Table 1 Comparison of the studies for human spermatozoa conventional freezing and vitrification

Saritha and Bongso [21]

57 human semen samples^a

Glycerol used. RT 10 min, cryotube 0.85 mL, LN₂ vapor, 15 + 15 min. Thawed RT 30–45 min.

Glycerol used. RT 10 min. Cryotube 0.85 mL. Plunged into LN₂. Warmed RT 30–45 min.

No motility difference was found between two methods.

Nawroth et al. [22]

30 human semen samples. Native or swim-up.

Glycerol used. 0.25 mL straw, RT 10 min. 22 °C to 4 °C by − 5 °C/min; 4 °C to − 30 °C by − 10 °C/min; − 30 °C to − 140 °C by − 20 °C/min. Thawed in 37 °C water bath 50 s.

With or without permeable cryoprotectant. Copper loop, 20 μl or 0.25 mL straw. Plunged into LN₂. Warmed in 37 °C medium 5–10 min.

Permeable cryoprotectant-free vitrification using copper loop resulted in higher motility with swim-up samples than conventional freezing. No difference in morphology.

Chang et al. [23]

30 healthy human semen samples

Freezing medium used. Biological freezer used. Thawing unspecified.

Freezing medium used. Plunged into LN₂. Warming unspecified.

No difference in motility or DNA fragmentation was found between two methods.

Vutyavanich et al. [24]

30 normospermic human semen samples

Freezing medium used. 0.25 mL straw, RT 10 min. 20 °C to 5 °C by − 1 °C/min; − 5 °C to − 85 °C by − 10 °C/min. Thawed in 25–28 °C tap water.

Glycerol used. 0.25 mL straw, 4 °C 10 min. Plunged into LN₂. Warmed in 25–28 °C tap water.

Vitrification gave superior motility and cryosurvival than conventional freezing. No difference in morphology or DNA integrity.

Moskovtsev et al. [25]

11 human semen samples. Washed.

Freezing medium used. LN₂ vapor. Thawing unspecified.

Permeable cryoprotectant free. Warming unspecified.

Vitrification resulted in higher motility and progressive motility.

Agha-Rahimi et al. [26]

30 normozoospermic samples. Washed.

Glycerol used. Cryotube, LN₂ vapor 30 min. Thawed in 37 °C water bath 10 min.

With or without glycerol. 30 μl drop, Plunged into LN₂. Warmed at 37 °C medium 5–10 s.

Both methods resulted in similar motility, viability, recovery rate and DNA fragmentatioin. No permeable cryoprotectant was required for vitrification.

Zhu et al. [27]

58 human semen samples. Washed.

Glycerol used. RT 5 min. LN₂ vapor 30 min. Cryogenic vial, 0.5 mL, LN2 vapor 30 min. Thawed in 37 °C water bath till melted.

Permeable cryoprotectant free. Cryogenic vial, 0.25 mL, RT 1 min. Plunged into LN₂. Warmed in 42 °C water bath 1 min, 37 °C water bath till melted.

Vitrification with optimal sucrose concentration resulted in higher progressive motility, plasma membrane and acrosome integrity than conventional freezing. No differences in motility or DNA stability.

Ali Mohamed [28]

33human semen samples

Freezing medium used. 0.25 mL straw, RT 10 min, LN₂ vapor 30 min. Thawed 37 °C water bath till melting.

permeable cryoprotectant free, 37 °C 5 min, 100 μl straw-in-straw, Plunged into LN₂. Warmed in 42 °C medium.

Both methods had similar motility, viability and mitochondrial membrane potential.

Slabbert et al. [20]

35 human semen samples. Washed.

Freezing medium used. RT 10 min. 0.5 mL straw, LN₂ vapor 15 min. Thawed in 23 °C 5 min.

permeable cryoprotectant free. 300 μl sample in 1.5 mL straw, RT 10 min. Plunged into LN₂. Warmed in 42 °C medium 20 s.

Vitrification had higher mitochondrial membrane potential and lower percentage of DNA fragmentation than conventional freezing. No differences in motility.

Tongdee et al. [29]

37 normal human semen samples. Washed.

Freezing medium used. RT 10 min, Cryovial, 0.5 mL, 25 °C to 5 °C by − 1 °C/min; 5 °C to - 85 °C by − 10 °C/min. Thawed RT 15–20 min.

Freezing medium used. RT 10 min, Cryovial, 0.25 mL, plunged into LN₂. Warmed RT 15–20 min.

Motility decreased more by vitrification. No difference in morphology or DNA intergrity between two methods.

Aizpurua et al. [30]

18 normozoospermic human semen samples.

Glycerol used, 1.8 mL tube, 4 °C 30 min, LN₂ vapor 30 min. Thawed RT 30 min.

permeable cryoprotectant free, 37 °C 5 min, 20 μl drop, Plunged into LN₂. Warmed at 37 °C 5 min.

vitrification had higher motility and normal morphology, and lower DNA fragmentation than conventional freezing.

Karthikeyan et al. [31]

20 severe oligoasthenozoospermia (SOA) and very SOA sample^b

Freezing medium used. 0.5 mL straw, − 85 °C in a deep freezer 1 h. Thawed at RT 10 min.

permeable cryoprotectant free. Cryologic with stripper. Warmed in 37 °C medium

Vitrification revealed higher motility vitality with very SOA samples than conventional freezeing.

Le et al. [32]

105 human semen samples. Washed and unwashed.

Glycerol used. Cryotube RT 10 min. LN₂ vapor 15 min. Thawed at 37 °C water bath 5 min.

Glycerol used. RT 10 min. 30 μl drop, plunged into LN₂. Warmed at 37 °C water bath 5 min.

Conventional freezing method resulted in higher motility, viability while vitrification resulted in higher normal morphology.

Pabon et al. [33]

47 human semen samples, Swim-up

Glycerol used. RT 10 min. 50 μl drop on dry ice, cryotube. Thawed RT 10 min, then 37 °C 10 min.

permeable cryoprotectant free. RT 3 min. Collector-grid, 5–10 μl drop, plunged to LN₂. Warmed in 44 °C medium 3 min.

Vitrification presented higher motility, viability and mitochondrial activity than conventional freezing.

Spis et al. [34]

1 epididymal and 1 testicular sperm samples

Glycerol used. 20 + 8 capillaries. LN₂ vapor 30 min. Thawed in 37 °C water bath 50 s.

permeable cryoprotectant free. 20 + 8 capillaries. Plunged into LN₂. Warmed in 37 °C medium 20 s

Vitrification had higher mitochondrial membrane potential and motility in both epididymal and testicular capillaries than conventional freezing^c.