Humic acid complex formation with urea alters its structure and enhances biomass production in hydroponic maize.

BACKGROUND: Humic acid (HA)-enhanced urea (HAU) is the top-selling efficiency-enhanced urea in China. Comprehensive investigation into the structure and efficacy of HA complex formation with urea (HACU) - the main reaction product during HAU's production - is required to clarify the reaction mechanism between HA and urea, and to provide guidance for the development of high-efficiency HAU. RESULTS: HACU showed discrepant structural and compositional features from raw HA. Nitrogen (N) content in HACU was 7.3 times greater than that of HA. Several high-resolution analytical methods showed a sharp increase of ammonia in the gaseous product during HACU pyrolysis, suggesting that urea contributed N to HACU. HACU was characterized with significantly fewer carboxyl groups than in raw HA, implying that the carboxyl group was the main group in HA to participate in the reaction between HA and urea. The presence of amide-N in HACU verified the structure of the reaction product. Furthermore, both HACU and HA could enhance the biomass in hydroponically grown maize seedlings, but the highest stimulation for HACU came about when its carbon concentrations were 50-100 mg L-1 , higher than the optimal carbon concentration for HA (25 mg L-1 ), attributed to the lower carboxyl group content for HACU to some extent. CONCLUSION: During HAU's production, reaction with N derived from urea to form amide-N decreased the carboxyl groups in HA, leading to higher concentrations for HACU required to achieve the similar bioefficacy of HA. © 2021 Society of Chemical Industry.

Polydopamine-coated biomimetic bone scaffolds loaded with exosomes promote osteogenic differentiation of BMSC and bone regeneration.

Introduction: The repair of bone defects is ideally accomplished with bone tissue engineering. Recent studies have explored the possibility of functional modification of scaffolds in bone tissue engineering. We prepared an SF-CS-nHA (SCN) biomimetic bone scaffold and functionally modified the scaffold material by adding a polydopamine (PDA) coating loaded with exosomes (Exos) of marrow mesenchymal stem cells (BMSCs). The effects of the functional composite scaffold (SCN/PDA-Exo) on BMSC proliferation and osteogenic differentiation were investigated. Furthermore, the SCN/PDA-Exo scaffolds were implanted into animals to evaluate their effect on bone regeneration. Methods: SCN biomimetic scaffolds were prepared by a vacuum freeze-drying/chemical crosslinking method. A PDA-functionalized coating loaded with BMSC-Exos was added by the surface coating method. The physical and chemical properties of the functional composite scaffolds were detected by scanning electron microscopy (SEM), energy spectrum analysis and contact angle tests. In vitro, BMSCs were inoculated on different scaffolds, and the Exo internalization by BMSCs was detected by confocal microscopy. The BMSC proliferation activity and cell morphology were detected by SEM, CCK-8 assays and phalloidin staining. BMSC osteogenic differentiation was detected by immunofluorescence, alizarin red staining and qRT‒PCR. In vivo, the functional composite scaffold was implanted into a rabbit critical radial defect model. Bone repair was detected by 3D-CT scanning. HE staining, Masson staining, and immunohistochemistry were used to evaluate bone regeneration. Results: Compared with the SCN scaffold, the SCN/PDA-Exo-functionalized composite scaffold had a larger average surface roughness and stronger hydrophilicity. In vitro, the Exos immobilized on the SCN/PDA-Exo scaffolds were internalized by BMSCs. The BMSC morphology, proliferation ability and osteogenic differentiation effect in the SCN/PDA-Exo group were significantly better than those in the other control groups (p < 0.05). The effects of the SCN/PDA-Exo functional composite scaffold on bone defect repair and new bone formation were significantly better than those of the other control groups (p < 0.05). Conclusions: In this study, we found that the SCN/PDA-Exo-functionalized composite scaffold promoted BMSC proliferation and osteogenic differentiation in vitro and improved bone regeneration efficiency in vivo. Therefore, combining Exos with biomimetic bone scaffolds by functional PDA coatings may be an effective strategy for functionally modifying biological scaffolds.

Humic Acid Modified by Being Incorporated Into Phosphate Fertilizer Increases Its Potency in Stimulating Maize Growth and Nutrient Absorption.

