Pilot study in human healthy volunteers on the use of magnetohydrodynamics in needle-free continuous glucose monitoring

Figures

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  Figure 1. Experimental set up and scheme. (a) Top-view of the acrylic wells placed on the volunteer’s lower arm. (b) A side-view of the acrylic wells. (c) The volunteer’s arm was placed between two neodymium magnets separated by an aluminum support. ( d) A schematic presentation of the set-up and the MHD extraction. Two Ag/AgCl disk electrodes inside the well drive a current through the skin (J). A magnetic field with direction (B) orthogonal to the current is applied to create Lorentz force (F) pointing towards the skin surface. The scheme is not drawn to scale. Figure Credits: Artic Frame Studio https://www.arcticframe.com.

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  Figure 2. Glucose tolerance tests. ( a) Schematic presentation of the glucose tolerance test timeline (black dashed line). Volunteers entered the test after overnight fasting (9 h). 5 min MHD extractions were conducted with alternating current polarity. The red and blue bars indicate the direction of the applied electric current for each extraction. Capillary blood glucose measurements, represented by red blood drops and red dashed lines, were taken twice before sugar intake (green dashed line). 8 more capillary blood glucose readings were obtained after the glucose drink with 20 min intervals. The skin hydration and transepidermal water loss readings were recorded before and after the test. (b) Raw data from a representative experiment. These data are from the MHD cathode central well (grey diamonds), the control well (blue triangles), and reference blood glucose measurements (red circles). The first data point after warm-up is shown as a star. Error bars for the MHD and diffusion raw data are based on the standard error of the diffusion data recorded after the warm-up period. Error bars for the CBG concentrations are based on the standard error of our reference device. (c) All 10…

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  Figure 3. Correlation of glucose concentrations in extracted ISF and capillary blood samples. CEG showing 88 measurement pairs from 10 experiments. These data are shown after applying the basic least squares calibration algorithm. Percentages within each zone are as follows: Zone A: 84.0%, Zone B: 16.0%, Zones C-E: 0%. The corresponding MARD is 12.9%.

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  Figure 4. Effect of extraction on the skin. (a) Photographs of the skin MHD well sites before and after the glucose tolerance test that includes 30 extractions lasting 5 min. The extraction well outline was marked with a red makeup pen before the experiment. (b) ΔTEWL and (c) Δ skin water content for each well from all 10 experiments. Δ values were obtained by measuring the skin parameters before and after the experiment and by calculating the difference between these values (Δ = after – before). p values were obtained via t-test, with p ≤ 0.05 considered significant.