Strontium-substituted hydroxyapatite grown on graphene oxide nanosheet-reinforced chitosan scaffold to promote bone regeneration

Exploring the role of strontium-based nanoparticles in modulating bone regeneration and antimicrobial resistance: a public health perspective

Strontium-based nanoparticles (SrNPs) have emerged as a versatile and promising class of nanomaterials with a wide range of potential applications in healthcare, particularly in the fields of bone regeneration and combating antimicrobial resistance (AMR). Recent research has highlighted the unique properties of SrNPs, including their ability to promote osteogenesis, enhance bone healing, and exhibit strong antimicrobial activity against multidrug-resistant pathogens. These attributes position SrNPs as innovative therapeutic agents with the potential to address challenges such as osteoporosis, bone infections, and the growing global AMR crisis. This comprehensive review critically examines the dual functional potential of SrNPs by analyzing their synthesis methods, physicochemical properties, biological interactions, and translational applications in orthopedic and antimicrobial therapies. Specifically, the review emphasizes SrNPs' ability to enhance bone density, accelerate fracture healing, and reduce the economic burden associated with prolonged treatment and rehabilitation for bone-related diseases. Furthermore, their novel application as antimicrobial agents is explored, highlighting their ability to target bacterial metabolic pathways and combat the rise of antibiotic resistance. The review focuses on the synthesis methods used for SrNPs, particularly co-precipitation, hydrothermal synthesis, and sol-gel techniques. Each method is explored for its ability to produce SrNPs with controlled size, shape, and functionality, while addressing their scalability, cost-effectiveness, and environmental impact. Additionally, the toxicological risks associated with SrNPs are also explored, emphasizing the need for comprehensive preclinical and clinical evaluations to ensure safety for humans and ecosystems. The regulatory and ethical landscape of SrNPs highlights the need for global safety protocols, equitable access, and international cooperation to ensure ethical nanotechnology use. Environmental fate studies address bioaccumulation risks and ecological concerns. This review identifies opportunities and challenges in advancing bone regenerative medicine and combating AMR while emphasizing sustainable and ethical SrNP development for researchers, policymakers, and stakeholders.

3D-Printed PCL/SrHA@DFO Bone Tissue Engineering Scaffold with Bone Regeneration and Vascularization Function

The application of a three-dimensional (3D)-printed biological functional scaffold in the repair of bone defects is a promising strategy. In this study, strontium-containing hydroxyapatite (SrHA) powder was synthesized by the hydrothermal method, and then poly(ε-caprolactone) (PCL)/HA and PCL/SrHA composite scaffolds were prepared by the high-temperature melt extrusion 3D printing technology. The basic physical and chemical properties, in vitro biological properties, osteogenesis, and angiogenesis abilities of the scaffold were studied. The results showed that HA and SrHA were uniformly embedded in the composite scaffold, and the scaffold exhibited a 3D interconnected porous structure and rough microsurface. The in vitro release curve showed that Sr2+ and Ca2+ were continuously released from the PCL/SrHA scaffold. In order to verify the performance of the composite scaffold in bone regeneration, the proliferation and osteogenic differentiation of mouse embryonic osteoblasts (MC3T3E1) grown on the scaffold were evaluated. The experimental results showed that the incorporation of SrHA significantly promoted cell proliferation. Compared with the PCL/HA scaffold, the PCL/SrHA scaffold could better promote cell osteogenic differentiation. Deferoxamine (DFO) was loaded on the surface of the PCL/SrHA scaffold. By studying the proliferation, angiogenesis, and expression of osteogenesis and angiogenesis-related genes of human umbilical vein endothelial cells (HUVECs) on PCL/SrHA@DFO scaffold, it was verified that DFO had the ability to promote angiogenesis. It could induce angiogenesis in vitro in combination with Sr2+. Therefore, we believe that the composite scaffold has potential application prospects in the field of bone tissue engineering.

Microenvironment-responsive injectable hydrogel for neuro-vascularized bone regeneration

Bone is a richly innervated and vascularized tissue, whereas nerve-vascular network reconstruction was often ignored in biomaterial design, resulting in delayed or incomplete bone healing. Inspired by the bone injury microenvironments, here we report a controllable drug delivery strategy using a pH and reactive oxygen species (ROS) dual-response injectable hydrogel. Based on the dynamic borate ester bond covalent crosslinking, nano-hydroxyapatite (HA) and curculigoside (CCG) are integrated into PVA/TSPBA (PT) to construct a responsive injectable hydrogel (PTHC), which scavenges excessive ROS from the injury microenvironment and responsively releases HA and CCG, providing favorable homeostasis and in situ sustained release drug delivery system for bone repair. Additionally, PTHC hydrogel can alleviate ROS-mediated intracellular oxidative and exhibit multiple biological activities of angiogenesis, neurogenesis, and osteogenesis. Furthermore, it reconstructs the microvascular network, accelerates sensory nerve repair, secretes neurotransmitters and bioactive factors, and improves neuro-vascularized bone regeneration. This multi-bioactive injectable hydrogel system offers a promising advance in therapeutic materials for bone repair.

