Mixed-ligand copper(II) complex of quercetin regulate osteogenesis and angiogenesis

Synthesis and Characterization of a Strontium-Quercetin Complex and Its In Vitro and In Vivo Potential for Application in Bone Regeneration

Progress has been made toward developing therapies to treat bone-related diseases and defects caused by trauma. However, some of these therapies, such as administering strontium ranelate to treat osteoporosis, have significant side effects. In this context, designing new and safer strontium-based materials constitutes an important current challenge. Here, we have used quercetin as a platform to synthesize a new complex based on strontium and evaluate its activity in vitro and in vivo. First, we carried out strontium complexation with quercetin. Then, we employed Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermal gravimetric analysis to determine the chemical composition of the resulting complex as [(C15H7O7)Sr2]·6(H2O), which was also supported by theoretical calculations. This complex enhanced osteogenic differentiation of a preosteoblastic cell line in vitro, which increased alkaline phosphatase activity and extracellular matrix mineralization. By using a periapical lesion model in mice, we tested whether treatment with this complex could regenerate bone defects in vivo and found that the lesions decreased after 7 days. Together, our data showed that the strontium-quercetin complex synthesized herein is a potential candidate for developing new bone regeneration therapies.

Nrf2 Activation as a Therapeutic Target for Flavonoids in Aging-Related Osteoporosis

Biological aging is a substantial change that leads to different diseases, including osteoporosis (OP), a condition involved in loss of bone density, deterioration of bone structure, and increased fracture risk. In old people, there is a natural decline in bone mineral density (BMD), exacerbated by hormonal changes, particularly during menopause, and it continues in the early postmenopausal years. During this transition time, hormonal alterations are linked to elevated oxidative stress (OS) and decreased antioxidant defenses, leading to a significant increase in OP. Aging is significantly associated with an abnormal ratio of oxidant/antioxidant and modified nuclear factor erythroid-derived two related factor2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) pathway. OS adversely affects bone health by promoting osteoclastic (bone resorbing) activity and impairing osteoblastic (bone-forming cells). Nrf2 is critical in controlling OS and various cellular processes. The expression of Nrf2 is linked to multiple age-related diseases, including OP, and Nrf2 deficiency leads to unbalanced bone formation/resorption and a consequent decline in bone mass. Various drugs are available for treating OP; however, long-term uses of these medicines are implicated in diverse illnesses such as cancer, cardiovascular, and stroke. At the same time, multiple categories of natural products, in particular flavonoids, were proposed as safe alternatives with antioxidant activity and substantial anti-osteoporotic effects.

Hydrazone copper(II) complexes suppressed lung adenocarcinoma by activating multiple anticancer pathway

Activating multiple anti-cancer pathways has great potential for tumor treatment. Herein, we synthesized two binuclear Cu(II) hydrazone complexes ([Cu2(HL1)2Cl2] 1 and [Cu2(HL1)2Br2] 2) and two mononuclear hydrazone-Cu(II) complexes ([Cu(HL2)Cl]·CH3OH 3 and [Cu(HL2)(H2O)Br]·2H2O 4), to evaluate their anti-lung cancer activities. MTT assays revealed that the Cu(II) complexes demonstrate superior anticancer activity compared to cisplatin. Among them, complex 3 exhibited selective toxicity towards A549 cancer cells in comparison to normal cells and demonstrated hemolytic activity comparable to cisplatin. The low toxicity and effective antitumor capabilities of complex 3 have been confirmed in xenograft experiments using A549 tumor-bearing mice. Interestingly, complex 3 eradicates lung tumor cells both in vivo and in vitro by initiating multiple anticancer pathways, including cuproptosis. Our research extends the study of hydrazone copper complexes and provides strategies for the treatment of lung cancer.

Exploring the Correlation Between the Molecular Structure and Biological Activities of Metal-Phenolic Compound Complexes: Research and Description of the Role of Metal Ions in Improving the Antioxidant Activities of Phenolic Compounds

We discussed and summarized the latest data from the global literature on the action of polyphenolic antioxidants and their metal complexes. The review also includes a summary of the outcomes of theoretical computations and our many years of experimental experience. We employed various methods, including spectroscopy (FT-IR, FT-Raman, NMR, UV/Vis), X-ray diffraction, thermal analysis, quantum calculations, and biological assays (DPPH, ABTS, FRAP, cytotoxicity, and genotoxicity tests). According to our research, the number and position of hydroxyl groups in aromatic rings, as well as the delocalization of electron charge and conjugated double bonds, have a major impact on the antioxidant effectiveness of the studied compounds. Another important factor is metal complexation, whereby high ionic potential metals (e.g., Fe(III), Cr(III), Cu(II)) enhance antioxidant properties by stabilizing electron charge, while the low ionic potential metals (e.g., Ag(I), Hg(II), Pb(II)) reduce efficacy by disrupting electron distribution. However, we observed no simple correlation between ionic potential and antioxidant capacity. This paper gives insights that will aid in identifying new, effective antioxidants, which are vital for nutrition and the prevention of neurodegenerative illnesses. Our results outline the connections between biological activity and molecular structure, offering a foundation for the methodical design of antioxidants. Our review also shows in detail how we use various complementary methods to assess the impact of metals on the electronic systems of ligands. This approach moves beyond the traditional "trial and error" method, allowing for the more efficient and rational development of future antioxidants.

