Cellulose-Based Hydrogels and Methods of Making Thereof

• US 20130032059A1
• Filed: 08/03/2011
• Published: 02/07/2013
• Est. Priority Date: 08/03/2011
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Trexler, Morgana M., Graham, Jenna L., Breidenich, Jennifer L., Patrone, Julia B., Patchan, Marcia W., Elisseeff, Jennifer H., Calderon-Colon, Xiomara, Maranchi, Jeffrey P.
• Granted Patent: US 8,871,016 B2
• Time in Patent Office: Days
• US Class Current: 106/164.01
• CPC Class Codes: B29D 11/00038 Production of contact lenses
• CPC Class Codes: C08B 1/003 Preparation of cellulose solutions, i.e. dopes, with different possible solvents, e.g. ionic liquids solutions used in the manufacture of monocomponent artificial filaments or cellulose or derivatives thereof D01F2/02
• CPC Class Codes: C08J 2301/02 Cellulose; Modified cellulose
• CPC Class Codes: C08J 3/075 Macromolecular gels
• CPC Class Codes: C08L 1/02 Cellulose; Modified cellulose
• CPC Class Codes: C08L 101/14 the macromolecular compounds being water soluble or water swellable, e.g. aqueous gels
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 2205/16 Fibres; Fibrils
• CPC Class Codes: C08L 29/04 Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• CPC Class Codes: C08L 33/066 containing -OH groups
• CPC Class Codes: C08L 33/10 Homopolymers or copolymers of methacrylic acid esters
• CPC Class Codes: C08L 33/20 Homopolymers or copolymers of acrylonitrile C08L55/02 takes precedence
• CPC Class Codes: C08L 33/26 Homopolymers or copolymers of acrylamide or methacrylamide
• CPC Class Codes: C08L 39/06 Homopolymers or copolymers of N-vinyl-pyrrolidones
• CPC Class Codes: C08L 71/02 Polyalkylene oxides
• CPC Class Codes: C08L 83/04 Polysiloxanes
• CPC Class Codes: G02B 1/04 made of organic materials, e.g. plastics G02B1/08 takes precedence
• CPC Class Codes: G02B 1/043 Contact lenses
• CPC Class Codes: G02C 7/049 Contact lenses having special fitting or structural features achieved by special materials or material structures

Abstract

The present invention provides cellulose hydrogels having one or more of the following properties: high water content, high transparency, high permeability, high biocompatibility, high tensile strength and an optimal thickness. The present invention further provides a process for preparing a cellulose hydrogel comprising: (i) contacting cellulose with a solvent to activate the cellulose; (ii) optionally removing the solvent from the activated cellulose; (iii) substantially dissolving the activated cellulose to form a solution; (iv) allowing the solution to gel; and optionally (v) drying the gel and rehydrating the gel. The cellulose hydrogel can have many uses, including uses as contact lenses.

Claims

1. A re-wet cellulose hydrogel wherein the hydrogel comprises one or more properties selected from the group consisting of:

a cellulose content of from about 40% to about 65% by weight;

a tensile strength of from about 1000 kPa to about 5000 kPa;

a tear strength of from about 3.0 N/mm to about 12 N/mm;

a strain to failure of from about 20% to about 40%;

a suture retention strength of from about 1.0 N/mm to about 7.0 N/mm;

a transparency that exceeds 85% at 550 nm at 100 microns thickness;

Young'"'"'s modulus of from about 4000 kPa to about 15000 kPa; and

a puncture resistance of from about 3 MPa to about 5 MPa.

2. The hydrogel of claim 1, wherein the hydrogel is in the shape of a contact lens.

3. The hydrogel of claim 2, wherein the cellulose is from a source selected from the group consisting of plant, wood pulp, cotton pulp, microbial, and combinations thereof.

4. The hydrogel of claim 3, wherein the hydrogel comprises one or more cellulose fiber layers.

5. The hydrogel of claim 3, wherein the cellulose concentration is about 55% by weight.

6. The hydrogel of claim 2, wherein the transparency of the hydrogel is at least 95% at 550 nm.

7. The hydrogel of claim 2, wherein the cellulose starting material has a density of about 0.20-0.40 g/cm³ and a moisture content of about 2-6% by weight.

8. The hydrogel of claim 1, further comprising one or more synthetic polymers selected from the group consisting of hydroxyethylmethacrylate (HEMA), poly(hydroxyethyl methacrylate) (PHEMA), polyacrylamide, polyethylene glycol (PEG), polyethyleneoxide (PEO), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), poly(vinyl pyrrolidone) (PVP) and silicones.

9. The hydrogel of claim 1, wherein the hydrogel has a thickness of from about 50 to about 250 microns.

10. The hydrogel of claim 1, wherein the hydrogel has a refractive index of from about 1.30 to about 1.50.

11. The hydrogel of claim 1, wherein the hydrogel has a tear strength of from about 3.0 N/mm to about 12 N/mm.

12. The hydrogel of claim 1, wherein the hydrogel has a cellulose content of about 60% by weight.

13. The hydrogel of claim 1, wherein the cellulose content is about 50% by weight.

14. The hydrogel of claim 1, wherein the hydrogel is a composite comprising microcrystalline cellulose and bacterial cellulose.

15. The hydrogel of claim 1, wherein the hydrogel has a denaturation temperature of at least about 300°

C.

16. A process for preparing a cellulose hydrogel comprising:

(i) contacting cellulose with a solvent to activate the cellulose;

(ii) optionally removing the solvent from the activated cellulose;

(iii) substantially dissolving the activated cellulose to form a solution;

(iv) allowing the solution to gel; and

optionally

(v) drying the gel and rehydrating the gel.

17. The process of claim 16, wherein the solution gels in a mold and is later removed and optionally washed.

18. The process of claim 16, wherein the solvent of (i) is selected from the group consisting of dimethylacetamide, water, methanol, acetone, ethanol and a combination of water and ethanol.

19. The process of claim 16, wherein the cellulose is substantially dissolved in a solvent selected from the group consisting of cupriethylenediamine (CED), cadmiumethylenediamine (Cadoxen), LiCl/dimethylacetamide (LiCl/DMAc), Ca(SCN)₂/water, 1-butyl-3-methylimidazolium chloride (BmimCl), NaOH/water, N-methyl-morpholine-N-oxide (NMMO)/water, and 1-allyl-3-methyllimidazolium chloride.

20. The process of claim 16, wherein the gel is dried by a process selected from the group consisting of freeze drying (lyophilization);

drying in a hot press between two heated platens while applying an amount of pressure;

a solvent exchange process;

supercritical CO₂;

air drying; and

a combination thereof.

21. The process of claim 17, wherein the mold is a contact lens mold.

22. The process of claim 16, wherein the rehydrated hydrogel has a tensile strength of about 1250 kPa to about 3500 kPa.

23. The process of claim 22, wherein the rehydrated gel has a transparency of at least about 95% at 550 nm.

24. A contact lens comprising the rehydrated gel made according to the process of claim 20.

25. A wet cellulose hydrogel wherein the hydrogel comprises one or more properties selected from the group consisting of:

a cellulose content of from about 2% to about 9% by weight;

a tensile strength in the range of from about 50 kPa to about 600 kPa;

a tear strength of from about 0.10 N/mm to about 0.60 N/mm;

a strain to failure of from about 40% to about 80%;

a suture retention strength of from about 0.05 N/mm to about 0.30 N/mm;

a transparency that exceeds 85% at 550 nm;

Young'"'"'s modulus of from about 100 kPa to about 700 kPa; and

a puncture resistance of from about 50 kPa to about 300 kPa.