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Critical-size bone defects are an important problem in clinical practice, which usually occurs in severe trauma, or tumor resection, and cannot heal completely and autonomously. Implantation of grafts is often required to promote the regeneration of critical-size bone defects. Metal ions play an important role in human health, as they affect the body's metabolism and the tissue function. Strontium ions (Sr 2+ ) can promote osteogenesis and angiogenesis. Herein, we prepared nano-hydroxyapatite (nHA)/chitosan (CS) composite microspheres with a uniform particle size distribution and an extracellular matrix-like nanofiber structure using microfluidic technology and direct alkali-induced gelation. Strontium ions were stably added into the microspheres by using polydopamine (PDA) to chelate metal ions forming a bone repair material (nHA/CS@PDA-Sr) with good bioactivity. The coordination reaction of PDA can effectively control the release of strontium ions and avoid the negative effects caused by the high strontium concentration. Our in vitro experiments showed that the composite microspheres had good biocompatibility and that the PDA coating promotes cell adhesion. The slow release of strontium ions can effectively promote mesenchymal stem cells osteogenic differentiation and the vascularization of endothelial cells. In addition, we injected composite microspheres into cranial defects of rats to evaluate osseointegration in vivo. The results showed that nHA/CS@PDA-Sr could effectively promote bone regeneration in the defect area. This study demonstrates that composite microspheres stimulate bone repair providing a promising way for bone-defect regeneration.

Determination of strontium ions (Sr 2+ ) is crucial with regard to human health and environmental protection. In this work, an electrochemical aptasensor was designed using carboxylated graphene oxide (CGO)-modified carbon paste electrode (CGO/CPE) for ultrasensitive determination of Sr 2+ ions. The electrochemical determination was accomplished with employing the constructed G-quadruplex (G4) aptamer at the surface of aptasensor in presence of carmoisine (CA) as an electrochemical label. Moreover, NH 2 -functionalized aptamer was immobilized onto CGO/CPE via carboxylic group. Hence, differential pulse voltammetry was applied for detection of any possible signal changes of CA on the aptasensor surface. The reduction peak currents of CA in the absence and presence of Sr 2+ in solution were different and this difference was linearly dependent to the concentration of Sr 2+ in solution. The analytical results revealed that our novel aptasensor showed two appropriate linear ranges (0.1-8.0 pM and 3.0-20.0 nM) versus to Sr 2+ ion concentrations with the limit of detection of 0.06 pM (S/N = 3). Excellent stability, selectivity and reproducibility were achieved with this new electrochemical aptasensor. Additionally, the aptasensor showed good achievements in analysis of Sr 2+ in aqueous and urine real samples, which making this proposed method a promising candidate for electrochemical detection of Sr 2+ in real samples., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Myofibrillar proteins (MPs) and the quality of meat strongly depend on the properties of MP gels, which in turn depend on several parameters that include the thermal history and the concentration of metal ions. Strontium element (Sr) widely exists in mineral water and is found as strontium ions (Sr 2+ ), which is an essential trace element for humans. This study investigated the effects of trace Sr 2+ on the structure-function relationship of mutton MPs, as well as their gels with water. Trace concentrations of Sr 2+ were found to significantly alter the conformation of the MPs. An increase in Sr 2+ concentration was associated with a reduction in the tightness and strength of the gel and a significant increase in its water-holding capacity As compared to the untreated control sample, the solubility, particle size, and the magnitude of the Zeta potential of the gels increased by 13.03 %, 12.62 %, and 19.73 %, respectively, whereas the water retention capacity and the gel strength increased by 23.13 % and 21.90 %, at a Sr 2+ concentration of 5.0 mg/L. Molecular docking predicted an increase in ionic bonds and disulfide bonds because Sr 2+ had a strong interaction with hydrophilic amino acids and acidic amino acids. The analysis of molecular forces further verified the significant facilitation of interactions between MP molecules with the induction of Sr 2+ . As compare to the untreated control group, the ionic and disulfide bonds increased by 141.17 % and 66.94 %, when treated with 5.0 mg/L Sr 2+ . These changes were likely due to the enhancement of protein-protein interactions caused by Sr 2+ , which could induce MP molecules to properly unfold and aggregate in gel formation. The results could provide a basis for improving the texture and the quality of meat and meat products., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

