Recent Progress of Near-Infrared Fluorescence in vivo Bioimaging in the Second and Third Biological Window

Abstract

Near-infrared (NIR) fluorescence bioimaging using above to 1000 nm wavelength region is a promising analytical method on visualizing deep tissues. As compared to the short-wavelength ultraviolet (UV: < 400 nm) or visible (VIS: 400 -700 nm) region, which results in an extremely low absorption or scattering of biomolecules and water in the body, NIR light passes through the tissues. Various fluorescent probes that emit NIR emission in the second (1100 -1400 nm) or third (1550 -1800 nm) biological windows have been developed and used for NIR in vivo imaging. Single-walled carbon nanotubes (SWCNTs), quantum dots (QDs), rare-earth doped ceramic nanoparticles (RED-CNPs), and organic dye-based probes have been proposed by many researchers, and are used to successfully visualize the bloodstream, organs, and disease-affected regions, such as cancer. NIR imaging in the second and third biological windows is an effective analytical method on visualizing deep tissues.

C 1-Symmetrical [Ir(C^N1)(C^N2)(N^O)]-tris-heteroleptic Ir(iii)-complexes with one strong N^O-ancillary π-donor for efficient all-solution-processed near-infrared (NIR) polymer light-emitting diodes (PLEDs)

“…Therefore, as summarized in Table S4 (ESI †), in consideration of the dominant HOMO -LUMO transition for either the S 0 -S 1 (73.71% for 1 versus 96.92% for 2) or the S 0 -T 1 (89.19% for 1 versus 75.91% for 2) excitation, the experimentally visible absorption should be ascribed to the 1 LC/ 1 MLCT-admixed transitions, and the S 0 -T 1 excited lowest-energy (over 600 nm) absorption is mostly assigned to the 3 ILCT/ 3 LLCT transition mixed with the less 3 MLCT one. In comparison, as to the two C^N 2 -(btp) À -incorporated 3, although the similar 1,3 LC/ 1,3 MLCT-transitions to 1,3 LC are realized, its absorption bands are limited in the visible range, which should be due to the relatively smaller molecule conjugation. Undoubtedly, also arising from the domination (82.14%) of the HOMO -LUMO Fig.…”

“…T 1 -radiative transition, the visible red-light emission of 3 shows a typical phosphorescence characteristic of the 3 LC/ 3 MLCTadmixed nature with 3 LC dominating. With regard to 1 and 2, although their NIR-phosphorescence is also 3 LC-dominant within the 3 LC/ 3 MLCT-admixed T 1 state, the slightly larger 3 LLCT portion for 1 and the significantly larger 3 ILCT portion for 2 should be attributed to their C 1 -symmetry. Alongside this case, an augmented (18.569%) 3 MLCT character in the bisheteroleptic 1 instead of the tris-heteroleptic 2 (14.309%) is unexpected, which should probably be ascribed to the stronger electronic perturbation 22 by the N^O-(pbi) À ancillary ligand capable of stronger p-donation.…”

“…Motivated by the emergence of near-infrared (NIR; l em 4 700 nm) organic/polymer light-emitting diodes (NIR-OLEDs/ PLEDs) promising in night-vision and information-security displays, 1 optical telecommunication 2 and photodynamic therapy, 3 concrete efforts 4 have been devoted to the development of new and efficient NIR-emissive lumophores. Meanwhile, in order to effectively suppress the detrimental aggregationcaused quenching (ACQ) 5 effect, their doping into compatible small-molecule or polymeric hosts as the emitting layers (EMLs) is necessary for reliable NIR-OLEDs/PLEDs through vacuum-deposition or solution-processing.…”

“…As a matter of fact, along with the progressive efforts to develop Ir(III)-complex-based NIR-OLEDs/PLEDs, [16][17][18][19][20] LiF/Al, 18 giving an additional tactic to achieve the desirable all-solution-processed NIR-PLEDs (ASP-Type-IB/IC, also see Scheme 1). Specifically, although [Ir(iqbt)(C^N 2 )(L^X)] with an appreciably augmented 3 MLCT effect compared to that of fac-[Ir(iqbt) 3 ] or [Ir(iqbt) 2 (L^X)] was demonstrated to support the significantly improved efficiency (F PL /Z EQE ) through non-allsolution-processing, 19 [Ir(C^N 1 )(C^N 2 )(L^X)]-tris-heteroleptic Ir(III)-complexes including Hiqbt as the HC^N 1 ligand, to the best of our knowledge, have never been used for to their all-solution-processed NIR-OLEDs/PLEDs.…”

Effects of hydrophilic/hydrophobic blocks ratio of PEG-b-PLGA on emission intensity and stability of over-1000 nm near-infrared (NIR-II) fluorescence dye-loaded polymeric micellar nanoparticles

“…In the last decade, dynamic live fluorescence imaging within over-thousand-nanometer (OTN) near-infrared (NIR) optical window, the so-called second biological window (NIR-II), has attracted considerable interest for the visualization of blood vessels, 1,2 organs 3,4 and tumors, 5,6 and monitoring drug delivery. 7,8 OTN-NIR fluorescence imaging 9 provides higher transparency and depth of observation in vivo compared to traditional fluorescence imaging in the visible and NIR regions (400-900 nm) due to low absorption and light scattering through the use of the light of longer wavelength. [10][11][12][13] Among the various OTN-NIR fluorophores such as single-walled carbon nanotubes, [14][15][16] quantum dots, 17,18 rare-earth-doped nanoparticles, [19][20][21][22] organic dye-based phosphors (including novel organic dyes), [23][24][25][26] dye molecular aggregations, [27][28][29][30][31] dye-encapsulated micelles, 32,33 and dye conjugated peptides, 5 organic dye-based phosphors are promising candidates because of their potentials of low toxicity in biological applications.…”