Effects of the Starch Types and the Grafting Conditions on the In Vitro Mucoadhesiveness of the Starch-graft-Poly(Methacrylic Acid) Hydrogels

In the present study, grafting of poly(methacrylic acid) (PMAA) onto various types of starches (maize; rice; wheat; potato) is realized in the aqueous media for the first time using methacrylic acid as monomer and ammonium cerium-IV-nitrate as initiator system. The effects of the gelatinization pretreatment and the use of a crosslinker in the grafting reactions are investigated. The formation of the starch-graft-poly(methacrylic acid) (S-g-PMAA) is confirmed by Fourier transform infrared spectroscopy analysis. The grafting amounts (GA%) of the S-g-PMAAs are determined. The swelling and the erosion characteristics of the S-g-PMAAs are examined in deionized water and pH = 5 lactate buffer solution as an in vitro vaginal medium. Mechanical and in vitro mucoadhesiveness of the S-g-PMAAs are also investigated using ewe vaginal mucosa. The results demonstrate that the gelatinization pretreatment and crosslinking significantly affect the GA% values, swelling, erosion, mechanical, and mucoadhesive characteristics of the S-g-PMAAs depending on the types of starches. S-g-PMAAs with different mechanical and reasonable mucoadhesiveness can be obtained by manipulating the grafting conditions and using various types of starches. It is concluded that S-g-PMAAs could be appropriate candidates for applications as vaginal drug delivery systems.