Details for Patent: 6,287,539

Summary for Patent: 6,287,539

Title:	Methods of imaging using osmotically stabilized microbubble preparations
Abstract:	A microbubble preparation formed of a plurality of microbubbles comprising a first gas and a second gas surrounded by a membrane such as a surfactant, wherein the first gas and the second gas are present in a molar ratio of from about 1:100 to about 1000:1, and wherein the first gas has a vapor pressure of at least about (760-x) mm Hg at 37° C., where x is the vapor pressure of the second gas at 37° C., and wherein the vapor pressure of each of the first and second gases is greater than about 75 mm Hg at 37° C.; also disclosed are methods for preparing microbubble compositions, including compositions that rapidly shrink from a first average diameter to a second average diameter less than about 75% of the first average diameter and are stabilized at the second average diameter; methods and kits for preparing microbubbles; and methods for using such microbubbles as contrast agents.
Inventor(s):	Ernest G. Schutt, Charles David Anderson, David P. Evitts
Assignee:	PHOTOGEN TECHNOLOGIES Inc , TARGESON Inc
Application Number:	US08/841,846
Patent Claim Types: see list of patent claims	Use; Dosage form;

United States Patent 6,287,539: Scope, Claim Architecture, and Landscape for Osmotically Stabilized Gas-Loaded Microbubble Imaging

United States Patent 6,287,539 is an ultrasound and magnetic resonance (MR) imaging method patent that claims in vivo use of an “osmotically stabilized” microbubble preparation containing (i) a “modifier gas” that is not water vapor and (ii) a “gas osmotic agent” that is selected from defined low-water-solubility perfluorinated gases (and in an alternate branch, defined “vapor of a compound” that is a liquid at 37 °C and 760 Torr). The claims center on a molar ratio window of modifier gas to gas osmotic agent from about 1:100 to about 1,000:1, plus optional microbubble membrane composition (surfactant, liposome, proteinaceous material such as albumin).

What is the core claim thesis of US 6,287,539?

The independent claim set (method claims drafted at multiple granularities) is built around one technical thesis:

• Create or administer a microbubble preparation where the microbubble membrane encloses:
  • At least one modifier gas (explicitly “not water vapor”)
  • At least one gas osmotic agent (in a list of perfluorinated compounds; in one branch, a vapor-defined osmotic agent)
• Use a molar ratio window for modifier gas : gas osmotic agent:
  • About 1:100 to about 1,000:1 (repeated throughout dependents)
• Enable in vivo osmotic stabilization such that gases ordinarily dissolved in physiologic fluid diffuse into the bubble with sufficient osmotic pressure to counteract the microbubble Laplace pressure (explicit in several claim families).
• Image the patient by ultrasound or MR after introducing the microbubbles into the relevant anatomical region (object/body part/body cavity; includes vascular system, perfusion defect, myocardial tissue as dependents).

Independent-method capture (what is actually claimed)

Across the provided claim text, the independent claim language appears in multiple forms (you provided claims 1, 53, 70, and 92 as independent-style methods). Each version keeps the same center of gravity:

1) In vivo imaging method using microbubbles with:

• Aqueous dispersion
• Spherical membrane containing modifier gas and gas osmotic agent
• Modifier gas to osmotic agent molar ratio 1:100 to 1,000:1
• Modifier gas not water vapor
• Imaging by ultrasound or MR

2) Variant includes an explicit “vapor of a compound liquid at 37 °C and 760 Torr” limitation for the osmotic agent.

3) Variant adds precursor-container formulation and energy-triggered formation:

• Container holds aqueous medium, surfactant, modifier gas relatively soluble in water, and gas osmotic agent relatively insoluble
• Energy applied to form microbubbles that are osmotically stabilized when introduced into physiological liquid
• Includes mechanistic osmotic dilution concept to counter Laplace pressure
• Then imaging.

4) Variant uses proteinaceous microbubble membranes with “relatively water-soluble modifier gas” and “relatively water-insoluble gas osmotic agent”.

What are the exact claim scope boundaries (the “watertight” limitations)?

