Optically Detected Degradation of NaYF₄:Yb,Tm-Based Upconversion Nanoparticles in Phosphate Buffered Saline Solution

Abstract

In a proof-of-concept study, we assessed different analytical and spectroscopic parameters for stability screening of differently sized β-NaYF:20 mol % Yb, 2 mol % Tm upconversion nanoparticles (UCNPs) exemplarily in the bioanalytically relevant buffer phosphate buffered saline (PBS; pH 7.4) at 37 and 50 °C. This included the potentiometric determination of the amount of released fluoride ions, surface analysis with X-ray photoelectron spectroscopy (XPS), and steady-state and time-resolved fluorescence measurements. Based on these results, the luminescence lifetime of the 800 nm upconversion emission was identified as an optimum parameter for stability screening of UCNPs and changes in particle surface chemistry.

A simple neridronate-based surface coating strategy for upconversion nanoparticles: highly colloidally stable125I-radiolabeled NaYF4:Yb3+/Er3+@PEG nanoparticles for multimodalin vivotissue imaging

“…20 Few articles have recently addressed potential NaYF 4 :Yb 3+ / Er 3+ particle aggregation and dissolution in bioanalytically relevant media, such as phosphate buffered saline (PBS), and changes in the morphology, particle surface composition, Ln ion leakage, and photoluminescence intensity. 21,22 Though it is widely accepted that the NaYF 4 :Yb 3+ /Er 3+ -based nanoparticles possess high photochemical and thermal stability and low solubility in water, 23 their properties can be strongly affected by certain anions and ligands present in the biological media. 22 In PBS, the NaYF 4 :Yb 3+ /Er 3+ nanoparticles can undergo partial dissolution, subsequently forming stable Ln-phosphate complexes in the solution and on the particle surface due to the much lower solubility product of Ln-phosphates than that of the corresponding fluorides.…”

“…21,22 Though it is widely accepted that the NaYF 4 :Yb 3+ /Er 3+ -based nanoparticles possess high photochemical and thermal stability and low solubility in water, 23 their properties can be strongly affected by certain anions and ligands present in the biological media. 22 In PBS, the NaYF 4 :Yb 3+ /Er 3+ nanoparticles can undergo partial dissolution, subsequently forming stable Ln-phosphate complexes in the solution and on the particle surface due to the much lower solubility product of Ln-phosphates than that of the corresponding fluorides. 24 Moreover, this partial dissolution and particle morphological transformation under biological conditions may lead to organelle damage due to the stripping of the membrane phosphate groups from the lipid bilayer, which initiates pro-inflammatory effects and/or the generation of biological hazards in cells and animals.…”

Förster Resonance Energy Transfer‐Activated Processes in Smart Nanotheranostics Fabricated in a Sustainable Manner

“…[49].T he calculated h Q values for encapsulated NaYF 4 : Tm 3 + ,Y b 3 + NPs are much lower than the ones for ligand-free or silanized NaYF 4 :Tm 3 + ,Y b 3 + NPs. [49].T he calculated h Q values for encapsulated NaYF 4 : Tm 3 + ,Y b 3 + NPs are much lower than the ones for ligand-free or silanized NaYF 4 :Tm 3 + ,Y b 3 + NPs.…”

“…in which I Q and I 0 are integrated luminescence decay curves measured in the presencea nd absence of al uminescence quenching process, in our case after and before encapsulation of NaYF 4 :Tm 3 + ,Y b 3 + NPs, respectively.T he h Q values were equal to % 1.6 and % 5.3 %f or blue (470 nm) and red (800 nm) Tm 3 + ion up-conversion decay curves, respectively,s howing stronger quenching for red (800 nm) emission similar as in ref. [49].T he calculated h Q values for encapsulated NaYF 4 : Tm 3 + ,Y b 3 + NPs are much lower than the ones for ligand-free or silanized NaYF 4 :Tm 3 + ,Y b 3 + NPs. [50] Arppe et al [48] ;however,they allowed us to confirm the positive shielding effect provided by the selected emulsification/solvent evaporation methodf ollowed by the LbL encapsulationp rocess.…”

“…When the emission spectra of NCs loadedo nly with NaYF 4 :Tm 3 + ,Y b 3 + NPs( black line in Figure 4a)a re compared to the corresponding ones obtained for as-synthesized NPs (Figure S1, Supporting Information) no evident differences in relative blue-to-red emission ratio is observed, additionally only as light luminescencel ifetimes hortening was observed upon encapsulation (Table S1, Supporting Information). However,t oi nvestigate the influenceo ft he encapsulation process on the up-conversion Tm 3 + ion emission in am ore quantita-tive manner we have calculated the quenching efficiencyp arameter (h Q )a ccordingt ot he equation introduced by the Resch-Genger group: [48,49]…”