Copper metabolism in osteoarthritis and its relation to oxidative stress and ferroptosis in chondrocytes

Ferroptosis, an iron-ion-dependent process of lipid peroxidation, damages the plasma membrane, leading to non-programmed cell death. Osteoarthritis (OA), a prevalent chronic degenerative joint disease among middle-aged and older adults, is characterized by chondrocyte damage or loss. Emerging evidence indicates that chondrocyte ferroptosis plays a role in OA development. However, most research has concentrated on ferroptosis regulation involving typical iron ions, potentially neglecting the significance of elevated copper ions in both serum and joint fluid of patients with OA. This review aims to fill this gap by systematically examining the interplay between copper metabolism, oxidative stress, ferroptosis, and copper-associated cell death in OA. It will provide a comprehensive overview of copper ions' role in regulating ferroptosis and their dual role in OA. This approach seeks to offer new insights for further research, prevention, and treatment of OA.

Poly(vinyl chloride) Films Incorporated with Antioxidant ZnO-Flavonoid Nanoparticles: A Strategy for Food Preservation

Antioxidant films were prepared using poly(vinyl chloride) (PVC) incorporated with 0.5% or 1.0% zinc oxide (ZnO)-flavonoid (quercetin or morin) nanoparticles (NPZnO-Q% or NPZnO-M%) via the casting method. NP incorporation within the polymer matrix influenced the structural, morphological, optical, and thermal properties of the PVC-based films, as well as their antioxidant activity as assessed using the DPPH radical scavenging method. Our results indicated that increasing ZnO-flavonoid NP concentration increased films thickness, while reducing ultraviolet light (UV) transmittance but conserving transparency. The presence of NPZnO-Q% or NPZnO-M% improved the surface uniformity and thermal stability of the active films. In terms of antioxidant activity, there was an enhancement in the DPPH radical scavenging capacity (PVC/ZnO-Q1.0% > PVC/ZnO-Q0.5% > PVC/ZnO-M0.5% > PVC/ZnO-M1.0% > PVC), suggesting that the packaging can help protect food from oxidative processes. Therefore, these antioxidant films represent an innovative strategy for using as active food packaging material, especially intended for aiding in quality preservation and extending the shelf life of fatty foods.

Exploring the osteogenic potential of chitosan-quercetin bio-conjugate: In vitro and in vivo investigations in osteoporosis models

Anti-osteoporotic agents are clinically employed to improve bone health and prevent osteoporotic fractures. In the current study, we investigated the potential of chitosan-quercetin bio-conjugate as an anti-osteoporotic agent. The conjugate was prepared and characterized by FTIR and found notable interactions between chitosan and quercetin. Treating mouse MSCs with the bioconjugate in osteogenic conditions for a week led to elevated expression of differentiation markers Runx2, ALP, and Col-I, as determined by real-time PCR analysis. Evaluation at the cellular level using alizarin red staining demonstrated enhanced calcium deposition in MSCs following treatment with the bioconjugate. Likewise, ELISA analysis showed significantly elevated levels of secretory osteocalcin and osteonectin in groups treated with the conjugate. To broaden our comprehension, we utilized a zebrafish-based in vivo model of dexamethasone-induced osteoporosis to investigate bone regeneration. Toxicity profiling with zebrafish larvae confirmed the bio-conjugate's compatibility at a concentration of 25 μg/ml, underscoring the significance of finding the right dosage. Furthermore, in zebrafish models of osteoporosis, the bio-conjugate demonstrated significant potential for bone regeneration, as indicated by improved bone calcification, callus formation, and overall bone healing in a tail fin fracture model. Additionally, the study revealed that the bio-conjugate inhibited osteoclastic activity, leading to reduced TRAP activity and hydroxyproline release, suggesting its effectiveness in mitigating bone resorption. In conclusion, our research provides compelling evidence for the osteogenic capabilities of the chitosan-quercetin bio-conjugate, highlighting its promising applications in regenerative medicine and the treatment of conditions like osteoporosis.

Glutathione-Scavenging Celastrol-Cu Nanoparticles Induce Self-Amplified Cuproptosis for Augmented Cancer Immunotherapy

Cuproptosis is a novel copper-dependent programmed cell death. The efficacy of cuproptosis is highly dependent on intracellular copper accumulation and counteracted by a high level of glutathione (GSH) in tumor cells. Here, this work develops a self-amplified cuproptosis nanoparticles (Cel-Cu NP) using celastrol (Cel), a natural product isolated from medical plant. In Cel-Cu NP, Cel serves as a versatile copper ionophore, exhibiting an ideal coordination capacity toward copper ions without compromising the cuproptosis induction. Notably, Cel can simultaneously scavenge GSH content to amplify cuproptosis. Moreover, this self-amplified cuproptosis further activates immunogenic cell death (ICD) to elicit robust immune response. Combining with immune checkpoint blockade, Cel-Cu NP effectively eradicates metastatic tumors in a mouse lung metastasis model. This study provides an efficient nanomedicine by inducing self-amplified cuproptosis for robust immunotherapy.

Quercetin in Osteoporosis Treatment: A Comprehensive Review of Its Mechanisms and Therapeutic Potential

PURPOSE OF REVIEW

This review aims to provide a theoretical basis and insights for quercetin's clinical application in the prevention and treatment of osteoporosis (OP), analyzing its roles in bone formation promotion, bone resorption inhibition, anti-inflammation, antioxidant effects, and potential mechanisms.

