Planar-structured thiadiazoloquinoxaline-based NIR-II dye for tumor phototheranostics.

Second near-infrared (NIR-II) fluorescence imaging shows huge application prospects in clinical disease diagnosis and surgical navigation, while it is still a big challenge to exploit high performance NIR-II dyes with long-wavelength absorption and high fluorescence quantum yield. Herein, based on planar π-conjugated donor-acceptor-donor systems, three NIR-II dyes (TP-DBBT, TP-TQ1, and TP-TQ2) were synthesized with bulk steric hindrance, and the influence of acceptor engineering on absorption/emission wavelengths, fluorescence efficiency and photothermal properties was systematically investigated. Compared with TP-DBBT and TP-TQ2, the TP-TQ1 based on 6,7-diphenyl-[1,2,5]thiadiazoloquinoxaline can well balance absorption/emission wavelengths, NIR-II fluorescence brightness and photothermal effects. And the TP-TQ1 nanoparticles (NPs) possess high absorption ability at a peak absorption of 877 nm, with a high relative quantum yield of 0.69% for large steric hindrance hampering the close π-π stacking interactions. Furthermore, the TP-TQ1 NPs show a desirable photothermal conversion efficiency of 48% and good compatibility. In vivo experiments demonstrate that the TP-TQ1 NPs can serve as a versatile theranostic agent for NIR-II fluorescence/photoacoustic imaging-guided tumor phototherapy. The molecular planarization strategy provides an approach for designing efficient NIR-II fluorophores with extending absorption/emission wavelength, high fluorescence brightness, and outstanding phototheranostic performance.

Tumor-Targeted Squaraine Dye for Near-Infrared Fluorescence-Guided Photodynamic Therapy.

Many efforts have been made to develop near-infrared (NIR) fluorescent dyes with high efficiency for the NIR laser-induced phototherapy of cancer. However, the low tumor targetability and high nonspecific tissue uptake of NIR dyes in vivo limit their applications in preclinical cancer imaging and therapy. Among the various NIR dyes, squaraine (SQ) dyes are widely used due to their high molar extinction coefficient, intense fluorescence, and excellent photostability. Previously, benzoindole-derived SQ (BSQ) was prepared by incorporating carboxypentyl benzoindolium end groups into a classical SQ backbone, followed by conjugating with cyclic RGD peptides for tumor-targeted imaging. In this study, we demonstrate that the structure-inherent tumor-targeting BSQ not only shows a high fluorescence quantum yield in serum but also exhibits superior reactive oxygen species (ROS) generation capability under the 671 nm laser irradiation for effective photodynamic therapy (PDT) in vitro and in vivo. Without targeting ligands, the BSQ was preferentially accumulated in tumor tissue 24 h post-injection, which was the optimal timing of the laser irradiation to induce increments of ROS production. Therefore, this work provides a promising strategy for the development of photodynamic therapeutic SQ dyes for targeted cancer therapy.

Mitochondria-targeted BODIPY dyes for small molecule recognition, bio-imaging and photodynamic therapy.

Mitochondria are essential for a diverse array of biological functions. There is increasing research focus on developing efficient tools for mitochondria-targeted detection and treatment. BODIPY dyes, known for their structural versatility and excellent spectroscopic properties, are being actively explored in this context. Numerous studies have focused on developing innovative BODIPYs that utilize optical signals for imaging mitochondria. This review presents a comprehensive overview of the progress made in this field, aiming to investigate mitochondria-related biological events. It covers key factors such as design strategies, spectroscopic properties, and cytotoxicity, as well as mechanism to facilitate their future application in organelle imaging and targeted therapy. This work is anticipated to provide valuable insights for guiding future development and facilitating further investigation into mitochondria-related biological sensing and phototherapy.

Novel fluorescent probes based on sulfur and nitrogen co-doped carbon dots for determination of three N-substituted phenothiazine derivatives in dosage forms.

