Small Organic Dyes Research Articles

Bridge-induced taming of the visible electronic circular dichroism signatures of helicoBODIPYs

Helically-flexible bis(BODIPY)s based on chiral ethane-1,2-diamine or −1,2-diol bridges (named helicoBODIPYs) are an interesting family of accessible and tunable small multichromophoric organic dyes enabling visible electronic circular dichroism (ECD) and, even visible circularly polarized luminescence (CPL). However, their CPL brightness (BCPL) is still limited (up to ca. 10 M−1cm−1), due to low fluorescence efficiency owing to a non-optimal participation of intramolecular charge transfer (CT) emission. Herein, we analyze in depth the origin and factors controlling this CT, demonstrating the key participation of a BODIPY-to-BODIPY symmetry-breaking induced CT (SBCT), beyond the expected CT within each single BODIPY chromophore due to their push-pull character. It is also demonstrated that increasing the overcrowding at the flexible helicoBODIPY ethane bridges leads to BODIPY-BODIPY faced dispositions, promoting the SBCT and enabling the detection of both CT absorption and CT emission bands under specific conditions. Interestingly, this SBCT enhances the visible ECD (absolute gabs values), supporting the key role of the involved forbidden CT transitions in the chiroptical activity of these dyes, as well as the possibility of modulating their valuable visible chiroptical signatures (e.g., visible CPL brightness) by easily playing with steric factors at the dye bridge.

Visualizing Amyloid Assembly at the Nanoscale: Insights from Super‐Resolution Imaging

AbstractIn the rapidly evolving landscape of molecular imaging, super‐resolution techniques emerge as indispensable tools, revolutionizing our capacity to decipher the intricacies of protein aggregation, and paving the way for molecular‐level understanding of the progression of neurodegenerative disorders. In this review article we provide an overview of the diverse super‐resolution imaging techniques applied to study amyloids at high resolution. We outline the strengths and limitations of each technique, offering insights into their applicability to different amyloid systems. We next delve into the diverse strategies employed for labeling amyloids in conjunction with super‐resolution imaging. From small organic dyes to fluorescent proteins and advanced chemical probes, the discussion encompasses the strengths and considerations associated with each labeling method. The comparative analysis not only evaluates the impact of labeling on resolution and specificity but also highlights emerging trends and future directions in the field.

Exploring g-C3N4 as a green additive for biodegradable poly(butylene adipate-co-terephthalate) film with enhanced UV shielding and mechanical properties.

Typical small organic dyes exhibit excellent UV absorption capabilities and are commonly used as additives to shield plastic films from photoaging. However, their tendency to decompose easily and migrate rapidly within a polymer matrix limits their service life. Herein we prepared g-C3N4 nanosheets and fabricated g-C3N4/PBAT films to investigate the effects of g-C3N4 on UV shielding and plasticizing of a biodegradable PBAT film. Photophysical characterizations revealed that an improved UV light barrier performance was achieved on g-C3N4/PBAT films compared to pure PBAT. Furthermore, the photoaging results show that g-C3N4 can stably exist in the PBAT matrix, enabling the aged g-C3N4/PBAT films to maintain their effective UV shielding ability, whereas the aged benzophenone (UV-0)/PBAT film shows a substantial decrease in UV light absorption due to the photodecomposition of UV-0. Additionally, g-C3N4 acted as a reinforcing material for PBAT, as evidenced by the approximately 1.5-fold increase in longitudinal tear strength and 1.6-fold increase in tensile strength of g-C3N4/PBAT films compared to pure PBAT. Remarkably, even after 100 hours of photoaging, the aged g-C3N4/PBAT films retained their favorable mechanical properties. This study highlights the potential of g-C3N4 as a new type of UV shield additive for future practical applications in protecting biodegradable plastic from photoaging.