Cutting-edge collagen biocomposite reinforced with 2D nano-talc for bone tissue engineering

The advancement of nanobiocomposites reinforced with 2D nano-materials plays a pivotal role in enhancing bone tissue engineering. In this study, we introduce a nanobiocomposite that reinforces bovine collagen with 2D nano-talc, a recently exfoliated nano-mineral. These nanobiocomposites were prepared by blending collagen with varying concentrations of 2D nano-talc, encompassing mono- and few-layers talc from soapstone nanomaterial. Extensive characterization techniques including AFM, XPS, nano-FTIR, s-SNOM nanoimaging, Force Spectroscopy, and PeakForce QNM® were employed. The incorporation of 2D nano-talc significantly enhanced the mechanical properties of the nanobiocomposites, resulting in increased stiffness compared to pristine collagen. In vitro studies supported the growth and proliferation of osteoblasts onto 2D nano-talc-reinforced nanobiocomposites, as well as showed the highest mineralization potential. These findings highlight the substantial potential of the developed nanobiocomposite as a scaffold material for bone tissue engineering applications.

Conducting biointerface of spider-net-like chitosan-adorned polyurethane/SPIONs@SrO2-fMWCNTs for bone tissue engineering and antibacterial efficacy

In pursuit of enhancing bone cell proliferation, this study delves into the fabrication of porous scaffolds through the integration of nanomaterials. Specifically, we present the development of highly conductive chitosan (CS) nanonets on fibro-porous polyurethane (PU) bio-membranes. These nanofibers comprise functionalized multiwall carbon nanotubes (fMWCNTs), well-dispersed superparamagnetic iron oxide (SPIONs), and strontium oxide (SrO2) nanoparticles. The resulting porous scaffold exhibits remarkable interfacial biocompatibility, antibacterial properties, and load-bearing capability. Through meticulous in vitro investigations, the CS-PU/SPIONs/SrO2-fMWCNTs nanofibrous scaffolds have demonstrated a propensity to promote bone cell regeneration. Notably, the integration of these nanomaterials has been found to upregulate crucial bone-related markers, including ALP, ARS, COL-I, RUNX2, and SPP-I. The evaluation of these markers, conducted through quantitative real-time polymerase chain reaction (qRT-PCR) and immunocytochemistry, substantiates the improved cell survival and enhanced osteogenic differentiation facilitated by the integrated nanomaterials. This comprehensive analysis underscores the efficacy of CS-PU/SPIONs/SrO2-fMWCNTs bioscaffolds in promoting MC3T3-E1 cell regeneration within, thereby holding promise for advancements in bone tissue engineering and regenerative medicine.

An HA/PEEK scaffold with modified crystallinity via 3D-bioprinting for multiple applications in hard tissue engineering

Hard tissues, especially teeth and bones, are highly mineralized and the large-scale defect or total loss of them is irreversible. There is still no ideal strategy for the reconstruction of various hard tissue defects that can achieve the balance between biological and mechanical properties. Polyether ether ketone (PEEK) has the potential to substitute for natural hard tissue in defect areas but is limited by its biological inertness. The addition of hydroxyapatite (HA) can significantly improve the osteogenic properties and osteointegration of PEEK materials. But the mechanical properties of HA/PEEK scaffolds are far from satisfaction making scaffolds easy to fracture. We put forward a strategy to balance the mechanical and biological properties of HA/PEEK scaffolds via the regulation of the inner crystallinity and HA mixing ratio and we systematically evaluated the modified HA/PEEK scaffolds through material characterization,in vitroandin vivoexperiments. And we found that the 20%HA/PEEK scaffolds with low crystallinity achieved the required strength and elasticity, and exhibited the characteristics of promoting the proliferation, migration and osteogenic differentiation of bone marrow mesenchymal stem cells. The results of the implantation of beagles' teeth, mandible and rib showed that the 20%HA/PEEK scaffold with low crystallinity could well withstand the local complex force in the defect area and combine well with natural bone tissue, which made it a candidate for a practical versatile hard tissue engineering scaffold.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

A scoping review of graphene-based biomaterials for in vivo bone tissue engineering

