Polysaccharides-based 3D porous materials with conductive properties as biomedical scaffold

As the population ages, the replacement of tissues by prosthesis or artificial devices has become a primary concern. In addition to provide mechanical support, two features are extensively studied in the biomaterial field to favour the colonization of porous materials: (i) functionalization and elution of drug or protein that induce healing effects and (ii) having well-defined mechanical properties, close to the reconstructed tissue.  A recent development in the field of biomaterials design is the consideration of their electrical properties. Indeed, the conductivity of tissues (ventricular muscle, nerve, etc...) typically ranges from 0.01 to 0.8 S/m ( Wiley Encyclopedia of Biomedical Engineering, Copyright & 2006 John Wiley & Sons). Conductive biomaterials are a member of a new generation of ”smart” biomaterials, allowing direct transference of electrical, electrochemical and electromechanical stimuli to cells. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a biocompatible conjugate polymer, has been reported as an ideal substrate for the growth and electrical stimulation of osteogenic cells. 

In this work, we have developed new conductive 3D porous materials based on compact polyelectrolyte complexes (CoPECs) using chitosan (CHI) and hyaluronic acid (HA) and ethylenedioxythiphene (EDOT). First, fully screened HA/CHI complex precursors were prepared at high NaCl concentration. By applying a salinity-change phase separation process, i.e. water casting and thorough rinsing, we have successfully obtained 3D HA/CHI porous material with a pore diameter size of 40 μm and a storage modulus (G') of 0.7 kPa. Subsequent cross-linking further enhanced the G' to 15 kPa. EDOT was then polymerized on the surface of the pores, resulting in an electrical conductivity of 1.9 ± 0.7 10^-5 S.cm^-1. Finally, NIH3T3 fibroblasts were seeded on the three types of HA/CHI, native, cross-linked and PEDOT-functionalized. PEDOT:HA/CHI demonstrated optimal cell viability, exhibiting a high level of adherent cells on the surface and facilitating enhanced fibroblast colonization within the porosity.