Angel Leiva

Bio-foam enhances larval retention in a free-spawning marine tunicate

Here we report a mechanism that reduces dispersal of early developing stages and larvae in a free-spawning intertidal and shallow subtidal tunicate, Pyura praeputialis (Heller 1878), in the Bay of Antofagasta, Chile. The spawning of gametes by the tunicate into the naturally turbulent aerated seawater decreases their surface tension and induces the formation of a bio-foam. Water collected from foamy intertidal pools and tide channels showed a high concentration of P. praeputialis early developing stages and tadpole larvae in the foam. Because gametes are synchronically spawned for external fertilization and larvae settle near adults, our results suggest that this bio-foam increases fertilization success and effective settlement of their short-lived larvae in the vicinity of the adults spawning the gametes. This mechanism reinforces published evidence suggesting that local retention of intertidal and inshore marine invertebrate larvae may be more common than previously thought, offering, for instance, new perspectives for the design and networking of marine protected and management areas.

Synthesis of Oligomeric Silicon-containing Poly(imide-amide)s Derived from Trimellitic Anhydride and Amino-Acids. Vibration Spectral, Optical, Thermal and Morphological Characterization

Poly(imide-amide)s (PIAs) were synthesized from diacids, which were obtained by trimellitic anhydride and glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and p-aminobenzoic acid, and bis(4-aminophenyl)diphenylsilane. Compounds were characterized by elemental analysis, optical activity, IR and NMR spectroscopies. Yields were good, but ηinh values were low, showing materials of oligomeric nature, confirmed by MALDI-TOF spectrometry. PIAs were soluble in polar aprotic solvents, while those derived from amino acids with bulky side groups were soluble in CHCl3 and acetone. The wavenumber of vibrational bands were compared by Infrared and Raman spectroscopy. However, the high fluorescence emitted for PIAs, difficult to predict the vibrations of certain functional groups by Raman spectroscopy. The incorporation of chiral, amide and imide moieties interrupt the conjugation and increase the flexibility of the system. In addition, the adjacent phenyl units from the silicon-containing diamine, disfavors the planar conformation, which affects the optical properties showing an insulator behavior. DSC analyses showed that PIA-VII of aromatic nature had the higher glass transition temperature (Tg) value. For the other PIAs the Tg values decreased when volume of the side groups was increased, with the exception of PIA-VI derived from L-isoleucine. The thermal decomposition temperatures showed that only PIA-VII derived from p-aminobenzoic acid was thermostable. For the other PIAs it was possible to see a decrease of the TDT values when the size of the side chain is increased. The size and shape of the polymeric particles were studied by Scanning Electronic Microscopy (SEM), showing a relation between structure, incorporation of rigid aromatic rings and voluminous group into the system.

Encapsulation of Antioxidant Gallate Derivatives in Biocompatible Poly(ε-caprolactone)-b-Pluronic-b-Poly(ε-caprolactone) Micelles.

Formulation of antioxidant agents is still a challenge that limits their application in the biomedical field. Pentablock copolymers obtained through modification of two common PEO-PPO-PEO copolymers (Pluronic F127 and F68) with poly(ε-carprolactone) (PCL) were evaluated regarding their capability to form nanocarriers suitable for gallic acid, methyl gallate, and ethyl gallate. Applying a dialysis method, PCL/F127/PCL and PCL/F68/PCL self-assembled into spherical micelles in 0.9% NaCl aqueous solution but notably differed in critical micellar concentration (CMC), micelle core hydrophobicity, and micelle size, as evidenced by pyrene fluorescence, transmission electron microscopy, and dynamic light scattering. Cytotoxicity studies showed that the copolymers were safe at concentrations well above the CMC. Transfer of gallic acid and derivatives from aqueous medium to the micelle phase was characterized in terms of distribution constant and free energy of transference, which were shown to be strongly dependent on the hydrophobicity of the gallate derivatives and the length of PCL in the pentablock copolymer. Antioxidant activity of gallates was challenged against DPPH previously loaded in PCL/F127/PCL and PCL/F68/PCL micelles. The more the hydrophobicity of the gallate derivative, the greater the capability to enter in the micelle and to consume free radicals. In vitro release studies of gallic acid, methyl gallate, and ethyl gallate from the pentablock copolymer micelles also evidenced the influence of the hydrophobicity of both the gallate derivative and the micelle core on release rate, recording a variety of release patterns. Overall, PCL/F127/PCL and PCL/F68/PCL appear as suitable nanocarriers of potent antioxidant agents in a wide range of polarities, which may be useful for diverse therapeutic applications.

