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Carbon nanodots (CD) can be prepared from simple organic precursors and renewable natural products through user-friendly processes. Functional groups, structure, and morphology of CD determine their fundamental properties. The understanding of the correlation of the latter properties with the nature of precursor materials and synthesis methods is still under debate. In this context, the present work explores a tunable CD synthesis method based on microwave-assisted hydrothermal carbonization of urea/glucose mixtures, allowing variations in CD N-content. Different reaction conditions were tested and products were widely characterized. In the absence of urea, oxidized graphitic carbon dots of ca. 3 nm and low photoluminescence quantum yields (ΦPL∼0.009) were obtained. On increasing the urea molar fraction (χu), N-rich carbon dots were synthesized, characterized by the presence of amide surface groups and enhanced photoluminescence yields (ΦPL∼0.02 for χu∼0.2). In the extreme cases of χu ≥ 0.9, partially oxidized graphitic carbon nitride nanoflakes were obtained with ΦPL∼0.10. Correlations between N:C precursors ratio and synthesis conditions with the structure and photophysical properties of the nanoparticles obtained is thoroughly analyzed and discussed. In summary, a tunable synthesis method for preparing different carbon nanomaterials from the same very abundant and cheap precursors, glucose and urea was developed.

Melanosomes have been considered crucial targets in melanoma treatments. In this study we explored the role of melanosomes in photodynamic therapy (PDT), employing the synthetic Zn(II) phthalocyanine Pc13, a potent photosensitizer that promotes melanoma cell death after irradiation. Phototoxic action is mediated by reactive oxygen species increase. The internalization mechanism of Pc13 and its consequent subcellular localization were evaluated in melanotic B16-F0 cells. Pharmacological inhibitors of dynamin or caveolae, but not of clathrin, decreased Pc13 cellular uptake and phototoxicity. Similar results were obtained when cells over-expressed dominant negative mutants of dynamin-2 and caveolin-1, indicating that Pc13 is internalized by caveolae-mediated endocytosis. Confocal microscopy analysis revealed that Pc13 targets melanosomes and damage of these structures after irradiation was demonstrated by transmission electron microscopy. Treatment of pigmented B16-F0 and WM35 melanoma cells with the melanin synthesis inhibitor phenylthiourea for 48 h led to cell depigmentation and enhanced cell death after irradiation, whereas a 3-h period of inhibition did not modify melanin content but produced a marked reduction of Pc13 phototoxicity, together with a decrease of oxidative melanin synthesis intermediates. In contrast, the effect of Pc13 in amelanotic A375 cells was not altered by phenylthiourea treatment. These results provide evidence that melanosomes have a dual role in the efficacy of PDT. While melanin antagonizes the phototoxic action of Pc13, the release of cytotoxic synthetic intermediates to cytosol after irradiation and melanosome damage is conducive to the phototoxic response. Based on these findings, we demonstrate that melanosome-targeted PDT could be an effective approach for melanoma treatment.

Natural and synthetic phenazines are widely used in biomedical sciences. In dehydrogenase histochemistry, phenazine methosulfate (PMS) is applied as a redox reagent for coupling reduced coenzymes to the reduction of tetrazolium salts into colored formazans. PMS is also currently used for cytotoxicity and viability assays of cell cultures using sulfonated tetrazoliums. Under UV (340 nm) excitation, aqueous solutions of the cationic PMS show green fluorescence ({\lambda}em: 526 nm), whereas the reduced hydrophobic derivative (methyl-phenazine, MPH) shows blue fluorescence ({\lambda}em: 465 nm). Under UV (365 nm) excitation, cultured cells (LM2, IGROV-1, BGC-1, and 3T3-L1 adipocytes) treated with PMS (5 ug/mL, 30 min) showed cytoplasmic granules with bright blue fluorescence, which correspond to lipid droplets labeled by the lipophilic methyl-phenazine. After formaldehyde fixation blue-fluorescing droplets could be stained with oil red O. Interestingly, PMS-treated 3T3-L1 adipocytes observed under UV excitation 24 h after labeling showed large lipid droplets with a weak green emission within a diffuse pale blue-fluorescing cytoplasm, whereas a strong green emission was observed in small lipid droplets. This fluorescence change from blue to green indicates that reoxidation of methyl-phenazine to PMS can occur. Regarding cell uptake and labeling mechanisms, QSAR models predict that the hydrophilic PMS is not significantly membrane-permeant, so most PMS reduction is expected to be extracellular and associated with a plasma membrane NAD(P)H reductase. Once formed, the lipophilic and blue-fluorescing methyl-phenazine enters live cells and mainly accumulates in lipid droplets. Overall, the results reported here indicate that PMS is an excellent fluorescent probe to investigate labeling and redox dynamics of lipid droplets in cultured cells., Comment: 23 pages, 7 figures, 1 table, publication year 2020