In the current work, sulfur and nitrogen co-doped carbon dots (S,N-CDs) as simple, sensitive, and selective turn-off fluorescent nanosensors were utilized for analysis of three phenothiazine derivatives, including acetophenazine (APZ), chlorpromazine (CPH), and promethazine (PZH). S,N-CDs were synthesized through a green one-pot microwave-assisted technique using widely available precursors (thiourea and ascorbic acid). HRTEM, EDX, FTIR spectroscopy, UV-Vis absorption spectroscopy, and fluorescence spectroscopy were used to characterize the as-synthesized CDs. When excited at 330 nm, the carbon dots produced a maximum emission peak at 410 nm. The cited drugs statically quenched the S,N-CDs fluorescence as revealed by the Stern-Volmer equation. The current method represents the first spectrofluorimetric approach for the determination of the studied drugs without the need for chemical derivatization or harsh reaction conditions. The importance of the proposed work is magnified as the cited drugs do not have any fluorescent properties. The fluorescence of the developed sensor exhibited a linear response to APZ, CPH, and PZH in the concentration ranges of 5.0-100.0, 10.0-100.0, and 10.0-200.0 µM with detection limits of 1.53, 1.66, and 2.47 µM, respectively. The developed fluorescent probes have the advantages of rapidity and selectivity for APZ, CPH, and PZH analysis in tablets with acceptable % recoveries of (98.06-101.66 %). Evaluation of the method's greenness was performed using the Complementary Green Analytical Procedure Index (ComplexGAPI) and Analytical GREEnness metric (AGREE) metrics, indicating that the method is environmentally friendly. Validation of the proposed method was performed according to ICHQ2 (R1) guidelines.

Detection of CD40 Protein-Umbelliferone Interaction via Differential Scanning Fluorescence.

The investigation of interactions between different molecules is a crucial aspect of understanding disease pathogenesis and screening for drug targets. Umbelliferone, an active ingredient in Tibetan medicine Vicatia thibetica, exhibits an immunomodulatory effect with an unknown mechanism. The CD40 protein is a key target in the immune response. Therefore, this study employs the principle of differential scanning fluorescence technology to analyze the interactions between CD40 protein and umbelliferone using fluorescent enzyme markers. Initially, the stability of the protein fluorescent orange dye was experimentally verified, and the optimal dilution ratio of 1:500 was determined. Subsequently, it was observed that the temperature melting (Tm) value of CD40 protein tended to decrease with an increase in concentration. Interestingly, the interaction between CD40 protein and umbelliferone was found to enhance the thermal stability of CD40 protein. This study represents the first attempt to detect the binding potential of small molecule compounds and proteins using fluorescence microplates and fluorescent dyes. The technique is characterized by high sensitivity and accuracy, promising advancements in the fields of protein stability, protein structure, and protein-ligand interactions, thus facilitating further research and exploration.

A fluorescence ionic probe utilizing Cu2+ assisted competition for detecting glyphosate abused in green tea.

Food fraud caused by the violation of glyphosate use in tea is frequently exposed, posing a potential health risk to consumers and undermining trust in food safety. In the work, an ionic fluorescent probe "[P66614] [4HQCA]-Cu2+ (PHQCA-Cu2+)" was constructed using Cu2+ and ionic liquids coordination through a competitive coordination strategy to detect glyphosate. This probe exhibited a prominent "turn-on" fluorescence response in glyphosate detection. PHQCA-Cu2+was destroyed by glyphosate with its strong coordination capability, and a new complex re-formed simultaneously between glyphosate and the Cu2+ in it, where Cu2+ served as an "invisible indicator" influencing fluorescence changes. Remarkably, PHQCA-Cu2+formed rapidly within 5 s, demonstrated exceptional sensitivity and selectivity, and satisfactory detection performance on paper strips impregnated withPHQCA-Cu2+.Importantly,PHQCA-Cu2+showed excellent recoveries in various green tea, which offered a viable method for identifying contaminated products from the supply chain quickly to enhance overall food safety surveillance.

High enrichment and sensitive measurement of oxytetracycline in tea drinks by thermosensitive magnetic molecular imprinting based magnetic solid phase extraction coupled with boron doped carbon dots.

