Discrete wavelength selection for the optical readout of a metamaterial biosensing system for glucose concentration estimation via a support vector regression model.

In this contribution, a method to select discrete wavelengths that allow an accurate estimation of the glucose concentration in a biosensing system based on metamaterials is presented. The sensing concept is adapted to the particular application of ophthalmic glucose sensing by covering the metamaterial with a glucose-sensitive hydrogel and the sensor readout is performed optically. Due to the fact that in a mobile context a spectrometer is not suitable, few discrete wavelengths must be selected to estimate the glucose concentration. The developed selection methods are based on nonlinear support vector regression (SVR) models. Two selection methods are compared and it is shown that wavelengths selected by a sequential forward feature selection algorithm achieves an estimation improvement. The presented method can be easily applied to different metamaterial layouts and hydrogel configurations.

Dynamic modeling of the hydrogel molecular filter in a metamaterial biosensing system for glucose concentration estimation.

We present a novel concept for ophthalmic glucose sensing using a biosensing system that consists of plasmonic dipole metamaterial covered by a layer of functionalized hydrogel. The metamaterial together with the hydrogel can be integrated into a contact lens. This optical sensor changes its properties such as reflectivity upon the ambient glucose concentration, which allows in situ measurements in the eye. The functionalization of the sensor with hydrogel allows for a glucose-specific detection, providing both selectivity and sensitivity. As a result of the presented work we derive a dynamic model of the hydrogel that can be used for further simulation studies.

Distribution of 3-hydroxybutyrate dehydrogenase in primary lobules of rat liver.

In an attempt to establish the functional organization of the hepatic parenchymal unit, we used histo- and microchemical procedures to assess metabolic liver cell heterogeneity at the level of the primary lobule. Because of the close interrelation of glucogenesis and ketone body formation, and in view of the distinct regional differences of the in vivo activity of glucose-6-phosphatase (G6Pase), these techniques were used on livers from male rats to investigate the distribution of the ketogenic enzyme, 3-hydroxybutyrate dehydrogenase (3-HBDH), during the post-resorptive phase. A close reciprocity was found between the general increase in the activity of 3-HBDH and the decrease of the in vivo activity of G6Pase along the sinusoidal axis, and also with regard to enzyme gradients along sinusoids of different origin. The activity of the ketogenic enzyme was higher throughout septal than portal sinusoids, whereas the opposite applied to the glucogenic enzyme. Histo- and microchemical data support the concept of a lobular parenchymal unit composed of "primary lobules," and show also that hepatocyte function varies with cell location along the sinusoidal axis and with the origin of the sinusoids.