An injectable delivery platform for promoting delayed bone healing has been developed by combining a thermosensitive polyurethane-based hydrogel with strontium-substituted mesoporous bioactive glasses (MBG_Sr) for the long-term and localized co-delivery of pro-osteogenic Sr 2+ ions and an osteogenesis-enhancing molecule, N -Acetylcysteine (NAC). The incorporation of MBG_Sr microparticles, with a final concentration of 20 mg/mL, did not alter the overall properties of the thermosensitive hydrogel, in terms of sol-to-gel transition at a physiological-like temperature, gelation time, injectability and stability in aqueous environment at 37 °C. In particular, the hydrogel formulations (15% w/v polymer concentration) showed fast gelation in physiological conditions (1 mL underwent complete sol-to-gel transition within 3-5 min at 37 °C) and injectability in a wide range of temperatures (5-37 °C) through different needles (inner diameter in the range 0.4-1.6 mm). In addition, the MBG_Sr embedded into the hydrogel retained their full biocompatibility, and the released concentration of Sr 2+ ions were effective in promoting the overexpression of pro-osteogenic genes from SAOS2 osteoblast-like cells. Finally, when incorporated into the hydrogel, the MBG_Sr loaded with NAC maintained their release properties, showing a sustained ion/drug co-delivery along 7 days, at variance with the MBG particles as such, showing a strong burst release in the first hours of soaking.

Poly(lactic-co-glycolic acid) (PLGA)-based porous structures have a widespread application in bone defects. To solve its flaws in the bone application, hydroxyapatite (HA) is often introduced into PLGA-based systems, and ion doping endows HA with more biological activity. In osteoporotic bone defects, the decreased activity of osteoblasts and the hyperactive osteoclasts results in slow bone repair. Strontium (Sr) can promote bone regeneration and inhibit bone resorption and has been used in the treatment of osteoporosis. Magnesium (Mg) cannot only enhance the regeneration of bone tissue but also vessels. In this study,the aim is to fabricate a multifunctional porous structure that can promote osteogenesis, and angiogenesis and inhibit osteoclasts for repairing osteoporotic bone defects. PLGA cage-like structures loaded with Sr- and Mg-doped HA (Sr/Mg@HA/PLGA-CAS) are prepared; they have large pores, suitable hydrophilicity, and can continuously release Mg 2+ and Sr 2+ , which facilitate cell adhesion and growth. The results show that Sr/Mg@HA/PLGA-CAS can motivate the osteogenic activity of osteoblast precursor cells and angiogenic ability of endothelial cells, and suppress osteoclast differentiation in vitro. This study indicates that Sr/Mg@HA/PLGA-CAS can assist osteogenesis, and angiogenesis while restraining osteoclast differentiation, which may have a potential application value in osteoporotic bone defects., (© 2022 Wiley-VCH GmbH.)

