Research progress of near-infrared fluorescence probes based on indole heptamethine cyanine dyes in vivo and in vitro

Polymeric nanomaterials encapsulating fluorescent polyindole-nido- carborane: design, synthesis and biological evaluation

The water-soluble nido-carborane was prepared by alkali treatment of o-carborane. A polymer PInd containing a polyindole structure was synthesized and employed to label the modified o-carborane. Subsequently, four polymeric nanomaterials were synthesized with the objective of encapsulating them in order to enhance its bioavailability. The experimental results showed that the fluorescent complex encapsulated by the pH-sensitive polymer A had the best UV absorption and fluorescence intensity, and thus A-PInd-C was chosen for subsequent experiments. The Transmission electron microscopy images revealed that the compounds exhibited a rounded internal morphology, with the layers exhibiting a tightly stacked arrangement. The AFM imaging revealed that the surface of the sample exhibited a relatively uniform and smooth appearance. In vitro release experiments conducted under acidic conditions demonstrated that A-PInd-C was released in a predominantly linear manner, with a maximum release rate of 80% observed within 48 h. Cellular imaging experiments showed that the compound could enter HeLa and HCT-116 cells and was mainly distributed around the nucleus, especially in the acidic environment. The results of the cell proliferation toxicity experiments demonstrated that A-PInd-C exhibited inhibitory effects on HeLa, PC-3 and L02 cells. Among these, the inhibitory effect on PC-3 cells was the most pronounced, reaching up to 70%. In conclusion, this paper solves the problem of poor bioavailability of carborane by improving the boron containing compounds and also makes the system have potential for Boron neutron capture therapy.

Recent Advances in Organic Small-Molecule Fluorescent Probes Based on Dicyanoisophorone Derivatives

Fluorescent probe technology holds great promise in the fields of environmental monitoring and clinical diagnosis due to its inherent advantages, including easy operation, reliable detection signals, fast analysis speed, and in situ imaging capabilities. In recent years, a wide range of fluorescent probes based on diverse fluorophores have been developed for the analysis and detection of various analytes, yielding significant achievement. Among these fluorophores, the dicyanoisophorone-based fluorophores have garnered significant attention. Dicyanoisoporone exhibits minimal fluorescence, yet possesses a robust electron-withdrawing capability, rendering it suitable for constructing of D-π-A structured fluorophores. Leveraging the intramolecular charge transfer (ICT) effect, such fluorophores exhibit near-infrared (NIR) fluorescence emission with a large Stokes shift, thereby offering remarkable advantages in the design and development of NIR fluorescence probes. This review article primarily focus on small-molecule dicyanoisoporone-based probes from the past two years, elucidating their design strategies, detection performances, and applications. Additionally, we summarize current challenges while predicting future directions to provide valuable references for developing novel and advanced fluorescence probes based on dicyanoisoporone derivatives.

Regioselective C3Alkylation of Indoles for the Synthesis of Bis(indolyl)methanes and 3-Styryl Indoles

Herein, we describe an efficient transition-metal-free regioselective C3alkylation of indoles for the synthesis of bis(indolyl)methanes and 3-styryl indoles. Nitrobenzene is employed as the oxidant to oxidize the alcohols in the presence of a strong base and the reaction avoids the use of transition metals such as Ru and Mn. The protocol provides a favorable route to access biologically active compounds such as arundine, vibrindole A, and turbomycin B.

Bluer Phototruncation: Retro-Diels-Alder of Heptamethine Cyanine to Trimethine Cyanine through an Allene Hydroperoxide Intermediate

The photoconversion of heptamethine to pentamethine cyanines and of pentamethine to trimethine cyanines was recently reported. Here, we report mechanistic studies and initial experimental evidence for a previously unexplored 4-carbon truncation reaction that converts the simplest heptamethine cyanine to the corresponding trimethine cyanine. We propose a DFT-supported model describing a singlet oxygen (1O2)-mediated formation of an allene hydroperoxide intermediate and subsequent 4-carbon loss through a retro-Diels-Alder process. Fluorescence and mass spectrometry measurements provide evidence of this direct conversion process. This 4-carbon truncation reaction adds to a growing body of cyanine reactivity and may provide an optical tool leading to a substantial blue-shift (Δλem) of ∼200 nm.

