Incorporation of F-MWCNTs into electrospun nanofibers regulates osteogenesis through stiffness and nanotopography

Nanotopography and stiffness are major physical cues affecting cell fate. However, the current nanofiber modifications techniques are limited by their ability to control these two physical cues irrespective of each other without changing the materials' surface chemistry. For this reason, the isolated effects of topography and stiffness on osteogenic regulation in electrospun nanofibers have been studied incompletely. Here, we investigated 1. how functionalized multiwall carbon nanotubes (F-MWCNTs) loaded in Polycaprolactone (PCL) nanofibers control their physical properties and 2. whether the resulting unique structures lead to distinctive phenotypes in bone progenitor cells. Changes in material properties were measured by high-resolution electron microscopes, protein adsorption and tensile tests. The effect of the developed structures on human mesenchymal stem cell (MSC) osteogenic differentiation was determined by extensive quantification of early and late osteogenic marker genes. It was found that F-MWCNT loading was an effective method to independently control the PCL nanofiber surface nanoroughness or stiffness, depending on the applied F-MWCNT concentration. Collectively, this suggests that stiffness and topography activate distinct osteogenic signaling pathway. The current strategy can help our further understanding of the mechano-biological responses in osteoprogenitor cells, which could ultimately lead to improved design of bone substitute biomaterials.