The growing demand for more efficient materials for medical applications brought together two previously distinct fields: medicine and engineering. Regenerative medicine has evolved with the engineering contributions to improve materials and devices for medical use. In this regard, graphene is one of the most promising materials for bone tissue engineering and its potential for bone repair has been studied by several research groups. The aim of this study is to conduct a scoping review including articles published in the last 12 years (from 2010 to 2022) that have used graphene and its derivatives (graphene oxide and reduced graphene) in preclinical studies for bone tissue regeneration, searching in PubMed/MEDLINE, Embase, Web of Science, Cochrane Central, and clinicaltrials.gov (to confirm no study has started with clinical trial). Boolean searches were performed using the defined key words "bone" and "graphene", and manuscript abstracts were uploaded to Rayyan, a web-tool for systematic and scoping reviews. This scoping review was conducted based on Joanna Briggs Institute Manual for Scoping Reviews and the report follows the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Extension for Scoping Reviews (PRISMA-ScR) statement. After the search protocol and application of the inclusion criteria, 77 studies were selected and evaluated by five blinded researchers. Most of the selected studies used composite materials associated with graphene and its derivatives to natural and synthetic polymers, bioglass, and others. Although a variety of graphene materials were analyzed in these studies, they all concluded that graphene, its derivatives, and its composites improve bone repair processes by increasing osteoconductivity, osteoinductivity, new bone formation, and angiogenesis. Thus, this systematic review opens up new opportunities for the development of novel strategies for bone tissue engineering with graphene.

Advanced injectable hydrogels for bone tissue regeneration

Diseases or defects of the skeleton are hazardous because of their specificity and intricacy. Bone tissue engineering has become an important area of research that offers promising new tools for making biomimetic hydrogels that can be used to treat bone diseases. New hydrogels with a distinctive 3D network structure, high water content, and functional capabilities are ranked among the most promising candidates for bone tissue engineering. This makes them helpful in treating cartilage injury, skull deformity, and arthritis. This review will briefly introduce the variety of biocompatible functional hydrogels used in cell culture and bone tissue regeneration. Many gel design concepts, such as crosslinking procedures, controlled release properties, and alternative bionic methodology, were stressed regarding injectable hydrogels to form bone tissue. Hydrogels manufactured from biocompatible materials are a promising option for minimally invasive surgery because of their adaptable physicochemical qualities, ability to fill irregularly shaped defect sites, and ability to grow hormones or release drugs in response to external stimuli. Also included in this overview is a quick rundown of the more practical designs employed in treating bone disorders. Essential details on injectable hydrogel scaffolds for bone tissue regeneration are described in this article.

3D bioprinting of dECM/Gel/QCS/nHAp hybrid scaffolds laden with mesenchymal stem cell-derived exosomes to improve angiogenesis and osteogenesis

Craniofacial bone regeneration is a coupled process of angiogenesis and osteogenesis, which, associated with infection, still remains a challenge in bone defects after trauma or tumor resection. 3D tissue engineering scaffolds with multifunctional-therapeutic properties can offer many advantages for the angiogenesis and osteogenesis of infected bone defects. Hence, in the present study, a microchannel networks-enriched 3D hybrid scaffold composed of decellularized extracellular matrix (dECM), gelatin (Gel), quaterinized chitosan (QCS) and nano-hydroxyapatite (nHAp) (dGQH) was fabricated by an extrusion 3D bioprinting technology. And enlightened by the characteristics of natural bone microstructure and the demands of vascularized bone regeneration, the exosomes (Exos) isolated from human adipose derived stem cells as angiogenic and osteogenic factors were then co-loaded into the desired dGQH₂₀hybrid scaffold based on an electrostatic interaction. The results of the hybrid scaffolds performance characterization showed that these hybrid scaffolds exhibited an interconnected pore structure and appropriate degradability (>61% after 8 weeks of treatment), and the dGQH₂₀hybrid scaffold displayed the highest porosity (83.93 ± 7.38%) and mechanical properties (tensile modulus: 62.68 ± 10.29 MPa, compressive modulus: 16.22 ± 3.61 MPa) among the dGQH hybrid scaffolds. Moreover, the dGQH₂₀hybrid scaffold presented good antibacterial activities (against 94.90 ± 2.44% ofEscherichia coliand 95.41 ± 2.65% ofStaphylococcus aureus, respectively) as well as excellent hemocompatibility and biocompatibility. Furthermore, the results of applying the Exos to the dGQH₂₀hybrid scaffold showed that the Exo promoted the cell attachment and proliferation on the scaffold, and also showed a significant increase in osteogenesis and vascularity regeneration in the dGQH@Exo scaffoldsin vitroandin vivo. Overall, this novel dECM/Gel/QCS/nHAp hybrid scaffold laden with Exo has a considerable potential application in reservation of craniofacial bone defects.

