Photodynamic Therapy with Targeted Release of Boron-Dipyrromethene Dye from Cobalt(III) Prodrugs in Red Light.

Boron-dipyrromethene (BODIPY) dyes are promising photosensitizers for cellular imaging and photodynamic therapy (PDT) owing to their excellent photophysical properties and the synthetically tunable core. Metalation provides a convenient way to overcome the drawbacks arising from their low aqueous solubility. New photo-/redox-responsive Co(III) prodrug chaperones are developed as anticancer PDT agents for efficient cellular delivery of red-light-active BODIPY dyes. The photobiological activity of heteroleptic Co(III) complexes derived from tris(2-pyridylmethyl)amine (TPA) and acetylacetone-conjugated PEGylated distyryl BODIPY (HL1) or its dibromo analogue (HL2), [CoIII(TPA)(L1/L2)](ClO4)2 (1 and 2), are investigated. The Co(III)/Co(II) redox potential is tuned using the Co(III)-TPA scaffold. Complex 1 displays the in vitro release of BODIPY on red light irradiation. Complex 2, having good singlet oxygen quantum yield (ΦΔ âˆ¼ 0.28 in DMSO), demonstrates submicromolar photocytotoxicity to HeLa cancer cells (IC50 ≈ 0.23 µM) while being less toxic to HPL1D normal cells in red light. Cellular imaging using the emissive complex 1 shows mitochondrial localization and significant penetration into the HeLa tumor spheroids. Complex 2 shows supercoiled DNA photocleavage activity and apoptotic cell death through phototriggered generation of reactive oxygen species. The Co(III)-BODIPY prodrug conjugates exemplify new type of phototherapeutic agents with better efficacy than the organic dyes alone in the phototherapeutic window.

Quantification of Urine and Plasma Porphyrin Precursors Using LC-MS in Acute Hepatic Porphyrias: Improvement in Routine Diagnosis and in the Monitoring of Kidney Failure Patients.

BACKGROUND: The quantification of delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) in urine are the first-line tests for diagnosis and monitoring of acute hepatic porphyrias (AHP). Ion-exchange chromatography (IEC), which is time- and staff-consuming and limited to urine, is still the preferred method in many specialized laboratories, despite the development of mass spectrometry-based methods. METHODS: We describe a new LC-MS method that allows for rapid and simple quantification of ALA and PBG in urine and plasma with an affordable instrument that was used to analyze 2260 urine samples and 309 blood samples collected in 2 years of routine activity. The results were compared to those obtained with IEC, and urine reference ranges and concentrations in asymptomatic carriers were determined. Plasma concentrations were measured in healthy subjects and subgroups of symptomatic and asymptomatic AHP carriers. RESULTS: In urine, the clinical decision limits were not impacted by the change of method despite discrepancies in low absolute concentrations, leading to lower normal values. Two-thirds of asymptomatic AHP carriers (with the exception of coproporphyria carriers) showed an increased urine PBG concentration. Urine and plasma levels showed a good correlation except in patients with kidney disease in whom the urine/plasma ratio was relatively low. CONCLUSION: We described an LC-MS based method for the routine diagnosis and monitoring of AHP that allows for the detection of more asymptomatic carriers than the historical method. Blood analysis appears to be particularly relevant for patients with kidney disease, where urine measurement underestimates the increase in ALA and PBG levels.

Porphyrin precursors and risk of primary liver cancer in acute intermittent porphyria: A case-control study of 188 patients.

Acute intermittent porphyria (AIP) is a rare hereditary metabolic disease characterized by acute attacks and accumulation of the porphyrin precursors 5-aminolevulinic acid (ALA) and porphobilinogen (PBG). Patients with AIP have a high risk of primary liver cancer (PLC). We aimed to assess the association between porphyrin precursor excretion and the risk for PLC in patients with AIP. We studied 48 patients with AIP who developed PLC between 1987 and 2015 and 140 age and sex matched controls with AIP but no PLC. Data on all available urinary PBG and ALA samples collected from 1975 until 1 year before PLC diagnosis were analyzed and compared between cases and controls using logistic regression. Porphyrin precursor excretion was higher in patients with PLC (PBG median 7.9 [IQR 4.4-21.9] mmol/mol creatinine) than in controls (3.8 [1.2-9.8]) (adjusted odds ratio 1.07, 95% confidence interval: 1.02-1.12). None of the 28 patients with all registered samples below the upper limit of normal (ULN) developed PLC, and only one of the 45 patients with all samples <2× ULN developed PLC. Among non-PLC controls, ALA and PBG levels decreased after age 50-60 while an increasing trend was observed after age 65 among those who developed PLC. Increased urinary porphyrin precursors are associated with a high risk of developing PLC. Patients with normal levels appear to have a low risk while high or increasing ALA and PBG after age 65 indicates high risk, which should be considered in surveillance decisions.

