Nanotechnology has emerged as a promising solution opening the door to new possibilities. Besides conventional toxicological assays, scientists are also using cellular cytotoxicity, apoptosis as well as bioinformatics based interactive tools to narrate nanotoxicity and its remediation applying green nanoparticles in bacteria and fish model.

Intensive aquaculture practice leads to eutrophication of pond accumulating excess nutrient load. Global climate change is posing a serious threat to aquaculture due to high temperature, increased methane, and CO2 level etc.

“High water temperature has a direct impact on water quality, plankton community, survival of larva and juveniles, as well as the reproductive potential of fish.”

Likewise, fish health management appeared as another challenging problem. Deteriorating environmental quality and impact of climatic change has led to a significant upsurge of pathogens and diseases in aquaculture.

“Nanotechnology has emerged as a promising solution opening the door to new possibilities.”

Nanotechnology is the science of developing and applying materials at nanoscale dimensions (1-100 nm) with unique properties paving the way for novel applications. With nanotechnological intervention, reports are mounting on its toxic impacts on aquatic organisms including fish.

Application of nanotechnology in different frontiers of aquaculture

Nanotechnology for aquaculture structure and fishing system

Nanoparticles like silver, zinc oxide, copper oxide, and iron oxide have been found to have antimicrobial and antibiofilm functions. Fish aquariums, cemented cisterns can be sterilized if their walls would be immobilized with nanoparticles.

Development of hybrid nanocomposite membranes consisting of nanosilver and polyamide (PA) were shown to possess antimicrobial and anti-biofouling effect on Pseudomonas sp. along with water flux and salt rejection effect.

Hence, nanosilver-composite can be applied to design multifunctional membranes serving as filtration systems in diversified polluted water. A schematic diagram is designed describing multiple impacts of nanoparticles for pond and fishing structure Figure 1.

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Nanotechnology in nutritional aquaculture

Nanoparticle can alter feed consumption pattern by adding flavor, color, or attractants etc. Some water-insoluble vitamins, carotenoids, can be solubilized by processing with nanoparticles and used as a dietary supplement for better bioavailability.

Different nanoparticles can function as growth promoters and immunomodulators when supplemented with fish diet in a microscale. Supplementation of selenium nanoparticles with basal diet demonstrated an improvement in weight gain, antioxidant profile, and muscle bioaccumulation in crucian carp. Nanosilver has been found to improve overall growth, protease, and metalloprotease activity in zebrafish (Danio rerio).

Similarly, a positive trend of growth pattern was reported in grass carp (C. idella) and common carp (Cyprinus carpio). Zinc nanoparticle-induced growth and immunomodulation were also reported in Pangasius hypophthalmus under combined abiotic and biotic stress conditions Nano-encapsulation protects the sensitive and precious bioactive elements of food from diverse, adverse environmental circumstances.

“They involved in eradication of incompatibilities and masking objectionable odor/taste from solubilization and also helps in the unmasking of taste.”

Applying different nanotechnology-based methods, i.e. oil-in-water-in-oil double emulsions, water-in-oil-in-water, or solid lipids can be designed for effective encapsulation.

Potential of chitosan-based nanocapsules showed the capacity for entrapment of water-soluble compounds like Ascorbic acid (AA) by making a positively charged complexes at nanoscale range. Chitosan-based polymeric nanoparticle acted as an efficient vehicle for oral delivery of AA and may be applied for other important active compounds applied in aquaculture.

Essential nanoparticles can be delivered to fish spawn, fry and fingerling through a primary member of the food chain like zooplanktons or directly through bathing route. However, toxicity aspects of nanoparticles application must be assessed before its potential inte- gration into the food chain.

Nanotechnology for gonadal maturation and breeding of fish

Injection of stimulating hormones like human chorionic gonadotropin (HCG), etc. are delivered from the pre-spawning phase, and fish are met with handling stress, occupational pain, etc. Nano-encapsulated hormonal delivery found to be a more efficacious alternative to this approach.

An improved and controlled nano-delivery system was demonstrated to surpass the fundamental dilemma of precise life span of leuteinizing hormone-releasing hormone (LHRH) in blood circulation averting the need of multiple applications of injections in fish.

Nanotechnology in aquaculture biotechnology

Nanoparticles provide an attractive receptor and function as scaffolds for nucleic acids. In fisheries, nanofabricated technology can be utilized in DNA and protein microarray for analyzing genetic polymorphism, new biomarker discovery, and differential gene expression, etc. Biochips and microfluidic chips can accomplish high throughput screening and can be employed for developing DNA and protein marker- dependant detection as well as identification systems.

Nanoparticles assist in designing novel and innovative gene transfer methods in fish (Figure 2).

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Small interfering RNA (siRNA) has emerged as a great hope in molecular therapeutics. Nanoparticles
possess unique properties to develope improved siRNA-based delivery systems. A schematic diagram of nanoparticle-mediated siRNA delivery in the fish system is presented as Figure 3.

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Nanotechnology in fish disease control

Nanotechnology can contribute significantly in these spheres through novel methods as well as restructuring conventional technology. In this context, a schematic diagram is presented describing nanoparticles inspired disease management in fish Figure 4.

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The occurrence of disease is one of the major menace to intensive aquaculture system. An antibody-based, highly sensitive immunodiagnostics protocol has been designed by attaching nanoscale gold with alkaline phosphatase (ALP) conjugated secondary antibody titre against white spot syndrome virus (WSSV) strain in shrimp. Nanosensors are also effective and easy solutions to identify pathogens.

Different nanosensors can be effectively used to detect important aquaculture viruses. The antimicrobial and prophylactic properties of nanomaterials like nanosilver, zinc oxide nanoparticles are already exploited to reduce the pathogenic load in the aquaculture system.