Chitosan/Xanthan/Hydroxyapatite-graphene oxide porous scaffold associated with mesenchymal stem cells for dentin-pulp complex regeneration

The aim of this paper was to synthesize and characterize polymeric scaffolds of Chitosan/Xanthan/Hydroxyapatite-Graphene Oxide nanocomposite associated with mesenchymal stem cells for regenerative dentistry application. The chitosan-xanthan gum (CX) complex was associated with Hydroxyapatite-Graphene Oxide (HA-GO) nanocomposite with different Graphene Oxides (GO) concentration (0.5 wt%; 1.0 wt%; 1.5 wt%). The scaffolds characterizations were performed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and contact angle. The mechanical properties were assessed by compressive strength. The in vitro bioactivity and the in vitro cytotoxicity test (MTT test) were analyzed as well. The data was submitted to the Normality and Homogeneity tests. In vitro Indirect Cytotoxicity assay data was statistically analyzed by ANOVA two-way, followed by Tukey's test (α = 0.05). Compressive strength and contact angle data were statistically analyzed by one-way ANOVA, followed by Tukey's test (α = 0.05). XRD showed the presence of Hydroxyapatite (HA) peaks in the structures CXHA, CXHAGO 0.5%,1.0% and 1.5%. FT-IR showed amino and carboxylic bands characteristic of CX. Raman spectroscopy analysis evidenced a high quality of the GO. In the TGA it was observed the mass loss associated with the CX degradation by depolymerization. SEM analysis showed pores in the scaffolds, in addition to HA incorporated and adhered to the polymer. Contact angle test showed that scaffolds have a hydrophilic characteristic, with the CX group the highest contact angle and CXHA the lowest (p < 0.05). 1.0 wt% GO significantly increased the compressive strength compared to other compositions. In the bioactivity test, the apatite crystals precipitation on the scaffold surface was observed. MTT test showed high cell viability in CXHAGO 1.0% and CXHAGO 1.5% scaffold. CXHAGO scaffolds are promising for regenerative dentistry application because they have morphological characteristics, mechanical and biological properties favorable for the regeneration process.

Biological Effects, Applications and Design Strategies of Medical Polyurethanes Modified by Nanomaterials

Polyurethane (PU) has wide application and popularity as medical apparatus due to its unique structural properties relationship. However, there are still some problems with medical PUs, such as a lack of functionality, insufficient long-term implantation safety, undesired stability, etc. With the rapid development of nanotechnology, the nanomodification of medical PU provides new solutions to these clinical problems. The introduction of nanomaterials could optimize the biocompatibility, antibacterial effect, mechanical strength, and degradation of PUs via blending or surface modification, therefore expanding the application range of medical PUs. This review summarizes the current applications of nano-modified medical PUs in diverse fields. Furthermore, the underlying mechanisms in efficiency optimization are analyzed in terms of the enhanced biological and mechanical properties critical for medical use. We also conclude the preparation schemes and related parameters of nano-modified medical PUs, with discussions about the limitations and prospects. This review indicates the current status of nano-modified medical PUs and contributes to inspiring novel and appropriate designing of PUs for desired clinical requirements.

Cytocompatibility of MG-63 osteosarcoma cells on chitosan/hydroxyapatite/lignin hybrid composite scaffoldin vitro

This study aims at fabricating promising cytocompatible hybrid biocomposite scaffolds from chitosan (CS), hydroxyapatite (HAP) and lignin (L) for bone tissue engineering by using freeze-drying technique. Different ratios of HAP to L (50:0, 37.5:12.5, 25:25 and 12.5:37.5) were taken to determine the optimum ratio for obtaining a composite with superior properties. The mechanical and biological properties of the resulting composites were investigated. The mechanical results showed that the prepared composite with a ratio of 25:25 of HAP/L exhibited a remarkable enhancement in the mechanical properties compared to the others. Additionally, it was found from thein vitroresults that the addition of L enhanced the water uptake value of the resulting scaffolds indicating their increased hydrophilicity. As a result, a significant increase in the attachment and proliferation of MG-63 cell line (osteoblast like cells) was observed in composite scaffolds with L over the scaffold without L (CS/HAP). From these results, it could be suggested that the prepared composite scaffold with 25:25 of HAP/L is very promising biomaterials in bone tissue-engineering as it exhibited a better mechanical and biological properties than the other prepared composites.

