Single-walled Carbon Nanotube-based Sensors Research Articles

(Invited) Commercializing Single Walled Carbon Nanotube-Based Sensors - Enzyme Activity and Beyond

The ECS carbon nanostructures community is well informed on the potential of single walled carbon nanotube (SWCNT)-based sensors and likewise the challenges associated with realizing practical applications outside of an academic laboratory. This talk will discuss our latest efforts in facile separation and sensor preparation methods. It will discuss potential use cases in improving high throughput screening of custom enzymes, with a current focus on recalcitrant substrates such as conventional polymers. This talk will also focus on latest efforts of reducing to practice optical fluorimeters (single, multi-channel, spatial, and temperature controlled) for field use applications. Finally, this talk will detail the on-going adventure of commercialization at Zymosense Inc. which we hope will serve as a practical guide to other groups considering transferring their technology from the lab.

Highly Stretchable and Sensitive Single-Walled Carbon Nanotube-Based Sensor Decorated on a Polyether Ester Urethane Substrate by a Low Hydrothermal Process.

We report a highly stretchable sensor with low-concentration (1.5 wt %) single-walled carbon nanotubes (SWCNTs) on flexible polyether ester urethane (PEEU) yarn, fabricated using a low hydrothermal process at 90 °C. Although SWCNTs restrict the PEEU polymer chain mobility, the resulting ductility of our nanocomposites reduces only by 16.5% on average, initially from 667.3% elongation at break to 557.2%. The resulting electrical resistivity of our nanocomposites can be controlled systematically by the number of hydrothermal cycles. A high gauge factor value of 4.84 is achieved at a tensile strain below 100%, and it increases up to 28.5 with applying a tensile strain above 450%. We find that the piezoresistivity of our nanocomposite is sensitive to temperature variations of 25–85 °C due to the hopping effect, which promotes more charge transport at elevated temperatures. Our nanocomposites offer both a high sensitivity and a large strain sensing range, which is achieved with a relatively simple fabrication technique and low concentration of SWCNTs.

Detection of single walled carbon nanotube based sensors in a large mammal

High resolution, rapid, and precise detection of biological analytes related to disease and infection is currently the focus of many researchers. Better biosensors could lead to earlier detection, more avenues of intervention, and higher efficacy of therapeutics, which would lead to better outcomes for all patients. One class of biosensors, single walled carbon nanotubes, is unique due to their nanoscale resolution, single molecule sensitivity, and reversibility for long term applications. While these biosensors have been successful in rodent models, to date, no study has shown successful sensor detection in a large animal. In this study, we show the first successful signal detection of single walled carbon nanotube-based sensors in a large mammal model. Using a relatively simple and cost-effective system, we were able to detect signals in nearly 70% of the sheep used in the study, marking an important steppingstone towards the use of SWNT-based sensors for clinical diagnostics.

Mass transport of lipopolysaccharide induced H2O2 detected by an intracellular carbon nanoelectrode sensor

Hydrogen peroxide is a key component of the innate immune response, regulating how a cell responds to a bacterial threat; however, being transient in nature makes it extremely difficult to detect. We show the development of an improved biosensor capable of the rapid detection of the hydrogen peroxide produced intracellularly in response to both smooth and rough lipopolysaccharides (LPS) structures. The arising signal and mass transport behaviour to the electrodes were characterised. This response was detected utilising a single walled carbon nanotube-based sensor that has been functionalised with an osmium complex for specificity and detecting the change in intracellular concentrations of hydrogen peroxide through chronoamperometry. This was conducted within murine macrophage (RAW264.7) cells and using ultra-pure LPS extracted from two different serotypes of bacteria (0111:B4 and Re495). This allowed the comparison of the immune response when infected with different structures of LPS. We demonstrate that the hydrogen peroxide signal can be electrochemically detected within 3 seconds post injection. Combining the nature of the mass transport of hydrogen peroxide and concentration characteristics, a bacterial ‘fingerprint’ was identified. The impact of this work will be demonstrated in allowing us to develop a rapid diagnostic for bacterial detection.

HIV Detection via a Carbon Nanotube RNA Sensor.

Viral illnesses remain a significant concern in global health. Rapid and quantitative early detection of viral oligonucleotides without the need for purification, amplification, or labeling would be valuable in guiding successful treatment strategies. Single-walled carbon nanotube-based sensors recently demonstrated optical detection of small, free oligonucleotides in biofluids and in vivo, although proteins diminished sensitivity. Here, we discovered an unexpected phenomenon wherein the carbon nanotube optical response to nucleic acids can be enhanced by denatured proteins. Mechanistic studies found that hydrophobic patches of the denatured protein chain interact with the freed nanotube surface after hybridization, resulting in enhanced shifting of the nanotube emission. We employed this mechanism to detect an intact HIV in serum, resulting in specific responses within minutes. This work portends a route toward point-of-care optical detection of viruses or other nucleic acid-based analytes.

Nanoparticle-Templated Molecular Recognition Platforms for Detection of Biological Analytes.

