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BIOELECTRONIC OLFACTORY NEURON DEVICE

Final Report Summary - BOND (Bioelectronic olfactory neuron device)

Executive summary:

Recently, the use of smell in different fields has been rediscovered due to major advances in odour sensing technology and artificial intelligence. However, even if current electronic and electrochemical-based nose devices can detect and identify some odorants, the usefulness and deployment of these products is very limited and restricted to some highly specific applications like process monitoring or environmental detection of natural products. The limited impact of the available systems is due to their significant limitations concerning sensitivity, reliability and selectivity. Thus, they do not meet the full operational capabilities demanded by a large number of potential end users in different areas, such as food safety, diagnosis, security and environment.

A new approach developed in the Spot-Nosed project (2003 to 2006), funded by the Fifth Framework Programme (FP5) 'Future and emerging technologies', proved that it is possible to use ORs (Ors), proteins located at the plasma membrane of olfactory neurons, as the sensing elements of electronic noses. Following this new concept, the objective of the BOND project has been to develop a new generation of bio-electronic nose devices that relies, contrary to previous approaches, on the fantastic analytical properties of the mammalian nose: specificity, sensitivity, identification of mixed signatures and real-time response.

Therefore, the bioelectronic olfactory neuron device (BOND) is an integrated bioelectronic analytical platform where the currently used physical or chemical sensing elements are replaced by ORs. The device is the result from scaling down this new biotechnology and integrating it into a single artificial device using nano and information technologies. Furthermore, the OR-based nanobiosensors have been interfaced with an electronic and highly-miniaturised apparatus that will confer to the system additional advantages: portability, low cost, user-friendliness and on-line monitoring.

The general objective of the BOND project has been to develop an array of smart nanobiosensors containing a large number of different ORs working simultaneously and in a complementary way for detection of odorant signatures that will offer:

1. extremely high sensitivity, thus making possible the detection of low concentrations of odorant molecules (below 0.1 ppb)
2. maximum reliability and capability of detecting odorant volatile molecules of small size, below 300 Da
3. very high specificity for a given odorant molecule and, at the same time, capability of detecting a broad range of the volatile odorant chemicals composing an odorant profile or fingerprint
4. real-time response, this parameter being mostly dependent upon data processing
5. easy-to-use environment, low degree of expertise required to operate such an instrument due to a user-friendly interface
6. portable equipment, implemented on a sensor-on-chip platform
7. affordable sensor system: low price, including both instrumentation and analysis costs.

After the development and integration of the main technologies and components of the new bioelectronic analytical platform, the BOND consortium has succeed in the assembly of the first complete prototype. Moreover, this prototype has been successfully tested and the BOND platform has been validated for a target application in the area of food quality.

Project context and objectives:

Recently, the use of smell in different fields has been rediscovered due to major advances in odour sensing technology and artificial intelligence. However, even if current electronic and electrochemical-based nose devices can detect and identify some odorants, the usefulness and deployment of these products is very limited and restricted to some highly specific applications like process monitoring or environmental detection of natural products. The limited impact of the available systems is due to their significant limitations concerning sensitivity, reliability and selectivity. Thus, they do not meet the full operational capabilities demanded by a large number of potential end users in different areas, such as food safety, diagnosis, security and environment.

A new approach developed in the Spot-Nosed project (2003 to 2006), funded by the FP5 'Future and emerging technologies' program, proved that it is possible to use olfactory receptors (ORs, proteins located at the plasma membrane of olfactory neurons) as the sensing elements of electronic noses. Following this new concept, the objective of the BOND project is to develop a new generation of bio-electronic nose devices that relies, contrary to previous approaches, on the fantastic analytical properties of the mammalian nose: specificity, sensitivity, identification of mixed signatures and real-time response.

Therefore, the BOND will be an integrated bioelectronic analytical platform where the currently used physical or chemical sensing elements are replaced by ORs. The device will result from scaling down this new biotechnology and integrating it into a single artificial device using nano and information technologies. Furthermore, the proposed OR-based nanobiosensors will be interfaced with an electronic and highly-miniaturised apparatus that will confer to the system additional advantages: portability, low cost, user-friendliness and on-line monitoring.

The general objective of the BOND project is to develop an array of smart nanobiosensors containing a large number of different ORs working simultaneously and in a complementary way for detection of odorant signatures.

