Engineering Red-Enhanced and Biocompatible Upconversion Nanoparticles

Masfer Alkahtani,Anfal Alfahd,Najla Alsofyani,Philip R Hemmer,Hussam Qasem,Fahad A Almughem,Abdullah A Alshehri,Anas A Almuqhim

doi:10.3390/nano11020284

Abstract

The exceptional optical properties of lanthanide-doped upconversion nanoparticles (UCNPs) make them among the best fluorescent markers for many promising bioapplications. To fully utilize the unique advantages of the UCNPs for bioapplications, recent significant efforts have been put into improving the brightness of small UCNPs crystals by optimizing dopant concentrations and utilizing the addition of inert shells to avoid surface quenching effects. In this work, we engineered bright and small size upconversion nanoparticles in a core–shell–shell (CSS) structure. The emission of the synthesized CSS UCNPs is enhanced in the biological transparency window under biocompatible excitation wavelength by optimizing dopant ion concentrations. We also investigated the biosafety of the synthesized CSS UCNP particles in living cell models to ensure bright and non-toxic fluorescent probes for promising bioapplications.

Highlights

Nanoscale luminescent materials have attracted a special interest in numerous biological applications including biological tissue imaging, super-resolution imaging, sensitive optical sensing, optogenetic, and drug delivery
Here, we present a red-enhanced emission of 808 nm excited upconversion nanoparticles (UCNPs) using a core–shell–shell (CSS) structure, where sensitizer and activator ion concentrations are optimized to meet the requirements of biologically transparent fluorescent markers
The C, CS, and CCS UCNPs presented in this work were synthesized following a solvent thermal protocol previously reported in [31] and detailed in the material and methods section

Summary

Introduction

Nanoscale luminescent materials have attracted a special interest in numerous biological applications including biological tissue imaging, super-resolution imaging, sensitive optical sensing, optogenetic (brain studies), and drug delivery. These include organic dyes [1,2,3], quantum dots (QDs) [4,5], and fluorescent polymers [6,7,8]; they are limited by either photostability [9], toxicity [10,11], or chemical environment sensitivity [12]. While some of the diamond color centers can be excited and detected within the biological transparency [13,17], their optical properties often degrade as the size of the diamond crystal decreases to biologically advantageous sizes (less than 7 nm) [18]

Methods

Results

Conclusion