Mussel-Inspired Self-Healing Coatings Based on Polydopamine-Coated Nanocontainers for Corrosion Protection

The mussel-inspired properties of dopamine have attracted immense scientific interest for surface modification of nanoparticles due to the high potential of dopamine functional groups to increase the adhesion of nanoparticles to flat surfaces. Here, we report for the first time a novel type of inhibitor-loaded nanocontainer using polydopamine (PDA) as a pH-sensitive gatekeeper for mesoporous silica nanoparticles (MSNs). The encapsulated inhibitor (benzotriazole) was loaded into MSNs at neutral pH, demonstrating fast release in an acidic environment. The self-healing effect of water-borne alkyd coatings doped with nanocontainers was achieved by both on-demand release of benzotriazole during the corrosion process and formation of the complexes between the dopamine functional groups and iron oxides, thus providing dual self-healing protection for the mild steel substrate. The coatings were characterized by electrochemical impedance spectroscopy, visual observations, and confocal Raman microscopy. In all cases, the coatings with embedded benzotriazole-loaded MSNs with PDA-decorated outer surfaces demonstrated superior self-healing effects on the damaged areas. We anticipate that dopamine-based multifunctional gatekeepers can find application potential not only in intelligent self-healing anticorrosive coatings but also in drug delivery, antimicrobial protection, and other fields

Phytolith-Occluded Carbon Storages in Forest Litter Layers in Southern China: Implications for Evaluation of Long-Term Forest Carbon Budget

Phytolith-occluded carbon (PhytOC) can be preserved in soils or sediments for thousands of years and might be a promising potential mechanism for long-term terrestrial carbon (C) sequestration. As the principal pathway for the return of organic matters to soils, the forest litter layers make a considerable contribution to terrestrial C sequestration. Although previous studies have estimated the phytolith production fluxes in the above-ground vegetations of various terrestrial ecosystems, the storages of phytoliths and PhytOC in litter layers have not been thoroughly investigated, especially in forest ecosystems. Using analytical data of silica, phytoliths, return fluxes and storages of forest litter, this study estimated the phytolith and PhytOC storages in litter layers in different forest types in southern China. The results indicated that the total phytolith storage in forest litter layers in southern China was 24.34 ± 8.72 Tg. Among the different forest types, the phytolith storage in bamboo forest litter layers (15.40 ± 3.40 Tg) was much higher than that in other forests. At the same time, the total PhytOC storage reached up to 2.68 ± 0.96 Tg CO2 in forest litter layers in southern China, of which approximately 60% was contributed by bamboo forest litter layers. Based on the current litter turnover time of different forest types in southern China, a total of 1.01 ± 0.32 Tg of PhytOC per year would be released into soil profiles as a stable C pool during litter decomposition, which would make an important contribution to the global terrestrial long-term biogeochemical C sink. Therefore, the important role of PhytOC storage in forest litter layers should be taken into account in evaluating long-term forest C budgets

The importance of non-carbonate mineral weathering as a soil formation mechanism within a karst weathering profile in the SPECTRA Critical Zone Observatory, Guizhou Province, China

Soil degradation, including rocky desertification, of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock (marls). Atmospheric inputs from dust were also detected

Evaluation of pharmacological and pharmacokinetic herb-drug interaction between irinotecan hydrochloride injection and Kangai injection in colorectal tumor-bearing mice and healthy rats

Introduction: Kangai (KA) injection, a Chinese herbal injection, is often used in combination with irinotecan (CPT-11) to enhance the effectiveness of anti-colorectal cancer treatment and alleviate side effects. However, the combined administration of this herb-drug pair remains controversial due to limited pre-clinical evidence and safety concerns. This study aimed to determine the pre-clinical herb-drug interactions between CPT-11 and KA injection to provide a reference for their clinical co-administration.Methods: In the pharmacological study, BALB/c mice with CT26 colorectal tumors were divided into four groups and treated with vehicle alone (0.9% saline), CPT-11 injection (100 mg/kg), KA injection (10 mL/kg), or a combination of CPT-11 and KA injection, respectively. The tumor volume of mice was monitored daily to evaluate the therapeutic effect. Daily body weight, survival rate, hematopoietic toxicity, immune organ indices, and gut toxicity were analyzed to study the adverse effects. Healthy Sprague-Dawley rats in the pharmacokinetic study were administered KA injection only (4 mL/kg), or a combination of CPT-11 injection (20 mg/kg) and KA injection, respectively. Six key components of KA injection (oxymatrine, matrine, ginsenoside Rb1, Rg1, Re, and astragaloside IV) in rat plasma samples collected within 24 h after administration were determined by LC-MS/MS.Results: The pharmacological study indicated that KA injection has the potential to enhance the anti-colorectal cancer efficacy of CPT-11 injection and alleviate the severe weight loss induced by CPT-11 injection in tumor-bearing mice. The pharmacokinetic study revealed that co-administration resulted in inhibition of oxymatrine metabolism in rats, evidenced by the significantly reduced Cmax and AUC0-t of its metabolite, matrine (p < 0.05), from 2.23 ± 0.24 to 1.38 ± 0.12 μg/mL and 8.29 ± 1.34 to 5.30 ± 0.79 μg h/mL, respectively. However, due to the similar efficacy of oxymatrine and matrine, this may not compromise the anti-cancer effect of this herb-drug pair.Discussion: This study clarified the pre-clinical pharmacology and pharmacokinetic benefits and risks of the CPT-11-KA combination and provided a reference for their clinical co-administration

