A Comparison of the Photophysical, Electrochemical and Cytotoxic Properties of meso-(2-, 3- and 4-Pyridyl)-BODIPYs and Their Derivatives.

Boron dipyrromethene (BODIPY) dyes bearing a pyridyl moiety have been used as metal ion sensors, pH sensors, fluorescence probes, and as sensitizers for phototherapy. A comparative study of the properties of the three structural isomers of meso-pyridyl-BODIPYs, their 2,6-dichloro derivatives, and their corresponding methylated cationic pyridinium-BODIPYs was conducted using spectroscopic and electrochemical methods, X-ray analyses, and TD-DFT calculations. Among the neutral derivatives, the 3Py and 4Py isomers showed the highest relative fluorescence quantum yields in organic solvents, which were further enhanced 2-4-fold via the introduction of two chlorines at the 2,6-positions. Among the cationic derivatives, the 2catPy showed the highest relative fluorescence quantum yield in organic solvents, which was further enhanced by the use of a bulky counter anion (PF6-). In water, the quantum yields were greatly reduced for all three isomers but were shown to be enhanced upon introduction of 2,6-dichloro groups. Our results indicate that 2,6-dichloro-meso-(2- and 3-pyridinium)-BODIPYs are the most promising for sensing applications. Furthermore, all pyridinium BODIPYs are highly water-soluble and display low cytotoxicity towards human HEp2 cells.

Radiation-induced synthetic lethality: combination of poly(ADP-ribose) polymerase and RAD51 inhibitors to sensitize cells to proton irradiation.

Although improvements in radiation therapy were made over the years, radioresistance is still a major challenge. Cancer cells are often deficient for DNA repair response, a feature that is currently exploited as a new anti-cancer strategy. In this context, combination of inhibitors targeting complementary pathways is of interest to sensitize cells to radiation. In this work, we used PARP (Olaparib) and RAD51 (B02) inhibitors to radiosensitize cancer cells to proton and X-ray radiation. More particularly, Olaparib and B02 were used at concentration leading to limited cytotoxic (alone or in combination) but increasing cell death when the cells were irradiated. We showed that, although at limited concentration, Olaparib and B02 were able to radiosensitize different cancer cell lines, i.e. lung and pancreatic cancer cells. Antagonistic, additive or synergistic effects were observed and correlated to cell proliferation rate. The inhibitors enhanced persistent DNA damage, delayed apoptosis, prolonged cell cycle arrest and senescence upon irradiation. These results demonstrated that radiation-induced synthetic lethality might widen the therapeutic window, hence extending the use of PARP inhibitors to patients without BRCAness.

Effect of substituents on Stokes shift of BODIPY and its application in designing bioimaging probes.

BODIPY-based probes have excellent fluorescence properties. However, small Stokes shifts approximately 5-15 nm greatly affect their detection sensitivity. In this study, we compared the Stokes shifts of reported BODIPY-based probes with various of substituents, and found that the phenyl groups on the specific position of BODIPY core could expand the Stokes shift of BODIPY-based probes, and methoxy groups on these phenyl substituents could enhance such effects. Then, by quantum chemical calculations, we found that the number of methoxy groups might also have obvious effect on the Stokes shift of BODIPY. Taking nitric oxide (NO) as analyte, 4,4-difluoro-8-(3,4-diaminophenyl)-3,5-bis(2,4-dimethoxyphenyl)-4-bora-3a,4a-diaza-s-indancene (DMOPB) with diaminophenyl substituents has been designed and synthesized. Compared with monomethoxy-phenyl substituted BODIPY-based probes (MOPBs) in our previous work, Stokes shift of DMOPB was expanded by 10 nm when using dimethoxyphenyl instead of monomethoxyphenyl, which is basically consistent with the quantum chemistry calculation of 11 nm. DMOPB can react with NO in only 2 min to form the triazole DMOPB-T with a fluorescence quantum yield of 0.32. An excellent linear relationship was observed in the range of NO concentration from 0.5 µM to 4 µM and the detection limit was 1 nM. The experimental results indicate that DMOPB with high sensitivity, excellent selectivity, low toxicity and dark background can be a great candidate for imaging NO in cells and tissues. Considering the lack of practical way to increase Stokes shift of small-molecule fluorescent probes based on specific fluorophore, the proposed strategy has great potential for the designing of probes with large Stokes shift.

