Date Published: March 12, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Jung Woo Leem, Jongwoo Park, Seong‐Wan Kim, Seong‐Ryul Kim, Seung Ho Choi, Kwang‐Ho Choi, Young L. Kim.
Fluorescent proteins often result in phototoxicity and cytotoxicity, in particular because some red fluorescent proteins produce and release reactive oxygen species (ROS). The photogeneration of ROS is considered as a detrimental side effect in cellular imaging or is proactively utilized for ablating cancerous tissue. As ancient textiles or biomaterials, silk produced by silkworms can directly be used as fabrics or be processed into materials and structures to host other functional nanomaterials. It is reported that transgenic fusion of far‐red fluorescent protein (mKate2) with silk provides a photosensitizer hybridization platform for photoinducible control of ROS. Taking advantage of green (visible) light activation, native and regenerated mKate2 silk can produce and release superoxide and singlet oxygen, in a comparable manner of visible light‐driven plasmonic photocatalysis. Thus, the genetic expression of mKate2 in silk offers immediately exploitable and scalable photocatalyst‐like biomaterials. It is further envisioned that mKate2 silk can potentially rule out hazardous concerns associated with foreign semiconductor photocatalytic nanomaterials.
Removal of Sericin in Silk (i.e., Degumming): For effective generation and release of ROS from mKate2 silk, it was critical to remove the outermost layer (i.e., sericin) of silk fibers. Sericin was removed using a degumming process. The outer sericin layer is commonly removed to improve the color, sheen, and texture of silk in the silk textile industry. However, conventional sericin removal methods are inappropriate for mKate2 silk, because these involve a boiling process in an aqueous solution.[[qv: 13c–e]] In this case, mKate2 silk cocoons were soaked in a prewarmed mixture solution of sodium carbonate (Na2CO3, 0.2%) and Triton X100 (0.1%) at low temperature of <60 °C under a vacuum pressure. During the degumming process, low pressure treatments (620 mmHg) were repeated several times to uniformly infiltrate the solution between silk fibers to remove most sericin. The degummed mKate2 silk cocoons were dried in dark under the ambient air conditions. The authors declare no conflict of interest. Source: http://doi.org/10.1002/advs.201700863