1) Modifier gas limitation: “not water vapor” and chemistry split

• Modifier gas is at least one gas inside the microbubble membrane.
• Proviso: modifier gas “is not water vapor” (present in the main independent structures, e.g., claim 1).
• Modifier gas can be:
  • Fluorocarbon modifier gas (claim 2)
  • Nonfluorocarbon modifier gas (claim 4)

Fluorocarbon modifier gases (examples explicitly listed)

• perfluoropropane
• perfluorobutane
• perfluorocyclobutane
• perfluoromethylcyclobutane
• perfluoropentane
• perfluorocyclopentane
  (claim 3)

Nonfluorocarbon modifier gases (examples explicitly listed)

• nitrogen
• oxygen
• carbon dioxide
  (claim 5)

A dependent set also specifies:

• air as nonfluorocarbon modifier gas (claims 18, 33, 59, 67? your text shows 18/33/59/107/112)

2) Gas osmotic agent limitation: defined perfluorinated agents (and an alternate vapor branch)

Main osmotic agent list (perfluorinated gases; examples)

The claims list gas osmotic agents including (as provided):

• perfluoropentane
• perfluorocyclopentane
• perfluoromethylcyclopentane
• perfluorodimethylcyclobutane
• perfluorohexane
• perfluorocyclohexane
• perfluoroheptane
• perfluorocycloheptane
• perfluoromethylcyclohexane
• perfluorodimethylcyclopentane
• perfluorotrimethylcyclobutane
• perfluorotriethylamine
  and combinations (claim 1)

Additional dependent branches narrow or specify subsets, including perfluoropentane (claim 14), perfluorohexane (claim 29), etc.

Water solubility constraint (one dependent adds a numeric filter)

• gas osmotic agent has water solubility not more than about 0.5 mM at 25 °C and 1 atm (claim 6)

Alternate osmotic agent definition in claims 53 and 70 family

Two specific alternate formulations appear in your text:

• In claim 53: osmotic agent “comprises the vapor of a compound which is a liquid at 37 °C and 760 Torr”.
• In claim 70: precursor-container concept where osmotic agent is “relatively insoluble in aqueous medium,” and modifier gas is “relatively soluble in aqueous medium.”

3) Molar ratio window is the central quantitative boundary

The claims repeatedly enforce modifier gas : gas osmotic agent molar ratio from about:

• 1:100 to 1,000:1 (independent claim 1)
• multiple dependents additionally specify nested ranges (examples):
  • between about 1:100 and 1:1 (claim 122)
  • between about 1:10 and 1:1 (claim 123)
  • greater than 1:1 (claims 124, 125, 130, 137, 141, 142, 143, 144, etc.)

The dependent ladder is designed to preserve enforceability across composition variants, not just one “ideal” formulation.

4) Microbubble membrane structural/material options

The claims broaden membrane composition by offering multiple alternative dependent paths:

• Surfactant membrane (claim 7) with broad surfactant taxonomy (claims 8-10) including nonionic, neutral, anionic, fluorinated surfactants, plus non-Newtonian surfactants (claim 9).

• Specific surfactant exemplars include:

  • polyoxypropylene polyoxyethylene copolymers
  • sugar esters
  • fatty alcohols
  • aliphatic amine oxides
  • hyaluronic acid esters/salts
  • specific ethoxylated surfactants (dodecyl poly(ethyleneoxy)ethanol; nonylphenoxy poly(ethyleneoxy)ethanol)
  • hydroxy ethyl starch and derivatives
  • dextran and derivatives
  • sorbitol/sorbitol fatty acid esters
  • gelatin
  • serum albumins
  • phospholipids and specific poloxamer-like / PEG-fatty acid ester families
  • cholesterol, oleic acid, sodium oleate
    (claim 10 and related surficant dependents)

• Liposome membrane (claim 11, 64)

• Proteinaceous membrane (claim 12, 22, 65, 92 family) with albumin as explicit exemplar (claims 13, 40, 66, 102)

5) Administration and imaging modality boundaries

• Introduce microbubble preparation into object/body part/body cavity; dependent claims specify:
  • intravenous administration (claim 49, 91, 103)
  • target anatomy includes:
  • vascular system (claim 50, 67, 88, 99? you provided 67/88)
  • perfusion defect (claim 51, 68, 89)
  • myocardial tissue (claim 52, 69, 90)
• Imaging step is explicitly ultrasound or magnetic resonance (in the independent formulations).

