Electrically conducting collagen and collagen–mineral composites for current stimulation

Abstract

Bifunctional films with higher electrochemical and bioactive properties have many promising applications including tissue engineering, drug delivery, nerve regeneration and bone healing. Since bone possesses natural bio-potential and electromechanical properties, the idea of utilizing small electrical pulses to induce bone-tissue growth has been explored in recent decades. Studies have revealed that electric stimulation (in the order of μV) has positive effects on the osteogenesis, and enhances the mineral formation in osteoblast-like cells. However, the mechanisms behind these effects are not well understood. Electric stimulation is generally performed through the implantation of metal electrodes that need to be removed after the treatment. This sometimes requires surgery that can lead to complications including infection and damaging newly formed bone-tissue. Therefore, in the search for new implant materials that are bioactive (allowing different cells to grow over it) and electrically conductive (to perform electrical stimulation), a composite material has been synthesized by integrating the electro-active properties of the conducting polymer (poly-3,4-ethylenedioxythiophene, doped with polystyrene sulfonate, PEDOT:PSS) with the biological properties of collagen (protein, which is present in the cornea) and collagen–calcium phosphate membranes (which mimics the composition of bone). It is shown that by varying the concentration of PEDOT:PSS, the composite (collagen–PEDOT:PSS) or the hybrid (collagen–hydroxyapatite–PEDOT:PSS) membrane could be altered to be highly biocompatible and highly electrically conductive.