RECENT FINDINGS

OP, a prevalent bone disorder, is marked by reduced bone mineral density and impaired bone architecture, elevating the risk of fractures in patients. The primary approach to OP management is pharmacotherapy, with quercetin, a phytochemical compound, emerging as a focus of recent interest. This natural flavonoid exerts regulatory effects on bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts and promotes bone health and metabolic equilibrium via anti-inflammatory and antioxidative pathways. Although quercetin has demonstrated significant potential in regulating bone metabolism, there is a need for further high-quality clinical studies focused on medicinal quercetin.

Bi-functional quercetin/copper nanoparticles integrating bactericidal and anti-quorum sensing properties for preventing the formation of biofilms

Biofilms formed by pathogenic bacteria present a persistent risk to human health. While the eradication of matured biofilms remains a formidable challenge, delaying or preventing their formation, which is coordinately regulated by quorum sensing (QS), presents a simpler and more advantageous strategy. Quercetin, a naturally occurring compound with anti-QS properties, has the potential to act as an antibiofilm agent. However, it is plagued by certain inherent drawbacks, including poor water solubility and limited bioavailability. Furthermore, solely blocking QS is not enough to prevent biofilm formation because it lacks bactericidal properties. To address these difficulties, we fabricated bi-functional nanoparticles through the co-assembly of quercetin and copper ions in a facile manner. The resulting quercetin/copper nanoparticles (QC NPs) demonstrated minimal cytotoxicity and hemolysis in vitro. In response to the low pH of microenvironments that were populated by bacterial colonies, the QC NPs underwent disassembly to release copper ions and quercetin. The former exterminated bacteria by disrupting the integrity of the cell membrane, while the latter disrupted the processes involved in QS that are responsible for the biofilm by downregulating the expression of specific genes, effectively preventing the formation of biofilms by both Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. In addition, the QC NPs were integrated into a bacterial cellulose membrane. The composite membrane proved to be highly effective at inhibiting biofilm formation in vitro and demonstrated the ability to reduce inflammatory responses and accelerate the healing of bacteria-infected wounds in vivo. Overall, the bi-functional QC NPs hold great potential for use in addressing the challenges associated with the management of bacterial biofilms.

Assessment of Mononuclear/Dinuclear copper acylhydrazone complexes for lung cancer treatment

Non-platinum metal-based complexes have good potential for cancer treatment. Here, we designed and synthesized five hydrazone copper(II) complexes, [Cu2(HL)2Cl2] 1A, [Cu2(HL)2(NO3)H2O]·NO3 2A, [Cu2(HL)2Br2] 3A, [Cu(L)pyridine] 1B and [Cu(HL)(pyridine)Br] 3B, and evaluated their anti-lung cancer activities. MTT experiments revealed that these copper(II) complexes exhibit higher anticancer activity than cisplatin. Mechanism studies revealed that complex 3A induced G1 phase cell cycle arrest, and induced cell apoptosis via reactive oxygen species (ROS)-mediated mitochondrial dysfunction. Scratch wound healing assay was also performed, revealing that complex 3A have good anti-cell migration activity. Hemolysis assays showed good blood biocompatibility of complex 3A. Furthermore, complex 3A can significantly inhibit the proliferation of A549 3D tumor spheroid. An in vivo anticancer study showed that complex 3A could delays the growth of A549 tumor xenografts with lower systemic toxicity. These results highlight the great possibility of developing highly active copper complexes as anti-lung cancer agents.

Copper-flavonoid family of complexes involved in alkaline phosphatase activation

The flavonoid naringenin and a family of naringenin derivative Cu(II) complexes having phenanthroline-based second ligands were selected to study alkaline phosphatase activation. This enzyme plays a critical role in tissue formation, increasing the inorganic phosphate formation, favoring mineralization, and being essential to producing bone mineralization. The effects of those compounds on the function and structure of the enzyme were evaluated by kinetic measurements, fluorescence, FTIR, and UV-Vis spectroscopies. The results showed that naringenin did not affect alkaline phosphatase activity, having a value of the Michaelis-Menten-constant close to the enzyme (Km = 3.07 × 10-6). The binary complex, Cu(II)-naringenin, and the ternary complex Cu(II)-naringenin-phenanthroline behaved as an enzyme activator in all the concentrations range used in this study. Those complexes increased in c.a. 1.9% the catalytic efficiency concerning enzyme and naringenin. The ternary complex Cu(II)-naringenin-bathophenanthroline, provokes an activator mixed effect, dependent on the substrate concentrations. The different kinetic behavior can be correlated with different conformational changes observed under the interaction with ALP. Fluorescence experiments showed a raising of the binding constant with temperature. FTIR determinations showed that the complex with bathophenanthroline modifies the ALP structure but maintains the helical structure. The other copper complexes provoked a structural unfolding, decreasing the α-helix content. None of them affect the dephosphorylation enzyme ability. Even though the interactions and structural modifications on ALP are different, it is evident that the presence of copper favors enzymatic activity. The observed electrostatic interactions probably benefit the dissociation of the bound phosphate. The results suggest potential biological applications for the studied compounds.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

In vitro and in vivo investigation of chrysin chelated copper complex as biocompatible materials for bone tissue engineering applications