The effect of vacuum frying on starch gelatinization and its in vitro digestibility in starch–gluten matrices

Starch digestibility in a food matrix depends on processing conditions that may affect its physical state and microstructure. Starch gelatinization is one critical change that takes place during frying which could be affected during low-pressure processing. This study assessed the effect of vacuum frying on starch gelatinization and its in vitro digestibility. Laminated dough was made of a reconstituted blend of wheat starch (88% d.b.) and gluten (12% d.b.). Samples were fried under vacuum (6.5 kPa, Twater-boiling-point=38°C) or atmospheric conditions up to bubble-end point, maintaining a thermal driving force of 70°C (Toil-Twater-boiling-point=70°C). Vacuum fried samples showed less starch gelatinization (28%), less rapidly available glucose (27%), and more unavailable glucose (70%) than their atmospheric counterparts (which presented 99% starch gelatinization, 40% rapidly available glucose, and 46% unavailable glucose), and the values were close to those of raw dough. These results show how vacuum processing may be used to control the degree of starch gelatinization and related digestibility.

Thermal and morphological behavior of chitosan/PEO blends containing gold nanoparticles. Experimental and theoretical studies.

Using solution-casting method, binary blends of chitosan (CS) and poly (ethylene oxide) (PEO 100,000) containing Au nanoparticles (AuNPs) were prepared. Shifts in the melting temperature (Tm) and crystallization temperature (Tc) values for CS/PEO and CS/PEO/AuNPs blends were observed by calorimetric analysis. In general, CS/PEO/AuNPs blends tended to decompose at higher temperatures than neat polymers. From the FT-IR spectra, shifts in the main signals, such as -NH2, -OH and COC, were detected in the blends and were attributed to the polymer interactions and the incorporation of gold nanoparticles. In addition, the analysis of the blend topographies by atomic force microscopy (AFM) showed that at a higher CS content, more homogenous surfaces were observed. This behavior was attributed to the interactions present in the CS/PEO/AuNPs blends. Finally, theoretical analyses helped to confirm that the gold nanoparticles would be preferentially adsorbed onto the chitosan microdomains due to the interactions between acetyl and hydroxyl groups and Au atoms.

Silicon-containing oligomeric poly(amides) with phthalimidyl-amide side groups: synthesis, characterization and thermal studies

Oligomeric poly(amide)s (PAs) were synthesized from monomeric diacids, which were obtained from phthalic anhydride and the amino acid glycine, l-alanine, l-phenylalanine, l-valine, l-leucine, l-isoleucine and p-aminobenzoic acid. The phthalimidyl acids (IA-1 to IA-7) reacted with 5-amino-isophthalic acid in order to obtain the monomeric diacids (1-7). Furthermore, the monomeric diacid 8 was obtained by direct reaction between phthalic anhydride and 5-amino-isophthalic acid. The isophthalic acid derivatives were reacted with bis(4-aminophenyl)diphenylsilane in order to obtain the PAs. Monomers and polymers were characterized by infrared and 1H-, 13C- and 29Si-NMR spectroscopy, elemental analysis and, when necessary, optical rotation. The results were in agreement with the proposed structures. The yields were generally good, but the η inh values were low, indicating that the polymers were of oligomeric nature, namely, a chain of moderate molecular weight. The polymers were soluble in polar aprotic solvents and some of them were soluble in m-cresol and tetrahydrofuran. The glass transition temperatures (T g) values were obtained by differential scanning calorimetry, showing, in general, a decrease in value when the volume of the side chain of the amino acid moiety was increased. The thermal stability of the polymers was determined by dynamic thermogravimetry, showing good values of thermal decomposition temperatures (TDT), especially for those with aromatic residue in the amino acid, and for PA without amino acid. For PAs in which the side chain of the amino acid was larger, the TDT values were lower, probably due to the lack of symmetry and the length of the side chain, both of which have influence on the thermal stability.

