Improving corrosion resistance of additively manufactured WE43 magnesium alloy by high temperature oxidation for biodegradable applications

Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.

Cistanche Deserticola for Regulation of Bone Metabolism:Therapeutic Potential and Molecular Mechanisms on Postmenopausal Osteoporosis

Osteoporosis is a generalized disease of bone that leads to a loss of bone density and bone mass,destruction of bone microstructure,increased brittleness and therefore fracture.At present,the main treatment of Western medicine is drug therapy such as bisphosphonates,calcitriol,vitamin D,etc.However,long-term use of these drugs may bring some adverse reactions.Chinese herbal medicine Cistanche deserticola could regulate bone metabolism by promoting osteoblast activity and inhibiting osteoclast activity with low toxicity and adverse reactions.Therefore,Cistanche deserticola has attracted increasing attention for its efficacy in the prevention and treatment of osteoporosis in recent years.Here we present a literature review of the molecular pathways involved in osteoporosis and the effects of Cistanche deserticola on bone metabolism.Our objective is to clarify the mechanism of Cistanche deserticola in the treatment of osteoporosis.

Simvastatin-hydroxyapatite coatings prevent biofilm formation and improve bone formation in implant-associated infections

Implant-associated infections(IAIs)caused by biofilm formation are the most devastating complications of orthopedic surgery.Statins have been commonly and safely used drugs for hypercholesterolemia for many years.Here,we report that simvastatin-hydroxyapatite-coated titanium alloy prevents biofilm-associated infections.The antibacterial properties of simvastatin against Staphylococcus aureus and Staphylococcus epidermidis biofilms in vitro was confirmed by crystal violet staining and live-dead bacterial staining.We developed a simvastatin-and hydroxyapatite(Sim-HA)-coated titanium alloy via electrochemical deposition.Sim-HA coatings inhibited Staphylococcus aureus biofilm formation and improved the biocompatibility of the titanium alloy.Sim-HA coatings effectively prevented Staphylococcus aureus IAI in rat femurs,as confirmed by radiological assessment and histological examination.The antibacterial effects of the Sim-HA coatings were attributed to their inhibitory effects on biofilm formation,as verified by scanning electron microscopic observations and bacterial spread plate analysis.In addition,the Sim-HA coatings enhanced osteogenesis and osteointegration,as verified by micro-CT,histological evaluation,and biomechanical pull-out tests.In summary,Sim-HA coatings are promising implant materials for protection against biofilm-associated infections.

The effect of pore size on the mechanical properties, biodegradation and osteogenic effects of additively manufactured magnesium scaffolds after high temperature oxidation: An in vitro and in vivo study

The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 μm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.

Lumbar spine localisation method based on feature fusion

To eliminate unnecessary background information,such as soft tissues in original CT images and the adverse impact of the similarity of adjacent spines on lumbar image segmentation and surgical path planning,a two‐stage approach for localising lumbar segments is proposed.First,based on the multi‐scale feature fusion technology,a non‐linear regression method is used to achieve accurate localisation of the overall spatial region of the lumbar spine,effectively eliminating useless background information,such as soft tissues.In the second stage,we directly realised the precise positioning of each segment in the lumbar spine space region based on the non‐linear regression method,thus effectively eliminating the interference caused by the adjacent spine.The 3D Intersection over Union(3D_IOU)is used as the main evaluation indicator for the positioning accuracy.On an open dataset,3D_IOU values of 0.8339�0.0990 and 0.8559�0.0332 in the first and second stages,respectively is achieved.In addition,the average time required for the proposed method in the two stages is 0.3274 and 0.2105 s respectively.Therefore,the proposed method performs very well in terms of both pre-cision and speed and can effectively improve the accuracy of lumbar image segmentation and the effect of surgical path planning.

Crosstalk between bone and other organs

Bone has long been considered as a silent organ that provides a reservoir of calcium and phosphorus,traditionally.Recently,further study of bone has revealed additional functions as an endocrine organ connecting systemic organs of the whole body.Communication between bone and other organs participates in most physiological and pathological events and is responsible for the maintenance of homeostasis.Here,we present an overview of the crosstalk between bone and other organs.Furthermore,we describe the factors mediating the cross-talk and review the mechanisms in the development of potential associated diseases.These connections shed new light on the pathogenesis of systemic diseases and provide novel potential targets for the treatment of systemic diseases.

