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. The grafting conditions of poly(methacrylic acid) onto four major types of starches and the effects of starch types on the in vitro mucoadhesiveness are investigated for the first time using ewe vaginal mucosa. The findings demonstrate that the grafted starch products with different mechanical and reasonable mucoadhesive characteristics can be obtained by manipulating grafting conditions and using different types of starches.