Flavonoid metal complexes have interesting properties and are widely explored for bone regeneration owing to their potent biological activity. In the present study, we investigated the biocompatibility and osteogenic properties of the Copper(II)-chrysin complex (C/Cu). The biocompatibility of C/Cu was assessed in vitro with human osteoblastic cells and in vivo using chick embryo and zebrafish models. The C/Cu complex was found to be cytofriendly with good biocompatibility. The osteogenic property of C/Cu was studied at cellular and molecular levels. C/Cu promoted mineralization in osteoblastic cultures by increasing ALP activity. At the molecular level, C/Cu significantly promoted the mRNA levels of osteoblast differentiation marker genes such as runt-related transcription factor 2 (Runx2), Type 1 collagen and ALP. In addition to this, secretory proteins, osteonectin (ON) and osteocalcin (OC) levels were also stimulated. We have also identified that C/Cu exhibited enhanced osteogenic properties and antibacterial activity compared with Chrysin. Thus, C/Cu can be used as an osteogenic agent in bone tissue engineering.

Hitchhiking into a cell: flavonoids may produce complexes with transition metals for transmembrane translocation

Flavonoids are a group of food polyphenols that are delivered to the human body with plant foods. In recent years, these substances have attracted the attention of researchers due to their effectiveness in preventing a wide variety of diseases, including neurodegenerative, oncological, autoimmune, and cardiovascular. Similar pathologies may also occur with a lack of some first-row transition metals, including Cu(II), Zn(II), Mn(II), Fe(II/III). It is noteworthy that flavonoids are known as transition metal chelators. When a complex with these metals is formed, the therapeutic effect of flavonoids can be enhanced, assuming the possibility of synergy. Molecular models have shown that the lipophilicity of flavonoid-metal complexes can vary significantly depending on their binding stoichiometry. Therefore, a unique process of translocation of flavonoid-metal complexes of various lipophilicity through cell membranes is assumed, based on the possibility of their sequential association and dissociation, called "hitchhiking". It is expected that studies of the interaction of flavonoids with metals will improve the effectiveness of drugs based on flavonoids.

Angiogenic and Osteogenic Effects of Flavonoids in Bone Regeneration

Bone is a highly vascularised tissue that relies on a close spatial and temporal interaction between blood vessels and bone cells. As a result, angiogenesis is critical for bone formation and healing. The vascular system supports bone regeneration by delivering oxygen, nutrients, and growth factors, as well as facilitating efficient cell-cell contact. Most clinical applications of engineered bone grafts are hampered by insufficient vascularization after implantation. Over the last decade, a number of flavonoids have been reported to have osteogenic-angiogenic potential in bone regeneration because of their excellent bioactivity, low cost, availability, and minimal in vivo toxicity. During new bone formation, the osteoinductive nature of certain flavonoids is involved in regulating multiple signaling pathways contributing toward the osteogenic-angiogenic coupling. This review briefly outlines the osteogenic-angiogenic potential of those flavonoids and the mechanisms of their action in promoting bone regeneration. However, further studies are needed to investigate their delivery strategies and establish their clinical efficacy. This article is protected by copyright. All rights reserved.

Non-destructive molecular FTIR spectromicroscopy for real time assessment of redox metallodrugs

Recent emergence of FTIR spectromicroscopy (micro-FTIR) as a dynamic spectroscopy for imaging to study biological chemistry has opened new possibilities for investigating in situ drug release, redox chemistry effects on biological molecules, DNA and drug interactions, membrane dynamics, and redox reactions with proteins at the single cell level. Micro-FTIR applied to metallodrugs has been playing an important role since the last decade because of its great potential to achieve more robust and controlled pharmacological effects against several diseases, including cancer. An important aspect in the development of these drugs is to understand their cellular properties, such as uptake, accumulation, activity, and toxicity. In this review, we present the potential application of micro-FTIR and its importance for studying metal-based drugs, highlighting the perspectives of chemistry of living cells. We also emphasise bioimaging, which is of high importance to localize the cellular processes, for a proper understanding of the mechanism of action.

Traditional Chinese Medicine Compound-Loaded Materials in Bone Regeneration

Bone is a dynamic organ that has the ability to repair minor injuries via regeneration. However, large bone defects with limited regeneration are debilitating conditions in patients and cause a substantial clinical burden. Bone tissue engineering (BTE) is an alternative method that mainly involves three factors: scaffolds, biologically active factors, and cells with osteogenic potential. However, active factors such as bone morphogenetic protein-2 (BMP-2) are costly and show an unstable release. Previous studies have shown that compounds of traditional Chinese medicines (TCMs) can effectively promote regeneration of bone defects when administered locally and systemically. However, due to the low bioavailability of these compounds, many recent studies have combined TCM compounds with materials to enhance drug bioavailability and bone regeneration. Hence, the article comprehensively reviewed the local application of TCM compounds to the materials in the bone regeneration in vitro and in vivo. The compounds included icariin, naringin, quercetin, curcumin, berberine, resveratrol, ginsenosides, and salvianolic acids. These findings will contribute to the potential use of TCM compound-loaded materials in BTE.

