Nanocomposite hydrogels have emerged to exhibit multipurpose properties, boosting especially the biomaterial field. However, the development and characterization of these materials can be a ...challenge, especially stimuli-sensitive materials with dynamic properties in response to external stimuli. By employing UV–vis spectroscopy and NMR relaxation techniques, we could outline the formation and behavior of thermosensitive nanocomposites obtained by in situ polymerization of poly(N-vinylcaprolactam) (PNVCL) and mesoporous silica nanofibers under temperature stimuli. For instance, inorganic nanoparticles covalently linked to PNVCL changed the pattern of temperature-induced phase transition despite showing similar critical temperatures to neat PNVCL. Thermodynamic parameters indicated the formation of an interconnected system of silica and polymer chains with reduced enthalpic contribution and mobility. The investigation of water molecule and polymer segment motions also revealed that the absorption and release of water happened in a wider temperature range for the nanocomposites, and the polymer segments respond in different ways during the phase transition in the presence of silica. This set of techniques was essential to reveal the polymer motions and structural features in nanocomposite hydrogels under temperature stimuli, demonstrating its potential use as experimental guideline to study multicomponent nanocomposites with diverse functionalities and dynamic properties.
Herein, we present a novel ruthenium(II)-perylene dyad (RuPDI-Py) that combines the photophysical properties of pyrrolidine-substituted perylene diimide (PDI-Py) and the ruthenium(II) polypyridine ...complex Ru(phen)32+. A comprehensive study of excited-state dynamics was carried out using time-resolved and steady-state methods in a dimethyl sulfoxide solution. The RuPDI-Py dyad demonstrated excitation wavelength-dependent photophysical behavior. Upon photoexcitation above 600 nm, the dyad exclusively exhibits the near-infrared (NIR) fluorescence of the 1PDI-Py state at 785 nm (τfl = 1.50 ns). In contrast, upon photoexcitation between 350 and 450 nm, the dyad also exhibits a photoinduced electron transfer from the {Ru(phen)32+} moiety to PDI-Py, generating the charge-separated intermediate state {Ru(III)-(PDI-Py)•–} (4 μs). This state subsequently decays to the long-lived triplet excited state 3PDI-Py (36 μs), which is able to sensitize singlet oxygen (1O2). Overall, tuning 1O2 photoactivation or NIR fluorescence makes RuPDI-Py a promising candidate for using absorbed light energy to perform the desired functions in theranostic applications.
Metabolomics analyses and improvement of growth conditions were applied toward diversification of phomactin terpenoids by the fungus Biatriospora sp. CBMAI 1333. Visualization of molecular networking ...results on Gephi assisted the observation of phomactin diversification and guided the isolation of new phomactin variants by applying a modified version of chemometrics based on a fractional factorial design. Consequentially, the first nitrogen-bearing phomactin, phomactinine (1), with a new rearranged carbon skeleton, was isolated and identified. The strategy combining metabolomics and chemometrics can be extended to include bioassay potency, structure novelty, and metabolic diversification connected or not to genomic analyses.
The complexes cis-Ru(phen)2(Apy)22+, Apy = 4-aminopyridine and 3,4-aminopyridine, are stable in aqueous solution with strong visible absorption. They present emission in the visible region with long ...lifetime that accumulates in the cytoplasm of Neuro2A cell line without appreciable cytotoxicity. The complexes also serve as mixed-type reversible inhibitors of human AChE and BuChE with high active site contact. cis-Ru(phen)2(3,4Apy)22+ competes efficiently with DMPO by the OH• radical. Luminescence using fluorescence lifetime imaging (FLIM) enables real-time imaging of the conformational changes of the self-aggregation of Aβ with incubation of complexes (0–24 h) in phosphate buffer at micromolar concentrations. By this technique, we identified protofibrills in the self-assembly of Aβ1–40 and globular structures in the short fragment Aβ15–21 in aqueous solution.
The water-soluble and visible luminescent complexes cis-Ru(L-L)2(L)22+ where L-L = 2,2-bipyridine and 1,10-phenanthroline and L= imidazole, 1-methylimidazole, and histamine have been synthesized and ...characterized by spectroscopic techniques. Spectroscopic (circular dichroism, saturation transfer difference NMR, and diffusion ordered spectroscopy NMR) and isothermal titration calorimetry studies indicate binding of cis-Ru(phen)2(ImH)22+ and human serum albumin occurs via noncovalent interactions with K b = 9.8 × 104 mol–1 L, ΔH = −11.5 ± 0.1 kcal mol–1, and TΔS = −4.46 ± 0.3 kcal mol–1. High uptake of the complex into HCT116 cells was detected by luminescent confocal microscopy. Cytotoxicity of cis-Ru(phen)2(ImH)22+ against proliferation of HCT116p53+/+ and HCT116p53–/– shows IC50 values of 0.1 and 0.7 μmol L–1. Flow cytometry and western blot indicate RuphenImH mediates cell cycle arrest in the G1 phase in both cells and is more prominent in p53+/+. The complex activates proapoptotic PARP in p53–/–, but not in p53+/+. A cytostatic mechanism based on quantification of the number of cells during the time period of incubation is suggested.