Acute hepatic porphyrias: Recommendations for diagnosis and management with real-world examples.

Acute hepatic porphyria (AHP) is a group of four rare inherited diseases, each resulting from a deficiency in a distinct enzyme in the heme biosynthetic pathway. Characterized by acute neurovisceral symptoms that may mimic other medical and psychiatric conditions, lack of recognition of the disease often leads to a delay in diagnosis and initiation of effective treatment. Biochemical testing for pathway intermediates that accumulate when the disease is active forms the basis for screening and establishing a diagnosis. Subsequent genetic analysis identifies the pathogenic variant, supporting screening of family members and genetic counseling. Management of AHP involves avoidance of known exogenous and hormonal triggers, symptomatic treatment, and prevention of recurrent attacks. Here we describe six case studies from our own real-world experience to highlight current recommendations and challenges associated with the diagnosis and long-term management of the disease.

A Tetrazine-Caged Carbon-Dipyrromethene as a Bioorthogonally Activatable Fluorescent Probe.

A water-soluble 1,2,4,5-tetrazine-substituted carbon-dipyrromethene (C-DIPY) was synthesized from the previously reported carbonyl pyrrole dimer through a two-step procedure. Owing to the presence of a tetrazine moiety, the fluorescence emission of this compound was largely quenched in phosphate-buffered saline at pH 7.4. Upon addition of a bicyclo[6.1.0]non-4-yne (BCN) derivative, the tetrazine-based quenching component of the compound was disrupted through the inverse electron-demand Diels-Alder reaction to restore the fluorescence in up to 6.6-fold. This bioorthogonal activation was also demonstrated using U-87 MG human glioblastoma cells, in which the fluorescence intensity of this C-DIPY could be enhanced by 8.7-fold upon post-incubation with the BCN derivative. The results showed that this tetrazine-caged C-DIPY can serve as a bioorthogonally activatable fluorescent probe for bioimaging. The compound, however, was found to reside preferentially in the lysosomes instead of the mitochondria of the cells as predicted based on its cationic character, which could be attributed to its energy-dependent endocytic cellular uptake pathway, for which lysosomes are the end station.

Cryptogenic Abdominal Pain: Recognizing False Leads.

BACKGROUND Lead toxicity is a rare yet serious condition which can be difficult to diagnose due to vague presenting symptoms. Other pathologies can also mimic the symptoms of chronic lead toxicity, making an already difficult diagnosis more challenging. There are multiple environmental and occupational contributors to lead toxicity. A thorough history and an open differential is the key to diagnosing and treating this rare disease. With increasing diversity of our patient population, we should keep an open differential, as the epidemiological features of presenting concerns have diversified as well. CASE REPORT A 47-year-old woman presented with persistent nonspecific abdominal pain despite extensive prior work, surgeries and a prior diagnosis of porphyria. This patient was eventually diagnosed as having lead toxicity when her most recent work-up for abdominal pain revealed no urine porphobilinogen and a high lead level. The cause of lead toxicity was attributed to be an eye cosmetic called "Surma", which can have variable lead levels. Chelation therapy was advised for the patient. CONCLUSIONS It is important to recognize the difficulty in this challenging diagnosis for nonspecific abdominal pain and to eliminate the mimickers. This case is interesting because the patient was initially diagnosed with porphyria, highlighting how heavy metals, lead in this case, can lead to a false-positive diagnosis of porphyria. Accurate diagnosis requires awareness of the role of urine porphobilinogen, checking lead levels, and an open differential. This case also emphasizes the importance of avoiding anchor bias to make a timely diagnosis of lead toxicity.

