Gold Nanoparticle-decorated Carbon Nanotubes Research Articles

Nanostructured electrochemical immunosensor for detection of serological alkaline phosphatase

Alkaline phosphatase (ALP) is an enzyme that plays an important role in bone mineralization and skeletal growth. Variations in physiological levels of ALP have been correlated to diseases such as osteomalacia, Paget's disease and arterial calcifications. In this context, the integration of carbon nanotubes (CNT) within osteointegration implants has shown to increase ALP's mineralization activity in virtue of their surface chemistry and their morphological resemblance to collagen nanofibers. In this study we present the development and analytical application of an impedimetric immunosensor based in gold nanoparticle-decorated CNT, which characteristics are desirable in implantable biosensors. The device effectively detects ALP within blood serum, a complex biological fluid where most expressed proteins can be found. Robustness and high sensitivity were attained by immobilizing covalently anti-ALP antibody as a specific probe towards ALP. Cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy were used to characterize the sensor system throughout mounting steps and real sample testing. Impedimetric responses were adjusted to a theoretical electrical circuit and charge transfer resistance showed to be an adequate parameter to evaluate the biorecognition process of the analyte. Additionally, amperometrical current variation and changes in topography found over the surface after positive samples evidenced biorecognition. The final biosensor showed excellent performance with two linear ranges from 0.5 to 50 IU.L-1 and from 100 to 600 IU.L-1; limits of detection were calculated as 0.25 and 84.6 IU.L-1 respectively with a relative standard deviation lower than 5%. The device was found to be selective, avoiding protein c, a potential interferer occurring during inflammatory processes. The proposed strategy is promising for osteogenic applications where it can improve osteointegration implants by monitoring ALP activity.

A molecularly imprinted electrochemical enzymeless sensor based on functionalized gold nanoparticle decorated carbon nanotubes for methyl-parathion detection

Schematic of MP MIP sensor and the possible mechanism.

Highly sensitive, transparent, and flexible gas sensors based on gold nanoparticle decorated carbon nanotubes

We report on a high performance flexible and transparent chemical sensor based on functionalised single-walled carbon nanotubes (SWCNTs). The SWCNT films were spray-deposited on transparent and flexible plastic substrates, and subsequently decorated with Au nanoparticles (AuNPs) providing a facile and cheap fabrication route. The electrical resistance of the films changed remarkably upon exposure to ammonia (NH3), AuNP decoration enhanced sensitivity to 255ppb (parts-per-billion), one of the lowest reported so far. The reported sensor performance is a huge improvement towards low power consumption and its room temperature operation augers well for use in mobile devices for environmental protection and air quality control.

Carbon Nanotube‐Tipped Endoscope for In Situ Intracellular Surface‐Enhanced Raman Spectroscopy

Gold nanoparticle-decorated carbon nanotubes (CNTs) are used to study intracellular environments in situ using surface-enhanced Raman spectroscopy (SERS). CNTs are decorated with gold nanoparticles and assembled onto the tips of pulled glass capillaries to form a SERS-enabled endoscope. The sub-micrometer size and high mechanical strength of the endoscope make it possible to penetrate the cell membrane for intracellular probing and remain positioned inside during lengthy SERS measurements without causing damage to the cell. Using the SERS-enabled endoscope, DNA and other biomolecules are detected in situ within the nucleus of a single human cervical carcinoma cell in a minimally invasive manner. The SERS-enabled endoscopes exhibit high selectivity and sensitivity for detecting trace amounts of analytes (≈1 pM) in biofluid environments, highlighting their capabilities as label-free, biological sensors for real-time in situ cellular diagnostics, biological detection, and pharmaceutical research.