Toward Spinning Greener Advanced Silk Fibers by Feeding Silkworms with Nanomaterials

Abstract

Silk has been used in several biomedical applications, including tissue engineering, drug delivery systems, biomedical implants, and diagnostic medical devices, due to its attractive intrinsic properties such as biocompatibility, controllable biodegradability, and excellent mechanical properties. In recent years, several attempts have been made to produce silk fibers with improved properties and new functionalities by feeding silkworms with modified diets containing nanomaterials. Nanomaterials possess unique physical, chemical, and biological properties and when combined with silk can expand its applicability for biomedical applications. Feeding silkworms with modified diets containing nanomaterials is a greener method of producing functionalized silk fibers when compared to the alternative postfunctionalization methods that include multistep procedures and toxic chemicals. The main advantages of using this greener method are related to the reduced usage of resources such as water, energy, and additional chemicals to spin functional silk fibers, the maintenance of intrinsic silk properties, the stability of the added new functionalities, and the possibility of large-scale production. Feeding silkworms with different nanomaterials such as carbon-based nanomaterials, metal and metal oxide nanoparticles, and quantum dots has led to the production of silk fibers with improved properties (e.g., mechanical and thermal) and/or new functionalities (e.g., magnetical and luminescence). However, nanomaterials concentration, dimensions, and solubility were shown to influence their uptake by silkworms as well as silk fiber properties. Here, we review the literature that focuses on the feeding of silkworms with nanomaterials, highlighting the acquired new functionalities and improved properties of the obtained greener and more sustainable silk fibers.

Ag-Based Synergistic Antimicrobial Composites. A Critical Review

“…This low-cost and energy-efficient method is frequently presented as a green alternative route compared to conventional chemical and physical methods and is a subject of an increasing number of publications. One of the finest examples of the green synthesis is the production of metal nanoparticles containing composites by feeding silkworms modified diets: this strategy allows researchers to get functional fibers by impregnating leaves with nanomaterials or their precursors for in situ synthesis [ 80 ]. However, all bioinspired methods require longer synthesis time (several hours and even few days) and additional and careful purification step of synthesized material from impurities and by-products [ 81 ].…”

Synthesis and Processing of Nanomaterials Mediated by Living Organisms

“…[46,48] As NMs have been detected in degummed (devoid of sericin) silk, this indicates that, once in the SG,NMs actually interact with the fibroin core.Itiswidely accepted that NMs incorporated in silk by silkworm feeding do not alter the basic silk structure but its secondary conformation. [55] As the ahelix/random coil structures confer ductility and toughness to the silk, and b-sheets provide stiffness, [43] specific physicochemical interactions of NMs with fibroin (likely including electrostatic, p-p stacking, van der Waals and hydrogen bonding [48] )w ould change the ratio of secondary motifs, resulting in upgraded mechanical performance.Itseems that oxidized carbon-based NMs (GO,GQDs,CDs), [46,48,54] smallsize Ag NPs, [57] and hydroxyapatite NPs [65] lead to an increase in a-helix and random coil structures by hindering their conversion to b-sheets during fiber spinning.T his would explain the high ductility and improved toughness reported in most of these cases (Figure 3d). Theo pposite trend is observed for CNTs,w hich is coupled to the increase in bturns [52] responsible for the silk stiffening.H owever,l ittle or no changes in the secondary structure were observed when silkworms were fed large-size Ag NPs [58] or cellulose nanofibers.…”

Synthesis and Processing of Nanomaterials Mediated by Living Organisms

“…It is widely accepted that NMs incorporated in silk by silkworm feeding do not alter the basic silk structure but its secondary conformation [55] . As the α‐helix/random coil structures confer ductility and toughness to the silk, and β‐sheets provide stiffness, [43] specific physicochemical interactions of NMs with fibroin (likely including electrostatic, π–π stacking, van der Waals and hydrogen bonding [48] ) would change the ratio of secondary motifs, resulting in upgraded mechanical performance. It seems that oxidized carbon‐based NMs (GO, GQDs, CDs), [46, 48, 54] small‐size Ag NPs, [57] and hydroxyapatite NPs [65] lead to an increase in α‐helix and random coil structures by hindering their conversion to β‐sheets during fiber spinning.…”