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Static Degradation of Electrospun Polycaprolactone Scaffolds
Emily Clement, Depts. of Biomedical Engineering and Electrical Engineering, Connor Donlan, Sam Cole, Sarah K. Saunders, and Johana Bracamonte, with Dr. Joao Soares, Dept. of Mechanical Engineering
Introduction: Engineered tissue vascular grafts (ETVGs), composed of cells seeded on a biodegradable scaffold, can be used to replace non-functional blood vessels. The scaffold acts as a replacement for the extracellular matrix, providing structural support to the developing tissue. A common biodegradable scaffold material is polycaprolactone (PCL). The main degradation mechanism of PCL is hydrolysis, which can be catalyzed by the use of NaOH solutions. Acceleration techniques must be employed to obtain information about the degradation in shorter observation times. In this study, we will compare the effect of degradation on physical and mechanical properties from samples degraded in PBS solutions (that mimics the pH of biological environments), and alkaline NaOH solutions. We hypothesize that the accelerated degradation profiles can be correlated to degradation profiles under in vivo like conditions. Methods: This study focuses on PCL (PCL 80,000 g/mol) 3mm electrospun scaffolds. Accelerated conditions were produced by submerging the scaffolds in increased NaOH solutions. The weight loss, elastic modulus, and microstructure of the scaffolds were assessed after vacuum drying at 0, 7, 14, 21, and 42 days. Phosphate-buffered saline (PBS) solution was used to replicate physiological-like pH conditions. This group was tested for elastic modulus, weight loss, and thickness at 0, 3, and 6 months. Results: The rate of change in mass, fiber orientation, and mechanical stiffness increased as the alkalinity of the liquid media increased to pH 12.45. Changes in the mechanical properties of the scaffolds became noticeable after 3 weeks of degradation. A decrease in mass stiffness was observed following a steep decrease in mass. At 6 weeks of degradation, the samples experienced a 20% decrease from the original mass and a 50% drop in membrane stiffness. The scaffolds swelled shortly after degradation began, but the swelling decreased as the mass decreased. In the non-accelerated degradation group, the scaffolds exhibited an average mass loss of 10 +/- 7% with no significant changes to mechanical properties. The scaffold thickness swelled to 40 +/- 20%, aligning with our previous works that showed scaffold swelling decreases at a larger pH. Conclusions: If the degradation of PCL scaffolds in physiological pH conditions follows the same trend as those in accelerated conditions, a stage of pronounced decrease in mass will be accompanied by a significant decrease in membrane stiffness and porosity. We hypothesize that the accelerated and non-accelerated degradation profiles are equivalent, meaning accelerated degradation can be used as a base to predict a scaffold’s behavior in physiological conditions.
Joao Soares, Ph.D.
Virginia Commonwealth University. Undergraduate Research Opportunities Program
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