Electrical and Physical Stimulation in Tissue Engineering

The presence of electric and magnetic field in the human body and their crucial role on different functions of body had been proven. Bioelectricity in the body is created by the ion concentration difference in the opposite sides of the cell membrane, which causes the electric field generation in the cell membrane and endows specific potential to the cells. Endogenous electric fields can influence many biological processes during fetal development, tissue hemostasis, tissue regeneration, and cancer creation and metastasis. The existence of electric fields in the body and their widespread influence on cell and tissue functions has drawn the attention toward the application of electrical stimulation to improve tissue damages not only in tissue engineering but also in clinical applications. In this chapter, firstly, the role of endogenous electric fields in the biological milieu is reviewed, and then the influence of exogenous electric fields on cell behavior and supracellular phenomena including cell adhesion, migration, orientation, and apoptosis as well as on vascularization is discussed. In the following, different methods of application of electrical stimulation in vitro and in vivo are reviewed, in which details of different electrical stimulation approaches, that is, direct, capacitive, and inductive coupled electrical stimulation has been provided. Moreover, about direct electrical stimulation, the common applying approaches including the direct electrode insertion, the salt bridges systems, and the microfluidic devices are discussed. In the next section, the relation between electrical stimulation and bone tissue regeneration is investigated, and more specifically, the effects of electrical stimulation on preosteoblast and osteoblast cells and the parameters interpreting bone tissue regeneration, like ossification, vascularization, and inflammation are discussed. Finally, the clinical applications of electrical stimulation and bone growth stimulator devices and their effects on healing on nonunion or delayed-union fractures have been reviewed and details of the invasive, semiinvasive, and noninvasive bone growth stimulators are debated.