Method of delivering a lipid-coated condensed-phase microparticle composition

A method of producing an X-ray image of a selected body structure in a subject, comprising

• administering to the subject an encapsulated microparticle composition having an average size between 0.05 and 5 microns, each encapsulated microparticle being composed of
• (i) an external lipid bilayer membrane containing a plasmalogen and effective to allow influx of external ions into said microparticle upon exposure to a stimulus,
• (ii) encapsulated within the lipid membrane, a condensed-phase microparticle which is composed of a matrix of crosslinked polyionic polymer filaments, and which is capable of decondensing to an expanded state when multivalent counterions also present within the matrix are replaced by monovalent counterions, and
• (iii) an X-ray-opaque compound to be released entrapped in the microparticle matrix, with said matrix in its condensed phase, and
• directing a dose of X-irradiation to the body structure sufficient to produce localized perturbation of the lipid membrane, and influx of monovalent counterions into the polymer matrix and to cause microparticle matrix swelling and compound release from said microparticles.

A method of targeting drug delivery to a specific tissue site in a subject, comprising

• administering to the subject an encapsulated microparticle composition having an average size between 0.05 and 5 microns, each encapsulated microparticle being composed of
• (i) an external lipid bilayer membrane containing a plasmalogen and effective to allow influx of external ions into said microparticle upon exposure to reactive oxygen species,
• (ii) attached to the external lipid bilayer membrane, an antigen molecule,
• (iii) encapsulated within the lipid membrane, a condensed-phase microparticle which is composed of a matrix of crosslinked polyionic polymer filaments, and which is capable of decondensing to an expanded state when multivalent counterions also present within the matrix are replaced by monovalent counterions, and
• (iv) a compound to be released entrapped in the microparticle matrix, with said matrix in its condensed phase,
• further administering to the subject an anti-antigen antibody-radionuclide complex effective to bind to said antigen,
• wherein said radionuclide produces a local dose of ionizing radiation sufficient to produce localized perturbation of the lipid membrane, and influx of monovalent counterions into the microparticle matrix and to cause microparticle matrix swelling and compound release from said microparticles.