Four-wave-mixing microscopy reveals non-colocalisation between gold nanoparticles and fluorophore conjugates inside cells

Jones, Arwyn T.; Giannakopoulou, Naya; Borri, Paola; Williams, Joseph B.; Watson, Peter; Moody, Paul R.; Langbein, Wolfgang; Sayers, Edward J.; Alexander, Cameron; Magnusson, Johannes P.; Payne, Lukas; Pope, Iestyn

Abstract

Gold nanoparticles have been researched for many biomedical applications in diagnostics, theranostics, and as drug delivery systems. When conjugated to fluorophores, their interaction with biological cells can be studied in situ and real time using fluorescence microscopy. However, an important question that has remained elusive to answer is whether the fluorophore is a faithful reporter of the nanoparticle location. Here, our recently developed four-wave-mixing optical microscopy is applied to image individual gold nanoparticles and in turn investigate their co-localisation with fluorophores inside cells. Nanoparticles from 10 nm to 40 nm diameter were conjugated to fluorescently-labeled transferrin, for internalisation via clathrin-mediated endocytosis, or to non-targeting fluorescently-labelled antibodies. Human (HeLa) and murine (3T3-L1) cells were imaged at different time points after incubation with these conjugates. Our technique identified that, in most cases, fluorescence originated from unbound fluorophores rather than from fluorophores attached to nanoparticles. Fluorescence detection was also severely limited by photobleaching, quenching and autofluorescence background. Notably, correlative extinction/fluorescence microscopy of individual particles on a glass surface indicated that commercial constructs contain large amounts of unbound fluorophores. These findings highlight the potential problems of data interpretation when reliance is solely placed on the detection of fluorescence within the cell, and are of significant importance in the context of correlative light electron microscopy.

Citation

Jones, A. T., Giannakopoulou, N., Borri, P., Williams, J. B., Watson, P., Moody, P. R., …Pope, I. (2020). Four-wave-mixing microscopy reveals non-colocalisation between gold nanoparticles and fluorophore conjugates inside cells. Nanoscale, 12(7), 4622-4635. https://doi.org/10.1039/c9nr08512b

• Journal Article Type: Article
• Acceptance Date: Dec 21, 2019
• Online Publication Date: Feb 11, 2020
• Publication Date: Feb 21, 2020
• Deposit Date: Feb 12, 2020
• Publicly Available Date: Feb 12, 2020
• Journal: Nanoscale
• Print ISSN: 2040-3364
• Electronic ISSN: 2040-3372
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 12
• Issue: 7
• Pages: 4622-4635
• DOI: https://doi.org/10.1039/c9nr08512b
• Keywords: General Materials Science
• Public URL: https://nottingham-repository.worktribe.com/output/3949612
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2020/NR/C9NR08512B
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Edward J. Sayers (ORCID); : Edward J. Sayers (ResearcherID); : Iestyn Pope (ORCID); : Cameron Alexander (ORCID); : Cameron Alexander (ResearcherID); : Arwyn T. Jones (ORCID); : Arwyn T. Jones (ResearcherID); : Wolfgang Langbein (ResearcherID); : Paola Borri (ORCID); : Single-blind; : Received 3 October 2019; Accepted 21 December 2019; Advance Article published 11 February 2020