Nanotechnology as a tool to utilize the nutraceuticals in aquafeed

Nanoparticles can be used as feed additives to improve livestock production. Minute micelles (nanocapsules) are used as carriers for essential oils, flavor, antioxidants, coenzyme Q10, vitamins, minerals, and phytochemicals to improve their bioavailability (Elamin, 2006). Encapsulating the nanoparticles of active ingredients (e.g., polyphenols, minerals, and micronutrients) protects them from oxidation and getting to the taste receptor site, thus reducing their undesirable off-tastes in the finished application.

Aquaculture is the burgeoning and improvident food production sector globally. While aquaculture nutrition remains essential to its success, a noticeable deviation is occurring from the traditional approach that was looking forward to growth with greater emphasis on health. Disease prevention is vital for enhancing growth. Consequently, the aquafeed industry is taking up the concept of components in the feed that provide health benefits beyond mere nutrient provision. In recent years, nutraceuticals are gaining importance in the aquaculture sector. The term “Nutraceuticals” was coined from “Nutrition” and “Pharmaceutical” in 1989 by Stephen De Felice, Founder and Chairman of the Foundation for Innovation in Medicine (FIM), Crawford, New Jersey.

The word nanotechnology is derived from the Latin nanus, meaning dwarf. Nanotechnology has a wide range of applications in aquaculture and could significantly help transform this industry. Between its current applications, we can find the detection and control of pathogens, water treatment, sterilization of ponds, and efficient delivery of nutrients and drugs. Nanotechnology is defined as the understanding and management of matter at the nanoscale. Typical nanotechnology utilizes structures under 100 nanometers in size, more than 1000 times narrower than the diameter of a human hair. Additionally, using nanomaterials for delivery systems can improve the nutritional profiles of feed and the feeding conversion rate. These advantages enhance feed efficiency, reduce waste and financial burden, and improve production yield and quality. Nanotechnology is also applied to strengthen bioavailability (including functional compounds), encapsulation, and monitoring the release of microencapsulated antimicrobials in packaging, slowing down the decomposition process and improving the stability and shelf-life of delicate ingredients in aquafeeds. Hence, the main goal of this review is to focus on a broad manuscript of information about the application of nanotechnology in fish feed additives.

MECHANISM OF ACTION OF NANOPARTICLES
The mechanisms of action of the nanoparticles are as follows below:
• Increase the surface area available to interact with biological support
• Prolong compound residence time in GIT
• Decrease the influence of intestinal clearance mechanisms
• Penetrate deeply into tissues through fine capillaries
• Cross epithelial lining fenestration (e.g., liver)
• Enable efficient uptake by cells
• Efficient delivery of active compounds to target sites in the body

USE OF NANOPARTICLES AS FEED ADDITIVES
Nanoparticles can be used as feed additives to improve livestock production. Minute micelles (nanocapsules) are used as carriers for essential oils, flavor, antioxidants, coenzyme Q10, vitamins, minerals, and phytochemicals to improve their bioavailability (Elamin, 2006). Encapsulating the nanoparticles of active ingredients (e.g., polyphenols, minerals, and micronutrients) protects them from oxidation and getting to the taste receptor site, thus reducing their undesirable off-tastes in the finished application.

The application of nanoparticles as feed additives is classified as follows:
1. As a growth promoter:
A sound understanding of the concept and importance of growth is central to meaningful improvement/progress in fish nutrition. Growth is essential in estimating fish populations’ production, stock size, recruitment, and mortality in fisheries and aquaculture. Several nanomaterials are currently being used as feed supplements.

Selenium is an essential micronutrient that enhances fish’s growth and physiological health by acting as an antioxidant and a catalyst for growth and hormone production. The synergic effect of dietary nano-selenium (nano-Se) and vitamin C reports on increased growth of mahseer fish (Tor putitora). Also, a study on common carp with different levels of nano-selenium showed improved growth performance (regarding final weight and weight gain) and higher selenium contents in the liver and muscle in a fish-fed diet supplemented with nano-selenium.

