Amorphous Silica: A New Antioxidant Role for Rapid Critical-Sized Bone Defect Healing

Novel Hydrogel Adjuvant of Chinese Medicine External Preparations for Accelerated Healing of Deep Soft Tissue Injuries

Traditional Chinese medicine external prescriptions have displayed excellent clinical effects for treating deep soft tissue injuries. However, the effects cannot be fully utilized due to the limitations of their dosage forms and usage methods. It is still a challenge to develop a satisfactory adjuvant of traditional Chinese medicine external prescriptions. Herein, a hydrogel adjuvant was prepared based on gallic acid coupled ε-poly-l-lysine and partially oxidized hyaluronic acid. The resulting adjuvant shows great physicochemical properties, low hemolysis rate (still much less than 5% at 5 mg/mL), excellent antibacterial ability (about 95% at 2 mg/mL), strong antioxidant ability (1.687 ± 0.085 mmol FeSO4/(g hydrogel) at 1 mg/mL), as well as outstanding biocompatibility. A clinically used Chinese medicine external preparation was selected as an example to investigate the effectiveness of the adjuvant in treating deep soft tissue injuries. The results show that the prescription can be evenly dispersed in the adjuvant. Moreover, the introduction of the prescription has not significantly changed these advanced properties of the adjuvant. Importantly, the hydrogel adjuvant significantly improves the effectiveness of the prescription in treating deep soft tissue injuries. This work offers an alternative approach to the development of a new-type adjuvant of Chinese medicine external preparations and also provides a new strategy for the combination of traditional Chinese medicine and hydrogel to treat clinical diseases.

Local Application of Tanshinone IIA protects mesenchymal stem cells from apoptosis and promotes fracture healing in ovariectomized mice

BACKGROUND

Elderly patients suffering from osteoporotic fractures are more susceptible to delayed union or nonunion, and their bodies then are in a state of low-grade chronic inflammation with decreased antioxidant capacity. Tanshinone IIA is widely used in treating cardiovascular and cerebrovascular diseases in China and has anti-inflammatory and antioxidant effects. We aimed to observe the antioxidant effects of Tanshinone IIA on mesenchymal stem cells (MSCs), which play important roles in bone repair, and the effects of local application of Tanshinone IIA using an injectable biodegradable hydrogel on osteoporotic fracture healing.

METHODS

MSCs were pretreated with or without different concentrations of Tanshinone IIA followed by H2O2 treatment. Ovariectomized (OVX) C57BL/6 mice received a mid-shaft transverse osteotomy fracture on the left tibia, and Tanshinone IIA was applied to the fracture site using an injectable hydrogel.

RESULTS

Tanshinone IIA pretreatment promoted the expression of nuclear factor erythroid 2-related factor 2 and antioxidant enzymes, and inhibited H2O2-induced reactive oxygen species accumulation in MSCs. Furthermore, Tanshinone IIA reversed H2O2-induced apoptosis and decrease in osteogenic differentiation in MSCs. After 4 weeks of treatment with Tanshinone IIA in OVX mice, the bone mineral density of the callus was significantly increased and the biomechanical properties of the healed tibias were improved. Cell apoptosis was decreased and Nrf2 expression was increased in the early stage of callus formation.

CONCLUSIONS

Taken together, these results indicate that Tanshinone IIA can activate antioxidant enzymes to protect MSCs from H2O2-induced cell apoptosis and osteogenic differentiation inhibition. Local application of Tanshinone IIA accelerates fracture healing in ovariectomized mice.

3D Printing of Cobalt-Incorporated Chloroapatite Bioceramic Composite Scaffolds with Antioxidative Activity for Enhanced Osteochondral Regeneration

Osteochondral defects are often accompanied by excessive reactive oxygen species (ROS) caused by osteoarthritis or acute surgical inflammation. An inflammatory environment containing excess ROS will not only hinder tissue regeneration but also impact the quality of newly formed tissues. Therefore, there is an urgent need to develop scaffolds with both ROS scavenging and osteochondral repair functions to promote and protect osteochondral tissue regeneration. In this work, by using 3D printing technology, a composite scaffold based on cobalt-incorporated chloroapatite (Co-ClAP) bioceramics, which possesses ROS-scavenging activity and can support cell proliferation, adhesion, and differentiation, is developed. Benefiting from the catalytic activity of Co-ClAP bioceramics, the composite scaffold can protect cells from oxidative damage under ROS-excessive conditions, support their directional differentiation, and simultaneously mediate an anti-inflammatory microenvironment. In addition, it is also confirmed by using rabbit osteochondral defect model that the Co-ClAP/poly(lactic-co-glycolic acid) scaffold can effectively promote the integrated regeneration of cartilage and subchondral bone, exhibiting an ideal repair effect in vivo. This study provides a promising strategy for the treatment of defects with excess ROS and inflammatory microenvironments.

SiONx Coating Regulates Mesenchymal Stem Cell Antioxidant Capacity via Nuclear Erythroid Factor 2 Activity under Toxic Oxidative Stress Conditions

Healing in compromised and complicated bone defects is often prolonged and delayed due to the lack of bioactivity of the fixation device, secondary infections, and associated oxidative stress. Here, we propose amorphous silicon oxynitride (SiONx) as a coating for the fixation devices to improve both bioactivity and bacteriostatic activity and reduce oxidative stress. We aimed to study the effect of increasing the N/O ratio in the SiONx to fine-tune the cellular activity and the antioxidant effect via the NRF2 pathway under oxidative stress conditions. The in vitro studies involved using human mesenchymal stem cells (MSCs) to examine the effect of SiONx coatings on osteogenesis with and without toxic oxidative stress. Additionally, bacterial growth on SiONx surfaces was studied using methicillin-resistant Staphylococcus aureus (MRSA) colonies. NRF2 siRNA transfection was performed on the hMSCs (NRF2-KD) to study the antioxidant response to silicon ions. The SiONx implant surfaces showed a >4-fold decrease in bacterial growth vs. bare titanium as a control. Increasing the N/O ratio in the SiONx implants increased the alkaline phosphatase activity >1.5 times, and the other osteogenic markers (osteocalcin, RUNX2, and Osterix) were increased >2-fold under normal conditions. Increasing the N/O ratio in SiONx enhanced the protective effects and improved cell viability against toxic oxidative stress conditions. There was a significant increase in osteocalcin activity compared to the uncoated group, along with increased antioxidant activity under oxidative stress conditions. In NRF2-KD cells, there was a stunted effect on the upregulation of antioxidant markers by silicon ions, indicating a role for NRF2. In conclusion, the SiONx coatings studied here displayed bacteriostatic properties. These materials promoted osteogenic markers under toxic oxidative stress conditions while also enhancing antioxidant NRF2 activity. These results indicate the potential of SiONx coatings to induce in vivo bone regeneration in a challenging oxidative stress environment.

Reactive Simulations of Silica Functionalization with Aromatic Hydrocarbons

Reactive molecular dynamics simulations are used to model the covalent functionalization of amorphous silica with aromatic hydrocarbons. Simulations show that the surface density of silanol-terminated phenyl, naphthyl, and anthracenyl molecules is lower than the maximum value calculated based on molecule geometry, and the simulation densities decrease faster with the number of aromatic rings than the geometric densities. The trends are analyzed in terms of the surface-silanol bonding configurations, tilt angles, local conformational ordering, and aggregation of surface-bound molecules under steady-state conditions. Results show that the surface density is affected by both the size and symmetry of the aromatic hydrocarbons. The correlations among bonding, orientation, and surface density identified here may guide the selection or design of molecules for functionalized surfaces.