Robust reduced graphene oxide-PDA/ZIF-8 aerogel composite for cyclic, high-capacity dye adsorption

The contamination of nanosized organic dyes in the water bodies is of great concern as it adversely affects the marine ecosystem and biodiversity, leading to water-borne ailments. In recent years, designing sustainable, high-performance, and cost-effective composite adsorbents embedded with functional adsorbents for wastewater treatment has attracted immense attention. In this work, a new composite aerogel (rGO-PDA/ZIF-8) was prepared via self-assembling graphene oxide (GO) flakes to form a three-dimensional (3D) structure with functional polydopamine (PDA). Then, ZIF-8 crystals were decorated on the porous aerogel structure via the in-situ crystallization method. PDA-modified rGO aerogel provided abundant useful functional groups, such as –OH, –COOH, and –NH–, on the surface, while the incorporation of ZIF-8 nanocrystals further endowed composite aerogels with higher surface area and extra functional groups for enhanced organic dye adsorption. Our results revealed that the composite aerogel exhibited not only ultrahigh adsorption towards methylene blue (MB) with a maximum adsorption capacity of 1045 ± 2.9 mg g−1 (with a maximum rejection rate of > 99 %) but also excellent recyclability with a slightly decreased adsorption capacity of 897 ± 26.9 mg g−1 and a stable removal efficiency of > 92 % even after 10 cycles of adsorption. To the best of our knowledge, the obtained adsorption capacity almost doubled the best-reported values at similar conditions in the literature. The excellent adsorption performance is owing to strong π–π and electrostatic attractions between the dye molecules and the hierarchical porous composite structures with functional PDA coating and ZIF-8 nano-adsorbents. Therefore, the new composite rGO-PDA/ZIF-8 aerogel composite has great potential in high-performance, cyclic small organic dye separation.

Vibrationally Resolved Absorption, Fluorescence, and Preresonance Raman Spectroscopy of Isolated Pyronin Y Cation at 5 K.

Exploring how charge-changing affects the photoluminescence of small organic dyes presents challenges. Here, helium tagging photodissociation (PD) action spectroscopy in the gas phase and dispersed laser-induced fluorescence (DF) spectroscopy in the solid Ne matrix are used to compare the intrinsic photophysical properties of pyronin Y cation [PY]+ and its one electron-reduced neutral radical [PY]• at 5 K. Whereas the cation shows efficient visible photoluminescence, no emission from the neutral, in line with theoretical predictions, was detected. B3LYP/aug-cc-pVDZ calculations based on the TD-DFT/FCHT method allow for unambiguous assignment of recorded vibrationally resolved absorption and emission spectra. Surprisingly, our experimental sensitivity was high enough to also observe electronic preresonance Raman (ePR-Raman) spectra of [PY]+, with a significant efficiency factor (EF). These characteristics of the [PY]•/[PY]+ pair suggest that appropriately functionalized derivatives may open new perspectives in the area of in vivo bioimagining microscopy and find applications in various sophisticated stimulated-Raman spectroscopies.

Organic Dye Molecule Intercalated Vanadium Oxygen Hydrate Enables High-Performance Aqueous Zinc-Ion Storage.

Although the layered vanadium oxide-based materials have been considered to be one of the candidates for aqueous Zn-ion batteries (AZIBs), it still faces inevitable challenges of unsatisfactory capacities and sluggish kinetics because of strong electrostatic interactions between Zn-ions and structure lattice. This work addresses the strategy of pre-inserting guest materials to vanadium oxide cathode using different intercalants. To achieve this goal, the small organic dye molecules, methyl orange (MO), and methylene blue (MB) are proposed as the intercalants for vanadium oxygen hydrate (VOH). It has been demonstrated that use of these intercalants can facilitate reaction kinetics between Zn2+ and VOH, leading to an improvement of specific capacity (293mAhg-1 at 0.3Ag-1 for MO-VOH and 311mAhg-1 for MB-VOH) compared to VOH, a large enhancement of excellent energy density (237.1Whkg-1 for MO-VOH, 232.3Whkg-1 for MB-VOH), and a prolong lifespan operation at 3Ag-1 . The mechanism studies suggest that the weakened electrostatic interactions between the Zn-ions and V-O lattice after intercalating organic molecules contribute to boosting the electrochemical performance of AZIBs unveiled by charge density difference and binding energy.

