If an effect can be evidenced

If an effect can be evidenced, it is detrimental to the device operation. In fact, the system is less sensitive and, if the standard deviation is considered (dot-dashed lines in Fig. 3), the two curves obtained by probe anchoring and perfect match hybridization almost overlap. The results show that in these conditions there is not enough confidence to detect DNA hybridization. Therefore, for our MOS-like systems, we focused on samples without BSA passivation. Fig. 4 shows the Si/SiO2 samples already described in Fig. 2 including their standard deviations (dot-dashed green lines). The shift of ~0.60V after hybridization is clearly wider than the errors; hence, it is a good measure the detection of DNA hybridization.
Conclusion MOS-like sensors for the direct detection of order clemastine fumarate have been investigated. We studied different dielectrics to detect DNA hybridization in order to define the best in terms of response and stability. By using SiO2 as dielectric, a shift of ~0.60V was measured after hybridization, well above the experimental errors. By simulating our devices with the commercial software Sentaurus® we determined that an electron density ~2×1012e−/cm2 produces a shift comparable with the experimental data. The simulation may help us to select, a priori, the DNA probe density on the sensitive area of the device in order to maximize the response. The other dielectrics studied, based on silicon nitride (Si3N4 and ONO), indicate that the trap presence in the nitride layer is detrimental to the device correct operation. Nevertheless, a proper device design, using ONO layers, may allow using the ONO “memory effect” to propose new biosensors for the detection of DNA hybridization.
Acknowledgments This work has been partially funded by the National Project MIUR-PON “Hyppocrates – Sviluppo di Micro e Nano – Tecnologie e Sistemi Avanzati per la Salute dell\'uomo” (PON02 00355).
Introduction In the last years, there has been a huge interest in the development of portable systems for DNA analysis, the so-called Biochip. These devices are miniaturised systems able to integrate on-chip all the basic functions for biochemical analysis combining consolidated process technologies (i.e. those silicon-based) with microfluidics functions such as transport, dispensing and mixing. The main cause of such a trend is mainly related to both the possibility to be massively produced (thanks to the consolidated production technologies) and their capability to give fast and reliable results in the analysis (thanks to the precise controls of the physical parameters of the DNA analysis). [1–4]. Due to Incompatibility advantages, biochips are expected to revolutionize clinical diagnosis of diseases, enabling the possibility to make fast diagnosis in the immediate closeness of patient (Point-of-Care, PoC) in a wide range of applications including oncology, drug discovery and infectious diseases [5–8]. Among the biotechnological methods used to analyse DNA, the qPCR (quantitative Polymerase Chain Reaction) is the most employed in the molecular diagnostic area. It is a biochemical technology able to generate thousands of million copies of a specific DNA segment through a thermal amplification process via the polymerase enzyme. The kinetic curve is measured in real time by recording a fluorescent signal coming from a specific dye. This signal is plotted against the number of amplification cycles on a logarithmic scale and the Cycle Threshold (CT) is extracted to quantify the DNA [9–12]. The use of such methodology in PoC format requires the development of portable and low-cost systems. These systems typically must integrate several technological modules such us thermal, optical, chemical and data analysis modules. The data analysis module is a combination between the detection system and the algorithm of analysis. For low cost instrument, usually charge-coupled device (CCD) detectors are employed to detect the fluorescent emission of DNA targets [1]. The structure of a typical fluorescent detection system consists of an excitation source such as a laser or a white light source or a Light Emitting Diode, light delivery optics, a narrowband interference filter to select a narrow spectrum of excitation light, light collection optics and a narrowband filter to isolate the emission spectrum of fluorochrome from its excitation spectrum, image sensor, and control and processing units.