As a typical kind of new pollutants, there are still some challenges in the rapid detection of antibiotics. In this work, a sensitive fluorescent probe based on boron-doped carbon dots (B-CDs) in combination with thermo-responsive magnetic molecularly imprinted polymers (T-MMIPs) was constructed for the detection of oxytetracycline (OTC) in tea drinks. T-MMIPs were designed, fabricated and employed to enrich OTC at trace level from tea drinks, and B-CDs were utilized as the fluorescent probe to detect the concentration of OTC. The proposed method exhibited good linear relationship with OTC concentration from 0.2 to 60 µg L-1 and the limit of detection was 0.1 µg L-1. The established method has been successfully validated with tea beverages. Present work was the first attempt application of T-MMIPs in combination with CDs in detection of OTC, and demonstrated that the proposed method endowed the detection of OTC with high selectivity, sensitivity, reliability and wide application prospect, meanwhile offered a new strategy for the method establishment of rapid and sensitive detection of trace antibiotics in food and other matrices.

One-pot, one-step, label-free miRNA detection method based on the structural transition of dumbbell probe.

In this study, we present a one-pot, one-step, label-free miRNA detection method through a structural transition of a specially designed dumbbell-shape probe, initiating a rolling circle transition (RCT). In principle, target miRNA binds to right loop of the dumbbell probe (DP), which allows structural change of the DP to circular form, exposing a sequence complementary to the T7 promoter (T7p) previously hidden within the stem. This exposure allows T7 RNA polymerase to initiate RCT, producing a repetitive Mango aptamer sequence. TO1-biotin, fluorescent dye, binds to the aptamer, inducing a detectable enhancement of fluorescence intensity. Without miR-141, the DP stays closed, RCT is prevented, and the fluorescence intensity remains low. By employing this novel strategy, target miRNA was successfully identified with a detection of 73 pM and a dynamic linear range of 0-10 nM. Additionally, the method developed enables one-pot, one-step, and label-free detection of miRNA, demonstrating potential for point-of-care testing (POCT) applications. Furthermore, the practical application of the designed technique was demonstrated by reliably detecting the target miRNA in the human serum sample. We also believe that the conceived approach could be widely used to detect not only miRNAs but also diverse biomolecules by simply replacing the detection probe.

Ginseng root extract-mediated synthesis of monodisperse silver nanoparticles as a fluorescent probe for the spectrofluorometric determination of nilvadipine; Evaluation of remarkable anti-bacterial, anti-fungal and in-vitro cytotoxic activities.

Nanoparticles are a boon for humanity because of their improved functionality and unlimited potential applications. Considering this significance, the proposed study introduced a simple, fast and eco-friendly method for synthesis of fluorescent silver nanoparticles (Ag-NPs) using Panax Ginseng root extract as a reducing and capping agent. Synthesis of Ag-NPs was performed in one step within three minutes utilizing microwave irradiation. The resulting Ag-NPs were characterized using various microscopic and spectroscopic techniques such as, Transmission Electron Microscope (TEM), UV/Visible spectroscopy, Fourier Transform Infrared Spectroscopy(FTIR) and Energy Dispersive X-ray analysis (EDX). The prepared Ag-NPs, which act as a fluorescent nano-probe with an emission band at 416 nm after excitation at 331 nm, were used to assay nilvadipine (NLV) spectrofluorimetrically in its pharmaceutical dosage form with good sensitivity and reproducibility. The proposed study is based on the ability of NLV to quantitatively quench the native Ag-NPs fluorescence, forming a ground state complex as a result of static quenching and an inner filter mechanism. The suggested approach displayed a satisfactory linear relationship throughout a concentration range of 5.0 µM - 100.0 µM, with LOD and LOQ values of 1.18 µM and 3.57 µM, respectively. Validation of the suggested approach was examined in accordance with ICH recommendations. In addition, the anti-bacterial and anti-fungal activities of the prepared nanoparticles were investigated, and they demonstrated effective anti-microbial activities and opened a future prospective to combat future antibiotic resistance. Finally, in-vitro cytotoxicity assay of Ag-NPs against normal and cancerous human cell lines was studied using MTT assay. The results proved the potential use of the produced Ag-NPs as an adjunct to anticancer treatment or for drug delivery without significantly harming healthy human cells.

BODIPY-Based Analogue of the TREM2-Binding Molecular Adjuvant Sulfavant A, a Chemical Tool for Imaging and Tracking Biological Systems.

