Chitosan materials from carbonic acid solution
Inventors
McCarthy, Simon • McGrath, Barbara • KUHN, Sam • Kimball, Jess • Stolten, Michael • Bennett, Amanda
Assignees
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Publication Number
US-9925210-B2
Publication Date
2018-03-27
Expiration Date
Abstract
The present invention comprises chitosan materials and methods of using carbonic acid for aqueous solubilization of neutralized or pre-treated chitosan gels and provides, among other things, substantially acid salt free composition native final forms without requiring subsequent acid salt elution. The invention includes chitosan-based solid and semi-solid material forms, optionally reinforced with chitosan fibers, such as powders, fibers, films, matrices, sponges, implants, scaffolds, fillers, and hydrogels. Native final forms are produced from chitosan powder solubilized in an aqueous acidic solution, processed to form a high pH hydrated chitosan gel precipitate material that is then neutralized by water washing and re-solubilized substantially to chitosan solution using carbonic acid. Chitosan materials can be mixed in solution with one or more of other hydrophilic polymers to create compositional heterogeneity and pharmaceutical agents to achieve controlled release of the agent(s) from the final forms at the site of application.
Core Innovation
The invention relates to chitosan-material production using carbonic acid/CO2 for aqueous solubilization and re-solubilization of neutralized chitosan gels to create native final forms that are solid and semi-solid while being substantially acid-salt free. The approach conditions high-pH hydrated chitosan gel by neutralization, washing, and then re-solubilization in carbonic acid aqueous solution, where the carbonic-acid environment is associated with tunability using CO2 partial pressure.
The resulting chitosan solubilized gel is incorporated into substantially acid-salt-free final forms without requiring acid-salt elution. The native final forms include solid and semi-solid finished compositions such as powders, films, matrices, sponges, scaffolds, implants, fillers, and hydrogels, and the forms can be reinforced with uniformly dispersed chitosan fibers.
The document further describes blending with other hydrophilic polymer heterogeneity and pharmaceutical active agents for controlled release. The materials are described as incapable of repeated solubilization in carbonic acid aqueous solution within a pH range of about 3.4 to about 7.0, while maintaining water-insoluble character in the final form.
Processing described in the document includes producing water-insoluble sponges and hydrogels through freeze-phase separation and shear/freeze processing to retain form on wetting, without retaining reliance on freeze-drying. The materials are characterized as having high water absorbency with minimal swelling and as exhibiting non-adherent behavior on wet tissue surfaces.
Claims Coverage
The independent claim covers a native final-form composition with uniformly dispersed chitosan fibers in a substantially acid-salt-free chitosan solubilized gel material and a defined robustness constraint: the final form is incapable of repeated solubilization in a carbonic acid aqueous solution having a pH between about 3.4 and about 7.0. Dependent claims refine the final form type and additional composition and performance properties.
Native final form with uniformly dispersed chitosan fibers
A solid or semi-solid native final form composition comprising uniformly dispersed chitosan fibers within a substantially acid-salt-free chitosan solubilized gel material.
Incapable of repeated solubilization in carbonic acid across pH 3.4 to 7.0
The native final form material is incapable of repeated solubilization in a carbonic acid aqueous solution having a pH between about 3.4 to about 7.0.
Substantially acid-salt-free chitosan composition
The composition is substantially acid-salt-free, with dependent claim coverage including an acid-salt content within about 0.01% (w/w) to about 5% (w/w).
Non-adhesive retention on biological fluids and wet tissue surfaces
A non-adhesive final composition that remains intact despite exposure to water, saline, blood, or other biological fluids and can stay on wounds or wet tissue surfaces for more than about four to seven days without significant change.
Water-insoluble freeze-phase molded hydrogel final form
The composition is a water-insoluble freeze-phase molded hydrogel in its final form.
Low water content in the final form
The final form contains water at less than about 10% by weight (w/w).
Density constraint of the final form
The final form composition has a density of about 0.12 g/cm3.
Overall claim coverage centers on a substantially acid-salt-free native final-form chitosan composition with uniformly dispersed chitosan fibers and explicit resistance to repeated solubilization in carbonic acid over a pH range of about 3.4 to about 7.0, with dependent claims further limiting acid-salt content, non-adhesive wet-tissue retention, and particular final-form morphologies and physical constraints.
Stated Advantages
Improved biocompatibility by reducing acid-salt residue.
Non-adherent behavior on wet tissue, supporting removability and handling on biological surfaces.
Resistance to dissolution and re-solubilization in the carbonic-acid environment.
Ability to retain complex porous structures without freeze-drying.
High water absorbency with minimal swelling.
Documented Applications
Wound treatment applications using the native chitosan final forms.
Regenerative medicine applications using the native chitosan final forms.
Drug-delivery applications using the native chitosan final forms with pharmaceutical actives for controlled release.
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