Project results:

During the first months of the project, the members of the BOND consortium selected two target applications for the device in the areas of food quality and clinical diagnosis. Taking into account the requirements of these applications, the first design of the bioelectronic nose was achieved.

The BOND consortium also progressed in the development of the different components and procedures of the bioelectronic device, leading to the following key results:

1. determination of the target odorants that will be detected by the device in order to fulfil the requirements of the targeted food quality controls
2. identification, cloning and expression of most of the ORs specific of the target odorants
3. design and fabrication of the first version of the nanotransducers (nanoelectrodes)
4. design and fabrication of the front-end electronic circuitry
5. design of specific nanotools for the characterisation at the nanoscale of the nanobiosensors
6. development of an improved microscopic model of electrical transport in proteins tested and validated for two different ORs.

During the second period of the project, the members of the BOND consortium focused in the integration of the main components of the Bioelectronic Analytical Platform, leading to the assembly of the first complete prototype. Moreover, this prototype has been successfully tested and the BOND platform has been validated for a target application in the area of food quality.

The main components of the project have been also improved leading to the following achievements:

1.production and functional assessment of the ORs specific of the target odorant required for food quality controls
2. identification, cloning and expression of ORs specific of a target odorant related to cancer diagnosis
3. design and fabrication of the final version of the nanotransducers (integrated electrochemical cell including counter, reference and optimised working electrodes)
4. design and fabrication of an optimised electronic front-end module for high sensitivity impedance spectroscopy measurements
5. design and fabrication of improved nanotools for the characterisation at the nanoscale of the nanobiosensors
6. development of an improved theoretical model for the electron tunneling through single proteins and a theoretical interpretation of the nanobiosensor response
7. design, fabrication and assembly of a self-contained portable analyser for data acquisition and processing
8. design and fabrication of an improved electromechanical interface between the removable nanotransducers and the analyser.

Potential impact:

The BOND consortium has developed a nanobiosensor based on recognition of odorant patterns by ORs, which can be applied to different fields for the general purpose of monitoring the presence and/or measuring the concentration of specific odorants. The potential applications for a precise, safe & reliable and rapid odour sensor are numerous and promising in many fields where these factors are of crucial importance: food safety and quality control, cosmetics, protection of the environment, on-line monitoring of industrial or environmental processes, safety controls, clinical diagnosis, etc. Among these potential applications, the BOND consortium has decided to focus on two applications related to two important economic areas such as the food industry, and the healthcare/medical Industry.

Applications in the field of health and medicine are likely to drastically diminish the cost of disease diagnosis and monitoring, as well as allowing their use in a larger population, for early detection and prevention of diseases. Moreover, the existing diagnosis and monitoring tools for some diseases are either strongly invasive or considerably non-specific. The possibility to diagnose and monitor diseases, and in particular some cancers, by measuring the concentration of volatile markers in body fluids (or in the breath) has gained acceptance in recent years within the medical community. Thus, the new family of BOND bioelectronic noses could provide highly specific, highly sensitive and non-invasive diagnostic tools.

Besides, measurements to ensure food safety and food quality are a critical need for our society. The detection of contaminated food products in a rapid and accurate manner before consumption would benefit the buyer market. The sensing of critical indicator volatile odorants markers using a bioelectronic olfactory nose is one of the many potential methods for developing sensors for detecting contamination in food products. It is also important to be able to distinguish between different quality classes of the same food to avoid fraud ant to fulfil customer expectations. Equally important is knowledge of the ingredients of a product to protect the customer from low-quality raw material and/or to avoid breaking the law. To develop an accurate artificial olfactory sensing system to be used as sensor, it is imperative to understand and analyse the olfactory system in human beings (and other mammals). The ORs and odour binding proteins from animals with their neuro-integrative strategies can aid the engineering of a robust and reproducible olfactory sensor.

Finally, the interdisciplinary approach of the BOND project presents also a great challenge to understand the nanoscopic mechanisms controlling protein sensing actions and will certainly lead to the creation of new types of biosensors (based in sensing proteins other than ORs) with potential applications in all of the stated sectors.

List of websites:

http://www.bondproject.org

Contact:

Prof. Josep Samitier Martí

Adress: C/Baldiri Reixach, 10-12, 08028 Barcelona (Spain)

E-mail: jsamitier@ub.edu

Telephone: +34-934-031198

Fax: +34-934-039702