Immunotoxicological Threats of Pollutants in Aquatic Invertebrates

Immunology deals with the physiological activity of organisms to defend against pathogen and toxin invasion. Invertebrates residing in aquatic ecosystems often face toxicological threat arises from habitat pollution. The aquatic habitat of invertebrates is in the precarious risk of pollution caused by diverse groups of environmental toxins. Immunotoxins have been considered as a special group of pollutants capable of affecting the immunological profile of organisms. Invertebrates residing in water bear ecological, economical, medicinal, industrial, nutritional and biotechnological significance. Global aquatic bioresource is largely composed of invertebrates belonging to multiple Phyla. These organisms, including insects, snails, clams, mussels, crabs and sponges, are physiologically dependent on innate immunological response for defense against pathogen and environmental contaminants. External physicochemical barriers of invertebrates act as primary line of defen against toxin entry. Principal barriers have been identified as shell, tunic, test, carapace, mucus, etc., in diverse species. Toxin-induced morphological damage of specialized immunocytes of invertebrates has been reported. Toxin-induced shift in density, surface adhesion efficacy and aggregation of blood cells or haemocytes have been identified as major xenobiotic stress in invertebrates. Various environmental toxins are capable of initiating alteration in the innate phagocytic response and cytotoxicity of blood cells. Lysosomes of invertebrate haemocytes are functionally involved in intracellular destruction of environmental pathogens. Toxins like arsenic, pyrethroid pesticides, azadirachtin and washing soda were reported to increase the relative fragility of lysosomal membranes of immunocytes. This often leads to impairment in the efficacy of invertebrates to destroy pathogen under the exposure of pollutants. Xenobiotics like pyrethroid pesticides have been recorded to affect apoptosis and necrosis of invertebrate immunocytes. Selected toxin-induced morphological damages of heart, gill, digestive gland, mantle and antennae may result in the overall impairment in homeostatic levels of invertebrates inhabiting the polluted environment. Global environment, in recent times, is under the serious threat of contamination by diverse chemical compounds of unknown or less known toxicity. A thorough ecotoxicological analysis at cellular and molecular levels needs to be carried out in invertebrates occupying the different realms of the planet in future

Broadband wavelength-selective reflectance and selective polarization by a tip-bent vertically aligned multi-walled carbon nanotube forest

The tunable optical properties of the bulk structure of carbon nanotubes (CNT) were recently revealed as a perfect black body material, optically reflective mirror and solar absorber. The present study demonstrates an enhanced optical reflectance of up to similar to 15% over a broad wavelength range in the near infrared region followed by a mechanical modification of the surface of a bulk CNT structure, which can be accounted for due to the grating-like surface abnormalities. In response to the specific arrangement of the so-formed bent tips of the CNT, a selective reflectance is achieved and results in reflecting only a dominant component of the polarized ight, which has not been realized so far. Modulation of this selective-optical reflectance can be achieved by ontrolling the degree of tip bending of the nanotubes, thus opening up avenues for the construction of novel dynamic light polarizers and absorbers

Water-responsive carbon nanotubes for selective detection of toxic gases

Ammonia plays an important role in our daily lives and hence its quantitative and qualitative sensing has become necessary. Bulk structure of carbon nanotubes (CNTs) has been employed to detect the gas concentration of 10 ppm. Hydrophobic CNTs were turned to hydrophilic via the application of a ramp electric field that allowed confinement of a controlled amount of water inside CNT microstructure. These samples were then also used to detect different gases. A comparative study has been performed for sensing three reducing gases, namely, ammonia, sulphur-di-oxide, and hydrogen sulphide to elaborate the selectivity of the sensor. A considerable structural bending in the bulk CNT was observed on evaporation of the confined water, which can be accounted to the zipping of individual nanotubes. However, the rate of the stress induced on these bulk microstructures increased on the exposure of ammonia due to the change in the surface tension of the confined solvent. A prototype of an alarm system has been developed to illustrate sensing concept, wherein the generated stress in the bulk CNT induces a reversible loss in electrical contact that changes the equivalent resistance of the electrical circuit upon exposure to the gas. (C) 2015 AIP Publishing LLC

A report of hailstorm damage to two species of freshwater sponge (Demospongiae: Haplosclerida: Spongillidae) populations of West Bengal, India

Selected freshwater bodies in Jagaddal of North 24 Parganas in West Bengal, India are inhabited by two species of sponge, Eunapius carteri (Bowerbank, 1863) and Spongilla alba (Carter, 1849) (Porifera: Demospongiae: Spongillidae). Most of these wetlands are perennial ponds without a history of aquaculture and toxin contamination. On 22 March 2014, the entire area of Jagaddal experienced an unprecedented hailstorm associated with a sharp decline of environmental temperature from 35 0C to 21 0C within 10–15 minutes. The hailstorm associated with torrential rain lasted for about 30 minutes. The natural habitat of the sponge was visited after six hours of the hailstorm in open day light conditions. During the field investigation, we recorded large-scale damage to the populations of E. carteri and S. alba. Macroscopic observation revealed that the fragmentation of body masses were also associated with cellular disintegration of the external surface. Sponge cells were experimentally dissociated from the sponge fragments and subjected to dye exclusion assay. A vital dye (trypan blue) exclusion assay of sponge fragments confirmed a high degree of mortality of the cells of E. carteri and S. alba. Hailstorm associated with the decline of environmental temperature down to 21 0C resulted in the mass destruction of these two species of sponges in their natural habitat. Any unprecedented and acute change in the climatic and hydrological parameter may lead to physiological adversity in the freshwater sponge. Subsequently, recovery from cold shock and mechanical stresses was overcome and a regeneration of sponge specimens was recorded within a period of around six months from the date of the hailstorm. </div

