W/O/W Emulsion Composition for High Stannous Fluoride Stability
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Solution Overview
Problem
Existing double emulsions with high metal salt content, such as stannous fluoride, are unstable due to charge imbalance at the interface between phases, leading to inefficient encapsulation and delivery of active substances.
Innovation Solution
A water-oil-water (W/O/W) emulsion is formed using at least two emulsifiers, an oil phase, stannous fluoride, a chelating agent, and citric acid, through a one-step emulsification process involving continuous stirring to stabilize high metal salt content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high metal salt content (e.g., stannous fluoride) is used as the active substance in an emulsion, then the functional efficacy is improved, but the emulsion stability deteriorates due to charge imbalance at the interface between phases
Solution Approach 1:
The patent introduces a specific emulsifier system comprising a nonionic emulsifier (e.g., polysorbate 20, polysorbate 80, or polyglycolized glyceride) in combination with an anionic emulsifier (e.g., sodium lauryl sulfate, disodium edetate, or sodium citrate). This emulsifier combination acts as an intermediary at the oil-water interface, with the nonionic emulsifier providing steric stabilization and the anionic emulsifier providing electrostatic stabilization, together preventing charge imbalance and maintaining emulsion stability even at high stannous fluoride concentrations (0.1-5% w/w).
Solution Approach 2:
The patent optimizes specific parameter ranges: emulsifier concentration (0.1-10% w/w total emulsifiers), pH (2-7), and metal salt concentration (0.1-5% w/w stannous fluoride). By controlling these parameters, particularly maintaining pH between 2-7 and using specific emulsifier ratios, the emulsion remains stable despite high metal salt content. The patent also controls ionic strength and uses chelating agents (e.g., EDTA, citric acid) to bind excess metal ions, preventing interface charge imbalance.
2Productivity
If high concentrations of stannous fluoride are used to achieve effective antibacterial action, then the antibacterial efficacy is improved, but the emulsion becomes unstable and difficult to form
Solution Approach 1:
The emulsifier system serves as an intermediary that facilitates the incorporation of high concentrations of stannous fluoride into the emulsion matrix. The nonionic emulsifier (e.g., polysorbate 80 at 0.5-5% w/w) reduces interfacial tension and enables dispersion of the hydrophobic stannous fluoride, while the anionic emulsifier (e.g., sodium lauryl sulfate at 0.1-2% w/w) provides electrostatic repulsion between droplets, preventing coalescence. This intermediary action allows easy formation of stable emulsions with 0.1-5% stannous fluoride.
Solution Approach 2:
The patent creates a composite emulsion system combining multiple components: nonionic emulsifier, anionic emulsifier, oil phase (e.g., mineral oil, vegetable oil, or essential oils), water phase, and stannous fluoride. This composite material approach allows the system to accommodate high metal salt concentrations while maintaining stability. The synergistic interaction between the two emulsifier types and the multi-phase structure enables both high antibacterial efficacy and ease of manufacture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The W/O/W emulsion maintains high retention of Sn2+ ions, ensuring stability and effective encapsulation, with SnF2 retention greater than 70% even at low pH, demonstrating improved antibacterial efficacy against Streptococcus mutans.
Implementation Method 1
A water-oil-water (W/O/W) emulsion is formed using at least two emulsifiers, an oil phase, stannous fluoride, a chelating agent, and citric acid
Implementation Method 2
The oil phase includes at least two emulsifiers and an oil
Implementation Method 3
The water phase includes stannous fluoride, a chelating agent, citric acid, and water
Data Source
AI summary
Provided is a high metal ion concentration emulsion comprising an oil phase and a water phase. The oil phase includes at least two emulsifiers and an oil. The at least two emulsifiers may include a hydrophobic emulsifier and a hydrophilic emulsifier. The water phase includes stannous fluoride, a chelating agent, citric acid, and water.