Regeneration of cartilage tissue is a difficult and lengthy process. An active fibrous substrate that mimics the random arrangement of fibres in the extracellular matrix (ECM) may be a promising strategy to aid the self-repair process. Fibrils form interconnected, three-dimensional network whose morphology promotes oxygen and nutrient delivery to cells. Tuning the surface topology and chemistry of the scaffolds affects cell functions such as attachment, proliferation etc.
Aim of our work was to obtain a nonwoven carbon fabric modified with iron layer to monitor the process of regeneration of cartilage or bone defects by MRI imaging.
A two-step thermal conversion process was used for the thermal treatment of polyacrylonitrile nonwoven substrate (PAN, Sigma-Aldrich). The first step was oxidation, the second step was low-temperature carbonization. The samples were modified using the DC magnetron sputtering system with metallic layers deposited in different time. The presence of the layer and its uniform distribution on the fibre surface were verified by SEM/EDS and MRI. T1 and T2 relaxation times were measured on Rock Core Analyzer (Magritek), they were obtained from distributions calculated by applying Inverse Laplace Transform. Effect of the layer on physicochemical properties; specific surface area, contact angle, surface free energy and porosity was evaluated. Biocompatibility test was performed by contacting cells with the scaffold after 3, 7 days using osteoblast and chondrocytes.
The thermal conversion of the polymer precursor results in 6% fibres shrinkage. The carbon fibres show a significant decrease in wettability compared to the polymer nonwoven. Magnetron sputtering leads to the formation of a metallic layer on the side of the nonwoven exposed to the source, which is heterogeneous in nature: mesopores are present on the surface. Their presence has a positive effect on cells viability and proliferation. Along with the evaporation time there is a smoothing of the fibres surface with a continuous layer. The longer the deposition time, the better cell morphology, which adheres to the fibres surface and spreads between them. Their wettability changes and is near 80o. The layer has a positive effect on texture of the material and physicochemical properties improving cellular response
The carbon non-woven substrates formed by thermal conversion of polymer precursor can be modified by magnetron sputtering. The metallic layer influences texture of the carbon fibres; the shorter the sputtering time the rougher the fibres surface increases improving the cellular response from osteoblasts and chondrocytes. The layer is external with thickness depending on the process conditions. The iron layer increases the effectiveness of MRI imaging.
The work was supported by the National Science Centre Poland (NCN): Project no UMO-2018/31/B/ST8/02418