Autogenous healing of osteoporotic fractures is challenging, as the regenerative capacity of bone tissues is impaired by estrogen reduction and existed pro-inflammatory cytokines. In this study, a biofunctional ginsenoside Rg1 and strontium-containing mineral (SrHPO 4 , SrP)-incorporated biodegradable silk fibroin-gelatin (SG) scaffold (Rg1/SrP/SG) was developed to stimulate the osteoporotic bone repair. The incorporation of 15 wt% SrP significantly enhanced the mechanical strength, stimulated the osteogenic differentiation of mouse bone marrow mesenchymal stem cells, and suppressed the osteoclastogenesis of RAW264.7 in a concentration-related manner. The loading of Rg1 in SG and 15SrP/SG scaffolds obviously promoted the angiogenesis of human umbilical vein endothelial cells via activating the expression of vascular endothelial growth factor and basic fibroblast growth factor genes and proteins. The bioactive strontium ions (Sr 2+ ) and Rg1 released from the scaffolds together mediated lipopolysaccharide-treated macrophages polarizing into M2 type. They downregulated the expression of inflammatory-related genes (interleukin (IL)-1β, tumor necrosis factor α, and IL-6) and stimulated the expression of genes related to anti-inflammation (Arginase and IL-10) as well as bone repair (BMP-2 and PDGF-BB) in the macrophages. The in vivo results also displayed that SrP and Rg1 significantly promoted the bone repair effect of SG scaffolds in osteoporotic critical-sized calvarial defects. Besides, the degradation rate of the scaffolds was close to the bone regeneration rate. Therefore, the simultaneous addition of SrP and Rg1 is a promising way for facilitating the osteoporotic bone repair activity of SG scaffolds via promoting the osteogenesis and angiogenesis, as well as inhibiting the osteoclastogenesis and inflammation., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)

The onset of scaling in oil pipelines can halt or drastically reduce oil production, causing huge financial losses and delays. Current methods used to monitor scaling can take weeks, while the scaling process only takes few hours. The proposed sensor is designed for online monitoring of strontium ions concentration in seawater as an early scaling indicator. The sensor operates in the GHz range by probing the shift in the resonance frequency due to changes in the ionic concentrations of the medium. The results show selective sensitivity to changes in the strontium ions concentration even in the presence of many other ions found in seawater. The measured sensitivity is found to be stable and linear with a detection level of better than 0.08% (0.042 mol/L) of strontium ions in seawater. This work demonstrates a robust GHz sensor for strontium sulfate scale monitoring and early detection, which could be used in the oil industry to prevent huge production losses. These results could also be extended further to target the monitoring of other ions in different industrial sectors.

Bacillus pumilus SWU7-1 was isolated from strontium ion (Sr(II))-uncontaminated soil, its biosorption potential was evaluated, and the effect of γ-ray radiation treatment on its biosorption was discussed. Domesticated under Sr(II) stress promoted the biosorption ability of B. pumilus to Sr(II), and the biosorption efficiency increased from 46.09% to 94.69%. At a lower initial concentration, the living bacteria had the ability to resist the biosorption of Sr(II). The optimal initial concentration range was 54-130 mg/L. The biosorption profile was better matched by Langmuir than Freundlich model, showing that the biosorption process of Sr(II) by the experimental strain was closer to the surface adsorption. According to Langmuir model, the maximum biosorption capacity of B. pumilus on Sr (II) was 299.4 mg/g. During the bacterial growth in the biosorption process, the changes in biosorption capacity and efficiency can be divided into two phases, and a pseudo-second-order model is followed in each phase. There was no significant difference in the biosorption efficiency of bacteria with different culture time after γ-ray radiation, and all of them were above 90%, which showed that B. pumilus had significant radiation resistance under experimental conditions. This study emphasized the potential application of B. pumilus in the treatment of radioactive Sr(II) pollution by biosorption., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The sorption removal of radionuclides Sr 2+ using a freestanding functional membrane is an interesting and significant research area in the remediation of radioactive wastes. Herein, a novel self-assembled membrane consisting of metal-organic framework (MOF) nanobelts and graphene oxides (GOs) are synthesized through a simple and facile filtration method. The membrane possesses a unique interwove morphology as evidenced from SEM images. Batch experiments suggest that the GO/Ni-MOF composite membrane could remove Sr 2+ ions from aqueous solutions and the Sr 2+ adsorption capacity and efficiency of the GO/Ni-MOF composite membrane is relevant to the MOF content in the composite. Thus, the dominant interaction mechanism was interface or surface complexation, electrostatic interaction as well as ion substitution. The maximum effective sorption of Sr 2+ over GO/Ni-MOF membrane is 32.99% with 2 mg composite membrane containing a high content of Ni-MOF at 299 K in 100 mg/L Sr 2+ aqueous solution. The FT-IR and XPS results suggest that the synergistic effect between GO and Ni-MOF is determinant in the sorption Sr 2+ process. The GO/Ni-MOF composite membrane is demonstrated to have the advantages of efficient removal of Sr 2+ , low cost and simple synthesis route, which is promising in the elimination of radionuclide contamination., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2020 The Author(s).)

