Self-assembling Mechanism Of Regenerated Silk Fibroin And Its Influence Factors

With exceptional mechanical properties, low costs, as well as goodbiocompatibility and biodegration, Silk has been widely used in biomedicalworld including tissue engineering, drug delivery, biosensor and etc. As themost primary part of silk, silk fibroin (SF), the special amino acid sequenceof which is the key factor for the excellent properties of silk, can self-assemble with its orderly arrangement of its unique hydrophobic amino acidside chains. Exploring the mechanism of silk fibroin self-assembly willbenefit a lot to understand the relationships between the structures andfunctions of silk based biomaterials. Regenerated silk fibroin (RSF) is anideal in vitro model system for elucidating the details of the silk spinningprocess in vivo and for understanding the nanoscale structure formation ofRSF-based biomaterials.In this work, RSF was prepared through the processes of come unglued, silksoluted and dialyzed. Self-assembly process of RSF with differentconcentrations was researched with AFM for surface topography and ATR-FTIR for second-structure analysis after different incubation time. Resultsshow that concentrations can impact the process of silk fibroin self-assembly.The transition time at lower concentrations is shorter than those at higherconcentrations. At relatively higher concentration, the surface topographyof RSF changed from disordered aggregates to nanoparticles, the self-assemble followed the nucleation-dependent aggregation mechanism, whileat relatively lower concentration, the surface topography of RSF tended tobe nanofibers which followed the Micelle-mediated nanofiber formationmechanism. Additionally, RSF at high concentration is more likely to form the gel.4Peptides (GAGAGS (GS6)、GAGAGY (GY6)、GAGAGVGY (GY8)、GAGAGSGAAS (GS10)) which construct the silk fibroin were synthesizedto explore the role of modular motifs playing in the self-assembly of SF.With the help of AFM, FT-IR, CD, SEM and etc., results were obtained andindicated that the transition time of the secondary structure and surfacetopography of these petides were: RSF <GS6<GS10<GY8<GY6, whichcame to the conclusion that the effects of the modula motifs on the β-sheetformation of SF self-assembly is GS6> GS10> GY8> GY6.These results provide further insight for the investigation of the mechanismof SF self-assembly and indicate a feasible direction into the peptidesequence design of silk-based biomaterials with targeted properties.