The Preparation and Effects of Organic-Inorganic Antioxidative Biomaterials for Bone Repair

Reactive oxygen species (ROS) has great influence in many physiological or pathological processes in organisms. In the site of bone defects, the overproduced ROS significantly affects the dynamic balance process of bone regeneration. Many antioxidative organic and inorganic antioxidants showed good osteogenic ability, which has been widely used for bone repair. It is of great significance to summarize the antioxidative bone repair materials (ABRMs) to provide guidance for the future design and preparation of osteogenic materials with antioxidative function. Here, this review introduced the major research direction of ABRM at present in nanoscale, 2-dimensional coating, and 3-dimensional scaffolds. Moreover, the referring main active substances and antioxidative properties were classified, and the positive roles of antioxidative materials for bone repair have also been clearly summarized in signaling pathways, antioxidant enzymes, cellular responses and animal levels.

Revolutionizing bone regeneration: advanced biomaterials for healing compromised bone defects

In this review, we explore the application of novel biomaterial-based therapies specifically targeted towards craniofacial bone defects. The repair and regeneration of critical sized bone defects in the craniofacial region requires the use of bioactive materials to stabilize and expedite the healing process. However, the existing clinical approaches face challenges in effectively treating complex craniofacial bone defects, including issues such as oxidative stress, inflammation, and soft tissue loss. Given that a significant portion of individuals affected by traumatic bone defects in the craniofacial area belong to the aging population, there is an urgent need for innovative biomaterials to address the declining rate of new bone formation associated with age-related changes in the skeletal system. This article emphasizes the importance of semiconductor industry-derived materials as a potential solution to combat oxidative stress and address the challenges associated with aging bone. Furthermore, we discuss various material and autologous treatment approaches, as well as in vitro and in vivo models used to investigate new therapeutic strategies in the context of craniofacial bone repair. By focusing on these aspects, we aim to shed light on the potential of advanced biomaterials to overcome the limitations of current treatments and pave the way for more effective and efficient therapeutic interventions for craniofacial bone defects.

Engineering Antioxidant Surfaces for Titanium-Based Metallic Biomaterials

Prolonged inflammation induced by orthopedic metallic implants can critically affect the success rates, which can even lead to aseptic loosening and consequent implant failure. In the case of adverse clinical conditions involving osteoporosis, orthopedic trauma and implant corrosion-wear in peri-implant region, the reactive oxygen species (ROS) activity is enhanced which leads to increased oxidative stress. Metallic implant materials (such as titanium and its alloys) can induce increased amount of ROS, thereby critically influencing the healing process. This will consequently affect the bone remodeling process and increase healing time. The current review explores the ROS generation aspects associated with Ti-based metallic biomaterials and the various surface modification strategies developed specifically to improve antioxidant aspects of Ti surfaces. The initial part of this review explores the ROS generation associated with Ti implant materials and the associated ROS metabolism resulting in the formation of superoxide anion, hydroxyl radical and hydrogen peroxide radicals. This is followed by a comprehensive overview of various organic and inorganic coatings/materials for effective antioxidant surfaces and outlook in this research direction. Overall, this review highlights the critical need to consider the aspects of ROS generation as well as oxidative stress while designing an implant material and its effective surface engineering.

Enhanced osteogenesis on proantocyanidin-loaded date palm endocarp cellulosic matrices: A novel sustainable approach for guided bone regeneration

Developing inexpensive, biocompatible natural scaffolds that can support the differentiation and proliferation of stem cells has been recently emphasized by the research community to faster obtain the FDA approvals for regenerative medicine. In this regard, plant-derived cellulose materials are a novel class of sustainable scaffolding materials with high potentials for bone tissue engineering (BTE). However, low bioactivity of the plant-derived cellulose scaffolds restricts cell proliferation and cell differentiation. This limitation can be addressed though surface-functionalization of cellulose scaffolds with natural antioxidant polyphenols, e.g., grape seed proanthocyanidin (PCA)-rich extract (GSPE). Despite the various merits of GSPE as a natural antioxidant, its impact on the proliferation and adhesion of osteoblast precursor cells, and on their osteogenic differentiation is an as-yet unknown issue. Here, we investigated the effects of GSPE surface functionalization on the physicochemical properties of decellularized date (Phoenix dactyliferous) fruit inner layer (endocarp) (DE) scaffold. In this regard, various physiochemical characteristics of the DE-GSPE scaffold such as hydrophilicity, surface roughness, mechanical stiffness, porosity, and swelling, and biodegradation behavior were compared with those of the DE scaffold. Additionally, the impact of the GSPE treatment of the DE scaffold on the osteogenic response of human mesenchymal stem cells (hMSCs) was thoroughly studied. For this purpose, cellular activities including cell adhesion, calcium deposition and mineralization, alkaline phosphatase (ALP) activity, and expression levels of bone-related genes were monitored. Taken together, the GSPE treatment enhanced the physicochemical and biological properties of the DE-GSPE scaffold, thereby raising its potentials as a promising candidate for guided bone regeneration.

Current Techniques of Water Solubility Improvement for Antioxidant Compounds and Their Correlation with Its Activity: Molecular Pharmaceutics

The aqueous solubility of a drug is important in the oral formulation because the drug can be absorbed from intestinal sites after being dissolved in the gastrointestinal fluid, leading to its bioavailability. Almost 80% of active pharmaceutical ingredients are poorly water-soluble, including antioxidant compounds. This makes antioxidant activity inefficient in preventing disease, particularly for orally administered formulations. Although several investigations have been carried out to improve the solubility of antioxidant compounds, there is still limited research fully discussing the subject. Therefore, this study aimed to provide an overview and discussion of the issues related to the methods that have been used to improve the solubility and activity of antioxidant compounds. Articles were found using the keywords "antioxidant" and "water solubility improvement" in the Scopus, PubMed, and Google Scholar databases. The selected articles were published within the last five years to ensure all information was up-to-date with the same objectives. The most popular methods of the strategies employed were solid dispersion, co-amorphous, and nanoparticle drug delivery systems, which were used to enhance the solubility of antioxidant compounds. These investigations produced impressive results, with a detailed discussion of the mechanism of improvement in the solubility and antioxidant activity of the compounds developed. This review shows that the strategies used to increase the solubility of antioxidant compounds successfully improved their antioxidant activity with enhanced free radical scavenging abilities.

Multiscale design of stiffening and ROS scavenging hydrogels for the augmentation of mandibular bone regeneration

Although biomimetic hydrogels play an essential role in guiding bone remodeling, reconstructing large bone defects is still a significant challenge since bioinspired gels often lack osteoconductive capacity, robust mechanical properties and suitable antioxidant ability for bone regeneration. To address these challenges, we first engineered molecular design of hydrogels (gelatin/polyethylene glycol diacrylate/2-(dimethylamino)ethyl methacrylate, GPEGD), where their mechanical properties were significantly enhanced via introducing trace amounts of additives (0.5 wt%). The novel hybrid hydrogels show high compressive strength (>700 kPa), stiff modulus (>170 kPa) and strong ROS-scavenging ability. Furthermore, to endow the GPEGD hydrogels excellent osteoinductions, novel biocompatible, antioxidant and BMP-2 loaded polydopamine/heparin nanoparticles (BPDAH) were developed for functionalization of the GPEGD gels (BPDAH-GPEGD). In vitro results indicate that the antioxidant BPDAH-GPEGD is able to deplete elevated ROS levels to protect cells viability against ROS damage. More importantly, the BPDAH-GPEGD hydrogels have good biocompatibility and promote the osteo differentiation of preosteoblasts and bone regenerations. At 4 and 8 weeks after implantation of the hydrogels in a mandibular bone defect, Micro-computed tomography and histology results show greater bone volume and enhancements in the quality and rate of bone regeneration in the BPDAH-GPEGD hydrogels. Thus, the multiscale design of stiffening and ROS scavenging hydrogels could serve as a promising material for bone regeneration applications.

