Oocyte cryopreservation
Cryopreservation of mature oocytes is a critical means for female fertility preservation. Despite clinical advances using vitrification preservation method, the high concentrations of toxic penetrating cryoprotectant agents (CPA, up to 4.3 M) and low throughput (only one every experiment) put forward a challenge. Here, we report a synergetic ice inhibition platform via PVA/Fe3O4/GO nanoparticles (PFG NPs), that achieves sharp ice morphology, ice recrystallization, and devitrification inhibition, thus reducing cryodamage both in cooling and warming stages. Oocyte cryopreservation experiment demonstrates the survival rate can attain 98.6% using 2.5 M penetrating CPA while ensuring the scalability (ten oocytes each cryopreservation procedure). In contrast, recovered oocytes via PFG platform show 85 gene variation compared with fresh oocytes, whereas tradition CPA (TCPA) formulation induces 1396 gene changes. Meanwhile, the PFG-cryopreservation oocytes maintain normal ability of fertilization, development, and birth of offspring. Overall design: A-fresh; B-cryopreservation-1 method; C- cryopreservation-2 method; method-1 is using the 15 % EG + 15 % DMSO + 0.5 M sucrose, and cryotop to freeze oocyte.  method-2 is using 17.5 % EG + 1 M trehalose + PVA/Fe3O4/GO nanoparticles and straw to cryopreserve oocyte.