Carbon-nanotube-assisted high loading and controlled release of polyoxometalates in biodegradable multilayer thin films

Carbon nanotubes loaded with peptides, proteins and drugs can translocate across the cell membrane. This big advantage has attracted increasing attention to design a novel delivery system using nanotubes. Polyoxometalate (POM) is a promising antitumor drug and it shows a very strong interaction with carbon nanotube surfaces. In this paper, a novel complex of POM-modified single-walled carbon nanotubes (SWNTs) and chitosan was fabricated through a layer-by-layer self-assembly process. With the addition of SWNTs, the loading of POM in this thin film was doubled in the high ionic strength. The initial burst release of POMs in the (POM/chitosan)_n thin film was suppressed in the (POM-SWNT/chitosan)_n thin film. Also the instability of POMs in a physiologically relevant pH environment was overcome. The strong interaction between POMs and SWNTs was believed to be the determinant factor in the higher loading and prolonged release of POMs in (POM-SWNT/chitosan)_n thin films.