A novel nano-copper-bearing stainless steel with reduced Cu(2+) release only inducing transient foreign body reaction via affecting the activity of NF-κB and Caspase 3

Copper incorporated biomaterial-based technologies for multifunctional wound repair

The treatment of wounds is a worldwide challenge, and wound infection can affect the effectiveness of wound treatment and further increase the disease burden. Copper is an essential trace element that has been shown to have broad-spectrum antibacterial effects and to be involved in the inflammation, proliferation, and remodeling stages of wound healing. Compared to treatments such as bioactive factors and skin grafts, copper has the advantage of being low-cost and easily available, and has received a lot of attention in wound healing. Recently, biomaterials made by incorporating copper into bioactive glasses, polymeric scaffolds and hydrogels have been used to promote wound healing by the release of copper ions. In addition, copper-incorporated biomaterials with catalytic, photothermal, and photosensitive properties can also accelerate wound healing through antibacterial and wound microenvironment regulation. This review summarizes the antibacterial mechanisms of copper- incorporated biomaterials and their roles in wound healing, and discusses the current challenges. A comprehensive understanding of the role of copper in wounds will help to facilitate new preclinical and clinical studies, thus leading to the development of novel therapeutic tools.

Bioactive elements manipulate bone regeneration

While bone tissue is known for its inherent regenerative abilities, various pathological conditions and trauma can disrupt its meticulously regulated processes of bone formation and resorption. Bone tissue engineering aims to replicate the extracellular matrix of bone tissue as well as the sophisticated biochemical mechanisms crucial for effective regeneration. Traditionally, the field has relied on external agents like growth factors and pharmaceuticals to modulate these processes. Although efficacious in certain scenarios, this strategy is compromised by limitations such as safety issues and the transient nature of the compound release and half-life. Conversely, bioactive elements such as zinc (Zn), magnesium (Mg) and silicon (Si), have garnered increasing interest for their therapeutic benefits, superior stability, and reduced biotic risks. Moreover, these elements are often incorporated into biomaterials that function as multifaceted bioactive components, facilitating bone regeneration via release on-demand. By elucidating the mechanistic roles and therapeutic efficacy of the bioactive elements, this review aims to establish bioactive elements as a robust and clinically viable strategy for advanced bone regeneration.

Modulation of Macrophage Response by Copper and Magnesium Ions in Combination with Low Concentrations of Dexamethasone

Macrophages have been deemed crucial for correct tissue regeneration, which is a complex process with multiple overlapping phases, including inflammation. Previous studies have suggested that divalent ions are promising cues that can induce an anti-inflammatory response, since they are stable cues that can be released from biomaterials. However, their immunomodulatory potential is limited in a pro-inflammatory environment. Therefore, we investigated whether copper and magnesium ions combined with low concentrations of the anti-inflammatory drug, dexamethasone (dex), could have a synergistic effect in macrophage, with or without pro-inflammatory stimulus, in terms of morphology, metabolic activity and gene expression. Our results showed that the combination of copper and dex strongly decreased the expression of pro-inflammatory markers, while the combination with magnesium upregulated the expression of IL-10. Moreover, in the presence of a pro-inflammatory stimulus, the combination of copper and dex induced a strong TNF-α response, suggesting an impairment of the anti-inflammatory actions of dex. The combination of magnesium and dex in the presence of a pro-inflammatory stimulus did not promote any improvement in comparison to dex alone. The results obtained in this study could be relevant for tissue engineering applications and in the design of platforms with a dual release of divalent ions and small molecules.

