A study of the influence of drug loading level on the morphology and burst release in the in situ forming matrices

Injectable biomaterials are widely researched and hold great promise in the field of drug delivery, largely due to the minimally invasive nature which they can be delivered. Drugrelease kinetics can be varied via altering the character and processing of the injectable biomaterial matrix or depot, andthe properties (size, hydrophilicity, amount of loading, etc.) of the drug to be released often have a large effect on release kinetics [1].Phase separation involves dissolving a water insolublepolymer and the model drug like Leuprolide acetate in a water miscible, cytocompatible solvent such as N-methyl-2-pyrolidone. Because the polymer phase is water insoluble, injection into an aqueous environment results in exchange of the injected solvent with water from the surrounding environment, leading to precipitation of the polymer phase. Burst release is often seen initially and is related to the time ittakes for the solid matrix to form. Nature (hydrophobicity or hydrophilicity) of drug as a additive can have an effect on the initial burst release by varying the pore morphology of the polymer matrix [2].