**2. Natural polysaccharides**

The use of nanotechnology for the delivery of therapeutic agents was put forward by Paul Enrich [6], the proponent of drug loaded magic bullets. Biomedical field uses polysaccharides for the last one half of the century due to its remarkable applications [38]. Nature is an abundant source for natural polysaccharides made its use widely in this field. Most of the drugs used for different types of diseases

cause dangerous side effects. These problems can be reduced by the use of natural biocompatible polymer/polysaccharides as carriers for the drug. Seaweeds provide a better source for available polysaccharides such as carrageenan (iota, kappa, and lambda), alginate, and agar [39].

Monosaccharides combine to form polysaccharides with number of reactive groups that can be easily modified to get various types of polysaccharides. Typical sources of polysaccharide include algae, microorganisms, animals, etc. The positive features of polysaccharides such as higher molecular weight, changing chemical composition and large number of reactive groups gave diversity in its function. Adaptable chemical composition delivers its variety in structure and also in property. Medicinal field exploits these best properties of polysaccharides for the betterment of drug delivery. Drug carriers from polysaccharides make sustainable, cost effective and biodegradable drug carriers. Modification of polysaccharide chains opens a way to target drug to the affected site, altering the solubility, biocompatibility, moisture resistant and particularly reduce the severe side effects from therapeutic agents. Polysaccharides can perform bio adhesion through hydrophilic groups such as carboxyl, hydroxyl and amino groups by making non covalent interaction with biological tissues that elongates residing time. By this the absorption of drug at the particular area can be easily made. In this chapter we discuss niosomal emulsions of alginate, *κ*-carrageenan and gelatin as drug carrier [38, 40, 41].

Alginates are naturally derived polysaccharide block copolymers composed of β-d-mannuronic acid monomers (M-blocks), α-l-guluronic acids (G-blocks) and regions of interspersed M and G units [38, 42]. Divalent cations such as Ca2+ can induce hydrogel formation by polysaccharide chain association in alginates [20]. Carrageenans represent a family of sulphated linear polysaccharides consisting of (1 → 3)-linked β-galactose and (1 → 4)-linked α-d-galactose units mainly extracted from certain red seaweeds of Rhodophyceae family particularly from *Chondrus crispus*, *Eucheuma gigartina*, *Stellate iridaea*, *Hypnea*, *Solieria agardhiella and Sarconema*, which are variously substituted and modified to the 3,6-anhydro derivative, depending on the nature of origin and extraction conditions [43]. Three main types of carrageenans are known: kappa-*κ*, lambda-*λ* and iota-*i*, depending on the number and the position of the ionic sulphate groups. The presence of a suitable cation, typically potassium, or calcium is an absolute requirement for gelation of the carrageenans, especially kappa [44]. Gelatin is a protein derived from denatured collagen that contains high levels of hydroxyproline, proline and glycine. It is useful as a thermally reversible gelling agent for encapsulation [45].

However, we go through the development and characterization of alginate/*κ*carrageenan and alginate/gelatin hydrogel beads and its application in encapsulation of a model hydrophobic potential drug, curcumin. Hydrogel beads were developed via ionotropic gelation. Alginate/*κ*-carrageenan beads were cross-linked with CaCl2-KCl salt solution and alginate/gelatin beads with CaCl2 solution. Drug release behaviour of alginate/*κ*-carrageenan and alginate/gelatin hydrogel beads was compared employing curcumin, which is a natural polyphenolic compound isolated from rhizome of turmeric (*Curcuma longa*) as a model drug [46]. Curcumin is widely known to possess antioxidant [47], antitumor [48], and anti-inflammatory [49] activity. Swelling of the beads and in vitro release of curcumin were studied in phosphate buffered saline (PBS, pH 7.4).
