Wettability of electrospun fibers is one of the key parameters in the biomedical and filtration industry. Within this comprehensive study of contact angles on three-dimensional (3D) meshes made of electrospun fibers and films, from seven types of polymers, we clearly indicated the importance of roughness analysis. Surface chemistry was analyzed with X-ray photoelectron microscopy (XPS) and it showed no significant difference between fibers and films, confirming that the hydrophobic properties of the surfaces can be enhanced by just roughness without any chemical treatment. The surface geometry was determining factor in wetting contact angle analysis on electrospun meshes. We noted that it was very important how the geometry of electrospun surfaces was validated. The commonly used fiber diameter was not necessarily a convincing parameter unless it was correlated with the surface roughness or fraction of fibers or pores. Importantly, this study provides the guidelines to verify the surface free energy decrease with the fiber fraction for the meshes, to validate the changes in wetting contact angles. Eventually, the analysis suggested that meshes could maintain the entrapped air between fibers, decreasing surface free energies for polymers, which increased the contact angle for liquids with surface tension above the critical Wenzel level to maintain the Cassie-Baxter regime for hydrophobic surfaces.

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This study represents the unique analysis of the electrospun scaffolds with the controlled and stable surface potential without any additional biochemical modifications for bone tissue regeneration. We controlled surface potential of polyvinylidene fluoride (PVDF) fibers with applied positive and negative voltage polarities during electrospinning, to obtain two types of scaffolds PVDF­(+) and, PVDF(−). The cells’ attachments to PVDF scaffolds were imaged in great details with advanced scanning electron microscopy (SEM) and 3D tomography based on focus ion beam (FIB-SEM). We presented the distinct variations in cells shapes and in filopodia and lamellipodia formation according to the surface potential of PVDF fibers that was verified with Kelvin probe force microscopy (KPFM). Notable, cells usually reach their maximum spread area through increased proliferation, suggesting the stronger adhesion, which was indeed double for PVDF(−) scaffolds having surface potential of −95 mV. Moreover, by tuning the surface potential of PVDF fibers, we were able to enhance collagen mineralization for possible use in bone regeneration. The scaffolds built of PVDF(−) fibers demonstrated the greater potential for bone regeneration than PVDF­(+), showing after 7 days in osteoblasts culture produce well-mineralized osteoid required for bone nodules. The collagen mineralization was confirmed with energy dispersive X-ray spectroscopy (EDX) and Sirius Red staining, additionally the cells proliferation with fluorescence microscopy and Alamar Blue assays. The scaffolds made of PVDF fibers with the similar surface potential to the cell membranes promoting bone growth for next-generation tissue scaffolds, which are on a high demand in bone regenerative medicine.

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A single‐step electrospinning approach enables controlling surface potential of fibers by changing voltage polarities during scaffolds production to enhance cells biointegration. This innovative and facile way of fibers production regulates the interfacial properties to enhance cells adhesion and filopodia formation on fibrous tissue scaffolds for possible bone regeneration. Tuning surface chemistry of polycaprolactone (PCL) by altering voltage polarity during electrospinning allows to double the surface potential on fibers up to 145 mV, which is directly measured using Kelvin probe force microscopy. The obtained surface potential on PCL fibers is directly correlated with surface chemistry analyzed at the grazing angle by X‐ray photoelectron spectroscopy, showing lower oxygen content at PCL fiber surfaces, produced with negative voltage polarity, PCL (−). These fibers create well‐engineered scaffolds that are able to increase significantly cell proliferation that is visualized with fluorescence microscopy, and filopodia formation on positively charged fibers, investigated with high‐resolution scanning electron microscopy. This work introduces electrospun PCL fibers without a need for chemical modification to tune electrostatic interactions between cells and fibrous scaffolds for biomaterials used in regenerative medicine.