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.

Single-Walled Carbon Nanotube Sensor Platform for the Study of Extracellular Analytes.

Single-walled carbon nanotubes (SWNT) are attractive targets for the formation of high-density sensor arrays. Their small size and high reactivity could allow for the spatial and temporal study of extracellular products to a degree which greatly surpasses contemporary sensors. However, current methods of SWNT immobilization produce a low fluorescence yield that requires a combination of high magnification, exposure time, and laser intensity to combat, thus limiting the sensor's applications. In this work, a platform for the immobilization of SWNT sensors with increased fluorescence yield, longevity, fluorescence distribution, and fast reaction times is developed.

Novel methods to extract and quantify sensors based on single wall carbon nanotube fluorescence from animal tissue and hydrogel-based platforms.

Sensors that can quickly and accurately diagnose and monitor human health are currently at the forefront of medical research. Single walled carbon nanotube (SWNT) based optical biosensors are a growing area of research due to the high spatiotemporal resolution of their near infrared fluorescence leading to high tissue transparency and unparalleled sensitivity to analytes of interest. Unfortunately, due to the functionalization requirements of SWNT-based sensors, there are concerns surrounding accumulation and persistence when applied in vivo. In this study, we developed protocols to extract and quantify SWNT from complex solutions and show an 89% sensor retention by hydrogel platforms when implanted in vivo. Animal tissues of interest were also extracted and probed for SWNT content showing no accumulation (0.03 mg l-1 SWNT detection limit). The methods developed in this paper demonstrated one avenue for applying SWNT sensors in vivo without concern for accumulation.

Quantification of Nitric Oxide Concentration Using Single-Walled Carbon Nanotube Sensors.

Nitric oxide (NO), a free radical present in biological systems, can have many detrimental effects on the body, from inflammation to cancer. Due to NO's short half-life, detection and quantification is difficult. The inability to quantify NO has hindered researchers' understanding of its impact in healthy and diseased conditions. Single-walled carbon nanotubes (SWNTs), when wrapped in a specific single-stranded DNA chain, becomes selective to NO, creating a fluorescence sensor. Unfortunately, the correlation between NO concentration and the SWNT's fluorescence intensity has been difficult to determine due to an inability to immobilize the sensor without altering its properties. Through the use of a recently developed sensor platform, systematic studies can now be conducted to determine the correlation between SWNT fluorescence and NO concentration. This paper explains the methods used to determine the equations that can be used to convert SWNT fluorescence into NO concentration. Through the use of the equations developed in this paper, an easy method for NO quantification is provided. The methods outlined in this paper will also enable researchers to develop equations to determine the concentration of other reactive species through the use of SWNT sensors.

Implantable Nanotube Sensor Platform for Rapid Analyte Detection.

The use of nanoparticles within living systems is a growing field, but the long-term effects of introducing nanoparticles to a biological system are unknown. If nanoparticles remain localized after in vivo implantation unanticipated side effects due to unknown biodistribution can be avoided. Unfortunately, stabilization and retention of nanoparticles frequently alters their function.[1] In this work multiple hydrogel platforms are developed to look at long-term localization of nanoparticle sensors with the goal of developing a sensor platform that will stabilize and localize the nanoparticles without altering their function. Two different hydrogel platforms are presented, one with a liquid core of sensors and another with sensors decorating the hydrogel's exterior, that are capable of localizing the nanoparticles without inhibiting their function. With the use of these new hydrogel platforms nanoparticle sensors can be easily implanted in vivo and utilized without concerns of nanoparticle impact on the animal.