Magnetic microparticles

• US 5,411,730 A
• Filed: 07/20/1993
• Issued: 05/02/1995
• Est. Priority Date: 07/20/1993
• Status: Expired due to Term

• Current Assignee: Daniel C.F. Chan, Dmitri B. Kirpotin, Paul A. Bunn Jr
• Original Assignee: Research Corporation Technologies
• Inventors: Kirpotin, Dmitri, Bunn, Paul A. Jr., Chan, Daniel C. F.
• Primary Examiner(s): Hollinden, Gary E.
• Application Number:
  US08/094,790
• Time in Patent Office: 651 Days
• Field of Search: 424/9, 428/403, 423/633, 423/634, 436/173, 436/806, 128/653.4, 128/654, 514/6, 514/54, 514/59
• US Class Current: 424/9.322
• CPC Class Codes: A61K 41/0052 Thermotherapy; Hyperthermia; Magnetic induction; Induction heating therapy
• CPC Class Codes: A61K 49/1863 the organic macromolecular compound being a polysaccharide or derivative thereof, e.g. chitosan, chitin, cellulose, pectin, starch
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH
• CPC Class Codes: G01R 33/5601 involving use of a contrast agent for contrast manipulation, e.g. a paramagnetic, super-paramagnetic, ferromagnetic or hyperpolarised contrast agent
• CPC Class Codes: Y10S 436/806 Electrical property or magnetic property
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 436/24 Nuclear magnetic resonance, electron spin resonance or other spin effects or mass spectrometry

Abstract

Superparamagnetic particles are provided for medical applications including hyperthermia techniques, localized heating and tissue-specific release of therapeutic agents, and magnetic resonance imaging contrast enhancement, comprising superparamagnetic iron oxide and a polymer such as dextran at a ratio of about 0.5 to 0.1 w/w of polymer to iron. The particles display at least one of the following magnetic properties: (a) specific power absorption rate greater than 300 w/g Fe; (b) initial magnetic susceptibility greater than 0.7 EMU/g Fe/Gauss; and (c) magnetic moment greater than 10^-15 erg/Gauss.

Claims

1. A composition comprising particles of an iron oxide and a polymer, said iron oxide being superparamagnetic, the ratio of polymer to iron being 0.1 to 0.5 (w/w), said particles having sedimentation constants in the range of 150-5000S, said particles having at least one of the following magnetic properties:

a) specific power absorption rate (SAR) greater than 300 w/g Fe, measured in an electromagnetic field of 1 MHz frequency and 100 Oe field strength;

b) initial magnetic susceptibility greater than 0.7 EMU/gFe/Gauss; and

c) magnetic moment greater than 10^-15 erg/Gauss.

2. A composition according to claim 1 wherein the polymer is dextran.

3. A composition according to claim 1 wherein the specific power absorption rate is greater than 350 W/g Fe.

4. A composition according to claim 1 wherein the polymer-iron ratio is 0.2-0.4 (w/w).

5. A composition according to claim 1 wherein the particles have sedimentation constants in the range of 500-2500S.

6. A composition according to claim 1 wherein the particles have at least two of the magnetic properties set forth in claim 1.

7. A composition according to claim 1 wherein the particles have all three of the magnetic properties set forth in claim 1.

8. A composition according to claim 3 wherein the particles have at least one of the properties b) and c) set forth in claim 1.

9. A composition according to claim 1 wherein the particles further comprise a particle-encapsulating lipid.

10. A composition according to claim 9 wherein the particle-encapsulating lipid comprises an antibody or antibody fragment.

11. A composition according to claim 9 wherein the particle-encapsulating lipid has a transition temperature in the range of 41°

-54°

C.

12. A composition according to claim 11 wherein the particle-encapsulating lipid further comprises a therapeutic agent.

13. A method for heating a tissue comprising contacting said tissue with the composition of claim 1, then exposing said tissue to an oscillating electro-magnetic field at a frequency of 0.5-1.5 MHz and a field strength of 75-150 Oe.