Fluorescence Lifetime Research Articles

A Single Early Life Acetaminophen Exposure Causes Persistent Abnormalities in the Murine Lung.

Whether early life acetaminophen (APAP) exposures injure the developing lung is controversial. We sought to correlate murine pulmonary developmental expression profiles of Cyp2e1 to susceptibility to APAP exposure. P14 C57BL/6 mice were exposed to APAP (140 mg/kg x 1, IP) and assessed for evidence of a histologic, metabolic, functional, and/or transcriptional pulmonary response. Similar experiments were performed in P14 IL6-/- mice given the controversial role of IL6 in APAP-induced tissue injury. No evidence of hepatic injury was noted in APAP exposed P14 mice. In contrast, within 6 hours of exposure pulmonary tissue demonstrated histologic and functional evidence of injury and increased mitochondrial load by fluorescent lifetime imaging microscopy (FLIM). The pulmonary transcriptional response was marked by increased expression of Cyp2e1, Nrf2 targets, and pro-inflammatory genes. Specifically, APAP exposure increased pulmonary IL6 mRNA, protein and associated STAT3 signaling. In contrast, IL6-/- demonstrated attenuated STAT3 signaling and injury at 6 hours of exposure. At P28, functional and stereologic assessment of both WT and IL6-/- mice exposed to a single dose of APAP at P14 revealed persistent abnormalities consistent with lung enlargement and alveolar simplification. Developmentally regulated surges in pulmonary Cyp2e1 expression correlate with sensitivity to APAP exposures that do not cause recognizable hepatic injury. A single exposure during this developmental window is enough to cause persistent functional and stereological abnormalities. These results highlight the need to further study the relationship between developmentally-regulated pulmonary Cyp2e1 expression, APAP exposures and long-term pulmonary dysfunction.

Fluorescence lifetime imaging in drug delivery research.

Once an exotic add-on to fluorescence microscopy for life science research, fluorescence lifetime imaging (FLIm) has become a powerful and increasingly utilised technique owing to its self-calibration nature, which affords superior quantification over conventional steady-state fluorescence imaging. This review focuses on the state-of-the-art implementation of FLIm related to the formulation, release, dosage, and mechanism of action of drugs aimed for innovative diagnostics and therapy. Quantitative measurements using FLIm have appeared instrumental for encapsulated drug delivery design, pharmacokinetics and pharmacodynamics, pathological investigations, early disease diagnosis, and evaluation of therapeutic efficacy. Attention is paid to the latest advances in lifetime-engineered nanomaterials and practical instrumentation, which begin to show preclinical and clinical translation potential beyond in vitro samples of cells and tissues. Finally, major challenges that need to be overcome in order to facilitate future perspectives are discussed.

Toluidine blue O demethylated photoproducts as type II photosensitizers.

Toluidine blue O (TBO) is a type I-type II photosensitizer that has shown good efficacy and selectivity in antimicrobial and anticancer photodynamic therapy applications. However, its complex photochemistry with multiple photoproducts hinders its application as a photosensitizer. We have previously described the mechanism for photooxidative demethylation of TBO which in acetonitrile yields two main products: demethylated-TBO (d-TBO) and double-demethylated-TBO (dd-TBO). In the current work, we describe the photophysical properties of these two photoproducts. In acetonitrile and phosphate buffer, demethylation induces an hypsochromic shift in the absorption and fluorescence emission maxima. Fluorescence quantum yields increase slightly for the demethylated photoproducts, in agreement with the lengthening of the fluorescence lifetimes. Triplet excited states lifetimes in the presence of oxygen decreased slightly upon demethylation. However, the singlet oxygen quantum yield increased significantly reaching unity for the dd-TBO photoproduct. These results are interpreted in terms of the competing pathways of TBO photochemistry. For TBO, demethylation is the main pathway for deactivation of the excited state, while for d-TBO, demethylation and singlet oxygen generation are significant. For dd-TBO, singlet oxygen generation is the main deactivation pathway. Overall, TBO demethylated photoproducts demonstrate good potential as candidates for photodynamic therapy applications.

Insights into the Spectral Characteristics and Sources of Dissolved Organic Matter in a Water Supply Reservoir.