Zinc: Dietary is essential for the growth and health of higher animals, including fish. Zinc promotes growth, and it cannot be stored in animal bodies. Its deficiency could lead to frequent infections, poor appetite, and taste and smell-associated problems. Regular dietary zinc intake is, therefore, a necessity. The supplementation of nano zinc oxide in the feed of grass carp (Ctepharyngodon idella) shows a significant increase in growth and hematological parameters.

Iron: Dietary iron supplementation for fish is essential because most natural bulk iron sources do not meet dietary requirements due to low solubility and bioavailability. The study of the growth-promoting potential of iron oxide nanoparticles shows an improvement in growth and survival rate in Freshwater prawns (Macrobranchium rosenbergiii).

2. A stress resisstors:
Oxidative stress-related minerals selenium (Se), zinc (Zn), and manganese (Mn) should be supplied in micro diets for better survival of larvae. Since the larvae were less resistant to stress, adding Zn, Mn, and Se in nanometals has improved stress resistance and bone mineralization.

3. As an antioxidant promoter:
A wide range of short-chain fatty acids (SCFAs) and their salts can be efficiently used in fish diets to improve their health, antioxidant status, immunity, and overall performance. Among SCFAs, butyric acid and its salt sodium butyrate have attracted the vision and interests of researchers to be used as excellent growth promoters, antioxidants, and immunostimulants. The dietary supplementation of sodium butyrate nano particles modulated the fish antioxidant defense mechanism by significantly upregulating antioxidant enzyme genes (gpx and sod).

4. As an immune response promotor:
Copper is a critical mineral. It is used as an alternative to antibiotics that affect animal performance development by influencing the metabolism of nutrients as it affects the immune system, which results in metabolic changes known as immunological stress. The administration of copper nanoparticles will increase lymphoid organs, which indicates an improved immune status.

DELIVERY METHODS OF NANOPARTICLES IN FEED
Nano-additives can also be incorporated in micelles or capsules of protein or another natural food/feed ingredient.

Micelles
Liquid droplet technology named ‘Nano-sized Self-assembled Liquid Structures (NSLS) involves encapsulation and release of particles in cells. Micelles are tiny spheres of oil or fat coated with a thin layer of bipolar molecules of which one end is soluble in fat and the other in water. Such nanocapsules can contain healthy omega-3 fish oil (ώ3 fatty acids) with a strong and unpleasant taste and only release in the stomach. The particle size of minerals as feed additives in nanoparticle form is claimed to be smaller than 100 nanometers, so they can pass through the stomach wall and into body cells more quickly than ordinary minerals with larger particle sizes. The micellar particles encapsulate nutraceuticals (beta-carotene, CoQ10, docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) and other compounds) into 30 nm self-assembled spheres.

Micelles are organic nano particulates that can be assembled by the thermodynamically driven process known as self-assembly. Micelles made in this way can encapsulate non-polar molecules such as lipids, flavors, antimicrobials, antioxidants, and vitamins. Compounds generally insoluble or only sparingly soluble in water can be made water soluble, extending their use in foods/feeds and potentially changing their bioavailability once ingested. The micelles are made from lipid molecules and have a unique hydrophobic interior. The NSLS particles are reported to act as vehicles for compounds to be absorbed into the bloodstream from the gut more readily, increasing their bioavailability. Liposomes are another example of micelles and can be used to encapsulate both water and lipid-soluble compounds. The dissolution of fat-soluble nutrients in water-based drinks is one of the critical applications of liposomes. Liposomes can be produced in different sizes (10-500nm) and engineered to have extra stability and surface charges under other environmental conditions. Liposome technology can target specific sites within a food/feed product for enzymatic degradation.

Nanoemulsions
Nanoemulsions are thermodynamically stable emulsions compared to conventional emulsions under a range of different conditions. This is due to their small size (typically 50 to 500nm compared to 1200nm) and monodispersity. They can be diluted with water without changing the droplet size distribution. The type of surfactant used to formulate a nanoemulsion is critical to the stability of the final emulsion.