Polymethacrylates containing indanyl groups—I. Poly(5-indanyl methacrylate). Synthesis, conformational and viscometric behaviour in dilute solution

Abstract The synthesis and dilute solution behaviour of poly(5-indanyl methacrylate) (PS-IM) is studied in THF, toluene and butanone at 298 K, by intrinsic viscosity, light scattering measurements and size exclusion chromatography (SEC). The Kuhn-Mark-Houwink-Sakurada (KMHS) relationships were established in all the solvents studied. The flexibility factors σ and C ∞ and the thermodynamic parameters A 2 and B were calculated using Zimm plots and the Stockmayer-Fixman equation, respectively. The A 2 and the B values are indicative of the presence of the excluded volume effect. The results obtained about the rigidity factors are compared with those previously found for other aromatic poly(methacrylates) and discussed in terms of the influence of the volume and interactions of the lateral chains.

Interfacial Properties of Poly(N‐Vinyl‐2‐Pyrrolidone) at the Air/Water Interface

Abstract Spread films of poly(N‐vinyl‐2‐pyrrolidone) (PVP) were studied at the air/water interface by using the Langmuir technique. Influence of the subphases of different thermodynamic conditions were analyzed. Surface pressure–area (π–A) isotherms change sensitively with the temperature. Adsorption layers (Gibbs surface excess layer) of aqueous solutions of PVP were also investigated using the interfacial tension measurements. The influence of the PVP concentration and temperature on the adsorption behavior of PVP solutions was determined. The behavior of spread films is contrasted to the behavior of surface excess layers for this polymer. The driving force for adsorption of PVP at the air/aqueous interface seems to arise from an entropic contribution. It was observed that when the polymers hydrodynamic volume decreases (0.55 M Na2SO4, θ‐solvent), a more favorable entropy adsorption was obtained. Comparison of the spread film and surface excess layer data seems to indicate that the interfacial segment density is lower in the surface excess layer than in the spread film.

Interfacial Properties of Poly(Caprolactone) and Derivatives

Abstract Monolayers of biodegradable polymers, poly(caprolactone) (PCL), poly(caprolactone) diol (PCL‐diol), and poly(caprolactone) triol (PCL‐triol) in the air/water interface were studied and characterized. The Langmuir–Blodgett technique was used for the monolayer transfer onto hydrophilic and hydrophobic solid substrates. The results obtained in both cases are dependent on the functional groups incorporated in the respective polymers. The surface energy (SE), and the polar and dispersion contributions, γp and γd, respectively, were obtained by wettability measurements. For polymeric spin‐casted thin films deposited over glass, the results also indicate an increment in the polymer hydrophilicity by hydroxyl groups insertion.

Solution properties of poly(di-1'-methylalkyl itaconates)

Abstract Di-1′-methylalkyl itaconates and the corresponding poly(di-1′-methylalkyl itaconates) (PD1′Al) containing 2-propyl (PDiPI), 2-butyl (PDiBI), 1′-methylbutyl (PDiAI), 1′-methylpentyl (PDiHI) and 1′-methyiheptyl (PDiOI) groups as side chains were synthesized and characterized. The polymers were fractionated by fractional precipitation. The fractions were characterized by viscometry in THF and acetone, and by light scattering and size exclusion chromatography in THF. The K a and a parameters of the Kuhn—Mark—Houwink—Sakurada equations were determined in THF and acetone. The stiffness of the polymer chain was estimated through the rigidity indices, a, and the characteristic ratio, C α , using the conformational parameter K Θ obtained from the Stockmayer—Fixman plots. The effect of the side-chain structure on the stiffness, conformational behaviour and glass transition temperatures, T g , of these polymers is discussed and the results compared with those corresponding to other related polymer analogues.