Fibrillar bacterial proteins can be mixed with oil in or on water. The interaction of the proteins at the oil-water interface can result in oil dispersion in water in the form of droplets surrounded by an aggregated protein film. The film may be formed by multiple layers of the fibrillar proteins with water between adjacent protein layers. The proteins may be derived from bacterial cells, such as Bacillus subtilis. The encapsulated oil droplets can be collected from the water, for example, as part of an oil spill clean-up or oil storage. The oil may be removed from the collected droplets, for example, by evaporation to produce a three-dimensional network composed of the aggregated films. The three-dimensional network material can be used as a coating for transplant material, grafted onto implant material to improve biocompatibility, as a precursor for tissue growth or engineering, or provided into a human or animal body.