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In vivo Glucose sensing with Carbon Nanotubes
In vivo monitoring of the glucose levels, although in market is not efficient. These sensors rely on enzymatic actions. Their performance is limited by their short lives, need for frequent recalibration, invasive characteristics and possible biofouling[1].
Single-Walled Carbon Nanotubes exhibit fluorescence in the near infrared (NIR) region 900 – 1600nm, the optical transparency window of the skin lies within this range (called tissue transparency window). NIR waves have higher tissue penetration depths compared to visible wavelengths. Maximum penetration depth is seen at 100-1400nm which fits in the window of SWCNT fluorescence. Absorption attenuation is also more pronounced at visible wavelengths compared to NIR. SWCNT also resist photobleaching making the sensor long-term systems. The optical methods for glucose monitoring by exploiting the fluorescence of SWCNT offers non-invasive/partially invasive method for glucose monitoring[1].
Semiconducting Single-walled Carbon nanotubes have shown excellent electrocatalysis and fast electron transfer. HiPCO® Single-walled carbon nanotubes have been showcased in the application of glucose sensors by exploiting their sensitivity to H2O2 produced during the enzymatic action of glucose oxidase. The NIR spectroscopy is used as an optical method of measurement in the sensor. The H2O2 can be decomposed into H2O and O2 by increasing the pH[2], [3].
DNA or Polymer wrapped SWCNT have also been showcased for glucose detection. Functionalization with Glucose binding Protein (GBP) has aided in the detection of glucose. The GBP changes conformation upon binding of glucose, increasing fluorescence quenching, which is observed to be proportional to the glucose concentration. Similar studies have been showcased with Boronic Acid (BA) functionalization on nanotubes. Glucose-BA complex formation has shown modulation of SWCNT fluorescence [1], [4].
HiPCO® nanotubes contain a mixture of semiconducting and metallic nanotubes. HiPCO® method produces the smallest diameter SWCNT (0.6-1.2nm). At NoPo, we have perfected this method for industrial scale to ensure the availability of this wonder material to creators across the globe. Being the only current manufacturer of HiPCO®, we aim to be a part of the breakthroughs that will follow by being the provider of the world’s favourite Single-Walled Carbon Nanotubes.
References:
[1] K. Yum, T. P. McNicholas, B. Mu, and M. S. Strano, “Single-Walled Carbon Nanotube-Based Near-Infrared Optical Glucose Sensors toward In Vivo Continuous Glucose Monitoring,” J. Diabetes Sci. Technol., vol. 7, no. 1, pp. 72–87, Jan. 2013.
[2] C. Song, P. E. Pehrsson, and W. Zhao, “Recoverable Solution Reaction of HiPco Carbon Nanotubes with Hydrogen Peroxide,” J. Phys. Chem. B, vol. 109, no. 46, pp. 21634–21639, Nov. 2005.
[3] X. Tu, P. E. Pehrsson, and W. Zhao, “Redox Reaction of DNA-Encased HiPco Carbon Nanotubes with Hydrogen Peroxide: A Near Infrared Optical Sensitivity and Kinetics Study,” J. Phys. Chem. C, vol. 111, no. 46, pp. 17227–17231, Nov. 2007.
[4] Y. Xu, P. E. Pehrsson, L. Chen, R. Zhang, and W. Zhao, “Double-Stranded DNA Single-Walled Carbon Nanotube Hybrids for Optical Hydrogen Peroxide and Glucose Sensing,” J. Phys. Chem. C, vol. 111, no. 24, pp. 8638–8643, Jun. 2007.
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