Plasmonic Copper Sulfide Nanoparticles Enable Dark Contrast in Optical Coherence Tomography

Zhiming Wang,Fernando Rivero,Alexander O Govorov,Daniel Jaque,José Lifante,Lucas V Besteiro,Fernando Alfonso,Francisco Sanz‐Rodríguez,Riccardo Marin

doi:10.1002/adhm.201901627

Abstract

Optical coherence tomography (OCT) is an imaging technique affording noninvasive optical biopsies. Like for other imaging techniques, the use of dedicated contrast agents helps better discerning biological features of interest during the clinical practice. Although bright OCT contrast agents have been developed, no dark counterpart has been proposed yet. Herein, plasmonic copper sulfide nanoparticles as the first OCT dark contrast agents working in the second optical transparency window are reported. These nanoparticles virtually possess no light scattering capabilities at the OCT working wavelength (≈1300 nm); thus, they exclusively absorb the probing light, which in turn results in dark contrast. The small size of the nanoparticles and the absence of apparent cytotoxicity support the amenability of this system to biomedical applications. Importantly, in the pursuit of systems apt to yield OCT dark contrast, a library of copper sulfide nanoparticles featuring plasmonic resonances spanning the three optical transparency windows is prepared, thus highlighting the versatility and potential of these systems in light-controlled biomedical applications.

Highlights

Sometimes, the most valuable gifts are those we cannot see with our eyes
In the quest for copper sulfide NPs with a plasmonic resonance centered at the working wavelength of the optical coherence tomography (OCT) instruments used in this study (1300 and 1320 nm), two different approaches were pursued: i) thermolysis of copper complexes in high-boiling-point solvents followed by transfer to aqueous media and ii) direct synthesis in water
From this pre-screening of the reaction conditions, we identified copper sulfide NPs obtained from the thermolysis of Cu(tba)2 at 200 °C (Figure 1) as the most promising candidates for advancing our study, owing to a good homogeneous size distribution, small size and NIR-IIcentered localized surface plasmon resonance (LSPR) band

Summary

Introduction

The most valuable gifts are those we cannot see with our eyes. As philosophical as it might sound, this sentence well embodies the spirit of the latest research in the field of optical biomedical techniques. We report plasmonic copper sulfide nanoparticles as the first OCT dark contrast agents working in the second optical transparency window.

Results

Conclusion