“…[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.…”