***Archived: This is a past project, it is not on offer at the moment!***
Introduction
The emerging need for fast, easy-to-use, highly sensitive and low-cost point-of-care testing devices dedicated to distributed diagnostics and personalized theraphy has spurred multidisciplinary research on the development of nanobioelectronics. Among nanometer-scale material, carbon nanotubes (CNTs) are particularly interesting as the active material for biological and chemical sensors: their high carriers mobility, their smallest diameter (~1 nm) directly comparable to the size of the target molecules and their unique geometry consisting of one-dimensional electronic material comprising only surface atoms, make CNTs well suited for electronic detection that relies on electrostatic interactions with analyte biomolecules. All these features make carbon nanotube (CNT) biosensors promising devices to enhance conventional biosensors in term of sensitivity, scalability and ease in realizing complex massive sensor arrays. Moreover, bio-detection is also required to be highly specific in order to succeed in disease discrimination and analysis of drugs efficacy on the patients. FET technology provides control in multi-panel biochip to enhance specifity in detecting multiple drugs. Current available tools, based on monitoring system for genetic predisposition to drug metabolism, cannot acquire information about drugs concentration on real-time basis. For these reasons, reliable point-of-care technologies to monitor multiple drug compounds in patient’s plasma are absolutely required in therapy personalization. Biosensors based on individual P450 proteins have already been proposed to develop novel drug screening tools. P450-CNFET based bio sensors are very promising to fill the gap needed by tools for personalized theraphy.
The Master Project
Aim of this Master Project is to design a new device specially dedicated to distributed diagnostics to measure multiple drugs concentrations in real-time directly in patient’s blood samples. In particular, the project is focused on the microfabrication of an array of Carbon Nanotube Field Effect Transistors (CNTFETs) to provide nano-biosensing based on cytochrome P450. The ideal CNTFET Sensor Array (CSA) for multi-drug detection comprises of multiple gates; individual polarization of each gates enables indipendent control of the channels which are made of distinct bundles of SWCNTs. In the present project the most simple configuration is employed: only two gates are used to control the corrisponding CNT channels and hence the drug detection. The microfabrication process includes two metal deposition and contacts patterning defined using standard lithography. Aluminum is employed for the gates (width ~ 500 nm), while palladium is used for source and drain electrodes (channel lenght of 2 µm). The challenge of the present microfabrication is using aligned SWCNTs as the channels of the FET. The alignment can be achieved by using the Langmuir-Blodgett technique: aligned SWCNT Langmuir-Blodgett films can be deposited after aluminum deposition to cover the wafer and fixed by palladium deposition. Since the final goal is controlling independently all the gates, hence each channels, arrayed bundles of CNTs has to be placed on the top of each gate and all the CNTs deposited between them can be removed by selective plasma etching. Eventually, taking into account that all the measurements have to be carried out in a wet environment, a passivation layer has to be deposited in order to insulate the parts of the chip we do not want to functionalize with protein. As the last step of the fabrication process, each CNT-channel is functionalized with the proper P450 isoform. The one-to-one binding of P450 cytochromes and the gates is performed by activating each gate at a time while exposing the CNT channel to the respective P450 solution: during the exposure, respective P450 isoform is trapped onto the proper CNTs bundle driven by the single gate by using protein electrostatic trapping. Moreover, taking into account that the sensitivity of the CSA is proportional to the amount of P450s bonded to the conducting CNTs, a desired sensitivity level can be achieved by optimizing the active area.
A so realized multi-panel CNTFET biochip enables early identification of drug candidates in human’s samples by mutliplexing different P450 probes: multiple query of differently polarized CNT-FET channels improve the specificity in drugs detection.
Tasks:
- Micro- and nano-fabrication of electrical devices
- Nano-structuring FET with carbon nanotubes monolayer
- Fabrication of Langmuir Blodgett Films of CNTs
- Bio-functionalize the nano-structured CNT-FET channels with the proteins P450
- Acquiring electrochemical signals from the nano-structures
- Computing the sensing performances obtained by nano-structuring
Requirements:
- Basic knowledge on FET technology
- Basic knowledge on sensors
- Basic Knowledge on nanotechnology
- Basic knowledge on Langmuir Blodgett technique
- Experience with microfabrication process
- Experience with electrical measurements with lab equipments
- Interest in diagnostics for personalized therapy
This project was supervised by Sandro Carrara.
***Archived: This is a past project, it is not on offer at the moment!***