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Trace additives of DMAEMA markedly enhanced the mechanical performances of the gelatin-based hydrogels through molecular induced multiple crosslinking structures.

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Molecular design strategy combined with bioactive nanocomposites have a synergistically effects on promoting ROS scavenging ability and osteoactivity of the biomimetic hydrogels.

Accelerated Bone Regeneration by an Astaxanthin-Modified Antioxidant Aerogel through Relieving Oxidative Stress via the NRF2 Signaling Pathway

Bone regeneration of critical-sized bone defects (CSBDs) with biomimetic collagen-based aerogels remains a significant challenge due to the oxidative stress on the microenvironment. The excessive oxidative stress could induce apoptosis and dysfunction of host-derived cells. Astaxanthin (ATX) exhibits excellent antioxidant ability to block free radical chain reactions. In the present study, hybrid antioxidant collagen-derived aerogels (ATX-Col aerogels) were fabricated by a simple one-step method through the covalent cross-linking of Col and ATX. The resulting ATX-Col aerogels show porous and interconnected structures due to freeze-drying strategies. The ATX-Col aerogels exhibited excellent biocompatibility and biosafety. Furthermore, ATX-Col aerogels demonstrated favorable antioxidant capacity by eliminating intracellular ROS by activating the NRF2 signaling pathway. Finally, excellent reparative effects in repairing rat cranial defects were observed in ATX-Col aerogels. Taken together, ATX-Col aerogels can accelerate bone regeneration by relieving oxidative stress via the NRF2 signaling pathway and act as a potential bone graft for CSBD. This study provides a simple method of developing antioxidant aerogels for bone regeneration.

Superoxide Dismutase and Glutathione Reductase as Indicators of Oxidative Stress Levels May Relate to Geriatric Hip Fractures' Survival and Walking Ability: A Propensity Score Matching Study

Background

Oxidative stress status may affect bone metabolism and regeneration. However, few studies reported whether oxidative stress could impact the outcomes of hip fractures. This study aimed to explore if superoxide dismutase and glutathione reductase, the critical antioxidant enzymes, correlated with the prognosis of hip fractures.

Methods

Patients with hip fractures were extracted from our database, and those who met the inclusion criteria were analyzed. Propensity score matching was used to reduce the influence of confounding factors, and ROC curves based on matched populations were created to determine the optimal cutoff points of SOD and GR. Then, outcomes between SOD or GR and outcomes of hip fractures were compared.

Results

Out of 301 patients enrolled in this study, 50 patients died within one year. After a 1:1 PSM, the patients with less than 1-year survival had significantly lower SOD (p = 0.026) and GR (p = 0.021) than those who were still alive at one year. Logistics analysis showed that low SOD and low GR may be independent risk factors for 6-month survival, 1-year survival, 6-month free walking ability, and 1-year free walking ability.

Conclusion

SOD and GR may be the independent risk factors for survival and walking abilities of hip fractures.

PgC3Mg metal-organic cages functionalized hydrogels with enhanced bioactive and ROS scavenging capabilities for accelerated bone regeneration

The repair of large bone defects is an urgent problem in the clinic. Note that the disruption of redox homeostasis around bone defect sites might hinder the new bone reconstruction. The rational design of hydrogels for bone regeneration still faces the challenges of insufficient antioxidant capability and weak osteogenesis performance. Here, motivated by the versatile therapeutic functions of metal-organic cages, magnesium-seamed C-propylpyrogallol[4]arene (PgC₃Mg) functionalized biodegradable and porous gelatin methacrylate (GelMA) hydrogels are constructed. The novel metal-organic cages endow hydrogels with highly bioactive characteristics and strong reactive oxygen species (ROS)-scavenging ability owing to the simultaneous release of bioactive Mg²⁺ ions and antioxidant phenolic hydroxyl-rich moieties. The in vitro results reveal that the PgC₃Mg modified biocompatible hydrogels show higher expression of osteo-related genes and significantly eliminate the intracellular ROS levels of bone marrow-derived mesenchymal stem cells (BMSCs) against oxidative damage. Meanwhile, the bioactive and ROS scavenging hydrogels can accelerate bone regeneration in large cranial defects. Overall, this study may provide new insights into the designing of regenerative bone grafts with simultaneously enhanced osteogenic and antioxidant capabilities.

Impact of High-Altitude Hypoxia on Bone Defect Repair: A Review of Molecular Mechanisms and Therapeutic Implications

Reaching areas at altitudes over 2,500–3,000 m above sea level has become increasingly common due to commerce, military deployment, tourism, and entertainment. The high-altitude environment exerts systemic effects on humans that represent a series of compensatory reactions and affects the activity of bone cells. Cellular structures closely related to oxygen-sensing produce corresponding functional changes, resulting in decreased tissue vascularization, declined repair ability of bone defects, and longer healing time. This review focuses on the impact of high-altitude hypoxia on bone defect repair and discusses the possible mechanisms related to ion channels, reactive oxygen species production, mitochondrial function, autophagy, and epigenetics. Based on the key pathogenic mechanisms, potential therapeutic strategies have also been suggested. This review contributes novel insights into the mechanisms of abnormal bone defect repair in hypoxic environments, along with therapeutic applications. We aim to provide a foundation for future targeted, personalized, and precise bone regeneration therapies according to the adaptation of patients to high altitudes.

Interfacial adhesion and surface bioactivity of anodized titanium modified with SiON and SiONP surface coatings

Titanium (Ti) surface modification via coating technologies (plasma spraying, electron-beam deposition) has been used to enhance bone-implant bonding by increasing the rate of hydroxyapatite (HA) formation, a property known as bioactivity. Regardless the enhancement in the surface activity, the high fabrication-temperature (> 600 °C) reduces coating-implant adhesion due to thermal expansion mismatch and reduces bioactivity due to increased crystallinity in the coating. Thus, amorphous surface coatings with strong Ti-substrate adhesion that can be fabricated at relatively low temperatures are crucially needed for enhanced osseointegration. Therefore, this study aimed to enhance the Ti surface bioactivity via strongly adherent bioactive thin film coatings deposited by low temperature (< 400 °C) plasma enhanced chemical vapor deposition technique on nanopore anodized-Ti (A-Ti) surface. Two groups of coating (silicon oxynitride (SiON) and silicon oxynitrophosphide (SiONP)) were deposited on anodized Ti and tested for interfacial adhesion and surface bioactivity. TEM and XPS were used to investigate the interfacial composition while interfacial adhesion was tested using nano-indentation tests which indicated a strong interfacial adhesion between the coatings and the A-Ti substrate. Surface bioactivity of the modified Ti was tested by comprehensive surface characterization (i.e., chemical composition, surface energy, morphology, and mechanical properties) and apatite formation on each surface. SiONP coating significantly enhanced the Ti surface bioactivity that presented the highest surface coverage of carbonated hydroxyapatite (HCA, ~ 40%) with a Ca/P ratio (~ 1.65) close to the stoichiometric hydroxyapatite (~ 1.67) found in bone biomineral. The HCA structure and morphology were confirmed by HR-TEM/SAED, XRD, FT-IR, and HR-SEM/EDX. MSCs in-vitro studies indicated preferable cells adhesion and proliferation on the modified surfaces without any cytotoxic effects. This study concluded that the improved surface bioactivity of Ti-SiON and Ti-SiONP coatings suggests their potential use as strongly adherent bioactive surface coatings for Ti implants.

