Two-Photon Luminescent Bone Imaging Using Europium Nanoagents

Abstract

Gunnlaugsson and co-workers have undertaken the synthesis and physical study of luminescent nanoagents for use in imaging of damaged bone structures. These agents are based on europium macrocyclic complexes that are tethered to the surface of nanometer-sized gold nanoparticles through covalent spacers. These nanoagents can selectively bind to exposed calcium sites, also called microcracks, within a damaged bone surface. Using a sensitizing antennae and two-photon microscopy, the authors have achieved 3D mapping of the damaged bone area by observing the long-wavelength lanthanide-centered emission.

Surface‐Modified Gold Nanoparticles Possessing Two‐Channel Responsive EuIII/TbIII Cyclen Complexes as Luminescent Logic Gate Mimics

“…A similar and common inorganic support that has been utilized in both sensing and imaging, are AuNP structures, which are functionalized at the metal surface by attachment through thiol groups . We have demonstrated the use of AuNPs functionalised with emissive Ln III complexes for the formation of selective luminescence probes, imaging agents, and AuNP‐based displacement assays for organic molecules . In this Communication, we combine our interest in material and sensing chemistry, by presenting an example of surface modification of AuNPs with luminescent ternary complexes that are responsive, resulting in modulation of luminescent “outputs” that can be expressed in terms of molecular logic functions.…”

“…6nmc ompared to the non-functionalised AuNPs;c onfirming the adsorptiono ft he complexes to the surface, as eluded to above. Monitoring the maximum Ln III emission intensityu pon titration of AuNP-[Eu.1] 3 + + and AuNP-[Tb.1] 3 + + with appropriate sensitising antenna allowed determination of the number of bound complexes, [17] these studies indicatedc a. 50 complexes wereb ound to each AuNP.E xcitation of the AuNP-[Eu.1] 3 + + and AuNP-[Tb.1] 3 + + at 318 nm resulted in Stoke's-shifted fluorescence (l em = 355 nm).…”

Opportunities for Persistent Luminescent Nanoparticles in Luminescence Imaging of Biological Systems and Photodynamic Therapy

“…Thus, luminescence imaging of biological systems is based on exciting a volume of a sample containing a luminescent compound using an adequate excitation source and wavelength and collecting the light emitted. Luminescence imaging is a sensitive technique that allows diagnosing diseases [ 15 , 16 , 17 ], reconstructing 3-D structures of tissues or cellular components [ 18 , 19 ], sensing chemical species [ 1 , 2 , 3 , 12 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ], and unraveling cellular processes [ 39 , 40 , 41 ]. One of the drawbacks of this technique is the strong background emission intensity, especially in the blue and green regions of the electromagnetic spectrum that are often higher than those of the luminescent compound.…”

Two-Photon Excitation for Bone Imaging: A New Application for Lanthanide Luminescence

“…In this issue of Chem, the work by Gunnlaugsson and colleagues builds upon those results and further enhances the ability to image bone structure. 10 Because large amounts of emissive molecules are necessary for high-resolution imaging, the authors isolated a cyclen-based system with three iminodiacetate-Ca II -targeting pendants, to which a fourth thiol-terminated pendant was added (1.Eu.Na in Figure 1). This improved ligand enabled the authors to anchor approximately 20 Eu III -containing complexes onto the surface of Au nanoparticles (AuNP-1.Eu.Na in Figure 1).…”