Effects of Astaxanthin on Growth Performance, Gut Structure, and Intestinal Microorganisms of Penaeus vannamei under Microcystin-LR Stress.

Microcystin-LR (MC-LR) are biologically active cycloheptapeptide compounds that are released by cyanobacteria during water blooms and are extensively found in aquatic ecosystems. The Penaeus vannamei is a significant species in global aquaculture. However, the high level of eutrophication in aquaculture water frequently leads to outbreaks of cyanobacterial blooms, posing a significant threat to its sustainable cultivation. Astaxanthin (AX) is commonly utilized in aquaculture for its physiological benefits, including promoting growth and enhancing immune function in cultured organisms. This study aimed to examine the protective effect of astaxanthin on P. vannamei exposed to microcystin-induced stress. The experiment consisted of three groups: one group was fed formulated feed containing MC (100 µg/kg), another group was fed formulated feed containing MC (100 µg/kg) + AX (100 mg/kg), and the third group was fed basic feed (control group). After 15 days of feeding, the specific growth rate (SGR) was significantly higher in the MCAX group (2.21% day-1) compared to the MC group (0.77% day-1), and there was no significant difference between the MCAX group (2.21% day-1) and the control group (2.24% day-1). Similarly, the percent of weight gain (PWG) was also significantly higher in the MCAX group (14.61%) compared to the MC group (13.44%) and the control group (16.64%). Compared to the control group, the epithelial cells in the MC group suffered severe damage and detachment from the basement membrane. However, in the MCAX group, although there was still a gap between the intestinal epithelial cells and the basement membrane, the overall intestinal morphology was slightly less impaired than it was in the MC group. The analysis of the intestinal microbiota revealed a significant disparity in the community composition (chao 1 and ACE) between the MC and MCAX groups. When comparing the various bacterial genera, the MC group exhibited an increase in Vibrio abundance, whereas the MCAX group showed a decrease in both Shewanella and Vibrio abundance. The results indicate that AX has a positive impact on the growth performance and resistance of P. vannamei against MC by regulating the composition of the intestinal microbiota. AX can be utilized to mitigate the detrimental effects of MC in aquaculture practices. This function could be attributed to the role of AX in preserving the structural integrity of the intestinal mucosa and regulating the composition of the intestinal microbiota.

Gold nanoparticles bearing a clinically used non-antibiotic drug for combating multi-drug resistant bacteria.

We introduce N-acetyl-L-cysteine (NAC), a clinically used non-antibiotic drug, to the synthesis of antibacterial gold nanoparticles (Au_NAC). Au_NAC shows excellent antibacterial activities against multi-drug resistant (MDR) Gram-negative bacteria and possesses wound healing capabilities. We provide a new direction for antibiotic design and novel uses of known drugs.

Bioeffects of Inhaled Nanoplastics on Neurons and Alteration of Animal Behaviors through Deposition in the Brain.

The potential toxicity of nanoplastics on plants has previously been illustrated, but whether nanoplastics could cause neurotoxicity, especially to higher animals, remains unclear. We now demonstrate that nanoplastics can be deposited in the brain via nasal inhalation, triggering neuron toxicity and altering the animal behavior. Polystyrene nanoparticles (PS-NPs) of PS-COOH and PS-NH2 are used as models for nanoplastics. We designed a microfluidic chip to evaluate the PS-NPs with different concentrations, surface ligands, and sizes to interact with neurons. Smaller PS-NPs can induce more cellular uptake than larger PS-NPs. PS-NPs with a size of 80 nm can reach and deposit in the brain of mice via aerosol inhalation. Mice inhaling PS-NPs exhibit fewer activities in comparison to those inhaling water droplets. An obvious neurotoxicity of the nanoplastics could be observed from the results of the inhibition of AChE activities. Our results show the potential significance of the physiochemical properties of organic nanoplastics on depositing in mammalian brains by nasal inhalation.

DNA cleavage and chemical transformation of nano-plastics mediated by surface ligand and size.

Here, we investigated the photochemistry of nano-plastic particles with different surface ligands and sizes (i.e. PS-NH2 40, 80, 100, 200 nm and PS-COOH 40, 80, 100, 200 nm) under a solar simulator. Our findings provide new insights into DNA cleavage and chemical transformation of nano-plastics, especially mediated by different ligands and sizes.

DNA Cleavage by Chemically Exfoliated Molybdenum Disulfide Nanosheets.

Chemically exfoliated MoS2 (ce-MoS2) nanosheets have been widely used in biomedical and environmental fields. Some in vitro studies demonstrated that ce-MoS2 might induce toxicity. However, the understanding of the mechanism of potential toxicity is lacking. In this study, we found that ce-MoS2 could directly induce breakage of double-stranded DNA with or without an external energy input, making it different from other two-dimensional nanomaterials. In a dark environment, the DNA cleavage exhibited a pH-dependent trend due to reactive oxygen species generation under different pH values. Under photoirradiation, DNA cleavage could be enhanced. This study provides insights into the potential environmental risk and toxicity of ce-MoS2 in the aquatic environment.

The antibacterial activities of MoS2 nanosheets towards multi-drug resistant bacteria.