Multi-functional SiO32--releasing hydrogel with bioinspired mechanical properties and biodegradability for vascularized skeletal muscle regeneration

Vascularized skeletal muscle regeneration remains a great medical need but significant challenge. Biomaterial strategies that can facilitate the regeneration of muscle fibers and blood vessels are unavailable. Herein, we report...

Chitosan-strontium chondroitin sulfate scaffolds for reconstruction of bone defects in aged rats

Bone defects caused by trauma have become increasingly common in aged populations. Clinically, because of the relatively decreased bone healing capacity compared with the youth adults, bone defect repair in the elderly remains challenging. The development of effective biomaterials targeted at bone defects in the elderly is a key component of bone-tissue engineering strategies. However, little attention has been paid to bone regeneration in the elderly. Here, we developed a new scaffold chitosan-Strontium chondroitin sulfate (CH-SrCS) and evaluated its effect on improving bone regeneration. We find that the CH-SrCS scaffold displayed positive effects on downregulation of inflammation and osteoclastogenesis related mRNA expressions while demonstrating a significant increase in the expression level of BMP2. Finally, we show that the bone defects healing effects as assessed using an aged rats' bone defects model. Ultimately, this work also provides insights into the design of effective biomaterials targeted at bone defects in the elderly.

Bioprinting of Stem Cells in Multimaterial Scaffolds and Their Applications in Bone Tissue Engineering

Bioprinting stem cells into three-dimensional (3D) scaffolds has emerged as a new avenue for regenerative medicine, bone tissue engineering, and biosensor manufacturing in recent years. Mesenchymal stem cells, such as adipose-derived and bone-marrow-derived stem cells, are capable of multipotent differentiation in a 3D culture. The use of different printing methods results in varying effects on the bioprinted stem cells with the appearance of no general adverse effects. Specifically, extrusion, inkjet, and laser-assisted bioprinting are three methods that impact stem cell viability, proliferation, and differentiation potential. Each printing method confers advantages and disadvantages that directly influence cellular behavior. Additionally, the acquisition of 3D bioprinters has become more prominent with innovative technology and affordability. With accessible technology, custom 3D bioprinters with capabilities to print high-performance bioinks are used for biosensor fabrication. Such 3D printed biosensors are used to control conductivity and electrical transmission in physiological environments. Once printed, the scaffolds containing the aforementioned stem cells have a significant impact on cellular behavior and differentiation. Natural polymer hydrogels and natural composites can impact osteogenic differentiation with some inducing chondrogenesis. Further studies have shown enhanced osteogenesis using cell-laden scaffolds in vivo. Furthermore, selective use of biomaterials can directly influence cell fate and the quantity of osteogenesis. This review evaluates the impact of extrusion, inkjet, and laser-assisted bioprinting on adipose-derived and bone-marrow-derived stem cells along with the effect of incorporating these stem cells into natural and composite biomaterials.

The Role of Adipose Stem Cells in Bone Regeneration and Bone Tissue Engineering

Bone regeneration is a complex process that is influenced by tissue interactions, inflammatory responses, and progenitor cells. Diseases, lifestyle, or multiple trauma can disturb fracture healing, which might result in prolonged healing duration or even failure. The current gold standard therapy in these cases are bone grafts. However, they are associated with several disadvantages, e.g., donor site morbidity and availability of appropriate material. Bone tissue engineering has been proposed as a promising alternative. The success of bone-tissue engineering depends on the administered cells, osteogenic differentiation, and secretome. Different stem cell types offer advantages and drawbacks in this field, while adipose-derived stem or stromal cells (ASCs) are in particular promising. They show high osteogenic potential, osteoinductive ability, and immunomodulation properties. Furthermore, they can be harvested through a noninvasive process in high numbers. ASCs can be induced into osteogenic lineage through bioactive molecules, i.e., growth factors and cytokines. Moreover, their secretome, in particular extracellular vesicles, has been linked to fracture healing. The aim of this review is a comprehensive overview of ASCs for bone regeneration and bone tissue engineering.

Silicon Oxynitrophosphide Nanoscale Coating Enhances Antioxidant Marker-Induced Angiogenesis During in vivo Cranial Bone-Defect Healing

Critical-sized bone defects are challenging to heal because of the sudden and large volume of lost bone. Fixative plates are often used to stabilize defects, yet oxidative stress and delayed angiogenesis are contributing factors to poor biocompatibility and delayed bone healing. This study tests the angiogenic and antioxidant properties of amorphous silicon oxynitrophosphide (SiONPx) nanoscale-coating material on endothelial cells to regenerate vascular tissue in vitro and in bone defects. in vitro studies evaluate the effect of silicon oxynitride (SiONx) and two different SiONPx compositions on human endothelial cells exposed to ROS (eg, hydrogen peroxide) that simulates oxidative stress conditions. in vivo studies using adult male Sprague Dawley rats (approximately 450 g) were performed to compare a bare plate, a SiONPx-coated implant plate, and a sham control group using a rat standard-sized calvarial defect. Results from this study showed that plates coated with SiONPx significantly reduced cell death, and enhanced vascular tubule formation and matrix deposition by upregulating angiogenic and antioxidant expression (eg, vascular endothelial growth factor A, angiopoetin-1, superoxide dismutase 1, nuclear factor erythroid 2-related factor 2, and catalase 1). Moreover, endothelial cell markers (CD31) showed a significant tubular structure in the SiONPx coating group compared with an empty and uncoated plate group. This reveals that atomic doping of phosphate into the nanoscale coating of SiONx produced markedly elevated levels of antioxidant and angiogenic markers that enhance vascular tissue regeneration. This study found that SiONPx or SiONx nanoscale-coated materials enhance antioxidant expression, angiogenic marker expression, and reduce ROS levels needed for accelerating vascular tissue regeneration. These results further suggest that SiONPx nanoscale coating could be a promising candidate for titanium plate for rapid and enhanced cranial bone-defect healing. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Pulp tissue reaction to a self-adhesive, resin-based direct pulp capping material containing surface pre-reacted glass-ionomer filler

OBJECTIVE

This study aimed to evaluate the effect of direct pulp capping using an experimental self-adhesive resin for direct pulp capping (SRD) containing silica and surface pre-reacted glass-ionomer (S-PRG) filler on pulpal healing and to monitor the dentin bridge formation in rat pulp 2-4 weeks after operation.

METHODS

Five types of SRDs (SRD-0: S-PRG fillers 0 wt%; SRD-1: S-PRG fillers 9.1 wt%; SRD-2: S-PRG fillers 18.4 wt%; SRD-3: S-PRG fillers 27.8 wt%; and SRD-6: S-PRG fillers 57.4 wt%) were prepared, and mineral trioxide aggregate (MTA) was used as control (n = 8). Direct pulp capping was performed on rats that were sacrificed for further evaluation 2 or 4 weeks after the operation. The pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and reparative dentin formation were histopathologically evaluated; the data were statistically analyzed using the Kruskal-Wallis and the Mann-Whitney U tests.

