Electroactivity and biocompatibility of polypyrrole‐hyaluronic acid multi‐walled carbon nanotube composite

Abstract

Electroactivity of polypyrrole hyaluronic acid, electropolymerized in the presence of oxidized carbon nanotubes (PPyHA-CNT) was studied in situ by electrochemical atomic force microscopy (EC-AFM) in physiological electrolyte solution. In situ Raman spectroscopic and quartz crystal microbalance (QCM) studies were conducted on layers of the polymer grown on AT-cut 5 MHz quartz crystals. Human adipose stem cell (ASC) attachment and viability were studied by Live/Dead staining, and the proliferation was evaluated by WST-1 Cell proliferation assay for polypyrrole samples electropolymerized on titanium. According to cyclic voltammetry, the measured specific capacitance of the material on gold is roughly 20% of the reference polypyrrole dodecylbenzene sulfonate (PPyDBS). Electrochemical-QCM (EC-QCM) analysis of a 210-nm thick film reveals that the material is very soft G' approximately 100 kPa and swells upon reduction. EC-AFM of samples polymerized on microelectrodes show that there are areas of varying electroactivity, especially for samples without a hydrophopic backing PPyDBS layer. AFM line scans show typically 20-25% thickness change during electrochemical reduction. Raman spectroscopic analysis suggests that the material supports noticeable polaron conduction. Biocompatibility study of the PPyHA-CNT on titanium with adipose stem cells showed equal or better cell attachment, viability, and proliferation compared with the reference polylactide.

Carbon nanotube interaction with extracellular matrix proteins producing scaffolds for tissue engineering

“…52,[70][71][72] This kind of material can also be applied within hyaluronic acid hydrogels to enhance viscoelasticity of biopolymer hydrogels without changing their water-intake capacity. 46,67,73 Thus this novel hybrid hydrogel can be a suitable material to be used in drug delivery with controlled release, and in tissue engineering. 46 For an interesting review in which the authors discuss CNTs as carriers for in vitro and in vivo drug delivery in cancer therapy, see Liu et al 74 …”

Nanocomposite and Nanostructured Carbon-based Films as Growth Substrates for Bone Cells

“…Thus, carbon nanotubes could be utilized in hard tissue surgery, e.g., to reinforce artificial bone implants, particularly scaffolds for bone tissue engineering made of relatively soft synthetic or natural polymers. Carbon nanotubes have been used in combination with poly(carbonate) urethane (Khang et al, 2007(Khang et al, , 2008, biodegradable polymers such as polylactic acid (Supronowicz et al, 2002), propylene fumarate (Shi et al, 2006), poly(3-hydroxybutyrate) (Misra et al, 2010), a copolymer of polylactide-caprolactone (Lahiri et al, 2009) or a copolymer of polypyrrole-hyaluronic acid (Pelto et al, 2010). Also hydroxyapatite (HAp), i.e., a ceramic material widely used in bone tissue engineering, but known for its high brittleness, has been reinforced with carbon nanotubes (Balani et al, 2007;Hahn et al, 2009).…”

“…One of the mechanisms of the improved cell colonization was an increased adsorption of fibronectin, i.e., an important cell-adhesion mediating ECM protein, to these composites, which has been explained by creating a nanoscale surface roughness of the material by the addition of nanotubes, and also by an increased material surface hydrophilia due to the presence of the polymeric component (pure carbon nanotube surfaces were highly hydrophobic, Khang et al, 2007Khang et al, , 2008. Another important mechanism is the electroactivity of carbon nanotubes, i.e., their electrochemical activity, electrical charge and conductivity, which enable electrical stimulation of cells (Supronowicz et al, 2002;Zanello et al, 2006;Khang et al, 2008;Pelto et al, 2010). For example, osteoblasts cultured on nanocomposites consisting of polylactic acid and carbon nanotubes and exposed to electrical stimulation (current 10 μA, frequency 10 Hz), increased their proliferation activity, concentration of extracellular calcium and mRNA expression for collagen type I (Supronowicz et al, 2002).…”

Novel Polypyrrole-Coated Polylactide Scaffolds Enhance Adipose Stem Cell Proliferation and Early Osteogenic Differentiation

“…5 The surface roughness, hydrophilicity, and elasticity of PPys can be tailored by the choice of the dopants or surfactants used in their synthesis. 6,7 One of the most studied biopolymer dopants is chondroitin sulfate (CS), a naturally occurring ubiquitous glycosaminoglycan. 8,9 CS is found not only in the ECM, but was also discovered on the cell surfaces of most mammalian cells and reported to be involved in osteogenic processes, including development, maturation, remodeling, and repair.…”

“…7 The effect of PPy surfaces with or without electrical stimulation (ES) has been studied with various cell types, such as skeletal muscle cells, neurites, endothelial cells, fibroblasts, osteoblasts, and MSCs. [12][13][14][15][16][17] However, so far, the effects of PPy on osteogenic differentiation of human ASCs have not, to the best of our knowledge, been reported either with or without ES.…”