Functional nanostructured chitosan coatings for medical instruments and devices

Abstract

Disclosed herein is an approach for coating a biocompatible material, in particular chitosan, onto a surface in need thereof. This approach results in a coating that is highly uniform, even on irregular surfaces, and enables ready adjustment of the morphology of the coated material. A convenient means to add a functional property to the biocompatible material by incorporation of functional additives is also provided.

What is claimed: 
     
         1 . A method for coating a biopolymer in an adjustable morphology onto a metal-based surface in need thereof comprising:
 providing an electrolyte, said electrolyte comprising the biopolymer which is dissolved in a non-aqueous solvent system containing a supporting electrolyte and at least one biopolymer functional additive;   providing a negative counter electrode, a reference electrode and a positive working electrode;   contacting said electrolyte with the counter electrode, reference electrode, and working electrode; and   applying an electrical potential and current,   such that the biopolymer deposits onto the surface of said positive working electrode in order to form a coating of said biopolymer and the functional additive in an adjustable morphology.   
     
     
         2 . The method of  claim 1 , wherein said biopolymer is chitosan. 
     
     
         3 . The method of  claim 2  further comprises adjusting a pH of said electrolyte to a pH of less than 6.5. 
     
     
         4 . The method of  claim 3 , wherein the pH of said electrolyte is adjusted to pH 4 to 4.5. 
     
     
         5 . The method of  claim 1 , wherein said non-aqueous solvent system is propylene carbonate: ethylene glycol in a ratio of 1:4 v/v. 
     
     
         6 . The method of  claim 1 , wherein the supporting electrolyte comprises LiClO 4 , KCL, KNO 3 , HCl, NaOH, tetraalkylammonium salts or a combination thereof. 
     
     
         7 . The method of  claim 6 , wherein a concentration of the supporting electrolyte is 5.5 mM to 55 mM. 
     
     
         8 . The method of  claim 1 , wherein said surface of the positive working electrode is a conductive surface comprising pure metals or metal alloys. 
     
     
         9 . The method of  claim 8 , wherein said surface of the positive working electrode is stainless steel-based or titanium-based. 
     
     
         10 . The method of  claim 2 , wherein the morphology of chitosan coating includes one or more of particles, wires, rods, flakes, ribbons, flower-like, urchin-like, multipods or tubes. 
     
     
         11 . The method of  claim 1 , wherein said at least one functional additive is 5-florouracil. 
     
     
         12 . The method of  claim 1 , wherein said at least one functional additive is calcium carbonate. 
     
     
         13 . The method of  claim 11 , wherein the ratio of said biopolymer to said 5-florouracil is about 1:8. 
     
     
         14 . The method of  claim 12 , wherein the ratio of said biopolymer to said calcium carbonate is about 1:5. 
     
     
         15 . A medical device coated by the method of  claim 1 , wherein the medical device is configured for implantation or insertion into an animal in need thereof.