Assessing and Mitigating the Hazard Potential of Two-Dimensional Materials.

The family of two-dimensional (2D) materials is comprised of a continually expanding palette of unique compositions and properties with potential applications in electronics, optoelectronics, energy capture and storage, catalysis, and nanomedicine. To accelerate the implementation of 2D materials in widely disseminated technologies, human health and environmental implications need to be addressed. While extensive research has focused on assessing the toxicity and environmental fate of graphene and related carbon nanomaterials, the potential hazards of other 2D materials have only recently begun to be explored. Herein, the toxicity and environmental fate of postcarbon 2D materials, such as transition metal dichalcogenides, hexagonal boron nitride, and black phosphorus, are reviewed as a function of their preparation methods and surface functionalization. Specifically, we delineate how the hazard potential of 2D materials is directly related to structural parameters and physicochemical properties and how experimental design is critical to the accurate elucidation of the underlying toxicological mechanisms. Finally, a multidisciplinary approach for streamlining the hazard assessment of emerging 2D materials is outlined, thereby providing a pathway for accelerating their safe use in a range of technologically relevant contexts.

Small BODIPY Probes for Combined Dual (19) F†MRI and Fluorescence Imaging.

The combination of the two complementary imaging modalities (19) F magnetic resonance imaging (MRI) and fluorescence imaging (FLI) possesses high potential for biological and medical applications. Herein we report the first design, synthesis, dual detection validation, and cytotoxic testing of four promising BODIPY dyes for dual (19) F MRI-fluorescence detection. Using straightforward Steglich reactions, small fluorinated alcohols were easily covalently tethered to a BODIPY dye in high yields, leaving its fluorescence properties unaffected. The synthesized compounds were analyzed with various techniques to demonstrate their potential utility in dual imaging. As expected, the chemically and magnetically equivalent trifluoromethyl groups of the agents exhibited a single NMR signal. The determined longitudinal relaxation times T1 and the transverse relaxation times T2 , both in the lower second range, enabled the imaging of four compounds in vitro. The most auspicious dual (19) F MRI-fluorescence agent was also successfully imaged in a mouse post-mortem within a 9.4 T small-animal tomograph. Toxicological assays with human cells (primary HUVEC and HepG2 cell line) also indicated the possibility for animal testing.

Tavaborole, a Novel Boron-Containing Small Molecule Pharmaceutical Agent for Topical Treatment of Onychomycosis: II. Prenatal and Postnatal Developmental Toxicity and Maternal Function Study.

Tavaborole is a topical antifungal agent approved by the US Food and Drug Administration for the treatment of toenail onychomycosis. The effects of tavaborole on gestation, parturition (delivery, labor), offspring development, and survival during the perinatal and postnatal periods were assessed in mated female rats. Females (F0 generation) were administered single daily oral (gavage) doses of 15, 60, or 100 mg/kg/d from gestation day 6 through lactation day 20. The females were allowed to deliver naturally and rear their offspring until lactation day 21, at which time the F0 females were euthanized. One male and female from each litter were selected (F1 generation) and retained for assessments, including growth, neurobehavior, fertility, and their ability to produce an F2 generation. Reproductive and offspring parameters were determined for the F1 and F2 generations, as applicable. F1 females and F2 pups were euthanized on postnatal day 7. In the F0 females, decreased activity was observed in the 100 mg/kg/d dose group. Excess salivation was observed in the 60 and 100 mg/kg/d dose groups (slight to moderate), however, this finding was not considered adverse. There were no tavaborole-related effects on the growth, viability, development, neurobehavioral assessments, or reproductive performance of the F1 generation. Survivability and mean body weight of the F2 pups were unaffected. The no observed adverse effect level (NOAEL) for maternal toxicity (F0 generation) was 60 mg/kg/d, based on the decreased activity observed in the 100 mg/kg/d dose group. The NOAEL for the offspring effects was ≥100 mg/kg/d, based on the lack of test article-related changes.

Inhibition of Toll-like receptor-mediated inflammation in vitro and in vivo by a novel benzoxaborole.

