Silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biocompatible contrast agent in biomedical photoacoustics

Rudolf Alwi,Sulayman Oladepo,Andreas Mandelis,Sergey Telenkov,Frank Gu,Kirk Michaelian,Timothy Leshuk

doi:10.1364/boe.3.002500

Abstract

In this study, we report for the first time the use of silica-coated superparamagnetic iron oxide nanoparticles (SPION) as contrast agents in biomedical photoacoustic imaging. Using frequency-domain photoacoustic correlation (the photoacoustic radar), we investigated the effects of nanoparticle size, concentration and biological media (e.g. serum, sheep blood) on the photoacoustic response in turbid media. Maximum detection depth and the minimum measurable SPION concentration were determined experimentally. The nanoparticle-induced optical contrast ex vivo in dense muscular tissues (avian pectus and murine quadricept) was evaluated and the strong potential of silica-coated SPION as a possible photoacoustic contrast agents was demonstrated.

Highlights

There has been a significant increase in the use of contrast agents in photoacoustic imaging [1,2,3,4,5,6,7,8,9,10,11,12,13]
We conducted five types of experiments to evaluate the effectiveness of silica-coated Superparamagnetic iron oxide nanoparticles (SPION) as a PA contrast agent: 1) we measured the maximum detectable depth of a known silica-coated SPION concentration inside a tissue mimicking Intralipid solution; 2) we investigated the effect of nanoparticle size variation on the generated PA response; 3) we examined whether the silica-coated SPION were optically stable in organic solvents; 4) we quantified the minimum resolvable concentration of silica-coated SPION at fixed depths inside a tissue mimicking Intralipid solution; and 5) we tested the detectability of silica-coated SPION inside chicken breast tissue and rat thigh muscle ex vivo
Near-IR FTIR-PA spectroscopy results [Fig. 1(c)] of silica nanoparticles (SiO2; LUDOX), bare SPION (8 nm Fe3O4 core), and silica-coated SPION (8 nm Fe3O4 core, 3 nm SiO2 coating), show approximately 1.6-fold increase in PA signal magnitude generated by silicacoated SPION compared to bare SPION spectra under 1064-nm wavelength excitation

Summary

Introduction

There has been a significant increase in the use of contrast agents in photoacoustic imaging [1,2,3,4,5,6,7,8,9,10,11,12,13]. A gold nanoparticle has a superior optical absorption profile attributed to its strong plasmon resonance peaks in the near-IR [15]. Thakor et al [18] in their recent review article on the use of gold nanoparticles in a clinical setting stated that, inevitably, trade-offs will have to be made regarding some of their diagnostic and therapeutic properties vis-a-vis their associated toxicity profile

Objectives

Results

Conclusion