Hybrid ceramic nanofiltration membranes prepared by impregnation and solid-state grafting of organo-phosphonic acids

Grafting of oligomers into the mesopores of ceramic membranes (e.g. γ-alumina) represents an attractive strategy for deploying durable, resistant, and efficient hybrid membranes for the industrial treatment of wastewater containing organic solvents and divers solutes. In general, to control the membrane/solute/solvent interactions, homogeneous surface modification and high grafting yields are required. However, reaching this goal is rather challenging with the current grafting approaches where the active diffusion of the oligomers to the membrane pore surface may be hampered. To mitigate such diffusion limitation, we present here a novel synthesis method consisting of an infiltration of concentrated PEG organophosphonic acid oligomer solution in ceramic ultrafiltration membranes before initiating the solid-state grafting reaction to form a PEG-brush-grafted nanofiltration ceramic membrane. The infiltration step was found to be decisive for the formation of weak bonds between the oligomer linking functions and the ceramic membrane ensuring the final synthesis of robust PEG-based membranes by a grafting reaction. The influence of the solvent polarity (water vs. cyclohexane) on the conformation of the grafted PEG brush inside the γ-alumina mesopores was observed as a key parameter in the analysis of the pore size and permeability results. In addition to this, it was studied here for the first time by molecular dynamic simulations. The as-prepared PEG-brush/ceramic membranes were found very efficient in the separation of small organic dyes such as Rhodamine B (479 g mol−1) up to 85%. As a result, the present synthesis method represents a sustainable and simple alternative way for the preparation of hybrid nanofiltration membranes with controlled surface properties and attractive separation performance. Moreover, the vacuum impregnation and solid-state grafting approach requires a minimal amount of functional oligomers and solvent (0.5 mmol for 2–3 mL of solvent) and can be applied to other porous materials used in separation technologies.

Click chemistry, FRET-FCS, and expansion microscopy reveal that Na, K-ATPase forms complexes in the plasma membrane

In order to study the spatial distribution of Na, K-ATPase alpha and beta subunits in the plasma membrane of epithelial cells we have developed sample preparation protocols based on genetic code expansion, click chemistry and expansion microscopy. HEK 293T cells were transiently transfected with constructs containing the coding sequence for Na, K-ATPase subunits (alpha1 and beta1) carrying a premature amber or ochre stop codon. Two bioorthogonal tRNA and tRNA synthetase pairs were also transfected for stop codon suppression and site-specific insertion of two unnatural amino acids. The unnatural amino acids were then labelled with small organic dyes using CuAAC and SPIEDAC click reactions. Care was taken to keep the transfection and expression levels low.In living cells, we used Fluorescence Correlation Spectroscopy (FCS) and FRET to assess the density of click-labeled and endogenous [SE1] Na, K-ATPase in the plasma membrane. The dyes Alexa488 and Alexa647 were used as a FRET sensor for homo- and heterodimer analysis and, using FRET-FCS, we could detect the oligomerization of alpha and beta in a complex containing two alpha and two beta subunits in a heterodimer.FCS measurements in cells where both the alpha and beta subunits were labeled was used to calculate the absolute density of endogenous and exogenous Na, K-ATPase in the plasma membrane. To detect oligomerization, we used cells where the beta subunit was labeled with a 50/50 mix of Alexa488 and Alexa647. We successfully detected FRET signals and an analysis of the FRET-FCS data revealed a high density of oligomers. FRET-FCS is, compared to conventional cross-correlation FCCS, one to two orders of magnitude more sensitive for the detection of oligomers. FRET-FCS is also inherently insensitive to heterogenous labeling efficiencies, which is a great advantage during live cell measurementsExpansion microscopy was performed using a modified MAP protocol, reaching an isotropic expansion of approximately 4.5-fold. Confocal airyscan microscopy of the expanded cells with <50nm resolution revealed local variations in Na, K-ATPase density and enabled detailed cluster analysis.In conclusion we demonstrate that the density of Na, K-ATPase has large local variations and that the Na, K-ATPase oligomerizes in the plasma membrane. We propose that this oligomerization can have a regulatory function for the net efficiency of Na, K-ATPase in the cell. VR 2020-05347, VR 2019-00217 (Swedish Research Council) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Photoacoustic Imaging Probes for Theranostic Applications.

