A Composite Polyelectrolytic Matrix for Controlled Oral Drug Delivery

The purpose of this study was to formulate drug-loaded polyelectrolyte matrices constituting blends of pectin, chitosan (CHT) and hydrolyzed polyacrylamide (HPAAm) for controlling the premature solvation of the polymers and modulating drug release. The model drug employed was the highly water-soluble antihistamine, diphenhydramine HCl (DPH). Polyelectrolyte complex formation was validated by infrared spectroscopy. Matrices were characterized by textural profiling, porositometry and SEM. Drug release studies were performed under simulated gastrointestinal conditions using USP apparatus 3. FTIR spectra revealed distinctive peaks indicating the presence of –COO⁻ symmetrical stretching (1,425–1,390 cm⁻¹) and -NH₃⁺ deformation (1,535 cm⁻¹) with evidence of electrostatic interaction between the cationic CHT and anionic HPAAm corroborated by molecular mechanics simulations of the complexes. Pectin–HPAAm matrices showed electrostatic attraction due to residual –NH₂ and –COO⁻ groups of HPAAm and pectin, respectively. Textural profiling demonstrated that CHT-HPAAm matrices were most resilient at 6.1% and pectin–CHT–HPAAm matrices were the least (3.9%). Matrix hardness and deformation energy followed similar behavior. Pectin–CHT–HPAAm and CHT–HPAAm matrices produced type IV isotherms with H3 hysteresis and mesopores (22.46 nm) while pectin–HPAAm matrices were atypical with hysteresis at a low P/P₀ and pore sizes of 5.15 nm and a large surface area. At t _2 h, no DPH was released from CHT–HPAAm matrices, whereas 28.2% and 82.2% was released from pectin–HPAAm and pectin–CHT–HPAAm matrices, respectively. At t _4 h, complete DPH release was achieved from pectin–CHT–HPAAm matrices in contrast to only 35% from CHT–HPAAm matrices. This revealed the release-modulating capability of each matrix signifying their applicability in controlled oral drug delivery applications.