Grafted tamarind kernel polysaccharide based Al3+ cross-linked hydrogel matrices for sustained release of drug in the gastrointestinal milieu

Ionically cross-linked hydrogel serves as an excellent matrix material for the sustained delivery of drugs. Tablets prepared with tamarind kernel polysaccharide (TKP) as the sole matrix material could not provide sustained release of the incorporated drugs. The purpose of the work was to modify TKP and development of ionically cross-linked hydrogel matrix tablets for sustained drug delivery. Grafting of TKP was performed with methacrylic acid (MAA) following the free radical polymerization technique. Hydrogel matrix tablets using Al³⁺ ion cross-linked grafted TKP were prepared by direct compression method. Al³⁺ ions were found to considerably influence the erosion, swelling, and paracetamol release from the matrix tablet. Retardation of the erosion, swelling, and paracetamol release was observed with increasing the concentration of Al³⁺ ions. The hydrogel matrix tablets showed a slow release of drugs in an acidic medium and a relatively faster drug release in an alkaline medium. The optimized formulation having a co-polymer/aluminium hydroxide (Al(OH)₃) ratio of 1:1, exhibited sustained drug release action for more than 10 h with lower swelling and erosion of the gel matrix. We conclude that Al³⁺ ion cross-linked grafted TKP is an excellent matrix material for sustained delivery of drugs in the gastrointestinal milieu.