Day 2 of the XXVII International symposium on Bioelectrochemistry and Bioenergetics started with a plenary lecture from Kylie Vincent from the University of Oxford, who spoke about Electrochemical control over metalloprotein single crystals. This lecture focused on bridging the solid state and the solution phase with electrochemical structure and metalloenzymes.
Throughout the day, there were plenty of bio (inspired) sensor and diagnostic presentations, all relevant to the field that ZP are most passionate about- biosensors and medical diagnostic devices. A special mention from day 2 goes to keynote lecturer Johan Bobacka from Åbo Akademi University, Finland. Johan’s talk focused around the upcoming field Magneto Hydrodynamic Extraction (MHE) of Interstitial Fluid for Non-invasive Wearable Biosensing.
The lecture discussed the importance of non-invasive/minimally invasive biosensing. Experiments on porcine skin were reported as an ex vivo model (closest to human skin). This was done in order to test the method of extraction.
An extraction cell was developed, see figure 1, including a hydrogel that contained a certain concentration of glucose. A magnetic field was applied to this extraction cell using neodymium magnets and a current was applied in a direction perpendicular to the magnetic field, in order to extract fluid, shown in figure 2. A comparison was to compare how much glucose was extracted using this active technology versus passive diffusion in comparison to magneto hydrodynamic extraction.
Figure 1: Extraction Cell Set Up Figure 2: Magneto- Hydrodynamics on Porcine Skin
This non-invasive MHE biosensing was conducted on 5 volunteers who had fasted for 9 hours before and who were then given 5 grams of glucose. A good correlation was shown between the MHE signal and Capillary Blood Glucose (CBG), with time lags between MHE and CBG taken into consideration. It was found that MHE is 13x more efficient than reverse iontophoresis- another non-invasive biosensing method first commercialised by Cygnus in their glucose watch.
Despite there being a few more questions regarding how much volume you can extract using a magnet, if it is an implantable CGM, and the clearance for this method, the scientific community is becoming closer to figuring out the complex solution to wearable CGM using non- invasive technology such as MHE. Screen printed biosensors and different approaches to combining biosensors to skin and tackling that biosensor-skin interface is what Zimmer and Peacock strive to achieve along with the rest of the diabetes community.
Also discussed on the second day was Paper-based (bio)sensors as smart and sustainable point of-care devices, shown in figure 4. The development of these paper based sensors starts with wax printing, where the pattern is designed and printed. The next steps in the process is heating to modifying and then screen printing. The aim is to use a porous paper as a support to contain the required reagents, delivering a reagent free device and reducing ink management. Smart paper based biosensors are becoming more prevalent as scientific discoveries are made in this field. Using paper to detect an analyte on the surface e.g the detection of chloride, without a separation system is of increasing interest.
Figure 3: Paper based biosensors Figure 4: End of an informative and successful day