Ultrasonics induced variations in molecular structure and tensile properties of silk fibers in a chemical free environment

Abstract

Ultrasonics can be used as an alternative energy supply for a green silk wet processing and for enhancement of some chemical/physical properties of biopolymers. In this work, ultrasonically treated silk fabric were compared with that of untreated and were investigated for the changes in fiber conformation structure and subsequent tensile property. Experiments were conducted under different time duration in a chemical free environment. Fiber surface energy distribution and transformation of silk secondary structure were analyzed using Xray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrum (FITR). Results showed that subject to treatment time, a surface oxidation effect and a light transformation of random coil to β-sheet can be induced from ultrasonic irradiation. Tensile testing showed that under certain treatment time, ultrasonics can lead to silk fibers with a slightly increased strength and reduced extensibility, as a result of the transition of fiber secondary structure.

Ultrasound-assisted air-jet spinning of silk fibroin-soy protein nanofiber composite biomaterials

“…This trend was seen again for the peak at 28.78° (IS80-0), which decreased gradually and moved left to 26.10° (IS80-180). These examples together indicate that longer ultrasonic treatment times will cause the random coil structure in SPI/SF composite nanofibers to transform into a β -sheets conformation [12] , [30] , [31] , [32] , [33] . The resulting changes of peak position, peak strength, peak shape and the secondary structure contents all indicate that an extension of ultrasonic time enhance the hydrogen bond interactions between soy and silk fibroin proteins as well as causing an increase in the β -sheet crystal content.…”

“…This phenomenon was also noted by Wang et al . [12] in a study on the ultrasonic treatment of silk fibroin from 0 to 60 min. This indicated that the longer ultrasonic times enhance the hydrogen bond interactions between protein molecular chains.…”

“…Silk fibroin protein chains exist as aggregates and micelles in the silkworm's glandular, forming a β -sheet structure when the silkworm spits out, with a crystallinity of about 75% [12] , [13] . Previous studies [1] , [2] , [14] , [15] , [16] found that the molecular chain of silk fibroin consist of an H-chain and an L-chain as well as a P25 protein.…”

“… •SDG-7: Affordable, reliable, and sustainable access to modern energy for everyone. Target 7.1 China [12] The powdered microfibers and nano-fibers were obtained by ultrasonic treatment of acid aqueous solution of silk fibroin protein fibers. •The diameter of 5–10 μm for powdered microfibers and the diameter of 30–120 nm for nanofibers can be obtained by simple and efficient ultrasonic technology.…”

The Evaluation of the Biological Effects of Melanin by Using Silkworm as a Model Animal

“…Here, FTIR was used to identify silk proteins and evaluate their relative content by revealing the effects of melanin on their secondary structures. The peaks at 1630, 1665, and 1700 cm −1 were attributed to random coil, β-sheet, and β-turn [ 41 , 42 , 43 , 44 ]. The FTIR spectra shown in Figure 4 a showed that all the spectra corresponding to control and melanin silks have the same peaks.…”