Example of current influenza point-of-care:
BD Veritor™ system1
Disadvantages of current design:
The advantage of our design:
Another benefit of our design is the involvement of subtyping test. None of the current commercial point-of-care kits is able to subtype the suspected samples, so subtyping mainly is handed over to analyzing laboratory, providing an efficient way for frontline staff, such as immigration department and Agriculture, Fisheries and Conservation Department.
Almost all respondents prioritize reliability (ie. sensitivity and specificity) in the first place, no matter from local or international surveys.
Our ultimate goal is that non-professional can also handle. For the sake of easy observation of the results, we utilized chromoprotein as the reporter so that no special reporter machine is needed.
Ordinary and typical diagnosis procedure always spend an entire day long. After the conversations with two medical experts, it is known that shorter the diagnosis time, quicker for patients to undergo medical treatment. Thus, we aim to shorter the detection time. Also, we have considered that heater/ heat plate is not common, or even unavailable in the suburb, remote districts or some developing countries. The reporter chromoprotein can still be expressed under room temperature, however, its disadvantage is that users need to wait more than an hour. But still, it provides convenience to people living in regions with limited resources.
According to the result in Hong Kong, they mostly accepted the additional price ranging from HKD41 to HKD60 for quick detection, in which we are confident the price of the kit will be much lower than it. However, the acceptable price range of our another target group, people in developing countries, such as Bangladesh, Vietnam is only 1 USD approximately. If we want to promote our kit as far as possible to the above-mentioned countries, which is suffering from the influence of influenza, we need to further cut down our cost.
According to the result of surveys in Hong Kong, size and ethic consideration got lesser votes, when we asked for the reasons behind, they agreed that smaller size of the product will be better, but the size should not have a high priority in the process of design. As for ethic consideration, despite fears were expressed by interviewees when we mentioned that E.coil is utilized during the productions of toehold switches, they felt more acceptable after full explanation on the whole flow of manufacture and further recommend us to add such kind of explanations inside the kit (ie, protocol) to allay users’ worries.
The protocol is divided into two parts: the introduction and procedure.
From the questionnaires of citizens, we found that 86% respondents don’t know what H and N stand for. We believe that only when people get more familiar with the knowledge of influenza, flu can be absolutely combated.
At the beginning, we proposed that saliva can be the source of sampling due to its easy accessibility. After interviewing with Prof Chan, he indicated that nasopharyngeal aspirate is the most common sampling source in diagnosis, but the assistance of nurse/ medical professional is needed. Besides, he suggested that throat swab is the possible sampling way in the condition that our kit is sensitive and specific enough.
Prior to detection, water is required to add to reactivate the cell-free system as the cell-free system is inactivated as freeze-dried. For the sake of easy operation, another plate with pre-inserted water is prepared. During detection, sample will be load into the plate with water first to stabilize the protein. After that, standardized amount is extracted (50ul is set) followed by the sample, what the detection kit needs is only the heater/heat plate which is able to heat up to 37 degree Celsius (°C), and wait for 3 to 4 hours, or alternatively, if unfortunately, no heater/heat plate is available, the chromoprotein can be expressed at the 25 Celsius (°C), but need to wait for more than an hour. At the end, no special equipment/machine is needed for result identification, instead, the result is clarified in a color change attributed to the presence of chromoprotein. Avian influenza pose more threats on human, for instance, H5N1, H7N9 rendered negative and far-reaching influences on both economy and public health system in Hong Kong before. Thus, specially, we will include the detections of H5N1, H7N9 inside the kit, just as what medical experts and health department had said, rapid confirmation of whether suffering influenza, especially avian influenza helps quicker start of medical treatment.
During use, samples are loaded into the wells of our bio-design (See "Design" below, each kit will only contain one of them), and the results are shown in the form of colour changes
Cotton wool is used for sample collection. Our ultimate goal would be the kit is sensitive enough in response to throat swab.
The freeze-drying system is required to be rehydrated prior to the use. For the sake of easier operation, another plate with similar appearance is prepared (different colour will be used for distinction). Detailed information has been described above.
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.
Design 1 (Paper-based)
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.
Design 2 (Test tube)
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.
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.
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).
Design 3 (Tablets package)
In response to the concern raised by Prof Chan, we designed another design and the appearance is tablet package alike. The UCCKE team helped us to 3D-printed the model (see our collaboration page). 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.
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.
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.
Prototype of detection kit applied in medical diagnosis
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.
Design 4 (Modification of tablets package)
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 PBS before transferring to the detector, the cell-free system and it can help stabilizing the RNA inside the samples.
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).