Degradation protection and enhanced biocompatibility of Mg alloys pretreated with plasma proteins.

After implantation of the Mg alloy in the human body, the adsorption of plasma protein on surface will cause a series of cell reactions and affect the degradation of Mg alloys. Herein, in vitro biological reactions of the ZK60 and AZ31 Mg alloys are analyzed in plasma protein environment. Combined with mass spectrometry analysis of the type of adsorbed proteins, it is shown that proteins such as fibrinogen, vitronectin, fibronectin, and prothrombin are prone to get adsorbed on the surface of the alloys than other proteins, leading to the promotion of MG63 cell adhesion and proliferation. The effect of selected proteins (fibrinogen, fibronectin, and prothrombin) on degradation of ZK60 and AZ31 Mg alloys is investigated using immersion tests. The degradation of AZ31 Mg alloy is significantly restrained with the presence of proteins. This is due to the protein adsorption effect on the sample surface. The molecular dynamics simulation results indicate that both fibrinogen and fibronectin tend to adsorb onto the AZ31 rather than ZK60, forming a stable protein layer on the AZ31 Mg alloy retarding the degradation of the samples. As to ZK60 alloy, the addition of protein inhibits the degradation in the short term, however, the degradation increases after a long time of immersion. This phenomenon is particularly pronounced in fibronectin solution.

Festuca coelestis Increases Drought Tolerance and Nitrogen Use via Nutrient Supply-Demand Relationship on the Qinghai-Tibet Plateau.

Drought and nutrient deficiency pose great challenges to the successful establishment of native plants on the Qinghai-Tibet Plateau. The dominant factors and strategies that affect the adaptation of alpine herbs to dry and nutrient-deficient environments remain unclear. Three water gradients were established using two-factor controlled experiments: low water (WL), medium water (WM), and high water (WH). The field water-holding capacities were 35%, 55%, and 75%, respectively. Nitrogen fertilizer (N) was applied at four levels: control (CK), low (FL), medium (FM), and high (FH) at 0, 110, 330, and 540 mg/kg, respectively. The results revealed that N was the main limiting factor, rather than phosphorous (P), in Festuca coelestis under drought stress. Under water shortage conditions, F. coelestis accumulated more proline and non-structural carbohydrates, especially in the aboveground parts of the leaves and stems; however, the root diameter and aboveground nitrogen use efficiency were reduced. Appropriate N addition could mitigate the adverse effects by increasing the release of N, P, and enzyme activity in the bulk soil and rhizosphere to balance their ratio, and was mainly transferred to the aboveground parts, which optimized the supply uptake relationship. The effects of water and fertilizer on the physiological adaptability and nutrient utilization of F. coelestis were verified using structural equation modeling. Based on their different sensitivities to water and nitrogen, the WHFM treatment was more suitable for F. coelestis establishment. Our results demonstrated that the disproportionate nutrient supply ability and preferential supply aboveground compared to below ground were the main factors influencing F. coelestis seedling establishment under drought conditions. This study provides evidence for a better understanding of herbaceous plants living in high mountain regions and offers important information for reducing the risk of ecological restoration failure in similar alpine regions.

Enhanced anti-corrosion and biocompatibility of a functionalized layer formed on ZK60 Mg alloy via hydroxyl (OH-) ion implantation.

Magnesium and its alloys have piqued the interest of researchers due to their promising mechanical properties and biocompatibility. Moreover, the excessively fast corrosion rate of Mg alloys impedes their development in biomedical fields. Inspired by conventional ion implantation, a less-toxic functional group (hydroxyl) is used as the ion source to bombard the ZK60 Mg alloy surface to form a functionalized oxide layer. The surface characterization, corrosion resistance, and biocompatibility are systematically investigated before and after hydroxyl ion implantation. A smoother surface mainly constituted of hydroxide/oxide is formed for the treated samples. The formed functionalized layer significantly improves the corrosion resistance of the ZK60 Mg alloy substrate and the proliferation of MC3T3-E1 cells, as demonstrated by electrochemical, immersion, and in vitro cytocompatibility tests. In summary, less-toxic functional ion implantation can be an effective strategy for preventing corrosion of Mg alloy implants and promoting their biocompatibility.

Patterns and drivers of the belowground bud bank in alpine grasslands on the Qinghai-Tibet Plateau.

Introduction: In grassland ecosystems dominated by asexual plants, the maintenance, renewal, and resistance of plant populations to disturbance are more dependent on the belowground bud bank (BBB). However, the response of the BBB to environmental factors in the alpine grassland of the Qinghai-Tibet Plateau (QTP) is still unknown. Methods: Therefore, a transect survey was conducted to measure the size and scale of BBB and 21 factors in the alpine grassland of the QTP. In addition, the critical driving factors of BBB were screened by boost regression tree analysis, and a structural equation model (SEM) was employed to express the path coefficients of the key factors on the BBB size. Results: The results showed that BBB size had no significant geographical pattern in the QTP, and the BBB size was mainly accounted for by soil leucine aminopeptidase (LAP, 17.32%), followed by Margalef and Shannon -Wiener indices of plants (12.63% and 9.24%, respectively), and precipitation (9.23%). SEM further indicated significant positive effects of plant diversity (scored at 0.296) and precipitation (scored at 0.180) on BBB size, and a significant negative effect of LAP (scored at 0.280) on BBB size. Discussion: Generally, the findings allow for better understanding of the regulated mechanisms of BBB size and the importance of the role of bud bank in the restoration of the grassland ecosystem.

Vegetation distribution along mountain environmental gradient predicts shifts in plant community response to climate change in alpine meadow on the Tibetan Plateau.

Plants are particularly sensitive to climate change in alpine ecosystem of the Tibetan Plateau. The various mountain micro-climates provide a natural gradient for space-for-time substitution research that plant responses to climate change. In this study, we surveyed the plant community in term of species composition, diversity and biomass across 189 sites on a hill of the Tibetan Plateau and analysed the individual and integrated effects of soil temperature and moisture on the plant community. The results showed that, at the quadrat scale, there were decrease in richness of 1.08 species for every 1 °C increase in soil temperature and 3.56 species for every 10% decrease in soil moisture. The integrated effects of increasing soil temperature and decreasing moisture are expected to lead to a rapid decrease in species richness. Biomass had no significant correlation with soil temperature but significantly decreased with soil moisture decreasing (p < 0.01). Biomass would decrease when soil moisture was below 20%, no matter how the change of soil temperature. We also found that gramineae and perennial forbs were sensitive to climate change. With soil temperature increased, the proportion of gramineae increased, whereas the proportion of perennial forbs decreased. The integrated effects of soil temperature increasing and moisture decreasing caused a shift from sedge-controlled to gramineae-controlled communities in alpine meadow. This study not only enhances our understanding of mountain plant community dynamics under climate change, but also predicts the shift of vegetation response to climate change on high-elevation alpine meadow.