Synthesis, characterization and swelling studies of pH responsive psyllium and methacrylamide based hydrogels for the use in colon specific drug delivery

In order to utilize the psyllium husk a medicinally important natural polysaccharide and to develop the novel hydrogels meant for the colon specific drug delivery, we have prepared psyllium and methacrylamide based polymeric networks by using N,N′-methylenebisacrylamide (NN-MBAAm) as crosslinker and ammonium persulfate (APS) as initiator. To study various structural aspects of the polymeric networks thus formed psy-cl-poly(MAAm), these were characterized with SEMs, FTIR, TGA and swelling studies. The swelling studies of networks were carried out as a function of time, temperature, pH and NaCl]. Equilibrium swelling has been observed to depend on both composition of the polymer and nature of swelling medium. Maximum percent swelling 1262 was observed for the polymeric network prepared with 19.45 × 10⁻³ mol/L of NN-MBAAm] at 40 °C in 0.5 M NaOH solution. This article also discusses the release dynamics of tetracycline hydrochloride from the hydrogels, for the evaluation of the drug release mechanism and diffusion coefficients of drug from the polymer matrix. The effect of pH on the release pattern of tetracycline hydrochloride has been studied by varying the pH of the release medium. It has been observed from the release dynamics of drug from the hydrogels that the diffusion exponent ‘n’ have 0.477, 0.423 and 0.427 values and gel characteristic constant ‘k’ have 5.07 × 10⁻², 6.34 × 10⁻² and 6.38 × 10⁻² values, respectively, in distilled water, pH 2.2 buffer and pH 7.4 buffer solution. The values the ‘n’ indicated that the Fickian type diffusion mechanism occurred for the release of tetracycline hydrochloride from drug loaded psy-cl-poly(MAAm) polymers in different release mediums. In Fickian type diffusion mechanism, the rate of polymer chain relaxation is more as compare to the rate of drug diffusion from these hydrogels and release behavior follows Fick’s law of diffusion. In each release medium, the values of the initial diffusion coefficient ‘D_i’ for the release of tetracycline hydrochloride was higher than the values of late time diffusion coefficient ‘D_L’ indicating that in the start, the diffusion of drug from the polymeric matrix was faster as compare to the latter stages.