Dynamic layer-by-layer films linked with Schiff base bond for sustained drug release

Abstract

Dynamic layer-by-layer films were fabricated from a dextran–doxorubicin conjugate, PO-Dex–DOX, and glycol chitosan (GC), via the in situ Schiff base reaction between the aldehyde groups on PO-Dex–DOX and the amino groups on GC. Because of the reversible, dynamic nature of Schiff base bonds in the films, the films disintegrate gradually when soaked in aqueous solutions, and thus release DOX into the media. The release mechanism is different from ordinary drug carriers, in which the drug is usually released via diffusion or polymer degradation. The drug release rate decreases with increasing molecular weight of dextran. More importantly, because of the stimuli-responsivity of Schiff base bonds, the drug release rate can be tuned via external stimuli. Faster hydrolysis of Schiff base bonds at a lower pH and/or a higher temperature results in accelerated film disintegration and thus faster drug release. In vitro cytotoxicity test suggests that the released DOX retains its antitumor activity.