Modeling of SAM Impedance Onto Gold and Silver Thin-Film Mass-Produced Electrodes and Their Use for Optimization of Lactic Acid Detection.

In this work, we demonstrate how an innovative, out-of-cleanroom customized CD/DVD fabrication process can be successfully used for mass production of biosensors with thin-film electrodes. We show that silver and gold electrodes can be used for impedimetric and voltammetric biosensing applications, both in presence and absence of a redox mediator. We modeled the redox/non-redox electrodes impedance through equivalent electrical circuits, and we evaluated their transfer function sensitivity with a one-factor-at-a-time approach. Using this approach, we introduced a new prediction method to find which equivalent electrical circuit elements contribute more to the transfer function variations, then we experimentally validated the predictions measuring the electrodes electrochemical impedance spectroscopy responses with relevant self-assembled monolayer molecules immobilized on them, i.e., MCH and DTSP. We also assess the silver electrodes long-term stability with impedance spectroscopy measurements over a period of 1200 hours, proving their possible use in point-of-care applications. Finally, we also prove that the sensors correctly perform in a practical case, i.e., as a lactic acid biosensor, by studying the optimization of the biosensor efficiency through different enzyme immobilization methods. By comparing lactate oxidase enzyme direct adsorption and covalent binding to DTSP self-assembling monolayers, we found that covalent binding to DTSP can boost the catalytic current of about 40% with respect to that obtained from the direct adsorption of the same enzyme concentration.

Enhancement and control of surface plasmon resonance sensitivity using grating in conical mounting configuration.

In this work we propose a method to enhance and control the angular sensitivity of a grating coupled surface plasmon resonance (GCSPR) sensor. We lighted a silver grating, mounted in conical configuration, with a laser source and we measured the transmittance of the grating as a function of the azimuthal angle. To evaluate the sensitivity, grating surface was functionalized with four different alkanethiol self assembled monolayers (SAM) and the correspondent azimuthal transmittance peak shifts were measured. The sensitivity control was performed by simply change the light incident angle. This method offers the possibility to design dynamic GCSPR sensor benches that can be used to amplify the SPR angle shift at any step of a biological detection process.

Development of a complete plasmonic grating-based sensor and its application for self-assembled monolayer detection.

This work presents an integrated plasmonic biosensing device consisting of a one-dimensional metallic lamellar grating designed to exploit extraordinary transmission of light toward an underlying silicon photodetector. By means of finite element simulations, the grating parameters have been optimized to maximize the light transmission variation induced by the functionalization of the gold nanostructures. An optimized grating was fabricated using an electron beam process and an optoelectronic test bench suitable for sample tests was developed. A clear difference in the grating transmitted light due to surface functionalization was observed in presence of TM polarized illumination.

A proposito de um caso de fistula uretrorretal iatrogenica. / Apropos of a case of iatrogenic rectourethral fistula

E apresentado um caso de fistula uretrorretal com estenose de uretra, como complicacoes de prostatectomia transvesical, onde a enucleacao foi dificultada por aderencias fibrosas. Por acesso perineal, a fistula foi corrigida cirurgicamente,assim como a estenose uretral. Obteve-se sucesso com o procedimento empregado