The silkworm Bombyx mori secretes two silk proteins: silk fibroin and silk sericin. These are secreted
in a non-sericin substance. Silk fibrin is known for its immune tolerance, and is notable for its historic
use in suturing. At first, silk sericin was considered an impurity that elicited harmful pro-inflammatory
cytokine production. However, it was recently discovered that silk sericin has numerous beneficial
biological activities as an antioxidant and a tyrosinase inhibitor. Tyrosinases catalyze the hydroxylation
of monophenol molecules in cells, turning them into ortho-quinones. Silk sericin chelates with copper
and prevents lipid peroxidation due to tyrosinase activity, which prevents keratinocyte apoptosis.
Antioxidant effects and inhibitory effects on tyrosinase were also recently discovered to be found in the non-protein layer of silkworms, which consists of carbohydrates, salt, wax, and flavonoid derivatives.
Recently, fibrin and sericin from silkworm was also shown to stimulate cell migration in mink lung epithelial
cells.The silk protein of a tropical tasar silkworm was found to inhibit UVB-induced apoptosis
in human keratinocytes by preventing the activation of caspase-3.
Anti-aging effects of silk sericin have been demonstrated in a within-patient untreated-controlled
study. A hydroxyproline assay showed no significant differences in hydroxyproline content, skin impedance,
and transepidermal water loss between sericin treated skin and control. Another study showed a
significant drop in impedance when silk fibrin and sericin was used at 5% concentrations.
Silk sericin is also being explored in wound healing applications. A silk sericin-releasing bioactive
wound dressing was developed and found on average to heal faster, in 12 days, compared to Bactigras
dressing, which healed in 14 days with significantly reduced pain.
