# 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.

- **Patent:** US 4235871
- **Original title:** Method of encapsulating biologically active materials in lipid vesicles
- **Owner:** Individual
- **Granted:** 1980
- **Status:** Public domain (expired)
- **Times cited:** 1,862
- **Field:** biotech, pharmaceutical, materials

## What it does

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.

## 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.

## 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.

## Real-world examples

1. Liposomal drug delivery systems for cancer treatments like Doxil
2. Liposomal formulations for antifungal medications such as Ambisome
3. Some cosmetic products using liposomes to deliver active ingredients
4. Research applications for delivering enzymes or nucleic acids into cells

## Why it matters

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.

## 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.

**Full plain-English explainer:** https://patentbrief.org/patent/us/4235871/hepatitis-b-vaccine-recombivax

**Original patent:** https://patents.google.com/patent/US4235871

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._