Activatable probes with potential for intraoperative tumor-specific fluorescence-imaging guided surgery

Owing to societal development and aging population, the impact of cancer on human health and quality of life has increased. Early detection and surgical treatment are the most effective approaches for most cancer patients. As the scope of conventional tumor resection is determined by auxiliary examination and surgeon experience, there is often insufficient recognition of tiny tumors. The ability to detect such tumors can be improved by using fluorescent tumor-specific probes for surgical navigation. This review mainly describes the design principles and mechanisms of activatable probes for the fluorescence imaging of tumors. This type of probe is nonfluorescent in normal tissue but exhibits obvious fluorescence emission upon encountering tumor-specific substrates, such as enzymes or bioactive molecules, or changes in the microenvironment, such as a low pH. In some cases, a single-factor response does not guarantee the effective fluorescence labeling of tumors. Therefore, two-factor-activatable fluorescence imaging probes that react with two specific factors in tumor cells have also been developed. Compared with single biomarker testing, the simultaneous monitoring of multiple biomarkers may provide additional insight into the role of these substances in cancer development and aid in improving the accuracy of early cancer diagnosis. Research and progress in this field can provide new methods for precision medicine and targeted therapy. The development of new approaches for early diagnosis and treatment can effectively improve the prognosis of cancer patients and help enhance their quality of life.

Fluorescence-based absolute quantification of near-infrared probes in tissue extracts for biodistribution analyses

In recent years, significant progress has been made in the development of fluorescent contrast agents for clinical applications. For the development of a fluorescent probe, it is crucial to evaluate its safety profile, including biodistribution. Specific methods need to be developed for the absolute quantification of fluorescent probes in tissue specimens from animals administered with test compounds in the framework of biodistribution/efficacy/toxicity studies. Here, we describe a new method for the absolute quantification of fluorescent probes in tissue specimens from animals administered with compounds that have absorption and emission wavelength in the Near-Infrared region (600-800 nm). The protocol is based on the standard addition approach in order to minimize the interference of the matrix on the analyte signal causing inaccuracy in the absolute determination of the concentration. The measurement of the fluorescence intensity is done via a microplate reader. The method has been fully validated and applied for the quantification of a fluorescence-guided surgery targeted contrast agent in a Good Laboratory Practice (GLP) biodistribution study. Results clearly demonstrate that this procedure is fully applicable in a preclinical setting and that it overcomes common issues associated with fluorescence signal quantification in tissue extracts.

The mechanism of fluorescence quenching of naphthalimide A/C leak detector by copper (II)

BACKGROUND

Fluorescence quenching is an interesting phenomenon with the potential to be applied across various fields. The mechanism is commonly used across analytical applications for monitoring the concentration of trace substances. Naphthalimide and its family of compounds are commonly used as fluorescent detectors. This work investigated an analytical technique through which naphthalimide-based dyes could be quantified. A commercial A/C leak detector was used as the dye and Cu²⁺ ions as the quencher. Experiments were also conducted to investigate the effect of temperature on quenching. To study the mechanism of quenching further, density functional theory (DFT) was used.

RESULTS

The method detection limit obtained in this work is 1.7 × 10^-6 mol/L. The results from the quenching experiments demonstrated a pattern which fit a modified Stern-Volmer (SV) model, with an R² value of 0.9886. From the experiments on the effect of temperature, a dynamic quenching behavior was observed given the emission spectra demonstrated an inverse relationship with temperature.

CONCLUSIONS

The quenching of the commercial A/C dye by Cu²⁺ ions can be used to develop a rapid and sensitive detection method for metal ions such as Cu²⁺, and for future fabrication of chemosensors for Cu²⁺.

Recent progress in the development of fluorescent probes for imaging pathological oxidative stress

Oxidative stress is closely related to the physiopathology of numerous diseases. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) are direct participants and important biomarkers of oxidative stress. A comprehensive understanding of their changes can help us evaluate disease pathogenesis and progression and facilitate early diagnosis and drug development. In recent years, fluorescent probes have been developed for real-time monitoring of ROS, RNS and RSS levels in vitro and in vivo. In this review, conventional design strategies of fluorescent probes for ROS, RNS, and RSS detection are discussed from three aspects: fluorophores, linkers, and recognition groups. We introduce representative fluorescent probes for ROS, RNS, and RSS detection in cells, physiological/pathological processes (e.g., Inflammation, Drug Induced Organ Injury and Ischemia/Reperfusion Injury etc.), and specific diseases (e.g., neurodegenerative diseases, epilepsy, depression, diabetes and cancer, etc.). We then highlight the achievements, current challenges, and prospects for fluorescent probes in the pathophysiology of oxidative stress-related diseases.

