Cellulose hydrogel compositions and contact lenses for corneal applications
The present invention provides cellulose hydrogels having one or more of the following properties: high water content, high transparency, high oxygen permeability, high biocompatibility, high tensile strength and desirable thermal stability. The present invention further provides a process for preparing a cellulose hydrogel comprising (i) a step of activating cellulose, in which the activating step comprises contacting the cellulose with a solvent to activate the cellulose for a time duration from about 2 hours to about 30 hours; (ii) substantially dissolving the activated cellulose to form a solution; and (iii) gelling the solution to form a gel, in which the gelling step comprises allowing the solution to gel in an environment comprising a relative humidity from about 30% to about 80% at 35° C.
1. A process for preparing a wet cellulose hydrogel, said process comprising:
(i) activating cellulose, wherein said activating step comprises contacting the cellulose with a solvent to activate the cellulose for a time duration from about 2 hours to about 30 hours;
(ii) substantially dissolving the activated cellulose to form a solution; and
(iii) gelling the solution to form a gel, wherein said gelling step comprises allowing the solution to gel in an environment comprising a relative humidity from about 30% to about 80% at 35° C., wherein a cellulose content of the gel is from about 1% to about 10% by weight, wherein
said wet cellulose hydrogel comprises
(a) a tear strength of from about 1.25 N/mm to about 3 N/mm;
(b) a Young's modulus of from about 1000 kPa to about 1600 kPa;
(c) a tensile strength in the range of from about 900 kPa to about 4000 kPa; and
(d) an oxygen permeability from about 55 to about 150 Dk.
2. The process of claim 1 , wherein (i) said activating step comprises contacting the cellulose with the solvent to activate the cellulose from about 10 hours to about 20 hours; and (ii) said gelling step comprises allowing the solution to gel in an environment comprising a relative humidity from about 70% to about 80% at 35° C.
3. The process of claim 1 , wherein the solution gels in a mold and is later removed and optionally washed.
4. The process of claim 3 , wherein the mold is a contact lens mold.
5. The process of claim 1 , wherein the cellulose content of the gel is from about 2% to about 7% by weight.
6. The process of claim 1 , wherein the cellulose content of the gel is from about 2% to about 5% by weight.
7. The process of claim 1 , wherein the cellulose content of the gel has a denaturation temperature of at least about 70° C.
8. The process of claim 7 , wherein the denaturation temperature exceeds about 250° C. and less than about 300° C.
9. The process of claim 1 , wherein the wet cellulose hydrogel has a strain to failure of from about 40% to about 160%.
10. The process of claim 1 , wherein the wet cellulose hydrogel has a suture retention strength of from about 0.1 N/mm to about 3.5 N/mm.
11. The process of claim 1 , wherein the wet cellulose hydrogel has a puncture resistance of from about 100 kPa to about 300 kPa.
12. The process of claim 1 , wherein the cellulose is from a source selected from the group consisting of plant, wood pulp, cotton pulp, microbial, and combinations thereof.
13. The process of claim 1 , wherein the wet cellulose hydrogel comprises one or more cellulose fiber layers.
14. The process of claim 1 , wherein a transparency of the wet cellulose hydrogel is at least 95% at 550 nm.
15. The process of claim 1 , wherein the wet cellulose hydrogel has a thickness of from about 50 to about 250 microns.
16. The process of claim 1 , wherein the wet cellulose hydrogel has a refractive index of from about 1.30 to about 1.50.
17. The process of claim 1 , wherein the wet cellulose hydrogel comprises bacterial cellulose.
18. The process of claim 1 , wherein activating cellulose comprises a single-step activation step; wherein the single-step activation step is devoid of solvent exchange steps.
19. The process of claim 1 , wherein a transparency of the wet cellulose hydrogel exceeds 85% at 550 nm.