Nonwoven Scaffolds Under Tension: In Situ High-Resolution Ultrasound Observation of Microstructure Evolution in the Volume

Fibrous scaffolds represent the basic material for tissue engineering, where creation of matrices with predictable properties is an important issue. Typically, the assessment of scaffold characteristics, including the mechanical behavior, is conducted in the air environment that is far from the natural physiological conditions in a living organism, despite possible differences in the properties obtained in dry and water-filled specimens. The studies of the mechanical behavior of scaffolds in the wet environment are limited by the properties of visualization methods. The optimal method for studying fibrous objects in the wet environment is ultrasonic techniques, for which water immersion is a prerequisite for the experiment. Herein, a high-frequency (200 MHz) acoustic microscopy is combined with a horizontal mechanical testing machine for in situ visualization of microstructural transformation in the volume of elastic and rigid electrospun scaffolds under tension. For the first time, the results show that in situ ultrasound monitoring provides high-resolution imaging of the internal microstructure in water-filled specimens. This work provides the foundation for future experimental setups for characterization of tissue-engineered constructs in the conditions close to those in a living organism.