The Use of Cholesterol Inclusion Complexes Based on Randomly Methylated Beta-Cyclodextrins to Improve Human Sperm Cryotolerance

The cryoprotective properties of cholesterol inclusion complexes based on randomly methylated β-cyclodextrin (RAMEB) derivatives in relation to human sperm was studied. The interaction of various concentrations of RAMEB and cholesterol inclusion complexes based on RAMEB with sperm membranes was assessed. It was shown that the pronounced cytotoxicity of RAMEB against sperm is due to the interaction of cyclodextrins with lipid components of the membrane, in particular, cholesterol extraction. RAMEB complexes with cholesterol have significantly less pronounced cytotoxicity. A relationship has been established between the concentration of cholesterol in sperm membranes and the concentration of RAMEB complexes with cholesterol in the sample. It found that incubation of sperm before cryopreservation with 2 mg/mL of RAMEB complexes with cholesterol significantly increased survival (by 13.8%) and the proportion of progressively motile sperm (by 14.8%) after thawing. X-ray diffraction analysis showed that the presence of RAMEB and RAMEB complexes with cholesterol in the samples at the studied concentrations (2, 4, and 8 mg/mL) did not affect the average size of ice crystals formed in the sample during cryopreservation. The mechanism of cryoprotective effect of RAMEB complexes with cholesterol was proposed.