Effect of pH on the structure and drug release profiles of layer-by-layer assembled films containing polyelectrolyte, micelles, and graphene oxide.

Layer by layer (lbl) assembled multilayer thin films are used in drug delivery systems with attractive advantages such as unlimited selection of building blocks and free modification of the film structure. In this paper, we report the fundamental properties of lbl films constructed from different substances such as PS-b-PAA amphiphilic block copolymer micelles (BCM) as nano-sized drug vehicles, 2D-shaped graphene oxide (GO), and branched polyethylenimine (bPEI). These films were fabricated by successive lbl assembly as a result of electrostatic interactions between the carboxyl group of BCM and amine group of functionalized GO or bPEI under various pH conditions. We also compared the thickness, roughness, morphology and degree of adsorption of the (bPEI/BCM) films to those in the (GO/BCM) films. The results showed significant difference because of the distinct pH dependence of each material. In addition, drug release rates of the GO/BCM film were more rapid those of the (bPEI/BCM) film in pH 7.4 and pH 2 PBS buffer solutions. In (bPEI/BCM/GO/BCM) film, the inserted GO layers into bPEI/BCM multilayer induced rapid drug release. We believe that these materials &pH dependent film properties allow developments in the control of coating techniques for biological and biomedical applications.