Human Oocyte Vitrification via Nitrogen Slush Exposure
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Solution Overview
Problem
Current methods for cryopreserving human oocytes result in low pregnancy and implantation rates due to poor viability of thawed oocytes, despite advancements in slow cooling protocols and vitrification techniques.
Innovation Solution
The method involves directly exposing human oocytes to slushed nitrogen (N2 slush) for vitrification, using a transfer instrument like an electron microscopy grid to facilitate rapid cooling and minimize ice crystal formation, and storing the vitrified oocytes until they are ready to be devitrified.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slow cooling methods are used for cryopreservation, then oocytes can be stored for future use, but pregnancy and implantation rates remain low due to poor viability of thawed oocytes
Solution Approach 1:
The invention changes the cooling parameters from slow cooling to rapid cooling by using nitrogen slush, which achieves much higher cooling rates. This parameter change transforms the freezing process into vitrification, eliminating ice crystal formation and significantly improving oocyte viability and subsequent pregnancy rates
Solution Approach 2:
The invention utilizes the phase transition of nitrogen from liquid to slush state to achieve rapid heat extraction. The nitrogen slush acts as a cryogenic medium that enables extremely fast cooling rates, transforming the oocytes into a vitrified state without ice crystal formation, thereby resolving the contradiction between storage capability and post-thaw viability
2Duration of action of stationary object
If conventional liquid nitrogen methods are used, then oocytes can be frozen and stored, but survival rate after thawing is poor and apoptosis increases
Solution Approach 1:
The invention introduces nitrogen slush as an intermediary medium between the oocytes and liquid nitrogen. This intermediary enables controlled rapid cooling by facilitating heat transfer at optimal rates, preventing both ice crystal formation and excessive thermal shock, thereby maintaining high survival rates while enabling long-term storage
Solution Approach 2:
The invention applies preliminary cooling action by using nitrogen slush before final liquid nitrogen storage. This preliminary rapid cooling phase vitrifies the oocytes, creating a stable glassy state that can be maintained during subsequent long-term storage in liquid nitrogen, ensuring high survival rates upon thawing
3Manufacturing precision
If faster cooling rates are achieved, then vitrification is improved, but the method complexity increases compared to conventional freezing
Solution Approach 1:
The invention employs pneumatic principles by using nitrogen gas that is cooled to slush state. The nitrogen slush can be generated and maintained using pressure control and gas flow management, providing a relatively simple system to achieve the required cooling rates for vitrification without complex equipment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases the survival rate of vitrified human oocytes and decreases apoptosis upon thawing, leading to improved clinical outcomes such as higher fertilization, cleavage, and pregnancy rates compared to conventional liquid nitrogen methods.
Implementation Method 1
placing the transfer instrument and the human oocytes directly into a slushed nitrogen (N2 slush), wherein the human oocytes are directly exposed to the N2 slush thereby undergoing vitrification
Implementation Method 2
Nitrogen slush was compared to liquid nitrogen for freezing oocytes on grids. Survival rates based on morphology, cleavage and blastocyst formation were higher for bovine oocytes frozen in liquid nitrogen compared to those frozen in nitrogen slush
Data Source
AI summary
Provided are methods for the vitrification of human oocytes, which comprises: (a) placing human oocytes on a transfer instrument; and (b) placing the transfer instrument and the human oocytes directly into a slushed nitrogen (N2 slush), wherein the human oocytes are directly exposed to the N2 slush thereby undergoing vitrification, and wherein the human oocytes are able to live for a period of time after the human oocytes are devitrified.