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5. Dropper <br> | 5. Dropper <br> | ||
Dropper is used to transfer the sample which has already been loaded into the water. To aid easy manipulation, the dropper will be customized and it can transfer the 50ul of solution per single absorption. | Dropper is used to transfer the sample which has already been loaded into the water. To aid easy manipulation, the dropper will be customized and it can transfer the 50ul of solution per single absorption. | ||
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+ | <br><br> | ||
+ | <h3><b>Design</b></h3> | ||
+ | <b>Design 1 (Paper-based)</b><br> | ||
+ | At the beginning, our ultimate goal is to insert our toehold switches into the cell-free system and in a paper form, reversely, our supervisors, Prof KM Chan and Prof TF Chan thought that there is no big difference between paper-based/ solution-based actually, solution-based may be easier to achieve. This led to the second design, which is solution-based. | ||
+ | <br><br> | ||
+ | <b>Design 2 (Test tube)</b><br> | ||
+ | We then designed another prototype. The freeze-dried cell-free pellet is condensed on the bottom of the test tube. There is a water pack on the top (below the cap), and a ring of saw-tooth down below the water pack. When the user presses the cap, the water pack will burst because of the pressure exerted from both cap and saw-tooth, hydrating the freeze-dried cell-free pellet. Also, in order to reduce the effect, brought by light on the cell-free system, there is an opaque membrane outside the tube. Users can tear along the dotted line before use. There is a circle in the middle of the plane of saw-tooth and its size is able to allow the passage of a cotton wool used for sample collection, including nasal swab. | ||
+ | <br><br> | ||
+ | However, this design is criticized by Prof Chan as the pellet may be not condensed at the bottom of test tube during freeze-drying by reasons of improper transportation, etc. In view of this, we try to condense the cell-free solution at the bottom, for example, use a smaller tube rather than the 15ml tube so that it is easier to make the pellet condensed at the bottom. Also, the cell-free system will be freeze-dried and stored in the test tube prior to distribution to market. Thus, during shipping, low-temperature environment maintenance should be ensured, preventing them from melting and not dispersed around. | ||
+ | <br><br> | ||
+ | He also agreed to the advice of our supervisors that cell-free system in solution form will be more practical, and appreciated to the design of chromoprotein, allowing simpler detection process, nevertheless, he cast his doubt on the subtyping, another track other than medical diagnosis: since the cell-free system can only reveal the result in yes-or-no form, there is no big problem in the medical track since not many tubes will be consumed, however, when applied in subtyping path, it seems redundant and many tubes will be used at the same time in only one sample (for example, when we want to test a suspect from verifying whether it is H5N1 or H7N9, 4 tubes are needed in total). | ||
+ | <br><br> | ||
+ | <b>Design 3 (Tablets package)</b><br> | ||
+ | In response to the concern raised by Prof Chan, we designed another design and the appearance is tablet package alike. As the bottom is curve-like shape, even if the freeze-dried cell-free system melt and spread around, or cannot condense totally at the bottom, the curve-shape can help settle down the cell-free solution. During the use, tear off the firm firstly, and add a certain amount of water by dropper. After hydration, similar to previous design, add the sample by cotton wool. The procedures afterward (eg the verification) are equivalent to previous design. | ||
+ | <br><br> | ||
+ | Apart from smaller size when compared to the previous design, fewer materials are used, which is more environmental-friendly. For the medical track, as mentioned above in procedure section, there are 7 wells (with freeze-dried cell-free system) in one plate and every patient will only consume 1 plate. | ||
+ | <br><br> | ||
+ | For the sake of convenience, especially on-site mass-screening detection carried by immigration or agriculture department, a larger plate with more wells is prepared, allowing mass detection at the same time. | ||
+ | <br><br> | ||
+ | In spite of appreciation of tablet design by Prof Chan, he commented that RNA may degrade during sampling, also the amount of sample is not standardized, which may interfere with the result. Such concerns render further improvement on next design. | ||
+ | <br><br> | ||
+ | <b>Design 4 (Modification of tablets package)</b><br> | ||
+ | During the conversation with Prof. Sung, we inquired him the problems faced in the last prototype. He suggested adding the samples to small amount of ddH2O before transferring to the detector, the cell-free system and it can help stabilizing the RNA inside the samples. | ||
+ | <br><br> | ||
+ | Therefore, new distribution and allocation of wells inside the detection plate are changed: For medical track, each user/patient will consume 2 plates, one is the detector with freeze-dried cell-free system, another is only plate with water for sample stabilization; For subtyping, the plate is advanced by the referral from medical experts by adding more subtype detection. According to the latest information from the Centers for Disease Control and Prevention3 (lastly updated on 19 April 2017), there are 18 known HA subtypes and 11 known NA subtypes up to now and many different combinations of HA and NA proteins are possible. Thus, a plate with two rows, HA and NA with 31 wells in total (18 for HA, 11 for NA and 2 for controls, positive and negative). | ||
</body> | </body> |
Revision as of 18:18, 29 October 2017