Probing tricarbocyanine dyes for targeted delivery of anthracyclines

Along with bright fluorescence in the near-IR range, heptamethine carbocyanine dyes possess affinity to cancer cells. Thus, these dyes could be utilized as fluorescent labels and vectors for drug delivery as covalent conjugates with cytotoxic compounds. To test the properties, structure-activity relationship, and scope of such conjugates, we synthesized drug-dye dyads of tricarbocyanine dyes with anthracycline drug daunorubicin. We used hydrophilic zwitterionic and hydrophobic positively charged benzoindoline-benzothiazole-based heptamethine dyes as terminal alkyne derivatives and N-acylated or oxime-linked daunorubicin as azido-derivatives. These two alkynes and two azides were coupled to each other by Cu-catalyzed Huisgen-Meldal-Sharpless cycloaddition (click reaction) to afford four conjugates. Molecules based on hydrophobic dyes possess submicromolar cytotoxicity to HCT116 cells. Cytotoxicity, cell penetration, intracellular distribution, apoptosis induction and the effect of antioxidants on toxicity were evaluated. The results show that the structure of the cyanine-anthracycline conjugate (hydrophilicity/hydrophobicity, charge, linker, attachment site) is important for its biological activity, thus, expansion of the chemical space of such conjugates could provide new molecular research tools for diagnostics and therapy.

Near-Infrared Probes for Biothiols (Cysteine, Homocysteine, and Glutathione): A Comprehensive Review

Biothiols (cysteine, homocysteine, and glutathione) are an important class of compounds with a free thiol group. These biothiols plays an important role in several metabolic processes in living bodies when present in optimum concentration. Researchers have developed several probes for the detection and quantification of biothiols that can absorb in UV, visible, and near-infrared (NIR) regions of the electromagnetic spectrum. Among them, NIR organic probes have attracted significant attention due to their application in in vivo and in vitro imaging. In this review, we have summarized probes for these biothiols, which could work in the NIR region, and discussed their sensing mechanism and potential applications. Along with focusing on the pros and cons of the reported probes we have classified them according to the fluorophore used and summarized their photophysical and sensing properties (emission, response time, limit of detection).

Effect of Steam Flash-Explosion on Physicochemical Properties and Structure of High-Temperature Denatured Defatted Rice Bran Protein Isolate

The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein.

Structure-Activity Studies of Nitroreductase-Responsive Near-Infrared Heptamethine Cyanine Fluorescent Probes

Two new classes of near-infrared molecular probes were prepared and shown to exhibit "turn on" fluorescence when cleaved by the nitroreductase enzyme, a well-known biomarker of cell hypoxia. The fluorescent probes are heptamethine cyanine dyes with a central 4'-carboxylic ester group on the heptamethine chain that is converted by a self-immolative fragmentation mechanism to a 4'-caboxylate group that greatly enhances the fluorescence brightness. Each compound was prepared by ring opening of a Zincke salt. The chemical structures have either terminal benzoindolinenes or propargyloxy auxochromes, which provide favorable red-shifted absorption/emission wavelengths and a hyperchromic effect that enhances the photon output when excited by 808 nm light. A fluorescent probe with terminal propargyloxy-indolenines exhibited less self-aggregation and was rapidly activated by nitroreductase with large "turn on" fluorescence; thus, it is the preferred choice for translation towards in vivo applications.

