Abstract
Silk fibroin-derived polypeptides (FDPs) are polypeptides resulting from the enzymatic separation of the hydrophobic crystalline (Cp) and hydrophilic electronegative amorphous (Cs) components of silk fibroin (SF). The role of these polypeptides in promoting the nucleation of hydroxyapatite (HA) has been previously investigated, yet is still not fully understood. Here we study the potential of HA mineralization via FDPs incorporated at 1:10, 1:2 and 1:1 in a plastically compressed (PC) and dense collagen (DC) scaffold. Scaffolds were immersed in simulated body fluid (SBF) at physiological conditions (pH = 7.4, 37°C) to promote biomineralization. The effect of Cs and Cp to promote HA nucleation was investigated at different time points, and compared to pure DC scaffolds. Characterization of Cs and Cp fragments using Liquid Chromatography–Mass Spectrometry (LCMS) showed little difference in the amino acid composition of the FDPs. Results obtained in vitro using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM) X-Ray Diffraction (XRD) and mass analysis showed little difference between scaffolds that incorporated Cs, Cp, and DC hydrogels. These results demonstrated that silk FDPs incorporation are not yet suitable to promote HA nucleation in vivo without further refining the collagen-FDP system.
Highlights
Native bone tissue is composed of organic collagen fibrils and inorganic hydroxyapatite (HA) crystals arranged in a strict hierarchical structure
While the nucleation of HA crystals occurs within collagen fibrils, collagen itself does not take an active role in HA nucleation, and only a small amount of apatite will form after a long period of time [3,4]
The peak at 2θ = 45 ̊ was not as apparent as in other dense collagen (DC) and DC hydrogels containing Cs (DC-Cs) hydrogels. Both 1:10 DC-Cs and DC-Cp hydrogels showed that their incorporation led to HA nucleation, which can be explained by the fact that both Cs and Cp have similar amino acid compositions, as seen by the Liquid Chromatography–Mass Spectrometry (LCMS) results, and the fact that both Cs and Cp lead to the nucleation of HA, as confirmed by the X-Ray Diffraction (XRD) pattern from the particles were immersed in simulated body fluid (SBF)
Summary
Native bone tissue is composed of organic collagen fibrils and inorganic hydroxyapatite (HA) crystals arranged in a strict hierarchical structure. It is thought that the high concentration of glutamic acid (glu) in Cs [23] allows it to play a role similar to calcium-binding non-collagenous proteins (NCPs), which act as modulators for the nucleation and growth of HA nanocrystals [28,29,30] by attracting more Ca2+ ions, as well as providing more nucleation sites for HA crystals [31]. Plastic compression (PC) removes excess water and forms a dense collagen (DC) hydrogel, in which the collagen fibril density (CFD) increases from
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
