Injectable Chitosan Solution pH Control for Biocompatibility
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Solution Overview
Problem
Current fillers for aesthetic and medical applications, such as facial fillers, face challenges in maintaining longevity without inducing inflammatory reactions or rapid biodegradation, and existing chitosan solutions are either too acidic for physiological injection or have poor injectability due to gelling issues at physiological pH.
Innovation Solution
A homogeneous aqueous solution of chitosan with a degree of acetylation less than 20% and a pH between 6.2 and 7.2, prepared by dissolving chitosan in water with a weak acid and adjusting the pH through dialysis, maintaining the solution in a liquid form at room temperature for stable and biocompatible injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If chitosan is used as an injectable filler to achieve long-term effect and biocompatibility, then the filling effect longevity is improved, but the product causes tissue necrosis due to low pH
Solution Approach 1:
The patent changes the pH parameter of the chitosan solution from acidic (below 6.2) to near-physiological (6.2-7.2) to eliminate tissue necrosis while preserving the long-term filling effect. This is achieved by adjusting the degree of acetylation and controlling the pH during preparation.
2Object-affected harmful factors
If chitosan solution pH is adjusted to physiological pH to avoid tissue necrosis, then biocompatibility is improved, but the solution gels at room temperature reducing injectability
Solution Approach 1:
The patent creates a temperature-dependent local quality in the chitosan solution: at room temperature it remains liquid for injection, but at body temperature (37°C) it forms a gel for sustained effect. This is achieved by carefully controlling the pH to be above 6.2 but below the gelation point at room temperature.
Solution Approach 2:
The patent utilizes the phase transition of chitosan from liquid to gel as temperature increases from room temperature to body temperature. This thermotropic phase transition enables the solution to be injectable at room temperature while forming a stable gel at the injection site.
3Object-affected harmful factors
If chitosan degree of acetylation is reduced to maintain solubility at physiological pH, then biocompatibility is improved, but the solution stability is reduced
Solution Approach 1:
The patent optimizes the degree of acetylation parameter to be between 70-85%, which is high enough to maintain solubility at physiological pH (improving biocompatibility) but controlled to prevent excessive degradation (maintaining stability). This precise parameter control resolves the contradiction.
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 solution provides a stable, biocompatible, and injectable chitosan formulation that remains liquid at room temperature, avoiding tissue necrosis and ensuring effective, long-term biological filling without undesirable side effects.
Implementation Method 1
prepared by dissolving chitosan in water with a weak acid and adjusting the pH through dialysis
Implementation Method 2
adjusting the pH through dialysis
Implementation Method 3
said solution not containing chitosan having a degree of acetylation greater than 20%, said solution being liquid and homogeneous at room temperature
Data Source
Figure 1~2
AI summary
The present invention relates to a homogeneous aqueous solution of injectable chitosan containing, in a physiologically acceptable medium, between 0.1 and 4.5% by weight of a chitosan having a degree of acetylation less than 20% and a weight average molecular mass of between 100,000 and 1,500,000 g/mol, said solution having a pH greater than or equal to 6.2, and advantageously between 6.2 and 7.2, said solution not containing chitosan having a degree of acetylation greater than 20%, said solution being liquid and homogeneous at ambient temperature. The invention also relates to an aqueous solution as previously described, characterised in that it is preparable by a method comprising at least the following steps: - dissolving the chitosan in water by adding acid such as a weak acid, said weak acid being advantageously chosen from the group consisting of acetic acid, glycolic acid, lactic acid, glutamic acid, and the mixtures of same, and - readjusting the pH by dialysis, preferably at ambient temperature, in order to obtain an aqueous solution having a pH greater than or equal to 6.2, advantageously between 6.2 and 7.2, and preferably between 6.25 and 7.1.