Characterization of Silk/Poly 3-Hydroxybutyrate-chitosan-multi-walled Carbon Nanotube Micro-nano Scaffold: A New Hybrid Scaffold for Tissue Engineering Applications

Background: Long-term healing tissue engineering scaffolds must hold its full mechanical strength at least for 12 weeks. Nano-micro scaffolds consist of electrospinning nanofi bers and textile microfi bers to support cell behavior and mechanical strength, respectively. Methods: The new nano-micro hybrid scaffold was fabricated by electrospinning poly 3-hydroxybutyrate-chitosan-multi-walled carbon nanotube (MWNT functionalized by COOH) solution on knitted silk in a random manner with different amounts of MWNT. The physical, mechanical, and biodegradation properties were assessed through scanning electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, water contact angle test, tensile strength test, and weight loss test. The scaffold without MWNT was chosen as control sample. Results: An increase in the amount of MWNT up to 1 wt% leads to better fi ber diameter distribution, more hydrophilicity, biodegradation rate, and higher tensile strength in comparison with other samples. The porosity percentage of all scaffolds is more than 80%. According to FTIR spectra, the nanofi brous coat on knitted silk did not have any effect on silk fi broin crystallinity structures, and according to tensile strength test, the coat had a signifi cant effect on tensile strength in comparison with pure knitted silk (P ≤ 0.05). The average fi ber diameter decreased due to an increase in electrical conductivity of the solution and fi ber stretch in electrical fi eld due to MWNTs. The scaffold containing 1 wt% MWNT was more hydrophilic due to the presence of many COOH groups of functionalized MWNT, thus an increase in the hydrolysis and degradation rate of this sample. Conclusions: High intrinsic tensile strength of MWNTs and improvement of nano-micro interface connection lead to an increase in tensile strength in scaffolds containing MWNT.