Several factors have to be considered like the chemical nature of the released ion (i.e., its oxidation state and complexation degree with the medium species) and dose.įor decades, the application of an external electric field has been studied and successfully used in clinical practice to stimulate bone healing. For this reason, the use of alloying elements which upon dissolution release non-cytotoxic ions is of utmost importance. However, metals typically suffer from corrosion in bodily fluids, leading to eventual ions release into the medium. In this framework, biocompatible metallic scaffolds offer two main advantages over ceramic and polymeric scaffolds: (i) their mechanical properties are more similar to those of the human bone and (ii) they are intrinsically conductive, which makes them interesting candidates for electrical stimulation. However, polymers also suffer from some drawbacks such as an exceedingly low elastic modulus and, in some cases, poor corrosion resistance. Polymers are also considered as potential biomaterials for scaffolds due to some of their characteristics like high ductility and easy processability. For example, an implantable bone scaffold should not be too stiff so as to limit the stress shielding effect and avoid bone resorption and scaffold loosening, but should offer enough mechanical support and long-term stability for any daily activity. However, their associated brittle behavior and the typically reported high stiffness may hamper their application in specific cases where a certain degree of elasticity is required. Īmong the non-bioresorbable scaffolds, ceramics are the most widely studied materials as they offer a combination of high fracture toughness with good biocompatibility. 3D porous scaffolds must be compliant with the following requirements to be used in bone tissue engineering: (i) open and interconnected pore network to allow cell nutrition, proliferation and migration for tissue vascularization and formation of new tissue, (ii) in vivo vascularization, (iii) biocompatibility and bioactivity/biodegradability (iv) similar mechanical properties to those of the replaced tissue (v) corrosion resistance and (vi) ease of fabrication. The use of three-dimensional (3D) porous scaffolds in bone tissue engineering has been introduced as a promising alternative to conventional treatment options (i.e., autografting, allografting and xenografting) to promote bone healing and regeneration of relatively large non-healing bone defects, as it offers some advantages over conventional treatments (i.e., avoidance of donor site morbidity, high supply availability or reduced immune rejection). The results suggest that palladium-coated polyurethane foams may be good candidates for osteoblast scaffolds and demonstrate that ES enhances osteoblast proliferation up to 14 days and upregulate expression genes related to extracellular matrix formation. Regarding osteoblast differentiation, ES seems to enhance the expression of early expressed genes. However, after 28 days in culture, cells without ES were filling the entire structure, while cells under ES appeared rounded and not well adhered, a sign of cell death onset.
In addition, cells grown in both conditions were well adhered, with a flat appearance and a typical actin cytoskeleton distribution. Cells grown on palladium-coated polyurethane foams under ES presented higher proliferation than cells grown on foams without ES for up to 14 days. In the present work we have used a palladium-coated polymeric scaffold, generated by electroless deposition, as a bipolar electrode to electrically stimulate human osteoblast-like Saos-2 cells.
Amongst all non-bioresorbable scaffolds, biocompatible metallic scaffolds are preferred over ceramic and polymeric scaffolds, as they can be used as electrodes with different electric field intensities (or voltages) for electric stimulation (ES). Three-dimensional porous scaffolds offer some advantages over conventional treatments for bone tissue engineering.
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