The synthesis and photochemical properties of two novel selenium zinc(II) phthalocyanines, a lipid-soluble 2,9(10),16(17),23(24)-tetrakis [(2-dimethylamino)ethylselanyl]phthalocyaninato zinc(II) (4) and its water-soluble quaternized derivative 2,9(10),16(17),23(24)-tetrakis [(2- trimethylammonium)ethylselanyl]phthalocyaninato zinc(II) tetraiodide (5), were investigated. Maximum absorption values were 689 nm and 684 nm for 4 and 5 in DMF, respectively. In addition, phthalocyanines were revealed to be very efficient singlet oxygen generators with high values of ΦΔ 0.74 and 0.84 for 4 and 5 in DMF, and they were photostable over the irradiation times studied. The photodynamic effect were evaluated on CT26 colon carcinoma cells. After light exposure, 4 and 5 were found to be cytotoxic, and IC50 values were 0.5 ± 0.1 μM and 2.3 ± 0.6 μM, respectively. The production of a greater amount of reactive oxygen species after phthalocyanines irradiation would be responsible for its potent phototoxic action on CT26 colon carcinoma cells. Fil: Ezquerra Riega, Sergio Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: Chiarante, Nicolás Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Valli, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Marino, Veronica Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Roguin, Leonor Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Awruch, Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: Garcia Vior, María Cecilia. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Quinoline is one of the most important heterocyclic systems in life sciences. Some derivatives are normal metabolites, and others are used as antibacterial, antimalarial, and anticancer agents. In this work, we describe the synthesis, physicochemical properties, and fluorescence features of a new 4-quinolinone fluorophore, 3-hydroxykynurenic acid (3-HOKA). 3-HOKA was obtained by alkoxide-induced rearrangement of ethyl isatinacetate followed by acidification and then alkaline hydrolysis. The fluorescent compound was characterized by NMR, MS, IR, and UV–Vis spectra. 3-HOKA can exist under a keto-enol equilibrium, but the 4-quinolinone form is the predominant tautomer. In PBS (pH = 7.4), the anionic keto form of 3-HOKA showed a maximum absorption at 368 nm, a fluorescence peak at 474 nm, and a fluorescence quantum yield (ΦF): 0.73. 3-HOKA is photostable and is a moderately weak oxygen generator. Viability assays on HeLa cells indicated that 3-HOKA did not induce significative cytotoxic effects. Under UV excitation, a bright blue fluorescence was selectively found in a singular body within the cytoplasm, a labeling pattern that suggests the possible localization of the probe in the centriole or related structures. Therefore, this novel fluorophore represents a promising prototype compound owing to its biocompatibility and potential biological applications. Fil: Shmidt, María Sol. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina Fil: Garcia Vior, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: Ezquerra Riega, Sergio Dario. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina Fil: Lazaro Martinez, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: Abasolo, María I.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: Lazaro Carrillo, Ana. Universidad Autónoma de Madrid; España Fil: Tabero, Andrea. Universidad Autónoma de Madrid; España Fil: Villanueva, Angeles. Universidad Autónoma de Madrid; España. Instituto Madrileño de Estudios Avanzados en Nanociencia; España Fil: Moglioni, Albertina Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: del Blanco, María Mercedes. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina Fil: Stockert Cossu, Juan Carlos. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Instituto de Investigacion y Tecnología en Reproducción Animal; Argentina

The effect of dye concentration on the fluorescence, ΦF, and singlet molecular oxygen, ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nmthick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF=0.05±0.01 andΦΔ=0.76±0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05Mand concentration self-quenching after 0.01Mare interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius rQ=1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF, trap/ΦF, monomer≈0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided. Fil: Ezquerra Riega, Sergio Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Rodriguez, Hernan Bernardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: San Roman, Enrique Arnoldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina

Identification and quantification of the separate roles of compression and of cake build-up in membranes under different fouling conditions can provide a better understanding of filtration and MBR behavior. A simple and rapid flux-step method for evaluation of critical flux, subcritical and supracritical fouling rates and in situ determination of internal and external irreversible fouling resistance and compressibility, without provoking alteration of the system and without stopping the treatment process is proposed. The main novelty of the modified method is the inclusion of a new stage, termed pre-compression, by means of a flux increase at the beginning of each filtration step. The incorporation of pre-compression phases suppresses the time dependent compression of the irreversible fouling that interferes with the accurate determination of fouling rate, even in highly compressible fouled membranes. Hysteresis tests confirmed that extra fouling due to the pre-compression stages is reversible. The compressibility index of external irreversible fouling rose as high as 0.59, pore blocking compressibility was significantly small and reversible fouling compression effect was not observed in short-term test. A novel method was employed to determine the scouring effect and to measure the efficiency of in situ chemical cleaning methods applied to an AnMBR.

The preparation and characterization of a tetrasubstituted alkylselenium zinc(II) phthalocyanine are reported herein for the first time. The precursor 4-(butylselanyl)phthalonitrile ( 4 ) was obtained in 65% yield. Tetrasubstituted alkylselenium zinc(II) phthalocyanine 5 was synthesized from 4 and zinc acetate in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene in butanol.