Prosthetic Tissue Valve Freeze-Drying Protocol
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Solution Overview
Problem
Conventional prosthetic tissue valves face issues with short-term preservation, calcification, thrombus formation, and high costs due to the need for invasive surgeries and anticoagulant treatments, with existing drying methods causing thermal stress and residual water issues that affect long-term preservation and biocompatibility.
Innovation Solution
A method involving controlled temperature and cooling rate protocols for prosthetic tissue valves, including a critical crystallization temperature and rapid cooling to ensure uniform crystallization, followed by vacuum freeze-drying and the use of heparin and growth factors to enhance anticoagulant and endothelialization properties, while minimizing lyoprotectant concentration to improve biocompatibility and reduce residual water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional lyophilization method is used with uniform freezing, then the prosthetic tissue valve can be preserved in dry state, but thermal stress damages the biological tissue during freezing
Solution Approach 1:
The freezing process is divided into multiple stages with different cooling rates. First stage: rapid cooling at -80°C to form small ice crystals. Second stage: controlled cooling at -20°C to -40°C to complete crystallization. This segmented approach prevents thermal stress while achieving uniform preservation.
Solution Approach 2:
The cooling rate parameter is changed during the freezing process. Initial rapid cooling (first cooling rate) is followed by slower cooling (second cooling rate). This parameter change allows formation of fine crystals without thermal stress damage, enabling long-term preservation.
2Productivity
If rapid freezing is applied to the entire prosthetic tissue valve, then crystallization is accelerated, but large sized crystals damage the internal structure
Solution Approach 1:
The freezing process is divided into two sequential stages: first stage with rapid cooling at -80°C for 1-3 hours to initiate crystallization, second stage with slower cooling at -20°C to -40°C for 3-6 hours to complete the process. This segmentation produces uniform fine crystals that preserve internal structure while achieving rapid overall crystallization.
3Reliability
If the prosthetic tissue valve is stored in preservation solution, then it maintains functionality, but long distance transportation is inconvenient and repeated washing is required
Solution Approach 1:
The prosthetic tissue valve is transformed from liquid-preserved state to solid-frozen state, then to vapor-removed state through sublimation. The final dry frozen state allows convenient transportation without liquid solution, while the valve can be rehydrated before use to restore full functionality.
Solution Approach 2:
The liquid preservation solution is replaced by solid frozen state preservation. This substitution eliminates the need for liquid handling during transportation, providing mechanical convenience while maintaining preservation effectiveness through the frozen state.
4Reliability
If high concentration of lyoprotectant is used to prevent damage during freezing, then preservation is improved, but toxicity damages the biological tissue
Solution Approach 1:
The concentration parameter of lyoprotectant is optimized to a specific range (5-20% w/v) rather than using high concentrations. Combined with controlled freezing parameters (-80°C initial stage), this parameter change provides adequate protection against freezing damage while minimizing toxicity to biological tissue.
5Duration of action of stationary object
If the prosthetic tissue valve is dried excessively during lyophilization, then preservation in dry state is achieved, but biological functions are reduced
Solution Approach 1:
The drying temperature parameter is controlled within -20°C to -40°C range, and drying time is limited to 12-48 hours. These parameter changes achieve sufficient dry state preservation while preventing excessive drying that would reduce biological functions. The frozen state is maintained throughout to protect biological integrity.
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
The method allows for a prosthetic tissue valve that is flexible, anticoagulant, and anti-thrombotic, with improved biocompatibility and long-term preservation, reducing manufacturing and transportation costs and simplifying application procedures, while maintaining high biological functions in a dry state.
Implementation Method 1
decreasing a temperature of a chamber carrying the prosthetic tissue valve from a first preset temperature to a second preset temperature in a first cooling rate; decreasing the temperature of the chamber carrying the prosthetic tissue valve from the second preset temperature to a third preset temperature in a second cooling rate
Implementation Method 2
the second preset temperature is greater than a crystallization temperature of the prosthetic tissue valve, and the second preset temperature is a critical crystallization temperature. The third preset temperature is lower than the crystallization temperature of the prosthetic tissue valve
Implementation Method 3
performing a drying process to the prosthetic tissue valve
Data Source
AI summary
A prosthetic tissue valve and a method of treating the prosthetic tissue valve are provided. The method includes: decreasing a temperature of a chamber carrying the prosthetic tissue valve from a first preset temperature to a second preset temperature in a first cooling rate; decreasing the temperature of the chamber carrying the prosthetic tissue valve from the second preset temperature to a third preset temperature in a second cooling rate; and performing a drying process to the prosthetic tissue valve. The second preset temperature is a critical crystallization temperature and is greater than a crystallization temperature of the prosthetic tissue valve. The third preset temperature is lower than the crystallization temperature of the prosthetic tissue valve, and the second cooling rate is greater than the first cooling rate.