Application of conductive polymers, scaffolds and electrical stimulation for nerve tissue engineering

Abstract

Among the numerous attempts to integrate tissue engineering concepts into strategies to repair nearly all parts of the body, neuronal repair stands out. This is partially due to the complexity of the nervous anatomical system, its functioning and the inefficiency of conventional repair approaches, which are based on single components of either biomaterials or cells alone. Electrical stimulation has been shown to enhance the nerve regeneration process and this consequently makes the use of electrically conductive polymers very attractive for the construction of scaffolds for nerve tissue engineering. In this review, by taking into consideration the electrical properties of nerve cells and the effect of electrical stimulation on nerve cells, we discuss the most commonly utilized conductive polymers, polypyrrole (PPy) and polyaniline (PANI), along with their design and modifications, thus making them suitable scaffolds for nerve tissue engineering. Other electrospun, composite, conductive scaffolds, such as PANI/gelatin and PPy/poly(ε-caprolactone), with or without electrical stimulation, are also discussed. Different procedures of electrical stimulation which have been used in tissue engineering, with examples on their specific applications in tissue engineering, are also discussed.

Large enhancement in neurite outgrowth on a cell membrane-mimicking conducting polymer

“…7) also revealed similar conclusion because greater number of long neurites were presented. This increase is significantly greater than not only the values (20-60%) typically reported on hybrid and functionalized conducting organic materials 20,[27][28][29][30] but also the largest increase (90%) previously reported on polypyrrole 24 . We attribute this behaviour to the integrated stimulation of surface biochemical ligands and applied electrical pulses.…”

“…4e). This stimulation time was significantly longer than those reported from most previously conducted cell-based electrical stimulation experiments 20,24,[27][28][29][30] . In contrast, greater than 40% of the cells detached from unfunctionalized PEDOTs after only 1 day of electrical stimulation at an even lower voltage (20 mV).…”

“…Pioneering studies have demonstrated the efficiency of using ECPs for electrical interfacing with neural cells and tissues [18][19][20][21][22][23][24][25][26] .…”

Incorporation of Conductive Materials into Hydrogels for Tissue Engineering Applications

“…Since pi-electrons move freely, they can form electrical pathways of mobility charge carriers [54,55]. The usage of conducting polymers allows a hydrogel to provide electrical stimulation locally and enhance the physical properties of the hydrogel as a template to accurately control the extent and duration of external stimulation [56][57][58]. Conductive materials like, polypyrrole (PPy), polyaniline (PANi), polythiophene (PT), and poly (3, 4-ethylene dioxythiophene) (PEDOT), have been widely used in conductive hydrogels (Figure 3).…”

Controlled delivery for neuro-bionic devices

“…The most commonly studied OCPs for biomedical applications are polypyrrole (PPy) and the functionalised thiophene, Poly(3,4-ethylenedioxythiophene) (PEDOT) [58]. These OCPs have been studied in a wide range of cell types and are considered to be chemically stable and non-cytotoxic.…”