Due to the presence of electric fields and piezoelectricity in various living tissues, piezoelectric materials have been incorporated into biomedical applications especially for tissue regeneration. The piezoelectric scaffolds can perfectly mimic the environment of natural tissues. The ability of scaffolds which have been made from piezoelectric materials in promoting cell proliferation and regeneration of damaged tissues has encouraged researchers in biomedical areas to work on various piezoelectric materials for fabricating tissue engineering scaffolds. In this review article, the way that cells of different tissues like cardio, bone, cartilage, bladder, nerve, skin, tendon, and ligament respond to electric fields and the mechanism of tissue regeneration with the help of piezoelectric effect will be discussed. Furthermore, all of the piezoelectric materials are not suitable for biomedical applications even if they have high piezoelectricity since other properties such as biocompatibility are vital. Seen in this light, the proper piezoelectric materials which are approved for biomedical applications are mentioned. Totally, the present review introduces the recent materials and technologies that have been used for tissue engineering besides the role of electric fields in living tissues.

Hydroxyapatite-carbon nanotubes (HA-CNTs) nanocomposite coating was applied by electrophoretic method on anodized Ti alloy to investigate its stability in simulated body fluid (SBF). The biocoating was characterized by using scanning electron microscope (SEM) for microstructure, X-ray diffraction (XRD) for crystallography. The effect of CNTs concentration on the coating properties was also investigated and found out that CNTs up to 5% has various improving effect on the system. It increased corrosion resistance and adhesion of the coating to the substrate and decreased the number of cracks on the coating. The results of the in vitro test showed that the cell viability increased with increasing the concentration of CNTs to 3 wt.% CNTs.

In vivo cell tracking after transplantation in regenerative medicine remains an unmet challenge and limits current understanding of the wound healing mechanism through cell-based therapies. This study investigated tracking of human Wharton’s jelly stem cells (hWJSCs) seeded onto an acellular dermal matrix (ADM) and labeled with superparamagnetic iron oxide nanoparticles (SPIONs) by magnetic resonance imaging (MRI) in burn injury. The hWJSCs were characterized and assessed for growth kinetics. A total of 30 rats were enrolled in three equal groups. Group 1 underwent scald burn injury left without treatment, the group 2 was treated by an ADM that was prepared from cosmetic surgery skin samples and the group 3 received hWJSCs labeled with SPIONs seeded onto an ADM. Tensile strength was evaluated before and after interventions, real time PCR assessed apoptosis, and Prussian blue staining, scanning electron microscopy (SEM) and MRI were used for the tracking of labeled cells. The hWJSCs exhibited mesenchymal stem cell properties. Population doubling time was 40.1 hours. SPIONs did not show any toxic effect. The hWJSCs seeded onto an ADM decreased Bax and increased Bcl-2 gene expression. Internalization of SPIONs within hWJSCs was confirmed by Prussian blue staining, SEM and MRI until day 21. There was a significant difference between the Young’s moduli of normal skin and the group receiving hWJSCs seeded onto an ADM. Histological observations and SEM imaging confirmed that MRI is an accurate method to track SPION-labeled hWJSCs in vivo. This study showed that SPION labeling coupled with MRI can be used to further understand the fate of stem cells after transplantation in a burn model.