UV-vis Spectral Changes Research Articles

Amphiphilic Chlorin-β-cyclodextrin Conjugates in Photo-Triggered Drug Delivery: The Role of Aggregation.

Conjugates of chlorins with β-cyclodextrin connected either directly or via a flexible linker were prepared. In aqueous medium these amphiphilic conjugates were photostable, produced singlet oxygen at a rate similar to clinically used temoporfin and formed irregular nanoparticles via aggregation. Successful loading with the chemotherapeutic drug tamoxifen was evidenced in solution by the UV-Vis spectral changes and dynamic light scattering profiles. Incubation of MCF-7 cells with the conjugates revealed intense spotted intracellular fluorescence suggestive of accumulation in endosome/lysosome compartments, and no dark toxicity. Incubation with the tamoxifen-loaded conjugates revealed also practically no dark toxicity. Irradiation of cells incubated with empty conjugates at 640 nm and 4.18 J/cm2 light fluence caused >50 % cell viability reduction. Irradiation following incubation with tamoxifen-loaded conjugates resulted in even higher toxicity (74 %) indicating that the produced reactive oxygen species had triggered tamoxifen release in a photochemical internalization (PCI) mechanism. The chlorin-β-cyclodextrin conjugates displayed less-lasting effects with time, compared to the corresponding porphyrin-β-cyclodextrin conjugates, possibly due to lower tamoxifen loading of their aggregates and/or their less effective lodging in the cell compartments' membranes. The results suggest that further to favorable photophysical properties, other parameters are important for the in vitro effectiveness of the photodynamic systems.

UV–visible spectral changes of gamma irradiated olive leaves extract

Olive leaves benefits are less well known, despite having potential health benefits that could make them a valuable addition to a daily diet, compared to olive oil, which is well known for the many benefits it provides. The antioxidant capacity of olive leaves extract (OLE) is higher than that of the most known powerful antioxidants, such as vitamins C and E or pure hydroxytyrosol. The aim of this study was first to maximize the bioactive compounds in extra virgin olive oil (EVOO) by enriching it with olive leaves; the EVOO acts as an extraction solvent, and a study of the macerating period was carried out to select the best macerating period to improve the stabilization of the bioactive compounds in the olive oil matrix. Once the best macerating period was selected (7 days), OLE was gamma-irradiated with a dose of 25 kGy to assess its oxidative stability. To this end, UV–visible spectroscopy was used to perform stability and quality analysis of the OLE during a macerating period of 21 days and after irradiation. The results of this study show an extremely significant (p < 0.0001) improvement in the quality parameters (K232, K270, and ΔK) and in total carotenoids and chlorophylls, assessed by K470 and K670, among all the macerating periods of OLE compared to the control group. Regarding the irradiated OLE compared to the irradiated EVOO, there was an extremely significant (p < 0.0001) difference in ΔK. In addition, there was a significant decrease in total carotenoids and chlorophylls in the irradiated EVOO compared to the irradiated OLE. In conclusion, olive leaves extract in olive oil could be used as a free radical scavenger in food irradiation and tissue sterilization to alleviate the detrimental effects of ionizing radiation.

Selective fluoride sensing by a novel series of lanthanide-based one-dimensional coordination polymers through intramolecular proton transfer.

A novel series of one-dimensional coordination polymers (CPs) is achieved via a facile one-pot synthesis strategy employing the nitrate salts of trivalent lanthanides, a pentadentate chelating ligand, and triphenylphosphine oxide at a controlled stoichiometry under ambient conditions. All the CPs are characterized comprehensively using spectroscopic, X-ray crystallographic and magnetometric studies. The CPs are found to be thermally stable up to a significantly high temperature and resistant to water for an indefinite time. They are photoactive and exhibit selective fluoride ion (F-) sensing with excellent efficiency both colorimetrically and fluorimetrically in the solid-state as well as in solution. The presence of F- concomitantly sensitizes the photoluminescence enhancement and visual decolourization of the CPs in solution owing to the ground-state intra-molecular proton transfer. The photophysical response of the CPs to F- in solution was found to be instantaneous (<30 s). The sensitivity of detection is observed to be significantly high over a wide range of F- concentrations, covering the beneficial and detrimental domains of F- concentrations in drinking water. The limit of detection (LoD) under ambient conditions was found to be in the micromolar (μM) range-the best being 0.22 μM found using UV-vis spectrometry and 7.5 μM using fluorimetry. In comparison, the USEPA standard cut-off for the upper limit of F- concentration in drinking water is 211 μM, and the LoD of measuring F- concentration using the USEPA standard method using a fluoride-selective electrode is 26.3 μM. The CPs display markedly high selectivity toward F- with negligible-to-no interference from the commonly abundant ions (Cl-, Br-, I-, CH3CO2-, CO32-, SO42-, HPO42-, NH4+, Na+, K+, Mg2+, and Ca2+) in terms of UV-vis spectral change. Moreover, they also exhibit solid-state IR-spectrometric sensitivity towards F- under ambient conditions.