Cinnamoyl Dipyrromethenes as Fluorescence Zinc(II) Ion Sensor.

Friedel-Crafts acylation of dipyrromethane with cinnamoyl chloride was conducted to obtain dicinnamoyl dipyrromethane compounds 3 and 4. Both compounds were subsequently oxidized by DDQ to produce dicinnamoyl dipyrromethene ligands (DC-1 and DC-2). A large bathochromic shift compared to dipyromethene (D) was observed at 95 nm for DC-1 and 67 nm for DC-2. Both compounds showed remarkable chelation-enhanced fluorescence (CHEF) upon addition of zinc(II) ions. Similar to the quadrupolar system, DC-1 exhibited absorption and emission near the optical windows of the tissue. However, asymmetrical DC-2 had a better "turn-on" CHEF, with a fluorescence intensity that was 22 times higher than that of compound D. The DC-2 ligand also showed a limit of detection (LOD) of up to 3.0×10-8  M and selectivity toward zinc(II) ions compared to alkali and alkaline earth metal ions.

AGA Clinical Practice Update on Diagnosis and Management of Acute Hepatic Porphyrias: Expert Review.

DESCRIPTION: The acute hepatic porphyrias (AHP) are rare, inborn errors of heme-metabolism and include acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and porphyria due to severe deficiency of 5-aminolevulinic acid dehydratase. Acute intermittent porphyria is the most common type of AHP, with an estimated prevalence of patients with symptoms of approximately 1 in 100,000. The major clinical presentation involves attacks of severe pain, usually abdominal and generalized, without peritoneal signs or abnormalities on cross-sectional imaging. Acute attacks occur mainly in women in their childbearing years. AHP should be considered in the evaluation of all patients, and especially women aged 15-50 years with recurrent severe abdominal pain not ascribable to common causes. The screening tests of choice include random urine porphobilinogen and δ-aminolevulinic acid corrected to creatinine. All patients with elevations in urinary porphobilinogen and/or δ-aminolevulinic acid should initially be presumed to have AHP. The cornerstones of management include discontinuation of porphyrinogenic drugs and chemicals, administration of oral or intravenous dextrose and intravenous hemin, and use of analgesics and antiemetics. Diagnosis of AHP type can be confirmed after initial treatment by genetic testing for pathogenic variants in HMBS, CPOX, PPOX, and ALAD genes. AHP is also associated with chronic symptoms and long-term risk of systemic arterial hypertension, chronic renal and liver disease, and hepatocellular carcinoma. Patients who have recurrent acute attacks (4 or more per year) should be considered for prophylactic therapy with intravenous hemin or subcutaneous givosiran. Liver transplantation is curative and reserved for patients with intractable symptoms who have failed other treatment options. METHODS: This expert review was commissioned and approved by the American Gastroenterological Association (AGA) Institute Clinical Practice Updates Committee (CPUC) and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership, and underwent internal peer review by the CPUC and external peer review through standard procedures of Gastroenterology. These Best Practice Advice (BPA) statements were drawn from a review of the published literature and from expert opinion. Because systematic reviews were not performed, these BPA statements do not carry formal ratings of the quality of evidence or strength of the presented considerations. Best Practice Advice Statements BEST PRACTICE ADVICE 1: Women aged 15-50 years with unexplained, recurrent severe abdominal pain without a clear etiology after an initial workup should be considered for screening for an AHP. BEST PRACTICE ADVICE 2: Initial diagnosis of AHP should be made by biochemical testing measuring δ-aminolevulinic acid, porphobilinogen, and creatinine on a random urine sample. BEST PRACTICE ADVICE 3: Genetic testing should be used to confirm the diagnosis of AHP in patients with positive biochemical testing. BEST PRACTICE ADVICE 4: Acute attacks of AHP that are severe enough to require hospital admission should be treated with intravenous hemin, given daily, preferably into a high-flow central vein. BEST PRACTICE ADVICE 5: In addition to intravenous hemin, management of acute attacks of AHP should include pain control, antiemetics, management of systemic arterial hypertension, tachycardia, and hyponatremia, and hypomagnesemia, if present. BEST PRACTICE ADVICE 6: Patients should be counseled to avoid identifiable triggers that may precipitate acute attacks, such as alcohol and porphyrinogenic medications. BEST PRACTICE ADVICE 7: Prophylactic heme therapy or givosiran, administered in an outpatient setting, should be considered in patients with recurrent attacks (4 or more per year). BEST PRACTICE ADVICE 8: Liver transplantation for AHP should be limited to patients with intractable symptoms and significantly decreased quality of life who are refractory to pharmacotherapy. BEST PRACTICE ADVICE 9: Patients with AHP should be monitored annually for liver disease. BEST PRACTICE ADVICE 10: Patients with AHP, regardless of the severity of symptoms, should undergo surveillance for hepatocellular carcinoma, beginning at age 50 years, with liver ultrasound every 6 months. BEST PRACTICE ADVICE 11: Patients with AHP on treatment should undergo surveillance for chronic kidney disease annually with serum creatinine and estimated glomerular filtration rate. BEST PRACTICE ADVICE 12: Patients should be counseled on the chronic and long-term complications of AHP, including neuropathy, chronic kidney disease, hypertension, and hepatocellular carcinoma, and need for long-term monitoring.

