Electrospun Silk Fibroin/kappa-Carrageenan Hybrid Nanofibers with Enhanced Osteogenic Properties for Bone Regeneration Applications

Abstract

In this study, a novel nanofibrous hybrid scaffold based on silk fibroin (SF) and different weight ratios of kappa-carrageenan (k-CG) (1, 3, and 5 mg of k-CG in 1 mL of 12 wt% SF solution) was prepared using electrospinning and genipin (GP) as a crosslinker. The presence of k-CG in SF nanofibers was analyzed and confirmed using Fourier transform infrared spectroscopy (FTIR). In addition, X-ray diffraction (XRD) analysis confirmed that GP could cause SF conformation to shift from random coils or α-helices to β-sheets and thereby facilitate a more crystalline and stable structure. The ultimate tensile strength (UTS) and Young’s modulus of the SF mats were enhanced after crosslinking with GP from 3.91 ± 0.2 MPa to 8.50 ± 0.3 MPa and from 9.17 ± 0.3 MPa to 31.2 ± 1.2 MP, respectively. Notably, while the mean fiber diameter, wettability, and biodegradation rate of the SF nanofibers increased with increasing k-CG content, a decreasing effect was determined in terms of UTS and Young’s modulus. Additionally, better cell viability and proliferation were observed on hybrid scaffolds with the highest k-CG content. Osteogenic differentiation was determined from alkaline phosphatase (ALP) activity and Alizarin Red staining and expression of osteogenic marker genes. To this end, we noticed that k-CG enhanced ALP activity, calcium deposition, and expression of osteogenic genes on the hybrid scaffolds. Overall, hybridization of SF and k-CG can introduce a promising scaffold for bone regeneration; however, more biological evaluations are required.

Reinforcement of Calcium Phosphate Cement with Hybrid Silk Fibroin/Kappa-Carrageenan Nanofibers

“…k-CG can also induce the formation of a bone-like apatite layer in the body, as suggested by a previous report [ 28 ]. This coincides with the results of our study, where k-CG improved the bioactivity of SF and the osteogenic potential [ 26 ].…”

“…This can be due to the presence of k-CG in the fiber structure and the influential role of its sulfonate groups (-SO 3 H) in absorbing calcium ions from the environment and accelerating the process of hydroxyapatite formation [ 25 ]. In fact, -SO 3 H groups are suitable locations for germinating apatite crystals and encourage the precipitation of hydroxyapatite by forming a calcium sulfate complex [ 26 ].…”

“…The solution preparation and electrospinning parameters were based on our published protocol for hybrid SF/k-CG [ 26 ]. Briefly, a freeze-dried SF sponge was put in an 8:2 ( v / v ) HFIP/CHCl 3 solution and stirred for about 3 h to prepare a 12% ( w / v ) SF solution.…”

“…Additionally, these fibers exhibit superior mechanical properties, such as increased tensile strength and toughness, compared to other biological polymers such as gelatin and chitosan [ 25 ]. Recently, our group has successfully developed hybrid nanofibers based on SF and kappa-carrageenan (k-CG) via electrospinning [ 26 ]. k-CG has been used in drug delivery and tissue engineering due to its gelation properties, forming gels with proteins and drugs, as well as stimulating cell growth [ 27 ].…”

Carrageenan-Based Compounds as Wound Healing Materials

“…Thus, K-CG has been reported to have osteogenic potential because it induced the metabolic activity of pre-osteoblast cells [ 125 ]. Silk fibroin/K-CG electrospun nanofibers showed great osteogenic properties [ 126 ]. Furthermore, the use of a “bioactive composite scaffold with enhanced biomimetic mineralization” that also had silk fibroin “led to a bone-like apatite layer” deposit after 7 days [ 127 ].…”