Issue 6, 2020

Dynamic single-molecule counting for the quantification and optimization of nanoparticle functionalization protocols

Abstract

Applications of colloidal particles in the fields of i.e. biosensors, molecular targeting, or drug-delivery require their functionalization with biologically active and specific molecular ligands. Functionalization protocols often result in a heterogeneous population of particles with a varying density, spatial distribution and orientation of the functional groups on the particle surface. A lack of methods to directly resolve these molecular properties of the particle's surface hampers optimization of functionalization protocols and applications. Here quantitative single-molecule interaction kinetics is used to count the number of ligands on the surface of hundreds of individual nanoparticles simultaneously. By analyzing the waiting-time between single-molecule binding events we quantify the particle functionalization both accurately and precisely for a large range of ligand densities. We observe significant particle-to-particle differences in functionalization which are dominated by the particle-size distribution for high molecular densities, but are substantially broadened for sparsely functionalized particles. From time-dependent studies we find that ligand reorganization on long timescales drastically reduces this heterogeneity, a process that has remained hidden up to now in ensemble-averaged studies. The quantitative single-molecule counting therefore provides a direct route to quantification and optimization of coupling protocols towards molecularly controlled colloidal interfaces.

Graphical abstract: Dynamic single-molecule counting for the quantification and optimization of nanoparticle functionalization protocols

Supplementary files

Article information

Article type
Paper
Submitted
02 Dec 2019
Accepted
28 Jan 2020
First published
28 Jan 2020
This article is Open Access
Creative Commons BY-NC license

Nanoscale, 2020,12, 4128-4136

Dynamic single-molecule counting for the quantification and optimization of nanoparticle functionalization protocols

M. Horáček, D. J. Engels and P. Zijlstra, Nanoscale, 2020, 12, 4128 DOI: 10.1039/C9NR10218C

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