Graphene oxide reinforced SrHAP composite as a drug carrier in bone regeneration

Strontium substituted HAP (SrHAP), with a 10 mol% substitution, was mineralized on increasing weight percentages of graphene oxide (2, 4 and 6). The GS composites were comprehensively characterized for drug delivery in bone reconstruction. The formation of SrHAP was verified by XRD and FT-IR results. The apatite crystallization was influenced by graphene oxide content and strontium. The EDS results confirmed the presence of strontium and HR-SEM depicted rod shape apatite, of length between 58 and 135 nm, uniformly embedded on graphene oxide. The reinforcement of graphene oxide increased the surface area, porosity, microhardness (upto 0.59 GPa), protein adsorption (upto 18.16 μg/mg), water uptake and degradation properties. Also, the increase in graphene oxide fraction significantly enhanced the curcumin encapsulation efficiency (upto 80.16%) and the drug release was considerably retarded over SrHAP. The in vitro studies using human osteoblast-like MG-63 cells demonstrated that curcumin-loaded composite was biocompatible and promoted proliferation, differentiation and matrix mineralization. The results highlight the combinational therapy of osteogenic ion (strontium) and osteogenic drug (curcumin) as a promising platform in bone tissue engineering.

Effect of chitosan/inorganic nanomaterial scaffolds on bone regeneration and related influencing factors in animal models: A systematic review

Bone tissue engineering (BTE) provides a promising alternative for transplanting. Due to biocompatibility and biodegradability, chitosan-based scaffolds have been extensively studied. In recent years, many inorganic nanomaterials have been utilized to modify the performance of chitosan-based materials. In order to ascertain the impact of chitosan/inorganic nanomaterial scaffolds on bone regeneration and related key factors, this study presents a systematic comparison of various scaffolds in the calvarial critical-sized defect (CSD) model. A total of four electronic databases were searched without publication date or language restrictions up to April 2022. The Animal Research Reporting of In Vivo Experiments 2.0 guidelines (ARRIVE 2.0) were used to assess the quality of the included studies. Moreover, the risk of bias (RoB) was evaluated via the Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) tool. After the screening, 22 studies were selected. None of these studies achieved high quality or had a low RoB. In the available studies, scaffolds reconstructed bone defects in radically different extensions. Several significant factors were identified, including baseline characteristics, physicochemical properties of scaffolds, surgery details, and scanning or reconstruction parameters of micro-computed tomography (micro-CT). Further studies should focus on not only improving the osteogenic performance of the scaffolds but also increasing the credibility of studies through rigorous experimental design and normative reports.

Comparative review of piezoelectric biomaterials approach for bone tissue engineering

Bone as a minerals' reservoir and rigid tissue of the body generating red and white blood cells supports various organs. Although the self-regeneration property of bone, it cannot regenerate spontaneously in severe damages and still remains as a challenging issue. Tissue engineering offers several techniques for regenerating damaged bones, where various biomaterials are examined to fabricate scaffolds for bone repair. Piezoelectric characteristic plays a crucial role in repairing and regenerating damaged bone by mimicking the bone niche behavior. Piezoelectric biomaterials show significant potential for bone tissue engineering. Herein we try to have a comparative review on piezoelectric and non-piezoelectric biomaterials used in bone tissue engineering, classified them, and discussed their effects on implanted cells and manufacturing techniques. Especially, Polyvinylidene fluoride (PVDF) and its composites are the most practically used piezoelectric biomaterials for bone regeneration. PVDF and its composites have been summarized and discussed to repair damaged bone tissues.

Recent advances and challenges in graphene-based nanocomposite scaffolds for tissue engineering application

Graphene-based nanocomposites have recently attracted increasing attention in tissue engineering because of their extraordinary features. These biocompatible substances, in the presence of an apt microenvironment, can stimulate and sustain the growth and differentiation of stem cells into different lineages. This review discusses the characteristics of graphene and its derivatives, such as their excellent electrical signal transduction, carrier mobility, outstanding mechanical strength with improving surface characteristics, self-lubrication, antiwear properties, enormous specific surface area, and ease of functional group modification. Moreover, safety issues in the application of graphene and its derivatives in terms of biocompatibility, toxicity, and interaction with immune cells are discussed. We also describe the applicability of graphene-based nanocomposites in tissue healing and organ regeneration, particularly in the bone, cartilage, teeth, neurons, heart, skeletal muscle, and skin. The impacts of special textural and structural characteristics of graphene-based nanomaterials on the regeneration of various tissues are highlighted. Finally, the present review gives some hints on future research for the transformation of these exciting materials in clinical studies.

