Abstract
Introducing sulfhydryl groups to biomolecules to functionalize gold nanorods (GNRs) is an attractive method that involves the creation of a strong Au–S bond. Previously, we developed a facile method to functionalize GNR surfaces by thiolating antibodies using Traut’s reagent. In the current study, we evaluated several methods for the introduction of thiol groups onto the surface of GNRs by using Traut’s reagent, dithiotreitol (DTT), dithiolaromatic PEG6-CONHNH2, and thiol-polyethylene glycolamine (SH-PEG-NH2) combined with EDC reaction. We showed that the four above-mentioned thiolation methods can efficiently functionalize GNRs and simplify the functionalization procedures. The formed GNR-bioconjugates showed superior stability without compromising the biological activity. The GNR nanochip prepared with these four thiolated antibodies can detect human IgG targets with specificity. However, SH-PEG-NH2 combined with EDC reaction may affect the amount of functionalized GNRs because of the efficiency of thiol moiety linkage to antibodies, thereby affecting the sensitivity of the GNR sensor. The introduction of a thiol group to antibodies by using Traut’s reagent, DTT, and PEG6-CONHNH2 allowed for direct immobilization onto the GNR surface, improved the efficacy of functionalized GNRs, and increased the sensitivity in response to target detection as a biosensor. Given that PEG6-CONHNH2 modification requires glycosylated biomolecules, Traut’s reagent and DTT thiolation are recommended as universal applications of GNR biofunctionalization and can be easily extended to other sensing applications based on other gold nanostructures or new biomolecules.
Highlights
Gold nanorods (GNRs) are widely used in biomedicine, including biosensing [1,2,3], photothermal therapy [4,5,6], molecular imaging [7,8], and controlled drug delivery [5,9] because of their distinct optical properties, i.e., high refractive index sensitivity and a tunable longitudinal plasmon band by varying the aspect ratio [10,11]
These methods involved the introduction of sulfhydryl (-SH) groups to anti-human IgG to directly combine with the GNRs in an easy manner
We demonstrated that four thiolation methods to functionalize GNRs can be efficiently achieved by using Traut’s reagent, DTT, PEG6-CONHNH2, and SH-PEGNH2/EDC without compromising the biological activity and specificity
Summary
Gold nanorods (GNRs) are widely used in biomedicine, including biosensing [1,2,3], photothermal therapy [4,5,6], molecular imaging [7,8], and controlled drug delivery [5,9] because of their distinct optical properties, i.e., high refractive index sensitivity and a tunable longitudinal plasmon band by varying the aspect ratio [10,11]. Six nanometers of red shift were observed for the 728 nm GNRs upon binding of thiolated anti-IgG by Traut’s reagent, DTT, and PEG6-CONHNH2 modification. This decrease in red shift may be related to the reduction efficiency of thiol moiety linkage to the antibodies by SH-PEG-NH2 and EDC reaction, thereby reducing the amount of anti-IgG binding to GNR surfaces.
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