superior biocompatibility and promoted enhanced cell adhesion and proliferation with respect to human preosteoblast and osteosarcoma cell lines when compared to pristine titanium.

In vitro corrosion and cytocompatibility of Mg-Zn-Ca alloys coated with FHA

In the field of orthopedics, it's crucial to effectively slow down the degradation rate of Mg alloys. This study aims to improve the degradation behavior of Mg-Zn-Ca alloys by electrodepositing fluorohydroxyapatite (FHA). We investigated the microstructure and bond strength of the deposition, as well as degradation and cellular reactions. After 15-30 days of degradation in Hanks solution, FHA deposited alloys showed enhanced stability and less pH change. The strong interfacial bond between FHA and the Mg-Zn-Ca substrate was verified through scratch tests (Critical loads: 10.73 ± 0.014 N in Mg-Zn-0.5Ca alloys). Cellular studies demonstrated that FHA-coated alloys exhibited good cytocompatibility and promoted the growth of MC3T3-E1 cells. Further tests showed FHA-coated alloys owed improved early bone mineralization and osteogenic properties, especially in Mg-Zn-0.5Ca. This research highlighted the potential of FHA-coated Mg-Zn-0.5Ca alloys in orthopedics applications.