Synthesis, physicochemical and photophysical characterization of 4-(1-Pyrenyl)-Butyl-α-d-mannopyranoside

Indexación: Web of Science; Scopus; Scielo.Glycolipids are biomolecules composed of a lipid chain (lipophilic) and a monosaccharide or oligosaccharide as hydrophilic group. Their chemical structure and biological role make them undoubtedly good candidates for a large and continuously growing number of biotechnological applications. Mannose is a carbohydrate present on membrane glycolipids of a wide number of pathogenic microorganisms (bacteria, fungi, protozoa, and viruses) and specifically recognized by several lectins. We synthesized a mannose derivative linked through a short methylene chain to a pyrene moiety which behaves as a surfactant, able to aggregate, and retains the photophysical properties of pyrene: showing comparable absorption and emission spectra, having lower fluorescence quantum yield and the ability to form excimer, and finally the ability to produce O-2((1)Delta(g)) with high quantum yields. Thus, this novel molecule would open future applications for detection (fluorescence) or inactivation (singlet oxygen) of bacterial pathogens, viruses, tumor cells, or particular cells.http://ref.scielo.org/pcn4d

Laser-induced optoacoustics combined with near-infrared emission. An alternative approach for the determination of intersystem crossing quantum yields applied to porphycenes

An approach was developed to determine triplet quantum yields, ΦT, which overcomes most of the difficulties usually encountered in flash photolysis studies of triplet states. The combined application of near-IR emission and optoacoustics yields ΦT values which are independent of the absorption properties of the triplets. Thus, the triplet energies derived from near-IR phosphorescence spectra together with the values of the heat stored by the triplets determined from optoacoustic experiments afforded ΦT = 0.3 ± 0.1 for porphycene (PO) and 0.4 ± 0.1 for its tetra-n-propyl derivative (TPrPO). Several calorimetric references for optoacoustic measurements in the red region were tested. The ΦT values, combined with flash photolysis data, yielded accurate triplet- minus ground-state absorption coefficients. The quantum yields for singlet molecular oxygen production determined by time-resolved phosphorescence were ΦΔ = 0.34 ± 0.05 for PO and 0.36 ± 0.03 for TPrPO which implies an efficiency near unity for O2(1Δ8) production upon collision of the triplet states of the porphycenes with ground-state O2. © 1990 American Chemical Society.Fil:Aramendía, P.F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Negri, R.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Braslavsky, S.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

A Double Payload Complex between Hypericin and All-trans Retinoic Acid in the β-Lactoglobulin Protein

Combined therapies are usually used to treat acne vulgaris since this approach can tackle various foci simultaneously. Using a combination of spectroscopic, computational, and microbiological techniques and methods, herein we report on the use of β-lactoglobulin as a double payload carrier of hypericin (an antimicrobial photodynamic agent) and all-trans retinoic acid (an anti-inflammatory drug) for S. aureus in vitro photodynamic inactivation. The addition of all-trans retinoic acid to hypericinβ-lactoglobulin complex renders a photochemically safe vehicle due to the photophysical quenching of hypericin, which recovers its photodynamic activity when in contact with bacteria. The ability of hypericin to photoinactivate S. aureus was not affected by retinoic acid. β-Lactoglobulin is a novel biocompatible and photochemically safe nanovehicle with strong potential for the treatment of acne

Exploring structure–activity relationships in photodynamic therapy anticancer agents based on Ir(III)-COUPY conjugates

Photodynamic therapy holds great promise as a non-invasive anticancer tool against drug-resistant cancers. However, highly effective, non-toxic, and reliable photosensitizers with operability under hypoxic conditions remain to be developed. Herein, we took the advantageous properties of COUPY fluorophores and cyclometalated Ir(III) complexes to develop novel PDT agents based on Ir(III)-COUPY conjugates with the aim of exploring structure–activity relationships. The structural modifications carried out within the coumarin scaffold had a strong impact on the photophysical properties and cellular uptake of the conjugates. All Ir(III)-COUPY conjugates exhibited high phototoxicity under green light irradiation, which was attributed to the photogeneration of ROS, while remaining non-toxic in the dark. Among them, two hit conjugates showed excellent phototherapeutic indexes in cisplatin-resistant A2780cis cancer cells, both in normoxia and in hypoxia, suggesting that photoactive therapy approaches based on the conjugation of far-red/NIR-emitting COUPY dyes and transition metal complexes could effectively tackle in vitro acquired resistance to cisplatin

Assessing the potential of photosensitizing flavoproteins as tags for correlative microscopy

Photosensitizing flavoproteins have great potential as tags for correlative light and electron microscopy (CLEM). We examine the photostability of miniSOG mutants and their ability to photo-oxidize diaminobenzidine, both key aspects for CLEM. Our experiments reveal a complex relation between these parameters and the production of different reactive oxygen species. ¸ 2016 The Royal Society of Chemistry

Photoantimicrobials-are we afraid of the light?

Although conventional antimicrobial drugs have been viewed as miraculous cure-alls for the past 80 years, increasing antimicrobial drug resistance requires a major and rapid intervention. However, the development of novel but still conventional systemic antimicrobial agents, having only a single mode or site of action, will not alleviate the situation because it is probably only a matter of time until any such agents will also become ineffective. To continue to produce new agents based on this notion is unacceptable, and there is an increasing need for alternative approaches to the problem. By contrast, light-activated molecules called photoantimicrobials act locally via the in-situ production of highly reactive oxygen species, which simultaneously attack various biomolecular sites in the pathogenic target and therefore offer both multiple and variable sites of action. This non-specificity at the target circumvents conventional mechanisms of resistance and inhibits the development of resistance to the agents themselves. Photoantimicrobial therapy is safe and easy to implement and, unlike conventional agents, the activity spectrum of photoantimicrobials covers bacteria, fungi, viruses, and protozoa. However, clinical trials of these new, truly broad-spectrum, and minimally toxic agents have been few, and the funding for research and development is almost non-existent. Photoantimicrobials constitute one of the few ways forward through the morass of drug-resistant infectious disease and should be fully explored. In this Personal View, we raise awareness of the novel photoantimicrobial technologies that offer a viable alternative to conventional drugs in many relevant application fields, and could thus slow the pace of resistance development