RESULTS

The histopathological evaluation of SRD-1-treated test animals 2 weeks post-operation revealed inferior PTD and ICI when compared with that of MTA. Even 4 weeks after the operation in SRD-1- and SRD-2-treated rats, the PTD and ICI were inferior when compared with those of MTA. The dental specimens of SRD-0 and MTA showed orthodentin formation, whereas SRD-treated test animals showed osteodentin formation at a position slightly deeper than the site of the pulpal exposure.

SIGNIFICANCE

The reparative dentin formed by SRD-0 and MTA was genuine, whereas that formed by SRD-3 and SRD-6 was ossified and ectopic. SRD may have the potential to be utilized clinically as a direct pulp capping material.

The effect of surface pre-reacted glass-ionomer filler eluate on dental pulp cells and mineral deposition on dentin: In vitro study

The effects of surface pre-reacted glass-ionomer (S-PRG) filler on pulpal cells and on the composition of dentinal deposits were investigated. Proliferation (CCK-8), cytotoxicity (LDH), and differentiation activity (ALP) tests, along with cell morphology observations, were conducted at 6 and 24 h after treatment of pulpal cells with different S-PRG filler eluate concentrations. Dentinal surfaces were immersed in deionized water or S-PRG filler eluate followed by immersion in deionized water or simulated body fluid and observed under scanning electron microscope and elemental analysis using energy dispersive x-ray spectrometer. At 24 h, there were significant differences in CCK-8 and ALP activity values between the groups in a concentration-dependent manner. LDH test data were not significantly different among the groups. Cell morphology was not altered at either exposure time. However, decreased cellular density was observed with the highest eluate concentration. Crystalline deposits and occluded dentinal tubules were observed in samples immersed in S-PRG filler with a later immersion in simulated body fluid, which also showed higher concentrations of certain ions compared to surfaces that were not initially treated with S-PRG filler. The lowest two eluate concentrations did not show significant toxicity. S-PRG enhanced the effect of simulated body fluid in the formation of mineral deposits.

A comparative study on silicon nitride, titanium and polyether ether ketone on mouse pre-osteoblast cells

The current study provides more insights about the surface bioactivity of the silicon nitride (Si₃N₄) as a potential candidate for bone regeneration in craniofacial and orthopaedic applications compared with conventional implantation materials. Current skeletal reconstructive materials such as titanium and polyether ether ketone (PEEK) are limited by poor long-term stability, biocompatibility and prolonged healing. Si₃N₄ is an FDA-approved material for an intervertebral spacer in spinal fusion applications. It is biocompatible and has antimicrobial properties. Here, we hypothesize that Si₃N₄ was found to be an osteoconductive material and conducts the growth, differentiation of MC3T3-E1 cells for extracellular matrix deposition, mineralization and eventual bone regeneration for craniofacial and orthopaedic applications. MC3T3-E1 cells were used to study the osteoblastic differentiation and mineralization on sterile samples of Si₃N₄, titanium alloy and PEEK. The samples were then analysed for extracellular matrix deposition and mineralization by FTIR, Raman spectroscopy, SEM, EDX, Alizarin Red, qRT-PCR and ELISA. The in vitro study indicates the formation of collagen fibres and mineral deposition on all three sample surfaces. There was more profound and faster ECM deposition and mineralization on Si₃N₄ surface as compared to titanium and PEEK. The FTIR and Raman spectroscopy show formation of collagen and mineral deposition at 30 days for Si₃N₄ and titanium and not PEEK. The peaks shown by Raman for Si₃N₄ resemble closely to natural bone. Results also indicate the upregulation of osteogenic transcription factors such as RUNX2, SP7, collagen type I and osteocalcin. The authors concluded that Si₃N₄ rapidly conducts mineralized tissue formation via extracellular matrix deposition and biomarker expression in mouse calvarial pre-osteoblast cells. Thus, this study confirms that the bioactive Si₃N₄ could be a potential material for craniofacial and orthopaedic applications leading to rapid bone regeneration that resemble the natural bone structure.

Biological Roles and Delivery Strategies for Ions to Promote Osteogenic Induction

Bone is the most studied tissue in the field of tissue regeneration. Even though it has intrinsic capability to regenerate upon injury, several pathologies and injuries could hamper the highly orchestrated bone formation and resorption process. Bone tissue engineering seeks to mimic the extracellular matrix of the tissue and the different biochemical pathways that lead to successful regeneration. For many years, the use of extrinsic factors (i.e., growth factors and drugs) to modulate these biological processes have been the preferred choice in the field. Even though it has been successful in some instances, this approach presents several drawbacks, such as safety-concerns, short release profile and half-time life of the compounds. On the other hand, the use of inorganic ions has attracted significant attention due to their therapeutic effects, stability and lower biological risks. Biomaterials play a key role in such strategies where they serve as a substrate for the incorporation and release of the ions. In this review, the methodologies used to incorporate ions in biomaterials is presented, highlighting the osteogenic properties of such ions and the roles of biomaterials in controlling their release.

Surgical Sealing of Laterally Localized Accessory Root Canal with Resin Containing S-PRG Filler in Combination with Non-Surgical Endodontic Treatment: A Case Report

The spread of root canal infection to surrounding periodontal tissue through accessory root canals reduces the success rate of endodontic treatment. In this case, cone-beam computed tomography revealed a lesion (4 mm from the apex) resulting from an accessory root canal of the maxillary left central incisor. First, non-surgical endodontic treatment was conducted but the sinus tract remained. Surgical preparation of the root cavity was then conducted to remove potentially infected dentin surrounding the accessory root canal. The cavity was filled and the foramen was sealed with resin containing bioactive surface pre-reacted glass (S-PRG) filler. The photopolymerized resin was then contoured and polished. In combination with subsequent supportive non-surgical endodontic treatment, a good clinical outcome with the disappearance of the sinus tract and clinical symptoms such as discomfort and pressure pain and the regeneration of the alveolar bone hanging over the cavity was obtained. In this case, the good clinical outcome may have been due to the dentin-adhesive property and durability of the pre-adhesive system and composite resin. The better biocompatibility of S-PRG fillers presumably facilitated periodontal tissue healing.

Amorphous Silicon Oxynitrophosphide-Coated Implants Boost Angiogenic Activity of Endothelial Cells

Lack of osteointegration is a major cause of aseptic loosening and failure of implants used in bone replacement. Implants coated with angiogenic biomaterials can improve osteointegration and potentially reduce these complications. Silicon- and phosphorus-based materials have been shown to upregulate expression of angiogenic factors and improve endothelial cell functions. In the present study, we hypothesize that implants coated with amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP) by using plasma-enhanced chemical vapor deposition (PECVD) technique could enhance human umbilical vein endothelial cell angiogenic properties in vitro. The tested groups were: glass coverslip (GCS), tissue culture plate, SiON, SiONP1 (O: 7.3 at %), and SiONP2 (O: 14.2 at %) implants. The SiONP2 composition demonstrated 3.5-fold more fibronectin deposition than the GCS (p < 0.001). The SiONP2 group also presented a significant improvement in the capillary tubule length and thickness compared with the other groups (p < 0.01). At 24 h, we observed at least a twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2, more evident in the SiONP1 and SiONP2 groups. In conclusion, the studied amorphous silica-coated implants, especially the SiONP2 composition, could enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing. Impact Statement In this study, we report for the first time the significant enhancement of human umbilical vein endothelial cell angiogenic properties (in vitro) by the amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP). The SiONP2 demonstrated 3.5-fold more fibronectin deposition than the glass coverslip and presented a significant improvement in the capillary tubule length and thickness. At 24 h, SiONP reported twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2. The studied amorphous silica-coated implants enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing.