The Ru(II) (phen)2(pPDIp)2+ complex, where pPDIp is the symmetric bridging ligand phenanthroline–perylene–phenanthroline, shows strong electronic absorption bands attributed to the pPDIp and ...{Ru(phen)2}2+ moieties in acetonitrile. The charge-separated intermediate {Ru(III) (phen)2(pPDIp–•)} was detected by transient absorption spectroscopy upon electronic excitation in either the pPDIp or the complex moieties. The charge-separated intermediate species decays to generate the triplet state 3*pPDIp-Ru(II) (τP = 1.8 μs) that sensitizes the formation of singlet molecular oxygen with quantum yield ϕΔ = 0.57. The dyad in deaerated acetonitrile solutions is reduced by triethylamine (NEt3) to the Ru(II) (phen)2(pPDIp•–) radical anion in the dark. The electron-transfer reaction is accelerated by light absorption. By photolysis of the radical anion, a second electron transfer reaction occurs to generate the Ru(II) (phen)2(pPDIp2–) dianion. The changes of the color of solution indicate the redox states of complexes and offer a sensitive reporter of each stage of redox reaction from start to finish. The reduced complexes can be converted to the initial complex, using methyl viologen or molecular oxygen as an electron acceptor. The accumulation of electrons in two well-separated steps opens promising opportunities such as in catalysis.
The hormone estradiol 17β valerate (E2V), used in hormone replacement therapy, undergoes a structural phase transition at 251.1 K on cooling. The crystalline structures of the low and room ...temperature phases were determined showing that neither the space group nor the site symmetry and number of atoms are altered. These phases are related by a large conformational reorientation of the valerate chain. In addition, thermal analysis, solid state nuclear magnetic resonance, and infrared spectroscopy show that the transformation is reversible, discontinuous, and first order, evidencing the occurrence of an isosymmetric phase transition, rare for organic compounds.
Linear low-density polyethylene (LLDPE)/montmorillonite clay (MMT) nanocomposites were obtained by dilution of a master batch containing 20.0% clay content in a twin screw extruder to obtain samples ...with 1.5–10.0% clay content. Samples were aged in fuel (ethanol or gasoline) for 30 days at room temperature (25 °C). In the present study, wide-angle X-ray diffraction (WAXD) showed that ethanol interacts with clay more than gasoline does, rearranging the clay structure that was lost during the preparation of the nanocomposites. Solid-state 13C NMR spectroscopy showed that MMT modified the morphological structure of the LLDPE matrix, making it more heterogeneous. Moreover, the fuel-aging process generates structures that are more heterogeneous than nonaged nanocomposites. Finally, fuel sorption analysis was used to verify the structure of the LLDPE matrix after the addition MMT. It was observed that the gasoline diffusion coefficients were higher than the ethanol diffusion coefficients.
The beneficial effect of polyphenols and magnesium(II) against oxidative stress motivated our research group to explore the antioxidant activity of phenMgIso, an aqueous soluble magnesium(II) ...complex containing 1,10-phenanthroline (phen) and isovanillic acid (Iso) as ligands. Combined electrospray ionization–mass spectrometry and DOSY-NMR techniques identified two complexes in methanolic solution: hexacoordinated Mg(phen)2(Iso)+ and tetracoordinated Mg(phen)(Iso)+. The cyclic voltammogram of phenMgIso in the anodic region showed a cyclic process that interrupts the isovanillic acid degradation, probably by stabilization of the corresponding phenoxyl radical via complexation with Mg(II), which is interesting for antioxidant applications. phenMgIso competes with 2,2,6,6-tetramethylpiperidine by 1O2 with IC50(1O2) = 15 μg m–1 and with nitrotetrazolium blue chloride by superoxide ions (IC50(O2 •–) = 3.6 μg mL–1). Exposure of both zebrafish (2 mg L–1) and wistar male rats (3 mg kg–1 day–1 dose for 21 days) to phenMgIso does not cause mortality or visual changes compared with the respective control groups, thus phenMgIso could be considered safe under the conditions of this study. Moreover, no significant changes in comparison to both control groups were observed in the biochemical parameters on the brain-acetylcholinesterase activity, digestive tract enzyme catalase, and glutathione-S-transferase. Conversely, the performance of superoxide dismutase activity in wistar male rats increased in the presence of a complex, resulting in enhanced capacity of rats for superoxide radical enzymatic scavenging. The synergistic action of phenMgIso may be explained by the strong electrostatic interaction between Mg(II) and the O,O(phenolate) group, which makes the Iso ligand easier to oxidize and deprotonate, generating a cyclic stable species under oxidative conditions.
Salts of naproxen (NAP) with chitosan (CTS) and reticulated chitosan (CEP) were prepared under optimized conditions to maximize the yield of reaction. The objective was to evaluate the dissociation ...in water, which can guide studies of release of the drug from biopolymeric salts in pharmaceutical applications. Higher salification was found after 24 h of reaction at 60 °C in a molar ratio 1:1.05 (CTS:NAP, mol/mol), resulting in a degree of substitution (DS) of 17% according to 13C NMR, after neutralization of the –NH2 group of the biopolymer by the carboxylic group of the drug. The presence of NAP salt is evidenced by FTIR bands related to the –NH3+ group at 856 cm−1, a decrease in crystallinity index in XRD diffractograms as well as changes in mass loss ratios (TG/DTG/DTA) and increased thermal stability of the salt regarding CTS itself. The CEPN crosslinked salt presented a DS = 3.6%, probably due to the shielding of the –NH2 groups. Dissociation studies revealed that at pH 2.00, dissociation occurred faster when compared to at pH 7.00 in the non-reticulated salt, while the opposite was observed for the reticulated one.
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