Process for preparing a cross-linked hyaluronic acid product
View Patent ↗Efficient cross-linking of hyaluronic acid (HA) is provided by a manufacturing process. In the process, HA is activated by an initial cross-linking in an aqueous solution. Unreacted cross-linking agent is removed from the activated HA. Cross-linking of the activated HA is finalized, without addition of any additional cross-linking agent, in a suspension of a liquid precipitating medium and the activated HA in precipitated form. The resulting cross-linked HA products exhibit high effective cross-linker ratio and other favorable properties, making the products useful as implants and in medical and cosmetic surgery.
1. A process for manufacturing a cross-linked hyaluronic acid (HA) product, comprising:
(a) initiating cross-linking of HA by reacting HA with one or more polyfunctional cross-linking agents in an aqueous solution to obtain an activated HA;
(b) removing unreacted cross-linking agent(s) from the activated HA; and
(c) finalizing the cross-linking of the activated HA by subjecting the activated HA to further cross-linking conditions without addition of any additional cross-linking agent to obtain a cross-linked HA product;
wherein the finalizing cross-linking step (c) is performed in a suspension of a liquid precipitating medium and the activated HA in precipitated form.
2. A process according to claim 1 , wherein the removing step (b) comprises:
(b1) precipitating the activated HA in a liquid precipitating medium to obtain a suspension comprising the liquid precipitating medium and the activated HA in precipitated form; and
(b2) removing unreacted cross-linking agent(s) from the suspension of precipitated, activated HA.
3. A process according to claim 2 , wherein the removing substep (b2) comprises washing the precipitated, activated HA with a liquid precipitating medium.
4. A process according to claim 1 , wherein the finalizing cross-linking step (c) comprises:
(c1) precipitating the activated HA in a liquid precipitating medium to obtain a suspension comprising the liquid precipitating medium and the activated HA in precipitated form; and
(c2) finalizing the cross-linking of the activated HA by subjecting the suspension of precipitated, activated HA to further cross-linking conditions without addition of any additional cross-linking agent to obtain a cross-linked HA product.
5. A process according to claim 1 , wherein the liquid precipitating medium contains more than 65 wt % of a water-soluble organic solvent.
6. A process according to claim 5 , wherein the water-soluble organic solvent is ethanol.
7. A process according to claim 1 , wherein the initial cross-linking step (a) provides an activated HA in gel form.
8. A process according to claim 1 , wherein the cross-linking agent is selected from the group consisting of divinyl sulfone, multiepoxides and diepoxides.
9. A process according to claim 1 , wherein the cross-linking agent is 1,4-butanediol diglycidyl ether (BDDE).
10. A process according to claim 1 , further comprising the steps of:
(d) subjecting the precipitated, cross-linked HA product from step (c) to non-precipitating conditions; and
(e) isolating the cross-linked HA product in non-precipitated form.
11. A process according to claim 1 , comprising a step of sterilizing the cross-linked HA product.
12. The process according to claim 1 , comprising the preparation of a desired shape of the activated HA obtained in step (a) prior to the final cross-linking in step (c).
13. The process according to claim 12 , wherein the preparation of a desired shape of the activated HA obtained in step (a) occurs prior to the removing of unreacted cross-linking agent(s) from the activated HA in step (b).
14. The process according to claim 12 , wherein the desired shape is particles having a size of 0.1 - 5.0 mm.
15. The process according to claim 12 , wherein the desired shape is a string, a net, or a film.
16. The process according to claim 12 , wherein the desired shape is a string, said string having a ratio between its length and its width of 5:1 or higher.