Development of immunosensors using carbon nanotubes

Biosensors based on carbon nanotube-network field-effect transistors

We describe in detail the different steps involved in the construction of a carbon nanotube field-effect transistor (CNTFET) based on a network of single-walled carbon nanotubes (SWCNTs), which can selectively detect human immunoglobulin G (HIgG). HIgG antibodies, which are strongly adsorbed onto the walls of the SWCNTs, are the basic elements of the recognition layer. The nonspecific binding of proteins or other interferences are avoided by covering the nonadsorbed areas of the SWCNTs with Tween 20. The CNTFET is a reagentless device that does not need labels to detect HIgG.

Nanowire and nanotube transistors for lab-on-a-chip applications

Implementation of one-dimensional nanostructure-based devices in the lab-on-a-chip framework can allow us to impart various functionalities such as highly-sensitive sensors to a single chip. However, it is still extremely difficult to position nanowires or nanotubes on a defined area of solid substrates to build integrated functional devices. Herein, we review promising strategies for the massive integration of nanowires/nanotubes on lab-on-a-chip and their practical applications to sensors. The theoretical understanding and sensor characteristics of nanowire/nanotube-based devices are also discussed.

Covalent immobilization of proteins on carbon nanotubes using the cross-linker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide--a critical assessment

Functionalization of carbon nanotubes (CNTs) with proteins is often a key step in their biological applications, particularly in biosensing. One popular method has used the cross-linker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) to covalently conjugate proteins onto carboxylated CNTs. In this article, we critically assess the evidence presented in these conjugation studies in the literature. As CNTs have a natural affinity for diverse proteins through hydrophobic and electrostatic interactions, it is therefore important to differentiate protein covalent attachment from adsorption in the immobilization mechanism. Unfortunately, many studies of conjugating proteins onto CNTs using EDC lacked essential controls to eliminate the possibility of protein adsorption. In studies where the attachment was claimed to be covalent, discrepancies existed and the observed immobilization appeared to be due to adsorption. So far, bond analysis has been lacking to ascertain the nature of the attachment using EDC. We recommend that this approach of covalent immobilization of proteins on CNTs be re-evaluated and treated with caution.

Electronically monitoring biological interactions with carbon nanotube field-effect transistors

The year 2008 marks the 10th anniversary of the carbon nanotube field-effect transistor (NTFET). In the past decade a vast amount of effort has been placed on the development of NTFET based sensors for the detection of both chemical and biological species. Towards this end, NTFETs show great promise because of their extreme environmental sensitivity, small size, and ultra-low power requirements. Despite the great progress NTFETs have shown in the field of biological sensing, debate still exists over the mechanistic origins underlying the electronic response of NTFET devices, specifically whether analyte species interact with the carbon nanotube conduction channel or if interaction with the NTFET electrodes actually triggers device response. In this tutorial review, we describe the fabrication of NTFET devices, and detail several reports that illustrate recent advances in biological detection using NTFET devices, while highlighting the suggested mechanisms explaining the device response to analyte species. In doing this we hope to show that NTFET technology has the potential for low-cost and portable bioanalytical platforms.

Application of Nanotechnology in Cancer

Nanotechnology refers broadly to a field of applied science and technology whose unifying theme is the control of matter on the molecular level in scales smaller than 1 micrometer, normally 1 to 100 nanometers, and the fabrication of devices within that size range. In the last five years this technology has been improved tremendously in disease diagnosis and prognosis and maximum research and clinical work has been completed in cancer. The use of various pharmaceutical nanocarriers has become one of the most important areas of nanomedicine. Novel nanotechnologies can complement and augment existing genomic and proteomic techniques to analyze variations across different tumor types, thus offering the potential to distinguish between normal and malignant cells. Sensitive biosensors constructed of nanoscale components ( e.g., nanocantilevers, nanowires, and nanochannels) can recognize genetic and molecular events and have reporting capabilities, thereby offering the potential to detect rare molecular signals associated with malignancy. Such signals may then be collected for analysis by nanoscale harvesters that selectively isolate cancer-related molecules from tissues. The implication of nanotechnology in cancer is discussed in this article with an emphasis on biomarker detection, imaging studies for diagnosis, and its role in therapeutic intervention.

Functionalized carbon nanotubes and nanofibers for biosensing applications

This review summarizes recent advances in electrochemical biosensors based on carbon nanotubes (CNTs) and carbon nanofibers (CNFs) with an emphasis on applications of CNTs. CNTs and CNFs have unique electric, electrocatalytic and mechanical properties, which make them efficient materials for developing electrochemical biosensors.We discuss functionalizing CNTs for biosensors. We review electrochemical biosensors based on CNTs and their various applications (e.g., measurement of small biological molecules and environmental pollutants, detection of DNA, and immunosensing of disease biomarkers). Moreover, we outline the development of electrochemical biosensors based on CNFs and their applications. Finally, we discuss some future applications of CNTs.