Photoacoustic imaging (PAI), an emerging biomedical imaging technology, capitalizes on a wide range of endogenous chromophores and exogenous contrast agents to offer detailed information related to the functional and molecular content of diseased biological tissues. Compared with traditional imaging technologies, PAI offers outstanding advantages, such as a higher spatial resolution, deeper penetrability in biological tissues, and improved imaging contrast. Based on nanomaterials and small molecular organic dyes, a huge number of contrast agents have recently been developed as PAI probes for disease diagnosis and treatment. Herein, we report the recent advances in the development of nanomaterials and organic dye-based PAI probes. The current challenges in the field and future research directions for the designing and fabrication of PAI probes are proposed.

Multifunctional Gold Nanoclusters for Effective Targeting, Near-Infrared Fluorescence Imaging, Diagnosis, and Treatment of Cancer Lymphatic Metastasis.

Developing effective lymph-node (LN) targeting and imaging probes is crucial for the early detection and diagnosis of tumor metastasis to improve patient survival. Most current clinical LN imaging probes are based on small organic dyes (e.g., indocyanine green) or radioactive 99mTc-complexes, which often suffer from limitations, such as rapid photobleaching, poor signal contrast, and potential biosafety issues. Moreover, these probes cannot easily incorporate therapeutic functions to realize beneficial theranostics without affecting their LN-targeting ability. Herein, we have developed dual-ligand-/multiligand-capped gold nanoclusters (GNCs) for specific targeting, near-infrared (NIR) fluorescence imaging, diagnosis, and treatment of LN cancer metastasis in in vivo mouse models. By optimizing the surface ligand coating, we have prepared Au25(SR1)n(SR2)18-n (where SR1 and SR2 are different functional thiol ligands)-type GNCs, which display highly effective LN targeting, excellent stability and biocompatibility, and optimal body-retention time. Moreover, they can provide continuous NIR fluorescence imaging of LNs for >3 h from a single dose, making them well-suited for fluorescence-guided surgery. Importantly, we have further incorporated methotrexate, a chemotherapeutic drug, into the GNCs without affecting their LN-targeting ability. Consequently, they can significantly improve the efficiency of methotrexate delivery to target LNs, achieving excellent therapeutic efficacy with up to 4-fold lower hepatotoxicity. Thus, the GNCs are highly effective and safe theranostic nanomedicines against cancer lymphatic metastasis.

A quinoline-based indicator for NAD(P)H multimodal detection in vitro and in vivo: Spectrophotometry and visible near-infrared dual-channel lighting-up fluorescence imaging

Nicotinamide adenine dinucleotide (phosphate) (NAD(P)H/NAD(P)+) is crucial for oxidation-reduction equilibrium in all living cells, and disturbance of NAD(P)H/NAD(P)+ indicates many diseases. To accurately detect and track NAD(P)H in vitro and in vivo, we have developed a small organic dye (Rh-QL) based on intramolecular charge transfer (ICT) mechanism for multimodally detecting NAD(P)H by visible and near-infrared (Vis-NIR) dual-channel lighting-up fluorescence and by near-infrared spectrophotometry. This quinoline-based Indicator showed high selectivity and sensitivity toward NAD(P)H with a large redshift of absorption and dual-channel emissions at 580 nm and 750 nm, spatiotemporally and synchronously. For liquid samples, Rh-QL succeeded to screen NAD(P)H-related G6PD enzymatic activity by responsive absorption at 710 nm. In living cells, Rh-QL exhibited a good bio-compatibility and remarkable mitochondrial-targeted capacity to visualize intracellular endogenous and exogenous NAD(P)H variation utilizing Vis-NIR dual-channel fluorescence. In vivo, the near-infrared fluorescence was applied to differentiate tumor-bearing mice by NAD(P)H imaging. Moreover, “glycolysis” in both cancer cells and tumors of mice were traced to produce extra NAD(P)H using Rh-QL. As the first Vis-NIR dual-channel lighting-up probe to multimodally detect and track NAD(P)H in vitro and in vivo, it is appealing for high efficiency in understanding NAD(P)H-related physiological and pathological processes of disease diagnosis and therapy.