Stability of Dibromo-Dipyrromethene Complexes Coordinated with B, Zn, and Cd in Solutions of Various Acidities.

The spectral luminescent properties of dipyrromethenates halogenated with bromine on both ends of the long axis and coordinated using boron fluoride, zinc, or cadmium in neutral ethanol and acidified with hydrochloric acid solutions were studied. The constants of the acid-base equilibrium of the complexes in the proton-donor solvents in the ground and excited states was determined. The mechanisms of complex protonation were discussed, depending on the structure of the compounds. The electronic structures of the neutral and protonated compounds were modeled and analyzed based on the quantum-chemical method. The structures and spectral-luminescence properties were calculated using the SMD model of ethanol solvent using the TD-DFT theory with the B3LYP functional and the composite def2-SVP/def2-TZVP/def2-TZVPP_ECP basis sets, depending on the atomic number of the elements.

ALAD Inhibition by Porphobilinogen Rationalizes the Accumulation of δ-Aminolevulinate in Acute Porphyrias.

Patients with major forms of acute hepatic porphyria present acute neurological attacks with overproduction of porphobilinogen (PBG) and δ-aminolevulinic acid (ALA). Even if ALA is considered the most likely agent inducing the acute symptoms, the mechanism of its accumulation has not been experimentally demonstrated. In the most frequent form, acute intermittent porphyria (AIP), inherited gene mutations induce a deficiency in PBG deaminase; thus, accumulation of the substrate PBG is biochemically obligated but not that of ALA. A similar scenario is observed in other forms of acute hepatic porphyria (i.e., porphyria variegate, VP) in which PBG deaminase is inhibited by metabolic intermediates. Here, we have investigated the molecular basis of δ-aminolevulinate accumulation using in vitro fluxomics monitored by NMR spectroscopy and other biophysical techniques. Our results show that porphobilinogen, the natural product of δ-aminolevulinate deaminase, effectively inhibits its anabolic enzyme at abnormally low concentrations. Structurally, this high affinity can be explained by the interactions that porphobilinogen generates with the active site, most of them shared with the substrate. Enzymatically, our flux analysis of an altered heme pathway demonstrates that a minimum accumulation of porphobilinogen will immediately trigger the accumulation of δ-aminolevulinate, a long-lasting observation in patients suffering from acute porphyrias.

Mitochondria-Targeting Boron Dipyrromethene Based Photosensitizers for Enhanced Photodynamic Therapy: Synthesis, Optical Properties, and in†vitro Biological Activity.

