Articular cartilage wear is one of the most common cartilage injuries resulting from a number of causes including disease, trauma, or physical injury. Articular cartilage regeneration is a slow healing process due to the inherent vascular nature. Tissue engineering is an innovative approach used to facilitate healing and regeneration process of a natural tissue. In this study, nanocomposite scaffolds based on polycaprolactone (PCL)-chitosan/multi-walled carbon nanotubes Functionalized with carboxyl groups (MWCNTs) were fabricated via electrospinning method containing 0, 0.5 and 1 wt. % of MWCNTs. Nano-micro scaffolds were also fabricated using electrospinning of the nanocomposite scaffolds on the functionalized silk fibroin as substrate and investigated in terms of surface morphology, chemical and crystalline structure, hydrophilicity, mechanical properties, bioactivity, biodegradability and cell behavior. Scanning electron microscope (SEM) showed that the scaffold containing 0.5 w.t % MWCNTs with an average fiber diameter of 99 ± 15 nm possesses the lowest average fiber diameter with a statistically significant difference compared to the scaffold without MWCNTs and the one containing 1wt.% MWCNTs, which can be due to the inherent extraordinary electrical conductivity of MWCNTs. The hydrophilicity of the scaffold containing 1wt. % of MWCNTs with water contact angle of 51.73 ± 5.42 was significantly higher than the scaffold without MWCNTs with contact angle of 67.93 ± 6.59, which can be due to the increase of hydrophilic carboxyl functional groups related to MWCNTs. The scaffold containing 0.5 wt. % MWCNTs with tensile strength of 33.81 ± 6.76 MPa presented the highest tensile strength with significant difference compared to the sample without MWCNTs and the sample containing 1wt. % of MWCNTs. According to the obtained results regarding morphological eva‎luation as well as hydrophilicity and mechanical properties, the scaffold containing 0.5 wt. % of MWCNTs was selected as the optimal sample, and other studies were performed on this scaffold and the control sample (the scaffold without MWCNTs. Based on the bioactivity eva‎luation, the presence of MWCNTs increased the crystallinity in the structure of the scaffold containing MWCNTs compared to the scaffold without MWCNTs. As for biodegradability assessments, the scaffold containing MWCNTs with total weight loss of 6.36% is more stable than the scaffold without MWCNTs with total weight loss of 10.22%. The scaffold containing MWCNTs increased cell behavior and the formation of extracellular matrix on the surface of the scaffold. Characterization of nano-micro scaffolds revealed that the presence of functionalized silk led to the formation of more uniform nanofibers on microfibers during the electrospinning process compared to pure silk and the previous method. Examining the cross section morphology of the scaffold showed a favorable connection at the interface. The presence of MWCNTs has significantly reduced the water contact angle from 79.72±2.7 to 68.92±5.63. Tensile strength of pure silk fibroin, functionalized silk, nano-micro scaffold without MWCNTs and nano-micro scaffold containing MWCNTs are 32/92±2/69, 30/66±2/06, 29/93±0/77 and 25/39±1/30 MPa respectively. The increase of chemical interactions between the two phases has improved the mechanical strength due to the presence of MWCNTs. The increase of carboxyl groups due to the presence of 0.5wt. % of MWCNTs caused a significant increase in cell adhesion, growth and proliferation of chondrocyte cells on nano-micro scaffold containing MWCNTs on the 7th day, which can be seen in cell morphological examination using electron microscope and colorimetry. According to the obtained results, the nano-micro scaffold based on PCL/ chitosan/ functionalized MWCNTs/functionalized silk can be a good candidate for additional studies in the field of cartilage tissue engineering.

مهدي احمديان، سعيد كرباسي

محمد رفيعي نيا، مهدي مهديخاني، رحمت الله عمادي