Nanostructured Chitosan-Based Biomaterials for Sustained and Colon-Specific Resveratrol Release

In the present work, we demonstrate the preparation of chitosan-based composites as vehicles of the natural occurring multi-drug resveratrol (RES). Such systems are endowed with potential therapeutic effects on inflammatory bowel diseases (IBD), such as Crohn’s disease (CD) and ulcerative colitis, through the sustained colonic release of RES from long-lasting mucoadhesive drug depots. The loading of RES into nanoparticles (NPs) was optimized regarding two independent variables: RES/polymer ratio, and temperature. Twenty experiments were carried out and a Box–Behnken experimental design was used to evaluate the significance of these independent variables related to encapsulation efficiency (EE). The enhanced RES EE values were achieved in 24 h at 39 °C and at RES/polymer ratio of 0.75:1 w/w. Sizes and polydispersities of the optimized NPs were studied by dynamic light scattering (DLS). Chitosan (CTS) dispersions containing the RES-loaded NPs were ionically gelled with tricarballylic acid to yield CTS-NPs composites. Macro- and microscopic features (morphology and porosity studied by SEM and spreadability), thermal stability (studied by TGA), and release kinetics of the RES-loaded CTS-NPs were investigated. Release patterns in simulated colon conditions for 48 h displayed significant differences between the NPs (final cumulative drug release: 79–81%), and the CTS-NPs composites (29–34%)

The spatially resolved star formation history of CALIFA galaxies: Cosmic time scales

This paper presents the mass assembly time scales of nearby galaxies observed by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record method of the stellar populations to the complete sample of the 3rd CALIFA data release, with a total of 661 galaxies, covering stellar masses from 10$^{8.4}$ to 10$^{12}$ M$_{\odot}$ and a wide range of Hubble types. We apply spectral synthesis techniques to the datacubes and process the results to produce the mass growth time scales and mass weighted ages, from which we obtain temporal and spatially resolved information in seven bins of galaxy morphology and six bins of stellar mass (M$_{\star}$) and stellar mass surface density ($\Sigma_{\star}$). We use three different tracers of the spatially resolved star formation history (mass assembly curves, ratio of half mass to half light radii, and mass-weighted age gradients) to test if galaxies grow inside-out, and its dependence with galaxy stellar mass, $\Sigma_{\star}$, and morphology. Our main results are as follows: (a) The innermost regions of galaxies assemble their mass at an earlier time than regions located in the outer parts; this happens at any given M$_{\star}$, $\Sigma_{\star}$, or Hubble type, including the lowest mass systems. (b) Galaxies present a significant diversity in their characteristic formation epochs for lower-mass systems. This diversity shows a strong dependence of the mass assembly time scales on $\Sigma_{\star}$ and Hubble type in the lower-mass range (10$^{8.4}$ to 10$^{10.4}$), but a very mild dependence in higher-mass bins. (c) All galaxies show negative $\langle$log age$\rangle_{M}$ gradients in the inner 1 HLR. The profile flattens with increasing values of $\Sigma_{\star}$. There is no significant dependence on M$_{\star}$ within a particular $\Sigma_{\star}$ bin, except for the lowest bin, where the gradients becomes steeper.Comment: 15 pages, 13 figures, 3 tables, accepted for publication in Astronomy & Astrophysics. *Abridged abstract

The spatially-resolved star formation histories of CALIFA galaxies: Implications for galaxy formation

This paper presents the spatially resolved star formation history (SFH) of nearby galaxies with the aim of furthering our understanding of the different processes involved in the formation and evolution of galaxies. To this end, we apply the fossil record method of stellar population synthesis to a rich and diverse data set of 436 galaxies observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, with stellar masses ranging from $M_\star \sim 10^9$ to $7 \times 10^{11} M_\odot$. Spectral synthesis techniques are applied to the datacubes to retrieve the spatially resolved time evolution of the star formation rate (SFR), its intensity ($\Sigma_{\rm SFR}$), and other descriptors of the 2D-SFH in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd), and five bins of stellar mass. Our main results are: a) Galaxies form very fast independently of their current stellar mass, with the peak of star formation at high redshift ($z > 2$). Subsequent star formation is driven by $M_\star$ and morphology, with less massive and later type spirals showing more prolonged periods of star formation. b) At any epoch in the past the SFR is proportional to $M_\star$, with most massive galaxies having the highest absolute (but lowest specific) SFRs. c) While nowadays $\Sigma_{\rm SFR}$ is similar for all spirals, and significantly lower in early type galaxies (ETG), in the past $\Sigma_{\rm SFR}$ scales well with morphology. The central regions of today's ETGs are where $\Sigma_{\rm SFR}$ reached the highest values ($> 10^3 \,M_\odot\,$Gyr$^{-1}\,$pc$^{-2}$), similar to those measured in high redshift star forming galaxies. d) The evolution of $\Sigma_{\rm SFR}$ in Sbc systems matches that of models for Milky-Way-like galaxies, suggesting that the formation of a thick disk may be a common phase in spirals at early epochs.Comment: 21 pages, 11 figures, 1 table, accepted for publication in Astronomy & Astrophysics, abstract abridged for arXiv submissio