arXiv subjects

Thomas S. van Zanten

Publications and source records attributed to Thomas S. van Zanten.

3 recordsLinked to original sources

arXiv2026

The Hidden Cost of Two-Dimensional TEM Reconstruction of Magnetic Nanoparticle Morphology

Conventional transmission electron microscopy (TEM) records two-dimensional (2D) projections of three-dimensional (3D) objects, complicating the inference of nanoparticle morphology. This limitation is investigated for quasi-spherical iron oxide nanoparticles (IONPs) imaged after deposition on a TEM grid and after cellular internalization and immobilization in resin. A statistical inverse-reconstruction method is developed in which synthetic 3D particle populations are randomly oriented, projected onto a TEM-like plane, and compared with the experimental equivalent-diameter and axial-ratio distributions. Models of increasing geometrical complexity are considered, from monodisperse prolate spheroids to size- and shape-polydisperse prolate populations and triaxial ellipsoids. Size polydispersity is required to reproduce the projected equivalent-diameter distribution, whereas relaxing axial symmetry through a triaxial description enables simultaneous reproduction of the size and axial-ratio distributions. The inferred population represents a statistically compatible 3D morphology rather than a unique particle-by-particle reconstruction. Its physical relevance is assessed through a macrospin model incorporating the corresponding shape-anisotropy contributions. Application to magnetic fluid hyperthermia reveals a pronounced sensitivity of the predicted heating response to particle geometry and polydispersity. The approach provides a general framework for connecting conventional TEM measurements with morphology-dependent properties of nanoparticle ensembles.

cond-mat.mtrl-sci↗

arXiv2023

Broadband plasmonic nanoantennas for multi-color nanoscale dynamics in living cells

Recently, the implementation of plasmonic nanoantennas has opened new possibilities to investigate the nanoscale dynamics of individual biomolecules in living cell. However, studies have yet been restricted to single molecular species as the narrow wavelength resonance of gold-based nanostructures precludes the simultaneous interrogation of different fluorescently labeled molecules. Here we exploited broadband aluminum-based nanoantennas carved at the apex of near-field probes to resolve nanoscale-dynamic molecular interactions on intact living cell membranes. Through multicolor excitation, we simultaneously recorded fluorescence fluctuations of dual-color labeled transmembrane receptors known to form nanoclusters in living cells. Fluorescence cross-correlation studies revealed transient interactions between individual receptors in regions of ~60 nm. Moreover, the high signal-to-background ratio provided by the antenna illumination allowed us to directly detect fluorescent bursts arising from the passage of individual receptors underneath the antenna. Remarkably, by reducing the illumination volume below the characteristic receptor nanocluster sizes, we resolved molecular diffusion within nanoclusters and distinguished it from nanocluster diffusion. Spatiotemporal characterization of transient interactions between molecules is crucial to understand how they communicate with each other to regulate cell function. Our work demonstrates the potential of broadband photonic antennas to study multi-molecular events and interactions in living cell membranes with unprecedented spatiotemporal resolution.

physics.optics↗

arXiv2022

Multiplexed plasmonic nanoantennas for high throughput single molecule nanoscale dynamics in living cells

Single molecule detection has revolutionised the fields of chemistry and biology by offering powerful ways to study individual molecules under different scenarios. Nanophotonic structures, including plasmonic antennas, significantly overcome the concentration limit at which single molecule events can be observed, enabling their detection at concentrations that are relevant to biological and chemical processes. Although antennas can be fabricated in large arrays, probing dynamic events requires high temporal resolution, which is best achieved by serial antenna interrogation. Unfortunately, this precludes the simultaneous recording from multiple antennas at different sample locations, and is time consuming, resulting in poor statistics and low-throughput data acquisition, abating the true potential of arrays. Here we exploit arrays of antenna-in-box nanostructures in combination with sCMOS readout to interrogate nanoscale volumes from 225 antennas simultaneously. Recording at 1 kHz allowed multiplexed dynamic measurements from 50 nanoantennas simultaneously with a temporal resolution dictated by the camera framerate and the photons emitted per molecule during a single passage. We demonstrate the capability for high-throughput arrayed detection of single molecule dynamics at the nanoscale in the membrane of living cells, and determine the axial location of membrane molecular components with 1 nm accuracy and temporal resolution below 1 ms.

physics.bio-ph↗