A novel heptamethine cyanine photosensitizer for FRET-amplified photodynamic therapy and two-photon imaging in A-549 cells

In this study, a new cyanine-based photosensitizer Cy-N-Rh was developed for photodynamic therapy. Based on fluorescence resonance energy transfer (FRET) mechanism, utilizing the absorption of the donor rhodamine (Rh), the acceptor heptamethine cyanine unit (Cy) was indirectly excited to produce singlet oxygen (¹O₂). The efficiency of energy transfer from the donor Rh to the acceptor Cy was 78.5%. Meanwhile, the singlet oxygen yield of Cy-N-Rh (Φ_Δ = 12.00%) was much higher than that of the acceptor Cy (Φ_Δ = 4.35%) without FRET. Moreover, the dual cation gave Cy-N-Rh with excellent mitochondria-targeting ability with Pearson's correlation coefficients of 0.90 and 0.91, respectively. In the MTT test, Cy-N-Rh had low dark cytotoxicity with cell survival rate above 90% and high photo cytotoxicity with cell survival rate below 40%. The cell apoptosis assay also demonstrated the role of the photosensitizer Cy-N-R visually. More importantly, Cy-N-Rh fulfilled two-photon excitation fluorescence imaging under the 800 nm femtosecond laser. All results indicate that this design strategy provides a new method for the development of higher-level cyanine photosensitizers.

Heptamethine Cyanine–Based Application for Cancer Theranostics

Cancer is the most common life-threatening malignant disease. The future of personalized cancer treatments relies on the development of functional agents that have tumor-targeted anticancer activities and can be detected in tumors through imaging. Cyanines, especially heptamethine cyanine (Cy7), have prospective application because of their excellent tumor-targeting capacity, high quantum yield, low tissue autofluorescence, long absorption wavelength, and low background interference. In this review, the application of Cy7 and its derivatives in tumors is comprehensively explored. Cy7 is enormously acknowledged in the field of non-invasive therapy that can “detect” and “kill” tumor cells via near-infrared fluorescence (NIRF) imaging, photothermal therapy (PTT), and photodynamic therapy (PDT). Furthermore, Cy7 is more available and has excellent properties in cancer theranostics by the presence of multifunctional nanoparticles via fulfilling multimodal imaging and combination therapy simultaneously. This review provides a comprehensive scope of Cy7’s application for cancer NIRF imaging, phototherapy, nanoprobe-based combination therapy in recent years. A deeper understanding of the application of imaging and treatment underlying Cy7 in cancer may provide new strategies for drug development based on cyanine. Thus, the review will lead the way to new types with optical properties and practical transformation to clinical practice.

Perylene-Based Chromophore as a Versatile Dye for Light Amplification

One of the challenges for modern optoelectronics is to find versatile, easily adaptable components for novel laser-based technologies. A very attractive perylene-derivative chromophore in different organic matrices for high-performance light amplification is discussed and outlined. Our approach demonstrates the outstandingly compatible laser dye and a viable strategy to provide an effective optical gain for stimulated emission enhancement. Through structural control, we produce simple optical devices embedded in organic matrices, such as poly(methyl methacrylate), nematic liquid crystalline (NLC) mixture, and a hybrid emulsion system (poly(vinyl alcohol) PVA + NLC mesophase). Importantly, we investigate and compare the spectroscopy of differently constructed organic systems in terms of stimulated-emission thresholds and light amplification process efficiency. Moreover, we report the effects of tunability for LC cells by an applied external electric field stimulus. Future directions of laser systems are outlined with an emphasis on the role of the perylene derivative. The studies meet current challenges in the field of modern organic technologies dedicated to various optoelectronic systems, including touch screens, displays, and Li-Fi networks.

Near-infrared emissive polymer-coated IR-820 nanoparticles assisted photothermal therapy for cervical cancer cells

Photothermal therapy (PTT) has attracted wide attention due to its noninvasiveness and its thermal ablation ability. As photothermal agents are crucial factor in PTT, those with the characteristics of biocompatibility, non-toxicity and high photothermal stability have attracted great interest. In this work, new indocyanine green (IR-820) was utilized as a photothermal agent and near-infrared (NIR) fluorescence imaging nanoprobe. To improve the biocompatibility, poly(styrene-co-maleic anhydride) (PSMA) was utilized to encapsulate the IR-820 molecules to form novel IR-820@PSMA nanoparticles (NPs). Then, the optical and thermal properties of IR-820@PSMA NPs were studied in detail. The IR-820@PSMA NPs showed excellent photothermal stability and biocompatibility. The cellular uptaking ability of the IR-820@PSMA NPs was further confirmed in HeLa cells by the NIR fluorescent confocal microscopic imaging technique. The IR-820@PSMA NPs assisted PTT of living HeLa cells was conducted under 793 nm laser excitation, and a high PTT efficiency of 73.3% was obtained.

