Fluidic automation

How are automated fluidics transforming continuous glucose monitoring (CGM) sensor innovation?
TTP’s CGM test system has been designed to speed up development by providing core elements such as fluidic automation, sensor output measurement, and data management, while maintaining flexibility and allowing rapid customisation where needed.
Here we explore the use of automated fluidics to supply the system’s flow cell with test fluids, such as glucose in PBS, or more complex mixtures closer to interstitial fluid in an in-vivo environment.
For simplicity and accuracy, we use as set of premixed fluids, but dynamic mixing on-demand can also be used to generate concentration ramps to test the accuracy of rate of change measurements.
Guided by FDA 21CFR862.1355 reporting requirements for integrated Continuous Monitoring Systems, we chose 5 glucose concentration levels from 30 to 400mg/dL, with additional inputs to test interfering substances.
The system operates in a through-flow mode for fast concentration changes, and switches to recirculation mode for long term testing.
Temperature control is critical: deliberate changes can be used to measure performance shifts with temperature, and temperature is held constant when other factors are the focus. We used a dry block heater in our system: tubing and flow cells equilibrate with temperature-controlled aluminium blocks, providing an accessible and thermally stable system.
Sterilisation is needed as microbial growth in PBS/glucose solutions at 37⁰C could consume glucose and damage the sensor. We developed a steriliser using UV LEDs to deliver a typical 90% kill dose of 100J/m2 in a few seconds.
Oxygen monitoring and control functions can be added when investigating oxygen sensitivity, which can strongly influence the performance of glucose oxidase and fluorescence-based sensors.
Finally, our system is flexible: it can be reconfigured and expanded to accommodate additional test fluids and sensors, and adapted for other sensing modalities beyond electrochemical.