27 Incubators, Freezers and Cooling Equipment


Using the above method, the test was repeated with the larger 1.9mL Tri-Coded Tubes in a 48-position SBS rack. The only experimental differences were that the volume aspirated – in this case 2,073µl of Ringer’s solution to more closely match the correct working volume of this larger tube and the torque setting of 0.10 Nm for the larger tube and cap in use.


The total average weight change of all 48 x 1.9mL tubes was 0.006% (equal to 0.022mg) over two weeks, and then only increased to 0.06% (equal to 0.264mg) over three years.


Table 2: Results for 1.9mL 48-position rack. Time of weighing


Before Storage 2 Weeks 1 Month 3 Months 6 Months 1 Year


2 Years 3 Years


Average % change 100%


-0.01% 0.00% -0.04% -0.04% -0.04% -0.06% -0.07%


Figure 5: Variation between columns in the same sterile 48 -rack over one year.


For the 48 x e-Beam treated 3.8mL Tri-Coded Tubes, pre-capped, pre-racked the total average weight change of all 48 tubes was 0.0002% (equal to 0.0016mg) over one year.


Figure 6: Comparison of weight change at individual tube positions in a 48-position rack.


Again, there was no observed cracking, grazing, or other physical damage caused throughout the freezing period, nor by repeated freeze/thaw cycles over a one-year period.


Figure 3: Variation between columns in the same 48 rack of 1.9mL tubes over time.


Again, there was no observed cracking, grazing, or other physical damage caused throughout the freezing period, nor by repeated freeze/thaw cycles over a three-year period.


Figure 7: Schematic of the compression sealing design of an externally threaded tube with tolerances in millimetres.


Conclusions Figure 4: Comparing 1.9mL 48-position and 1.0mL 96-position Tri-Coded Tubes. Effect of electron beam treatment


In the second part of the experiment, attention was turned to polymer tubes which had been treated using a standard dose of 62 kGy of e-Beam radiation. Both 1.0mL and 3.8mL treated tubes were tested, the key difference being that these treated tubes are supplied already capped. The experimental method for both was thus modifi ed to include an initial step of decapping the racked tubes with the handheld single tube capper/decapper specifi ed above. There were only two data points for these tests: initial weight and residual weight after one year.


The aspirated volumes in this case were:


1mL tube = 1.085mL 4mL tube = 4.150mL The observed weight change after one year was as follows:


For the 96 x e-Beam treated 1.0mL Tri-Coded Tubes, pre-capped, pre-racked, the total average weight change of all 96 tubes was 0.006% (equal to 0.012mg) over one year.


After collection of three years of tube weight data for the 1.0mL and 1.9mL Azenta Tri- Coded Tubes, and annual data for the 3.8mL and 1.0mL Azenta e-Beam treated tubes, it suggests a similar trajectory and gives confi dence to state that these products are suitable for long-term storage applications. Azenta Tri-Coded Tubes have both the cap and the tube body manufactured from the same polymer. This reduces potential leakage caused by the differential coeffi cients of expansion that can be seen when two different polymers are used. By standardising on the same polymer for construction throughout, any expansion or contraction during freeze/thaw cycles is the same for both parts of the article and the possibility of any gap opening between seal and tube is minimised.


It is important to state here that accurate capping to the specifi ed torque values is necessary to avoid any irregular damage to the threads of both the tube and the screwcap, as well as guaranteeing a reproducible and leak-proof seal each time. The use of a double-start thread, which helps to prevent cross threading, and an ingenious compression seal design that also prevents over-tightening of the cap all contribute to the intrinsic integrity of the Azenta tube design and the very low losses seen over time as demonstrated above. The polymer used for these tubes is a polypropylene material with very low levels of extractables and leachables, to not contaminate the stored samples, especially those stored in solvent such as DMSO. Although free from DNA, DNA/RNA-ase, endotoxins, and pyrogens, the e-Beam process can also help to ensure sterility in the supplied product. Other treatment types such as gamma irradiation and ethylene oxide gas exposure can also be used to gain this benefi t.


It is encouraging to also note that freeze/thaw cycles do not seem to cause any unnecessary damage to this type of quality sample storage tube if handled in a careful and appropriate manner, thus making them ideal for biobanking and compound management applications that require multiple access of samples over their lifetime.


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