Design, synthesis and application of near-infrared fluorescence probe IR-780-Crizotinib in detection of ALK positive tumors

At present, the early diagnosis and treatment of NSCLC has become an international research hotspot. However, how to realize the organic combination of highly sensitive and high-resolution tumor imaging diagnosis and effective treatment, and to provide effective information for the diagnosis and treatment of cancer is still a major problem in the integration of cancer diagnosis and treatment. In this study, based on the Crizotinib has a good targeted inhibitory effect on ALK positive tumor cells, the near-infrared targeted fluorescent dye IR-780 was covalently bound with the drug molecule Crizotinib, thus the near-infrared fluorescent probe IR-780-Crizotinib targeting ALK positive tumor cells was synthesized. The probe structure is confirmed by NMR and MS. The optical properties of the fluorescent probe and the imaging process in ALK positive tumor-bearing mice were analyzed using ultraviolet spectrophotometer, near-infrared fluorescence spectrometer, and near-infrared fluorescence imaging system. The results show that the probe had better photoactivity. In vivo imaging shows that the probe maintained the biological activity of Crizotinib, effectively targeting the tumor site involved with clear imaging, and ultimately excreted from the body. It was confirmed that the probe could be used for the tracking, positioning and targeted therapy of nude mice with ALK positive tumors in vivo, thus exploring a new approach for the clinical application of near-infrared fluorescent probe to detect ALK positive tumors in the future.

Borisov S. Carbazole- and Fluorene-Fused Aza-BODIPYs: NIR Fluorophores with High Brightness and Photostability

Three new aza-BODIPY dyes incorporating fused fluorene or carbazole moieties have been prepared. The dyes show significant enhancement of photophysical properties compared to the parent 1,3,5,7-tetraphenyl aza-BODIPY (TPAB): a bathochromic shift of the absorption maximum (up to 2700 cm-1 ) and emission maximum (up to 2270 cm-1 ); an almost threefold increase in molar absorption coefficients (to ca. 230 000 M-1  cm-1 ) and a significant increase in the fluorescence quantum yield to 49-66 %. Owing to the combination of these properties, the new aza-BODIPY dyes belong to the brightest NIR dyes reported. The dyes also show excellent photostability. Due to their outstanding properties, the new dyes represent a promising platform for further exploration in biomedical research. A pH indicator containing only one fused carbazole unit was also prepared and shows absorption and emission spectra that are bathochromically shifted by about 110 and 100 nm, respectively, compared to the indicator dye based on the TPAB chromophore.

Intracellular pH - Advantages and pitfalls of surface-enhanced Raman scattering and fluorescence microscopy - A review

The value of pH in various parts of protoplasm can affect nearly all aspects of cell functions. Therefore, the determination of intracellular acid-base features is required in many areas of biological and biochemical studies. Because of a significant scientific importance of in vivo intracellular pH measurements, various groups carried out such experiments. In this review article we describe intracellular pH measurements using two the most sensitive optical spectroscopies: surface-enhanced Raman scattering (SERS) and fluorescence. It is reasonable to present these two techniques in one review article because the experimental approach in Raman and fluorescence experiments is relatively similar. The basic theoretical background explaining the mechanism of operation of fluorescence and SERS sensors are discussed and the motivations to carry out intracellular pH measurements are briefly described. Future perspectives in this field are also discussed.

Explorations into the Effect of meso-Substituents in Tricarbocyanine Dyes: A Path to Diverse Biomolecular Probes and Materials

Polymethine cyanine dyes have been widely recognized as promising chemical tools for a range of life science and biomedical applications, such as fluorescent staining of DNA and proteins in gel electrophoresis, fluorescence guided surgery, or as ratiometric probes for probing biochemical pathways. The photophysical properties of such dyes can be tuned through the synthetic modification of the conjugated backbone, for example, by altering aromatic cores or by varying the length of the conjugated polymethine chain. Alternative routes to shaping the absorption, emission, and photostability of dyes of this family are centered around the chemical modifications on the polymethine chain. This Minireview aims to discuss strategies for the introduction of substituents in the meso-position, their effect on the photophysical properties of these dyes and some structure-activity correlations which could help overcome common limitations in the state of the art in the synthesis.

