Amide cross-linking: an alternative to glutaraldehyde fixation

Area of Science:

• Biomaterials science
• Tissue engineering
• Biomedical engineering

Background:

• Standard glutaraldehyde fixation of bioprosthetic tissues forms Schiff-base bonds, which can induce toxic reactions and are prone to degradation.
• A new fixation method, Ultifix, utilizes amide bond formation for enhanced stability and reduced toxicity.
• The Ultifix process involves a coupler, coupling enhancer, and optional coupling agents to create stable cross-links.

Purpose of the Study:

• To evaluate the cross-linking efficacy of the Ultifix method on bioprosthetic heart valve tissues.
• To assess the resistance of Ultifix-fixed tissues to calcification in a rat model.
• To compare the performance of Ultifix fixation with the standard glutaraldehyde fixation method.

Main Methods:

• Porcine aortic roots and pericardium were fixed using Ultifix components: 1-ethyl-3(-3 dimethyl aminopropyl) carbodiimide hydrochloride (EDC) as coupler, N-hydroxysulfosuccinimide (sulfo-NHS) as enhancer, and 1,6-hexane diamine (DIA) and suberic acid (SUA) as coupling agents.
• Fixed tissues were tested for resistance to thermal denaturation and enzymatic digestion.
• Implantation in rats for up to 16 weeks evaluated resistance to calcification.

Main Results:

• Ultifix effectively stabilized and cross-linked porcine aortic roots and pericardium, comparable to glutaraldehyde fixation.
• Ultifix-fixed tissues exhibited significantly less calcification compared to glutaraldehyde-fixed tissues, particularly in valve cusps and pericardium.
• No toxic by-products were observed with the Ultifix method, unlike glutaraldehyde.

Conclusions:

• The Ultifix process provides a viable, safer alternative to glutaraldehyde for bioprosthetic heart valve fixation.
• Ultifix fixation enhances tissue durability and significantly reduces the risk of calcification.
• This method holds promise for improving the long-term performance and safety of bioprosthetic implants.