There is an increasing need for rapid, small scale and highly sensitive detection of biological molecules in medical, bioterrorism, food safety, and research applications. Nanostructures such as silicon nanowires and carbon nanotubes display physical and electronic properties amenable to use in miniature devices.
Carbon nanotubes (CNTs) are rolled up graphene sheets having a diameter on the nanometer scale and typical lengths of up to several micrometers. CNTs can behave as semiconductors or metals depending on their chirality. Additionally, dissimilar carbon nanotubes may contact each other allowing the formation of a conductive path with interesting electrical, magnetic, nonlinear optical, thermal and mechanical properties.
E. I. du Pont de Nemours and Company (Wilmington, DE) reveals a nanosensor for the detection of an analyte such as a bioterrorism agent, a disease agent, a genetic disorder, an environmental contaminant, or a food pathogen in U.S. Patent 7,635,423.
According to inventors Salah Boussaad, Bruce A. Diner, Janine Fan; (Hockessin, DE), Vsevolod Rostovtsev, and Ajit Krishnan, the nanosensor is comprised of an electrically conducting path of semiconducting single walled carbon nanotubes having a baseline conductance, in contact with an effector solution comprising a redox effector molecule.
The effector solution has a given redox potential that is correlated to the redox state of the redox effector molecule. Modulations in the redox potential of the effector solution give rise to changes in the conductance of the CNT with respect to the baseline conductance. The nanosensor additionally comprises a redox reporter that interacts with a redox active substrate and co-substrate. In the presence of an analyte the reporter interacts with the substrate and co-substrate oxidizing one and reducing the other altering the redox potential of the effector solution.
Several advantages of this detection system are 1) the analyte or capture moiety-analyte complex itself does not need to directly change the conductance of the CNT; 2) the capture moiety does not need to be attached to or be in close proximity to the CNT; and, where the reporter is an enzyme; 3) the signal is greatly amplified through the turnover of the redox reporter.
The du Pont biosensor also provides a method for detecting an analyte indirectly by first binding the analyte to a capture moiety that is attached to a surface, binding a redox reporter conjugate to the bound analyte, which acts upon a redox-active substrate and co-substrate. The change in redox potential of one of the substrates, acting as the redox effector or of a redox mediator, in equilibrium with one of the substrates, and acting as the effector, is measured as a change in conductance of at least one semiconducting CNT in a conductive path in contact with the solution.
The du Pont biosensor also provides a method for detecting an analyte indirectly by first binding the analyte to a capture moiety that is attached to a surface, binding a redox reporter conjugate to the bound analyte, which acts upon a redox-active substrate and co-substrate. The change in redox potential of one of the substrates, acting as the redox effector or of a redox mediator, in equilibrium with one of the substrates, and acting as the effector, is measured as a change in conductance of at least one semiconducting CNT in a conductive path in contact with the solution.
Another embodied method is to bind an analyte that is redox active to a capture moiety. In the presence of a redox active substrate and a redox active co-substrate, one of which acts as the effector or alters the redox potential of a redox mediator which acts as the effector, a change in the redox potential of the effector is detected via a change in the conductance of at least one semiconducting CNT in a conductive path in contact with the solution.
An additional method for detecting an analyte indirectly is to allow an analyte that is a redox active substrate to react with a surface attached redox reporter in the presence of a co-substrate. One of the substrates, or a redox mediator in equilibrium with one of them, acts as the effector, the change in redox potential of which causes a change in the conductance of at least one semiconducting CNT in a conductive path in contact with the solution.
Highly sensitive nanoscale detection of biomolecules has utility in bioterrorism, biomedical, environmental, food safety, research, and other applications. Use of the system wherein detection by the CNTs is of a change in redox potential in solution increases the diversity of biomolecules that may be assayed and the sensitivity of detection. Samples may be screened to detect a target biomolecule that would indicate the presence of a bioterrorism agent, a disease agent, a genetic disorder, an environmental contaminant, a food pathogen, a desired product, and other such components.
Highly sensitive nanoscale detection of biomolecules has utility in bioterrorism, biomedical, environmental, food safety, research, and other applications. Use of the system wherein detection by the CNTs is of a change in redox potential in solution increases the diversity of biomolecules that may be assayed and the sensitivity of detection. Samples may be screened to detect a target biomolecule that would indicate the presence of a bioterrorism agent, a disease agent, a genetic disorder, an environmental contaminant, a food pathogen, a desired product, and other such components.