Recently, we described synthetic sulfolipids named Sulfavants as a novel class of molecular adjuvants based on the sulfoquinovosyl-diacylglycerol skeleton. The members of this family, Sulfavant A (1), Sulfavant R (2), and Sulfavant S (3), showed important effects on triggering receptor expressed on myeloid cells 2 (TREM2)-induced differentiation and maturation of human dendritic cells (hDC), through a novel cell mechanism underlying the regulation of the immune response. As these molecules are involved in biological TREM2-mediated processes crucial for cell survival, here, we report the synthesis and application of a fluorescent analogue of Sulfavant A bearing the 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene moiety (Me4-BODIPY). The fluorescent derivative, named PB-SULF A (4), preserving the biological activity of Sulfavants, opens the way to chemical biology and cell biology experiments to better understand the interactions with cellular and in vivo organ targets and to improve our comprehension of complex molecular mechanisms underlying the not fully understood ligand-induced TREM2 activity.

Rapid identification of Radix Astragali origin by using fluorescence probe combined with chemometrics.

Fluorescent probes for metal ion recognition can be divided into selective probes, weakly selective probes, and non-selective probes roughly. Weakly selective probes are not often used for quantitative analysis of metal ions due to their overlapping spectra resulting from simultaneous interactions with multiple metal ions. Conversely, the different metal ions contained in herbal medicine extracts from different geographical origins will produce corresponding fluorescence fingerprint profiles after interaction with weakly selective fluorescence probes. The performance can be used in the study of origin tracing of food or Chinese herbal medicine. Weakly selective fluorescent probes of benzimidazole derivatives have been synthesized and attempted to be used in the origin tracing of Radix Astragali in this work. Radix Astragali from different origins will produce different fluorescence fingerprint spectra due to the difference of metal ions and content in combination with the probe. Excitation-emission matrix (EEM) fluorescence spectroscopy in conjunction with N-way partial least squares discriminant analysis (N-PLS-DA), and unfolded partial least squares discriminant analysis (U-PLS-DA) were used to identify the origin of 150 Radix Astragali samples from five geographical origins. The prediction results showed that the correct recognition rates of the U-PLS-DA model and N-PLS-DA model are 95.92% and 93.88%, respectively. In comparison, the results of U-PLS-DA are slightly better than those of N-PLS-DA. These findings indicate that EEM fluorescence spectroscopy based on weakly selective fluorescent probes combined with multi-way chemometrics provides a good idea for the origin tracing of traditional Chinese medicine.

D-A-D organic fluorescent probes for NIR-II fluorescence imaging and efficient photothermal therapy of breast cancer.

Near-infrared second region (NIR-II) fluorescent probes are used in the diagnosis of early cancer due to their high tissue penetration. However, there are still few reports on organic small molecule fluorescent probes with NIR-II fluorescence imaging (NIR-II FI) combined with efficient photothermal therapy (PTT). In this study, planar cyclopentadithiophene (CPDT) was incorporated into the twisted structural skeleton (D-A-D), and the strong acceptor TTQ molecule (A) and the donor triphenylamine (D) were introduced to synthesize an organic small molecule (TCT) with enhanced NIR-II fluorescence emission performance. To improve the hydrophilicity of TCT molecules, we used the nanoprecipitation method to coat DSPE-mPEG2000 on the TCT molecules and obtained nanoparticles (TCT-NPs) with a strong absorption band, good water dispersibility, and NIR-II FI ability, which realized NIR-II FI-guided PTT for breast cancer tumors. Due to their effective near-infrared absorption, TCT-NPs exhibit high photothermal conversion efficiency (η = 40.1%) under 660 nm laser irradiation, making them a photothermal therapeutic agent with good performance. Therefore, TCT-NPs have the potential to diagnose, eliminate, and monitor the diffusion of cancer.

Azide-modified corrole phosphorus complexes for endoplasmic reticulum-targeted fluorescence bioimaging and effective cancer photodynamic therapy.

