Probing protein surface interactions in nanoaperture optical tweezers

George, S; Zhao, T; Letwin, K; Truong, VG; Helmi, N; Chormaic, SN; Ying, C; Gordon, R

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Probing protein surface interactions in nanoaperture optical tweezers

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George, S, Zhao, T, Letwin, K, Truong, VG, Helmi, N, Chormaic, SN, Ying, C ORCID: https://orcid.org/0000-0002-7279-1388 and Gordon, R, 2025. Probing protein surface interactions in nanoaperture optical tweezers. Nanotechnology, 36 (47): 475501. ISSN 0957-4484

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Official URL: https://doi.org/10.1088/1361-6528/ae1c48

Abstract

Nanoaperture optical tweezers (NOTs) can trap single proteins using local electromagnetic field enhancements at metal surfaces and therefore they are also subject to surface interactions. To probe these interactions, we consider the power dependence of the trapping stiffness at the limit of zero power, where an attractive or repulsive static force remains. We analyze various proteins with different charge and find that negatively charged proteins are attracted to the gold surface and positively charged proteins are repelled. We interpret this attraction as coming from local positive image charges on the gold adjacent to the negatively charged glass-water interface, as confirmed by finite-element Poisson equation simulations. This work shows a way to quantify the important impact of surface interactions in nanophotonic single molecule sensors of biomolecules and nanoparticles and to gauge their surface charge.

Item Type:	Journal article
Publication Title:	Nanotechnology
Creators:	George, S., Zhao, T., Letwin, K., Truong, V.G., Helmi, N., Chormaic, S.N., Ying, C. and Gordon, R.
Publisher:	IOP Publishing
Date:	24 November 2025
Volume:	36
Number:	47
ISSN:	0957-4484
Identifiers:	Number Type 10.1088/1361-6528/ae1c48 DOI 2538766 Other
Rights:	© 2025 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license (https://creativecommons.org/licenses/by/4.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Borcherds
Date Added:	28 Nov 2025 12:44
Last Modified:	28 Nov 2025 12:44
URI:	https://irep.ntu.ac.uk/id/eprint/54821