Degradation Mechanism and Control of Silk Fibroin

Abstract

Controlling the degradation process of silk is an important and interesting subject in biomaterials field. In the present study, silk fibroin films with different secondary conformations and nanostructures were used to study the degradation behavior. Silk fibroin films with highest β-sheet content achieved highest degradation rate, different from the previous studies. A new degradation mechanism revealed that degradation behavior of silk fibroin was related to not only crystal content, but also hydrophilic interaction and crystal-noncrystal alternant nanostructures. The hydrophilic blocks of silk were firstly degraded. Then, the hydrophobic crystal blocks which were formerly surrounded and immobilized by hudrophilic blocks, became free particles and moved into solution. Based on the mechanism, which enables the process more controllable and flexible, controlling the degradation behavior of silk fibroin without sacrificing other performances such as mechanical or hydrophilic properties become feasible, and this would greatly expand the applications of silk as a biomedical material.

Toward Biodegradable Mg–Air Bioelectric Batteries Composed of Silk Fibroin–Polypyrrole Film

“…[38] With the increased incubation time, the intensity of the amide I shoulder at 1630 cm -1 increased, indicating an enhancement in the degree of crystallinity. [39] After 10 days incubation, an interesting feature was observed that the film substrate showed a combined pattern of PPy and silk. This can be attributed to the degradation of silk substrate resulting in the exposure of PPy layer.…”

Biocompatible silk fibroin scaffold prepared by reactive inkjet printing

“…Silk is a versatile, natural material favoured for its mechanical strength, excellent biocompatibility, adaptable biodegradability [1,2], easy processing [3] and flexible structural modification [4]. Silk has a long history of use [5]; recently, regenerated silk fibroin (RSF) has been used as a building block for the fabrication of biomedical devices [3].…”

“…By increasing the b-sheet content using approaches such as controlled drying and alcohol immersion, the mechanical properties of RSF films can be improved. Similarly, the degradation rate of RSF can be controlled by varying the processing route [1,2]. For instance, water-annealed films are more flexible and have a faster degradation rate than that of methanol treated films [1].…”

“…Non-printed cast RSF films (NP) and cast films submerged in methanol for 4 days (NP?M) to induce bsheet formation were used as controls to monitor the transformation of the printed films. FTIR spectra were taken of the amide I region (1705-1595 cm -1 ), which is most commonly used to determine the secondary structure of proteins as this region has less convolution of peaks than other areas of the spectra [2,20]. Films untreated with methanol had a peak at 1638 cm -1 , associated with random coils; however, with the increasing volumes of methanol, this peak shifts to 1620 cm -1 which is indicative of b-sheets [21], and in (Fig.…”

“…3c. As discussed earlier, the ability to selectively induce regions of different crystallinity could be used to control degradation rate, since the degradation of RSF structures is related to their b-sheet content [1,2]. Inkjet printing offers greater flexibility in controlling the crystallinity of the RSF structure due to its selectively patterning nature.…”