This study focuses on the composition and sources of dissolved organic matter (DOM) in the Fancun Reservoir, located in Ningguo City, Anhui Province, China. The investigation was conducted by analyzing the spectral characteristics of DOM using UV-Vis absorption spectra and fluorescence spectroscopy. The humic substances were dominated by fulvic acid, with an average DOM concentration of 30.54mg/L at the reservoir outlet primarily originating from internal release. Fluorescence indices suggested a strong autochthonous contribution of DOM and weak humus characteristics. Three DOM components were identified through parallel factor analysis. Aromatic protein substances in DOM ranged from 0.52 to 4.49%, suggesting minimal anthropogenic influence. The average fluorescence lifetime increased from 0.81 ns at the reservoir entrance to 0.91 ns at the outlet, with an average relative quantum yield of 4.99%, implying stabilization throughout the reservoir. Correlation analysis indicated positive correlations (P < 0.001) between absorption coefficients at specific wavelengths. Principal component analysis explained 67.7% of the total variance, indicating highly common DOM sources across sites.

Modulating room-temperature phosphorescence of D-π-A luminogens via methyl substitution, positional isomerism, and host-guest doping.

Organic room-temperature phosphorescence (RTP) luminogens have showed significant potential in the fields of diagnostics, sensing, and information encryption. However, it is difficult to achieve high RTP yield (ΦP) and long RTP lifetime simultaneously. By methyl substitution, positional isomerism, and host-guest doping, three new D-π-A type luminogens named as TBTDA, 2M-TBTDA, and 3M-TBTDA were designed and synthesized, whose RTP properties were tuned and optimized. In various solvents and glassy THF solution, similar solvatochromism and phosphorescence nature of three luminogens were revealed. In poly (methyl methacrylate) (PMMA) and polyvinyl alcohol (PVA) matrixes, the luminogens showed high-contrast RTP properties. TBTDA emitted invisible afterglow in PMMA films, but with strong RTP and long green afterglow in PVA films. More importantly, 2M-TBTDA showed RTP and afterglow lifetimes of 809.81ms and 8s, as well as ΦP of up to 0.64 in PMMA at 1% doping concentration. Taking advantage of Foerster resonant energy transfer (FRET), reddish-brown or orange afterglow were observed, with emission maxima of 593-617nm, RTP and afterglow lifetimes of 299-566ms and 5-6s, ΦP of 0.34-0.46, as well as FRET efficiency of 70-90%. Finally, dynamic anti-counterfeiting and digital encryption were successfully constructed via different fluorescence, RTP colors, and afterglow lifetimes. This work not only obtained an efficient host-guest doping RTP system, but also can be expected to provide more theoretical guidance and experimental supports for molecular design, dynamic anti-counterfeiting and digital encryption.

Luminescent Lanthanide Infinite Coordination Polymers for Ratiometric Sensing Applications.

Ratiometric lanthanide coordination polymers (Ln-CPs) are advanced materials that combine the unique optical properties of lanthanide ions (e.g., Eu3+, Tb3+, Ce3+) with the structural flexibility and tunability of coordination polymers. These materials are widely used in biological and chemical sensing, environmental monitoring, and medical diagnostics due to their narrow-band emission, long fluorescence lifetimes, and excellent resistance to photobleaching. This review focuses on the composition, sensing mechanisms, and applications of ratiometric Ln-CPs. The ratiometric fluorescence mechanism relies on two distinct emission bands, which provides a self-calibrating, reliable, and precise method for detection. The relative intensity ratio between these bands varies with the concentration of the target analyte, enabling real-time monitoring and minimizing environmental interference. This ratiometric approach is particularly suitable for detecting trace analytes and for use in complex environments where factors like background noise, temperature fluctuations, and light intensity variations may affect the results. Finally, we outline future research directions for improving the design and synthesis of ratiometric Ln-CPs, such as incorporating long-lifetime reference luminescent molecules, exploring near-infrared emission systems, and developing up-conversion or two-photon luminescent materials. Progress in these areas could significantly broaden the scope of ratiometric Ln-CP applications, especially in biosensing, environmental monitoring, and other advanced fields.

Nanoscale Viscometry Reveals an Inherent Mucus Defect in Cystic Fibrosis.

