Guanine quantum defects in carbon nanotubes for biosensing

09 February 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

Carbon nanotubes
fluorescence
near infrared biosensing
quantum defects
DNA
dopamine

Supplementary materials

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Description
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Title
Supporting information for Guanine quantum defects in carbon nanotubes for biosensing
Description
Additional fluorescence spectra and plots for surface-DNA quantification, selectivity and stability experiments.
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