Near-Infrared Intraoperative Chemiluminescence Imaging

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

Luminescence imaging is a powerful and versatile technique for investigating cell physiology and pathology in living systems, making significant contributions to life science research and clinical diagnosis. In recent years, luminescent transition metal complexes have gained significant attention for diagnostic and therapeutic applications due to their unique photophysical and photochemical properties. In this Review, we provide a comprehensive overview of the recent development of luminescent transition metal complexes for bioimaging and biosensing applications, with a focus on transition metal centers with a d6, d8, and d10 electronic configuration. We elucidate the structure-property relationships of luminescent transition metal complexes, exploring how their structural characteristics can be manipulated to control their biological behavior such as cellular uptake, localization, biocompatibility, pharmacokinetics, and biodistribution. Furthermore, we introduce the various design strategies that leverage the interesting photophysical properties of luminescent transition metal complexes for a wide variety of biological applications, including autofluorescence-free imaging, multimodal imaging, organelle imaging, biological sensing, microenvironment monitoring, bioorthogonal labeling, bacterial imaging, and cell viability assessment. Finally, we provide insights into the challenges and perspectives of luminescent transition metal complexes for bioimaging and biosensing applications, as well as their use in disease diagnosis and treatment evaluation.

Intraoperative biophotonic imaging systems for image-guided interventions

Biophotonic imaging has revolutionized the operation room by providing surgeons intraoperative image-guidance to diagnose tumors more efficiently and to resect tumors with real-time image navigation. Among many medical imaging modalities, near-infrared (NIR) light is ideal for image-guided surgery because it penetrates relatively deeply into living tissue, while nuclear imaging provides quantitative and unlimited depth information. It is therefore ideal to develop an integrated imaging system by combining NIR fluorescence and gamma-positron imaging to provide surgeons with highly sensitive and quantitative detection of diseases, such as cancer, in real-time without changing the look of the surgical field. The focus of this review is to provide recent progress in intraoperative biophotonic imaging systems, NIR fluorescence imaging and intraoperative nuclear imaging devices, and their future perspectives for image-guided interventions.

Divalent Eu2+ ion - an effective inorganic mediator of energy transfer from the primary chemiluminescence emitter 3 Me2 CHC(H)=O* on Tb3+ and Ru(bpy)3 2+ ions

This study demonstrated for the first time that chemiluminescence (CL) from oxidation of Buⁱ ₂ AlH (Bu = C₄ H₉ ) using oxygen from tetrahydrofuran (THF) was significantly enhanced by the addition of Ru(bpy)₃ ²⁺ . A quantitative comparison of the enhancement efficiency of this CL was performed by addition of ionic phosphors Eu²⁺ , Tb³⁺ and Ru(bpy)₃ ²⁺ . CL enhancement was caused by energy transfer from the primary CL emitter (³ Me₂ CHC(H)=O* aldehyde) to these ionic phosphors. The CL efficiency enhancement was in the order: Eu²⁺ (8.9 × 10⁶ ) > Tb³⁺ (100) > Ru(bpy)₃ ²⁺ (50). The enhanced CL emitters were excited ions: Eu²⁺ *, λ_max  = 465 nm; Tb³⁺ *, λ_max  = 485, 542, 625 nm; and Ru(bpy)₃ ²⁺ *, λ_max  = 567 nm. When two ions Eu²⁺ -Tb³⁺ or Eu²⁺ -Ru(bpy)₃ ²⁺ were present in the reaction solution, the efficiency of CL enhancement by Tb³⁺ or Ru(bpy)₃ ²⁺ ions was much higher, being 1.2 × 10⁶ and 4.2 × 10⁴ , respectively. In this case, two excited ions were simultaneously registered as CL emitters: Eu²⁺ * and Tb³⁺ * or Eu²⁺ * and Ru(bpy)₃ ²⁺ *. Emission intensity of the Eu²⁺ * ion in these emitter doublets is much lower than when only one Eu²⁺ ion is present in solution.

Near-Infrared Dioxetane Luminophores with Direct Chemiluminescence Emission Mode

Chemiluminescent luminophores are considered as one of the most sensitive families of probes for detection and imaging applications. Due to their high signal-to-noise ratios, luminophores with near-infrared (NIR) emission are particularly important for in vivo use. In addition, light with such long wavelength has significantly greater capability for penetration through organic tissue. So far, only a few reports have described the use of chemiluminescence systems for in vivo imaging. Such systems are always based on an energy-transfer process from a chemiluminescent precursor to a nearby emissive fluorescent dye. Here, we describe the development of the first chemiluminescent luminophores with a direct mode of NIR light emission that are suitable for use under physiological conditions. Our strategy is based on incorporation of a substituent with an extended π-electron system on the excited species obtained during the chemiexcitation pathway of Schaap's adamantylidene-dioxetane probe. In this manner, we designed and synthesized two new luminophores with direct light emission wavelength in the NIR region. Masking of the luminophores with analyte-responsive groups has resulted in turn-ON probes for detection and imaging of β-galactosidase and hydrogen peroxide. The probes' ability to image their corresponding analyte/enzyme was effectively demonstrated in vitro for β-galactosidase activity and in vivo in a mouse model of inflammation. We anticipate that our strategy for obtaining NIR luminophores will open new doors for further exploration of complex biomolecular systems using non-invasive intravital chemiluminescence imaging techniques.