Phase-resolved magnetomotive OCT for imaging nanomolar concentrations of magnetic nanoparticles in tissues

Amy L Oldenburg,Vasilica Crecea,Stephen A Boppart,Stephanie A Rinne

doi:10.1364/oe.16.011525

Amy L Oldenburg, Vasilica Crecea + Show 2 more

Open Access

https://doi.org/10.1364/oe.16.011525

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Journal: Optics Express	Publication Date: Jul 18, 2008
Citations: 116	License type: cc-by

Affiliation: University of Illinois Urbana-Champaign

Abstract

Magnetic nanoparticles (MNPs) are increasingly important in magnetic resonance and biomedical optical imaging. We describe a method for imaging MNPs by detecting nanoscale displacements using a phase-resolved spectral-domain optical coherence tomography (OCT) system. Biological tissues and phantoms are exposed to approximately 800 G magnetic fields modulated at 56 and 100 Hz to mechanically actuate embedded iron oxide MNPs (approximately 20 nm diameter). Sensitivity to 27 microg/g (approximately 2 nM) MNPs within tissue phantoms is achieved by filtering paramagnetic from diamagnetic vibrations. We demonstrate biological feasibility by imaging topically applied MNPs during their diffusion into an excised rat tumor over a 2 hour time period.

Highlights

Magnetic nanoparticles (MNPs) composed of biocompatible iron oxides exhibit magnetic susceptibilities χ that are typically >105 times larger than that of human tissue, including red blood cells [1,2]
Magnetomotive OCT (MMOCT) imaging was performed on silicone phantoms with tissue-like optical and mechanical properties to understand the sensitivity to small MNP doses
MMOCT imaging provides a new way of tracking MNPs on the microscale

Summary

Introduction

Magnetic nanoparticles (MNPs) composed of biocompatible iron oxides (magnetite, Fe3O4, or maghemite, γ-Fe2O3) exhibit magnetic susceptibilities χ that are typically >105 times larger than that of human tissue, including red blood cells [1,2]. Not surprisingly, this fact has led to the increasing development of MNP-related technologies in biology and medicine [3]. Heating of MNPs with high frequency magnetic fields is being investigated as a possible cancer treatment by inducing hyperthermia in tumors [4]. The availability of new imaging techniques appropriate to the microscale such as optical coherence tomography (OCT) can elucidate processes such as diffusion, active transport processes, and in general, biodistribution and kinetics, which may be currently limiting our ability to target MNPs [3]

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