The abnormally viscous and thick mucus is a hallmark of cystic fibrosis (CF). How the mutated CF gene causes abnormal mucus remains an unanswered question of paramount interest. Mucus is produced by the hydration of gel-forming mucin macromolecules that are stored in intracellular granules prior to release. Current understanding of mucin/mucus structure before and after secretion remains limited, and contradictory models exist. Here, we used a molecular viscometer and fluorescence lifetime imaging of human bronchoepithelial cells (Normal and CF) to measure nanometer-scale viscosity. We found significantly elevated intraluminal nanoviscosity in a population of CF mucin granules, indicating an intrinsic, presecretory mucin defect. Nanoviscosity influences protein conformational dynamics and function. Its elevation along the protein secretory pathway could arise from molecular overcrowding, impacting mucin's post-translational processing, hydration, and mucus rheology after release. The nanoviscosity of secreted CF mucus was elevated compared to that of non-CF. Interestingly, it was higher after release than in granules. Validation experiments indicate that reduced mobility of water hydrating mucin macromolecules may contribute to the high nanoviscosity in mucus and mucin granules. This suggests that mucins have a weakly ordered state in granules but adopt a highly ordered, nematic crystalline structure when secreted. This challenges the traditional view of mucus as a porous agarose-like gel and suggests an alternative model for mucin organization before and after secretion. Our study also indicates that endoplasmic reticulum stress due to molecular overcrowding could contribute to mucus pathogenesis in CF cells. It encourages the development of therapeutics that target presecretory mechanisms in CF and other muco-obstructive lung diseases.

Photophysical Properties, Fluorescence Quenching of Metformin Hydrochloride by Caffeine, and its Docking with the AMP-activated protein kinase receptor.

In this research, the photophysical properties of metformin hydrochloride (MF-HCl) were studied using spectroscopic and molecular docking techniques. The interaction between metformin hydrochloride and caffeine is essential for understanding the pharmacokinetics of metformin, particularly in populations with high caffeine consumption. Metformin is a first-line medication for managing type 2 diabetes, while caffeine is a widely consumed dietary stimulant. Knowing how caffeine may affect the action of metformin is crucial for effective diabetes management. The spectroscopic techniques results showed that the photophysical properties (fluorescence quantum yields, lifetime, radiative, and non-radiative decay) of the drug are influenced by solvent polarity and drug concentration. The binding mechanism of metformin hydrochloride-caffeine (MF-HCl-CAF) was identified through the fluorescence quenching method. The quenching of drugs induced by caffeine is due to ground state complex formation. The binding occurs due to hydrogen bonds and Van der Waals forces in the reaction. The förster resonance energy transfer (FRET) between metformin hydrochloride and caffeine was also calculated using flourtools.com software. The threshold distance (R0), for 50% energy transfer from metformin hydrochloride to caffeine is 1.81nm and the binding distance (r), between caffeine and the amino acid residue in metformin hydrochloride is 1.55nm. Dynamic light scattering (DLS), Zeta potential, and Fourier transform infrared (FTIR) spectroscopy confirm the conformational change of the drugs, as the caffeine molecule binds to metformin hydrochloride molecules. The molecular docking of metformin hydrochloride with the amp-activated protein kinase receptor (PDB Id: 1z0n) is analyzed. Again the docking of both metformin hydrochloride and caffeine (two ligands) with the protein receptor (PDB Id: 1z0n) was also analyzed and the results agreed with the fluorescence quenching techniques.

Deciphering the Photophysical Properties of Nonplanar Heterocyclic Compounds in Different Polarity Environments.

Nonplanar (butterfly-shaped) phenothiazine (PTZ) and its derivative's (M-PTZ) photophysical and spectral properties have been tuned by varying the solvents and their polarity and investigated employing spectroscopic techniques such as UV-Vis, steady-state and time-resolved fluorescence, and TDDFT calculations. The UV-Vis absorption studies and TDDFT calculations reveal two distinct bands for both compounds: a strong π-π* transition at shorter wavelengths and a weaker n-π* transition, which displays a little bathochromic shift in polar solvents. The detailed emission studies reveal that such dual emission is a result of the photoinduced excited-state conjugation enhancement (ESCE) process. The band at a shorter wavelength corresponds to the locally excited (LE) state, while the longer wavelength band arises from the planarized excited state resulting from ESCE. With the increase in solvent polarity, the LE band is less affected, whereas strong positive solvatochromism is observed for the ESCE band. As the solvent polarity increases, the ESCE band demonstrates significant positive solvatochromism, while emission intensity decreases with higher solvent polarity, suggesting stabilization of the excited state. The biexponential decay of fluorescence lifetimes further corroborates the dual emission behavior of PTZ and M-PTZ. PTZ exhibits a higher photoluminescence quantum yield (PLQY) than that observed for M-PTZ, and the solvent viscosity influences the PLQY, indicating that nonradiative decay is activated during the planarization of the excited state, also known as excited-state conjugation enhancement. Furthermore, the (time-dependent) density functional theory (TD) DFT calculations performed to understand the geometrical parameters and the electronic transitions of these model molecules further corroborate experimental findings. These findings underscore the significant influence of solvent polarity and molecular structure on the dual emission and excited-state dynamics of PTZ and M-PTZ, which eventually hold substantial implications for advanced photophysical applications.

