Fluorescent single-wall carbon nanotubes (SWCNTs) are used as nanoscale biosensors in diverse applications. Selectivity is built in by noncovalent functionalization with polymers such as DNA. Recently, covalent functionalization was demonstrated by conjugating guanine bases of adsorbed DNA to the SWCNT surface as guanine quantum defects (g-defects). Here, we create g-defects in (GT)10-coated SWCNTs (Gd-SWCNTs) and explore how this affects molecular sensing. We vary the defect densities, which shifts the E 11 fluorescence emission by 55 nm to a λmax of 1049 nm. Furthermore, the Stokes shift between absorption and emission maximum linearly increases with defect density by up to 27 nm. Gd-SWCNTs represent sensitive sensors and increase their fluorescence by >70% in response to the important neurotransmitter dopamine and decrease it by 93% in response to riboflavin. Additionally, the extent of cellular uptake of Gd-SWCNTs decreases. These results show how physiochemical properties change with g-defects and that Gd-SWCNTs constitute a versatile optical biosensor platform.
Fluorescent single wall carbon nanotubes (SWCNTs) are used as nanoscale biosensors in diverse applications. Selectivity is built in by non-covalent functionalization with polymers such as DNA. In general, fluorescence sensing with SWCNTs would benefit from covalent DNA-conjugation but it is not known how changes in conformational flexibility and photophysics affect the sensing mechanism. Recently, covalent functionalization was demonstrated by conjugating guanine bases of adsorbed DNA to the SWCNT surface as guanine quantum defects (g-defects). Here, we create guanine defects in (GT)10 coated SWCNTs (Gd-SWCNTs) and explore how this affects molecular sensing. We vary the defect densities, which shifts the E11 fluorescence emission by 55 nm to max = 1049 nm for the highest defect density. Furthermore, the difference between absorption maximum and emission maximum (Stokes shift) increases with increasing defect density by 0.87 nm per nm of absorption shift and up to 27 nm in total. Gd-SWCNTs represent sensitive sensors and increase their fluorescence >70 % in response to the important neurotransmitter dopamine and decrease 93 % in response to riboflavin. Additionally, cellular uptake of Gd-SWCNTs decreases. These results show how physiochemical properties alter with guanine defects and that Gd-SWCNTs constitute a versatile optical biosensor platform.
Um Signalmoleküle zu beobachten, sind Methoden mit hoher zeitlicher und räumlicher Auflösung erforderlich. Als Bausteine für Sensoren eignen sich Kohlenstoffnanoröhren, die im nahen Infrarot fluoreszieren. Auf Gehirnzellen aufgebracht zeigen sie, wo und wann der Neurotransmitter Dopamin frei wird.
The molecules released by cells are a fingerprint of their current state. Methods that measure them with high spatial and temporal resolution would provide valuable insights into cell physiology and diseases. Here, we develop a nanosensor coating that transforms standard cell culture materials/dishes into “Smart Slides” capable of optically monitoring biochemical efflux from cells. For this purpose, we use single wall carbon nanotubes (SWCNTs) that are fluorescent in the beneficial near-infrared (NIR, 850 – 1700 nm) window. They are chemically tailored to detect the neurotransmitter dopamine by a change in fluorescence intensity. These nanosensors are spin-coated on glass substrates and we show that such sensor layers can be sterilized by UV light and can be stored in dry condition or buffer for at least 6 weeks. We also identify the optimal sensor density to maximize sensitivity. Finally, we use these materials to image dopamine release from neuronal cells cultivated on top in the presence of various psychotropic substances, which represents a system to test pharmaceuticals for neurological or neurodegenerative diseases. Therefore, Smart Slides are a powerful tool to monitor cellular processes in cell culture systems.
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