Study on corrole photosensitizers (PSs) for photodynamic therapy (PDT) has made remarkable progress. Targeted delivery of PSs is of great significance for enhancing therapeutic efficiency, decreasing the dosage, and reducing systemic toxicity during PDT. The development of PSs that can be specifically delivered to the subcellular organelle is still an attractive and challenging work. Herein, we synthesize a series of azide-modified corrole phosphorus and gallium complex PSs, in which phosphorus corrole 2-P could not only precisely target the endoplasmic reticulum (ER) with a Pearson correlation coefficient (PCC) up to 0.92 but also possesses the highest singlet oxygen quantum yields (ΦΔ = 0.75). This renders it remarkable PDT activity at a very low dosage (IC50 = 23 nM) towards HepG2 tumor cell line while ablating solid tumors in vivo with excellent biosecurity. Furthermore, 2-P exhibits intense red fluorescence (ΦF = 0.25), outstanding photostability, and a large Stokes shift (190 nm), making it a promising fluorescent probe for ER. This study provides a clinically potential photosensitizer for cancer photodynamic therapy and a promising ER fluorescent probe for bioimaging.

Development of Human Serum Albumin Fluorescent Probes in Detection, Imaging, and Disease Therapy.

Human serum albumin (HSA) acts as a repository and transporter of substances in the blood. An abnormal concentration may indicate the occurrence of liver- and kidney-related diseases, which has attracted people to investigate the precise quantification of HSA in body fluids. Fluorescent probes can combine with HSA covalently or noncovalently to quantify HSA in urine and plasma. Moreover, probes combined with HSA can improve its photophysical properties; probe-HSA has been applied in real-time monitoring and photothermal and photodynamic therapy in vivo. This Review will introduce fluorescent probes for quantitative HSA according to the three reaction mechanisms of spatial structure, enzymatic reaction, and self-assembly and systematically introduce the application of probes combined with HSA in disease imaging and phototherapy. It will help develop multifunctional applications for HSA probes and provide assistance in the early diagnosis and treatment of diseases.

Benzobisthiadiazole-Based Small Molecular Near-Infrared-II Fluorophores: From Molecular Engineering to Nanophototheranostics.

Organic fluorescent molecules with emission in the second near-infrared (NIR-II) biological window have aroused increasing investigation in cancer phototheranostics. Among these studies, Benzobisthiadiazole (BBT), with high electron affinity, is widely utilized as the electron acceptor in constructing donor-acceptor-donor (D-A-D) structured fluorophores with intensive near-infrared (NIR) absorption and NIR-II fluorescence. Until now, numerous BBT-based NIR-II dyes have been employed in tumor phototheranostics due to their exceptional structure tunability, biocompatibility, and photophysical properties. This review systematically overviews the research progress of BBT-based small molecular NIR-II dyes and focuses on molecule design and bioapplications. First, the molecular engineering strategies to fine-tune the photophysical properties in constructing the high-performance BBT-based NIR-II fluorophores are discussed in detail. Then, their biological applications in optical imaging and phototherapy are highlighted. Finally, the current challenges and future prospects of BBT-based NIR-II fluorescent dyes are also summarized. This review is believed to significantly promote the further progress of BBT-derived NIR-II fluorophores for cancer phototheranostics.

Dual/Multi-Modal Image-Guided Diagnosis and Therapy Based on Luminogens with Aggregation-Induced Emission.

The combination of multiple imaging methods has made an indelible contribution to the diagnosis, surgical navigation, treatment, and prognostic evaluation of various diseases. Due to the unique advantages of luminogens with aggregation-induced emission (AIE), their progress has been significant in the field of organic fluorescent contrast agents. Herein, this manuscript summarizes the recent advancements in AIE molecules as contrast agents for optical image-based dual/multi-modal imaging. We particularly focus on the exceptional properties of each material and the corresponding application in the diagnosis and treatment of diseases.

Electrochemical Diselenation of BODIPY Fluorophores for Bioimaging Applications and Sensitization of 1 O2.

We report a rapid, efficient, and scope-extensive approach for the late-stage electrochemical diselenation of BODIPYs. Photophysical analyses reveal red-shifted absorption - corroborated by TD-DFT and DLPNO-STEOM-CCSD computations - and color-tunable emission with large Stokes shifts in the selenium-containing derivatives compared to their precursors. In addition, due to the presence of the heavy Se atoms, competitive ISC generates triplet states which sensitize 1 O2 and display phosphorescence in PMMA films at RT and in a frozen glass matrix at 77 K. Importantly, the selenium-containing BODIPYs demonstrate the ability to selectively stain lipid droplets, exhibiting distinct fluorescence in both green and red channels. This work highlights the potential of electrochemistry as an efficient method for synthesizing unique emission-tunable fluorophores with broad-ranging applications in bioimaging and related fields.