Zinc alloy-based bone internal fixation screw with antibacterial and anti-osteolytic properties

There is no targeted effective treatment for patients undergoing internal fixation surgery/two-stage total joint revision surgery with a high risk of postoperative infection and osteolysis, while the rate of reoperation due to infection and osteolysis remains high. In this study, we report a pioneering application of implants made of biodegradable Zn–Ag alloy with active antibacterial and anti-osteolytic properties in three classical animal models, illustrating antibacterial, anti-osteolysis, and internal fixation for fractures. The antibacterial activity of the Zn–2Ag alloy was verified in a rat femur osteomyelitis prevention model, while the anti-osteolytic properties were evaluated using a mouse cranial osteolysis model. Moreover, the Zn–2Ag based screws showed similar performance in bone fracture fixation compared to the Ti–6Al–4V counterpart. The fracture healed completely after 3 months in the rabbit femoral condyle fracture model. Furthermore, the underlying antibacterial mechanism may include inhibition of biofilm formation, autolysis-related pathways, and antibiotic resistance pathways. Osseointegration mechanisms may include inhibition of osteoclast-associated protein expression, no effect on osteogenic protein expression, and no activation of related inflammatory protein expression. The empirical findings here reveal the great potential of Zn–Ag-based alloys for degradable biomaterials in internal fixation surgery/two-stage total joint revision surgery for patients with a high risk of postoperative infection and osteolysis.

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Zn–2Ag alloy is designed for orthopedic applications.

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Zn–2Ag alloy exhibit outstanding antibacterial properties in a rat femur osteomyelitis prevention model.

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Zn–2Ag alloy exhibit outstanding anti-osteolytic properties in a mouse cranial osteolysis model.

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Zn-2Ag based screws showed reliable performance in bone fracture fixation in the rabbit femoral condyle fracture model.

Copper-Containing Alloy as Immunoregulatory Material in Bone Regeneration via Mitochondrial Oxidative Stress

In the mammalian skeletal system, osteogenesis and angiogenesis are closely linked by type H vessels during bone regeneration and repair. Our previous studies confirmed the promotion of these processes by copper-containing metal (CCM) in vitro and in vivo. However, whether and how the coupling of angiogenesis and osteogenesis participates in the promotion of bone regeneration by CCM in vivo is unknown. In this study, M2a macrophages but not M2c macrophages were shown to be immunoregulated by CCM. A CCM, 316L−5Cu, was applied to drilling hole injuries of the tibia of C57/6 mice for comparison. We observed advanced formation of cortical bone and type H vessels beneath the new bone in the 316L−5Cu group 14 and 21 days postinjury. Moreover, the recruitment of CD206-positive M2a macrophages, which are regarded as the primary source of platelet-derived growth factor type BB (PDGF-BB), was significantly promoted at the injury site at days 14 and 21. Under the stimulation of CCM, mitochondria-derived reactive oxygen species were also found to be upregulated in CD206^hi M2a macrophages in vitro, and this upregulation was correlated with the expression of PDGF-BB. In conclusion, our results indicate that CCM promotes the evolution of callus through the generation of type H vessels during the process of bone repair by upregulating the expression of PDGF-BB derived from M2a macrophages.

In vitro study on cytocompatibility and osteogenesis ability of Ti-Cu alloy

Titanium implants easily suffer bacteria-related infections in clinic due to their inherent lack of self-protection ability. Therefore, a novel Ti-Cu alloy with good antibacterial activity has been developed as a new kind of implant material. This study focuses on a systematic evaluation of both cytocompatibility and osteogenesis activity of the Ti-Cu alloy in vitro. It was revealed that an addition of 5% Cu into pure Ti would not cause any negative effect on osteoblasts adhesion, proliferation and apoptosis cultured with Ti-Cu alloy. In addition, Ti-Cu alloy could significantly promote the osteogenic differentiation of MG 63 cells by upregulating the osteogenesis-related gene expressions including alkaline phosphatase (ALP), Collagen I (Colla I), osteopontin (OPN) and osteocalcin (OCN). These promising results suggest that the Ti-Cu alloy has great potential to be used as a multi-functional titanium implant for clinical applications.

