Evaluation of a conducting interpenetrating network based on gum ghatti-g-poly(acrylic acid-aniline) as a colon-specific delivery system for amoxicillin trihydrate and paracetamol

Abstract

The objective of the present investigation was to develop colon-specific drug delivery systems for amoxicillin trihydrate and paracetamol using Gum ghatti (Gg) based cross-linked hydrogels. An interpenetrating network (IPN) of electrically active hydrogel based on Gg, poly(acrylic acid) (AA) and polyaniline was synthesized by a two-step aqueous polymerization. The radical copolymerization of Gg and AA was done using N,N′-methylene-bis-acrylamide (MBA) and ammonium persulphate (APS) as a crosslinker-initiator system. Optimum operating conditions for maximizing the percentage swelling were solvent (ml) = 10, AA (mol L⁻¹) = 0.291 × 10⁻³, APS (mol L⁻¹) = 0.219 × 10⁻¹, MBA (mol L⁻¹) = 0.324 × 10⁻¹, reaction time (min) = 180, temperature (°C) = 60 and pH = 7.0. The synthesized semi-IPN matrix was further grafted with aniline through oxidative-radical copolymerization using APS in acidic media. The resultant cross-linked hydrogels were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, ToF-SIMS and electrical conductivity. The maximum conductivity was found to be 2.5 × 10⁻⁶ S cm⁻¹ at 1.5 N HCl concentration. The synthesized hydrogels were loaded with amoxicillin trihydrate and paracetamol as model drugs to investigate the release behaviour. Amoxicillin trihydrate follows the surface phenomena and weak bonding interaction whereas paracetamol exhibited chemical interaction with the hydrogel matrices. The release rate of both the drugs through the synthesized hydrogel matrices was found to show Fickian behaviour at each pH. The hydrogel networks showed lower release in acidic and neutral media than in basic media, making them particularly suitable carriers for colon-specific drug delivery.