An oocyte vitrification carrier is the device that holds the oocyte or embryo in an ultra-thin film of cryoprotectant solution whilst it is plunged into liquid nitrogen during vitrification. The geometry of the carrier directly determines the cooling rate, the volume of cryoprotectant surrounding the cell, and whether the system is open (cell contacts liquid nitrogen directly) or closed (cell is sealed before liquid nitrogen contact).
The carrier is not interchangeable between vitrification kit manufacturers. The cryoprotectant concentrations, equilibration times, and warming protocol are all calibrated to the specific carrier geometry and material properties of the kit they are supplied with. Using a carrier from one manufacturer with a warming protocol from another is a common source of unexplained poor survival rates in labs that have recently changed kit supplier.
What is the difference between an open and a closed oocyte vitrification carrier?
An open carrier suspends the oocyte or embryo in direct contact with liquid nitrogen during cooling, achieving the highest possible cooling rate. A closed carrier seals the sample within a straw before liquid nitrogen contact, providing containment integrity and eliminating direct contact between the cell and the nitrogen.
CBS High Security Vitrification Kits (cryolab.co.uk/product-category/vitrification-kits/) use a closed carrier design that is compatible with standard UK IVF laboratory practice and consistent with current HFEA guidance on containment.
The carrier you choose commits you to a specific warming protocol. Embryologists who have changed vitrification kit suppliers and attempted to use the old warming protocol with a new carrier system have encountered survival rates that do not reflect the kit’s validated performance. The protocol is inseparable from the carrier – always use the warming protocol supplied with the kit you are using.
Can oocyte vitrification carriers be reused?
No. Vitrification carriers are single-use devices. Reuse carries cross-contamination risk and does not comply with HFEA traceability requirements. Each carrier should be labelled with patient identifiers as part of the witnessing and traceability process required under HFEA standards, in line with the clinic’s standard operating procedures.