Giant actuation in bulk carbon nanotubes under coupled electric and magnetic fields

We report an enhanced actuation in bulk carbon nanotubes (CNTs) under coupled electric and magnetic fields, which is much higher than that evaluated in the presence of individual fields. Coupled electric and magnetic fields induce a directional actuation demonstrating a transformation from polarity independent to dependent actuation behavior of CNTs. Both qualitative and quantitative analyses are performed to understand this transformation in the bulk CNTs. Moreover, actuations along radial and axial directions of CNTs have also demonstrated a similar directional behavior

Diffusion of Solvent-Separated Ion Pairs Controls Back Electron Transfer Rate in Graphene Quantum Dots

In the present study, the stability of the photogenerated, solvent-separated charged states of graphene quantum dots (GQDs) in the presence of <i>N</i>,<i>N</i>-diethylaniline (DEA) has been evaluated in a series of organic solvents. The results indicate that the rate constant for back electron transfer (<i>k</i>_BET) from GQD radical anion to DEA radical cation is diffusion-controlled. As a result of the diffusion-controlled back electron transfer (BET), <i>k</i>_BET exhibits an inverse exponential relation to (a) the viscosity coefficient (η) of the solvent and (b) the average radius of the graphene quantum dots. An analytical expression for the diffusion-controlled back electron transfer rate constant has been formulated. The dependence of <i>k</i>_BET on the diffusion of solvent-separated ion pairs has been evaluated for the first time for quantum dot systems and the results provide an efficient method for enhancing the lifetime of the photogenerated charge-separated states from graphene quantum dots. The present findings can potentially improve the performance of GQD-based photovoltaic and optoelectronic devices

Expanded polystyrene microplastic is more cytotoxic to seastar coelomocytes than its nonexpanded counterpart: A comparative analysis

Microplastics (MPs) are established contaminants of coastal ecosystem. Present investigation is aimed to assess comparative toxicity of polystyrene microplastic (PS-MP) and expanded polystyrene microplastic (EPS-MP) in the coelomocytes of Astropecten indicus, a common seastar of Digha coast of Bay of Bengal, India. Coastal water of Digha, a tourist spot of attraction, bears the ecotoxicological risk of contamination by various agents including expanded and nonexpanded microplastics of industrial origin. Coelomocytes of seastar perform multiple physiological functions including pathogen engulfment, cytotoxicity and respiratory gas exchange and considered as immunoeffector cells in echinoderms. We report an adverse shift in total count, phagocytic response, cytotoxicity and oxidative potential of the coelomocytes of A. indicus under the exposures of 0.5 and 1 mg L−1 PS-MP and EPS-MP for 7 and 14 d. Experimental data suggested a higher level of cytotoxicity of EPS-MP in coelomocytes in comparison to that of PS-MP. Seastar is considered as a keystone species, which plays an important role in maintaining the functional homeostasis of coastal ecosystem. Unrestricted contamination of coastal water by MPs may lead to a persistent immunophysiological stress in seastar. Experimental endpoints may be considered as effective monitoring tool to assess ecotoxicity of MPs in seastar and alike organisms sharing the same habitat

Coordination-Induced Emissive Poly-NHC-Derived Metallacage for Pesticide Detection

Developing sensitive, rapid, and convenient methods for the detection of residual toxic pesticides is immensely important to prevent irreversible damage to the human body. Luminescent metal–organic cages and macrocycles have shown great applications, and designing highly emissive supramolecular systems in dilute solution using metal–ligand coordination-driven self-assembly is demanded. In this study, we have demonstrated the development of a silver–carbene bond directed tetranuclear silver(I)-octacarbene metallacage [Ag4(L)2](PF6)4 (1) based on an aggregation-induced emissive (AIE) cored 1,1′,1″,1‴-((1,4-phenylenebis(ethene-2,1,1-triyl))tetrakis(benzene-4,1-diyl))tetrakis(3-methyl-1H-imidazol-3-ium) salt (L). A 36-fold enhanced emission was observed after metallacage (1) formation when compared with the ligand (L) in dilute solution due to the restriction of intramolecular motions imparted by metal–ligand coordination. Such an increase in fluorescence made 1 a potential candidate for the detection of a broad-spectrum pesticide, 2,6-dichloro-nitroaniline (DCN). 1 was able to detect DCN efficiently by the fluorescence quenching method with a significant detection limit (1.64 ppm). A combination of static and dynamic quenching was applicable depending on the analyte concentration. The use of silver–carbene bond directed self-assembly to exploit coordination-induced emission as an alternative to AIE in dilute solution and then apply this approach to solve health and safety concerns is noteworthy and carries a lot of potential for future developments