Humic acid-enhanced phosphate fertilizer (HAP) is widely applied in Chinese agriculture due to its high efficiency. Although the structural composition and physicochemical properties of humic acid (HA) are significantly altered during HAP production, a clear understanding of the mechanisms underlying the biological effects of HA extracted from HAP fertilizer (PHA) on plant growth is still lacking. In the current study, we extracted PHA from HAP and assessed its effects on the dry biomass, phosphorus (P) and nitrogen (N) uptake, and P absorption rate of maize seedlings when supplied at different concentrations (2.5, 5, 10, and 25 mg C L-1) in the hydroponic culture. The root vigor, root plasma membrane H+-ATPase activity, and root nitrate reductase activity were also determined as the representative indicators of the root capacity for nutrient absorption, and used to clarify the mechanism by which PHA affects the maize growth and nutrient absorption. The results showed that the dry biomass, phosphorus uptake, nitrogen uptake, and average phosphorus absorption rates were significantly higher by 14.7-27.9%, 9.6-35.1%, 17.9-22.4%, and 22.1-31.0%, respectively, in plants treated with 2.5-5 mg C L-1 PHA compared to untreated controls. Application of 10-25 mg C L-1 raw HA resulted in similar stimulatory effects on plant growth and nutrient absorption. However, higher levels of PHA (10-25 mg C L-1) negatively impacted these indicators of plant growth. Furthermore, low PHA or high raw HA concentrations similarly improved root vigor and root plasma membrane H+-ATPase and nitrate reductase (NR) activities. These results indicate that lower concentrations of PHA can stimulate maize seedling growth and nutrient absorption to an extent that is comparable to the effect of higher concentrations of raw HA. Thus, the proportion of HA incorporated into HAP could be lower than the theoretical amount estimated through assays evaluating the biological effects of raw HA.

Combining humic acid with phosphate fertilizer affects humic acid structure and its stimulating efficacy on the growth and nutrient uptake of maize seedlings.

This paper analyzed the compositional and structural changes of humic acid (HA) after combined with phosphate fertilizer (PHA), and investigated its effects on the growth of maize seedlings with four humic acid concentrations. The results showed that the atomic ratios of O/C and (O + N)/N of PHA were significantly lower than those of HA, which indicated that PHA had poor hydrophilicity compared with HA. The spectra of FTIR and NMR results suggested that the relative content of carboxyl group in PHA was higher than that in HA. X-ray photoelectron spectroscopy technology showed that the relative amount of C-C in PHA was lower than that in HA, while C-H was the opposite. The above changes were attributed to the crack of HA structure during the preparation of humic acid enhanced phosphate fertilizer, which was verified by the results from the determination of gel permeation chromatography that there were more low molecular weight components in PHA than that in HA. However, compared with HA, PHA showed a worse effect in promoting growth and the uptake of nitrogen, phosphorus and potassium by maize seedlings. This worse effect might be attributed to the poor hydrophilicity and unsuitable addition amount of PHA.

Characterization of pH-fractionated humic acids derived from Chinese weathered coal.

To reduce the compositional and structural heterogeneity of humic acids (HAs) and achieve better use of HA resources, in this study, we report a new sequential dissolution method for HAs derived from Chinese weathered coal. This method was used to separate HAs into seven fractions by adjusting the pH (3-10) of the extraction solution. The results showed that the HA fractions derived from Chinese weathered coal were concentrated up to 90.31% in the lower pH solutions (3-7). The compositional and structural characteristics of the HA fractions were determined by elemental analysis; ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), and solid-state 13C-nuclear magnetic resonance (NMR) spectroscopies; and other techniques. The results showed significant differences among the HA fractions. The concentrations of the total acidic groups and the carboxyl groups decreased with the increasing pH of the extraction solution. However, the HA fractions derived from extraction solutions with pH 3-4 had relatively lower aromaticity but a higher protonated carbon content. The HA fractions derived from extraction solutions with pH 6-7 had the highest aromaticity and the greatest abundance of COO/N-C=O. This study demonstrated that adjusting the pH of the extraction solution is one way to fractionate HAs from Chinese weathered coal and to obtain HA fractions with compositions and structures that could serve as useful material for study and utilization.