Rational design and construction of S-scheme CeO2/AgCl heterojunction with enhanced photocatalytic performance for tetracycline degradation

Semiconductor-based photocatalysis has attracted extensive attentions in waste water treatment and environment remediation. However, a single semiconductor photocatalyst inevitably encounters a dilemma between light absorption and redox ability of photoinduced holes and electrons. In this work, an S-scheme CeO2/AgCl heterojunction photocatalyst was designed, prepared and characterized by various techniques. The as-prepared CeO2/AgCl composite photocatalyst exhibited enhanced photocatalytic activity compared with single CeO2 and AgCl as revealed by the photodegradation of tetracycline (TC), a widely used antibiotic. According to UV–Vis spectral changes and degradation mass spectra of TC, the CeO2/AgCl composite photocatalyst not only can destroy the B, C, D rings, but also the A ring of TC, which cannot be destroyed by most of previously reported photocatalysts. The enhanced photocatalytic ability of CeO2/AgCl composite was due to the formation of an S-scheme heterojunction structure between CeO2 and AgCl, which simultaneously retained the maximum redox ability of photoinduced holes and electrons in the valence band of AgCl and in the conduction band of CeO2, respectively, resulting in the production of highly efficient O2−, OH and h+. This work provided insight into the rational design and construction of S-scheme heterojunction composites and new possibility of photocatalytic degradation of antibiotic wastewater.

Imidazobenzimidazole fused aza-calix[4]arenes: Synthesis, structure, and Zn2+-selective colorimetric-fluorometric sensor

Tetra(amino)azacalix[4]arene skeleton was functionalized at the bridging NH sites using various aromatic aldehydes via formation of imidazobenzimidazole fused heterocycles. X-ray single crystal analysis revealed distorted 1,3-alternate conformations for the resulting macrocycles. Anthracenyl and pyrenyl modified imidazobenzimidazole fused aza-calix[4]arenes existed as dimers in the solid state, associated mainly through π-π stacking interactions between the planar polycyclic fluorophores. The tetrapyrenyl modified product was further used as a Zn2+-selective sensor, which showed naked-eye detected color change and enhanced excimer emission. The stoichiometry between the sensor and Zn2+ was determined to be 1:1 and the association constant was 1.1 × 105 L/mol. The sensing process was highly selective and showed strong anti-interference with presence of other cations. The UV-vis spectral changes in the sensing process were completely reversible by alternate addition of Zn2+ and F−, showing an efficient ‘‘on–off-on’’ result.

Combined calorimetric, spectroscopic and microscopic investigation on the inclusion complex from cyclocurcumin and sulfobutylether-β-cyclodextrin in aqueous solution and Kinetics of thermal cis-trans isomerization

The complexation reaction between cyclocurcumin (CyCur), a natural curcuminoid with bioactive effects, and sulfobutylether-β-cyclodextrin (SBE-βCD), one of the more versatile and tolerate β-cyclodextrin derivates, was investigated in aqueous solution at 298 K. The UV–vis spectral changes of CyCur in the presence of SBE-βCD indicate the formation of the host-guest inclusion complex according to a 1:1 stoichiometry. The binding constant (Kb) determined by applying the Benesi-Hildebrand model was comparable to the value obtained by Isothermal Titration Calorimetry (ITC) measurements. Moreover, the thermodynamic parameters of the SBE-βCD/CyCur interactions demonstrate that the complexation process is enthalpically driven. Interestingly, microscopy analysis highlights the tendency of cyclocurcumin to aggregate into spherical fluorescent structures able to change their aspect and morphology in the presence of SBE-βCD. Finally, the thermal cis-trans isomerization rates of CyCur in the temperature range 294–314 K and the energetic parameters calculated by Arrhenius and Eyring plots were spectroscopically determined in SBE-βCD aqueous solution.

