Team:UNOTT/Design3

Key Transport Device

The Key. coli design is optimised to facilitate safe transport, ease of use, and maximise cell viability when it is required for authentication. To store our E. coli, they will be freeze-dried in an anaerobic environment with a desiccating cryoprotectant and liquid nitrogen. Freeze-dried cells will be kept at -70°C until use in our “key”, where it will remain at room temperature. Our key streamlines the resuspension of freeze dried cells and drives cell growth and gene expression.

Our design was inspired by the Mix2vial® system, which we are utilising to keep freeze dried cells and LB medium separated in two containers in an anaerobic, sterile environment. When the need comes to reactivate the bacteria, they can be easily connected to release the LB medium by simply attaching the two containers into the middle piece.

The current design allows for revival at room temperature, however, since E. coli grows best at 37°C, future improvements will include a heating module surrounding the collection container at the base. The mechanism of this module is under discussion, but we favour the use of super cooled sodium acetate crystallisation, reducing the need for electricity in our key. This exothermic reaction will heat up the solution to the optimum temperature of approximately 30-35oC.

Our device is designed to activate a freeze dried pellet of competent cells already transformed with our unique plasmid. Upon activation, the LB broth contained in one sector activates these cells which can then be measured.

The device consists of the following parts:

  1. Top container: it is a hollow cylinder with a sealed top. It holds the LB medium and the bottom is sealed with an easily pierceable material, such as aluminium foil.

  2. Bottom container: it is a hollow cylinder with a sealed bottom. It holds the freeze-dried cells and the top is sealed with an easily pierceable material, such as aluminium foil.

  3. Middle piece: it works as a joint for the two containers and allows flow of medium from the top container to the bottom container. Inside this piece there are two cylinders, one pointing upwards and the other downwards, to pierce the aluminium seal once the containers are attached by screwing.

  4. Polystyrene Foam: designed to provide support to the parts inside the key set.

  5. Outer case: provides protection to the other parts.

Production

The production of the Key. coli transport device prototype is still being undertaken with the help of one of the 3D printing laboratory at the University of Nottingham.

In the finalised version of the key transports all parts, except the polystyrene foam, will be made of polypropylene. This will allow for sterilisation by autoclaving and, therefore, reuse.

Assembly and Activation

To assemble the device:

  1. Hold the middle piece with the top part up.

  2. Hold the medium container upside down and attach it to the middle piece, with two screwing movements.

  3. Hold the cells container with the seal facing upwards and attach it to the bottom of the middle piece with two screwing movements.

  4. Still in the same position, screw the cells container completely into the middle piece to destroy the seal.

  5. Now, screw the medium container completely to destroy the seal and allow liquid to flow into the cells container.

  6. Mix gently as desired.

  7. Place the assembled device, with the cells container down, in a fixed surface (or incubator) until measurements.

  8. Once assembled, the device should be held with the top part up and should not be turned upside down.