Nonionic Surfactant as a Tool to Modify Electrospun Fiber Properties for In Vitro Fibrous Connective Tissue Models

Injuries to dense connective tissues, including the knee menisci, contribute to altered joint biomechanics and degeneration. Though meniscal tears are the most common intra-articular knee injury, potential drivers of regenerative treatments remain unknown. Tissue culture scaffolds which effectively recapitulate the fibrous, anisotropic structure and mechanics of meniscus tissue are essential components for in vitro models to investigate meniscus regeneration. Electrospinning poly-ε-caprolactone (PCL) is commonly employed to create meniscus-mimetic scaffolds. However, PCL fiber hydrophobicity often requires post-fabrication treatment to establish adequate hydrophilicity for processing and efficacy in vitro. Nonionic surfactants, like Span80, are common additives in the electrospinning process that are leveraged to increase hydrophilicity in a single step. This study investigates the effects of increasing Span80 concentration, in both unaligned and aligned electrospun fibers, on sample morphology (fiber diameter, alignment), tensile mechanical properties, surface properties (wettability via water contact angle, serum protein adsorption), and meniscal cell adhesion and matrix protein production. A low concentration of Span80 (10%) had a minimal impact on fiber diameter, fiber alignment, and tensile properties, while significantly increasing sample wettability and meniscal cell adhesion and fibronectin production. On the other hand, a higher Span80 concentration (30%) significantly decreased fiber diameter, tensile properties, and cell numbers, especially in aligned scaffolds. Overall, these results illustrate the utility of Span80, in a concentration dependent manner, for modulating surface wettability, protein adsorption, and tensile properties of meniscus-mimetic fibrous scaffolds while maintaining the material-cell compatibility, representing an adaptable in vitro model designed to interrogate cell behavior in a biologically relevant environment.