Influence of silk fibroin/sodium alginate coatings on the mineralization of silk fibroin fiber artificial ligament prototypes

The goal of the present work is to investigate the effects of varying coatings on in vitro mineralization of silk fibroin fiber artificial ligaments (SFALs). Silk fibroin (SF) and sodium alginate (SA) aqueous solutions with varying concentrations were respectively employed for coating surfaces of the SFALs to improve calcium phosphate (CaP) deposition. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Energy-dispersive X-ray spectroscopy were utilized for characterizations. Furthermore, the surface of the SFAL was modified with SF/SA composite coatings. The volume ratios of the SF to the SA were set at 2:8, 4:6, 5:5, 6:4 and 8:2. The results show that either the SF or the SA coatings can improve the mineralization of the SFALs in vitro. The concentration of 1% for the SF and the SA coatings is conducive to deposit more calcium ions and obtain a biomimetic Ca/P ratio. Furthermore, the SF/SA composite coatings facilitate a thicker and uniform deposition layer than the SF and the SA coatings. The sediments are spherical particles and are more uniform in size. Therefore, the SF/SA composite coatings have more significant efficacy, particularly when the volume ratio of the SF to the SA was 4:6. The present work indicates that the SF/SA coatings possess excellent potential in promoting the osseointegration of artificial ligaments implanted in bone tunnels.