Emergent Biosensing Technologies Based on Fluorescence Spectroscopy and Surface Plasmon Resonance

The purpose of this work is to provide an exhaustive overview of the emerging biosensor technologies for the detection of analytes of interest for food, environment, security, and health. Over the years, biosensors have acquired increasing importance in a wide range of applications due to synergistic studies of various scientific disciplines, determining their great commercial potential and revealing how nanotechnology and biotechnology can be strictly connected. In the present scenario, biosensors have increased their detection limit and sensitivity unthinkable until a few years ago. The most widely used biosensors are optical-based devices such as surface plasmon resonance (SPR)-based biosensors and fluorescence-based biosensors. Here, we will review them by highlighting how the progress in their design and development could impact our daily life.

Cancer and pH Dynamics: Transcriptional Regulation, Proteostasis, and the Need for New Molecular Tools

An emerging hallmark of cancer cells is dysregulated pH dynamics. Recent work has suggested that dysregulated intracellular pH (pHi) dynamics enable diverse cancer cellular behaviors at the population level, including cell proliferation, cell migration and metastasis, evasion of apoptosis, and metabolic adaptation. However, the molecular mechanisms driving pH-dependent cancer-associated cell behaviors are largely unknown. In this review article, we explore recent literature suggesting pHi dynamics may play a causative role in regulating or reinforcing tumorigenic transcriptional and proteostatic changes at the molecular level, and discuss outcomes on tumorigenesis and tumor heterogeneity. Most of the data we discuss are population-level analyses; lack of single-cell data is driven by a lack of tools to experimentally change pHi with spatiotemporal control. Data is also sparse on how pHi dynamics play out in complex in vivo microenvironments. To address this need, at the end of this review, we cover recent advances for live-cell pHi measurement at single-cell resolution. We also discuss the essential role for tool development in revealing mechanisms by which pHi dynamics drive tumor initiation, progression, and metastasis.

A Facile and Reproducible Synthesis of Near-Infrared Fluorescent Conjugates with Small Targeting Molecules for Microbial Infection Imaging

Optical imaging of microbial infections, based on the detection of targeted fluorescent probes, offers high sensitivity and resolution with a relatively simple and portable setup. As the absorbance of near-infrared (NIR) light by human tissues is minimal, using respective tracers, such as IRdye800CW, enables imaging deeper target sites in the body. Herein, we present a general strategy for the conjugation of IRdye800CW and IRdye700DX to small molecules (vancomycin and amphotericin B) to provide conjugates targeted toward bacterial and fungal infections for optical imaging and photodynamic therapy. In particular, we present how the use of coupling agents (such as HBTU or HATU) leads to high yields (over 50%) in the reactions of amines and IRDye-NHS esters and how precipitation can be used as a convenient purification strategy to remove excess of the targeting molecule after the reaction. The high selectivity of the synthesized model compound Vanco-800CW has been proven in vitro, and the development of analogous agents opens up new possibilities for diagnostic and theranostic purposes. In times of increasing microbial resistance, this research gives us access to a platform of new fluorescent tracers for the imaging of infections, enabling early diagnosis and respective treatment.

High-Yielding Water-Soluble Asymmetric Cyanine Dyes for Labeling Applications

A simple and efficient microwave-assisted synthesis of asymmetric pentamethine cyanine dyes with various functional groups was developed, which allows high-yielding results. The synthesized dyes are modifiable and suitable for single-molecule imaging in biological and medical sciences by application of click chemistry or classic esterification and amidation.

New directions of activity-based sensing for in vivo NIR imaging

In vivo imaging is a powerful approach to study biological processes. Beyond cellular methods, in vivo studies allow for biological stimuli (small molecules or proteins) to be studied in their native environment. This has the potential to aid in the discovery of new biology and guide the development of diagnostics and therapies for diseases. To ensure selectivity and an observable readout, the probe development field is shifting towards activity-based sensing (ABS) approaches and near-infrared (NIR) imaging modalities. This perspective will highlight recent in vivo ABS applications that utilize NIR imaging platforms.