Storing self-contained gel capillary cassettes for POC medical diagnostics

For effective clinical uptake of the lab on a chip/point of care technology (LOC-POC), in addition to cost advantages LOC-POC devices should offer multiple patient screening panels for related diseases as well as cold-chain transportation and storage abilities. We recently described a device that performs polymerase chain reaction (PCR) to simultaneously screen raw clinical samples from up to 16 patients for multiple infectious agents (Manage et al., Lab Chip, 2013, 13, 2576-2584). This cassette contains glass capillaries with desiccated semi-solid acrylamide gels that include all the reagents except for the sample, with integrated quality control. Here we report the development of protocols to store assembled PCR cassettes at room temperature, 4 °C or -20 °C as well as at +40 °C. We show that our cassettes are stable, with no loss of activity for at least 3 months at RT and at least 7 months at 4 °C and -20 °C. However, the activity of desiccated cassettes degrades when stored for more than 2 weeks at 40 °C, insufficient time for post-manufacture delivery and use of cassette PCR. To address this, we have evaluated two stage storage protocols. PCR cassettes can initially be stored at 4 °C and -20 °C for prolonged periods of time and removed for shorter term storage at RT, retaining activity for at least a month, which would facilitate transport to remote areas for testing. Effective use of cassette PCR in high temperature regions of the world, for experimental purposes defined here as 40 °C, appears to be feasible only after a first stage storage in the cold, followed by no more than 1 week at 40 °C. This should allow sufficient time for delivery by the manufacturer to a central area well served by power and refrigeration, for later ambient temperature transport and use in under-resourced areas that lack refrigeration.