Human Sperm Cryopreservation: Update on Techniques, Effect on DNA Integrity, and Implications for ART

Table 1

Approaches to cryopreserve limited number of spermatozoa.

Cryopreservation techniques	Authors	Principle	Main advantages	Main disadvantages
Empty zona pellucida	Borini et al. [69]	Storage of individual spermatozoa in animal or human empty zona pellucida.	Avoid waste of time in screening to locate motile sperm; cryoprotectants can be added and removed without loss of spermatozoa sequestered in the zona	Risk of biological contamination
	Cohen et al. [70]
	Walmsley et al. [71]
	Montag et al. [72]
	Hsieh et al. [73]
	Liu et al. [74]
	Levi-Setti et al. [75]
	Cesana et al. [76]
	Hassa et al. [77]
Microdroplets	Gil-Salom et al. [78]	Storage of droplets of sperm/cryoprotectants mixture on the surface of dry ice and directly plunged into liquid nitrogen	Avoid sperm loss through adherence to the vessel	Risk of cross-contamination; shape and size of dishes make difficult to handle and store in conventional freezers and liquid nitrogen tanks
	Sereni et al. [79]
	Quintans et al. [80]
	Bouamama et al. [81]
ICSI pipette	Gvakharia et al. [82]	Storage of spermatozoa in ICSI pipettes	Sterile, simple, and convenient system	Not practical for long-term storage; fragility of ICSI pipettes; risk of cross-contamination
	Sohn et al. [83]
Volvox globator spheres	Just et al. [84]	Storage of sperm into spheres of Volvox globator	Significant postthaw recovery of motile sperm	Exposure to genetic material from the algae; constant source of algae
Alginate beads	Herrler et al. [85]	Microencapsulation in alginate beads	Inert nature of alginate beads	Decrease sperm motility with encapsulation
Cryoloop	Nawroth et al. [86]	Individual spermatozoa deposited directly on cryoprotectant film covering the nylon loop and immersed in liquid nitrogen	Excellent vessel for vitrification; no additional preparation	Open system: risk of cross-contamination
	Schuster et al. [87]
	Isachenko et al. [42]
	Isachenko et al. [42]
	Desai et al. [88]
	Desai et al. [89]
Agarose microspheres	Isaev et al. [90]	Storage of sperm loaded in agarose microspheres	Nonbiological carrier	Clinical value of this approach not evaluated
Straws	Desai et al. [91]	Sperm/cryoprotectants loaded into the ministraw	Sterile, simple, and convenient system	Not ideal for severely impaired specimens; sperm loss due to adherence to the vessel
	Isachenko et al. [92]
	Koscinski et al. [93]