**3.2 Closed supports**

#### **3.2.1 Cryotip**

CryoTip consists of a plastic straw with a thin part (250 *μm* inner diameter, 20 *μm* wall thickness and 3 cm length) connected to a thick part (2000 *μm* inner diameter and 150 *μm* wall thickness, 4.5 cm length) and equipped with a movable protective metal sleeve (Fig. 11) (Kuwayama, Vajta, Ieda & Kato, 2005).

Fig. 11. The CryoTip is a finely pulled straw designed for holding gametes or embryos

Embryos are loaded in approximately 1 *μl* solution into the narrow part of the CryoTips without any air bubbles by aspiration of medium. Subsequently, the straw is heat-sealed at both ends, the protective sleeve is pulled over the narrow part and the device is plunged into liquid nitrogen. The time required for loading, sealing, adjustment of the sleeve and plunging does not exceed 90 s. The use of the closed CryoTip system eliminates potential embryo's contamination during cryopreservation and storage without compromising survival and developmental rates in vitro and in vivo (Kuwayama, Vajta, Ieda & Kato, 2005).