Surface-Decorated Graphene Oxide Sheets with Copper Nanoderivatives for Bone Regeneration: An In Vitro and In Vivo Study Regarding Molecular Mechanisms, Osteogenesis, and Anti-infection Potential

It has been previously reported that graphene oxide/copper nanoderivative (GO/Cu)-incorporated chitosan/hyaluronic acid scaffolds might be promising wound dressings for the management of infected wound healing. The aim of the present research is to deeply explore the potential antimicrobial mechanisms and synergistic osteogenic activity, as well as the in vivo anti-infective behavior of GO/Cu nanocomposites, making them possible candidates for establishing implantable biomaterials for the repair of infected bone defects. The antibacterial mechanisms of the nanocomposites were explored through the examination of membrane integrity, oxidative stress, and metabolic enzyme activities. Then, the cytocompatibility with bone mesenchymal stem cells (rBMSCs) and osteogenic potential were confirmed, and a subcutaneous bacterial infection model in rats was also established to verify the in vivo anti-infective property and biosafety of the nanocomposites. It was found that leakage of adenosine triphosphate, proteins, and reducing sugars from the bacterial cells, indicative of damaged permeability of bacterial membranes, and promoted production of reactive oxygen species and disordered metabolic enzyme activities in response to oxidative stress were possible molecular mechanisms responsible for the synergistic antibacterial effects of the GO/Cu nanocomposites. Additionally, good cytocompatibility with rBMSCs and promoted osteogenic differentiation were found in GO/Cu nanocomposites (mass ratio = 2:1), which also demonstrated satisfactory in vivo anti-infective performance, reduced inflammation, and acceptable biosafety. Based on our results, damaged bacterial membranes, increased ROS production, and disorders of crucial enzyme metabolism were the main antibacterial mechanisms involved in the bacterium-killing events caused by the GO/Cu nanocomposites, which also showed enhanced osteogenic activity, in vivo anti-infective capability, and acceptable cytocompatibility and biosafety. Therefore, GO/Cu (2:1) nanocomposites are a potential strategy for improving the biological performance of current bone substitutes used for combating bacterial-contaminated bone defects.

Preparation of multigradient hydroxyapatite scaffolds and evaluation of their osteoinduction properties

Porous hydroxyapatite (HA) scaffolds are often used as bone repair materials, owing to their good biocompatibility, osteoconductivity and low cost. Vascularization and osteoinductivity of porous HA scaffolds were limited in clinical application, and these disadvantages were need to be improved urgently. We used water-in-oil gelation and pore former methods to prepare HA spheres and a porous cylindrical HA container, respectively. The prepared HA spheres were filled in container to assemble into composite scaffold. By adjusting the solid content of the slurry (solid mixture of chitin sol and HA powder) and the sintering temperature, the porosity and crystallinity of the HA spheres could be significantly improved; and mineralization of the HA spheres significantly improved the biological activity of the composite scaffold. The multigradient (porosity, crystallinity and mineralization) scaffold (HA-700) filled with the mineralized HA spheres exhibited a lower compressive strength; however, in vivo results showed that their vascularization ability were higher than those of other groups, and their osteogenic Gini index (Go: an index of bone mass, and inversely proportional to bone mass) showed a continuous decrease with the implantation time. This study provides a new method to improve porous HA scaffolds and meet the demands of bone tissue engineering applications.

One-Step Synthesis of Multifunctional Chitosan Hydrogel for Full-Thickness Wound Closure and Healing

Multifunctional hydrogel as a sealant or wound dressing with high adhesiveness and excellent antibacterial activity is highly desirable in clinical applications. In this contribution, one-step synthetic hydrogel based on quaternized chitosan (QCS), tannic acid (TA), and ferric iron (Fe(III)) is developed for skin incision closure and Staphylococcus aureus (S. aureus)-infected wound healing. In this hydrogel system, the ionic bonds and hydrogen bonds between QCS and TA form the main backbone of hydrogel, the metal coordination bonds between TA and Fe(III) (catechol-Fe) endow hydrogel with excellent adhesiveness and (near-infrared light) NIR-responsive photothermal property, and these multiple dynamic physical crosslinks enable QCS/TA/Fe hydrogel with flexible self-healing ability and injectability. Moreover, QCS/TA/Fe hydrogel possesses superior antioxidant, anti-inflammatory, hemostasis, and biocompatibility. Also, it is safe for vital organs. The data from the mouse skin incision model and infected full-thickness skin wound model presented the high wound closure effectiveness and acceleration of the wound healing process by this multifunctional hydrogel, highlighting its great potential in wound management.

