Influence of enzyme immobilization and skin-sensor interface on non-invasive glucose determination from interstitial fluid obtained by magnetohydrodynamic extraction.

We integrated a magnetohydrodynamic fluid extractor with an amperometric glucose biosensor to develop a wearable device for non-invasive glucose monitoring. Reproducible fluid extraction through the skin and efficient transport of the extracted fluid to the biosensor surface are prerequisites for non-invasive glucose monitoring. We optimized the enzyme immobilization and the interface layer between the sensing device and the skin. The monitoring device was evaluated by extracting fluid through porcine skin followed by glucose detection at the biosensor. The biosensor featured a screen-printed layer of Prussian Blue that was coated with a layer containing glucose oxidase. Both physical entrapment of glucose oxidase in chitosan and tethering of glucose oxidase to electrospun nanofibers were evaluated. Binding of glucose oxidase to nanofibers under mild conditions provided a stable biosensor with analytical performance suitable for accurate detection of micromolar concentrations of glucose. Hydrogels of varying thickness (95-2000 µm) as well as a thin (30 µm) nanofibrous polycaprolactone mat were studied as an interface layer between the biosensor and the skin. The effect of mass transfer phenomena at the biosensor-skin interface on the analytical performance of the biosensor was evaluated. The sensing device detected glucose extracted through porcine skin with an apparent (overall) sensitivity of -0.8 mA/(M·cm2), compared to a sensitivity of -17 mA/(M·cm2) for measurement in solution. The amperometric response of the biosensor correlated with the glucose concentration in the fluid that had been extracted through porcine skin with the magnetohydrodynamic technique.

Adaptation to a dynamic visual perspective in laparoscopy through training in the cutting task.

BACKGROUND: Laparoscopic surgery demands of surgeons special skills acquired only through practice. Laparoscopic training systems traditionally have an optical system that, once positioned, remains fixed and cannot refresh the perspective unless the task is interrupted and the camera repositioned. During a surgery, the visual perspective changes constantly to relocate the surgical target. This difference is a limitation for any novice surgeon. This report proposes the use of a mechatronic system that allows the trainee to handle optics dynamically during training in the cutting task and thereby adapt to dynamic relocation of the surgical target. METHODS: The study was conducted in two phases. The first phase involved using fixed optics to cut a circle drawn on a piece of cloth. The second phase involved the same cutting task but with the visual perspective changed dynamically by the user via a mechatronic assistant. RESULTS: The data show that by adapting to dynamic optics, medical trainees can quickly and easily handle and locate the task with real-time changes in visual perspective and can also improve task quality. A significant statistical difference was found between the two methods performed (p < 0.0025). Variance analysis also was applied to the mean values of the scores achieved by both groups (p < 0.0001). CONCLUSIONS: A new laparoscopic training method has been developed. It applies real-time dynamic optics that trainees assist by means of a mechatronic device harnessed to their body. This new training tool allows resident trainees to adapt quickly to the work environment of dynamic optics and thus enter the surgical scenario more rapidly and confidently after mastering the visual-spatial aspect of the laparoscopic approach.