How to Encapsulate Active Materials in Lipid Bubbles Efficiently
This patent describes a method for trapping biologically active substances inside tiny, multi-layered fat bubbles called liposomes, using a specific water-in-oil emulsion and gel-forming process to improve how much material gets captured.
Original patent title: “Method of encapsulating biologically active materials in lipid vesicles”
This patent describes a method for trapping biologically active substances inside tiny, multi-layered fat bubbles called liposomes, using a specific water-in-oil emulsion and gel-forming process to improve how much material gets captured. Granted to Individual in 1980 with 27 claims and 1,862 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent details a four-step method for encapsulating biologically active materials within synthetic, oligolamellar lipid vesicles (liposomes). First, it involves providing a mixture of a wall-forming compound (like a phospholipid, per claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 2) in an organic solvent and an aqueous mixture of the material to be encapsulated. This is then formed into a homogeneous water-in-oil type emulsion, as specified in claim 1. Next, the organic solvent is evaporated from this emulsion until it becomes a gel-like mixture. Finally, this gel is converted into a suspension of liposomes by either agitating the gel or dispersing it in an aqueous medium, effectively trapping the active material inside. For example, insulin (claim 20) could be encapsulated using this method.
The gap
What does this patent NOT cover?
- Does not cover encapsulation methods that do not form a water-in-oil type emulsion as an intermediate step.
- Does not cover methods that do not involve evaporating an organic solvent to create a gel-like mixture.
- Does not cover forming liposomes that are not 'oligolamellar' (having a few layers), such as single-layered or highly multi-layered vesicles.
- Does not cover methods where the biologically active material is not initially in an aqueous mixture.
- Does not cover methods where the wall-forming compound is not initially provided in an organic solvent.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The clever part is the specific process of forming a water-in-oil emulsion, then evaporating the organic solvent to create a gel-like intermediate, and finally converting this gel into liposomes. This sequence, particularly the gel-forming step, was found to significantly increase the 'capture efficiency' of the biologically active material, meaning more of the desired substance ends up inside the liposomes.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Liposomal drug delivery systems for cancer treatments like Doxil
Liposomal formulations for antifungal medications such as Ambisome
Some cosmetic products using liposomes to deliver active ingredients
Research applications for delivering enzymes or nucleic acids into cells
Why it matters
The bigger picture
This method improved the efficiency of creating liposomes, which are crucial for delivering medicines, vaccines, and other sensitive substances within the body. By trapping these materials inside protective lipid bubbles, they can be delivered more effectively, protected from degradation, and potentially targeted to specific areas. This innovation made liposome production more practical for various applications.
Filed
February 24, 1978
Granted
November 25, 1980
Market context
Who's building on this
Companies in this space
Many pharmaceutical and biotechnology companies continue to build on the foundational principles of liposome encapsulation. Companies like Johnson & Johnson (through its Janssen Pharmaceuticals division) and Gilead Sciences develop and market liposomal drug formulations. Research institutions and startups also actively explore new lipid compositions and encapsulation methods for novel therapies, including gene therapies and vaccines.
Market impact
This patent contributed to making liposome technology more viable for commercial applications by offering a method with improved capture efficiency. It helped pave the way for a generation of liposomal drugs that offered better patient outcomes by protecting sensitive compounds and enabling targeted delivery. The method's advantages in efficiency supported the broader adoption and development of liposome-based products across the pharmaceutical and biotech industries.
Claim 1 — Plain English
What this patent covers
This patent details a four-step method for encapsulating biologically active materials within synthetic, oligolamellar lipid vesicles (liposomes). First, it involves providing a mixture of a wall-forming compound (like a phospholipid, per claim 2) in an organic solvent and an aqueous mixture of the material to be encapsulated. This is then formed into a homogeneous water-in-oil type emulsion, as specified in claim 1. Next, the organic solvent is evaporated from this emulsion until it becomes a gel-like mixture. Finally, this gel is converted into a suspension of liposomes by either agitating the gel or dispersing it in an aqueous medium, effectively trapping the active material inside. For example, insulin (claim 20) could be encapsulated using this method.
The clever bit
The clever part is the specific process of forming a water-in-oil emulsion, then evaporating the organic solvent to create a gel-like intermediate, and finally converting this gel into liposomes. This sequence, particularly the gel-forming step, was found to significantly increase the 'capture efficiency' of the biologically active material, meaning more of the desired substance ends up inside the liposomes.
What it does not cover
- Does not cover encapsulation methods that do not form a water-in-oil type emulsion as an intermediate step.
- Does not cover methods that do not involve evaporating an organic solvent to create a gel-like mixture.
- Does not cover forming liposomes that are not 'oligolamellar' (having a few layers), such as single-layered or highly multi-layered vesicles.
- Does not cover methods where the biologically active material is not initially in an aqueous mixture.
- Does not cover methods where the wall-forming compound is not initially provided in an organic solvent.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
18/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$176K – $562K
Midpoint $351K · expired or expiring · industry ×3.0
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
27 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Papahadjopoulos, D. P., & Jr., F. C. S. (1980). How to Encapsulate Active Materials in Lipid Bubbles Efficiently (U.S. Patent No. 4,235,871). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4235871/hepatitis-b-vaccine-recombivax
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How to Encapsulate Active Materials in Lipid Bubbles Efficiently cover?
This patent describes a method for trapping biologically active substances inside tiny, multi-layered fat bubbles called liposomes, using a specific water-in-oil emulsion and gel-forming process to improve how much material gets captured.
Who owns patent US 4235871?
Individual owns this patent, granted in 1980.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 4235871 cited by?
This patent has been cited by 1862 later patents that build on its ideas.
What problem does this patent solve?
This method improved the efficiency of creating liposomes, which are crucial for delivering medicines, vaccines, and other sensitive substances within the body. By trapping these materials inside protective lipid bubbles, they can be delivered more effectively, protected from degradation, and potentially targeted to specific areas. This innovation made liposome production more practical for various applications.
What does this patent NOT cover?
Does not cover encapsulation methods that do not form a water-in-oil type emulsion as an intermediate step.
Same assignee
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