A ratiometric fluorescence assay for the detection of DNA methylation based on an alkaline phosphatase triggered in situ fluorogenic reaction.

The accurate and sensitive quantification of DNA methylation is significant for the early diagnosis of cancer. In this work, an alkaline phosphatase (ALP) triggered in situ fluorogenic reaction between ascorbic acid (AA) and 2,3-DAN was employed as a ratiometric fluorescent probe for the accurate and sensitive detection of DNA methylation with the assistance of ALP encapsulated liposomes. The quinoxaline derivative with a yellow fluorescence emission (I525) was generated from the reaction between AA and 2,3-DAN. Meanwhile, the consumption of 2,3-DAN declined its fluorescence intensity (I386). A ratiometric fluorescent probe (I525/I386) constructed by the above in situ fluorogenic reaction was applied for the accurate detection of DNA methylation. The methylated DNA was first captured by its complementary DNA in 96-well plates. Then, 5mC antibody (Ab) linked liposomes that were encapsulated with ALP recognized and combined with the methylation sites of the target DNA. After the liposomes were lysed by Triton X-100, the released ALP triggered the hydrolysis of ascorbic acid diphosphate (AAP) to form AA, participating in the fluorogenic reaction with 2,3-DAN to produce a quinoxaline derivative. Thus, the ratiometric fluorescence detection of DNA methylation was achieved using I525/I386 values. Using the ALP-enzyme catalyzed reaction and liposomes as signal amplifiers, a low detection limit of 82 fM was obtained for DNA methylation detection. Moreover, the accuracy of the assay could be improved using ratiometric fluorescent probes. We hope that the proposed assay will pave a new way for the accurate determination of low-abundance biomarkers.

Development and Validation of a Fluorogenic Probe for Lysosomal Zinc Release.

Zinc homeostasis, which allows optimal zinc utilization in diverse life processes, is responsible for the general well-being of human beings. This paper describes developing and validating an easily accessible indole-containing zinc-specific probe in the cellular milieu. The probe was synthesized from readily available starting materials and was subjected to steady-state fluorescence studies. It showed selective sensing behavior towards Zn2+ with reversible binding. The suppression of PET (Photoinduced Electron Transfer) and ESIPT (Excited State Intramolecular Proton Transfer) elicited selectivity, and the detection limit was 0.63 µM (LOQ 6.8 µM). The zinc sensing capability of the probe was also screened in the presence of low molecular weight ligands [LMWLs] and showed interference only with GSH and ATP. It is non-toxic and can detect zinc in different cell lines under various stress conditions such as inflammation, hyperglycemia, and apoptosis. The probe could stain the early and late stages of apoptosis in PAN-2 cells by monitoring the zinc release. Most experiments were conducted without external zinc supplementation, showing its innate ability to detect zinc.

J-Aggregation induced NIR-II fluorescence: an aza-BODIPY luminogen for efficient phototheranostics.

The development of organic dyes with emission peaks in the second near-infrared window (NIR-II 1000-1700 nm) is highly desirable for in vivo imaging and imaging-guided phototheranostics. However, the lack of appropriate molecular frameworks and the challenges associated with complex synthesis critically hinder the development of new candidate fluorophores. J-Aggregation is considered as a smart and straightforward way to construct such a therapeutic agent with NIR-II fluorescence imaging properties. Here, we present the design and synthesis of an aza-BODIPY probe (TA). Upon encapsulation within the amphiphilic polymer DSPEG-PEG2000-NH2, TA underwent self-assembly and formed J-aggregates (TAJ NPs), which showed emission at 1020 nm. High spatial resolution and adequate signal-to-noise ratio of the TAJ NPs are demonstrated for noninvasive bioimaging of the vasculature, lymph nodes and bones of mice in the NIR-II region. Moreover, the TAJ NPs exhibited good tumor enrichment efficiency with reduced liver accumulation and significant imaging-guided phototherapy performance against lung cancer cells. Taken together, this work not only introduces a new NIR-II imaging and phototheranostic agent based on J-aggregates, but also provides insight into the development of versatile organic dyes for future clinical implementation.