Patent ID: 7374745

Claim:
A biocompatible composition comprising microbubbles encapsulating a gas within a shell comprising a plurality of compounds, each compound having a polar head group linked to a straight-chain hydrophobic group selected as having different chain lengths sufficient for longer chains to assemble beneath adjacent shorter chains thereby enhancing rigidity of the shell, the hydrophobic groups oriented toward the gas, wherein the compounds have the structure R 1 —X-Z; R 2 —X-Z; and R 3 —X-Z′ where R 1 , R 2 and R 3 are hydrophobic groups selected from the group consisting of straight-chain alkyls, alkylethers, alkylthiolethers, alkyldisulfides, polyfluoroalkyls, and polyfluoroalkylethers having a carbon chain length greater than or equal to 16 and less than or equal to 32 and where R 1 is greater than R 2 and R 1 is greater than or equal to R 3 ; R 3 has one or more such hydrophobic groups having the same or different lengths; X is a linker connecting the hydrophobic group to the polar head group; Z is a polar head group selected from the group consisting of CO 2 -M + , SO 3 − M + , SO 4 − M + , PO 3 − M + , PO 4 − M + 2 , N(R) 4 + , a pyridinium or substituted pyridinium group, and a zwitterionic group; R is selected from the group consisting of —H, —CH 3 , alkyl, cycloalkyl, substituted cycloalkyls containing one or more heteroatoms, and benzyl and can be the same or different; and Z′ is a nonionic group selected from the group consisting of polysorbates, polyglycerols, polypeptides, polynucleotides, polysaccharides, polyvinylpyrrolidones, polyvinylalcohols, polyethyleneglycols, and combinations thereof.