**2. Alginate, polymer purified from seaweed**

Alginic acid or sodium and potassium alginates (ALG) are one of the biomaterials of the adhesive mucus, due to its cellular compatibility, biocompatibility, biodegradability, SOL transport properties, and chemical versatility, which allow more GEL-changes to adapt the properties. It makes it possible, it has been studied for drug transfer. This substance is prepared from different types of seaweed. The many advantages of this material have led to the increase of the scientific community's interest in alginate as a platform for the promotion of new nanomedicine delivery systems in recent decades. The release of water-soluble drugs from the alginate gel matrix is generally done through diffusion, while the drugs with low solubility in water are released through the erosion of the alginate matrix. The potential of different qualities of pharmaceutical side additives has not been fully evaluated, but alginate is likely to make an important contribution to the development of polymeric delivery systems. Natural polymers such as albumin, gelatin, alginate, collagen, chitosan, etc., and other materials can be used alone or in combination with other polymers to formulate nanoparticles. Natural polymers are often cheaper and are often soluble in water, which is effective in protecting drugs and antigens. Biocompatibility and biodegradability are also important features. In addition, chitosan and alginate polymers are mucus adhesive, which is in line with the approach of developing mucosal vaccines. This group of polymers increases the absorption and biosupply of vaccines by increasing the duration of antigen retention in the target tissue or by affecting the tight connections between cells [16, 17].

Alginate is a natural water-soluble polysaccharide extracted from the cell wall of various species of brown algae, i.e., Laminaria, Macrocystis, and Ascophyllum [18]. In fact, alginate is a linear block polymer of 1b-D-mannuronic acid (M) and a-L-guluronic acid (G); the content of M and G units affects its physical properties and determines its industrial utilization. Therefore, alginates with various sources would have specific M-G contents, and consequently, different physical properties [18]. Inherent hydrophilicity of alginate makes it an excellent gel-forming compound, capable of holding large amounts of water.

The word alginate is derived from the word Algae which means algae has been Alginate has been isolated from the cell wall of various types of brown algae such as Macrocystis pyrifera, Laminaria hyperborea*,* and Ascophyllum nodosum (**Figure 1**). Alginate is also from some bacteria such as Azotobacter vinelandii can be extracted. Alginates of bacterial origin are rich in structural units. Mannuronic acid has a very weak gel-forming property, and in addition, the production of alginate from bacteria is not cost-effective for commercial use, so alginates from seaweed are often used for mass production [19, 20].

Alginate is a polysaccharide extracted from the cell wall of phaeophyceae brown algae and is used in the food industry in the form of sodium, potassium, and calcium alginate salts. Sodium alginate is a viscous gum compound and is widely used in the food industry due to its emulsifying, stabilizing, thickening, gel-forming properties in the presence of polyvalent cations, elasticity, and the formation of preservative edible films [21, 22].

**Figure 1.** *Origin of alginate: (1) Ascophyllum nodosum, (2) Laminaria hyperborea, and (3) Macrocystis pyrifera.*

Placing the alginate film around the food item preserves the water retention capacity and protects the item against microbial and oxidative spoilage [23]. Unlike chemical preservatives, it is biodegradable and compatible with the environment, it has a protein, polysaccharide (gum, etc.), and lipid origin and does not pose a threat to the health of the consumer [24].