Bedrock geochemistry influences vegetation growth by regulating the regolith water holding capacity

Although low vegetation productivity has been observed in karst regions, whether and how bedrock geochemistry contributes to the low karstic vegetation productivity remain unclear. In this study, we address this knowledge gap by exploring the importance of bedrock geochemistry on vegetation productivity based on a critical zone investigation across a typical karst region in Southwest China. We show silicon and calcium concentrations in bedrock are strongly correlated with the regolith water loss rate (RWLR), while RWLR can predict vegetation productivity more effectively than previous models. Furthermore, the analysis based on 12 selected karst regions worldwide further suggest that lithological regulation has the potential to obscure and distort the influence of climate change. Our study implies that bedrock geochemistry could exert effects on vegetation growth in karst regions and highlights that the critical role of bedrock geochemistry for the karst region should not be ignored in the earth system mode

Soil functions and ecosystem services research in the Chinese karst Critical Zone

Covering extensive parts of China, karst is a critically important landscape that has experienced rapid and intensive land use change and associated ecosystem degradation within only the last 50 years. In the natural state, key ecosystem services delivered by these landscapes include regulation of the hydrological cycle, nutrient cycling and supply, carbon storage in soils and biomass, biodiversity and food production. Intensification of agriculture since the late-20th century has led to a rapid deterioration in Critical Zone (CZ) state, evidenced by reduced crop production and rapid loss of soil. In many areas, an ecological ‘tipping point’ appears to have been passed as basement rock is exposed and ‘rocky desertification’ dominates. This paper reviews contemporary research of soil processes and ecosystems service delivery in Chinese karst ecosystems, with an emphasis on soil degradation and the potential for ecosystem recovery through sustainable management. It is clear that currently there is limited understanding of the geological, hydrological and ecological processes that control soil functions in these landscapes, which is critical for developing management strategies to optimise ecosystem service delivery. This knowledge gap presents a classic CZ scientific challenge because an integrated multi-disciplinary approach is essential to quantify the responses of soils in the Chinese karst CZ to extreme anthropogenic perturbation, to develop a mechanistic understanding of their resilience to environmental stressors, and thereby to inform strategies to recover and maintain sustainable soil function. © 2019 Elsevier B.V

Geochemistry of rare earth elements in soils under different land uses in a typical karst area, Guizhou Province, Southwest China

Understanding soil erosion processes under different land uses is important for predicting and controlling watershed soil losses, especially in karst areas. Five soil profiles and 55 soil samples were collected from soils that were under different land uses in a typical karst catchment, Southwest China. The total contents of rare earth elements (REE) are significantly lower (< 100 mg kg(-1)) than the average value of soils in China (181 mg kg(-1)). The enrichment degree of REE in heavy REE is much higher than that of light REE in all soil samples. A positive Ce anomaly (similar to 1.4) and a slightly negative Eu anomaly (similar to 0.95) were found. The enrichment and release of REE are partly controlled by pH, distribution of REE in bedrocks, contents, and adsorption ability of organic matters in weathering profiles

Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon.

The continental bio-cycling of silicon (Si) plays a key role in global Si cycle and as such partly controls global carbon (C) budget through nutrition of marine and terrestrial biota, accumulation of phytolith-occluded organic carbon (PhytOC) and weathering of silicate minerals. Despite the key role of elemental composition of phytoliths on their solubility in soils, the impact of plant cultivar and organ on the elemental composition of phytoliths in Si high-accumulator plants, such as rice (Oryza sativa) is not yet fully understood. Here we show that rice cultivar significantly impacts the elemental composition of phytoliths (Si, Al, Fe and C) in different organs of the shoot system (grains, sheath, leaf and stem). The amount of occluded OC within phytoliths is affected by contents of Si, Al and Fe in plants, while independent of the element composition of phytoliths. Our data document, for different cultivars, higher bio-available Si release from phytoliths of leaves and sheaths, which are characterized by higher enrichment with Al and Fe (i.e., lower Si/Al and Si/Fe ratios), compared to grains and stems. We indicate that phytolith solubility in soils may be controlled by rice cultivar and type of organs. Our results highlight that the role of the morphology, the hydration rate and the chemical composition in the solubility of phytoliths and the kinetic release of Si in soil solution needs to be studied further. This is central to a better understanding of the impact of soil amendment with different plant organs and cultivars on soil OC stock and on the delivery of dissolved Si as we show that sheath and leaf rice organs are both characterized by higher content of OC occluded in phytolith and higher phytolith solubility compared to grains and stems. Our study shows the importance of studying the impact of the agro-management on the evolution of sinks and sources of Si and C in soils used for Si-high accumulator plants