A film for the retention and controlled release of organic or inorganic molecules consists essentially of a phyllosilicate clay and a organic polyanion. The film may be a built-up layered film of alternating layers of the clay and the polyanion. Organic or inorganic molecules are absorbed into the film from solution, and released in response to changes in the film's environment. The film may be built up using layer-by-layer (LbL) methods, or deposited on a substrate from a mixture of the clay and polyanion. Articles may be coated with the film by the same methods. The film is useful for the controlled release of antibiotics in response to infections, and also retains antibiotics such that bacteria may be killed by direct contact with the film.