High resolution fluorescence bio-imaging upconversion nanoparticles in insects.

Masfer Alkahtani,Philip R Hemmer,Yunyun Chen,Hong Liang,Dilworth Y Parkinson,Julie J Pedraza,Jorge M González

doi:10.1364/oe.25.001030

Abstract

Imaging fluorescent markers with brightness, photostability, and continuous emission with auto fluorescence background suppression in biological samples has always been challenging due to limitations of available and economical techniques. Here we report a new approach, to achieve high contrast imaging inside small and difficult biological systems with special geometry such as fire ants, an important agricultural pest, using a homemade cost-effective optical system. Unlike the commonly used rare-earth doped fluoride nanoparticles, we utilized nanoparticles with a high upconversion efficiency in water. Specifically Y2O3:Er+3,Yb+3 nanoparticles (40-50 nm diameter) were fed to fire ants as food and then a simple illuminating experiment was conducted at 980 nm wavelength at relatively low pump intensity8kW.cm-2. The locations were further confirmed by X-ray tomography, where most particles aggregated inside the ant's mouth. High resolution, fast, and economical optical imaging system opens the door for studying more complex biological systems.

Highlights

Over the past decades, intensive efforts have been focused to develop effective nanoparticles like fluorescent markers in biological imaging [1,2,3]
Most of the traditional fluorescent markers such as organic dyes and quantum dots exhibit high luminesce efficiency within the visible range when stimulated by high-energy lasers excitation
Their high-energy illumination causes the surrounding biological samples to emit light in the visible window, resulting in a significant auto-fluorescence which will reduces the sensitivity of using these fluorescent markers in deep tissue imaging [4, 5]

Summary

Introduction

Intensive efforts have been focused to develop effective nanoparticles like fluorescent markers in biological imaging [1,2,3]. Most of the traditional fluorescent markers such as organic dyes and quantum dots exhibit high luminesce efficiency within the visible range when stimulated by high-energy lasers excitation. Their high-energy illumination causes the surrounding biological samples to emit light in the visible window, resulting in a significant auto-fluorescence which will reduces the sensitivity of using these fluorescent markers in deep tissue imaging [4, 5]. Most of the upconversion fluorescent markers systems including upconversion organic dyes and quantum dots require high laser excitation intensity (typically~107 −1011 W.cm−2 ), often resulting in serious damage of biological samples [8, 9]. Upconversion organic dyes and quantum dot are limited by photobleating, blinking, and toxicity [10]

Methods

Results

Conclusion