Na Ling

Background: Heavy metal pollution has become a global problem, which urgently needed to be solved owing to its severe threat to water ecosystems and human health. Thus, the exploration and development of a simple, cost-effective and environmental-friendly technique to remove metal elements from contaminated water is of great importance. Algae are a kind of photosynthetic autotroph and exhibit excellent bioadsorption capacities, making them suitable for wastewater treatment.Methods: The effects of heavy metals (copper, lead and cadmium) on the growth, biomolecules accumulation, metabolic responses and antioxidant response of Dunaliella salina were investigated. Moreover, the Box-Behnken design (BBD) in response surface methodology (RSM) was used to optimize the biosorption capacity, and FT-IR was performed to explore the biosorption mechanism of D. salina on multiple heavy metals.Results: The growth of D. salina cells was significantly inhibited and the contents of intracellular photosynthetic pigments, polysaccharides and proteins were obviously reduced under different concentrations of Cu²⁺, Pb²⁺ and Cd²⁺, and the EC50 values were 18.14 mg/L, 160.37 mg/L and 3.32 mg/L at 72 h, respectively. Besides, the activities of antioxidant enzyme SOD and CAT in D. salina first increased, and then descended with increasing concentration of three metal ions, while MDA contents elevated continuously. Moreover, D. salina exhibited an excellent removal efficacy on three heavy metals. BBD assay revealed that the maximal removal rates for Cu²⁺, Pb²⁺, and Cd²⁺ were 88.9%, 87.2% and 72.9%, respectively under optimal adsorption conditions of pH 5-6, temperature 20-30°C, and adsorption time 6 h. Both surface biosorption and intracellular bioaccumulation mechanisms are involved in metal ions removal of D. salina. FT-IR spectrum exhibited the main functional groups including carboxyl (-COOH), hydroxyl (-OH), amino (-NH2), phosphate (-P=O) and sulfate (-S=O) are closely associated with the biosorption or removal of heavy metalsions.Discussion: Attributing to the brilliant biosorption capacity, Dunaliella salina may be developed to be an excellent adsorbent for heavy metals.

Copper (Cu) is one of the essential microelements for plants and algae. It can stimulate growth and photosynthesis at low concentration but inhibit them at higher concentration. The knowledge of molecular response mechanisms to copper stress in green algae is still limited. The responses of the green algae Dunaliella salina to Cu stress were studied using the physiochemical indexes and RNA-seq analysis. The physiochemical indexes such as growth rate, the content of chlorophyll and soluble sugar, photosynthesis and peroxidase activity were all changed in D. salina under Cu stress. In addition, a total of 3799 differentially expressed genes (DEGs) were identified between the control and Cu-treated group. Among these, 2350 unigenes were up-regulated whereas 1449 were down-regulated. Here, the DEGs encoding proteins relevant to photosynthesis, carbon assimilation and carbohydrate mechanism were significantly up-regulated in the Cu-treated group. In addition, the unigenes encoding proteins involved in the antioxidant system and heat shock proteins were also up-regulated, and these were consistent with the expression patterns based on TPM (transcripts per million) values. This study shows that the enhanced growth and photosynthesis and carbon mechanism in D. salina can be triggered by copper, which will lay a firm foundation for future breeding and carotenoid production, further highlighting the underlying application of D. salina as a functional food.

Schedule-Dependent Effects of Kappa-Selenocarrageenan in Combination with Epirubicin on Hepatocellular Carcinoma Kappa-selenocarrageenan;epirubicin;cmbination therapy;HCC;cell cycle; Hepatocellular carcinoma (HCC) has a relatively higher incidence in many countries of Asia. Globally, HCC has a high fatality rate and short survival. Epirubicin, a doxorubicin analogue, may be administered alone or in combination with other agents to treat primary liver cancer and metastatic diseases. However, the toxic effects of epirubicin to normal tissues and cells have been one of the major obstacles to successful cancer chemotherapy. Here, we investigated the effects of epirubicin in combination with kappa-selenocarrageenan on mice with H22 implanted tumors and HepG-2 cell proliferation, immune organ index, morphology, cell cycle and related protein expressions in vivo and in vitro with sequential drug exposure. The inhibitory rate of tumor growth in vivo was calculated. Drug sensitivity was measured by MTT assay, and the King's principle was used to evaluate the interaction of drug combination. Morphological changes were observed by fluorescent microscopy. Cell cycle changes were analyzed by flow cytometry. Expression of cyclin A, Cdc25A and Cdk2 were detected by Western blotting. In vivo results demonstrated that the inhibitory rate of EPI combined with KSC was higher than that of KSC or EPI alone, and the Q value indicated an additive effect. In addition, KSC could significantly raise the thymus and spleen indices of mice with H22 implanted tumors. In the drug sensitivity assay in vitro, exposure to KSC and EPI simultaneously was more effective than exposure sequentially in HepG-2 cells, while exposure to KSC prior to EPI was more effective than exposure to EPI prior to KSC. Q values showed an additive effect in the simultaneous group and antagonistic effects in the sequential groups. Morphological analysis showed similar results to the drug sensitivity assay. Cell cycle analysis revealed that exposure to KSC or EPI alone arrested the cells in S phase in HepG-2 cells, exposure to KSC and EPI simultaneously caused accumulation in the S phase, an effect caused by either KSC or EPI. Expression of cyclin A, Cdc25A and Cdk2 protein was down-regulated following exposure to KSC and EPI alone or in combination, exposure to KSC and EPI simultaneously resulting in the lowest values. Taken together, our findings suggest that KSC in combination with EPI might have potential as a new therapeutic regimen against HCC.