Increasing Investigations show that photosensitizers (PSs) which target mitochondria are useful for enhancing photodynamic therapy (PDT) efficacy. Herein, we carefully designed and synthesized four triphenylphosphonium (TPP)-modified boron dipyrromethene (BDP)-based PSs through Cu(I)-assisted "3+2" cycloaddition reaction. All of them exhibit intense red light absorption with maxima between 659 and 663 nm, considerable fluorescence emission with quantum yields of 0.16-0.23, high singlet oxygen generation efficiency ranging from 0.22 to 0.34, excellent mitochondria-targeting ability, and good biocompatibility. Upon illumination, they induce significant cancer cell death through a mitochondria-related apoptosis pathway. The IC50 values of these BDP dyes against MCF-7 cells were determined to be as low as 0.046-0.113 µM under rather low dosage of light irradiation (1.5 J ⋅ cm-2 ).

BODIPY-based metal-organic frameworks as efficient electrochemiluminescence emitters for telomerase detection.

A boron dipyrromethene (BODIPY)-based metal-organic framework (MOF) nanoemitter was for the first time designed with enhanced electrochemiluminescence (ECL) intensity due to the suppression of non-radiative dissipation originating from the ordered arrangement of BODIPY molecules in the framework. Thus, an ECL biosensor was developed for telomerase detection with excellent performance in real samples.

A Hypoxia-Activated Prodrug Conjugated with a BODIPY-Based Photothermal Agent for Imaging-Guided Chemo-Photothermal Combination Therapy.

Hypoxia-activated prodrugs (HAPs) have drawn increasing attention for improving the antitumor effects while minimizing side effects. However, the heterogeneous distribution of the hypoxic region in tumors severely impedes the curative effect of HAPs. Additionally, most HAPs are not amenable to optical imaging, and it is difficult to precisely trace them in tissues. Herein, we carefully designed and synthesized a multifunctional therapeutic BAC prodrug by connecting the chemotherapeutic drug camptothecin (CPT) and the fluorescent photothermal agent boron dipyrromethene (BODIPY) via hypoxia-responsive azobenzene linkers. To enhance the solubility and tumor accumulation, the prepared BAC was further encapsulated into a human serum albumin (HSA)-based drug delivery system to form HSA@BAC nanoparticles. Since the CPT was caged by a BODIPY-based molecule at the active site, the BAC exhibited excellent biosafety. Importantly, the activated CPT could be quickly released from BAC and could perform chemotherapy in hypoxic cancer cells, which was ascribed to the cleavage of the azobenzene linker by overexpressed azoreductase. After irradiation with a 730 nm laser, HSA@BAC can efficiently generate hyperthermia to achieve irreversible cancer cell death by oxygen-independent photothermal therapy. Under fluorescence imaging-guided local irradiation, both in vitro and in vivo studies demonstrated that HSA@BAC exhibited superior antitumor effects with minimal side effects.

Identification and function analysis of yellow-leaf mutant (YX-yl) of broomcorn millet.

BACKGROUND: Broomcorn millet is highly tolerant to drought and barren soil. Changes in chlorophyll content directly affect leaf color, which subsequently leadsleading to poor photosynthetic performance and reduced crop yield. Herein, we isolated a yellow leaf mutant (YX-yl) using a forward genetics approach and evaluated its agronomic traits, photosynthetic pigment content, chloroplast ultrastructure, and chlorophyll precursors. Furthermore, the molecular mechanism of yellowing was explored using transcriptome sequencing. RESULTS: The YX-yl mutant showed significantly decreased plant height and low yield. The leaves exhibited a yellow-green phenotype and poor photosynthetic capacity during the entire growth period. The content of chlorophyll a, chlorophyll b, and carotenoids in YX-yl leaves was lower than that in wild-type leaves. Chlorophyll precursor analysis results showed that chlorophyll biosynthesis in YX-yl was hindered by the conversion of porphobilinogen to protoporphyrin IX. Examination of chloroplast ultrastructure in the leaves revealed that the chloroplasts of YX-yl accumulated on one side of the cell. Moreover, the chloroplast structure of YX-yl was degraded. The inner and outer membranes of the chloroplasts could not be distinguished well. The numbers of grana and grana thylakoids in the chloroplasts were low. The transcriptome of the yellowing mutant YX-yl was sequenced and compared with that of the wild type. Nine chlorophyll-related genes with significantly different expression profiles were identified: PmUROD, PmCPO, PmGSAM, PmPBDG, PmLHCP, PmCAO, PmVDE, PmGluTR, and PmPNPT. The proteins encoded by these genes were located in the chloroplast, chloroplast membrane, chloroplast thylakoid membrane, and chloroplast matrix and were mainly involved in chlorophyll biosynthesis and redox-related enzyme regulation. CONCLUSIONS: YX-yl is an ideal material for studying pigment metabolism mechanisms. Changes in the expression patterns of some genes between YX-yl and the wild type led to differences in chloroplast structures and enzyme activities in the chlorophyll biosynthesis pathway, ultimately resulting in a yellowing phenotype in the YX-yl mutant. Our findings provide an insight to the molecular mechanisms of leaf color formation and chloroplast development in broomcorn millet.

