Encapsulation of microbubbles within the aqueous core of microcapsules

1. A construct comprising an echogenic microcapsule comprising:

a contiguous first shell uninterrupted by gas;

an aqueous core surrounded by the first shell;

at least one micro-bubble encapsulated by a second shell;

wherein the at least one encapsulated microbubble comprises a gas and is within the aqueous core of the echogenic microcapsule; and

wherein the first shell becomes permeable to the aqueous core when the microcapsule is irradiated with an ultrasound intensity that is equal to or higher than the leakage threshold intensity of the microcapsule.

2. The construct of claim 1 , wherein the first shell comprises phospholipids.

3. The construct of claim 1 , wherein the first shell further comprises from about 0.001% to about 10% of an oil.

4. The construct of claim 1 , wherein the aqueous core comprises a therapeutic agent.

5. The construct of claim 1 , wherein the at least one encapsulated microbubble is free-floating in the aqueous core.

6. The construct of claim 1 , wherein the at least one encapsulated microbubble is tethered to the inner surface of the microcapsule.

7. The construct of claim 1 , wherein the gas comprises a chemical selected from the group consisting of air, octafluoropropane, perfluorobutane, and sulfur hexafluoride.

8. The construct of claim 1 , further comprising at least one pharmaceutically acceptable carrier.

9. A method of imaging a tissue or an organ in a subject, wherein the method comprises the steps of:

administering to the subject a pharmaceutical composition comprising a construct comprising an echogenic microcapsule comprising:

a contiguous first shell uninterrupted by gas;

an aqueous core surrounded by the first shell;

at least one microbubble encapsulated by a second shell;

wherein the at least one encapsulated microbubble comprises a gas and is within the aqueous core of the echogenic microcapsule; and

wherein the first shell becomes permeable to the aqueous core when the microcapsule is irradiated with an ultrasound intensity that is equal to or higher than the leakage threshold intensity of the microcapsule;

and,

monitoring the location of the construct within the subject by ultrasound techniques using a first ultrasound intensity, wherein the first ultrasound intensity is lower than the leakage threshold intensity of the microcapsule.

10. The method of claim 9 , wherein the shell comprises phospholipids.

11. The method of claim 9 , wherein the shell further comprises from about 0.001% to about 10% of an oil.

12. The method of claim 9 , wherein the aqueous core comprises a therapeutic agent.

13. The method of claim 9 , wherein the at least one microbubble is free-floating in the aqueous core.

14. A method of delivering a therapeutic cargo to a tissue or organ in a subject, wherein the method comprises the steps of:

administering to the subject a pharmaceutical composition comprising a construct comprising an echogenic microcapsule, wherein a therapeutic cargo is associated with the construct, wherein the echogenic microcapsule comprises:

a contiguous first shell uninterrupted by gas;

an aqueous core surrounded by the first shell;

at least one microbubble encapsulated by a second shell;

wherein the at least one encapsulated microbubble comprises a gas and is within the aqueous core of the echogenic microcapsule;

wherein the first shell becomes permeable to the aqueous core when the microcapsule is irradiated with an ultrasound intensity that is equal to or higher than the leakage threshold intensity of the microcapsule;

monitoring the location of the construct within the subject by ultrasound techniques using a first ultrasound intensity, wherein the first ultrasound intensity is lower than the leakage threshold intensity of the microcapsule;

detecting presence of the construct in the vicinity of the organ or tissue based on ultrasound monitoring; and,

releasing the therapecutic cargo from the construct by applying a second ultrasound intensity to the construct, wherein the second ultrasound intensity is:

equal to or higher than the leakage threshold of the microcapsule, and

equal to or lower than the maximum ultrasound intensity that can be safely applied to the tissue or organ.

15. A method of treating a disease or disorder in a subject in need thereof, the method comprising the steps of:

administering to the subject an effective amount of a pharmaceutical composition comprising a construct comprising an echogenic microcapsule, wherein a therapeutic cargo that treats the disease or disorder is associated with the construct, wherein the echogenic microcapsule comprises:

a contiguous first shell uninterrupted by gas;

an aqueous core surrounded by the first shell;

at least one microbubble encapsulated by a second shell;

wherein the at least one encapsulated microbubble comprises a gas and is within the aqueous core of the echogenic microcapsule;

wherein the first shell becomes permeable to the aqueous core when the microcapsule is irradiated with an ultrasound intensity that is equal to or higher than the leakage threshold intensity of the microcapsule;

monitoring the location of the construct within the subject by ultrasound methods using a first ultrasound intensity, wherein the first ultrasound intensity is lower than the leakage threshold intensity of the microcapsule;

detecting presence of the construct in the vicinity of an organ or tissue that is associated with the disease or disorder, based on ultrasound monitoring; and,

releasing the therapecutic cargo from the construct by applying a second ultrasound intensity to the construct, wherein the second ultrasound intensity is:

equal to or higher than the leakage threshold of the microcapsule, and

equal to or lower than the maximum ultrasound intensity that can be safely applied to the tissue or organ.

16. The construct of claim 1 , wherein the contiguous first shell is a polymeric shell.

17. The construct of claim 1 , wherein the construct can withstand ultrasound contrast imaging at ultrasound intensities below the leakage threshold of the microcapsule.

18. The construct of claim 1 , wherein the construct is produced using a water/oil/water emulsion technique.

19. A construct comprising an echogenic microcapsule comprising:

a contiguous first shell uninterrupted by gas;

an aqueous core surrounded by the first shell; and

at least one micro-bubble encapsulated by a second shell, wherein the encapsulated microbubble comprises a gas and is within the aqueous core of the echogenic microcapsule;

wherein the contiguous first shell protects the at least one encapsulated micro-bubble and yields increased ultrasound longevity relative to an identical microbubble that is not encapsulated by the contiguous first shell; and

wherein the contiguous first shell is ruptured upon cavitation of the at least one encapsulated microbubble.

20. The construct of claim 19 , wherein the first shell is a polymeric shell.

21. The construct of claim 19 , wherein the first shell comprises phospholipids.

22. The construct of claim 19 , wherein the microbubble comprises a perfluorocarbon gas.

23. The construct of claim 19 , wherein the construct can withstand ultrasound contrast imaging at ultrasound intensities below the leakage threshold of the microcapsule.

24. The construct of claim 19 , wherein the construct is produced using a water/oil/water emulsion technique.

25. The construct of claim 1 , wherein the second shell comprises a gel-phase lipid.

26. The construct of claim 25 , wherein the gel-phase lipid comprises a gel-phase phospholipid.

27. The construct of claim 1 , wherein the second shell comprises at least one compound selected from the group consisting of PEGylated phospholipid, DMPC (dimyristoylphosphatidylcholine), DSPC (distearoylphosphatidylcholine), and egg PC (egg phosphatidylcholine).