The Effect of Freeze Drying on the Deoxyribonucleic Acid Chain of Human Sperm

As a new method for preservating human spermatozoa, freeze drying has many special advantages. However, the freeze drying process could damage the the DNA of the human spermatozoa, the injury will also be caused by the endoenzyme of the spermatozoa. So far, the commonly used freeze drying protective agents-ETBS (ethylenedioxy-diethylene- dinitrilo-tetraacetic acid (EDTA) or ethylene glycol-bis-(2- aminoethyl)-N,N,N´, N´-tetraacetic acid (EGTA) was added to the Tris-HCl buffer) has been proved to restrain the enzyme activation in sperm and protect the genetic material. Many studies showed that yolk and trehalose can supply special protection for the sperm in the freeze drying process. In this study, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) and single cell gel electrophoresis (SCGE) were used to detect the sperm DNA damage after freeze drying with ETBS, ETBS added with trehalose or added with both trehalose and yolk as protective agents.