Glycerol (25% w/w based on
the weight of the gelatin powder ¼ 250 mg/mL based on the gelatin
solution) (Merck, Germany) as plasticizer and glutaraldehyde (0.2%
w/w based on the weight of the gelatin powder ¼ 2 mg/mL based
on the gelatin solution) were added to gelatin solutions.