Claudio Stagni

CMOS DNA Sensor Array With Integrated A/D Conversion Based on Label-Free Capacitance Measurement

This paper presents a fully electronic label-free DNA chip in 0.5-mum CMOS technology, with 5-V supply voltage, suitable for low-cost highly integrated applications. The chip features an array of 128 sensor sites with gold electrodes and integrated measurement, conditioning, multiplexing and analog-to-digital conversion circuitry. The circuits measure capacitance variations due to DNA hybridization on the gold electrodes which are bio-modified by covalently attaching probes of known sequence. Specificity, repeatability and parallel detection capability of the fabricated chip are successfully demonstrated

DNA detection by integrable electronics

This paper presents a new electronic methodology to detect DNA hybridization for rapid identification of diseases, as well as food and environmental monitoring on a genetic base. The proposed solution exploits a new (electrical) capacitive measurement circuit, not requiring any prior labeling of the DNA (as it is often the case with the commonly employed optical detection). The sensitivity, the reliability, and the reproducibility of this device have been evaluated by experiments performed with a (non-integrated) prototype implementation, easily integrable in IC and/or micro-fabricated lab-on-a-chip.

A Fully Electronic Label-Free DNA Sensor Chip

This paper presents a microfabricated DNA chip for fully electronic, label-free DNA recognition based on capacitance measurements. The chip has been fabricated in 0.5-mum CMOS technology and it features an array of individually addressable sensing sites consisting of pairs of gold electrodes and addressing logic. Read-out circuitry is built externally using standard components to provide increased experimental flexibility. The chip has been electrically characterized and tested with various solutions containing DNA samples. Significant capacitance variations due to DNA hybridization have been measured, thus showing that the approach represents a viable solution for a single chip DNA sensor array

Microelectrodes on a Silicon Chip for Label-Free Capacitive DNA Sensing

This paper presents the experimental characterization of two-terminal microfabricated capacitors for microarrays with an electrical sensing of label-free deoxyribonucleic acid (DNA). So far, such a concept has been demonstrated only in experimental setups featuring dimensions much larger than those typical of microfabrication. Therefore, this paper investigates: 1) the compatibility of the silicon microelectronic processes with biological functionalization procedures; 2) the effects of parasitics when electrodes have realistic dimensions; 3) measurement stability and reproducibility; and 4) the possibility of a fully integrated stand-alone device. The obtained results clearly indicate that two-terminal capacitive sensing with fully integrated electronics represents a viable technology for a DNA label-free detection/recognition

A Biosensor for Direct Detection of DNA Sequences Based on Capacitance Measurements

The large demand for DNA analysis calls for the development of portable, low-cost, easy-to-perform assays. We developed and performed preliminary assessments of an integrable biosensor for the direct detection of DNA sequences through capacitance measurements. The device behaves consistently with a proposed electrical model and it reliably detects DNA hybridization with high specificity. We have also verified the reproducibility of the experimental results and the reusability of the DNA biosensor.

New insights for using self-assembly materials to improve the detection stability in label-free DNA-chip and immuno-sensors

This paper examines reliable advancements in low-cost DNA- and immuno-chips. Capacitance detection was successfully chosen to develop label-free bio-chips. Probe immobilization was rigorously investigated in order to obtain reliable capacitance measurements. Protein probes immobilized by using usual alkanethiols or thiolated ssDNA probes directly immobilized on gold do not allow sufficient stable capacitance measurements. New alkanethiols improved with ethylene-glycol function are shown in this paper to be more suitable materials for capacitive bio-chip development. Atomic Force Microscopy, Quartz Crystal Microbalance, and Capacitance Measurements were used to demonstrate that ethylene-glycol alkanethiols allow high time stability, smaller errors in detection, and improved ideal behaviour of the sensing surfaces. Measured capacitance is in the range of 8-11 nF/mm(2) for antibody layers and close to 6 nF/mm(2) for DNA probes. It is in the range of 10-12 nF/mm(2) and of 4-6 nF/mm(2) for antigen and DNA detection, respectively. The percentage error in detection is highly improved and it is in the range of 11-37% and of 0,23-0,82% for antigen and DNA, respectively. The reproducibility is also improved and it is close to 0,44% for single spot measurements on ethylene-glycol alkanethiols. A molecular theory attributing these improvements to water molecules strongly coordinated by ethylene-glycol functional groups and to solution ions not entering into probe films is finally proposed.

Fully Electronic CMOS DNA Detection Array Based on Capacitance Measurement with On-Chip Analog-to-Digital Conversion

An 8 times 16 array of sensing micro-sites employs a fully-electrical label-free technique for DNA recognition using capacitance measurement and is fabricated in 0.5mum CMOS with added noble metal. Repeatability and parallel detection capability have been demonstrated. The DNA-chip is suitable for low-cost, fully-integrated point-of-care applications

Smart sensors for fast biological analysis

This paper presents an updated overview of present works concerning the realization of biological sensors based on electronic devices. In particular DNA sensors will be described and their main characteristics will be analyzed. As an example, a new sensor for DNA detection and analysis will be described in details. The proposed approach is based on the use of non-volatile memories and does not require sample treatment nor sensor surface functionalization. Moreover fabrication technology is widely compatible with standard CMOS process. Experimental results show that the sensor has sufficient accuracy and sensitivity, that can be further improved by suitable device engineering.

Hardware-Software Design of a Smart Sensor for Fully-Electronic DNA Hybridization Detection

The paper describes the design of a smart sensor for label-free detection of DNA hybridization. The sensor is based on a direct electrical transduction principle: it measures impedance variation at the interface between a bio-functionalized electrode and a solution containing the analyte. The smart sensor includes a complete signal conditioning and processing subsystem based on an embedded /spl mu/-controller. We outline the sensor architecture, and we describe in detail board-level integration as well as hardware and software implementation and design choices. The accuracy of our embedded solution has been evaluated by comparing it with a high-cost laboratory setup. Moreover, we provide measurements of real sensing structures which demonstrate the functionality of our system in the field.