Biomimetic Nanosilica-Collagen Scaffolds for In Situ Bone Regeneration: Toward a Cell-Free, One-Step Surgery

Current approaches to fabrication of nSC composites for bone tissue engineering (BTE) have limited capacity to achieve uniform surface functionalization while replicating the complex architecture and bioactivity of native bone, compromising application of these nanocomposites for in situ bone regeneration. A robust biosilicification strategy is reported to impart a uniform and stable osteoinductive surface to porous collagen scaffolds. The resultant nSC composites possess a native-bone-like porous structure and a nanosilica coating. The osteoinductivity of the nSC scaffolds is strongly dependent on the surface roughness and silicon content in the silica coating. Notably, without the use of exogenous cells and growth factors (GFs), the nSC scaffolds induce successful repair of a critical-sized calvarium defect in a rabbit model. It is revealed that topographic and chemical cues presented by nSC scaffolds could synergistically activate multiple signaling pathways related to mesenchymal stem cell recruitment and bone regeneration. Thus, this facile surface biosilicification approach could be valuable by enabling production of BTE scaffolds with large sizes, complex porous structures, and varied osteoinductivity. The nanosilica-functionalized scaffolds can be implanted via a cell/GF-free, one-step surgery for in situ bone regeneration, thus demonstrating high potential for clinical translation in treatment of massive bone defects.

Bisphosphonate-Functionalized Scaffolds for Enhanced Bone Regeneration

The local sustained release of bioactive substances are attracting increasing attention in bone tissue engineering, which is beneficial to bone tissue formation and helps to improve the bone ingrowth ability of a scaffold. Bisphosphonates (BPs), as a representative kind of osteoclast inhibitors, are proven to possess excellent osteogenic induction capability. Accordingly, various physical and chemical strategies are developed to functionalize bone tissue scaffolds with BPs to achieve controlled release profiles. Compared with traditional treatment modalities, local release of BPs from these composite scaffolds will contribute to continuous bone integration without the risk of many complications. This review explores the molecular mechanisms of BPs on bone metabolism and analyzes the appropriate concentrations of BPs that promote bone regeneration. The advanced BP loading strategies, implant modification technologies, and BP-loaded composite scaffolds based on different matrices are summarized. Finally, the latest advances and the future development of BP-modified scaffolds for enhanced bone regeneration are discussed. This article provides leading-edge design strategies of the BP-functionalized bone engineering scaffolds for improved bone repairability.

Role of Nrf2 in Fracture Healing: Clinical Aspects of Oxidative Stress

Fracture healing is a natural process that recapitulates embryonic skeletal development. In the early phase after fracture, reactive oxygen species (ROS) are produced under inflammatory and ischemic conditions due to vessel injury and soft tissue damage, leading to cell death. Usually, such damage during the course of fracture healing can be largely prevented by protective mechanisms and functions of antioxidant enzymes. However, intrinsic oxidative stress can cause excessive toxic radicals, resulting in irreversible damage to cells associated with bone repair during the fracture healing process. Clinically, patients with type-2 diabetes mellitus, osteoporosis, habitual drinkers, or heavy smokers are at risk of impaired fracture healing due to elevated oxidative stress. Although increased levels of oxidative stress markers upon fracture and effects of antioxidants on fracture healing have been reported, a detailed understanding of what causes impaired fracture healing under intrinsic conditions of oxidative stress is lacking. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been identified as a key transcriptional regulator of the expression of antioxidants and detoxifying enzymes. It further not only plays a crucial role in preventing degenerative diseases in multiple organs, but also during fracture healing. This narrative review evaluates the influence of intrinsic oxidative stress on fracture healing and sheds new light on the intriguing role of Nrf2 during bone regeneration in pathological fractures.

Surface Pre-Reacted Glass Filler Contributes to Tertiary Dentin Formation through a Mechanism Different Than That of Hydraulic Calcium-Silicate Cement

The induction of tissue mineralization and the mechanism by which surface pre-reacted glass-ionomer (S-PRG) cement influences pulpal healing remain unclear. We evaluated S-PRG cement-induced tertiary dentin formation in vivo, and its effect on the pulp cell healing process in vitro. Induced tertiary dentin formation was evaluated with micro-computed tomography (μCT) and scanning electron microscopy (SEM). The distribution of elements from the S-PRG cement in pulpal tissue was confirmed by micro-X-ray fluorescence (μXRF). The effects of S-PRG cement on cytotoxicity, proliferation, formation of mineralized nodules, and gene expression in human dental pulp stem cells (hDPSCs) were assessed in vitro. μCT and SEM revealed that S-PRG induced tertiary dentin formation with similar characteristics to that induced by hydraulic calcium-silicate cement (ProRoot mineral trioxide aggregate (MTA)). μXRF showed Sr and Si ion transfer into pulpal tissue from S-PRG cement. Notably, S-PRG cement and MTA showed similar biocompatibility. A co-culture of hDPSCs and S-PRG discs promoted mineralized nodule formation on surrounding cells. Additionally, S-PRG cement regulated the expression of genes related to osteo/dentinogenic differentiation. MTA and S-PRG regulated gene expression in hDPSCs, but the patterns of regulation differed. S-PRG cement upregulated CXCL-12 and TGF-β1 gene expression. These findings showed that S-PRG and MTA exhibit similar effects on dental pulp through different mechanisms.

Rapid Regeneration of Vascularized Bone by Nanofabricated Amorphous Silicon Oxynitrophosphide (SiONP) Overlays

Fracture healing is a complex biological process. Severe bone loss and ischemia from traumatic fractures lead to inflammation and accumulation of damaging reactive oxygen species (ROS). Fixative devices that not only provide mechanical support but also stimulate antioxidants such as superoxide dismutase (SOD1) and influence signaling pathways for extracellular matrix (ECM) mineralization, are critical for normal healing of such fractures. In this study, we report a novel biomaterial, silicon oxynitrophosphide (SiONP) that provides sustained release of ionic silicon (Si⁺⁴) and phosphorous (P) over few weeks under physiological conditions. Anti-oxidant role of Si⁺⁴ and augmented ECM mineralization by P ions lead to enhanced osteogenesis coupled with quick revascularization for rapid bone regeneration. Plasma enhanced chemical vapor deposition (PECVD) provided a conformal, well adherent and highly reproducible surface chemistry overlaid onto nanofabricated bioinspired surfaces. The Nitrogen to P and O content ratio was observed to change the dissolution rate and the release kinetics of the overlaid film. The SiONP films with optimal release kinetics promoted anti-oxidant expression via enhanced SOD1, which downstream upregulated other osteogenic markers with MC3T3-E1 cells. These surfaces also promoted angiogenesis evident by formation of thicker tubules by Human umbilical vein endothelial cells (HUVEC). In-vivo evaluation using a rat critical-sized calvarial defect model showed rapid bone-regeneration for these nanofabricated biomaterials as compared to control groups, and opens new horizon for future clinical trials of new antioxidant materials on biomedical devices that can reduce healing time, lower medical care cost, and increase the quality of newly formed bone in critical size defects.

