Biomechanical studies on aliphatic physically crosslinked poly(urethane urea) for blood contact applications

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Mechanical Engineering

Background:

• Aliphatic poly(urethane urea)s (PUUs) are crucial for biomedical applications due to their tunable properties.
• Assessing long-term stability under physiological and accelerated degradation conditions is vital for device longevity.

Purpose of the Study:

• To develop and characterize novel hydrophobic, physically crosslinked aliphatic PUUs.
• To evaluate the biomechanical properties and degradation resistance of these PUUs under various stress and hydrolytic conditions.
• To compare the performance of the developed PUU against poly(ether urethane urea)s for blood-contact applications.

Main Methods:

• Synthesis and physical characterization of aliphatic PUUs.
• Environmental stress corrosion cracking (ESC) testing in Ringer's solution and phosphate-buffered saline at 50°C.
• Mechanical testing (tensile strain) and modulus analysis after aging in papain enzyme and buffer.
• Accelerated hydrolytic degradation testing in boiling alcoholic potassium hydroxide solution.

Main Results:

• The developed poly(urethane urea) exhibited resistance to ESC in hydrolytic media.
• Strain-induced aging in papain enzyme and buffer led to an increased elastic modulus due to chain reorganization.
• The polymer showed no degradation in accelerated hydrolytic chemical degradation tests.
• Poly(ether urethane urea)s displayed inferior properties, undergoing degradation in boiling alcoholic potassium hydroxide solution.

Conclusions:

• The candidate poly(urethane urea) HFL 18-PUU demonstrates superior biomechanical stability and resistance to degradation compared to poly(ether urethane urea)s.
• HFL 18-PUU is a promising elastomer for long-term, biomechanically sensitive blood contact applications.
• Potential applications include heart valves and blood pump diaphragms for left ventricular assist devices.