Integrated biodetection in a nanofluidic device

The sensing of enzymatic processes in volumes at or below the scale of single cells is challenging but highly desirable in the study of biochemical processes. Here we demonstrate a nanofluidic device that combines an enzymatic recognition element and electrochemical signal transduction within a six-femtoliter volume. Our approach is based on localized immobilization of the enzyme tyrosinase in a microfabricated nanogap electrochemical transducer. The enzymatic reaction product quinone is localized in the confined space of a nanochannel in which efficient redox cycling also takes place. Thus, the sensor allows the sensitive detection of minute amounts of product molecules generated by the enzyme in real time. This method is ideally suited for the study of ultra-small-volume systems such as the contents of individual biological cells or organelles

Isoflavone aglycons-sulfobutyl ether-β-cyclodextrin inclusion complexes: in solution and solid state studies

he effect of a polyanionic variably substituted sulfobutyl ether-β-cyclodextrin (SBE-β-CyD), complexation on the UV absorption of genistein (Gen) and daidzein (Dai) was studied in pure water. A phase solubility study was performed, according to the method reported by Higuchi and Connors, to evaluate the changes of isoflavones in the complexation state and type-AL solubility diagrams for both isoflavones were obtained suggesting that they form complexes with 1:1 molar ratio. These results were confirmed by Job's plot method. Complexation strongly increases the water solubility of isoflavones. The in vitro dissolution of isoflavones entrapped into SBE-β-CyD significantly surpassed that of the free isoflavones (over 90 % of the loaded Gen and Dai dissolved in 15 and 30 min, respectively). Finally, 1:1 molar ratio solid complexes were prepared by the kneading method and characterized in solid state by FTIR-ATR spectroscopy, with particular regard to O-H and C=O stretching vibrations, achieving structural information on the modifications induced by complexation on the H-bond scheme, also by applying band decomposition and curve-fi