How do the claims stratify into enforceable “baskets” for infringement?

US 6,287,539 is drafted so that infringement can be asserted without committing to one single membrane or modifier gas identity. The claim structure creates a multi-axis “basket” system:

Basket A: Composition axis (modifier gas and osmotic agent)

• Modifier gas not water vapor (must be a defined gas).
• Modifier gas can be fluorocarbon or nonfluorocarbon (with explicit exemplars).
• Gas osmotic agent must be one of defined low-water-solubility perfluorinated agents (or vapor/liquid-analog branch).
• Ratio modifier gas : osmotic agent must be within 1:100 to 1,000:1, with dependents carving narrower subranges.

Basket B: Osmotic function axis (stability mechanism)

Several dependents/in independent variants explicitly tie osmotic stabilization to:

• dilution of modifier gas by osmotic agent so dissolved physiological gases diffuse into bubble
• osmotic pressure sufficient to counteract Laplace pressure

Basket C: Microbubble formation pathway axis

• Some dependents restrict to a precursor-container method with energy-triggered formation (claim 70 family).
• Other independents simply require “introducing” an already formed microbubble preparation.

Basket D: Membrane material axis

• Surfactant (including non-Newtonian and fluorinated surfactants)
• Liposome
• Proteinaceous (albumin exemplar)

Basket E: Use axis (imaging and target)

• Ultrasound or MR imaging
• In vivo introduction (including IV as dependents)
• Anatomical targets: vascular system, perfusion defect, myocardial tissue

This architecture typically supports broader infringement theories (for composition + imaging) while allowing narrower design-around if a competitor avoids the specific ratio window, avoids perfluorinated osmotic agents, or uses different gas architecture not captured by the “modifier gas + gas osmotic agent” construct.

What is the technical “design space” implied by the claims?

The claims indicate microbubbles engineered to resist in vivo gas exchange via osmotic counter-pressure. The claimed microbubbles contain two gas components:

• A modifier gas with higher relative solubility in aqueous medium (implied by “relatively soluble” in claim 70; also reflected in the ratio design).
• A gas osmotic agent that is substantially insoluble in aqueous medium, diluting the modifier gas and creating osmotic pressure to counteract surface-tension-driven gas loss (Laplace pressure).

Key numeric anchors present in your claim text

• Molar ratio: 1:100 to 1,000:1
• Bubble diameter: dependents state:
  • 1 to 10 μm (claims 126, 132, 133, 139, 145, 146)
  • about 6 μm (claims 127, 134, 140, 146? your text shows 140 and 139 and 146; 134 says about 6 μm)
• Osmotic agent water solubility:
  • ≤ 0.5 mM at 25 °C and 1 atm (claim 6)
• Alternative osmotic agent definition:
  • “vapor of compound liquid at 37 °C and 760 Torr” (claim 53/54 branch in your text)

How does claim breadth compare across membrane and gas identity branches?

Membrane breadth

The independent scope (claim 1) only requires “generally spherical microbubble membrane containing at least one modifier gas and at least one gas osmotic agent.” It does not require surfactant or liposome or protein in the independent itself. Dependents expand membrane choices, making it harder to avoid infringement based solely on shell chemistry.

Gas identity breadth

Modifier gas identity is broader than osmotic agent identity:

• Modifier gas has explicit categorical options (fluorocarbon or nonfluorocarbon) and exemplar lists.
• Osmotic agent is restricted to a defined set of perfluorinated compounds in the main claim set (plus the alternate “vapor of liquid at 37 °C and 760 Torr” concept).

Quantitative breadth

The ratio window is wide (three orders of magnitude from 1:100 to 1,000:1). Dependents also slice into subranges but the anchor is still broad.

Formation-route breadth

Claim 70 family introduces additional constraints (precursor container + energy application). But other independents (claim 1, 53, 92) focus on the result (introduced microbubbles used for imaging) rather than the manufacturing step.

What is the practical patent landscape implication of this claim set?