[Effects of Different Organic Materials on Bio-availability of Cd, Pb in a Contaminated Greenhouse Soil].

A two-season soil culture experiment was continually conducted to study the effects of three organic materials,namely Danty, Peat and Biochar,respectively,on combined forms and bio-availability of cadmium (Cd) and lead (Pb) under Cd and Pb in single and combined pollution during 2014-2015. This study aimed to provide a theoretical basis for remediating greenhouse soil contaminated with heavy metals Cd and Pb using organic materials. The main results were as follows: the content of DTPA-Cd decreased significantly by 11.9%(P<0.05) in the soil of Cd and Pb combined pollution with the application of danty, the total of exchangeable Cd, carbonate-bound Cd and iron-manganese oxide bound Cd was reduced by 26.4% and 34.4% in the soil, and the accumulation of Cd in shoots was significantly cut down by 32.0% and 28.0% (P<0.05) respectively in Cd single and Cd and Pb combined pollution after applying danty; the content of DTPA-Pb was significantly depleted by 83.5% and 83.8%(P<0.05), the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was decreased by 34.5% and 13.9% in the soil and the accumulation of Pb in shoots was significantly reduced by 32.0% and 30.0% (P<0.05) in Pb single and Cd and Pb combined pollution respectively as the use of danty. The content of DTPA-Cd was significantly decreased by 18.9% (P<0.05) in the soil of Cd and Pb combined pollution with the use of peat, the accumulation of Cd in shoots was reduced by 38.0% and 23.4%(P<0.05) in Cd single and Cd-Pb combined pollution respectively after the application of peat; The content of DTPA-Pb was significantly decreased by 2.7% and 7.2%(P<0.05), the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was decreased by 15.8% and 14.6% in the soil and the accumulation of Pb in shoots was significantly reduced by 12.7% and 23.4% (P<0.05) respectively in Pb single and Cd and Pb combined pollution due to the application of peat. The pH value of the soil was increased by the use of biochar, the content of DTPA-Cd was reduced by 4.7% and 15.0% respectively in the soil of Cd single and Cd and Pb combined pollution, and the accumulation of Cd in shoots was significantly minified by 38.0% and 23.4% respectively in Cd single and Cd and Pb combined pollution as the application of biochar. The content of DTPA-Pb was decreased by 6.8% and 1.0% and the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was cut down by 11.9% and 30.0% in the soil of Pb single and Cd and Pb combined pollution respectively by the application of biochar. The content of Cd in plant was most significantly positively correlated with the content of exchangeable Cd in soil (P<0.01). The content of Pb in plant was most significantly positively correlated with the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb (P<0.01). In summary, after the application of danty, peat and biochar, the proportion of highly active content of Cd and Pb was minified through adjusting soil pH and immobilizing Cd and Pb by means of adsorption and complexation in greenhouse soil. With the analysis of input-output, the application of danty, peat and biochar costs 4050 yuan·hm-2, 11250 yuan·hm-2 and 22500 yuan·hm-2, respectively. Thus danty, peat and biochar could be used as effective organic agents in the remediation of Cd and Pb contaminated greenhouse soil.

Age-related impaired Th1 responses to PRV vaccine in vivo in aged pigs.

Murine model studies have shown that function of the immune system declines with aging, but data on aged pigs are scarce. Many physiological and pathophysiological data of pigs can be transferred to human, research in pigs is important to confirm murine data, therefore, aged pigs were chosen as an aged animal model. In this study, we demonstrated an age-related decline in Th1 responses in vivo to PRV vaccine in the pig model, and this decline in type 1 immune responses was associated with reduced PRV-specific T cell proliferation, IgG2/IgG1, and Th1 cytokines production. More importantly, these impaired Th1 responses correlated with reduced CD4(+) T cells and markedly increased CD4(+)CD8(+) T cells. Taken together, these data demonstrated that there was a decline in Th1 immune responses to PRV vaccine with aging in pigs, which may help to explain the age-related decline in vaccine efficacy and increase in morbidity and mortality of infectious diseases.