Conductive polymeric biomaterials for tissue regeneration applications

Abstract

Tissue engineering involves materials science, bioengineering, and regenerative medicine and many other disciplines. In the early stage, it aims to develop functional biological alternatives that improve, or maintain the function of lost or damaged tissue by combining the scaffold, cells, and biological molecules (such as growth factors). In addition, the ultimate goal of tissue engineering is to regenerate or repair damaged tissues with the help of the biological substitutes. Therefore, the tissue engineering scaffold should mimic the property, structure of the damaged tissue and mimic the extracellular matrix to support cell survival and growth to improve the tissue function. Moreover, the scaffold should also enhance cell proliferation and guide differentiation to regenerate or repair damaged tissues. Over the years, numerous studies have demonstrated that electrical signals can influence cellular behavior and function and conductive materials can enhance cell proliferation and guide differentiation of stem cells through promoting intercellular signaling. Traditional polymers have good process property, biodegradability, and good biocompatibility. So they are most widely used in tissue engineering, but traditional polymers are insulators, which cannot respond to signal transmission between cells to further control cellular activities, such as cell proliferation, migration and differentiation. However, researchers have discovered a variety of electrically conducting polymers in recent decades, such as polyaniline (PANi), polypyrrole (PPy), polythiophene, and their derivatives (mainly aniline oligomers and poly(3,4-ethylenedioxythiophene)) which have good biocompatibility and excellent electrical conductivity. They have been widely used in biomedical fields including drug delivery systems, biosensors, neural implants, and biological actuator, mostly used in the field of tissue engineering scaffolds. Moreover, their excellent electrical conductivity can promote cell adhesion and proliferation at the interface between the polymer and tissue by electrical stimulation, thereby promoting tissue growth. Therefore, the field of tissue engineering by conductive polymeric biomaterials has received more and more attention. However, the pure conductive polymers are brittle and their poor processability limits their applications in tissue engineering. Therefore, composite conductive polymeric biomaterials have been developed based on the above-mentioned conductive polymers and biocompatible degradable polymers, which have excellent biocompatibility, electrical conductivity, and processability. This review will summarize a variety of composite conductive polymeric biomaterials used in tissue engineering, such as pure conducting polymers, conducting blends or composite films, conducting copolymer films, conducting nanofibers, conducting hydrogels, and conducting composite three-dimensional (3D) scaffolds. In addition, recent research in tissue engineering has found that these conductive polymeric biomaterials can be used in various electrical signal sensitive tissues engineering including bone, muscle, nerve and cardiac tissue engineering. The above aspects will be discussed in detail in this paper.