Colorimetric detection of phosphate-based on iron complexing catechol-displacement assay in eutrophicated water bodies

A simple, sensitive, and inexpensive colorimetric indicator-displacement assay based on Fe3+-catechol complex has been developed to determine PO43-. The Fe3+ and catechol formed a greenish color complex, upon the addition of PO43- to the complex, it exhibited a visual color change immediately from greenish to colorless along with UV–vis spectral change. This change was mainly attributed to the high binding affinity of PO43- with Fe3+ by displacing catechol from the Fe3+-catechol complex. The developed sensor showed good sensitivity for the determination of PO43- in a wide linear range from 2 − 1000 µM with a limit of detection (LOD) of 0.5 µM which was found to be lower than the permissible limit. The sensor presented good selectivity towards the detection of PO43- in the existence of other potential interfering anions. Furthermore, the method was successfully applied to determine PO43- in eutrophicated water bodies (river and lake water) with good recoveries and without showing any significant matrix effect.

Photochemical Nitric Oxide Release from S‐Nitrosothiol‐Functionalized Chitosan

AbstractS‐nitrosothiols (RSNOs) are nitric oxide (NO) donor molecules with potential biomedical applications since they mimic NO biological functions, such as vasodilation and inflammatory process regulation. In this work, chitosan (CS), a natural biopolymer widely used as a biomaterial, is functionalized with thioglycolic acid (TGA) or mercaptosuccinic acid (MSA) in reactions mediated by a carbodiimide, yielding CS with thiol contents of 88 µmol g–1 (CS‐TGA) and 126 µmol g–1 (CS‐MSA). The subsequent S‐nitrosation of CS‐TGA and CS‐MSA generates the corresponding S‐nitroso derivatives, CS‐TGA(SNO) and CS‐MSA(SNO). The UV–Vis spectral changes associated with the S‐NO bond cleavage of CS‐TGA(SNO) and CS‐MSA(SNO), monitored in solution over 18 days of storage in a common refrigerator, reveal that these S‐nitroso CS derivatives display enhanced thermal stability in the dark, with half‐life values of 36.1 for CS‐TGA(SNO) and 16.1 days for CS‐MSA(SNO). Conversely, CS‐TGA(SNO) and CS‐MSA(SNO) can release NO photochemically on‐demand under visible light irradiation in a first‐order process triggered by photon absorption that leads to a half‐life of 33 min for both S‐nitroso CS. These results show that CS‐TGA(SNO) and CS‐MSA(SNO) may emerge as new CS‐based biomaterials for providing light‐triggered local NO release in biomedical applications.

Iron Porphyrin as a Cytochrome P450 Model for the Degradation of Dye.

Organic dyes are widely used in the textile, biological, medical and other fields. However, a serious environmental problem has appeared because of the presence of organic dyes in industrial aqueous effluents. Thus, the efficient treatment of organic dyes in industrial wastewaters is currently in real demand. The current study investigated the oxidative degradation of the organic dye gentian violet by meso-tetra(carboxyphenyl) porphyriniron(III), [FeIII(TCPP)] as a cytochrome P450 model and iodosylbenzene (PhIO) as an oxidant at room temperature. The degradation reaction was monitored by UV-vis absorption spectroscopy via the observation of UV-vis spectral changes of the gentian violet. The results showed that the efficiency of catalyzed degradation reached more than 90% in 1 h, indicating the remarkable oxidative degradation capacity of the [FeIII(TCPP)]/PhIO system, which provided an efficient approach for the treatment of dyeing wastewater.