“This unique nanomedicinal phenomenon is non-specific, universal, and widely applicable. Antibacterial potentials of nanoparticles like titanium-di-oxide, copper oxide are under trials and would be useful nanomedicines for fish.”

Graphene appeared as a commercially attractive, cheap, renewable nanomaterial. Oxidized form of graphene is easy to process and dispersible in water. Graphene oxide (GO) exhibited inhibitory effect against important aquatic pathogens.

Different herbal and phyto-extracts are applied as potential drug in treating fish diseases. Different nanoparticles are being synthesized using medicinal plant/herbal extracts at optimized hydrodynamic conditions, and a composite of the phyto-nanoformulation are delivered as drugs with synergistic impacts.

Nano-delivery of drugs are attributed with novel properties like sustained release, regulation and control of size, shape, dispersity, and surface charge of targeted materials, location specific, multi-route delivery processes, and regulated degradability of nanocarrier.

Nanotechnology for fish quality testing

The freshness of fishery products is a real health and quality concern. To address this issue, a quantum dot-based nanosensor has been designed. The electrochemical output displayed a higher sensitivity, quicker response time, and extensive linear range.

Formalin appears as a great menace on modern days ‘fish-food safety’. Formaldehyde nano-biosensor was designed applying an enzyme (formaldehyde dehydrogenase) and nanomaterial (carbon nanotubes, chitosan) for precisely detecting this impending human health hazard.

Biogenic amines such as histamine, cadaverine etc. are found in seafoodand produced by action of bacterial decarboxylase on a free amino acid. A nanosensor was developed using stable magnetic mobile crystalline material-41, cetyltrimethylammonium bromide, and Fe3 O4 nanoparticles to detect the linear concentration ranges of mentioned amines TTX, as a potent sodium channel inhibitor, found to be 1000 times more toxic than potassium cyanide.

“The optical phenomena of tetrodo-toxin (TTX) were examined using nanoparticle arrays-assisted surface-enhanced Raman scattering (SERS).”

These arrays were designed to apply nanosphere lithography and a metallic lift-off process for controlling particle shape, size and spacing.

Nanomaterial synthesis from fishwaste and their bioactivity

Throughout the world, a major part of (30-35%) fin and shellfish are discarded as unconsumed waste, which otherwise also works as a center of pathogenic infestation and spread foul smell. Unconsumed fish-waste has been engineered to develop nanomaterials to open up an attractive market for discarded materials that provide 100% value to productivity as well as sustainablity in aquaculture.

Nano-remediation of the aquatic system

The sustainability of aquaculture depends on the quality of the aquatic medium. Development of novel forms of nanomaterials triggers new achievements in the remediation of aquatic environment that might exclude the minute contaminants from water and can design “reactive surface coatings” or “smart materials” with specificity towards certain toxicants (Figure 5).

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Aspects of nano-toxicity

As fish lives in aquatic environment, every nanoparticle pass through a water medium before inducing its beneficial impact. Silver in the colloidal form were found to be more toxic than suspended solid form, and increase in nanoparticles size could reduce the toxicity effect as studied in rainbow trout.

Nanomaterials showed a great difference in their toxicity impact on the fish system. Selenium nanoparticles showed higher bioavailability and toxicity than selenite in Medaka fish (Oryzias latipes). In aquatic medium, addition of nanomaterials leads to direct gill exposure.

Specific pH of different body fluids may influence nanomaterials to agglomerate suggesting their adherence to blood cells.”

Nanoparticle induced toxicity in fish can be measured through routine protocols or applying high-through put screening (HTS) technique. Highly automated high-throughput screening (HTS) platforms have been developed using zebrafish embryos as well as hatching phe- nomena for quickly assessing the hazard quotient of metal oxide nano- particles.

Molecular nano-toxicity investigation of green magnesium and calcium oxide nanoparticles in zebrafish demonstrated that significant dysregulation in oxidative stress tending towards apoptosis occurred due to nanoparticle internalization and their interaction with important regulatory cellular proteins.

Conclusion

Nanotechnology research and development holds unique, multiple promises to improve and innovate conventional aquaculture practices along with a handful of challenges.

Biodegradability, agglomeration, and precipitation are crucial fac- tors to consider in the application of nanoparticles at aquaculture. The biodegradable nano-carrier is vital for delivering bioactive compounds, important ingredients etc. for higher efficacy, greater bioavailability.

It will boost overall aquaculture- management processes through the enrichment (feed, medicine, fertilizer, etc.) resulting in minimal dumping of ingredients and will be adsorbed as well as degraded rapidly to trigger the natural biofortification cycle.

“The application of nanoparticles also reduces gaseous contaminants, un- wanted spreading of algae and diatom in the aquatic ecosystem.”

However, the hazard of using nanoparticles in aquafarming is tricky to decide due to the natural complexit yof the aquacultural system and the non-availability of research database.

Moreover, the benefits of nanotechnology are worth pursuing and primary information of hazards should not be a hurdle in the responsible use of nanotechnology for sustainable, nextgeneration aquaculture.

This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “NANOTECHNOLOGY: A NEXT-GENERATION TOOL FOR SUSTAINABLE AQUACULTURE” developed by: BIPLAB SARKAR-Indian Institute of Agricultural Biotechnology, ARABINDA MAHANTY National Rice Research Institute, SANJAY KUMAR GUPTA- Indian Institute of Agricultural Biotechnology, ARNAB ROY CHOUDHURY-Indian Institute of Natural Resins and Gums, AKSHAY DAWARE Tripura University, y SURAJIT BHATTACHARJEE- Tripura University.
The original article was published on AUGUST, 2021, through AQUACULTURE under the use of a creative commons open access license.
The full version can be accessed freely online through this link: https://doi.org/10.1016/j.aquaculture.2021.737330.

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