Biomedical applications of chitosan-graphene oxide nanocomposites

Chitosan (CS) and graphene oxide (GO) nanocomposites have received wide attention in biomedical fields due to the synergistic effect between CS which has excellent biological characteristics and GO which owns great physicochemical, mechanical, and optical properties. Nanocomposites based on CS and GO can be fabricated into a variety of forms, such as nanoparticles, hydrogels, scaffolds, films, and nanofibers. Thanks to the ease of functionalization, the performance of these nanocomposites in different forms can be further improved by introducing other functional polymers, nanoparticles, or growth factors. With this background, the current review summarizes the latest developments of CS-GO nanocomposites in different forms and compositions in biomedical applications including drug and biomacromolecules delivery, wound healing, bone tissue engineering, and biosensors. Future improving directions and challenges for clinical practice are proposed as well.

Advances in Use of Nanomaterials for Musculoskeletal Regeneration

Since the worldwide incidence of bone disorders and cartilage damage has been increasing and traditional therapy has reached its limits, nanomaterials can provide a new strategy in the regeneration of bones and cartilage. The nanoscale modifies the properties of materials, and many of the recently prepared nanocomposites can be used in tissue engineering as scaffolds for the development of biomimetic materials involved in the repair and healing of damaged tissues and organs. In addition, some nanomaterials represent a noteworthy alternative for treatment and alleviating inflammation or infections caused by microbial pathogens. On the other hand, some nanomaterials induce inflammation processes, especially by the generation of reactive oxygen species. Therefore, it is necessary to know and understand their effects in living systems and use surface modifications to prevent these negative effects. This contribution is focused on nanostructured scaffolds, providing a closer structural support approximation to native tissue architecture for cells and regulating cell proliferation, differentiation, and migration, which results in cartilage and bone healing and regeneration.

Impact of High-Altitude Hypoxia on Early Osseointegration With Bioactive Titanium

Nowadays, the bone osseointegration in different environments is comparable, but the mechanism is unclear. This study aimed to investigate the osseointegration of different bioactive titanium surfaces under normoxic or high-altitude hypoxic environments. Titanium implants were subjected to one of two surface treatments: (1) sanding, blasting, and acid etching to obtain a rough surface, or (2) extensive polishing to obtain a smooth surface. Changes in the morphology, proliferation, and protein expression of osteoblasts on the rough and smooth surfaces were examined, and bone formation was studied through western blotting and animal-based experiments. Our findings found that a hypoxic environment and rough titanium implant surface promoted the osteogenic differentiation of osteoblasts and activated the JAK1/STAT1/HIF-1α pathway in vitro. The animal study revealed that following implant insertion in tibia of rabbit, bone repair at high altitudes was slower than that at low altitudes (i.e., in plains) after 2weeks; however, bone formation did not differ significantly after 4weeks. The results of our study showed that: (1) The altitude hypoxia environment would affect the early osseointegration of titanium implants while titanium implants with rough surfaces can mitigate the effects of this hypoxic environment on osseointegration, (2) the mechanism may be related to the activation of JAK1/STAT1/HIF-1α pathway, and (3) our results suggest the osteogenesis of titanium implants, such as oral implants, is closely related to the oxygen environment. Clinical doctors, especially dentists, should pay attention to the influence of hypoxia on early osseointegration in patients with high altitude. For example, it is better to choose an implant system with rough implant surface in the oral cavity of patients with tooth loss at high altitude.

Fabrication and applications of bioactive chitosan-based organic-inorganic hybrid materials: A review

Organic-inorganic hybrid materials like bone, shells, and teeth can be found in nature, which are usually composed of biomacromolecules and nanoscale inorganic ingredients. Synergy of organic-inorganic components in hybrid materials render them outstanding and versatile performance. Chitosan is commonly used organic materials in bionic hybrid materials since its bioactive properties and could be controllable tailored by various means to meet complex conditions in different applications. Among these fabrication means, hybridization was favored for its convenience and efficiency. This review discusses three kinds of chitosan-based hybrid materials: hybridized with hydroxyapatite, calcium carbonate, and clay respectively, which are the representative of phosphate, carbonate, and hydrous aluminosilicates. Here, we reported the latest developments of the preparation methods, composition, structure and applications of these bioactive hybrid materials, especially in the biomedical field. Despite the great progress was made in bioactive organic-inorganic hybrid materials based on chitosan, some challenges and specific directions are still proposed for future development in this review.

