pH responsive, reversible photo-crosslinkable micelle in layer-by-layer assembly-Study on film growth and drug delivery behavior

Layer-by-layer multilayered film has been creating great opportunities in developing controlled drug and other bioactive molecular delivery system. In this work, coumarin bearing micelles of poly(acrylic acid-coumarin methacrylate) is first synthesized in a one-step copolymerization and the reversible photo-crosslinkable multilayers containing coumarin groups are then fabricated via layering the micelles with polyethyleneimine (PEI). The film growth behavior of polyetheleneimine/poly(acrylic acid-coumarin methacrylate) (PEI/P(AA-r-CMA)) multilayer is found to rely on deposit solution pH. Increasing PEI solution pH and decreasing P(AA-r-CMA) pH can greatly accelerate film growing process. This is explained by PEI diffusivity and destabilization of P(AA-r-CMA) micelle at solution/multilayer interface. Nile red (NR) is loaded into the film as a model drug via simple post diffusion driven by hydrophobic interactions. Furthermore, photo-crosslink and decrosslink of PEI/P(AA-r-CMA) film is achieved by irradiating the films with light of 365 and 254 nm wavelength, respectively, which therefore ensures the possibility of fine control over drug delivery procedure.