Surface Plasmon Enhanced Upconversion Fluorescence in Short-Wave Infrared for In Vivo Imaging of Ovarian Cancer.

Short-wave infrared (SWIR; 850-1700 nm) upconversion fluorescence enables "autofluorescence-free" imaging with minimal tissue scattering, yet it is rarely explored due to the lack of strongly emissive SWIR upconversion fluorophores. In this work, we apply SWIR upconversion fluorescence for in vivo imaging with exceptional image contrast. Gold nanorods (AuNRs) are used to enhance the SWIR upconversion emission of small organic dyes, forming a AuNR-dye nanocomposite (NC). A maximal enhancement factor of ∼1320, contributed by both excitation and radiative decay rate enhancement, is achieved by varying the dye-to-AuNR ratio. In addition, the upconversion emission intensity of both free dyes and AuNR-dye NCs depends linearly on the excitation power, indicating that the upconversion emission mechanism remains unchanged upon enhancement, and it involves one-photon absorption. Moreover, the SWIR upconversion emission shows a significantly higher signal contrast than downconversion emission in the same emission window in a nonscattering medium. Finally, we apply the surface plasmon enhanced SWIR upconversion fluorescence for in vivo imaging of ovarian cancer, demonstrating high image contrast and low required dosage due to the suppressed autofluorescence.

(Invited) Kinetics and Thermodynamics of Swcnts and Bnnts Encapsulation with α-Sexithiophene in Liquid Phase

Single-Walled Carbon Nanotubes (SWNTs) and Boron Nitride Nanotubes (BNNTs) come with hollow 1D centers, which can serve to define narrow spaces for encapsulating small organic dyes. The encapsulation process is of scientific interest because it can be used to tailor the optical properties of the resulting dyes@NTs nanohybrids. Past works have shown that the dyes@SWCNT exhibits a strongly enhanced Raman scattering cross section, while the dyes@BNNTs do emit robust, generally red-shifted, luminescence at wavelengths down to the near-IR. In both cases, the nanotube protects the encapsulated dyes from photobleaching, provides high confinement, and reinforces intermolecular interactions between dyes into specific aggregation states.Here, we compare the liquid phase encapsulation process of α-sexithiophene (6T), which is a conjugated rod-like dye, inside SWCNTs and BNNTs. Raman and luminescence imaging experiments are used to monitor the 6T encapsulation process of a large ensemble of individual nanotubes in liquid-phase. This method probes statistically the encapsulation kinetics using hundreds of individual nanotubes according to various parameters (dye concentration and temperature). The results highlight a kinetic model in which single and double aggregates is formed sequentially. This kinetics and the associated thermodynamic parameters for the 6T encapsulation will be presented and discussed so as to gain a better control over the emission properties of the nanohybrids.

Progress in the past five years of small organic molecule dyes for tumor microenvironment imaging.

The tumor microenvironment (TME) is the survival environment for tumor cell proliferation and metastasis in deep tissues. Prognostic factors, such as growth, invasion and metastasis of malignant tumors, are closely related to changes in physiological parameters, including hypoxia, enzymes, low extracellular pH, and reduction conditions. Therefore, it is of great clinical significance to study tumor microenvironment markers to evaluate tumor progression and predict therapeutic effects. Organic fluorescent dyes are popular because of their small size, easy modification, adjustable luminescence and simple elucidation of their mechanism, and are widely used in tumor diagnosis and treatment. This paper reviews recent progress in fluorescent probes based on small organic molecules for imaging TME markers. Firstly, the design mechanism of a fluorescent probe is discussed, and then the application of pH, hypoxia, and reactive oxygen species, and a reduction-condition-responsive fluorescent probe in tumor imaging is discussed in detail. Finally, the prospects for the application of small-molecule fluorescent probes for imaging a tumor microenvironment in vivo are explored, but the potential application of small-molecule fluorescent probes in the early diagnosis of cancer as well as in the clinical laboratory for differentiating cancers, and further use in image-guided tumor surgery still face great challenges.

