Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Oct 11;10(10):230825.
doi: 10.1098/rsos.230825. eCollection 2023 Oct.

Feasibility of NAD(P)/NAD(P)H as redox agents in enzymatic plasmonic gold nanostar assays for galactose quantification

Tozivepi Aaron Munyayi  1 , Danielle Wingrove Mulder  1 , Engela Helena Conradie  1 , Barend Christiaan Vorster  1
Affiliations

Feasibility of NAD(P)/NAD(P)H as redox agents in enzymatic plasmonic gold nanostar assays for galactose quantification

Tozivepi Aaron Munyayi et al. R Soc Open Sci. .

Abstract

Plasmonic colorimetric sensors have emerged as powerful analytical tools in biochemistry due to their localized surface plasmon resonance extinction in the visible range. Here, we describe the feasibility of NAD(P)/NAD(P)H as redox agents in enzymatic plasmonic gold nanostar (AuNS) assays for galactose quantification using three model enzymes, GalDH, AR and GalOx, immobilized separately on polyvinylpyrrolidone-capped AuNS scaffolds. These highly specific, sensitive and selective bioassays induce the transformation of AuNS into quasi-spherical nanoparticles during the biorecognition of galactose in water and synthetic blood matrices. As a result, using our inexpensive and simple AuNS plasmon bioassays, the presence of galactose may be detected spectrophotometrically and by the naked eye.

Keywords: bioassay; biorecognition; biosensor; gold nanostars; immobilized; redox agents.

PubMed Disclaimer

Conflict of interest statement

We have no competing interests to declare.

Figures

Figure 1.
Figure 1.
EDS spectra, SEM-EDS elemental mapping profiles, and HR-TEM images for AuNS. (a,c,e) Uncapped AuNS; (b,d,f) PVP-capped AuNS.
Figure 2.
Figure 2.
UV–visible spectra profiles, 1H-NMR spectra profiles, electrophoretic profiles and HR-TEM images for AuNS bioconjugates. (a–d) AuNS-PVP-GalDH, (e–h) AuNS-PVP-AR, (i–l) AuNS-PVP-GalOx.
Figure 3.
Figure 3.
UV–visible spectra of AuNS bioconjugate stability after 3 h incubation in (a) blank urine; (b) serum; (c) supplemented cell culture medium. Short-term storage stability UV–visible spectra at room temperature and 4°C in water matrix: (d,g) AuNS-PVP-GalDH, (e,h) AuNS-PVP-AR, (f,i) AuNS-PVP-GalOx.
Figure 4.
Figure 4.
Preliminary colorimetric UV–visible profiles for AuNS-PVP in the presence of (a) NAD+, (b) NADPH and (c) H2O2.
Figure 5.
Figure 5.
AuNS bioconjugate colorimetric spectra in water and synthetic blood with increasing galactose: (a,d) AuNS-PVP-GalDH, (b,e) AuNS-PVP-AR, (c,f) AuNS-PVP-GalOx.
Figure 6.
Figure 6.
AuNS bioconjugate TEM images before and after colorimetric reactions in the water matrix.
Figure 7.
Figure 7.
AuNS bioassay analyte specificity test. Glucose was used in place of galactose. (a,d) AuNS-PVP-GalDH, (b,e) AuNS-PVP-AR, (c,f) AuNS-PVP-GalOx.
See this image and copyright information in PMC

Similar articles

See all similar articles

References

    1. Broderick JB. 2001. Coenzymes and cofactors. Encyclopedia of Life Sciences 1, 1-11. (10.1038/npg.els.0000631) - DOI
    1. Rucker RB, Chowanadisai W. 2016. Coenzymes and cofactors. In Encyclopedia of food and health (eds Finglas CB, Toldrá Fidel PM), pp. 206-224. Oxford, UK: Academic Press.10.1016/b978-0-12-384947-2.00181-1) - DOI
    1. Gopalan A, Ragupathy D, Kim H-T, Manesh KM, Lee K-P. 2009. Pd (core)-Au (shell) nanoparticles catalyzed conversion of NADH to NAD+ by UV-vis spectroscopy—a kinetic analysis. Spectrochim. Acta A Mol. Biomol. Spectrosc. 74, 678-684. (10.1016/j.saa.2009.07.022) - DOI - PubMed
    1. Wilmot CM, Phillips SEV. 1997. Structure of oxidoreductase. Protein Data Bank. (10.2210/pdb1spu/pdb) - DOI
    1. Patterson GH, Knobel SM, Arkhammar P, Thastrup O, Piston DW. 2000. Separation of the glucose-stimulated cytoplasmic and mitochondrial NAD(P)H responses in pancreatic islet beta cells. Proc. Natl Acad. Sci. USA 97, 5203-5207. (10.1073/pnas.090098797) - DOI - PMC - PubMed