Boron Dipyrromethene-Based Phototheranostics for Near Infrared Fluorescent and Photoacoustic Imaging-Guided Synchronous Photodynamic and Photothermal Therapy of Cancer.

The regulation of photochemical properties of phototheranostics, especially the absorption, fluorescence, singlet oxygen (1O2) generation, and photothermal conversion efficiency, is a hot research topic. Here, we designed and synthesized four boron dipyrromethene (BODIPY) derivatives with high absorption coefficients and intense fluorescence in the near-infrared (NIR) region. The substituted electron-donating group significantly improved 1O2 generation and fluorescence of BODIPYs, whereas the electron-withdrawing group boosts photothermal conversion. These hydrophobic BODIPYs were further coated with DSPE-PEG-2000 to form water dispersible nanoparticles (NPs). Among these BODIPY NPs, the B-OMe-NPs with methoxyl substituted at the meso-position showed the highest 1O2 generation, a photothermal conversion efficiency of 66.5%, and an NIR fluorescence peak at 809 nm. In vitro and in vivo experiments demonstrated that B-OMe-NPs might be used for NIR fluorescent and photoacoustic imaging-guided photodynamic and photothermal therapy of cancer.

Self-Assembled Aza-Boron-Dipyrromethene for Ferroptosis-Boosted Sonodynamic Therapy.

The presence of apoptosis inhibition proteins renders the cancer cells resistant to apoptosis, severely compromising the antitumor efficacy of sonodynamic therapy (SDT). Here, an intelligent anticancer nanoplatform based on an Aza-boron-dipyrromethene dye (denoted as Aza-BDY) is elaborately established for ferroptosis augmented SDT through cysteine (Cys) starvation. After endocytosis by tumor cells, Aza-BDY serves as both a ferroptosis inducing agent and a sonosensitizer for tumor treatment. The specific Cys response facilitates the disruption of redox homeostasis and initiation of cellular ferroptosis. Meanwhile, the released sonosensitizer causes efficient SDT and augments ferroptosis under ultrasound irradiation. Detailed in vitro and in vivo investigations demonstrate that the synergistic effect of Cys depletion and singlet oxygen (1 O2 ) generation significantly induces cancer-cell death and suppresses tumor proliferation with a high inhibition rate of 97.5 %.

Disease burden in patients with acute hepatic porphyria: experience from the phase 3 ENVISION study.

BACKGROUND: Acute hepatic porphyria (AHP) is a family of four rare genetic diseases, each involving deficiency in a hepatic heme biosynthetic enzyme. Resultant overproduction of the neurotoxic intermediates δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) leads to disabling acute neurovisceral attacks and progressive neuropathy. We evaluated the AHP disease burden in patients aged ≥ 12 years in a post hoc analysis of the Phase 3, randomized, double-blind, placebo-controlled ENVISION trial of givosiran (NCT03338816), an RNA interference (RNAi) therapeutic that targets the enzyme ALAS1 to decrease ALA and PBG production. We analyzed baseline AHP severity via chronic symptoms between attacks, comorbidities, concomitant medications, hemin-associated complications, and quality of life (QOL) and evaluated givosiran (2.5 mg/kg monthly) in patients with and without prior hemin prophylaxis on number and severity of attacks and pain scores during and between attacks. RESULTS: Participants (placebo, n = 46; givosiran, n = 48) included patients with low and high annualized attack rates (AARs; range 0-46). At baseline, patients reported chronic symptoms (52%), including nausea, fatigue, and pain; comorbidities, including neuropathy (38%) and psychiatric disorders (47%); concomitant medications, including chronic opioids (29%); hemin-associated complications (eg, iron overload); and poor QOL (low SF-12 and EuroQol visual analog scale scores). A linear relationship between time since diagnosis and AAR with placebo suggested worsening of disease over time without effective treatment. Givosiran reduced the number and severity of attacks, days with worst pain scores above baseline, and opioid use versus placebo. CONCLUSIONS: Patients with AHP, regardless of annualized attack rates, have considerable disease burden that may partly be alleviated with givosiran.