Multispectroscopic and computational evaluation of the binding of flavonoids with bovine serum albumin in the presence of Cu2+

Bovine serum albumin (BSA) has the potential application of establishing a delivery system for flavonoids. However, the effect of copper on the binding of flavonoids with BSA is unclear. Therefore, the binding of six flavonoids with BSA containing Cu2+ was investigated using UV–vis, fluorescence, and molecular docking. The UV–vis spectral changes demonstrated the formation of flavonoid-Cu2+ complexes. The fluorescence quenching results suggested that the chelation of Cu2+ increased the binding affinity of galangin and baicalin to the BSA but decreased the binding capacity of chrysin, baicalein, luteolin, and vitexin. Synchronous fluorescence data revealed that Cu2+ could influence the secondary structure conformation of BSA binding with flavonoids, which was further confirmed by ANS-binding fluorescence, circular dichroism, and molecular docking. These findings demonstrate that the complexation of Cu2+ significantly affects the binding of flavonoids with BSA, which provides the theoretical basis for the development of natural product-metal complex functional foods.

DEGRADATION OF METHYL BLUE BY FENTON PROCESS

In this study, the oxidative degradation of Methyl Blue (MB) triphenylmethane dye, in aqueous solution by Fenton oxidation process was investigated. The UV-Vis spectral changes of Methyl Blue dye during discoloration process were studied. Kinetic study was done to find out the effect of pH on discoloration rate of dye solution.

DEGRADATION OF METHYL BLUE BY FENTON PROCESS

In this study, the oxidative degradation of Methyl Blue (MB) triphenylmethane dye, in aqueous solution by Fenton oxidation process was investigated. The UV-Vis spectral changes of Methyl Blue dye during discoloration process were studied. Kinetic study was done to find out the effect of pH on discoloration rate of dye solution.

Development and Characterization of Silver Containing Free Standing Polymer FILMS for Dosimetry Applications.

Polymer gels and films, due to their near equivalence to biological tissue, are amongst the most promising future dosimetry tools for medical applications. The application of polymer dose gels is limited by the sensitivity of dose readout methods and dose gel properties. It is a challenge to find suitable dosimeters for registration of doses delivered to the target by orthovoltage therapy units. The application of metal-particle-enriched polymer composites for dose registration in X-ray therapy might be an elegant solution, especially if recent dose-reading technologies exploring advantages of different physical phenomena are involved. In this work, X-rays from the orthovoltage therapy range were used for the irradiation of experimental samples. In addition, radiation-induced processes of formation of silver nanoparticles in AgNO3–PVA gels and in free standing AgNO3PVA films, also containing some additional solvents, namely glycerol, ethanol, and isopropanol, have been investigated, with the aim to apply the developed composites for medical dosimetry purposes. A simple and environmentally friendly method for the formation of free-standing AgPVA films at room temperature was proposed and realized for preparing AgPVA films for investigation. Radiation-induced synthesis of silver nanoparticles in AgPVA composites was investigated, analyzing LPSR-based UV-VIS spectral changes to the irradiated films with respect to irradiation doses, and dose-related tendencies were also evaluated. It was shown that AgPVA films were more sensitive for detection of doses from the interval 0–1.0 Gy, thus indicating potential application of AgPVA films for dosimetry purposes.

Triazine and Porphyrin-Based Cross-Linked Conjugated Polymers: Protonation-Assisted Dissolution and Thermoelectric Properties

As two pivotal functional segments, triazine and porphyrin can be coupled to form a highly cross-linked conjugated polymer. Although the obtained conjugated polymers are almost insoluble in most so...

Synthesis, crystal structure, DFT calculation and trans → cis isomerisation studies of bipyridyl ruthenium(II) complexes bearing 8-oxyquinolate azo ligands

