The invention provides biopolymer sponge tubes closed at one end for use in surgery. The preferred biopolymer iscollagen. The biopolymer sponge tubes are prepared by forming an aqueous dispersion of the biopolymer, introducing the dispersion into tube-shaped moulds, freezing the dispersion in the moulds to form a shaped, aqueous dispersion, followed by freeze-drying the frozen aqueous dispersion. The tubes are fitted over endoscopic surgical staplers to provide improved sealing of stapled tissues, especially for air-tight sealing in lung resections.