Pro-inflammatory cytokines play a critical role in the development of autoimmune and inflammatory diseases. Targeting the cytokine environment has proven efficient for averting inflammation. In this study, we reported that 6-[4-(aminomethyl)-2-chlorophenoxyl]benzo[c][1,2]oxaborol-1(3H)-ol (AN3485), a benzoxaborole analog, inhibited TLR2-, TLR3-, TLR4-, and TLR5-mediated TNF-α, IL-1ß, and IL-6 release from human PBMCs and isolated monocytes with IC(50) values ranging from 18 to 580 nM, and the inhibition was mediated at the transcriptional level. Topical administration of AN3485 significantly reduced PMA-induced contact dermatitis and oxazolone-induced delayed-type hypersensitivity in mice, indicating its capability of penetrating skin and potential topical application in skin inflammation. Oral administration of AN3485 showed dose-dependent suppression of LPS-induced TNF-α and IL-6 production in mice with an ED(90) of 30 mg/kg. Oral AN3485, 35 mg/kg, twice a day, suppressed collagen-induced arthritis in mice over a 20-day period. The potent anti-inflammatory activity in in vitro and in vivo disease models makes AN3485 an attractive therapeutic lead for a variety of cutaneous and systemic inflammatory diseases.

In vitro investigation of the cellular toxicity of boron nitride nanotubes.

Nanotubes present one of the most promising opportunities in nanotechnology with a plethora of applications in nanoelectronics, mechanical engineering, as well as in biomedical technology. Due to their structure and some physical properties, boron nitride (BN) nanotubes (BNNTs) possess several advantages over carbon nanotubes (CNTs), and they are now commercially produced and used on a large scale. The human and environmental exposure to BN nanomaterials is expected to increase in the near future, and their biological responses need to be examined. Using complementary assays, we have extensively investigated the effects of BNNTs on the viability and metabolic status of different cell types: on the one hand, the effects on cells present in the lung alveoli, and on the other hand, on human embryonic kidney (HEK) cells. Our results indicate that BNNTs are cytotoxic for all cell types studied and, in most cases, are more cytotoxic than CNTs in their pristine (p-CNT) and functionalized (f-CNT) form. However, the level of toxicity and the prominent morphological alterations in the cell populations withstanding BNNT exposure are cell-type-dependent. For instance, BNNTs induced extensive multinucleated giant cell formation in macrophages and increased levels of eosinophilia in fibroblasts. Finally, our results point the toxicity of tubular nanomaterials to be strongly correlated with the cellular accumulation enhanced for straight nanotubes.

Assessing cytotoxicity of boron nitride nanotubes: Interference with the MTT assay.

Thanks to a non-covalent wrapping with glycol-chitosan, highly biocompatible and highly concentrated dispersions of boron nitride nanotubes were obtained and tested on human neuroblastoma cells. A systematic investigation of the cytotoxicity of these nanovectors with several complementary qualitative and quantitative assays allowed a strong interference with the MTT metabolic assay to be highlighted, similar to a phenomenon already observed for carbon nanotubes, that would wrongly suggest toxicity of boron nitride nanotubes. These results confirm the high complexity of these new nanomaterials, and the needing of extensive investigations on their exciting potential applications in the biomedical field.

Pharmacokinetics and effects after intravenous administration of high-dose boron to rat.

Boron (B) compounds have been widely used in the chemical industry, agriculture, and environmental science. The kinetics and toxicity of B were studied by analyzing several serum and urine parameters after a single intravenous injection of sodium tetraborate solution (B: 85.7 mg/kg) in Wistar male rats. Blood samples were removed at 0, 1, 2, 4, and 6 h after injection. The serum parameters studied included: B, Na, Ca, K, P, Mg, gamma-GTP, AST, ALT, BUN, Cr, CK, LDH and ALD. Plasma concentration-time profiles of B were evaluated by a nonlinear least-squares method for fitting data to polyexponential equations and calculation of relevant pharmacokinetic parameters. Urine samples were collected from the bladder following infusion. The urinary parameters that were studied included urine volume and excretion of B, Cr and NAG. Results indicated that a two-compartment model could describe the elimination of B from plasma after intravenous administration. Urine volume significantly increased. A diuretic effect of B was noted.

