Biomaterials with enhanced properties and devices made therefrom

Abstract

Biomaterials with enhanced properties such as improved strength, flexibility, durability and reduced thickness are useful in the fabrication of biomedical devices, particularly those subjected to continuous or non-continuous loads where repeated flexibility and long-term durability are required. These enhanced properties can be attributed to elevated levels of elastin, altered collagen types, and other biochemical changes which contribute to these enhanced properties. Examples of devices which would be improved by use of such tissue include heart valves, including percutaneous heart valves, and vascular grafts, patches and the like. Such enhanced materials can be sourced from specific populations of animals, such as neonatal calves, or in range-fed adult cattle, or can be fabricated or created from cell populations exhibiting such properties. In one embodiment, glutaraldehyde-fixed neonatal pericardial tissue is used to create leaflets in a percutaneous heart valve, and may be used without chemical fixation, with or without processes to remove residual cellular membranes, and utilized as a scaffold material for tissue engineering.

What is claimed is: 
     
         1 . An isolated portion of neonatal calf pericardium tissue comprising:
 an elevated elastin content characteristic of an animal less than one year old; and   a collagen composition characteristic of a calf less than 12 months old.   
     
     
         2 . The isolated tissue of  claim 1  wherein amino acid residues in the tissue portion are cross-linked. 
     
     
         3 . The isolated tissue portion of  claim 1  having a thickness of between approximately 0.05-0.250 mm. 
     
     
         4 . The isolated tissue portion of  claim 1  wherein the tissue is acellular. 
     
     
         5 . The isolated tissue portion of  claim 1  having a pepsin digestion of more than 20%. 
     
     
         6 . The isolated tissue portion of  claim 1  having a modulus of greater than 20 MPa. 
     
     
         7 . The isolated tissue portion of  claim 1  wherein the elastin content is greater than 300 micrograms per milligram dry weight and a ratio of hydroxyproline to proline is greater than 1.0. 
     
     
         8 . The isolated tissue portion of  claim 1  wherein the tissue is a component of a prosthetic heart valve. 
     
     
         9 . The isolated tissue portion of  claim 1  wherein the tissue is a component of a surgical graft. 
     
     
         10 . A method to obtain neonatal calf pericardium tissue for human implantation comprising:
 excising a portion of calf pericardium tissue sized to be implanted in a human patient, and wherein the tissue has an elevated elastin content characteristic of a calf less than 12 months old, and a collagen composition characteristic of a calf less than 12 months old, and   treating the tissue portion to reduce immunogenicity.   
     
     
         11 . The method of  claim 10  further comprising the step of sizing the tissue portion to be used as a prosthetic heart valve or portion thereof. 
     
     
         12 . The method of  claim 10  further comprising the step of cross-linking amino acid residues in the tissue. 
     
     
         13 . The method of  claim 12  wherein the cross-linking step is treatment with glutaraldehyde. 
     
     
         14 . The method of  claim 10  wherein the tissue has a thickness of between approximately 0.05 to 0.250 mm. 
     
     
         15 . The method of  claim 10  wherein the calf is less than 30 days old. 
     
     
         16 . The method of  claim 12  further comprising the step of testing the tissue for a properly selected from the group of elastin content, hydroxproline to proline ratio, modulus, and thickness or combinations thereof. 
     
     
         17 . The method of  claim 12  wherein the pepsin digestion of the tissue is more than 20%. 
     
     
         18 . A system for percutaneous insertion of neonatal calf pericardium tissue transplant comprising:
 a catheter designed for peripheral vascular access and sized to traverse a portion of human vasculature, and   an isolated portion of calf pericardium tissue of  claims 1 - 9  confined by the catheter into a configuration having a reduced profile to pass through the vasculature.   
     
     
         19 . The system of  claim 18  where in the tissue portion is a component of a prosthetic heart valve. 
     
     
         20 . The system of  claim 19  wherein the prosthetic heart valve is releasably attached to the distal end of the catheter. 
     
     
         21 . The system of  claim 18  wherein the reduced profile is approximately 16 French or less.