Cadmium-Induced Physiological Responses, Biosorption and Bioaccumulation in Scenedesmus obliquus.

Cadmium ion (Cd2+) is a highly toxic metal in water, even at low concentrations. Microalgae are a promising material for heavy metal remediation. The present study investigated the effects of Cd2+ on growth, photosynthesis, antioxidant enzyme activities, cell morphology, and Cd2+ adsorption and accumulation capacity of the freshwater green alga Scenedesmus obliquus. Experiments were conducted by exposing S. obliquus to varying concentrations of Cd2+ for 96 h, assessing its tolerance and removal capacity towards Cd2+. The results showed that higher concentrations of Cd2+ (>0.5 mg L-1) reduced pigment content, inhibited algal growth and electron transfer in photosynthesis, and led to morphological changes such as mitochondrial disappearance and chloroplast deformation. In this process, S. obliquus counteracted Cd2+ toxicity by enhancing antioxidant enzyme activities, accumulating starch and high-density granules, and secreting extracellular polymeric substances. When the initial Cd2+ concentration was less than or equal to 0.5 mg L-1, S. obliquus was able to efficiently remove over 95% of Cd2+ from the environment through biosorption and bioaccumulation. However, when the initial Cd2+ concentration exceeded 0.5 mg L-1, the removal efficiency decreased slightly to about 70%, with biosorption accounting for more than 60% of this process, emerging as the predominant mechanism for Cd2+ removal. Fourier transform infrared correlation spectroscopy analysis indicated that the carboxyl and amino groups of the cell wall were the key factors in removing Cd2+. In conclusion, S. obliquus has considerable potential for the remediation of aquatic environments with Cd2+, providing algal resources for developing new microalgae-based bioremediation techniques for heavy metals.

Insights into the Enhanced Photogeneration of Hydroxyl Radicals from Chlorinated Dissolved Organic Matter.

Free available chlorine has been and is being applied in global water treatment and readily reacts with dissolved organic matter (DOM) in aquatic environments, leading to the formation of chlorinated products. Chlorination enhances the photoreactivity of DOM, but the influence of chlorinated compounds on the photogeneration of hydroxyl radicals (•OH) has remained unexplored. In this study, a range of chlorinated carboxylate-substituted phenolic model compounds were employed to assess their •OH photogeneration capabilities. These compounds demonstrated a substantial capacity for •OH production, exhibiting quantum yields of 0.1-5.9 × 10-3 through direct photolysis under 305 nm and 0.2-9.5 × 10-3 through a triplet sensitizer (4-benzoylbenzoic acid)-inducing reaction under 365 nm LED irradiation. Moreover, the chlorinated compounds exhibited higher light absorption and •OH quantum yields compared to those of their unchlorinated counterparts. The •OH photogeneration capacity of these compounds exhibited a positive correlation with their triplet state one-electron oxidation potentials. Molecular-level compositional analysis revealed that aromatic structures rich in hydroxyl and carboxyl groups (e.g., O/C > 0.5 with H/C < 1.5) within DOM serve as crucial sources of •OH, and chlorination of these compounds significantly enhances their capacity to generate •OH upon irradiation. This study provides novel insights into the enhanced photogeneration of •OH from chlorinated DOM, which is helpful for understanding the fate of trace pollutants in chlorinated waters.

Molecular complexation properties of Cd2+ by algal organic matter from Scenedesmus obliquus.

A detailed understanding the metals binding with algal organic matter (AOM) is essential to gain a deeper insight into the toxicity and migration of metals in algae cell. However, the molecular complexation mechanism of the metals binding with AOM remains unclear. In this study, cadmium ion (Cd2+) binding properties of AOMs from Scenedesmus obliquus, which included extracellular organic matter (EOM) and intracellular organic matter (IOM), were screened. When Cd2+ < 0.5 mg/L, the accumulation of Cd2+ could reach 40%, while Cd2+ > 0.5 mg/L, the accumulation of Cd2+ was only about 10%. EOM decreased gradually (from 8.51 to 3.98 mg/L), while IOM increased gradually (from 9.62 to 21.00 mg/L). The spectral characteristics revealed that IOM was richer in peptides/proteins and had more hydrophilic than EOM. Both EOM and IOM contained three protein-like components (containing tryptophan and tyrosine) and one humic-like component, and their contents in IOM were higher than that in EOM. The tryptophan protein-like substances changed greatly during Cd2+ binding, and that the tryptophan protein-like substances complexed to Cd2+ before tyrosine protein-like substances in IOM was identified. Moreover, the functional groups of N-H, O-H, and CO in AOM played an important role, and the N-H group was priority to interacts with Cd2+ in the complexing process. More functional groups (such as C-O and C-N) were involved in the metals complexing in EOM than in IOM. It could be concluded that Cd2+ stress promoted the secretion of AOM in Scenedesmus obliquus, and proteins in AOM could complex Cd2+ and alleviate its toxicity to algal cell. These findings provided deep insights into the interaction mechanism of AOM with Cd2+ in aquatic environments.