Fluorescence Lifetime Endoscopy with a Nanosecond Time-Gated CAPS Camera with IRF-Free Deep Learning Method.

Fluorescence imaging has been widely used in fields like (pre)clinical imaging and other domains. With advancements in imaging technology and new fluorescent labels, fluorescence lifetime imaging is gradually gaining recognition. Our research department is developing the tauCAMTM, based on the Current-Assisted Photonic Sampler, to achieve real-time fluorescence lifetime imaging in the NIR (700-900 nm) region. Incorporating fluorescence lifetime into endoscopy could further improve the differentiation of malignant and benign cells based on their distinct lifetimes. In this work, the capabilities of an endoscopic lifetime imaging system are demonstrated using a rigid endoscope involving various phantoms and an IRF-free deep learning-based method with only 6-time points. The results show that this application's fluorescence lifetime image has better lifetime uniformity and precision with 6-time points than the conventional methods.

Unveiling Microscopic Variations during Photodynamic Therapy via Polarity-Responsive Fluorescence Lifetime Imaging.

Photodynamic therapy is a highly promising method for cancer adjuvant treatment. However, the current research on the microscopic changes during the photodynamic therapy process is still quite limited, which seriously impedes the deep understanding of the procedure. For this purpose, a novel polarity-responsive probe, MI-PPF, with excellent mitochondrial targeting and anchoring capabilities has been rationally designed and synthesized. Notably, MI-PPF has successfully realized the in situ detection of mitochondrial morphology and polarity alterations during the photodynamic therapy process in cancer cells through fluorescence lifetime imaging. The results showed that a series of phenomena such as deformation, shrinkage, vacuolation, and aggregation occurred in the mitochondrial morphology during photodynamic therapy. Concurrently, a decline in mitochondrial polarity is also noted, which may be closely linked to the mitochondrial oxidative stress response during this process. Furthermore, MI-PPF can be used for photodynamic therapy on tumor mouse models and has successfully achieved fluorescence lifetime imaging of tumor sections before and after photodynamic therapy, uncovering multifaceted changes in cell morphology, polarity, and polarity distribution within the mouse tumor model during the process. It is anticipated that this study will offer valuable insights and guidance to the research of mitochondrial-related fields and will boost the advancement of diagnostic and therapeutic areas for associated diseases.

Rapid Acquisition of High-Pixel Fluorescence Lifetime Images of Living Cells via Image Reconstruction Based on Edge-Preserving Interpolation.

Fluorescence lifetime imaging (FLIM) has established itself as a pivotal tool for investigating biological processes within living cells. However, the extensive imaging duration necessary to accumulate sufficient photons for accurate fluorescence lifetime calculations poses a significant obstacle to achieving high-resolution monitoring of cellular dynamics. In this study, we introduce an image reconstruction method based on the edge-preserving interpolation method (EPIM), which transforms rapidly acquired low-resolution FLIM data into high-pixel images, thereby eliminating the need for extended acquisition times. Specifically, we decouple the grayscale image and the fluorescence lifetime matrix and perform an individual interpolation on each. Following the interpolation of the intensity image, we apply wavelet transformation and adjust the wavelet coefficients according to the image gradients. After the inverse transformation, the original image is obtained and subjected to noise reduction to complete the image reconstruction process. Subsequently, each pixel is pseudo-color-coded based on its intensity and lifetime, preserving both structural and temporal information. We evaluated the performance of the bicubic interpolation method and our image reconstruction approach on fluorescence microspheres and fixed-cell samples, demonstrating their effectiveness in enhancing the quality of lifetime images. By applying these techniques to live-cell imaging, we can successfully obtain high-pixel FLIM images at shortened intervals, facilitating the capture of rapid cellular events.

Absolute measurement of fast and slow neuronal signals with fluorescence lifetime photometry at high temporal resolution.