Controlled Nanoconfinement of Polyimide Networks in Mesoporous γ-Alumina Membranes for the Molecular Separation of Organic Dyes

Polyimide networks are key in the development of stable, resilient, and efficient membranes for separation applications under demanding conditions. To this aim, the controlled design of the network’s nanostructure and its properties are needed. However, such control remains a challenge with currently available synthesis methods. Here, we present a simple nanofabrication approach that allows the controlled nanoconfinement, growth, and covalent attachment of polyimide (PI) networks inside the mesopores of γ-alumina layers. The attachment of the PI network on the γ-alumina layer was initiated via different prefunctionalization steps that play a pivotal role in inducing the in situ polymerization reaction at the pore entrance and/or at the inner pore surface. The nanoconfinement was found to be limited to the 1.5 μm-thick γ-alumina supporting layer at maximum, and the resulting hybrid PI/ceramic membranes showed stable performance in a variety of solvents. These PI/ceramic membranes were found to be very efficient in the challenging separation of small organic dye molecules such as Rhodamine B (479 g mol–1) from toxic solvents such as dimethylformamide or dioxane. Therefore, this technique opens up possibilities for a multitude of separations. Moreover, the PI synthesis approach can be applied to other applications that also rely on porosity and stability control, such as for advanced insulation and anticorrosion.

Diketopyrrolopyrrole‐derived organic small molecular dyes for tumor phototheranostics

Cancer is one of the leading causes of human death around the world. Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is an emerging light-triggered cancer treatment and shows the advantages of non-invasiveness and low side effects. The design and preparation of efficient phototherapeutic agents are of great significance for phototherapy. Diketopyrrolopyrrole (DPP) is a small molecular organic dye featuring outstanding photophysical properties, facile tuning of structures and properties, and excellent photostability; thus, phototherapeutic agents based on organic small molecular DPP derivatives have attracted significant research attention for not only phototherapy but also photodiagnosis of fluorescence imaging (FLI) and photoacoustic imaging (PAI). This review summarizes the recent progress of various DPP-based organic small molecules on phototheranostics during the last five years. The molecular structure design and their phototheranostics performances are discussed in detail, as will be of great help for further creation of DPP-based phototheranostics.

Multi-layered Barium and Strontium Carbonate Structures Induced by the Small Organic Dye Acid Orange 7.

The crystal growth behavior induced by small molecular additives is commonly assumed to be far less complex and rich in comparison to that obtained when using macromolecules. Herein, we demonstrate that the small organic molecule Acid Orange 7 can induce a large diversity of multi-layered barium carbonate structures. These multi-layered structures stem from the small molecule imperfectly blocking the fastest growing crystal face. By tuning the balance of growth and inhibition, we control the layer shape and thickness of the structures. Extending these strategies to strontium carbonate enables the precipitation of large quasi two-dimensional multi-layer sheets. Collectively, these findings highlight the unforeseen potential for using small organic molecules to induce the formation of complex inorganic structures.

Characterization of Novel Fluorescent Bile Salt Derivatives for Studying Human Bile Salt and Organic Anion Transporters.