Re-appraising the role of flavonols, flavones and flavonones on osteoblasts and osteoclasts- A review on its molecular mode of action

Bone disorders have become a global concern illustrated with decreased bone mineral density and disruption in microarchitecture of natural bone tissue organization. Natural compounds that promote bone health by augmenting osteoblast functions and suppressing osteoclast functions has gained much attention and offer greater therapeutic value compared to conventional therapies. Amongst several plant-based molecules, flavonoids act as a major combatant in promoting bone health through their multi-faceted biological activities such as antioxidant, anti-inflammatory, and osteogenic properties. They protect bone loss by regulating the signalling cascades involved in osteoblast and osteoclast functions. Flavonoids augment osteoblastogenesis and inhibits osteoclastogenesis through their modulation of various signalling pathways. This review discusses the role of various flavonoids and their molecular mechanisms involved in maintaining bone health by regulating osteoblast and osteoclast functions.

Enhanced bone formation in rat critical-size tibia defect by a novel quercetin-containing alpha-calcium sulphate hemihydrate/nano-hydroxyapatite composite

We developed an innovative method to include quercetin into alpha-calcium sulphate hemihydrate/nano-hydroxyapatite (α-CSH/n-HA), to prepare a novel quercetin-containing α-CSH/n-HA composite (Q-α-CSH/n-HA). The physicochemical properties, and ability of Q-α-CSH/n-HA to promote cell proliferation, migration, and osteogenic differentiation of bone marrow stem cells (BMSCs) in vitro were examined. Further, the potential of Q-α-CSH/n-HA to promote bone defect repair was studied using a Sprague-Dawley rat model of critical tibial defects. Imaging was conducted by radiography and micro-CT, and bone defect repairs were observed by histopathological staining. Addition of quercetin clearly increased the porosity of the degraded composite, which elevated the cell proliferation rate, migration ability, osteogenesis differentiation, and mineralisation of BMSCs. Further, quercetin-containing composite increased the expression levels of OSX, RUNX2, OCN, ALP, BMP-2, OPN, BSP, SMAD2, and TGF-β in BMSCs, while it downregulated TNF-α. X-ray and micro-CT imaging showed that the quercetin-containing composite significantly enhanced bone defect repair and new bone in formation. Haematoxylin and eosin, Goldner, and Safranin O staining also showed that quercetin significantly increased new bone generation and promoted composite degradation and absorption. Moreover, immunofluorescence assay revealed that quercetin significantly increased the number of RUNX2/OSX/OCN-positive cells. Overall, our data demonstrate that Q-α-CSH/n-HA has excellent biocompatibility, bone conductivity, and osteo-induction performance in vitro and mediates enhanced overall repair effects and bone reconstruction in vivo, indicating that it is a promising artificial bone graft to promote bone regeneration.

Concomitant Effect of Quercetin- and Magnesium-Doped Calcium Silicate on the Osteogenic and Antibacterial Activity of Scaffolds for Bone Regeneration

Quercetin is a bioflavonoid which has a broad spectrum of biological activity. Due to its lower chemical stability, it is usually encapsulated, or a metal–quercetin complex is formed to enhance its biological activity at a lower concentration. Here, our novel approach was to form a quercetin complex to magnesium-doped calcium silicate (CMS) ceramics through a coprecipitation technique so as to take advantage of quercetin’s antibacterial activity within the antibacterial and osteogenic potential of the silicate. Due to quercetin’s inherent metal-chelating ability, (Ca+Mg)/Si increased with quercetin concentration. Quercetin in magnesium-doped calcium silicate ceramic showed concentration-dependent pro-oxidant and antioxidant activity in SaOS-2 with respect to quercetin concentration. By optimizing the relative concentration, we were able to achieve 3-fold higher proliferation and 1.6-fold higher total collagen at day 14, and a 1.7-fold higher alkaline phosphatase production at day 7 with respect to polycaprolactone/polyvinylpyrrolidone (PCL/PVP) scaffold. Quercetin is effective against Gram-positive bacteria such as S. aureus. Quercetin is coupled with CMS provided similar effect with lower quercetin concentration than quercetin alone. Quercetin reduced bacterial adhesion, proliferation and biofilm formation. Therefore, quercetin-coupled magnesium-doped calcium silicate not only enhanced osteogenic potential, but also reduced bacterial adhesion and proliferation.

Copper-based biomaterials for bone and cartilage tissue engineering

Backgroud

Tissue engineering using cells, scaffolds, and bioactive molecules can promote the repair and regeneration of injured tissues. Copper is an essential element for the human body that is involved in many physiological activities and in recent years, copper has been used increasingly in tissue engineering.

Methods

The current advances of copper-based biomaterial for bone and cartilage tissue engineering were searched on PubMed and Web of Science.

Results

Various forms of copper-based biomaterials, including pure copper, copper ions, copper nanoparticles, copper oxides, and copper alloy are introduced. The incorporation of copper into base materials provides unique properties, resulting in tuneable porosity, mechanical strength, degradation, and crosslinking of scaffolds. Copper also shows promising biological performance in cell migration, cell adhesion, osteogenesis, chondrogenesis, angiogenesis, and antibacterial activities. In vivo applications of copper for bone and cartilage tissue engineering are discussed.

Conclusion

This review focuses on copper’s physiochemical and biological effects, and its applications in bone and cartilage tissue engineering. The potential limitations and future perspectives are also discussed.

Translational potential of this article

This review introduces the recent advances in copper-based biomaterial for bone and cartilage tissue engineering. This revie could guide researchers to apply copper in biomaterials, improving the generation of bone and cartilages, decrease the possibility of infection and shorten the recovery time so as to decrease medical costs.