Phenylthiol-BODIPY-based supramolecular metallacycles for synergistic tumor chemo-photodynamic therapy.

The development of more effective tumor therapy remains challenging and has received widespread attention. In the past decade, there has been growing interest in synergistic tumor therapy based on supramolecular coordination complexes. Herein, we describe two triangular metallacycles (1 and 2) constructed by the formation of pyridyl boron dipyrromethene (BODIPY)-platinum coordination. Metallacycle 2 had considerable tumor penetration, as evidenced by the phenylthiol-BODIPY ligand imparting red fluorescent emission at ∼660 nm, enabling bioimaging, and transport visualization within the tumor. Based on the therapeutic efficacy of the platinum(II) acceptor and high singlet oxygen (1O2) generation ability of BODIPY, 2 was successfully incorporated into nanoparticles and applied in chemo-photodynamic tumor therapy against malignant human glioma U87 cells, showing excellent synergistic therapeutic efficacy. A half-maximal inhibitory concentration of 0.35 µM was measured for 2 against U87 cancer cells in vitro. In vivo experiments indicated that 2 displayed precise tumor targeting ability and good biocompatibility, along with strong antitumor effects. This work provides a promising approach for treating solid tumors by synergistic chemo-photodynamic therapy of supramolecular coordination complexes.

Surfactant mediated suppression of aggregation and excited state ring puckering process in Pyrromethene 597-Application in water based dye laser.

Water is being considered as an economical, safe and environmental friendly alternative solvent for dye lasers. However, the use of water in dye laser is restricted due to the formation of non-emissive aggregates of dye molecules. In the present study we have explored the possibility of the use of commercially available surfactant molecules for the water based laser of Pyrromethene 597 (PM597) dye, which has emerged as an alternative for more commonly used Rhodamine dyes in dye laser systems. Our studies show that in water, PM597 forms non-emissive aggregates which can be dissociated into monomeric dye molecules by adding common surfactants. Further, the high microviscosity in the micellar media retarded energy wasting ring puckering process in the excited state of the dye leading to the increase in its emission yield and excited state lifetime to a significant extent. It has been demonstrated that the emission yield and excited state lifetime in surfactant solution is relatively higher than in ethanol, the most commonly used organic solvent for dye lasers. Lasing action has been demonstrated in the aqueous solution of dye and lasing efficiency is found to be comparable to ethanol.

Phototoxicity of BODIPY in long-term imaging can be reduced by intramolecular motion.

For long-term live-cell fluorescence imaging and biosensing, it is crucial to work with a dye that has high fluorescence quantum yield and photostability without being detrimental to the cells. In this paper, we demonstrate that neutral boron-dipyrromethene (BODIPY)-based molecular rotors have great properties for high-light-dosage demanding live-cell fluorescence imaging applications that require repetitive illuminations. In molecular rotors, an intramolecular rotation (IMR) allows an alternative route for the decay of the singlet excited state (S1) via the formation of an intramolecular charge transfer state (CT). The occurrence of IMR reduces the probability of the formation of a triplet state (T1) which could further react with molecular oxygen (3O2) to form cytotoxic reactive oxygen species, e.g., singlet oxygen (1O2). We demonstrate that the oxygen-related nature of the phototoxicity for BODIPY derivatives can be significantly reduced if a neutral molecular rotor is used as a probe. The studied neutral molecular rotor probe shows remarkably lower phototoxicity when compared with both the non-rotating BODIPY derivative and the cationic BODIPY-based molecular rotor in different light dosages and dye concentrations. It is also evident that the charge and localization of the fluorescent probe are as significant as the IMR in terms of the phototoxicity in a long-term live-cell imaging.