We demonstrated that molybdenum disulfide (MoS2) nanosheets can be an excellent solar disinfection agent for multi-drug resistant (MDR) bacteria with disinfection efficiencies >99.9999% in only 30 min. Distinct from other reactive oxygen species (ROS)-dependent photocatalysts, both ROS generation and size decrease contributed to the high antibacterial efficiencies of MoS2.

Environmental transformation of graphene oxide in the aquatic environment.

In recent years, research on graphene oxide (GO) has developed rapidly in both academic and industrial applications such as electronic, biosensor, drug delivery, water treatment and so forth. Based on the large amount of applications, it is anticipated that GO will inevitably find its own way to the environment, if used are not restricted to prevent their release. Environmental transformation is an important transformation process in the natural environment. In this review, we will summarize the recent developments on environmental transformation of GO in the aquatic environment. Although papers on environmental transformation of graphene-based nanomaterials can be found, a systematic picture describing photo-transformation of GO (dividing into different irradiation sources), environmental transformation of GO in the dark environmental, the environmental toxicity of GO are still lacking. Thus, it is essential to summarize how different light sources will affect the GO structure and reactive oxygen species generation in the photo-transformation process, how GO will react with various natural constituents in the aquatic environment, whether GO will toxic to different aquatic organisms and what will be the interactions between GO and the intracellular receptors in the intracellular level once GO released into the aquatic environment. This review will arouse the realization of potential risk that GO can bring to the aquatic environment and enlighten us to pay attention to behaviors of other two-dimensional GO-like nanomaterials, which have been intensively applied and studied in recent years.

Photoreactivity of Metal-Organic Frameworks in Aqueous Solutions: Metal Dependence of Reactive Oxygen Species Production.

Promising applications of metal-organic frameworks (MOFs) in various fields have raised concern over their environmental fate and safety upon inevitable discharge into aqueous environments. Currently, no information regarding the transformation processes of MOFs is available. Due to the presence of repetitive π-bond structure and semiconductive property, photochemical transformations are an important fate process that affects the performance of MOFs in practical applications. In the current study, the generation of reactive oxygen species (ROS) in isoreticular MIL-53s was studied. Scavengers were employed to probe the production of (1)O2, O2(•-), and •OH, respectively. In general, MIL-53(Cr) and MIL-53(Fe) are dominated by type I and II photosensitization reactions, respectively, and MIL-53(Al) appears to be less photoreactive. The generation of ROS in MIL-53(Fe) may be underestimated due to dismutation. Further investigation of MIL-53(Fe) encapsulated diclofenac transformation revealed that diclofenac can be easily transformed by MIL-53(Fe) generated ROS. However, the cytotoxicity results implied that the ROS generated from MIL-53s have little effect on the viability of the human hepatocyte (HepG2) cell line. These results suggest that the photogeneration of ROS by MOFs may be metal-node dependent, and the application of MIL-53s as drug carriers needs to be carefully considered due to their high photoreactivity.

Soil microbial response to photo-degraded C60 fullerenes.

Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C60 fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C60. Irradiating aqueous (13)C-labeled C60 with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C60 to soil microcosms had little effect on net soil respiration, excess (13)C in the respired CO2 demonstrates that photo-irradiating C60 enhanced its degradation in soil, with ∼ 0.78% of 60 day photo-irradiated C60 mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how abiotic and biotic transformation processes can couple to influence degradation of CNMs in the natural environment.

Effect of dosing sequence and solution pH on floc properties of the compound bioflocculant-aluminum sulfate dual-coagulant in kaolin-humic acid solution treatment.

The compound bioflocculant (CBF)-aluminum sulfate (AS) dual-coagulant and AS were comparatively studied for the coagulation of kaolin-humic acid solution. Floc properties including floc growth rate, size, strength, recoverability and fractal dimension under different pH conditions were investigated by Mastersizer 2000. Results indicated that, the flocs formed by AS-CBF (AS dosed first) showed the largest size and the best recoverability across the pH range investigated. While flocs formed by CBF-AS gave the most compact structure. The three coagulants exhibited similar floc growth rate and strength. Moreover, flocs formed in acidic conditions were stronger and more recoverable but showed lower growth rate, smaller size and looser structure compared to those formed at pH>6 regardless of the coagulant used. Charge neutralization was the dominant mechanism for AS at low pH, while the coagulation mechanism transformed to enmeshment as the pH increased. There was an additional adsorption bridging effect for AS-CBF and CBF-AS.

Binding of Sudan II and Sudan IV to bovine serum albumin: comparison studies.

In this paper, we report the interaction of Sudan II and Sudan IV to bovine serum albumin (BSA). Structural analysis showed that both Sudan II and Sudan IV interact mainly with BSA at the hydrophobic pocket and via Van der Waals forces. The number of bound Sudan molecule for each protein molecule was approximately 1. The overall binding constants at 293 K (20°C) estimated for Sudan II and Sudan IV were 1.22 × 10(4)M(-1) and 1.48 × 10(4)M(-1), respectively. BSA backbone structure was damaged by the dyes with more severe phenomenon observed for Sudan IV. For two Sudan dyes with the same concentration, Sudan IV could cause more alterations on CD spectra of BSA with slight decrease of α-helical content and increase of ß-sheet content, suggesting a partial protein unfolding.