Bio-inspired multifunctional collagen/electrospun bioactive glass membranes for bone tissue engineering applications

Treatment of bone disease and disorders is often challenging due to its complex structure. Each year millions of people needs bone substitution materials with quick recovery from diseases conditions. Synthetic bone substitutes mimicking structural, chemical and biological properties of bone matrix structure will be very obliging and of copious need. In this work, we reported on the fabrication of bioinspired, biomimetic, multifunctional bone-like three-dimensional (3D) membranes made up of inorganic bioactive glass fibers matrixed organic collagen structure. The 3D structure is arranged as a stacked-layer similar to the order of apatite and neotissue formation. Comparative studies on collagen, collagen with hollow and solid bioactive glass fibers evidenced that, collagen/hollow bioactive glass is mechanically robust, has optimal hydrophilicity, simultaneously promotes bioactivity and in situ forming drug delivery. The 3D membrane displays outstanding mechanical properties apropos to the bioactive glass fibers arrangement, with its Youngs modulus approaching the modulus of cortical bone. The in vitro cell culture studies with fibroblast cells (3T3) on the membranes display enhanced cell adhesion and proliferation with the cell alignment similar to anisotropic cell alignment found in the native bone extracellular matrix. The membranes also support 3D cell culturing and exhibits cell proliferation on the membrane surface, which extends the possibility of its bone tissue engineering application. The alkaline phosphatase assessment and alizarin red staining of osteoblast cells (MG63) depicted an enhanced osteogenic activity of the membranes. Notable Runx2, Col-Type-1 mRNA, osteocalcin, and osteonectin levels were found to be significantly increased in cells grown on the collagen/hollow bioactive glass membrane. This membrane also promotes vascularization in the chick chorioallantoic membrane model. The results altogether evidence this multifunctional 3D membrane could potentially be utilized for treatment of bone defects.

Quercetin as an Agent for Protecting the Bone: A Review of the Current Evidence

Quercetin is a flavonoid abundantly found in fruits and vegetables. It possesses a wide spectrum of biological activities, thus suggesting a role in disease prevention and health promotion. The present review aimed to uncover the bone-sparing effects of quercetin and its mechanism of action. Animal studies have found that the action of quercetin on bone is largely protective, with a small number of studies reporting negative outcomes. Quercetin was shown to inhibit RANKL-mediated osteoclastogenesis, osteoblast apoptosis, oxidative stress and inflammatory response while promoting osteogenesis, angiogenesis, antioxidant expression, adipocyte apoptosis and osteoclast apoptosis. The possible underlying mechanisms involved are regulation of Wnt, NF-κB, Nrf2, SMAD-dependent, and intrinsic and extrinsic apoptotic pathways. On the other hand, quercetin was shown to exert complex and competing actions on the MAPK signalling pathway to orchestrate bone metabolism, resulting in both stimulatory and inhibitory effects on bone in parallel. The overall interaction is believed to result in a positive effect on bone. Considering the important contributions of quercetin in regulating bone homeostasis, it may be considered an economical and promising agent for improving bone health. The documented preclinical findings await further validation from human clinical trials.

Intussusceptive angiogenesis as a key therapeutic target for cancer therapy

Deregulation of angiogenesis is a key reason for tumor growth and progression. Several anti-angiogenic drugs in clinical practice attempt to normalize abnormal tumor vasculature. Unfortunately, these drugs are ineffective due to the development of resistance in patients after drug holidays. A sizable literature suggests that resistance to these anti-angiogenic drugs occurs due to various compensatory mechanisms of tumor angiogenesis. Therefore, we describe different compensatory mechanisms of tumor angiogenesis, and explain why intussusceptive angiogenesis (IA), is a crucial mechanism of compensatory angiogenesis in tumors which resist anti-VEGF (vascular endothelial growth factor) therapies. IA is often overlooked due to the scarcity of experimental models. Therefore, we examine data from existing experimental models and our novel ex-ovo model of angiogenesis in chick embryos, and explain the important genes and signaling pathways driving IA. Using bio-informatic analyses of major genes regulating conventional sprouting angiogenesis (SA) and intussusceptive angiogenesis, we provide fresh insights on the 'angiogenic switch' which regulates the transition from SA to IA. Finally, we examine the interplay between molecules regulating SA, IA, and molecules known to promote tumor progression. Based on these analyses, we conclude that intussusceptive angiogenesis (IA) is a promising therapeutic target for developing effective anti-cancer treatment regimes.

The effects of morin on bone regeneration to accelerate healing in bone defects in mice

Restoring bone defects are the major challenge facing clinical trial therapy, particularly skull related problems. Morin, a naturally occurring compound, has pro-osteogenesis. This research focuses on assessing the role of morin for its pro-osteogenesis activities. We utilized in vivo and in vitro models to investigate the molecular-level mechanisms of morin's osteoblastic biological activity. The effectiveness of morin on pro-osteogenesis (100 mg/kg/day) was assessed by monitoring modifications in the bone histomorphometry score, the development of immature osteoblasts from mesenchymal stems cells and improvements in the expression of pro-osteogenic cytokines in skull defected (SD) mice. Quantitative-PCR, Western blot analysis, and immunofluorescence were studied to investigate the signaling pathways. Morin has a substantial in vivo pro-osteogenesis effect which can facilitate the development of osteoblasts, the production of osteoblast related marker genes, and in vitro protein markers for osteoblasts. From a molecular biology standpoint, morin contributes to the development of osteoblasts and stimulation of the Wnt pathway with the activation and translocation of β-catenin nuclei. Our findings from the study revealed that morin may be a beneficial substitute for helping regenerate bone defects.

