Polysaccharide Gelled Foam via Gas-Triggered Ionic Crosslinking
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Solution Overview
Problem
Existing methods for preparing polysaccharide foams, such as alginate foams, require acidification to trigger crosslinking, which can cause pain, irritation, and complicate in situ applications, and often necessitate costly sterile equipment and formulations with low initial viscosity.
Innovation Solution
A method involving a solubilized polysaccharide, an ionic crosslinking agent that is not immediately available, a solvent, and optional plasticizer and surfactant, followed by foaming and gelling with a pH-modifying gas, without the need for acid addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acidification is used to trigger crosslinking, then gelation can be achieved, but pain, irritation, and formulation complexity increase
Solution Approach 1:
The patent removes the harmful acidification step from the crosslinking process by using soluble polyvalent counterions that directly trigger gelation through ionic crosslinking, eliminating the source of pain and irritation while maintaining reliable gel formation
Solution Approach 2:
The patent introduces soluble polyvalent counterions as an intermediary mechanism that enables crosslinking without acidification. These counterions act as mediators between the polysaccharide chains, forming ionic bonds that trigger gelation in a biocompatible manner
2Manufacturing precision
If fast mixing is performed to achieve homogeneous gelation, then homogeneous foam is obtained, but low viscosity formulations are required which compromise mechanical properties
Solution Approach 1:
The patent performs preliminary homogeneous mixing of the polysaccharide solution with soluble polyvalent counterions before foaming, ensuring uniform distribution of crosslinking sites throughout the foam matrix. This preliminary action allows subsequent foaming to proceed without requiring low viscosity, preserving mechanical properties while achieving homogeneity
Solution Approach 2:
The patent employs dynamic control of the foaming process, using mechanical agitation or gas injection during foam formation to ensure homogeneous gas distribution. This dynamic approach achieves uniform foam structure without requiring the polysaccharide solution to have low viscosity, thus maintaining mechanical strength
3Manufacturing precision
If covalent crosslinking agents are used, then crosslink density can be precisely controlled, but toxicity increases
Solution Approach 1:
The patent changes the chemical nature of the crosslinking mechanism from covalent to ionic bonding. By using soluble polyvalent counterions, the system achieves crosslinking through ionic interactions that can be precisely controlled by adjusting counterion concentration, while avoiding the toxicity associated with covalent crosslinking agents
Solution Approach 2:
The patent creates a biocompatible environment by using physiologically acceptable soluble polyvalent counterions that do not introduce toxicity. These counterions provide an inert, safe chemical environment for crosslinking, enabling precise control of crosslink density without harmful effects
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
This method produces a homogeneous, stable, and mechanically strong polysaccharide foam suitable for biomedical, food, and cosmetic applications, avoiding the need for acid and sterile equipment, and maintaining mechanical properties.
Implementation Method 1
The acidification of the solution containing the insoluble metal salts induces gelling, and possibly foaming when an effervescent agent is present
Implementation Method 2
The polyvalent cation can then be dissolved by adjusting the pH of the solution, usually by acidification. In the case of calcium carbonate, adding acid causes its dissociation into calcium ions and carbonate ions
Implementation Method 3
The metal cation complex can for example be obtained by means of a chelating agent such as EGTA (egtazic acid) or EDTA (ethylenediaminetetraacetic acid). The calcium ion complex solution can then be mixed with the polysaccharide (alginate) solution
Implementation Method 4
The soluble salt (coming from the solubilized polyvalent counterion) complexes with the carboxylate groups of the solubilized polysaccharide to form a polysaccharide gel that is insoluble in a physiological medium
Implementation Method 5
The association kinetics of the polyvalent counterions with the solubilized polysaccharide (for example alginate) is very rapid (instantaneous on a human scale)
Implementation Method 6
The foaming step can be carried out chemically, for example by means of a foaming agent, or physically, by means of a mixer, or any other expansion system, or by incorporation of gas
Data Source
AI summary
A method for the preparation of a gelled polysaccharide foam, which includes the following steps: (a) the preparation of a mixture including at least one solubilized polysaccharide chosen from alginates, pectic substances, carrageenans, and mixtures thereof, at least one solvent of the polysaccharide, at least one ionic crosslinking agent of the polysaccharide, the crosslinking agent being not available, optionally a plasticizer soluble into the solvent, optionally a surfactant, and optionally an additive, (b) foaming and gelling the mixture prepared at step (a) by incorporating a pH modifying gas, and (c) optionally drying the gelled foam obtained at step (b). Also, the gelled foam obtained from such a method as well as the uses thereof.