Fluorescent cacao oil: A material suited for highlighting blood vessel in macro-scale dissection.

This study describes a novel method to highlight vascular networks in animal tissue during macro-scale dissection using cacao oil and ultraviolet (UV) fluorescent dye. This is a three-step method: 1) injecting warmed cacao oil containing oil-based UV fluorescent dye ("fluorescent cacao oil" or FCO) into the blood vessels of a dead animal; 2) lowering the temperature to solidify the FCO in blood vessels; and 3) illuminating blood vessels with UV light when the specimen is dissected. This method uses the unique properties of cacao oil, which is solid at room temperature but becomes liquid at 40°C. Such a relatively low melting temperature meets two conflicting demands, i.e., maintaining low viscosity for better flow into the blood vessels and preventing damage of animal tissue by heat. This method is:•Practical, as blood vessel is strongly highlighted using handy UV light during dissection; therefore, a specific medical equipment is not required•Inexpensive, as FCO is made by mixing two commercially available produces (cacao oil and UV fluorescent dye)•Stable, as FCO-injected tissue can be fixed and preserved semi-permanently in formalin. The fluorescent ability of FCO is not affected by this process.