Silicon nitride enhances osteoprogenitor cell growth and differentiation via increased surface energy and formation of amide and nanocrystalline HA for craniofacial reconstruction

The bioactive silicon nitride (Si₃N₄) has been FDA cleared for use as spinal intervertebral arthrodesis devices. Because its surface properties promote bone ongrowth and ingrowth, it also has the potential to benefit craniofacial reconstruction. Thus, the aim of this work was to determine whether the surface properties of Si₃N₄ could enhance the osteoblast cell growth, differentiation and nucleation of hydroxyapatite (HA) crystals compared to conventional implant materials such as titanium (Ti) and polyether ether ketone (PEEK). X-ray absorbance near-edge structure analysis (XANES) indicated the presence of Si-Si, Si-O and Si-N bonding. Surface wettability studies confirmed that Si₃N₄ exhibits the lowest contact angle and highest surface energy. Cell culture studies showed that osteoblast growth was enhanced on Si₃N₄ after 1 day and up to 7 days. Si₃N₄ surface induced highest surface coverage and thickness of nanocrystalline HA (211) and (203) in cell-free in vitro studies after 7 days of culture. Raman spectroscopy analysis confirmed the presence of surface functional groups consisting of phosphate and carbonate species. Interestingly, Si₃N₄ surface showed amide and hydroxyproline groups, the precursors to collagen, which were not observed on Ti and PEEK surfaces. Furthermore, Si₃N₄ surface indicated high expression of RUNX2, enhanced cell differentiation and dense collagenous ECM after 30 days of the in vitro study. The present study concluded that Si₃N₄ surface enhances osteoprogenitor cell adhesion, growth, RUNX2 expression and ECM formation via the coupled effects of higher surface energy and the presence of amide and nanocrystalline HA functional groups.

Anti-inflammatory and antimicrobial activity of bioactive hydroxyapatite/silver nanocomposites

Biomaterials are often used in orthopedic surgery like cavity fillings. However, related complications often require long-term systemic antibiotics, device removal, and extended rehabilitation. Hydroxyapatite/silver (HA/Ag) composites have been proposed as implantation biomaterials owing to the osteogenic properties of hydroxyapatite and to the antimicrobial efficiency of silver. Nevertheless, higher silver concentrations induce cytotoxic effects. The aim of this study was to synthesize and characterize HA/Ag nanocomposites that will allow us to use lower concentrations of silver nanoparticles with better antimicrobial efficiency and anti-inflammatory properties. The characterization of HA/Ag was performed by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, and laser diffraction. Bioactivity was evaluated under a simulated body fluid. The viability of osteoblast like-cells (MG-63) was determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) and the antimicrobial activity was evaluated by the standard McFarland method. The detection of nitric oxide was measured by a colorimetric assay and the inflammatory cytokines by flow cytometry. We obtained particulate composites of calcium phosphates identified as hydroxyapatite and silver nanoparticles. The bioactivity of the HA/Ag nanocomposites on SFB was confirmed by apatite formations. The viability of MG-63 cells was not affected. We also found antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans owing to the presence of silver nanoparticles at non-cytotoxic concentrations. HA/Ag reduced the release of nitric oxide and decreased the secretion of IL-1 and TNF-α in cells stimulated with Lipopolysaccharide (LPS). In conclusion, the inflammatory and antimicrobial capacity of the HA/Ag nanocomposites, as well as its bioactivity and low cytotoxicity make it a candidate as an implantation biomaterial for bone tissues engineering and clinical practices in orthopedic, oral and maxillofacial surgery.

Analysis of Trauma Intensity during Surgical Bone Procedures Using NF-κB Expression Levels as a Stress Sensor: An Experimental Study in a Wistar Rat Model

Aim and objectives: It is well known that the transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and functions as a pivotal mediator of inflammatory responses. In the present study, we evaluated the trauma generated (inflammatory reaction) after osteotomy bone surgical procedures and placement of implants in the femoral cortical bone of Wistar rats. Surgical stress was evaluated measuring the release and activation of the NF-κB factor. Materials and Methods: Rats were divided into four groups (n = 10) and submitted to different surgical treatments: Control Group (G1 group), only bone perforation was performed without irrigation; Implant Group (G2 group), a titanium implant was inserted after bone perforation without irrigation; Irrigated Group (G3 group) perforations were performed with intense irrigation; and Vitaminic Compound Group (G4 group) surgical perforation was performed without irrigation and a vitaminic compound containing the principal ions present in the natural bone structure was used to fill the bone defect. All animals were euthanized six hours after the surgical procedure and NF-κB levels were determined through immunohistochemical stain followed by direct counting of labeled and unlabeled osteocytes. Results: Among different treated groups, the overall mean of the NF-κB positive cell count in all positions were higher for G1 group (33.4 ± 2.45 cells). NF-κB values were lower in the G2 group (28.9 ± 2.70 cells), whereas in the G3 group (24.3 ± 2.72 cells) as well as in G4 group still lesser NF-κB positive cells were counted (26.5 ± 2.60 cells). Conclusions: The results here presented suggest that maneuvers performed during osteotomy procedures can significantly affect inflammation levels. The NF-κB activation during the surgical procedures can be minimized and/or controlled thought the adequate irrigation or application of adequate substances.

Ionic silicon improves endothelial cells' survival under toxic oxidative stress by overexpressing angiogenic markers and antioxidant enzymes

Oxidative stress, induced by harmful levels of reactive oxygen species, is a common occurrence that impairs proper bone defect vascular healing through the impairment of endothelial cell function. Ionic silicon released from silica-based biomaterials, can upregulate hypoxia-inducible factor-1α (HIF-1α). Yet it is unclear whether ionic Si can restore endothelial cell function under oxidative stress conditions. Therefore, we hypothesized that ionic silicon can help improve human umbilical vein endothelial cells' (HUVECs') survival under toxic oxidative stress. In this study, we evaluated the ionic jsilicon effect on HUVECs viability, proliferation, migration, gene expression, and capillary tube formation under normal conditions and under harmful hydrogen peroxide levels. We demonstrated that 0.5-mM Si4+ significantly enhanced angiogenesis in HUVECs under normal condition (p < 0.05). HUVECs exposed to 0.5-mM Si4+ presented a morphological change, even without the bed of Matrigel, and formed significantly more tube-like structures than the control (p < 0.001). In addition, 0.5-mM Si4+ enhanced cell viability in HUVECs under harmful H2 O2 levels. HIF-1α, vascular endothelial growth factor-A, and vascular endothelial growth factor receptor-2 were overexpressed more than twofold in silicon-treated HUVECs, under normal and toxic H2 O2 conditions. Moreover, the HUVECs were treated with 0.5-mM Si4+ overexpressed superoxide dismutase-1 (SOD-1), catalase-1 (Cat-1), and nitric oxide synthase-3 (NOS3) under normal and oxidative stress environment (p < 0.01). A computational model was used for explaining the antioxidant effect of Si4+ in endothelial cells and human periosteum cells by SOD-1 enhancement. In conclusion, we demonstrated that 0.5-mM Si4+ can recover the HUVECs' viability under oxidative stress conditions by reducing cell death and upregulating expression of angiogenic and antioxidant factors.

Effect of lycopene on titanium implant osseointegration in ovariectomized rats

Background

Lycopene prevents bone loss in osteopenic models. However, the role of lycopene in the success rate of dental implants under osteopenic conditions remains unknown. The aim of this study was to evaluate whether lycopene prevents delayed implant osseointegration in an ovariectomized (OVX) rat model.

