A multilayer film including a layer of sealing film, having main top and bottom surfaces, and a layer of thermoplastic polymer film, laminated to the layer of sealing film, on at least one of the main top and bottom surfaces. The sealing film has a composition and thickness imparting gas barrier character to the multilayer film, of which the layer(s) of thermoplastic polymer film by themselves lack such gas barrier character. Such multilayer film is usefully employed to form biologically compatible therapeutic articles such as medical balloons that are constructed to be inflated in vivo.