RESUMO

Cardiovascular diseases (CVD), such as myocardial infarction (MI), constitute one of the world's leading causes of annual deaths. This cardiomyopathy generates a tissue scar with poor anatomical properties and cell necrosis that can lead to heart failure. Necrotic tissue repair is required through pharmaceutical or surgical treatments to avoid such loss, which has associated adverse collateral effects. However, to recover the infarcted myocardial tissue, biopolymer-based scaffolds are used as safer alternative treatments with fewer side effects due to their biocompatibility, chemical adaptability and biodegradability. For this reason, a systematic review of the literature from the last five years on the production and application of chitosan scaffolds for the reconstructive engineering of myocardial tissue was carried out. Seventy-five records were included for review using the "preferred reporting items for systematic reviews and meta-analyses" data collection strategy. It was observed that the chitosan scaffolds have a remarkable capacity for restoring the essential functions of the heart through the mimicry of its physiological environment and with a controlled porosity that allows for the exchange of nutrients, the improvement of the electrical conductivity and the stimulation of cell differentiation of the stem cells. In addition, the chitosan scaffolds can significantly improve angiogenesis in the infarcted tissue by stimulating the production of the glycoprotein receptors of the vascular endothelial growth factor (VEGF) family. Therefore, the possible mechanisms of action of the chitosan scaffolds on cardiomyocytes and stem cells were analyzed. For all the advantages observed, it is considered that the treatment of MI with the chitosan scaffolds is promising, showing multiple advantages within the regenerative therapies of CVD.

Assuntos

Quitosana , Infarto do Miocárdio , Humanos , Quitosana/química , Alicerces Teciduais/química , Fator A de Crescimento do Endotélio Vascular , Infarto do Miocárdio/metabolismo , Miócitos Cardíacos/metabolismo , Engenharia Tecidual

RESUMO

Parahydrophobic surfaces (PHSs) composed of arrays of cubic µ-pillars with a double scale of roughness and variable wettability were systematically obtained in one step and a widely accessible stereolithographic Formlabs 3D printer. The wettability control was achieved by combining the geometrical parameters (H = height and P = pitch) and the surface modification with fluoroalkyl silane compounds. Homogeneous distribution of F and Si atoms onto the pillars was observed by XPS and SEM-EDAX. A nano-roughness on the heads of the pillars was achieved without any post-treatment. The smallest P values lead to surfaces with static contact angles (CAs) >150° regardless of the H utilized. Interestingly, the relationship 0.6 ≤ H/P ≤ 2.6 obtained here was in good agreement with the H/P values reported for nano- and submicron pillars. Furthermore, experimental CAs, advancing and receding CAs, were consistent with the theoretical prediction from the Cassie-Baxter model. Structures covered with perfluorodecyltriethoxysilane with high H and short P lead to PHSs. Conversely, structures covered with perfluorodecyltrimethoxysilane exhibited a superhydrophobic behavior. Finally, several aqueous reactions, such as precipitation, coordination complex, and nanoparticle synthesis, were carried out by placing the reactive agents as microdroplets on the parahydrophobic pillars, demonstrating the potential application as chemical multi-reaction array platforms for a large variety of relevant fields in microdroplet manipulation, microfluidics systems, and health monitoring, among others.

RESUMO

In nature, superhydrophobic surfaces (SHSs) exhibit microstructures with several roughness scales. Scalable fabrication and build-up along the X-Y plane represent the promise of 3D printing technology. Herein we report 3D printed microstructures with a dual roughness scale that achieves SHS using a readily available Formlabs stereolithography (SLA) printer. Pillar-like structure (PLS) arrangements with a wide range of geometrical shapes were 3D printed at three resolutions and two printing orientations. We discovered that a tilted printing direction enables a stair-case pattern on the µ-PLS surfaces, conferring them a µ-roughness that reduces the solid-liquid contact area. The programmed resolution governs the number of polymerized layers that give rise to the stepped pattern on the µ-PLS surfaces. However, this is reduced as the printing resolution increases. Also, all samples' experimental contact angles were consistent with theoretical predictions from Cassie-Baxter, Wenzel, and Nagayama wettability models. The underlying mechanisms and governing parameters were also discussed. It is believed that this work will enable scalable and high throughput roughness design in augmenting future 3D printing object applications.

RESUMO

The design of new materials with two or more functional groups must be strongly considered to achieve multifunctional coatings with outstanding properties such as active-passive protection against corrosion, low-friction, antifouling, and sensing, among others. In this sense, nanocomposites based on solvent-free epoxy resin/bifunctionalized reduced graphene oxide layers with NH2 and NH3+ groups (ER/BFRGO) with super-anticorrosive properties are for the first time reported here. The amine groups (-NH2) act as cross-linker agents, which react with epoxy terminal groups from resin, thus closing the gap between the BFRGO layers and the polymeric matrix. Meanwhile, the ammonium ions (-NH3+) are effective trapping agents of negatively charged atoms or molecules (e.g., Cl-). This novel combination enables us to obtain nanocomposite coatings with passive-active protection against corrosion. ER/BFRGO deposited onto A36 mild steel exhibited a remarkably enhanced barrier against corrosion into a saline medium (1 M NaCl; 58.4 g/L), wherein the corrosion current density (icorr) was diminished 6 orders of magnitude (icorr = 5.12 × 10-12 A/cm2), with respect to A36 mild steel coated only with ER (icorr = 2.34 × 10-6 A/cm2). Also, the highest polarization resistance Rp = 6.04 × 107 Ω/cm2 was obtained, which represents the lowest corrosion rate and corresponds to 3 orders of magnitude higher than A36 mild steel coated with ER (Rp = 1.43 × 104 Ω/cm2). The strategy of bifunctionalization proposed herein to obtain bifunctionalized reduced GO with NH2 and NH3+ groups has not been disclosed in the literature before; in consequence, this work opens a new pathway toward the design of smart materials based on multifunctional nanomaterials.

RESUMO

The structure of the title compound, C16H14O2, features a dihedral angle of 54.4 (3)° between the aromatic rings. The allyl group is rotated by 37.4 (4)° relative to the adjacent benzene ring. The crystal packing is characterized by numerous C-H⋯O and C-H⋯π inter-actions. Most of these inter-actions occur in layers along (011). The layers are linked by C-H⋯π inter-actions along [100], forming a three-dimensional network.

RESUMO

The title compound, C26H26S4, shows a dihedral angle of 76.64 (15)° between the central and peripheral benzene rings. An inversion center is located at the centroid of the thio-benzoyl ring. In the crystal, weak C-H⋯S inter-actions form C(5) chains along [001]. There are no classical hydrogen bonds.

RESUMO

The mol-ecular structure of the title compound, C9H14O4S3, exhibits intra-molecular C-H⋯S hydrogen bonds. In the crystal, pairs of O-H⋯O hydrogen bonds lead to the formation of centrosymmetric dimers, which are in turn connected by weak C-H⋯O inter-actions. The combination of these inter-actions generates edge-fused R 2 (2)(8) and R 2 (2)(20) rings running along [211].

RESUMO

In the title compound, C(21)H(18)O(4), the outer benzyl rings are disordered over two resolved positions in a 0.50 ratio. The O-CH(2) groups form dihedral angles of 4.1 (2) and 10.9 (4)° with the central benzene ring, adopting a syn-anti conformation with respect to this ring. In the crystal, the mol-ecules are linked by O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions, forming chains along [010].