Methods

Thirty female Sprague-Dawley rats were randomly divided into the following groups: OVX with vehicle (OVX group), OVX with lycopene (OVX + lycopene group) and sham-operated with vehicle (sham group). Twelve weeks after ovariectomy or sham operation, titanium implants were placed into the distal metaphysis of the bilateral femurs of each rat. These rats were subsequently gavaged with lycopene (50 mg/kg/day) or vehicle. After 12 weeks of gavage, all rats were sacrificed, and specimens were harvested. Sample osseointegration was evaluated by biomechanical testing, 3D micro-computed tomography (micro-CT) analysis and histomorphometric analysis.

Results

Compared with the OVX group, the OVX + lycopene group showed a 69.3% increase in the maximum push-out force (p < 0.01). Micro-CT data for the femurs in the OVX + lycopene group showed significantly higher bone volume, trabecular thickness and less trabecular space than did those in the OVX group. The bone area (BA) around the implant and bone contact (BC) with the implant were increased by 72.3% (p < 0.01) and 51.4% (p < 0.01) in the OVX + lycopene group, respectively, compared with those in the OVX group. There was no significant difference in the mechanical test, micro-CT scanning and histomorphometric data between the OVX + lycopene and sham groups (p > 0.05).

Conclusions

Lycopene improved implant osseointegration, fixation and bone formation under osteopenic conditions, suggesting that lycopene is a promising therapeutic agent to prevent delayed implant osseointegration and bone loss under osteopenic conditions.

Application of a direct pulp capping cement containing S-PRG filler

OBJECTIVES

To evaluate new pulp capping cements containing surface pre-reacted glass ionomer (S-PRG) filler and to investigate ion release kinetics and pH shift of eluates from the cement.

MATERIALS AND METHODS

Molars of Wistar rats were directly pulp capped using three kinds of cement containing S-PRG filler and mineral tri-oxide aggregate (MTA) was used as a control. After 1, 2, or 4 weeks, histological evaluation was performed and differences of tertiary dentin formation were analyzed. Release of Sr²⁺, BO₃^3-, SiO₃^2-, Na⁺, and Al³⁺ ions was determined by inductively coupled plasma-atomic emission spectrometry, and F^- ion release was measured using a fluoride ion selective electrode. The pH of the eluate from each cement after mixing was measured with a pH electrode.

RESULTS

One of S-PRG cements promoted tertiary dentin formation to the same extent as the control (p > 0.05) and it showed a tendency of less inflammatory response. This cement released more BO₃^3- and SiO₃^2-, but less Sr²⁺, Na⁺, and F^- than other S-PRG specimens. Each cement recovered nearly neutral compared with glass ionomer cement.

CONCLUSIONS

S-PRG cement induced tertiary dentin formation based on multiple ion releases, suggesting that it is suitable as a pulp capping material.

CLINICAL RELEVANCE

This new material can be an alternative pulp capping agent to MTA.

Role of Hydrogen and Nitrogen on the Surface Chemical Structure of Bioactive Amorphous Silicon Oxynitride Films

Silicon oxynitride (Si-O-N) is a new biomaterial in which its O/N ratio is tunable for variable Si release and its subsequent endocytotic incorporation into native hydroxyapatite for enhanced bone healing. However, the effect of nitrogen and hydrogen bonding on the formation and structure of hydroxyapatite is unclear. This study aims to uncover the roles of H and N in tuning Si-O-N surface bioactivity for hydroxyapatite formation. Conformal Si-O-N films were fabricated by plasma-enhanced chemical vapor deposition (PECVD) onto Ti/Si substrates. Fourier transform infrared spectroscopy (FTIR) and Rutherford backscattering spectrometry (RBS) analysis indicated increased Si-H and N-H bonding with increased N content. Surface energy decreased with increased N content. X-ray absorbance near edge structure (XANES) analysis showed tetrahedral coordination in O-rich films and trigonal coordination in N-rich films. O-rich films exhibited a 1:1 ratio of 2p3/2 to 2p1/2 electron absorbance, while this ratio was 1.73:1 for N-rich films. Both Si and N had a reduced partial charge for both O- and N-rich films, whereas O maintained its partial charge for either film. O-rich films were found to exhibit random bonding SizOxNy, while N-rich films exhibited random mixing: [Si-Si]-[Si-O]-[Si-N]. Thus, hydrogen bonding limits random nitrogen bonding in Si-O-N films via surface Si-H and N-H bonding. Moreover, increased nitrogen content reduces the partial charge of constituent elements and changes the bonding structure from random bonding to random mixing.

Development of a SiYAlON glaze for improved osteoconductivity of implantable medical devices

The application of bioactive coatings onto orthopaedic appliances is commonly performed to compensate for the otherwise bioinert nature of medical devices and to improve their osseointegration. Calcium phosphates, hydroxyapatite (HAp), and bioglasses are commercially available for this purpose. Until recently, few other inorganic compounds have been identified with similar biofunctionality. However, silicon nitride (Si₃ N₄ ) has emerged as a new orthopaedic material whose unique surface chemistry also enhances osteoconductivity. Recent research has confirmed that its minority intergranular phase, consisting of silicon yttrium aluminum oxynitride (SiYAlON), is principally responsible for this improvement. As a result, it was hypothesized that SiYAlON itself might serve as an effective osteoconductive coating or glaze for medical devices. To test this hypothesis, a process inspired by traditional ceramic whiteware glazing was developed. A slurry containing ingredients similar to the intergranular SiYAlON composition was applied to a Si₃ N₄ surface, which was then subjected to a heat treatment to form a glaze. Various analytical tools were employed to assess its chemistry and morphology. It was found that the glaze was comprised predominately of Y₅ Si₃ O₁₂ N, a compound commonly referred to as N-apatite, which is isostructural to native HAp. Subsequent exposure of the glazed surface to acellular simulated body fluid led to increased deposition of biomimetic HAp-like crystals, while exposure to Saos-2 osteosarcoma cells in vitro resulted in greater HAp deposition relative to control samples. The observation that SiYAlON exhibits enhanced osteoconductivity portends its potential as a therapeutic aid in bone and tissue repair. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1084-1096, 2018.

Interleukin-6 as possible early marker of stress response after femoral fracture

Bone fracture healing is a complex process which at best results in full recovery of function and structure of injured bone tissue, but all the mechanisms involved in this process, and their mutual interaction, are not fully understood. Despite advancement of surgical procedures, this type of fractures is still a major public health concern. In the last few decades, a lot of attention is focused on the oxygen-free radicals and inflammatory response markers as important factors of skeletal injury. Thus, the aim of the present study was to follow the changes in redox balance and inflammatory response in elderly patients with femoral fractures during the earliest stages of fracture healing, by measuring the values of the observed markers immediately after fracture, as well as the first, third, and seventh postoperative day. Present study was performed on a group of 65 elderly patients with femoral neck fractures, recruited from the Orthopedic Clinic, Clinical Centre Kragujevac in the period from February to May 2015. Redox status was measured spectrophotometrically and evaluated by measuring the levels of index of lipid peroxidation (measured as TBARS), nitrite (NO₂^-), superoxide anion radical (O₂^-), and hydrogen peroxide (H₂O₂) in plasma, while activities of corresponding antioxidative enzymes, catalase (CAT), superoxide dismutase (SOD), and reduced glutathione (GSH) were measured in erythrocytes. The cytokine concentrations of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were determined in plasma, using ELISA assays specific for human cytokines. Our study showed that redox status and TNF-α in elderly patients with femoral fractures did not show statistically significant changes during the early phase of fracture healing. On the other hand, IL-6 increased statistically in first day after intervention. This preliminary study has shown our observations, and we hope that these results may help in better understanding mechanisms which are included at fracture healing. More importantly, this study attempted to create a platform for further research.