In-situ determination of the observed yield coefficient of aerobic activated sludge by headspace gas chromatography.

This paper describes a headspace gas chromatographic (HS-GC) method for the in-situ determination of the observed yield coefficient (Yobs) of aerobic activated sludge from domestic wastewater treatment plants. It is based on the measurement of oxygen and carbon dioxide in samples that have been incubated in headspace vials for relatively short periods of time. The method has good precision (the relative standard deviation < 5.46%) and accuracy (the relative differences < 9.23% when compared with the data from the reference method). The new method is much simpler and more efficient than the reference methods and should greatly facilitate the testing in aerobic activated sludge related applications, such as system design, operation and management.

Simple and efficient dual-wavelength spectroscopy for the determination of organic matter in sewage sludge from wastewater treatment.

In this study, a dual-wavelength spectroscopic method for rapid determination of organic matter in sludge was developed. The contents of the organic matter were calculated by determining the consumption of potassium dichromate (K2Cr2O7) based on the production of trivalent chromium ions (Cr3+). Cr3+ could be determined by subtracting the absorption at 800 nm (spectral interference) from the absorption at 650 nm (only contributed by Cr3+). The results showed that the relative standard deviation in the test was less than 5%. The same set of samples was used and when the content of organic matter was more than 150 g kg-1, the relative difference between the spectroscopic method and titration method was within 1%. Furthermore, the method does not require calibration based on the standard samples. In conclusion, the present method is simple, reliable, accurate and suitable for application in mass testing for sludge samples.

Biological activities and nitrogen and phosphorus removal during the anabaena flos-aquae biofilm growth using different nutrient form.

This work investigated the biological activities and nitrogen and phosphorus removal during the anabaena flos-aquae biofilm growth on the polyvinyl chloride (PVC) carriers, in different nutrient form mediums. The study showed that the production of dehydrogenase activity (DHA) and extracellular polymeric substances (EPS) can reach 40.4 g/(h·m2) and 115 × 10-2 g/m2 in an 11-day period, respectively, indicating that the anabaena flos-aquae biofilm had high biological activities. The results showed that the nitrogen and phosphorus removal reached 94.9 and 96.8%, respectively, in the ammonium form nitrogen group; while 97.7% of phosphorus were removed in the orthophosphate form phosphorous group. A comparison study was conducted and results showed that the present anabaena flos-aquae based biofilm provided a better removal of nitrogen and phosphorus than the other microalgae biofilms.

Antibody-based targeting of CD24 enhances antitumor effect of cetuximab via attenuating phosphorylation of Src/STAT3.

Epidermal growth factor receptor (EGFR) is a cell-surface receptor for some extracellular protein ligands relating to cancers and has been recognized as a key target for tumor therapy. Cetuximab, a chimerical monoclonal EGFR IgG1 antibody, is used for the treatment of various malignancies. However, recent clinical trials reported that the anti-tumor effect of cetuximab is still controversial. Cluster of differentiation 24 (CD24) is a tumor-associated antigen correlating with poor prognosis and regulating the activity of Src/STAT3 in multiple cancers. G7mAb was an anti-CD24 antibody derived by hybridoma technology in our previous study. To further evaluate the relationship between cetuximab and G7mAb in cancer therapy, this combination treatment was performed in vitro (A549, HT-29 and Huh-7 cells) and in vivo (xenograft mouse models). We showed that G7mAb suppressed the invasion and enhanced the anti-proliferation effect of cetuximab in A549, HT-29 and Huh-7 cells. Combination of cetuximab with G7mAb had enhanced effects on blocking the activation of signal transducer and activator of transcription 3 (STAT3) signal pathway. Furthermore, combination therapy of cetuximab with G7mAb significantly suppressed tumor developments and improved the survival rates in xenografted mice. In conclusion, G7mAb enhanced the antitumor effect of cetuximab by attenuating phosphorylation of Src/STAT3 both in vitro and in vivo. Combination of antibodies targeting EGFR or CD24 provided a potential strategy for cancer therapy.