Biodegradable magnesium alloy WE43 porous scaffolds fabricated by laser powder bed fusion for orthopedic applications:Process optimization,in vitro and in vivo investigation

Laser powder bed fusion(L-PBF)of magnesium(Mg)alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects.However,one of the key technical difficulties lies in the poor L-PBF process performance of Mg,contributed by the high susceptibility to oxidation,vaporization,thermal expansion,and powder attachment etc.This work investigated the influence of L-PBF energy input and scanning strategy on the formation quality of porous scaffolds by using WE43 powder,and characterized the microstructure,mechanical properties,biocompatibility,biodegradation and osteogenic effect of the as-built WE43 porous scaffolds.With the customized energy input and scanning strategy,the relative density of struts reached over 99.5%,and the geometrical error between the designed and the fabricated porosity declined to below 10%.Massive secondary phases including intermetallic precipitates and oxides were observed.The compressive strength(4.37-23.49 MPa)and elastic modulus(154.40-873.02 MPa)were comparable to those of cancellous bone.Good biocompatibility was observed by in vitro cell viability and in vivo implantation.The biodegradation of as-built porous scaffolds promoted the osteogenic effect,but the structural integrity devastated after 12 h by the immersion tests in Hank’s solution and after 4 weeks by the implantation in rabbits’femur,indicating an excessively rapid degradation rate.

Practical strategy to construct anti-osteosarcoma bone substitutes by loading cisplatin into 3D-printed titanium alloy implants using a thermosensitive hydrogel

Surgical resection and perioperative adjuvant chemotherapy-based therapies have improved the prognosis of patients with osteosarcoma;however,intraoperative bone defects,local tumour recurrence,and chemotherapy-induced adverse effects still affect the quality of life of patients.Emerging 3D-printed titanium alloy(Ti6Al4V)implants have advantages over traditional implants in bone repair,including lower elastic modulus,lower stiffness,better bone conduction,more bone in-growth,stronger mechanical interlocking,and lager drug-loading capacity by their inherent porous structure.Here,cisplatin,a clinical first-line anti-osteosarcoma drug,was loaded into Ti6Al4V implants,within a PLGA-PEG-PLGA thermo-sensitive hydrogel,to construct bone substitutes with both anti-osteosarcoma and bone-repair functions.The optimal concentrations of cisplatin(0.8 and 1.6 mg/mL)were first determined in vitro.Thereafter,the anti-tumour effect and biosafety of the cisplatin/hydrogel-loaded implants,as well as their bone-repair potential were evaluated in vivo in tumour-bearing mouse,and bone defect rabbit models,respectively.The loading of cisplatin reduced tumour volume by more than two-thirds(from 641.1 to 201.4 mm3)with negligible organ damage,achieving better anti-tumour effects while avoiding the adverse effects of systemic cisplatin delivery.Although bone repair was hindered by cisplatin loading at 4 weeks,no difference was observed at 8 weeks in the context of implants with versus without cisplatin,indicating acceptable long-term stability of all implants(with 8.48%-10.04%bone in-growth and 16.94%-20.53%osseointegration).Overall,cisplatin/hydrogel-loaded 3D-printed Ti6Al4V implants are safe and effective for treating osteosarcoma-caused bone defects,and should be considered for clinical use.

High efficacy of tetra-PEG hydrogel sealants for sutureless dural closure

Advances in meticulous dural closure technique remain a great challenge for watertight dural closure in the aged society,because the cerebrospinal fluid(CSF)leakage after spinal surgery is often accompanied with the disgusting wound infection,meningitis and pseudomeningocele.Here,a tetra-poly(ethylene glycol)(PEG)-based hydrogel sealant is developed with collective advantages of facile operation,high safety,quick set time,easy injectability,favorable mechanical strength and powerful tissue adhesion for effective sutureless dural closure during the surgery procedure.Impressively,this tetra-PEG sealant can instantaneously adhere to the irregular tissue surfaces even in a liquid environment,and effectively prevent or block off the intraoperative CSF leakage for sutureless dural closure and dura regeneration.Together,this sutureless tetra-PEG adhesive can be utilized as a very promising alternative for high-efficient watertight dural closure of the clinical patients who incidentally or deliberately undergo the durotomy during the spinal surgery.

Metabolic syndrome and osteoarthritis:Possible mechanisms and management strategies

Osteoarthritis(OA)is mostly considered not a simple cartilage degradation,but a whole joint disorder,with all the joint components involved,such as subchondral bone,synovium and adhesive ligaments/muscles.Moreover,metabolic syndrome(MetS)and OA are both share a low-grade inflammatory state,and an increasing number of studies have found correlations between metabolic syndrome(MetS)and OA.Their correlations imply that OA might not be a simple joint disorder,but also be affected by MetS.MetS is characterized by a series of risk factors,including hypertension,hyperglycaemia,dyslipidaemia,obesity.However,the findings of some studies didn’t agree with the above correlation between MetS and OA,partly due to complexity of MetS.This review summarizes the correlation between different factors of MetS and OA and the strategic methods for managing MetSrelated OA.Possible mechanisms by which each MetS factor is involved in OA onset and progression are reviewed.This work might help better understand OA and inspire new ideas for preventing and treating OA.