Preparations of nanoemulsions can be used to encapsulate functional food/feed components at oil/water interfaces or throughout the continuous phase of the system. The applications of nanoemulsions include delivery of active compounds in the body, stabilization of biologically active ingredients, extended shelf-life due to increased stability, and increased viscosity at lower concentrations of the oil phase. The technology has been combined with advanced processing technologies to develop novel microencapsulated products that allow the controlled release of food/feed bioactive in the gastrointestinal tract. These products may be ready-to-drink or powdered formulations fortified with functional ingredients from various sources.

DELIVERY OF DIETARY NANO PARTICLE SUPPLEMENTS AND NUTRACEUTICALS IN FISH
One of the main underlying concepts behind the idea that nanoparticles can improve fish development is based on their ability to increase the quantity of nutrients absorbed across the digestive tract. Micronutrients, in the form of nanoparticles incorporated in aquaculture feeds, can penetrate cells more efficiently and raise the absorption rate.

INCREASE IN BIOAVAILABILITY BY ENCAPSULATION
Nanotechnology has also been employed to improve the bioavailability and increase the retention span of natural bioactive compounds by encapsulating them with nanoparticles. For example, encapsulation of curcumin in nanoparticles has been reported in micelles, liposomes, and hydrogels, among others.

ROLE OF NANOPARTICLES IN THE PROPERTIES OF FEED
On the other hand, besides improving the stability and bioavailability of food ingredients, nanoparticles can modify the fish food’s physical attributes. Even small inclusions of nanomaterials can dramatically enhance the physical properties of food pellets. For example, including single-walled carbon nanotubes in trout diets results in a hard shell that maintains its integrity in the water. This is important to reduce pollution and food wastage in aquaculture systems due to inappropriate buoyancy, poor food stability, or texture of the pellets, which causes significant losses inside this industry. Thus, nano-formulation development has been heavily investigated in the industry. A fundamental characteristic of these systems is their suitability for different uses, such as the delivery of antibiotics, vaccines, pharmaceuticals, and nutraceuticals.

Current research has focused on using different types of biopolymers in the aquaculture sector. It was found that vitamin C encapsulated in chitosan-based nanoparticles raised the levels of vitamin C in the serum of rainbow trout (O. mykiss) when incorporated in the feed, also increasing the innate immune response, evidenced by the levels of lysozyme and hemolytic serum complement activities, compared to vitamin C and chitosan control groups.

CONCLUSION
Nanotechnology offers a range of valuable applications in aquaculture, including stabilizing proteins, DNA, and RNA, delivering small molecules, prolonging drug circulation, and modifying drug transport. These capabilities have practical uses in aquaculture nutrition, fish breeding, drug development, and fish health management. Additionally, nanomaterials can enhance wastewater treatment for safer aquaculture water and discharge. Regarding animal health, developing “nano vaccines” with improved delivery methods for small aquaculture animals like fish larvae and shrimp can be both cost-effective and beneficial for animal welfare. Exploring eco-friendly approaches that align with environmental sustainability is crucial to fully harnessing nano-delivery potential in aquaculture drugs and nutraceuticals.

References
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About Thangaraju Thiruvasagam
Thangaraju Thiruvasagam, Ph.D. is a research scholar in the Department of Fish Nutrition and Feed Technology at Institute of Fisheries Post Graduate Studies of Tamil Nadu Dr. J. Jayalalithaa Fisheries University (TNJFU), India. Thiruvasagam has done the research on shrimp nutrition (Penaeus vannamei) with supplementation of nutraceuticals like taurine and cholesterol.

About Dr. Amit Ranjan
Dr. Amit Ranjan is an Assistant Professor in the Department of Fish Nutrition & Feed Technology at the Institute of Fisheries Post Graduate Studies of Tamil Nadu Dr. J. Jayalalithaa Fisheries University (TNJFU), India. His research focus is on fish and shrimp nutrition, where he conducts both strategic and applied research. With his extensive experience in commercial culture of shrimp and freshwater fish, he has published several research papers in international peer-reviewed journals and serves as a reviewer for over 30 international peer-reviewed journals.