Sandro Carrara

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

Screen-printed electrodes based on carbon nanotubes and cytochrome P450scc for highly sensitive cholesterol biosensors

This paper is concerned with an investigation of electron transfer between cytochrome P450scc (CYP11A1) immobilized on nanostructured rhodium-graphite electrodes. Multi-walled carbon nanotubes (MWCNT) were deposited onto the rhodium-graphite electrodes by drop casting. Cytochrome P450scc was deposited onto MWCNT-modified rhodium-graphite electrodes. Cytochrome P450scc was also deposited onto both gold nanoparticle-modified and bare rhodium-graphite electrodes, in order to have a comparison with our previous works in this field. Cyclic voltammetry indicated largest enhanced activity of the enzyme at the MWCNT-modified surface. The role of the nanotubes in mediating electron transfer to the cytochrome P450scc was verified as further improved with respect to the case of rhodium-graphite electrodes modified by the use of gold nanoparticles. The sensitivity of our system in cholesterol sensing is higher by orders of magnitude with respect to other similar systems very recently published that are based on cholesterol oxidase and esterase. The electron transfer improvement attained by the use of MWCNT in P450-based cholesterol biosensors was demonstrated to be larger than 2.4 times with respect to the use of gold nanoparticles and 17.8 times larger with respect to the case of simple bare electrodes. The sensitivity was equal to 1.12 microA/(mM mm(2)) and the linearity of the biosensor response was improved with respect to the use of gold nanoparticles.

Energy Harvesting and Remote Powering for Implantable Biosensors

This paper reviews some popular techniques to harvest energy for implantable biosensors. For each technique, the advantages and drawbacks are discussed. Emphasis is placed on the inductive links that are able to deliver power wirelessly through the biological tissues and enable bidirectional data communication with the implanted sensors. Finally, high-frequency inductive links are described, focusing also on the power absorbed by the tissues.

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

Implantable enzyme amperometric biosensors

The implantable enzyme amperometric biosensor continues as the dominant in vivo format for the detection, monitoring and reporting of biochemical analytes related to a wide range of pathologies. Widely used in animal studies, there is increasing emphasis on their use in diabetes care and management, the management of trauma-associated hemorrhage and in critical care monitoring by intensivists in the ICU. These frontier opportunities demand continuous indwelling performance for up to several years, well in excess of the currently approved seven days. This review outlines the many challenges to successful deployment of chronically implantable amperometric enzyme biosensors and emphasizes the emerging technological approaches in their continued development. The foreign body response plays a prominent role in implantable biotransducer failure. Topics considering the approaches to mitigate the inflammatory response, use of biomimetic chemistries, nanostructured topographies, drug eluting constructs, and tissue-to-device interface modulus matching are reviewed. Similarly, factors that influence biotransducer performance such as enzyme stability, substrate interference, mediator selection and calibration are reviewed. For the biosensor system, the opportunities and challenges of integration, guided by footprint requirements, the limitations of mixed signal electronics, and power requirements, has produced three systems approaches. The potential is great. However, integration along the multiple length scales needed to address fundamental issues and integration across the diverse disciplines needed to achieve success of these highly integrated systems, continues to be a challenge in the development and deployment of implantable amperometric enzyme biosensor systems.

Multi-panel drugs detection in human serum for personalized therapy

This work focuses on P450 biosensors based on multiwalled carbon nanotubes (MWCNT) and different cytochrome isoforms: 3A4, 2B4, 2C9. The proposed biosensors exhibit enhanced sensitivities and decreased detection limits thanks to carbon nanotubes. The MWCNT structuring improves the sensitivity from 5.1 to 20.5 nA/mM mm(2) in case of CYP2B4-mediated Benzphetamine detection, from 0.26 to 0.63 nA/μM mm(2) in case of CYP3A4-mediated Cyclophosphamide detection, and from 0.11 to 0.25 nA/μM mm(2) in case of CYP2C9-mediated Naproxen detection. By using MWCNT, the limit of detection was enhanced from 59 to 12 μM in case of Cyclophosphamide and from to 187 to 82 μM in case of Naproxen. This makes possible the drug detection in human serum within the pharmacological range. In the paper, a new mathematical model is also proposed to succeed in discriminating different drug contributions in a mixture containing both Cyclophosphamide and Dextromethorphan or combining Naproxen and Flurbiprofen. Data analysis shows variations in reduction peaks that are dependent on the drug ratio, and that are consistent with competitive kinetics of substrates. This new approach enables multiple drug detection and opens the way to possible applications in personalized therapy.

