Starch-based capsules

Starch based plastics constituting about 50% of the bioplastics market, thermoplastic starch, such as plastarch material, currently represents the most important and widely used bioplastic. Pure starch possesses the characteristic of being able to absorb humidity, and is thus being used for the production of dmg capsules in the pharmaceutical sector. 

A very recent development is encapsulation of actives in colloidosomes [16, 41]. The method is analogous to liposome entrapment. Selectively permeable capsules are formed by surface-tension-driven deposition of solid colloidal particles onto the surface of an inner phase or active ingredient in a water-in-oil or an oil-in-water emulsion composed of colloidal particles. Initially synthetic polymer microparticles were used but more recently a natural alternative has been described based on small starch particles. After spray-drying, redispersible emulsions can be formed. 

Based on the fact that mefenamic acid reacts quantitatively with tV-bromosuccinimide (NBS) in an acidic medium, Hassib et al. [8] reported the titrimetric determination of mefenamic acid. A solution of mefenamic acid in acetic acid (0.02% m/V) was prepared. A volume of this solution containing 1.5-3.5 mg of mefenamic acid was allowed to react with 40 mL of 0.05 M NBS solution for 10 min in the dark (temperature of 25 2°C). Potassium iodide solution (10 mL) was added, and the solution was titrated with 0.01 N sodium thiosulfate to the starch end-point. A blank determination was carried out. For the determination of mefenamic acid in the capsules, the contents of 20 Ponstan capsules were mixed thoroughly and an accurately weighed portion of the mixed powder (nominally containing 25 mg of mefenamic acid) was extracted with diethyl ether (3 x 10 mL). The residue remaining after evaporation of diethyl ether was dissolved in acetic acid, and the procedure was continued as described for the determination of mefenamic acid. 

Matrix mini-tablets based on starch/microcellulose wax mixtures have been described (31,32). The possibility with these and other mini-tablets is that different dose levels can be administered by changing the number of mini-tablets within a capsule for adults or using single units for children. It is also possible to utilize fast-dissolving mini-tablets to prepare liquid dosages extemporaneously. 

The major advantages of ionotropic gelation are that capsules are easily prepared in aqueous solutions and at room temperature, enabling the method to be used for heat-labile materials. The drawback of this method includes very low payload, unacceptable cost-in-use, large capsules size, limited range of waU materials and undesirable amounts of substantial polymers incorporated into the foods. In order to improve this technique, hydrophobicaUy modified starch, epimerized alginate and polyelectrolyte-based multilayer microcapsules can be used to increase the payload. 

---