Specific inhibition of plasma kallikrein modulates chronic granulomatous intestinal and systemic inflammation in genetically susceptible rats.

The kallikrein-kinin (K-K) (contact) system is activated during acute and chronic relapsing phases of enterocolitis induced in genetically susceptible Lewis rats by intramural injection of peptidoglycan-polysaccharide (PG-APS). Using the selective plasma kallikrein inhibitor P8720, we investigate whether activation of the K-K system plays a primary role in chronic granulomatous intestinal and systemic inflammation in this model. Group I (negative control) received human serum albumin intramurally. Group II (treatment) received PG-APS intramurally and P8720 orally. Group III (positive control) received PG-APS intramurally and albumin orally. P8720 attenuated the consumption of the contact proteins, high molecular weight kininogen (P<0.03), and factor XI (P<0.04) in group II vs. group III. P8720 decreased chronic intestinal inflammation measured by blinded gross (P<0.01) and histologic (P<0.0005) scores as well as systemic complications (arthritis, splenomegaly, hepatomegaly, leukocytosis, and acute-phase reaction) (P<0.01) in group II as compared with group III. We conclude that relapsing chronic enterocolitis and systemic complications are in part due to plasma K-K system activation, and that inhibition of this pathway is a potential therapeutic approach to human inflammatory bowel disease and associated extraintestinal manifestations.

Selective tumor kill of cerebral glioma by photodynamic therapy using a boronated porphyrin photosensitizer.

The prognosis for patients with the high-grade cerebral glioma glioblastoma multiforme is poor. The median survival for primary tumors is < 12 months, with most recurring at the site of the original tumor, indicating that a more aggressive local therapy is required to eradicate the unresectable "nests" of tumor cells invading into adjacent brain. Two adjuvant therapies with the potential to destroy these cells are porphyrin-sensitized photodynamic therapy (PDT) and boron-sensitized boron neutron capture therapy (BNCT). The ability of a boronated porphyrin, 2,4-(alpha, beta-dihydroxyethyl) deuteroporphyrin IX tetrakiscarborane carboxylate ester (BOPP), to act as a photosensitizing agent was investigated in vitro with the C6 rat glioma cell line and in vivo with C6 cells grown as an intracerebral tumor after implantation into Wistar rats. These studies determined the doses of BOPP and light required to achieve maximal cell kill in vitro and selective tumor kill in vivo. The data show that BOPP is more dose effective in vivo by a factor of 10 than the current clinically used photosensitizer hematoporphyrin derivative and suggest that BOPP may have potential as a dual PDT/BNCT sensitizer.

Acute and subacute toxicity of 10B-paraboronophenylalanine.

The acute and subacute toxicities of 10B-paraboronophenylalanine (10B-BPA) were investigated in the rat, according to the Good Laboratory Practice Standard for safety studies on drugs in Japan. In the acute toxicity test of 10B-BPA, LD50 values of acidic 10B-BPA for intraperitoneal and subcutaneous injections were 640 mg/kg for male and 710 mg/kg for female rats, and more than 1,000 mg/kg for male and female rats, respectively. The LD50 values of neutral 10B-BPA for intraperitoneal and subcutaneous injections were more than 3,000 mg/kg for male and female rats. The difference in LD50 values between acidic and neutral 10B-BPA may be attributed to the acidity of material. From the subacute toxicity test, in which the rats were injected daily subcutaneously for 28 days, the following toxic effects of 10B-BPA were observed. Increase in ketone level in the urine was induced in all rats treated with 10B-BPA. High dose of 10B-BPA (1,500 mg/kg) induced increase in spleen weight and reticulocyte count, and decrease in hemoglobin count, thereby suggesting that 10B-BPA causes hemolysis. Increases in the leukocyte count and the ratio of neutrophils and lymphocytes were also observed in rats treated with a high dose of 10B-BPA. This may be attributed to local reactions at the injection site. There were no significant differences in the findings between control rats and rats treated with a low dose of 10B-BPA (300 mg/kg). Thus, low doses of neutral 10B-BPA may be available for use as a drug.