Fabrication and evaluation of pH-sensitive guar gum/chitosan/poly(vinyl alcohol) composite for improved gastro-retention of metformin

Retention of drug in the harsh environment of gastrointestinal tract is a major problem faced in oral delivery system as drugs are prone to a pre-mature release in the presence of digestive enzymes in the acidic media. This reduces the bioavailability of the drug and causes other side effects in the stomach. The composite is prepared through an economically viable and green method consisting of polymers such as guar gum, chitosan and poly(vinyl alcohol) for retention of metformin in the gastric media. Montmorillonite clay was incorporated into the composite to improve its mechanical property. Physical properties such as thickness, folding endurance, swelling capacity and transparency of the films were assessed and further characterized using techniques such as Fourier Transform Infrared spectrometry, X-Ray Diffractometry, Differential Scanning Calorimetry and Scanning Electron Microscopy. The prepared films were thin and flexible with an average thickness of 90 μm and exhibited good UV resistance. Metformin containing formulation exhibited ≤ 12% drug release in the simulated gastric fluid (1.2 pH), which satisfied the primary aim of the work. The drug release kinetics evaluated using various mathematical models revealed that Korsemeyer-Peppas was the best fit model and showed R² ≥ 0.986 revealing diffusion-controlled release pattern. Based on the results, the prepared composites could significantly resist early release of metformin in the stomach and improve its bioavailability in the system. This pH-sensitive composite can be anticipated as potential carrier for drugs experiencing pre-mature release in the gastric media.