Abstract: A controlled-gelation aqueous solution is proposed. The solution contains a hydrophobically-aggregating gelling agent, and an effective amount of an inhibitor which suppresses hydrophobic aggregation of the gelling agent. The inhibitor is soluble in water so that when the controlled-gelation aqueous solution contacts aqueous media the inhibitor disperses and gelation occurs. However, the inhibitor is substantially insoluble in hydrocarbons so that when the controlled-gelation aqueous solution contacts hydrocarbon media the inhibitor continues to suppress said hydrophobic aggregation and gelation is suppressed. The solution may be used to control the flow of water into oil wells, making it possible to reduce the water cut.

Abstract: A composition for facilitating delivery of biological agents, comprising a therapeutic or diagnostic agent and a supramolecular complex, the latter comprising (i) a block copolymer, having at least one nonionic, water soluble segment and at least one polyionic segment, and (ii) at least one charged surfactant having hydrophobic groups. The charge of the surfactant is opposite to the charge of the polyionic segment of the block copolymer. The constituents of the supramolecular complex are bound by interaction between the opposite charges thereof and between surfactant hydrophobic groups. The therapeutic or diagnostic agent may be an ionic substance, in which case the ionic substance has a net charge opposite to that of the block copolymer, the net charge being no more than 10.