Influence of scaffold forming techniques on stress relaxation behavior of polycaprolactone scaffolds

ABSTRACT This study evaluated the effect of scaffold processing methods on viscoelastic properties of polycaprolactone (PCL), a frequently explored biomaterial in tissue engineering. 80 kDa and 45 kDa PCL scaffolds were synthesized using salt leaching and electrospinning techniques. Also, films were formed by air drying. Scanning electron microscopy analysis confirmed that salt leached scaffolds had open pore architecture and electrospun scaffolds had randomly distributed uniform fibers. Using the tensile test results in phosphate buffered saline (pH=7.4) and 37° C, ramp‐hold tests were performed for five stages by setting the strain rate to be 1%s −1 for 2 s followed by 58 s of hold. Also, tests were performed at various strain rates and total strain. Salt leached scaffolds of same MW showed less relaxation in each stage relative to electrospun scaffolds. 45 kDa salt leached scaffolds relaxed more than 80 kDa scaffolds. Stress accumulated in each stage was more in films than in scaffolds. However, relaxation function appeared similar between films and electrospun fibers. Strain rate and amount of applied strain had significant effect on relaxation characteristics; 0.6%s −1 strain rate had higher accumulated stress than 1%s −1 and 3%s −1 . Increased amount of loading had significant effect in the first stage with repetitive relaxation characteristics in subsequent stages. SEM analysis of tested samples showed no change in the microstructure with the exception of a few locations where pores oriented in the direction of the pull. In summary, viscoelastic characteristics vary based on the type of scaffold processing used, despite use of the same polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4237–4244, 2013