Bringing you the latest ideas, opinions and news from the RPA community.
Lyophilised or liquid?
by Feb 12, 2018
Olaf Piepenburg Dr Olaf Piepenburg, CSO, TwistDx
One of our key aims at TwistDx is to make the RPA workflow as simple as possible, eliminating the pipetting of multiple reagents and freeing the user to focus on their research. As a result, we now offer RPA kits in two formats – lyophilised pellets and a liquid – each with unique strengths, suitable for different applications and requirements.
Lyophilised – no expertise needed
RPA has a number of advantages over PCR. The isothermal technique dispenses with thermocycling instruments and offers rapid results within five to 20 minutes, making it ideally suited to point-of-care testing and experiments away from the laboratory. Freeze-drying the reagents into a lyophilised pellet format enables us to put RPA into the hands of non-experts; buffers and magnesium acetate are simply added to the pellet with the template mixture and the reaction starts. Rehydration is the key step, and applying a little heat to the reaction will benefit sensitivity. Results can even be obtained using body heat, and in West Africa – where access to heating technology is limited – an ambient temperature of 30 °C is sufficient to carry out plant pathogen testing using our technology. Lyophilising the material into dry pellets increases the stability at these temperatures, reducing the need for cold storage and encouraging use outside the lab, from veterinary diagnostics on the farm to mobile testing for infectious diseases.
“Liquid RPA kits can be used in both high and low volume experiments, allowing reactions to take place in miniaturised formats – nanolitres to microlitres – which remain challenging to PCR.”
Liquid – high throughput and low volumes
High throughput, lab-based applications in industry and academia are at the other end of the spectrum, and a lyophilised format would, in many cases, be entirely inappropriate. We therefore also provide RPA reagents in a wet, glycerol-stabilised format, which simplifies the production process by cutting out the freeze-drying step.However, the liquid versions of the kits need to be stored at a low temperature to keep them stable, something that would not be suitable for point-of-care testing in the field. Offering RPA in a liquid format also opens the door to applications that would simply not be feasible using a lyophilised pellet. Liquid RPA kits can be used in both high and low volume experiments, allowing reactions to take place in miniaturised formats – nanolitres to microlitres – which remain challenging to PCR. This format is equally advantageous for larger volume reactions from 500 µl to 1 ml. It takes a comparatively large amount of energy and time to heat 1 ml of liquid during PCR, whereas RPA has less intensive requirements, operating at a constant, lower temperature.
Two formats, multiple applications
Both the lyophilised and liquid formats function in the same manner, and we are excited to be witnessing the adoption of the technology across a broad range of sectors, from microfluidics to water hygiene to biodefence. There are dozens and dozens of assays that researchers have created and published in peer-reviewed journals; so many that I can no longer keep up with reading all the papers as I used to. Whatever your application, our customer service team is always on hand to talk through any questions and discuss the most suitable RPA format for your application. Please get in touch and we’ll be happy to help.