Arsenic and/or copper caused inflammatory response via activation of inducible nitric oxide synthase pathway and triggered heat shock protein responses in testis tissues of chicken

The aim of this study is to investigate the effects of arsenic (As) and copper (Cu) on the inflammatory response, and the protective roles of heat shock proteins (Hsps) in chicken testes. Seventy-two 1-day-old male Hy-line chickens were treated with 30 mg/kg feed of arsenic trioxide (As₂O₃) and/or 300 mg/kg feed of copper sulfate (CuSO₄) for 4, 8, and 12 weeks. The histological changes, inducible nitric oxide synthase (iNOS) activity, and the expressions of Hsps and inflammatory cytokines were detected. The results showed that slight histology changes were obvious in the testis tissue exposure to treatment groups. The activity and the protein level of iNOS were increased compared to the control group. The mRNA levels of proinflammatory cytokines and inflammatory factors were increased as a whole. However, anti-inflammatory cytokines were inhibited. The mRNA and protein levels of Hsp60, Hsp70, and Hsp90 were upregulated. These results suggested that sub-chronic exposure to As and/or Cu induced testicular poisoning in chickens. Increased Hsps tried to protect chicken testis tissues from tissues damage caused by inflammation. In conclusion, testicular poisoning induced by As and/or Cu caused inflammatory response and heat shock protein response in chicken testis tissues.

Evaluation of promoting effect of a novel Cu-bearing metal stent on endothelialization process from in vitro and in vivo studies

Drug eluting stents (DES) have been extensively applied nowadays and reduce the incidence of in-stent restenosis (ISR) greatly as compared with bare metal stents (BMS). However, the development of DES is hindered by the risk of late stent thrombosis (LST) due to delayed re-endothelialization, while endothelialization is an important process related to ISR and LST after implantation. 316L is a traditional stent material without bioactivity and have a high risk of ISR. Cu is recognized for angiogenesis stimulation in these years. Hence a copper bearing 316L stainless steel (316L-Cu) was prepared and evaluated about its effect on endothelialization in this paper. Compared with traditional 316L, it was proved that 316L-Cu increased the proliferation of co-cultured human umbilical vein endothelial cells (HUVECs) at first day. Moreover, HUVECs stretched better on the surface of 316L-Cu. It also improved the expression of angiogenesis related genes and tube formation ability in vitro. 316L-Cu-BMS, DES and 316L-BMS were implanted in swine to evaluate the re-endothelialization ability in vivo. And 316L-Cu-BMS showed the best effect on endothelialization with good biosafety. Consequently, 316L-Cu is a kind of promising BMS material for coronary field.

Nano-copper-bearing stainless steel promotes fracture healing by accelerating the callus evolution process

Treatment for fractures requires internal fixation devices, which are mainly produced from stainless steel or titanium alloy without biological functions. Therefore, we developed a novel nano-copper-bearing stainless steel with nano-sized copper-precipitation (317L-Cu SS). Based on previous studies, this work explores the effect of 317L-Cu SS on fracture healing; that is, proliferation, osteogenic differentiation, osteogenesis-related gene expression, and lysyl oxidase activity of human bone mesenchymal stem cells were detected in vitro. Sprague–Dawley rats were used to build an animal fracture model, and fracture healing and callus evolution were investigated by radiology (X-ray and micro-CT), histology (H&E, Masson, and safranin O/fast green staining), and histomorphometry. Further, the Cu²⁺ content and Runx2 level in the callus were determined, and local mechanical test of the fracture was performed to assess the healing quality. Our results revealed that 317L-Cu SS did not affect the proliferation of human bone mesenchymal stem cells, but promoted osteogenic differentiation and the expression of osteogenesis-related genes. In addition, 317L-Cu SS upregulated the lysyl oxidase activity. The X-ray and micro-CT results showed that the callus evolution efficiency and fracture healing speed were superior for 317L-Cu SS. Histological staining displayed large amounts of fibrous tissues at 3 weeks, and cartilage and new bone at 6 weeks. Further, histomorphometric analysis indicated that the callus possessed higher osteogenic efficiency at 6 weeks, and a high Cu²⁺ content and increased Runx2 expression were observed in the callus for 317L-Cu SS. Besides, the mechanical strength of the fracture site was much better than that of the control group. Overall, we conclude that 317L-Cu SS possesses the ability to increase Cu²⁺ content and promote osteogenesis in the callus, which could accelerate the callus evolution process and bone formation to provide faster and better fracture healing.