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications.

Electrochemical detection of anti-breast-cancer agents in human serum by cytochrome P450-coated carbon nanotubes.

We report on the electrochemical detection of anti-cancer drugs in human serum with sensitivity values in the range of 8–925 nA/μM. Multi-walled carbon nanotubes were functionalized with three different cytochrome P450 isoforms (CYP1A2, CYP2B6, and CYP3A4). A model used to effectively describe the cytochrome P450 deposition onto carbon nanotubes was confirmed by Monte Carlo simulations. Voltammetric measurements were performed in phosphate buffer saline (PBS) as well as in human serum, giving well-defined current responses upon addition of increasing concentrations of anti-cancer drugs. The results assert the capability to measure concentration of drugs in the pharmacological ranges in human serum. Another important result is the possibility to detect pairs of drugs present in the same sample, which is highly required in case of therapies with high side-effects risk and in anti-cancer pharmacological treatments based on mixtures of different drugs. Our technology holds potentials for inexpensive multi-panel drug-monitoring in personalized therapy.

Electrochemical biosensors and nanobiosensors.

Electrochemical techniques have great promise for low-cost miniaturised easy-to-use portable devices for a wide range of applications–in particular, medical diagnosis and environmental monitoring. Different techniques can be used for biosensing, with amperometric devices taking the central role due to their widespread application in glucose monitoring. In fact, glucose biosensing takes an approximately 70% share of the biosensor market due to the need for diabetic patients to monitor their sugar levels several times a day, making it an appealing commercial market. In this review, we present the basic principles of electrochemical biosensor devices. A description of the different generations of glucose sensors is used to describe in some detail the operation of amperometric sensors and how the introduction of mediators can enhance the performance of the sensors. Electrochemical impedance spectroscopy is a technique being increasingly used in devices due to its ability to detect variations in resistance and capacitance upon binding events. Novel advances in electrochemical sensors, due to the use of nanomaterials such as carbon nanotubes and graphene, are presented as well as future directions that the field is taking.

Continuous monitoring of Naproxen by a cytochrome P450-based electrochemical sensor

This paper reports the characterization of an electrochemical biosensor for the continuous monitoring of Naproxen based on cytochrome P450. The electrochemical biosensor is based on the drop-casting of multi-walled carbon-nanotubes (MWCNTs) and microsomal cytochrome P4501A2 (msCYP1A2) on a graphite screen-printed electrode (SPE). The proposed biosensor was employed to monitor Naproxen (NAP), a well-known anti-inflammatory compound, through cyclic voltammetry. The dynamic linear range for the amperometric detection of NAP had an upper limit of 300 µM with a corresponding limit of detection (LOD) of 16 ± 1 µM (S/N=3), which is included in NAP physiological range (9-300 µM). The MWCNT/msCYP1A2-SPE sensor was also calibrated for NAP detection in mouse serum that was previously extracted from mice, showing a slightly higher LOD (33 ± 18 µM). The stability of the msCYP1A2-based biosensor was assessed by longtime continuous cyclic voltammetric measurements. The ability of the sensor to monitor drug delivery was investigated by using a commercial micro-osmotic pump. Results show that the MWCNT/msCYP1A2-SPE sensor is capable of precisely monitoring the real-time delivery of NAP for 16 h. This work proves that the proposed electrochemical sensor might represent an innovative point-of-care solution for the personalization of drug therapies, as well as for pharmacokinetic studies in both animals and humans.