Radioactive Europium‐Chelate‐Based Silica Nanoparticles as a Probe for Stability, Incorporation Efficiency and Trace Analysis

Abstract

Two luminescent terbium and europium lanthanide chelates were efficiently embedded into silica nanoparticles by using a reverse microemulsion process. The incorporation was achieved without covalent bonding between the lanthanide chelates and the silica matrix. To investigate the efficiency of the incorporation process and the stability of the silica‐encapsulated lanthanide complex, a method based on a radioactive probe was developed; γ‐emitting europium (152) chelates were synthesized and incorporated into silica nanoparticles. Measurements of the γ activity through the entire synthesis allowed the accurate characterization of the incorporation efficiency of the used chelates. A clear correlation was established between the physicochemical properties of the different chelates and the measured incorporation efficiencies. A very efficient noncovalent incorporation of lanthanide chelates in highly stable nanoparticles was achieved by tuning the chelate properties, thus rendering the development of lanthanide‐based fluorescent nanoparticles easier.

A Gadolinium Complex Confined in Silica Nanoparticles as a Highly Efficient T1/T2 MRI Contrast Agent

“…Moreover [Gd(ebpatcn)(H 2 O)] has a reasonably high stability ( p Gd=13.1) with respect to ligand dissociation providing an additional barrier capable of preventing the release of the toxic aqua ion from the NPs in the absence of covalent binding to the silica matrix. The high stability of the Gd NPs in H 2 O over a pH range of 7–8 with respect to metal leakage over a month period has been confirmed by inductively coupled plasma mass spectrometry (ICPMS) and by optical and radiotracing studies performed on the analogous Eu III and Tb III ebpatcn complexes 11. The value of the luminescence emission lifetime measured for the Tb NPs in H 2 O (1.86(3) ms) is slightly longer than the value measured for the monoaqua [Tb(ebpatcn)(H 2 O)] complex in water (1.60(2) ms, which indicates the presence of only one coordinated water molecule in the encapsulated complex.…”

“…Above 500 MHz, r 2 exceeds 150 s −1 m M −1 in the case of the large NPs and even 227 s −1 m M −1 in the case of the small ones. Here, using the Gd III concentration in the solution measured either from the NMR paramagnetic susceptibility shift14 or by ICPMS,11 the NPGd50 were shown to contain about 1,000 [Gd(ebpatcn)(H 2 O)] complexes (see the Supporting Information) so that their relaxivities on a per NP basis are r 1 ≅1,9×10 4 s −1 ⋅(m M of NP) −1 at 50 MHz and r 2 >1,5×10 5 s −1 ⋅(m M of NP) −1 for above 500 MHz. Larger NPs are obtained when a larger number of complexes are incorporated in the NP (see the Supporting Information).…”

Amine‐Functionalized Silica Nanoparticles Incorporating Covalently Linked Visible‐Light‐Excitable Eu3+ Complexes: Synthesis, Characterization, and Cell‐Uptake Studies

“…Moreover, encapsulation into silica nanoparticles improves the chemical and photostabilities of the loaded species . The remarkable optical properties of lanthanide ions (Ln 3+ ), such as narrow emission bands, high color purity, large Stokes shifts, and long luminescent decay times, have often been combined with the advantageous characteristics of silica nanoparticles . However, the use of Ln 3+ ions as bioprobes is restricted, due to their low molar‐absorption coefficients and UV excitation wavelengths .…”

Dye-sensitized lanthanide containing nanoparticles for luminescence based applications

“…Jiang et al designed NPs with emission colors from green to red by co-binding different molar ratios of Eu (64) and Tb(64). 183 Wartenberg et al designed their own Tb-Eu co-doped Silica NPs with 72 or 73 as antennas, 184 and proposed a new method to study the efficiency of the incorporation process by using 152 Eu chelates for radioactivity measurements. The effect of Ln-complex encapsulation on the ligand triplet-state energy level was questioned by Eliseeva et al, and [Eu 2 (75) 3 ] binuclear helicates incorporation into Silica NPs was shown to have no impact on it.…”