Controlled drugs released from gelatin hydrogels

This study evaluates and characterizes the use of porcine and fish gelatin hydrogels as the matrix in a controlled drug delivery system. The drug-loaded gelatin hydrogels were prepared by solution-casting using salicylic acid and 5-sulfosalicylic acid as the model drugs and glutaraldehyde as the crosslinking agent. The average molecular weight between crosslink, the crosslinking density, and the mesh size of the gelatin hydrogels were determined using the equilibrium swelling theory, as well as by scanning electron microscopy. The release mechanisms and the diffusion coefficients of the hydrogels were determined by using a modified Franz-Diffusion cell in an acetate buffer (at pH 5.5 and at a temperature of 37 °C for 48 hours) in order to investigate the effect of the crosslinking ratio. The diffusion coefficient of the drug was determined through the Higuchi equation at various crosslink ratios and different drug size. The diffusion coefficients of drug in the gelatin hydrogels decrease with increasing crosslink ratio due to the smaller mesh sizes of gelatin hydrogels. The diffusion coefficient of a smaller drug size is higher than that of a larger drug size. The diffusion coefficients obey the power law of the drug size over the mesh size ratio with the scaling exponent m equal to 0.45.