Facile Obtainment of Fluorescent PEG Hydrogels Bearing Pyrene Groups by Frontal Polymerization

Frontal polymerization (FP) was used to prepare poly(ethylene glycol) methyl ether acrylate (PEGMA) fluorescent polymer hydrogels containing pyrenebutyl pendant groups as fluorescent probes. The polymerization procedure was carried out under solvent-free conditions, with different molar quantities of pyrenebutyl methyl ether methacrylate (PybuMA) and PEGMA, in the presence of tricaprylmethylammonium (Aliquat 336®) persulfate as a radical initiator. The obtained PEGPy hydrogels were characterized by FT-IR spectroscopy, confirming the effective incorporation of the PybuMA monomer into the polymer backbone. The thermal properties of the hydrogels were determined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). After immersing the hydrogels in deionized water at 25 °C and pH = 7, their swelling behavior was investigated by mass gain at different pH and temperature values. The introduction of PybuMA comonomer into the hydrogel resulted in a decreased swelling ability due to the hydrophobicity of PybuMA. The optical properties of PEGPy were determined by UV-visible absorption and fluorescence spectroscopies. Both monomer and excimer emission bands were observed at 379–397 and 486 nm, respectively, and the fluorescence spectra of the PEGPy hydrogel series were recorded in different solvents to explore the coexistence of monomer and excimer emissions.

Multi-walled Carbon Nanotubes Synthesis by Arc Discharge Method in a Glass Chamber

Abstract. In the present paper, carbon nanotubes (CNTs) were synthesized by arc discharge method by vaporizing graphite rods in the presence of Ni and a Ni/Y mixture as catalysts for subsequent use in electrical energy storage and conversion devices. CNTs synthesis was carried out in a cylindrical glass reactor applying a controlled Argon flow of 1.43 cm3/min and a chamber pressure of 39 kPa. Carbon powder was collected from the reactor following chemical treatment with HCl solution at 1 M to remove the metallic impurities. Morphology obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed multi-walled nanotubes (MWCNTs) with amorphous carbon particles attached to their surface. Fourier transform infrared (FT-IR) spectra presented bands at 1550 and 1200 cm–1 corresponding to the C=C bond characteristic to the CNTs skeleton; these bands were not present in pristine graphite. Electromagnetic absorbance was observed using ultraviolet-visible spectroscopy (UV-Vis) showing peaks at 204 and 256 nm related to sp2 hybridization characteristic for MWCNTs.   Resumen. En el presente trabajo se sintetizaron nanotubos de carbono (NTCs) por el método de descarga de arco mediante la vaporización de barras de grafito en presencia de Ni y una mezcla de Ni/Y como catalizadores para su posterior uso en dispositivos de almacenamiento y conversión de energía eléctrica. La síntesis de NTCs se realizó en un reactor cilíndrico de vidrio aplicando un flujo controlado de Argón de 1.43 cm3/min y una presión de cámara de 39 kPa. El polvo de carbón se recolectó del reactor y se trató químicamente con una solución de HCl a 1 M para eliminar las impurezas metálicas. La morfología obtenida por microscopía electrónica de barrido (MEB) y microscopía electrónica de transmisión (MET) mostró nanotubos de paredes múltiples (NTCPMs) con partículas de carbón amorfo adheridas a su superficie. Los espectros de infrarrojo transformada de Fourier (FT-IR) mostraron bandas en 1550 y 1200 cm–1 que corresponden al enlace C=C característico de los NTCs; estas bandas no estuvieron presentes en el grafito prístino. La absorbancia electromagnética se observó mediante espectroscopia ultravioleta-visible (UV-Vis) mostrando picos a 204 y 256 nm relacionadas con la hibridación sp2 característica de los NTCPMs.

Guest-Mediated Reversal of the Tumbling Process in Phosphorus-Dendritic Compounds Containing β-Cyclodextrin Units: An NMR Study

The conformational study of dendritic platforms containing multiple β-cyclodextrin (βCD) units in the periphery is relevant to determine the availability of βCD cavities for the formation of inclusion complexes in aqueous biological systems. In this work, we performed a detailed conformational analysis in D2O, via 1D and 2D NMR spectroscopy of a novel class of phosphorus dendritic compounds of the type P3N3-[O-C6H4-O-(CH2)n-βCD]6 (where n = 3 or 4). We unambiguously demonstrated that a functionalized glucopyranose unit of at least one βCD unit undergoes a 360° tumbling process, resulting in a deep inclusion of the spacer that binds the cyclodextrin to the phosphorus core inside the cavity, consequently limiting the availability of the inner cavities. In addition, we confirmed through NMR titrations that this tumbling phenomenon can be reversed for all βCD host units using a high-affinity guest, namely 1-adamantanecarboxylic acid (AdCOOH). Our findings have demonstrated that it is possible to create a wide variety of multi-functional dendritic platforms.

Efficient modification of PAMAM G1 dendrimer surface with β-cyclodextrin units by CuAAC: impact on the water solubility and cytotoxicity

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications. In this work, we completely modified the periphery of PAMAM dendrimer generation 1 (PAMAM G1) with β-cyclodextrin (β-CD) units through the Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) to obtain the PAMAM G1-β-CD dendrimer with high yield. The PAMAM G1-β-CD was characterized by ¹H- and ¹³C-NMR and mass spectrometry studies. Moreover, the PAMAM G1-β-CD dendrimer showed remarkably higher water solubility than native β-CD. Finally, we studied the toxicity of PAMAM G1-β-CD dendrimer in four different cell lines, human breast cancer cells (MCF-7 and MDA-MB-231), human cervical adenocarcinoma cancer cells (HeLa) and pig kidney epithelial cells (LLC-PK1). The PAMAM G1-β-CD dendrimer did not present any cytotoxicity in cell lines tested which shows the potentiality of this new class of dendrimers.

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications.

Encapsulation of Antihypertensive Peptides from Whey Proteins and Their Releasing in Gastrointestinal Conditions

Antihypertensive peptide fraction from whey protein hydrolysate <3 kDa (measured as angiotensin-converting enzyme (ACE) activity %) was isolated and encapsulated into three composite materials: alginate-collagen, alginate Arabic gum, and alginate-gelatin. The release behavior of peptide fraction from capsules was analyzed according to the encapsulation material efficiency, the characteristics of the capsules, and the released antihypertensive peptides during gastrointestinal digestion. The highest encapsulation efficiency was found in capsules of alginate Arabic gum (95%). In this case, the released peptides incremented their ACE activity (85%) after the digestion process, with respect to the initial ACE activity (74%). Whey antihypertensive fraction revealed five peptide sequences; however, other amino acid sequences were released from digested capsules. Protein databases confirmed some antihypertensive sequences indicating the peptides content from β-Lg and α-La. Consequently, new peptides could be revealed from whey antihypertensive fraction.

[Correlation of the transaortic gradient determined with doppler echocardiography versus catheterization in patients with aortic stenosis]

The purpose of this report is to evaluate the reliability of a non-invasive estimation of a transaortic gradient in patients with valvular aortic stenosis by doppler echocardiography. We compared the transvalvular gradients obtained by cardiac catheterization (invasive) versus the estimation by non-invasive technique such as continuous-wave doppler in 30 consecutive patients with valvular aortic stenosis. When compared the peak velocity (Vmax) of the aortic jet versus the gradient obtained by cardiac catheterization we found a correlation coefficient (r) of 0.83 and when compared the gradient obtained by both methods we found an r value of 0.85. These results show that the calculations of aortic gradient by echo-doppler, are reliable. Besides this method allowed us to establish the correct diagnosis and to follow up these patients.