Polymeric Hydrogels as Smart Biomaterials by Susheel Kalia

Author:Susheel Kalia
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

In view of pharmacological importance related with antiulcer properties of sterculia gum and alginate, Singh et al. [75] have formulated sterculia gum-alginate beads and floating sterculia gum-alginate beads containing an antiulcer drug, pentoprazole using calcium chloride (CaCl2) as ionotropic cross-linker. After preliminary evaluation, optimized formula of Ca2+ ion cross-linked sterculia gum-alginate beads of pentoprazole was considered as polymer blends of 2 % w/v sodium alginate, 1.25 % w/v sterculia gum, and 0.1 M CaCl2. To prepare the floating sterculia gum-alginate beads of pentoprazole in this work, the effervescent technique was employed. These Ca2+ ion cross-linked sterculia gum-alginate floating beads of pentoprazole were prepared using 2 % w/v calcium carbonate (CaCO3) in the sterculia gum–sodium alginate polymer blend solutions (2 % w/v sodium alginate and 1.25 % w/v sterculia gum). The sterculia gum–sodium alginate polymer blend solutions were added dropwise to the 0.1 M CaCl2 containing 10 % acetic acid (v/v). In case of the Ca2+ ion cross-linked sterculia gum-alginate floating beads of pentoprazole, both external and internal gelations occurred. Upon contact with an acidic medium, ionotropic gelation through Ca2+ ions took place to facilitate a gel barrier at the surface of the formulated beads. The CaCO3 effervesced with releasing carbon dioxide (CO2) and Ca2+ ions. The released CO2 was entrapped into the gel network to provide buoyancy to those formulated beads. Then, the Ca2+ ions interacted with the –COOH groups of these two anionic polysaccharides (i.e., sterculia gum and sodium alginate) to produce Ca2+ ion cross-linked three-dimensional gel network that restricted further diffusion of CO2.

The shape of these Ca2+ ion cross-linked sterculia gum-alginate beads of pentoprazole was found spherical as the sodium alginate concentration increased in the polymer blend solutions. This can be attributed that the mean diameter of these beads increased due to increment in microviscosity of the polymer blend with the increment in sodium alginate concentrations in the polymer blend solutions. However, sterculia gum concentration in the polymer blend solutions and the cross-linker concentration did not influence the bead shape and diameter. The mean diameter of the optimized Ca2+ ion cross-linked sterculia gum-alginate floating beads of pentoprazole was found as 1.35 ± 0.30 mm. The mean diameter increment with the incorporation of CaCO3 in the formula might be due to the cause that when CaCO3 reacted with acetic acid present in the cross-linking medium, CO2 was formed and escaped from the bead matrix. The scanning electron microscope (SEM) image of optimized Ca2+ ion cross-linked sterculia gum-alginate non-floating beads of pentoprazole possessed rough surface (Fig. 1). On the other hand, SEM image of optimized Ca2+ ion cross-linked sterculia gum-alginate floating beads of pentoprazole prepared through the incorporation of CaCO3 confirmed comparative smooth surface (Fig. 2). The Ca2+ ions from CaCO3 might have contributed to the homogeneous sterculia gum-alginate beads formation, which may be responsible for smooth surface of the beads. This might be due to the bursting effect of larger amount of CO2 evolved before the walls get sufficiently hardened.

Fig. 1SEM image of optimized Ca2+ ion cross-linked sterculia gum-alginate non-floating beads of pentoprazole at different magnifications a ×86 and b ×2500 [75].

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