Characterization and Stability of the Antimony-Quercetin Complex

Purpose: Quercetin is a flavonoid known for its therapeutic properties and for forming complexes. Although the antimony-quercetin (SbQ) complex has been produced before, no previous exploration of its characteristics has been published in literature. Thus, this study aimed to characterize this complex, assess its stability and investigate its complexation site through its antibacterial activity. Methods: The SbQ complex was synthetized using Sb(III) potassium tartrate trihydrate and quercetin anhydrous (1:1) (v/v) as a solution and dried using three methods: rotaevaporation, lyophilization and spray drying. The material, in solution, was analyzed by UV-vis and fluorimetry; and, in the powder, by X-ray diffraction (XRD), both scanning electronic and fluorescence microscopy and infrared spectroscopy (FT-IR). Antimicrobial activity was evaluated via broth microdilution. Results: UV-vis exhibited a shoulder peak at 291 nm indicating metal chelation at C-ring of quercetin and confirmed 1:1 stoichiometry. Spectrofluorimetry showed an increase of intensity with the complex formation with an emission band (525 nm). After drying, XRD and SEM indicated loss of crystallinity and a difference in shape and size of the complex compared to its precursors. FT-IR suggested by a shift of frequency of the carbonyl group (1661 cm-1) that the quercetin bond to antimony by the C-3, followed by positions C-5 and C-4 carbonyl, which has been confirmed by MIC through the structure-activity relationship of the antibacterial activity of quercetin. Conclusion: These results provided a characterization of SbQ complex with the confirmation of its binding site, working as a guide for future studies involving this complex.

Fabrication and Evaluation of 3D Printed Poly(l-lactide) Scaffold Functionalized with Quercetin-Polydopamine for Bone Tissue Engineering

Quercetin (Qu), a bioflavonoid, has been reported to positively affect bone metabolism. For the first time, Qu with different concentrations was utilized to functionalize 3D-printed poly(l-lactide) (PLLA) scaffold with the aid of a polydopamine (PDA) layer through a convenient and effective way in this study. Results revealed that the coexistence of PDA and Qu can capacitate the 3D-printed PLLA scaffold to possess rougher surface, as well as better hydrophilicity and compressive properties. The resulting PDA- and Qu-modified PLLA scaffolds (Qu/PD-PLLA) can sustainably release Qu to some extent, which is more beneficial to the proliferation and attachment of MC3T3-E1 cells, upregulating ALP activity and calcium nodules as well as promoting the expression of related osteogenic genes and proteins. More significantly, such a positive impact of the Qu on the cell affinity and osteogenic activity played in a dose-dependent manner. This study revealed the potential of the 3D-printed Qu/PD-PLLA scaffolds with a certain amount of Qu as bone-repair materials.

ESI-TOF MS analysis of complexes formed between quercetin and five metal ions in hot water and a study into their DNA cleavage activity

Quercetin is a flavonoid compound widely found in vegetables, fruits, and medicinal plants. It has carbonyl and phenolic hydroxyl groups in its structure that can easily form complexes with metal ions. In this study, we reacted quercetin in water at 95 °C with five metal trace elements commonly found in plants, namely calcium, magnesium, zinc, iron(III), and copper. Each supernatant was then examined by electrospray ionization-time-of-flight mass spectrometry (ESI-TOF MS). The results showed that quercetin can form complexes with Ca²⁺, Mg²⁺, Zn²⁺, and Cu²⁺ in ratios of 2:1, 3:1, and 3:2. Interestingly, after reaction with Fe³⁺ in water at 95 °C, not only can quercetin‑iron(III) complexes be formed in ratios of 2:1 and 3:1, but small amounts of quercetin‑iron(II) complexes can also be formed in the same ratios. Furthermore, DNA cleavage experiments showed that when acting alone, quercetin and Cu²⁺ have weak or no cleavage effects on DNA, but the complex formed after reaction in hot water cleaves DNA in a time- and concentration-dependent manner. These results indicate that complexes may form between quercetin and a variety of metal trace elements in a water decoction of plants, and that these metal complexes may be the material basis for the health-promoting and therapeutic effects of edible or medicinal plants.

Synthesis, Spectroscopic Study and Radical Scavenging Activity of Kaempferol Derivatives: Enhanced Water Solubility and Antioxidant Activity

Kaempferol (Kae) is a natural flavonoid with potent antioxidant activity, but its therapeutic use is limited by its low aqueous solubility. Here, a series of Kae derivatives were synthesized to improve Kae dissolution property in water and antioxidant activity. These compounds included sulfonated Kae (Kae-SO₃), gallium (Ga) complexes with Kae (Kae-Ga) and Kae-SO₃ (Kae-SO₃-Ga). The compound structures were characterized by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and thermal methods (TG/DSC). The results showed that a sulfonic group (-SO₃) was successfully tethered on the C3' of Kae to form Kae-SO₃. And in the metal complexation, 4-CO and 3-OH of the ligand participated in the coordination with Ga(III). The metal-to-ligand ratio 1:2 was suggested for both complexes. Interestingly, Kae-SO₃-Ga was obviously superior to other compounds in terms of overcoming the poor water-solubility of free Kae, and the solubility of Kae-SO₃-Ga was about 300-fold higher than that of Kae-Ga. Furthermore, the evaluation of antioxidant activities in vitro was carried out for Kae derivatives by using α,α-diphenyl-β-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) free radical scavenging. The results showed that Kae-SO₃-Ga was also optimal for scavenging free radicals in a dose-dependent manner. These data demonstrate that sulfonate kaempferol-gallium complex has a promising future as a potential antioxidant and as a potential therapeutic agent for further biomedical studies.

