Schematic of PEDOT:PSS scaffold preparation and infiltration with osteogenic precursor cells.
Scanning electron microscopy images of (a) a pristine PEDOT:PSS scaffold and (b) a PEDOT:PSS scaffold where osteogenic precursor cells (MC3T3-E1) were grown for 7 days. Courtesy of Imperial College London.When fractured bones cannot readily repair or need replacement after disease or damage, clinicians increasingly look to tissue engineering for answers. The approach requires scaffold materials that can be implanted into the body, fill the gap left by damaged or diseased bone, and act as a support for regrowing tissue. Researchers have come up with a promising scaffold material in the form of a conjugated polymer, PEDOT:PSS (or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) [Guex et al., Acta Biomaterialia (2017), doi: 10.1016/j.actbio.2017.08.045].
PEDOT:PSS is well known as a good candidate for biomedical applications, so the team from Imperial College London, Cornell University, and Ecole Nationale Supérieure des Mines de Saint Etienne thought it might make a good scaffold for bone precursor cells.
“There is some evidence that bone healing can be enhanced by electrical stimulation of bone cells,” explains first author of the study, Anne Géraldine Guex. “We hypothesized that an electrically conductive scaffold could support bone growth, since an externally applied electrical signal could be transmitted directly to the cells, enhancing cell-cell communication and aiding tissue formation.”
The researchers created their novel scaffold by freezing a suspension of PEDOT:PSS in water. Ice crystals form, which are surrounded by the polymer. When the mixture is freeze-dried, the ice crystals leave behind a network of interconnected pores. This highly porous architecture allows bone cells to infiltrate into the scaffold.
“We found that osteogenic precursor cells (MC3T3-E1) cultured on PEDOT:PSS scaffolds survive, grow, and differentiate into bone cells,” says Guex. “What distinguishes these scaffolds from other polymeric materials is their inherent electrical conductivity.”
Moreover, the team found that the PEDOT:PSS scaffolds maintained their structural integrity even after a month. Along with the easy processing of this polymer using freeze-drying, the researchers believe their approach is straightforward, quick, and cost-effective.
“We think that the main advantage of our approach lies in the processing of the PEDOT:PSS dispersion,” points out Guex. “Freeze-drying is relatively easy and allows for the development of scaffolds with pore size and architecture can be custom-tailored.”
But while the findings suggest that PEDOT:PSS has potential as a scaffold material, the researchers say that a better understanding of how precursor cells differentiate into mature, mineralized bone tissue is needed.
“We need to optimize and understand the mechanisms of osteogenic differentiation on PEDOT:PSS and elucidate the complex effect of the electric conductivity on the cell fate,” she says. “We think that, by investigating this new group of materials, we can significantly contribute to a better understanding of cell-material interactions, the effect of electrical stimulation on cell fate and, ultimately, provide new materials for medical applications.”