Chitosan foam medical devices and methods

1. A method of making a solid foam wound dressing, consisting essentially of:

(I) introducing gas bubbles into an aqueous solution to form an aqueous foam with uniformly distributed gas bubbles therein, wherein the aqueous solution comprises chitosan, at least one protic acid, and at least one surface active agent;

(II) freezing the aqueous foam prepared in step (I) to form a frozen foam at a pressure of between about 100 mTorr to about 750 Torr before the gas bubbles collapse or coalesce and to expand the gas bubbles in the aqueous foam; and

(III) dehydrating the frozen foam to form a solid foam with a uniform structure from bottom to top as well as from side to side,

wherein step (II) occurs immediately after step (I).

2. The method of claim 1 , wherein said dehydrating the frozen foam comprises freeze drying the frozen foam.

3. The method of claim 1 , further comprising compressing the solid foam.

4. The method of claim 3 , further comprising imprinting the compressed solid foam with pattern or texture to provide a microporous surface.

5. The method of claim 4 , further comprising imprinting the compressed solid foam with soft substrates having a pattern or texture.

6. The method of claim 1 , wherein the protic acid is a hydrogen donator acid.

7. The method of claim 6 , wherein the hydrogen donator acid is selected from the group consisting of formic acid, acetic acid, propionic acid, lactic acid, succinic acid, glutamic acid, tartaric, citric acid, hydrochloric acid, nitric and, and phosphoric acid.

8. The method of claim 1 , wherein the surface-active agent is anionic, cationic, non-ionic, or amphoteric.

9. The method of claim 8 , wherein the cationic surface-active agent is selected from the group consisting of fatty amine halides, cetyl trimethylammonium halides, cetylpyrindium halides, benzalkonium halides, benzethonium halides, and polyethoxylated tallow amine.

10. The method of claim 1 , wherein the surface-active agent is antimicrobial and antiviral.

11. The method of claim 1 , wherein the gas is selected from the group consisting of air, nitrogen, helium, hydrogen, argon, and carbon dioxide.

12. The method of claim 1 , wherein the gas bubbles are introduced by mixing, beating, agitating, aerating, whipping, or injecting the gas into the aqueous solution.

13. The method of claim 1 , wherein the wound dressing is capable of promoting hemostasis.

14. The method of claim 1 , wherein the wound dressing is capable of promoting wound healing.

15. The method of claim 1 , wherein the wound dressing is antimicrobial and antiviral.

16. The method of claim 1 , wherein the wound dressing is capable of self adhering to wet tissues.

17. The method of claim 1 , wherein the solid foam is cationic.

18. The method of claim 1 , wherein the aqueous foam has a density of between about 0.40 g/cm 3 to about 0.85 g/cm 3 .

19. The method of claim 1 , wherein the wound dressing is uncompressed and has a density of between about 0.01 g/cm 3 to about 0.02 g/cm 3 .

20. A method of making a solid foam wound dressing, consisting essentially of:

(I) introducing gas bubbles into an aqueous solution to form an aqueous foam, wherein the aqueous solution comprises chitosan, at least one protic acid and at least one surface active agent;

(II) freezing the aqueous foam prepared in step (I) to form a frozen foam at a pressure of between about 100 mTorr to about 750 Torr before the gas bubbles collapse or coalesce and to expand the gas bubbles in the aqueous foam; and

(III) dehydrating the frozen foam to form a solid foam, wherein step (II) occurs immediately after step (I).

21. The method of claim 1 , wherein said freezing the aqueous foam prepared in step (II) is done at a pressure of about 400 mBar, or about 300 Torr.

22. The method of claim 20 , wherein said freezing the aqueous foam prepared in step (II) is done at a pressure of about 400 mBar, or about 300 Torr.