The concentrations of extracellular and intracellular signaling molecules, such as dopamine and cAMP, change over both fast and slow timescales and impact downstream pathways in a cell-type specific manner. Fluorescence sensors currently used to monitor such signals in vivo are typically optimized to detect fast, relative changes in concentration of the target molecule. They are less well suited to detect slowly-changing signals and rarely provide absolute measurements of either fast and slow signaling components. Here, we developed a system for fluorescence lifetime photometry at high temporal resolution (FLIPR) that utilizes frequency-domain analog processing to measure the absolute fluorescence lifetime of genetically-encoded sensors at high speed but with long-term stability and picosecond precision in freely moving mice. We applied FLIPR to investigate dopamine signaling in two functionally distinct regions in the striatum, the nucleus accumbens core (NAC) and the tail of striatum (TOS). We observed higher tonic dopamine levels at baseline in the TOS compared to the NAC and detected differential and dynamic responses in phasic and tonic dopamine to appetitive and aversive stimuli. Thus, FLIPR enables simple monitoring of fast and slow time-scale neuronal signaling in absolute units, revealing previously unappreciated spatial and temporal variation even in well-studied signaling systems.

Fluorescence Lifetime Imaging of NAD(P)H in Patients’ Lymphocytes: Evaluation of Efficacy of Immunotherapy

Background: The wide variability in clinical responses to anti-tumor immunotherapy drives the search for personalized strategies. One of the promising approaches is drug screening using patient-derived models composed of tumor and immune cells. In this regard, the selection of an appropriate in vitro model and the choice of cellular response assay are critical for reliable predictions. Fluorescence lifetime imaging microscopy (FLIM) is a powerful, non-destructive tool that enables direct monitoring of cellular metabolism on a label-free basis with a potential to resolve metabolic rearrangements in immune cells associated with their reactivity. Objective: The aim of the study was to develop a patient-derived glioma explant model enriched by autologous peripheral lymphocytes and explore FLIM of the redox-cofactor NAD(P)H in living lymphocytes to measure the responses of the model to immune checkpoint inhibitors. Methods: The light microscopy, FLIM of NAD(P)H and flow cytometry were used. Results: The results demonstrate that the responsive models displayed a significant increase in the free NAD(P)H fraction α1 after treatment, associated with a shift towards glycolysis due to lymphocyte activation. The non-responsive models exhibited no alterations or a decrease in the NAD(P)H α1 after treatment. The FLIM data correlated well with the standard assays of immunotherapy drug response in vitro, including morphological changes, the T-cells activation marker CD69, and the tumor cell proliferation index Ki67. Conclusions: The proposed platform that includes tumor explants co-cultured with lymphocytes and the NAD(P)H FLIM assay represents a promising solution for the patient-specific immunotherapeutic drug screening.

Targeted NIR Fluorescent Mechanically Interlocked Molecules-Peptide Bioconjugate for Live Cancer Cells Submitochondrial Stimulated Emission Depletion Super-Resolution Microscopy.

Herein, a water-soluble, ultrabright, near-infrared (NIR) fluorescent, mechanically interlocked molecules (MIMs)-peptide bioconjugate is designed with dual targeting capabilities. Cancer cell surface overexpressed αVβ3 integrin targeting two RGDS tetrapeptide residues is tethered at the macrocycle of MIMs-peptide bioconjugate via Cu(I)-catalyzed click chemistry on the Wang resin, and mitochondria targeting lipophilic cationic TPP+ functionality is conjugated at the axle dye. Living carcinoma cell selective active targeting, subsequently cell penetration, mitochondrial imaging, including the ultrastructure of cristae, and real-time tracking of malignant mitochondria by MIMs-peptide bioconjugate (RGDS)2-Mito-MIMs-TPP+ are established by stimulated emission depletion (STED) super-resolved fluorescence microscopy. Water-soluble NIR (RGDS)2-Mito-MIMs-TPP+ is an effective class of MIMs-peptide bioconjugate with promising photophysics; for instance, remarkable photostability and thermal stability, strong and narrow NIR abs/em bands with high quantum yield, ultrabrightness, decent fluorescence lifetime, reasonable stability against cellular nucleophiles, biocompatibility, noncytotoxicity, and dual-targeted living cancer cell submitochondrial imaging ability are all indispensable criteria for targeted super-resolved STED microscopy.