Molecular recognition of biological analytes with optical nanosensors provides both spatial and temporal biochemical information. A recently developed sensing platform exploits near-infrared fluorescent single-wall carbon nanotubes combined with electrostatically pinned heteropolymers to yield a synthetic molecular recognition technique that is maximally transparent through biological matter. This molecular recognition technique is known as corona phase molecular recognition (CoPhMoRe). In CoPhMoRe, the specificity of a folded polymer toward an analyte does not arise from a pre-existing polymer-analyte chemical affinity. Rather, specificity is conferred through conformational changes undergone by a polymer that is pinned to the surface of a nanoparticle in the presence of an analyte and the subsequent modifications in fluorescence readout of the nanoparticles. The protocols in this article describe a novel single-molecule microscopy tool (near-infrared fluorescence and total internal reflection fluorescence [nIRF TIRF] hybrid microscope) to visualize the CoPhMoRe recognition process, enabling a better understanding of synthetic molecular recognition. We describe this requisite microscope for simultaneous single-molecule visualization of optical molecular recognition and signal transduction. We elaborate on the general procedures for synthesizing and identifying single-walled carbon nanotube-based sensors that employ CoPhMoRe via two biologically relevant examples of single-molecule recognition for the hormone estradiol and the neurotransmitter dopamine. © 2016 by John Wiley & Sons, Inc.

DNA-functionalized single-walled carbon nanotube-based sensor array for gas monitoring

Nine deoxyribonucleic acid (DNA) sequences were used to functionalize single-walled carbon nanotube (SWNT) sensors to detect the trace amount of methanol, acetone, and HCl in vapor. DNA 24 Ma (24 randomly arranged nitrogenous bases with one amine at each end of it) decorated SWNT sensor and DNA 24 A (only adenine (A) base with a length of 24) decorated SWNT sensor have demonstrated the largest sensing responses towards acetone and HCl, respectively. On the other hand, for the DNA GT decorated SWNT sensors with different sequence lengths, the optimum DNA sequence length for acetone and HCl sensing is 32 and 8, separately. The detection of methanol, acetone, and HCl have identified that DNA functionalized SWNT sensors exhibit great selectivity, sensitivity, and repeatability with an accuracy of more than 90%. Further, a sensor array composed of SWNT functionalized with various DNA sequences was utilized to identify acetone and HCl through pattern recognition. The sensor array is a combination of four different DNA functionalized SWNT sensors and two bare SWNT sensors (work as reference). This wireless sensing system has enabled real-time gas monitoring and air quality assurance for safety and security.

Control of nano and microchemical systems

Many advances in the development of nano and microchemical systems have occurred in the last decade. These systems have significant associated identification and control challenges, including high state dimensionality, limitations in real-time measurements and manipulated variables, and significant uncertainties described by non-Gaussian distributions. Some strategies for addressing these challenges are summarized, which include exploiting structure within the stochastic Master equations that describe molecular interactions, manipulating molecular bonds at system boundaries, and manipulating molecules and nanoscale objects through magnetic and electric fields. The strategies are illustrated in a variety of applications that include the estimation of nucleation kinetics of protein and pharmaceutical crystals within fluidic devices, the estimation of concentration fields using DNA-wrapped single-walled carbon nanotube-based sensor arrays, the simultaneous control of nanoscale geometry and electrical activation during thermal annealing in a semiconductor material, and the control of nanostructure formation on surfaces. Promising directions for research and technology development are identified for the next decade.

Atomistic Modeling of Carbon Nanotube-based Mechanical Sensors

This article provides an overview of our recent studies on single-walled carbon nanotube-based sensors for measuring mass, strain, pressure, and temperature at the nanoscale. The carbon nanotube in a cantilevered or bridged configuration is simulated by an atomistic modeling, the molecular structural mechanics method. The principle of sensing is based on the resonant frequency shift of a carbon nanotube resonator when it is subjected to changes in attached mass, external loading, or temperature. The results indicate that a logarithmically linear relationship exists between the resonant frequency and the attached mass when the mass is larger than 10 20 g. The resonant frequency shifts are shown to be linearly dependent on the applied axial strain and the applied pressure, and approximate linearity exists between the resonant frequency shift and temperature. The sensing capability of carbon nanotube-based sensors far exceeds that of current microsensors and the sensitivities can be enhanced with the use of small size carbon nanotubes.

Strain and pressure sensing using single-walled carbon nanotubes

In this study, single-walled carbon nanotube-based sensors are proposed for measuringstrain and pressure at the nanoscale. The principle of sensing is based on the resonantfrequency shift of a carbon nanotube resonator when it is subjected to a strain resultingfrom external loading. The carbon nanotube in a bridged configuration is simulated byatomistic modelling, the molecular structural mechanics method. The resonant frequencyshifts are shown to be linearly dependent on the applied axial strain and the appliedpressure. The sensitivities of nanotube-based sensors are enhanced with the reduction oftube length and tube diameter, respectively, for axial strain and pressure sensing.