Two stable Ru(II) bipyridyl complexes were synthesized with the deprotonated forms of the azo ligands of 8-hydroxyquinoline (hq) as analogues and they were chromatographically separated. The extended azo ligands coordinated as a bidentate ligand and chelates to ruthenium(II) through 8-quinolinolate moiety, leaving the azo part free from coordination. The general formula of the complexes are [Ru(bpy)2(q)]+. Here, q− is the deprotonated form of 5-phenylazo-8-hydroxyquinoline (Hq1) and 5-(2-naphthylazo)-8-hydroxyquinoline (Hq2). The complexes were verified by 1H NMR, ESI-mass, absorption-emission spectra, cyclic voltammetry and single-crystal X-ray structure determination. UV light-induced trans → cis isomerization and reverse isomerism i.e. cis → trans around -N=N- bond at room temperature were proposed from the UV-Vis spectral changes as well as the changing of the colour of the solution of the complexes. In aid of understanding the electronic charge distribution and charge-transfer properties, computational studies employing DFT and TDDFT method have been executed. Significant alteration in absorption spectra and colour change was observed for trans-cis photo-isomerization of the complexes upon UV light irradiation due to presence of free rotating azo groups

Colorimetric determination of tyrosinase based on in situ silver metallization catalyzed by gold nanoparticles.

Gold nanoparticles (AuNPs) catalyze the mild reaction between the weak reducing agent kojic acid (KA) and silver ions (Ag+) to form Au@Ag bimetallic NPs by the combination of the intrinsic catalysis with plasmonic properties Thisis proposed as a novel optical assay to determine the tyrosinase (TYRase) concentration. The nanoparticles have been characterized by UV-vis spectroscopy, transmission electron microscope (TEM) images, and X-ray photoelectron spectroscopy (XPS). The sensing mechanism is based on the fact that KA binds to TYRase by chelating with dicopper active site of TYRase and the introduction of TYRase restrains the Au@Ag bimetallic NP formation by the precedent binding with KA. A clear color variation from yellow to pink and UV-vis spectral changes are observed at the optimal wavelength of 410nm. The assay works in the range 0.13~0.73UmL-1 with a detection limit (LOD) of 0.019UmL-1. The impact from matrix interfering substances including glucose, uric acid, common oxidases, and amino acids isnegligible. The applicability is demonstrated by quantitative determination of TYRase in human serum samples with 74 to 89% recoveryand RSD less than 4.0%, which accords with the level for bio-sample analysis. Graphical abstract Schematic presentation of colorimetric assay for tyrosinase (TYRase) based on the inhibition effect on silver deposition onto catalytically active gold nanoparticles (AuNPs) and its application with a smartphone. Tyrosinase (TYRase); silver ions (Ag+); kojic acid (KA); gold nanoparticles (AuNPs); gold-silver core-shell nanoparticles (Au@Ag NPs).

Dioxygen Activation by Internally Aromatic Metallacycle: Crystallographic Structure and Mechanistic Investigations.

SummaryMononuclear metal-peroxo species are invoked as the key intermediates in metalloenzymatic or synthetic catalysis. However, either transience or sluggishness reactivity of synthetic analogs of metal-peroxo species impedes our understanding of oxygen activation mechanism. Herein, we designed and characterized a dioxygen-derived mononuclear osmium-peroxo complex, in which the peroxo ligand is stabilized by internally aromatic metallacycle. We demonstrate that the osmium-peroxo species shows catalytic activity toward promoterless alcohol dehydrogenations. Furthermore, computational studies provide a new mechanism for the osmium-peroxo-mediated alcohol oxidation, starting with the concerted double-hydrogen transfer and followed by the generation of osmium-oxo species. Interestingly, the internally aromatic metallacycle also plays a vital role in catalysis, which mediates the hydrogen transfer from osmium center to the distal oxygen atom of Os–OOH moiety, thus facilitating the Os–OOH→Os=O conversion. We expect that these insights will advance the development of aromatic metallacycle toward aerobic oxidation catalysis.

Tuning of renewable biomass lignin into high value-added product: Development of light resistant azo-lignin colorant for coating application

