NIR-to-NIR Imaging: Extended Excitation Up to 2.2 μm Using Harmonic Nanoparticles with a Tunable hIGh EneRgy (TIGER) Widefield Microscope

Abstract

Near-infrared (NIR) marker-based imaging is of growing importance for deep tissue imaging and is based on a considerable reduction of optical losses at large wavelengths. We aim to extend the range of NIR excitation wavelengths particularly to values beyond 1.6 μm in order to profit from the low loss biological windows NIR-III and NIR-IV. We address this task by studying NIR-excitation to NIR-emission conversion and imaging in the range of 1200 up to 2400 nm at the example of harmonic Mg-doped lithium niobate nanoparticles (i) using a nonlinear diffuse femtosecond-pulse reflectometer and (ii) a Tunable hIGh EneRgy (TIGER) widefield microscope. We successfully demonstrate the existence of appropriate excitation/emission configurations in this spectral region taking harmonic generation into account. Moreover, NIR-imaging using the most striking configurations NIR-III to NIR-I, based on second harmonic generation (SHG), and NIR-IV to NIR-I, based on third harmonic generation (THG), is demonstrated with excitation wavelengths from 1.6–1.8 μm and from 2.1–2.2 μm, respectively. The advantages of the approach and the potential to additionally extend the emission range up to 2400 nm, making use of sum frequency generation (SFG) and difference frequency generation (DFG), are discussed.

Gd3+-Functionalized Lithium Niobate Nanoparticles for Dual Multiphoton and Magnetic Resonance Bioimaging

“…The nonlinear response of LNO NPs upon femtosecond pulse excitation was first reported at 800 nm (SHG) and successively in the 700–1300 nm excitation range for SHG and for other nonlinear and frequency mixing processes . Very recently, the SHG and THG from Mg-doped LNO NPs have been observed with excitation up to 2.2 μm . At 800 nm, the SHG efficiency of the LNO NPs studied here was determined from the ensemble measurements, leading to an orientation-averaged second-order susceptibility χ (2) value of ∼40 pm/V .…”

“…51 Very recently, the SHG and THG from Mg-doped LNO NPs have been observed with excitation up to 2.2 μm. 42 At 800 nm, the SHG efficiency of the LNO NPs studied here was determined from the ensemble measurements, leading to an orientation-averaged second-order susceptibility χ (2) value of ∼40 pm/V. 52 In Figure 2, we present a complete set of multiphoton images obtained on DU145 human prostate cancer cells treated with LNO-Gd NPs at 50 μg/mL following the protocol reported in the Experimental Section.…”

“…37,38 Sugiyama et al reported the labeling of hematopoietic stem cells with low concentrations of barium titanate (BaTiO3) HNPs to understand their cellular uptake and intracellular fate, 39 and other authors demonstrated their in vivo application. 40,41 The inherent flexibility and stability of the nonlinear response of HNPs upon excitation from UV to NIR-II, 33 NIR-III 42 and NIR-IV 42 would be highly advantageous in the context of multimodal imaging combining their capability for nonlinear optical response with magnetic properties for MRI. Recently, the surface decoration of BaTiO3 HNPs with gold or silver nanoparticles allowed for combined two-photon second harmonic generation imaging and one-photon surface enhanced Raman scattering in living cells.…”

“…Seminal achievements were reported with lanthanide-doped upconversion NPs for the combination of NIR luminescence imaging with complementary MRI, X-ray CT, or positron emission tomography (PET) imaging modalities. − Nanoconjugates based on iron oxide NPs were also disclosed for dual MRI/PET and MRI/CT tumor imaging. , Due to their ultrasmall size and luminescence properties, noble-metal nanoclusters were conjugated to gadolinium (Gd) ions to provide hybrid nanoprobes for targeted triple-modal NIR fluorescence/MRI/CT in vivo tumor imaging. , In addition to their multimodal imaging capabilities, nanoparticulate systems were used to increase the local concentration and efficiency of Gd-based MRI contrast agents by providing an effective delivery of reporters and a high payload of paramagnetic ions to the target sites. − Recently, harmonic NPs (HNPs) were proposed as highly efficient NIR probes presenting several complementary advantages with respect to other optically active NPs, − including the flexibility of the excitation wavelength, the absence of saturation, bleaching/blinking events, and the possibility of colocalizing the simultaneously emitted second and third harmonic signals excited for their identification in optically complex environments such as tumor tissues . We previously demonstrated the potential of bismuth ferrite (BiFeO 3 ) HNPs for cell labeling and tracking by NIR-II multiphoton microscopy in both muscle and lung tissues. , Sugiyama et al reported the labeling of hematopoietic stem cells with low concentrations of barium titanate (BaTiO 3 ) HNPs to understand their cellular uptake and intracellular fate, and other authors demonstrated their in vivo application. , The inherent flexibility and stability of the nonlinear response of HNPs upon excitation from UV to NIR-II, NIR-III, and NIR-IV would be highly advantageous in the context of multimodal imaging combining their capability for nonlinear optical response with magnetic properties for MRI. Recently, the surface decoration of BaTiO 3 HNPs with gold or silver NPs allowed for combined two-photon second harmonic generation (SHG) imaging and one-photon surface-enhanced Raman scattering in living cells …”

Solution‐Based Synthesis Routes for the Preparation of Noncentrosymmetric 0‐D Oxide Nanocrystals with Perovskite and Nonperovskite Structures

“…Harmonic signals from NCO nanocrystals used as exogenous bio-labeling probes thus hold great promise in the bioimaging and theranostic fields [15][16][17][18][19][20] and especially for very long term and fast in vivo imaging in the four NIR biological transparency windows. [21][22][23][24] As nonlinear optics is concerned, both Rayleigh and Mie scattering from all-dielectric nanostructures [25,26] and metal-NCO core-shell cavities [27,28] have also stimulated a lot of interest for the tailored and on-demand enhancement of the wavelengthdependent emission of harmonic signals when size control of these (hybrid)-nanostructures is achieved. [29] Likewise, preparation of thin dielectric films from NCO colloidal suspensions under mild chemical conditions relying on the heterogeneous mixing with a monomer paved the way for the development of new printable and spin-coated functional devices.…”