Bile salts, such as cholate, glycocholate, taurocholate, and glycochenodeoxycholate, are taken up from the portal blood into hepatocytes via transporters, such as the Na+-taurocholate-cotransporting polypeptide (NTCP) and organic anion-transporting polypeptides (OATPs). These bile salts are later secreted into bile across the canalicular membrane, which is facilitated by the bile salt export pump (BSEP). Apart from bile salt transport, some of these proteins (e.g., OATPs) are also key transporters for drug uptake into hepatocytes. In vivo studies of transporter function in patients by using tracer compounds have emerged as an important diagnostic tool to complement classic liver parameter measurements by determining dynamic liver function both for diagnosis and monitoring progression or improvement of liver diseases. Such approaches include use of radioactively labeled bile salts (e.g., for positron emission tomography) and fluorescent bile salt derivatives or dyes (e.g., indocyanine green). To expand the list of liver function markers, we synthesized fluorescent derivatives of cholic and chenodeoxycholic acid by conjugating small organic dyes to the bile acid side chain. These novel fluorescent probes were able to block substrate transport in a concentration-dependent manner of NTCP, OATP1B1, OATP1B3, OATP2B1, BSEP, and intestinal apical sodium-dependent bile salt transporter (ASBT). Whereas the fluorescent bile acid derivatives themselves were transported across the membrane by OATP1B1, OATP1B3, and OATP2B1, they were not transport substrates for NTCP, ASBT, BSEP, and multidrug resistance-related protein 2. Accordingly, these novel fluorescent bile acid probes can potentially be used as imaging agents to monitor the function of OATPs. SIGNIFICANCE STATEMENT: Synthetic modification of common bile acids by attachment of small organic fluorescent dyes to the bile acid side chain resulted in bright, fluorescent probes that interact with hepatic and intestinal organic anion [organic anion-transporting polypeptide (OATP) 1B1, OATP1B3, OATP2B1], bile salt uptake (Na+-taurocholate-cotransporting polypeptide, apical sodium-dependent bile salt transporter), and bile salt efflux (bile salt export pump, multidrug resistance-related protein 2) transporters. Although the fluorescent bile salt derivatives are taken up into cells via the OATPs, the efflux transporters do not transport any of them but one.

Noninvasive In Vivo Imaging and Monitoring of 3D-Printed Polycaprolactone Scaffolds Labeled with an NIR Region II Fluorescent Dye.

Significant progress has been made in fabricating porous scaffolds with ultrafine fibers for tissue regeneration. However, the lack of noninvasive tracking methods in vivo makes it impossible to track the fate of such scaffolds in situ. The development of near-infrared region II (NIR-II, 1000-1700 nm) dyes provides the possibility of performing noninvasive visualization with deep-tissue penetration and high spatial resolution in vivo. Herein, we developed a polycaprolactone (PCL) ink containing the small organic NIR-II dye SY-1030 and the fluorescently labeled macromolecular dye SY-COO-PCL and fabricated high-resolution NIR-II active scaffolds via electrohydrodynamic jet (EHDJ) printing. All printed scaffolds subcutaneously implanted in mice were clearly imaged one week after the operation. Compared with scaffolds containing SY-1030, the fluorescence intensity emitted from scaffolds containing SY-COO-PCL can be tracked for up to three weeks. Moreover, the image quality can be optimized by adjusting the dye concentration, laser power, and exposure time. The advantage of such NIR-II active scaffolds is evidenced by the lower dye concentration, longer tracking period, and better in vivo stability. We also demonstrated the biocompatibility and biodegradability of the scaffolds containing SY-COO-PCL over a 3-month period. The developed NIR-II active scaffolds have potential applications in biopolymer implant tracking, tissue reconstruction monitoring, and target-position-based drug delivery.

D-A-D structured selenadiazolesbenzothiadiazole-based near-infrared dye for enhanced photoacoustic imaging and photothermal cancer therapy

Near-infrared (NIR) small molecular organic dyes as photothermal agents for cancer photothermal therapy (PTT) have attracted considerable research attention. Herein, two donor-acceptor-donor (D-A-D) structured NIR dyes, BBTT and SeBTT, are rationally designed, where the only difference is one heteroatom within the acceptor unit varying from sulfur to selenium (Se). More importantly, SeBTT NPs exhibit stronger NIR absorbance and higher photothermal conversion efficiency (PTCE ≈ 65.3%). In vivo experiments illustrate that SeBTT NPs can be utilized as a high contrast photoacoustic imaging (PAI) agent, and succeed in tumor suppression without noticeable damage to main organs under NIR photoirradiation. This study presents an effective molecular heteroatom surgery strategy to regulate the photothermal properties of NIR small molecules for enhanced PAI and PTT.