Production of bio-ink
Enzyme solutions were prepared using dry samples and certain buffers. 0.15 g of glucose oxidase (GOD) (15000 U / L) were dissolved in 50 ml TRIS buffer, pH 7.4 for glucose biosensor. 0.15 g of cholesterol oxidase (CHOD) (300 U / L) were dissolved in 50 ml potassium phosphate buffer, pH 6.8 for cholesterol biosensor. Using ethylene glycol the viscosity of both enzymes solutions was adjusted to 10 cP.