Formic acid

Bombyx mori cocoon was prepared for a SF solution based on the protocols described^{65 (link)}. In brief, Bombyx mori cocoon was degummed to remove sericin. The degummed silk was then dissolved in a 9.3 M LiBr (SAMCHUN Chemical, South Korea, L1106) solution and dialyzed against deionized (DI) water for 3 days. After dialysis, the SF/DI solution was freeze-dried and dissolved in 98% formic acid (JUNSEI Chemical Co, Japan, 25010-0350) at a concentration of 10% (w/v). SF scaffolds were then fabricated via electrospinning, which provides rapid and low-cost strategy to control the SF nanofiber alignment in a continuous manner. As a gain medium, rhodamine B (Sigma, St. Louis, MO, USA, 1001405226) was added to the SF solution. Concentration of the rhodamine B was 0.001 M, unless specified otherwise. The electrospinning system (NanoNC, South Korea, ESR200RD) consisted of a high-voltage power supply, syringe pump, metal nozzle, and rotating collection drum. The alignment of the SF nanofibers was achieved by controlling the rotational speed of the collection drum. The rotational speed of the drum was varied from 500 to 2,500 rpm. The SF solution was continuously fed to the tip of the charged metal nozzle via the syringe pump at a constant speed. An electric field of 1.2 ~ 2.0 kV/cm was applied between the nozzle and the collection drum.

Four types of Ag compounds were used: Silver acetate (C₂H₃O₂Ag; 99%), silver tetrafluoroborate (AgBF₄; 98%), silver nitrate (AgNO₃; >99.9%), and silver phosphate (Ag₃PO₄; 98%). Silver acetate, silver tetrafluoroborate, and silver phosphate were purchased from Sigma-Aldrich (St. Louis, MO, USA). Silver nitrate was purchased from Kojima Chemicals (Saitama, Japan). Formic acid (98%) was purchased from Junsei (Tokyo, Japan). Gelatin powder (type A from porcine skin) was purchased from Sigma-Aldrich (St. Louis, MO, USA). An aqueous solution of glutaraldehyde (50%) was purchased from Sigma-Aldrich (St. Louis, MO, USA). Glycine was purchased from Sigma-Aldrich (St. Louis, MO, USA). All chemicals were used without further purification.

Phenethyl alcohol (98%) and formic acid (99%) were purchased from Junsei (Tokyo, Japan) and Dae-Jung (Gyunggido, Korea), respectively. Novozym 435, Lipozyme RM IM, and Lipozyme TL IM were purchased from Novozymes (Bagsværd, Denmark), and Lipase PS Amano IM was purchased from Amano International Enzyme Co. (Nagoya, Japan). The following solvents were used in this study: acetonitrile (99.5%; Junsei), acetone (99.5%; Dae-Jung), tetrahydrofuran (THF, Dae-Jung), 1,2-dichloroethane (99%; Dae-Jung), toluene (99.5%; Junsei), cyclohexane (99.5%; Dae-Jung), n-hexane (96%; Junsei), heptane (98%; Dae-Jung), and isooctane (98%; Dae-Jung).