Introducing new generations of injectable bioactive types of cement that fulfill excellent injectability, rapid self-setting, high bioactivity, proper biodegradability, and fast therapeutic ion-releasing capability is highly demanded for tooth and bone regeneration. Here, we announce therapeutic fast ion-releasing nanobiocements (NBCs) based on sol-gel-processed calcium silicate mesoporous nanobioactive glass with or without strontium (NBC, Sr-free and Sr-NBC, Sr-doped). The stimulating role of Sr ions in odontogenesis of stem cells derived from dental pulp (DPSCs) and in in vivo dentin formation has been investigated. The nanobiocement was formulated through the mixing of bioactive glass nanopowder with a phosphate-buffered saline (P/L = 0.5 g/mL) to form a soft cement paste that hardens within 5-10 min in the ambient environment. The self-setting originated from a setting reaction involving the deposition of hydroxyapatite as evidenced from X-ray diffraction. Both nanobiocements showed the rapid release of therapeutic ions with biologically effective doses, including strontium (Sr), calcium (Ca), or silicon (Si). In vitro cell cultures with DPSCs showed excellent biocompatibility and high odontogenic potential, especially from Sr-NBC. In an in vivo study, Sr-NBC showed more new dentin formation compared to that of NBC, revealed by two different animal models (odontogenesis in subcutaneous and natural tooth environment). Also, NBCs showed high loading capacities of simvastatin used as a model drug. Taken together, Sr-NBC could be considered as a multifunctional nanobiocement with high bioactivity, excellent biodegradability, fast therapeutic ion release, and high drug loading capability, which potentiates its application in dentin-pulp complex regeneration therapy.

The proper handling of low-level radioactive waste is crucial to promote the sustainable development of nuclear power. Research into the mechanism for interactions between bacterium and radionuclides is the starting point for achieving successful remediation of radionuclides with microorganisms. Using Sr(II) as a simulation radionuclide and the mixed microorganisms of Saccharomyces cerevisiae and Bacillus subtilis as the biological adsorbent, this study investigates behavior at the interface between Sr(II) and the microorganisms as well as the mechanisms governing that behavior. The results show that the optimal ratio of mixed microorganisms is S. cerevisiae 2.0 g L -1 to B. subtilis 0.05 g L -1 , and the optimal pH is about 6.3. Sr(II) biosorption onto the mixed microorganisms is spontaneous and endothermic in nature. The kinetics and the equilibrium isotherm data of the biosorption process can be described with pseudo-second-order equation and the Langmuir isotherm equation, respectively. The key interaction between the biological adsorbent and Sr(II) involves shared electronic pairs arising from chemical reactions via bond complexation or electronic exchange, and spectral and energy spectrum analysis show that functional groups (e.g., hydroxyl, carboxyl, amino, amide) at the interface between the radionuclide and the mixed microorganisms are the main active sites of the interface reactions.

Zirconium tungesto-vanadate cation exchange material was successfully architectured at open ended nanotubes morphological structure in the presence of polyvinyl alcohol as a stabilizing agent using microwave route. The ion exchange capacity (IEC) of the material was recorded as 4.8 meq/g of about 640 m(2)/g for a specific surface area. The x-ray diffraction pattern of the material implies its crystallinity. Both scanning and transmission electron microscopes identified the average aspect ratio of the architectured nanotubes as 6.5 and its hollow structure. The material posed 96.4 % cadmium ion decontamination within 90 min compared with 84 % strontium decontamination at the same time.