Models to investigate intussusceptive angiogenesis: A special note on CRISPR/Cas9 based system in zebrafish

Angiogenesis is a distinct process which follows sprouting angiogenesis (SA) and intussusceptive angiogenesis (IA) forming the basis for various physiological and pathological scenarios. Angiogenesis is a double edged sword exerting both desirable and discernible effects owing to the referred microenvironment. Therapeutic interventions to promote angiogenesis in regenerative medicine is essential to achieve functional syncytium of tissue constructs while, angiogenic inhibition is a key therapeutic target to suppress tumor growth. In the recent years, clustered regularly interspaced short palindromic repeats associated 9 (CRISPR-Cas9) based gene editing approaches have been gaining considerable attention in the field of biomedical research owing to its ease in tailoring targeted genome in living organisms. The Zebrafish model, with adequately high-throughput fitness, is a likely option for genome editing and angiogenesis research. In this review, we focus on the implication of Zebrafish as a model to study IA and furthermore enumerate CRISPR/Cas9 based genome editing in Zebrafish as a candidate for modeling different types of angiogenesis and support its candidature as a model organism.

Electronic Spectroscopies Combined with Quantum Chemistry Calculations: Study of the Interactions of 3-Hydroxyflavone with Copper Ions

The current study aims at obtaining a better understanding of the mechanisms involved in the complexation of copper ions by 3-hydroxyflavone (3HF), which is one of the most studied compounds of the flavonoid family. To achieve this goal, quantum chemistry calculations combined with electronic spectroscopies, including absorption, fluorescence emission, and excitation, have been used. The formation of successive complexes of stoichiometry (metal/ligand) 1:2, 1:1, and 3:2 has been highlighted. Even under acidic conditions (pH = 4.0), the α-hydroxy-keto function of the molecule presents a high complexing power with regard to copper ions, insofar as a stable complex of 1:2 stoichiometry is obtained with a large conditional stability constant (log β = 8.7). The formation of this predominant species induces a quenching of the dual fluorescence of 3HF, whereas the second complex of stoichiometry 1:1 presents a fluorescence emission.

Association of hypoxia inducible factor-1 alpha exon 12 mutation in diabetic patients with and without diabetic foot ulcer

Hypoxia inducible factor 1 alpha (HIF-1α) is a key regulator of the genes involved in the cellular response to hypoxia. This study aims to determine the HIF-1α gene polymorphism and its association with protein expression in diabetic subjects with and without diabetic foot ulcers (DFU). A total of 529 patients with T2DM (N = 185), DFU (N = 199) and Control (N = 145) were accounted for the study. PCR-RFLP experiment was carried out in order to find the allelic and genotypic comparison of HIF-1α gene in various groups of patients. There was a highly increased frequency of GA, RR value of 3.533(2.099-5.950) with p-value of 0.0001 on DFU patients when compared to that of control subjects with risk allele of GA, RR value of 1.756 (1.294-2.384) with p-value of 0.00001. Thus, we found that there was a significant association of HIF-1α polymorphism in exon 12 among DFU patients when compared to control groups. The circulatory HIF-1α protein expression study indicated a decreased expression in DFU levels when compared to T2DM and control. Overall, the study showed that there is an association of HIF-1α polymorphism (G1970A) in diabetes and DFU patients when compared to the healthy group.

Nitric oxide signaling regulates tumor-induced intussusceptive-like angiogenesis

Existing animal models for screening tumor angiogenic process have various setbacks that necessitate further investigations. In this study, we developed an ex-ovo egg yolk angiogenesis model to screen the angiogenic potency of tumor cells (HeLa and SiHa cell lines). The egg yolk angiogenesis assay was applied to study the nitric oxide (NO) influence on switching from sprouting angiogenesis (SA) to intussusceptive angiogenesis (IA) under tumor microenvironment. Morphological analysis and SA-like or IA-like markers expression were determined during the development of chicken chorioallantoic membrane (CAM) from day 5 to 13. Expression of Notch1, Notch2, EphrinB2, and Tie2 were considered as SA-like while TEM8, CALD1, CXCR4 and HOMX1 were followed as IA-like markers. The HeLa and SiHa cell lines embedded CAM showed an increase in micro and macro blood vessels and vascular size, junction and length which are the pivotal morphological parameters of angiogenesis. Further, the study revealed that HeLa is more aggressive than SiHa in inducing tumor angiogenesis. To determine the NO signaling implication in tumor milieu, NO donor (Spermine NONOate (SPNO)), NOS inhibitor (L-nitro-L-arginine-methyl ester (L-NAME) and VEGF inhibitor (Avastin) were administrated to chick embryo vascular bed with and without HeLa cells. The results demonstrated that HeLa cells promote IA through NO signaling, VEGF and eNOS and it was documented by angiogenic morphological parameters and SA-like or IA-like markers expression. Therefore, our study claims that ex-ovo egg yolk angiogenesis model could be used to study tumor angiogenesis and NO plays a key role in switching of IA under tumor microenvironment.