Reinforced and Ultraviolet Resistant Silks from Silkworms Fed with Titanium Dioxide Nanoparticles

Abstract

As the perfect combination of strength and luster, silkworm silks have been widely used in many fields but still need improvements. This paper demonstrates an in vivo uptake of titanium dioxide (TiO 2 ) nanoparticles by silkworms, leading to the direct production of intrinsically modified silk. The nanoparticles can be easily incorporated into the silk gland of silkworm by using this method due to the interactions between TiO 2 and silk fibroin molecules. Infrared spectra indicate that TiO 2 nanoparticles confine the conformation transition of silk fibroin from random coil/α-helix to β-sheet. Results of synchrotron radiation wide-angle X-ray diffraction and small-angle X-ray scattering suggest that modified silks have lower crystallinity, higher mesophase content, and higher Herman's orientation functions of crystalline region and mesophase region than control group. The breaking strength and elongation at break of the modified silk can be improved up to 548 ± 33 MPa and 16.7 ± 0.8%, respectively, by adding 1% nanoanatase into the artificial diet. Moreover, the TiO 2 -1% modified silk shows well-improved ultraviolet resistant property as the breaking strength only decreased 15.9% after exposure to ultraviolet light for 3 h. The in vivo modification method for silkworm silk is a green, sustainable, and promising route for commercial production in the future.

Enhanced silk performance by enriching the silkworm diet with bordeaux mixture

“…Researchers [24] also reported the largest agglomeration of silk fibroin compounds with the highest concentration of Ca, and it was shown that the fibroin macromolecular chains form complex with Cu ions, leading to more crystalline beta-type (beta-sheets) planes on the structure of silk fiber thread [13]. Similar results were reported using TiO 2 nanoparticles [15]. High additive amount is likely to exceed the absorbing capacity of the silkworms, and the agglomeration of nanoparticles at a high concentration may make the interaction between the metals and the silk fibroin difficult.…”

“…High additive amount is likely to exceed the absorbing capacity of the silkworms, and the agglomeration of nanoparticles at a high concentration may make the interaction between the metals and the silk fibroin difficult. According to these authors [15], TiO 2 nanoparticles interacted with the protein molecules and restricted the movement of protein molecules during secretion, then it was difficult to increase the nucleation sites of crystallization for silk fibroin around TiO 2 nanoparticles. Figure 5 X-ray diffractograms of silk fiber thread produced in different conditions.…”

“…This mechanism suggests that higher concentrations of Cu in the diet increase the silk tensile strength through conformational changes. Similarly, TiO 2 nanoparticles in the artificial diet of the silkworms also led to direct production of intrinsically modified silk, increasing the strength and toughness of the silk [15].…”

Functionalization of Silk Fibroin Materials at Mesoscale

“…After the TiO 2 were incorporated into silk fibers, the breaking strength and elongation of TiO 2 modified silk fiber can be enhanced to 548 ± 33 MPa and 16.7 ± 0.8%, respectively. Moreover, the TiO 2 functionalized silk fibers display well Anti UV properties compared with neat silk fibers …”

Effect of polyamines on mechanical and structural properties of Bombyx mori silk

“…Previously many attempts have been made to increase the silk production by feeding the larvae with compounds like royal jelly, cowpea,, and Juvenile hormone analog, methoprene . In vivo uptake of titanium dioxide nano particles by silkworms lead to increase in the mechanical properties of silk fibroin . Dietary supplementation with threonine and valine showed effect on mechanical properties .…”