Application: Ruthenium is a photoinitiator that utilizes visible light photocrosslinking (400-450nm) to covalently crosslink free tyrosine and acryl groups. Ruthenium photoinitiator has been tested on collagen type I, gelatin, silk fibroin, methacrylated hyaluronic acid, methacrylated gelatin, methacrylated collagen type I and PEGDA. Ruthenium is water soluble and yields better cytocompatibility, and crosslinking efficiency. Ruthenium is red/yellow/orange in color and will change the color of your solutions, hydrogels, or printed constructs. The Ruthenium photoinitiator kit is non-sterile. Adding antibiotics to your cell culture system, or sterile filtering is recommended. To sterile filter, resuspend the entire volume of ruthenium and Sodium persulfate (separately) and filter through small 0.2 micron button filters (separately). Use the sterile photoinitiator within 2 weeks. Ruthenium photoinitiator kit is ideal for tissue engineering, cell culture, and bioprinting, where tuning the mechanical properties of the substrate is required. The kit provides enough photoinitiator for >200 mL of bioinks/hydrogels.