The valorization of lignin by virtue of functionalization of its aromatic backbone with different moieties through diazo coupling reaction and its utilization as a leather chemical has been attempted. The 4-aminoazobenzene functionalized lignin based azo polymer (4-AAB-IL) was characterized using Nuclear Magnetic Resonance Spectroscopy (NMR), Heteronuclear Single Quantum Correlation (HSQC), Fourier - Transform Infrared Spectroscopy (FT-IR), UV–visible absorption, and dynamic light scattering techniques. The CHNS analysis reveals the increase in the percentage of nitrogen after diazotization which could have originated from the diazo functional groups. UV–visible absorption spectra of azo-modified lignin exhibit the characteristic features of azobenzene. The photoisomerization of lignin bearing azobenzene from trans→cis isomer was understood from the characteristic UV–visible spectral changes monitored during the course of the reaction. Notably the photostationary state (PSS), an indicator for the extent of trans isomer converted into cis isomer, PSStrans/cis is found to be 92:8 for 4-AAB-IL whereas that of the parent compound 4-aminoazobenzene (4-AAB) is 32:68. This indicates the higher photostability of 4-AAB-IL which would have originated from the restrictions in the structural motions around the diazo moiety imposed by the lignin skeleton, which is essential for the isomerization reaction. Since the azo compounds are evolved as dyes in leather industries, the applicability of synthesized 4-AAB-IL on leather was tested and the results showed excellent light fastening properties even after prolonged irradiation. In addition, the 4-AAB-IL provides darker shade to the crust leather when compared to the 4-AAB, thus these results suggest that functionalization of lignin could pave the way to alter the color of the lignin in a desired way by employing suitable substituents. This functional lignin based colorant would find a new green and sustainable pathway for cleaner application of lignin in coating.

Caution for the routine use of phenol red – It is more than just a pH indicator

Phenol red (PR) is the standard pH indicator in various cell and tissue culture media, as it provides a quick check for the health of the culture. PR has also been used in multiple protocols to detect cellular hydrogen peroxide as well as peroxidase activity from human peroxidase enzymes. The majority of promyelocytic leukemia cell lines (e.g. HL-60 cells) express myeloperoxidase (MPO), which may react with PR, especially as the latter is present in cell culture media at sufficient concentrations (~15 μM) to partake in redox reactions. Moreover, phenolic molecules are often efficient donor substrates for peroxidase enzymes. In this study, we hypothesized that MPO metabolism of PR via MPO-expressing HL-60 cells could result in PR metabolite(s) that could modulate cell viability. We used purified human MPO for UV–visible spectrophotometry, electron paramagnetic resonance (EPR) and LC-MS analyses to investigate PR peroxidation. 2-chloro-5,5-dimethyl-1,3-cyclohexanedione (monochloro-dimedone, MCD) was used to assess the effect of PR on MPO-catalyzed chlorination activity, and we assessed PR uptake by HL-60 cells using LC-MS analysis. Lastly, we investigated the impact of PR metabolism by intracellular MPO on cell viability (ATP, using CellTiter-Glo®), cytotoxicity (using trypan blue), and on reduced and oxidized glutathione (using GSH/GSSG-Glo™). Our results demonstrate that PR undergoes oxidative halogenation via MPO, resulting in its UV–vis spectral changes due to the formation of mono- and di-halogenated products. Moreover, a significant increase in MPO-catalyzed chlorination of MCD and an increase in glutathionyl radical detection (using EPR) were observed in the presence of PR. Our in-vitro studies revealed that PR is readily taken up by HL-60 cells and its metabolism by intracellular MPO leads to a significant decrease in cellular glutathione as well as a significant increase in glutathione disulphide formation. In spite of the latter, PR had no considerable effect on HL-60 cell viability. These results provide evidence that while no overt decrease in cell viability may be observed, PR does impart redox activity, which investigators should be wary of in experimental protocols.

Synthesis of novel betaine dyes for multi chromic sensors

In this study, we have designed and synthesized novel betaine dyes with clear structural confirmation using 1H and 13C NMR spectroscopy, ESI-MS and UV–Vis analyses. For these betaines, we investigated their hydro-, iono-, thermo- and solvato-chromic sensor properties through UV–visible spectral changes and visual color changes. We observed hydrochromic properties in solution state by adding 3% water (V/V) and we checked solid state hydrochromic sensing property through betaine-embedded PEO film. For ionochromism, we used an equimolar concentration of salt to dye in solution. Thermochromic sensing studies were performed in a temperature range from 50 °C to −10 °C, and solvatochromism properties were investigated by increasing polarity using solvents from DCM to DMF. Finally, the experimental results were supported with theoretical studies.