Towards measurements of absolute membrane potential in Bacillus subtilis using fluorescence lifetime.

Membrane potential (MP) changes can provide a simple readout of bacterial functional and metabolic state or stress levels. While several optical methods exist for measuring fast changes in MP in excitable cells, there is a dearth of such methods for absolute and precise measurements of steady-state membrane potentials (MPs) in bacterial cells. Conventional electrode-based methods for the measurement of MP are not suitable for calibrating optical methods in small bacterial cells. While optical measurement based on Nernstian indicators have been successfully used, they do not provide absolute or precise quantification of MP or its changes. We present a novel, calibrated MP recording approach to address this gap. In this study, we used a fluorescence lifetime-based approach to obtain a single-cell resolved distribution of the membrane potential and its changes upon extracellular chemical perturbation in a population of bacterial cells for the first time. Our method is based on (i) a unique VoltageFluor (VF) optical transducer, whose fluorescence lifetime varies as a function of MP via photoinduced electron transfer (PeT) and (ii) a quantitative phasor-FLIM analysis for high-throughput readout. This method allows MP changes to be easily visualized, recorded and quantified. By artificially modulating potassium concentration gradients across the membrane using an ionophore, we have obtained a Bacillus subtilis-specific MP versus VF lifetime calibration and estimated the MP for unperturbed B. subtilis cells to be -65 mV (in MSgg), -127 mV (in M9) and that for chemically depolarized cells as -14 mV (in MSgg). We observed a population level MP heterogeneity of ∼6-10 mV indicating a considerable degree of diversity of physiological and metabolic states among individual cells. Our work paves the way for deeper insights into bacterial electrophysiology and bioelectricity research.

Transferrin Modified Gold Nanoclusters-Based Biosensing Nanoplatform for High-Precision Multimodal Bioimaging of Tumor Cells.

Bioimaging technology has been broadly used in biomedicine, and the growth of multimodal imaging technology based on synergistic advantages can overcome the shortcomings of traditional single-modal bioimaging methods and attain high specificity and sensitivity in the fields of bioimaging and biosensing. The analysis of low-abundance microRNAs (miRNAs) in complex organisms is of high importance for early-stage diagnosis and clinical treatment of tumors. In our current study, a biosensing nanoplatform based on Tf-AuNCs and MnO2 nanosheets was developed for multimodal imaging of tumor cells. First, oxidizable MnO2 nanosheets provided a smart tool for use as nanocarriers and contrast agents for intracellular glutathione (GSH)-activated magnetic resonance imaging (MRI). Then, MnO2 nanosheets delivered Tf-AuNC-based biosensing nanoplatforms into cells through endocytosis. Endogenous GSH degraded MnO2 nanosheets into Mn2+, and the released functional nucleic acid probes can perform specific biosensing responses to miR-21 exhibiting multimodal imaging including two-photon near-infrared fluorescence imaging (TP-NIRFI), fluorescence lifetime imaging (FLIM), and MRI. Finally, the biosensing nanoplatform achieved satisfactory results in tumor cells and tissues by TP-NIRFI (300.0 μm penetration depth), FLIM (τ ≈ 50.0 ns), and MRI. Therefore, biosensing nanoplatforms based on Tf-AuNCs and MnO2 nanosheets show great potential for multimodal detection and imaging in tumor cells.

Histamine N-methyltransferase (HNMT) as a potential auxiliary biomarker for predicting adaptability to anti-HER2 drug treatment in breast cancer patients