Oxygen Plasma Technology-Assisted Preparation of Three-Dimensional Reduced Graphene Oxide/Polypyrrole/Strontium Composite Scaffold for Repair of Bone Defects Caused by Osteoporosis

Repairs of bone defects caused by osteoporosis have always relied on bone tissue engineering. However, the preparation of composite tissue engineering scaffolds with a three-dimensional (3D) macroporous structure poses huge challenges in achieving osteoconduction and osteoinduction for repairing bone defects caused by osteoporosis. In the current study, a three-dimensional macroporous (150-300 μm) reduced graphene oxide/polypyrrole composite scaffold modified by strontium (Sr) (3D rGO/PPY/Sr) was successfully prepared using the oxygen plasma technology-assisted method, which is simple, safe, and inexpensive. The findings of the MTT assay and AO/EB fluorescence double staining showed that 3D rGO/PPY/Sr has a good biocompatibility and effectively promoted MC3T3-E1 cell proliferation. Furthermore, the ALP assay and alizarin red staining showed that 3D rGO/PPY/Sr increased the expression levels of ALP activity and the formation of calcified nodules. The desirable biocompatibility, osteoconduction, and osteoinduction abilities, assure that the 3D macroporous rGO/PPY/Sr composite scaffold offers promising potential for use in the repair of bone defects caused by osteoporosis in bone tissue engineering.

Bi-directional regulation functions of lanthanum-substituted layered double hydroxide nanohybrid scaffolds via activating osteogenesis and inhibiting osteoclastogenesis for osteoporotic bone regeneration

Rationale: Osteoporotic patients suffer symptoms of excessive osteoclastogenesis and impaired osteogenesis, resulting in a great challenge to treat osteoporosis-related bone defects. Based on the positive effect of rare earth elements on bone metabolism and bone regeneration, we try to prove the hypothesis that the La³⁺ dopants in lanthanum-substituted MgAl layered double hydroxide (La-LDH) nanohybrid scaffolds simultaneously activate osteogenesis and inhibit osteoclastogenesis.

Methods: A freeze-drying technology was employed to construct La-LDH nanohybrid scaffolds. The in vitro osteogenic and anti-osteoclastogenic activities of La-LDH nanohybrid scaffolds were evaluated by using ovariectomized rat bone marrow stromal cells (rBMSCs-OVX) and bone marrow-derived macrophages (BMMs) as cell models. The in vivo bone regeneration ability of the scaffolds was investigated by using critical-size calvarial bone defect model of OVX rats.

Results: La-LDH nanohybrid scaffolds exhibited three-dimensional macroporous structure, and La-LDH nanoplates arranged perpendicularly on chitosan organic matrix. The La³⁺ dopants in the scaffolds promote proliferation and osteogenic differentiation of rBMSCs-OVX by activating Wnt/β-catenin pathway, leading to high expression of ALP, Runx-2, COL-1 and OCN genes. Moreover, La-LDH scaffolds significantly suppressed RANKL-induced osteoclastogenesis by inhibiting NF-κB signaling pathway. As compared with the scaffolds without La³⁺ dopants, La-LDH scaffolds provided more favourable microenvironment to induce new bone in-growth along macroporous channels.

Conclusion: La-LDH nanohybrid scaffolds possessed the bi-directional regulation functions on osteogenesis and osteoclastogenesis for osteoporotic bone regeneration. The modification of La³⁺ dopants in bone scaffolds provides a novel strategy for osteoporosis-related bone defect healing.

Improved nanomechanical and in-vitro biocompatibility of graphene oxide-carbon nanotube hydroxyapatite hybrid composites by synergistic effect

Hydroxyapatite (HAP) is an attractive bio-material for new bone growth process, hard tissue repair, bioactivity, osteoblast adhesion and proliferation due to its physicochemical resembles natural apatite. The intrinsic brittleness and poor mechanical properties of HAP restrict it for potential clinical applications. This problem is undertaken by exploiting the unique properties of carbon nanofillers (carbon nanotube (CNTs), graphene oxide (GO), graphene oxide-carbon nanotube (GCNTs) hybrid) which are used as reinforcement for preparing the carbon nanofillers based HAP composites. The nanomechanical and in-vitro biocompatibility of carbon nanofiller reinforced HAP composites have been studied. Carbon nanofiller reinforced HAP composites led to an improvement in nanomechanical and biocompatibility properties. The nanoindentation hardness and elastic modulus of GCNTs-HAP composites are significantly higher than other carbon nanofiller reinforced composites and pristine HAP powder. The in-vitro cytotoxicity of the prepared carbon nanofillers reinforced HAP composites is examined using MTT-assay on the MDCK cell line. The prepared GCNTs-HAP composites containing 2% of GCNTs nanofiller show higher cell viability, improved compatibility, and superior one cell proliferation induction than the other carbon nanofillers and HAP. These findings will provide the new prospects for utilizing the GO and its hybrid in HAP composites in bone repair, regeneration, augmentation and implantation.