Our research focuses on the development of sensors constructed using nanomaterials such as carbon nanotubes and indium oxide nanowires. There are several types of nanobiosensor. Several nanobiosensors have been fabricated using nanocantilevers, nanoparticles, or quantum dots but these need to be couple to an optical detection method. The most promising nanobiosensors are the those based the electrocnic detection of the target molecule such as field effect transistor nanosensors (FET). These devices are still in the early stages of development but have made impressive progress over the past 5 years. Each single nanobiosensor is capable of identifying the specific biomarker for which it was designed. Large arrays entailing hundreds of FET nanobiosensors could be constructed to fit on the tip of a needle for a very broad screening of biomarkers and other medically useful biomolecules. For instance, in the field of oncology, dozens or even hundreds of biomarkers of specific tumours could be monitored and the presence of a growing tumour can be detected while the cancer is still in very early stages of growth -- months, if not years, before it could be detected using currently available diagnostic imaging technologies. FET nanobiosensors are highly specific to their targets and produce a signal in a very short period of time (generally a few seconds); consequently, the need for laboratory-based analysis could be substantially reduced.
The "sensing element" of a Field Effect Transistor (FET) nanobiosensor is the semiconductor channel (nanowire) of the transistor. This channel is fabricated using nanosized materials such as carbon nanotubes, metal oxide nanowires (ex: In2O3), or Si nanowires. A unique property of these materials is the very high surface to volume ratio: a very large portion of the atoms are located on the surface for the nanowires whereas all the atoms are surface atoms in the case of carbon nanotubes. Because of this, the nanowire/nanotube becomes extremely sensitive to the environment and to everything coming in close contact to its surface.
A specific recognition group can be used to coat the surface of the nanowire/nanotube, making the device specifically sensitive only to a particular target. This recognition group could be a single stranded DNA (capable of recognizing its complementary strand), an antibody (that recognize a particular antigene), an aptamer that shows affinity for a unique target, or a protein that specifically interact with another biological molecule. The presence of this recognition group on the nanowire surface gives to the device high specificity and exclusivity toward its target.
Once the nanowire based transistor has been coated with a specific recognition group, the device is ready to function as a nanobiosensor. In a working nanobiosensor, the current flowing throught the nanowire is monitored versus time. Initially, some voltage is applied between the transistor's source and drain and the resulting current is used asbaseline signal. At this point the device is contact with some physiological solution but the target molecule is not present.
The target biomolecule is usually a charged molecule in aqueous media. These charges can act as chemical gate for the transistor, modifying its electrical properties. These charges influence the current flow in the nanowire by injecting holes or electron. Once the target molecule interacts with the surface of the nanowire/nanotube, the current flowing through the nanowire either decreases or increases (depending on the type of charge injected). This is the signal that alert the analyst about the presence of biomolecule for which the nanobiosensor was designed.
These two NanoBioSensors were designed to detect the presence of the PSA protein, a biomarker used in oncology to monitor the growth of prostate cancer. The top device was fabricated using a single Indium Oxide nanowire whereas the bottom device was made with a mat of carbon nanotubes. After having established a baseline current we added: a drop of buffer solution to check how the mechanical disturbance would affected the baseline signal; a solution containing the BSA protein, a non-target molecule for which our device did not show any response; a solution containing the PSA protein, which, upon interacting with the device surface, caused the conductivity to change (positive response).
The "sensing element" of a Field Effect Transistor (FET) nanobiosensor is the semiconductor channel (nanowire) of the transistor. This channel is fabricated using nanosized materials such as carbon nanotubes, metal oxide nanowires (ex: In2O3), or Si nanowires. A unique property of these materials is the very high surface to volume ratio: a very large portion of the atoms are located on the surface for the nanowires whereas all the atoms are surface atoms in the case of carbon nanotubes. Because of this, the nanowire/nanotube becomes extremely sensitive to the environment and to everything coming in close contact to its surface.
A specific recognition group can be used to coat the surface of the nanowire/nanotube, making the device specifically sensitive only to a particular target. This recognition group could be a single stranded DNA (capable of recognizing its complementary strand), an antibody (that recognize a particular antigene), an aptamer that shows affinity for a unique target, or a protein that specifically interact with another biological molecule. The presence of this recognition group on the nanowire surface gives to the device high specificity and exclusivity toward its target.
Once the nanowire based transistor has been coated with a specific recognition group, the device is ready to function as a nanobiosensor. In a working nanobiosensor, the current flowing throught the nanowire is monitored versus time. Initially, some voltage is applied between the transistor's source and drain and the resulting current is used asbaseline signal. At this point the device is contact with some physiological solution but the target molecule is not present.
The target biomolecule is usually a charged molecule in aqueous media. These charges can act as chemical gate for the transistor, modifying its electrical properties. These charges influence the current flow in the nanowire by injecting holes or electron. Once the target molecule interacts with the surface of the nanowire/nanotube, the current flowing through the nanowire either decreases or increases (depending on the type of charge injected). This is the signal that alert the analyst about the presence of biomolecule for which the nanobiosensor was designed.
These two NanoBioSensors were designed to detect the presence of the PSA protein, a biomarker used in oncology to monitor the growth of prostate cancer. The top device was fabricated using a single Indium Oxide nanowire whereas the bottom device was made with a mat of carbon nanotubes. After having established a baseline current we added: a drop of buffer solution to check how the mechanical disturbance would affected the baseline signal; a solution containing the BSA protein, a non-target molecule for which our device did not show any response; a solution containing the PSA protein, which, upon interacting with the device surface, caused the conductivity to change (positive response).