Role of MCPIP1 in the Endothelial-Mesenchymal Transition Induced by Silica.

BACKGROUND: Silicosis is characterized by the accumulation of fibroblasts and the excessive deposition of extracellular matrix. Fibroblast generation via endothelial-mesenchymal transition (EndMT) is one process responsible for this accumulation of fibroblasts. However, the mechanisms underlying EndMT remain unknown. METHODS: Human umbilical vein endothelial cells (HUVECs) were exposed to SiO2 (50 µg/cm2). Specific endothelial and mesenchymal markers were evaluated using immunofluorescence and western blot analysis. Functional changes were evaluated by analyzing cell migration and proliferation. LC3-adenovirus transfections were performed, and changes in autophagy were measured using a marker of autophagy. RESULTS: SiO2 induced decreases in the endothelial cell-specific markers in HUVECs while dramatically increasing mesenchymal cell product levels and mesenchymal functions. Although MCPIP1 expression increased in parallel with the increase in specific mesenchymal cell products, the MCPIP1 expression level was not consistent with the observed decrease in specific endothelial marker expression. Autophagy mediated the effects of MCPIP1, as rapamycin and 3-MA enhanced and attenuated the effect of SiO2 on HUVECs, respectively. MAPKs and the PI3K/Akt pathway were involved in the regulation of MCPIP1 by SiO2, and Pyk2 and MLC-2 mediated cell migration. CONCLUSION: Our findings reveal a new potential function of MCPIP1, suggesting a possible mechanism of fibrosis in pulmonary silicosis.

Effects of nutrient loading on Anabaena flos-aquae biofilm: biofilm growth and nutrient removals.

Effects of three different nutrient loadings (low nutrient loading, medium nutrient loading and high nutrient loading, denoted as LNS, MNS and HNS, respectively) on the structure and functions of algal biofilm using Anabaena flos-aquae were investigated using synthetic wastewater. Nutrients removal efficiencies, biofilm thickness, microalgae dehydrogenase activity (DHA) and exopolysaccharide (EPS) productions were examined. Results showed that the changes of nutrient concentration were insignificant after 4 days of experiment for the case of HNS condition; 9 days for the case of MNS condition, and 6 days for the case of LNS condition, respectively. The biofilm thickness, nutrient removal efficiencies, algae DHA and EPS productions increased with the increase of nutrient loadings in synthetic wastewater. For the case of HNS condition, the microalgal biofilm exhibited the best performance in terms of C, N and P removal efficiencies, reaching the removal rates of 68.45, 3.56 and 1.61 mg·L(-1)·d(-1) for C, N, P, respectively. This was likely because, fact with the high nutrient loading, the high biological activity could be achieved, thus resulting in high nutrient removals. The thickness of the biofilm in HNS condition was 75 µm, which was closely related to EPS production. DHA and EPS concentrations were 7.24 and 1.8 × 10(-2) mg·mm(-2), respectively. It was also shown that apart from the nutrient loading, the structure and functions of microalgal biofilm were also influenced by other factors, such as illumination and temperature.

A novel antibody targeting CD24 and hepatocellular carcinoma in vivo by near-infrared fluorescence imaging.

Liver cancer is one of the most common malignant cancers worldwide. The poor response of liver cancer to chemotherapy has whipped up the interest in targeted therapy with monoclonal antibodies because of its potential efficiency. One promising target is cluster of differentiation 24 (CD24), which is known to beover-expressed on hepatocellular carcinoma (HCC), providing prospect for HCC targeted diagnosis and therapy. In this study we developed a novel CD24 targeted monoclonal antibody G7mAb based on hybridoma technology and then generated a single-chain antibodyfragment (scFv) G7S. Firstly, ELISA, western blot, and flow cytometry assays demonstrated specific binding of CD24 by G7mAb and G7S. Further, G7mAb was demonstrated to have similar binding capacity as ML5 (a commercial Anti-CD24 Mouse Antibody) inimmunohistochemical assay. Further more, a near-infrared fluorescent dye multiplex probe amplification (MPA) was conjugated to G7mAb and G7S to form G7mAb-MPA and G7S-MPA. The near-infrared fluorescence imaging revealed that G7mAb and G7S aggregate in CD24+Huh7 hepatocellular carcinoma xenograft tissuevia specific binding to CD24 in vivo. In conclussion, G7mAb and G7S were tumor targeted therapeutic and diagnostic potentials in vitro and in vivo as anticipated.