Quantitative assessment of energy transfer in upconverting nanoparticles grafted with organic dyes

Abstract

Upconverting nanoparticles (UCNPs) are luminophores that have been investigated for a multitude of biological applications, notably low-background imaging, high-sensitivity assays, and cancer theranostics. In these applications, they are frequently used as a donor in resonance energy transfer (RET) pairs. However, because of the peculiarity and non-linearity of their luminescence mechanism, their behavior as a RET pair component has been difficult to predict quantitatively, preventing their optimization for subsequent applications. In this article, we assembled UCNP-organic dye RET systems and investigated their luminescence decays and spectra, with varying UCNP sizes and quantities of dyes grafted onto their surface. We observed an increase in RET efficiency with lower particle sizes and higher dye decoration. We also observed several unexpected effects, notably a quenching of UCNP luminescence bands that are not resonant with the absorption of organic dyes. We proposed a semi-empirical Monte Carlo model for predicting the behavior of UCNP-organic dye systems, and validated it by comparison with our experimental data. These findings will be useful for the development of more accurate UCNP-based assays, sensors, and imaging agents, as well as for optimization of UCNP-organic dye RET systems employed in cancer treatment and theranostics.

Long‐Term Colloidal and Chemical Stability in Aqueous Media of NaYF4‐Type Upconversion Nanoparticles Modified by Ligand‐Exchange

“…As reported by the group of Parak a comb‐like polymer consisting of a poly(maleic anhydride) backbone with a modified hydrophobic chain can be used for the successful transfer of colloidal nanoparticles into a hydrophilic environment. During this process, also polymer micelles with no UCNPs inside are generated . This is attributed by the intention to ensure a complete coating of the UCNPs by using an excess of the amphiphilic polymer.…”

Core or Shell? Er3+ FRET Donors in Upconversion Nanoparticles

“…[11] FRET biosensing with nanoparticle donors and acceptors (e.g., quantum dots) [12,13] and lanthanide complex donors [14,15] has been applied for many years. Also, in the field of UCNPs, FRET is becoming more and more popular, and many studies have investigated UCNP donors in combination with various acceptors, including organic dyes, [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] fluorescent proteins, [32] and nanoparticles. [33][34][35][36][37][38][39][40] Despite the increasing interest, FRET with UCNPs is far from well understood.…”

Single-molecule photoreaction quantitation through intraparticle-surface energy transfer (i-SET) spectroscopy

“…17 and Supplementary Tables 3, 4). By contrast, the measured energy transfer efficiency is only 16% for conventional NaYF 4 :Yb,Er(18,2 mol%)@NaYF 4 , the most representative low-doping nanoparticle widely applied for upconversion-based FRET studies 41,42 , when decorated with a similar concentration of dye molecules ( Fig. 2d and Supplementary Figs.…”