Within a US enforcement posture, US 6,287,539 creates a composition-and-use platform around osmotic stabilization via a two-gas microbubble architecture. The landscape impact tends to cluster around competitors developing:

• stabilized gas microbubbles for ultrasound/MR contrast
• perfluorinated gas payloads intended to improve circulation persistence and reduce gas loss
• formulations combining different gases to tune diffusivity and osmotic exchange
• shells using surfactant, phospholipid, albumin, or hybrid systems

Your claim set suggests that many variants can still fall within scope if they maintain: 1) a modifier gas not water vapor 2) a perfluorinated osmotic agent 3) ratio in the 1:100 to 1,000:1 window 4) microbubble introduced into the body and imaged by ultrasound or MR.

Which dependent claim groups are most likely to matter for freedom-to-operate (FTO) and design-around?

High-leverage dependent claim groups

1) Molar ratio narrowing dependents
They can be used to assert infringement even if accused products differ from an asserted “center” ratio.

2) Osmotic agent water solubility and identity dependents

• Water solubility cap (claim 6)
• Specific osmotic agents (perfluoropentane, perfluorohexane, etc.) create clear claim hooks for specific formulations.

3) Modifier gas identity dependents

• fluorocarbon modifier gas (claims 2-3, 15, 30, etc.)
• nonfluorocarbon modifier gas (claims 4-5, 17, 31-33, etc.)

4) Membrane dependent exemplars
If a competitor uses albumin or fluorinated/non-Newtonian surfactants, those dependent paths narrow into clearer infringement theories.

5) Microbubble diameter dependents

• 1 to 10 μm, and “about 6 μm” If accused compositions fall into this size band, these dependents can strengthen the mapping to product specs.

Potential design-around pressure points (in claim language)

• Use a microbubble formulation where no modifier gas-to-osmotic-agent molar ratio falls within 1:100 to 1,000:1.
• Use an osmotic agent outside the claimed perfluorinated list and outside the “vapor of compound liquid at 37 °C and 760 Torr” branch.
• Use shell systems that do not contain the claimed gas architecture (modifier + osmotic agent) in a way that does not establish the claim’s two-gas construct.

Key Takeaways

• US 6,287,539 claims an in vivo imaging method (ultrasound or MR) using osmotically stabilized microbubbles that contain two gas components: a modifier gas (not water vapor) and a gas osmotic agent chosen from defined perfluorinated compounds (plus a vapor-defined alternate branch).
• The claims enforce a wide molar ratio window of modifier gas to gas osmotic agent: about 1:100 to about 1,000:1, with dependents narrowing into subranges and enabling multiple infringement pathways.
• Membrane composition is broad at the independent level and then expanded via dependents covering surfactants, liposomes, and proteinaceous shells (albumin exemplar).
• The landscape risk is concentrated in competitors that engineer two-gas microbubble contrast agents using perfluorinated osmotic agents and maintain the claimed ratio window, regardless of whether they use surfactant-based, phospholipid, or albumin-like shells.

FAQs

1) Is US 6,287,539 limited to ultrasound imaging?
No. It also covers imaging by magnetic resonance in the independent method claim structures.

2) What is the central numeric limitation in the claims?
The molar ratio of modifier gas to gas osmotic agent is about 1:100 to about 1,000:1.

3) Must the osmotic agent be perfluorinated?
In the main claim family you provided, the gas osmotic agent is selected from a defined list of perfluorinated gases. A separate branch includes a “vapor of a compound liquid at 37 °C and 760 Torr” concept.

4) Does the patent require a specific microbubble shell material?
No at the independent level. Dependents add shell options such as surfactant, liposome, and proteinaceous material (albumin).

5) Does the patent require intravenous administration?
No. IV is a dependent limitation. The method scope includes introducing microbubbles into the object/body part/body cavity more generally, with IV as one optional narrowing.

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References

[1] United States Patent 6,287,539. “Method of imaging an object using osmotically stabilized microbubbles.” (Claims as provided in user input).

Drugs Protected by US Patent 6,287,539

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

International Family Members for US Patent 6,287,539

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	281183
Australia	4922196
Australia	5199701
Australia	694135
Australia	731099
Australia	731671