BackgroundUp to 23% of breast cancer patients recurred within a decade after trastuzumab treatment. Conversely, one trial found that patients with low HER2 expression and metastatic breast cancer had a positive response to trastuzumab-deruxtecan (T-Dxd). This indicates that relying solely on HER2 as a single diagnostic marker to predict the efficacy of anti-HER2 drugs is insufficient. This study highlights the interaction between histamine N-methyltransferase (HNMT) and HER2 as an adjunct predictor for trastuzumab response. Furthermore, modulation of HER2 expression by HNMT may explain why those with low HER2 expression still respond to T-Dxd.MethodsWe investigated the impact of HNMT protein expression on the efficacy of anti-HER2 therapy in both in vivo and ex vivo models of patient-derived xenografts and cell line-derived xenografts. Our analysis included Förster resonance energy transfer (FRET) to assess the interaction strength between HNMT and HER2 proteins in trastuzumab-resistant and sensitive tumor tissues. Additionally, we used fluorescence lifetime imaging microscopy (FLIM), cleaved luciferase, and immunoprecipitation to study the interaction dynamics of HNMT and HER2. Furthermore, we evaluated the influence of HNMT activity on the binding of anti-HER2 antibodies to their targets through flow cytometry. We also observed the nuclear translocation of HNMT/HER2-ICD cells using fluorescent double staining and DeltaVision microscopy. Finally, ChIP sequencing was employed to identify target genes affected by the HNMT/HER2-ICD complex.ResultsThis study highlights HNMT as a potential auxiliary biomarker for diagnosing HER2 + breast cancer. FRET analysis demonstrated a significant interaction between HNMT and HER2 protein in trastuzumab-sensitive tumor tissue (n = 50), suggesting the potential of HNMT as a predictor of treatment response. Mechanistic studies revealed that the interaction between HNMT and HER2 contributes to increased HER2 protein expression at the transcriptional level, thereby impacting the efficacy of anti-HER2 therapy. Furthermore, a subset of triple-negative breast cancers characterized by HNMT overexpression was found to be sensitive to HER2 antibody–drug conjugates such as T-Dxd.ConclusionsThese findings offer crucial insights for clinicians evaluating candidates for anti-HER2 therapy, especially for HER2-low breast cancer patients who could gain from T-Dxd treatment. Identifying HNMT expression could help clinicians pinpoint patients who would benefit from anti-HER2 therapy.

Rationalizing Photophysics of Co(III) Complexes with Pendant Pyrene Moieties.

Pendant organic chromophores have been used to improve the photocatalytic performance of many metal-based photosensitizers, particularly in first-row metals, by increasing π conjugation in ligands and lowering the energy of the photoactive absorption band. Using a combination of spectroscopic studies and computational modeling, we rationalize the excited state dynamics of a Co(III) complex containing pendant pyrene moieties, CoL1, where L1 = 1,1'-(4-(pyren-1-yl)pyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium). CoL1 displays higher visible absorptivity, and blue luminescence from pyrene singlet excited states compared with CoL0 [L0 = 1,1'-(pyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium)] in which the pyrene moiety is absent. Emissive properties are highly influenced by the metal center, reducing the fluorescence lifetime from 5.9 to 3.5 ns, and a blue shift of 43 nm. The lower energy of the d orbitals in Co(III) compared with Fe(II) drastically affects the character of the excited state, resulting in a mixture of singlet intraligand charge-transfer (1ILCT) and ligand-to-metal charge-transfer (1LMCT) character. Transient absorption experiments revealed that although the dark triplet intraligand pyrene (3ILPyrene) state is present, it is not efficiently populated and possesses a short nanosecond-scale lifetime. Instead, triplet metal-centered (3MC) states dominate the decay path with a 2.4 ps lifetime, no photoactivity toward singlet oxygen formation or triplet-triplet energy transfer (TTET). This work shows how various factors can influence excited-state dynamics.

Delocalized Nonbonding Orbitals of Thioxanthone in Polycyclic Aromatic Hydrocarbons for Reduced Energy Gap and Narrowband Emission.

Chalcogen-containing carbonyls, specifically thioxanthone (TX), hold great potential in organic light-emitting diodes (OLEDs). While the development of narrowband OLEDs with chalcogen-containing carbonyls remains challenging due to difficulties in achieving both high device efficiency and narrow emission spectra. Herein, via a strategic incorporation of the TX moiety, two orange-red narrowband emitters, 2TXBN and BNTXBN, are designed and synthesized for the first time. Both 2TXBN and BNTXBN exhibit bright orange-red emissions with peaks at 582 and 585 nm, respectively, along with narrow full widths at half maximum of 30 and 32 nm. Notably, 2TXBN demonstrates delocalization of the nonbonding orbital within the TX segment, which raises the first triplet energy level and reduces the singlet-triplet energy gap. This electronic structural adjustment effectively shortens the delayed fluorescence lifetime, leading to enhanced device performance. Accordingly, OLED employing 2TXBN as the emitter achieves remarkable performance, with a maximum external quantum efficiency of 31.0%, a current efficiency of 69.0 cd A-1, and a power efficiency of 76.0 lm W-1, highlighting the efficacy of the nonbonding orbital delocalization strategy in achieving bathochromic-shifted narrowband OLED materials.