Jose A. Tornero

Drug delivery systems using sandwich configurations of electrospun poly(lactic acid) nanofiber membranes and ibuprofen

The primary advantages of electrospun membranes include the ability to obtain very thin fibers that are on the order of magnitude of several nanometers with a considerable superficial area and the possibility for these membranes to be manipulated and processed for many different applications. The purpose of this study is to evaluate and quantify the transport mechanisms that control the release of drugs from polymer-based sandwich membranes produced using the electrospinning processes. These electrospun membranes were composed of poly(lactic acid) (PLA) because it is one of the most promising biodegradable polymers due to its mechanical properties, thermoplastic processability and biological properties, such as its biocompatibility and biodegradability. The transport mechanism that controls the drug delivery was evaluated via the release kinetics of a bioactive agent in physiological serum, which was used as a corporal fluid simulation. To describe the delivery process, mathematical models, such as the Power Law, the classical Higuchi equation and an approach to Ficks Second Law were used. Using the applied mathematical models, it is possible to conclude that control over the release of the drug is significantly dependent on the thickness of the membrane rather than the concentration of the drug.

Resolving the Electrospinnability Zones and Diameter Prediction for the Electrospinning of the Gelatin/Water/Acetic Acid System

The development of suitable biomimetic scaffolds is a fundamental requirement of tissue engineering. Although electrospinning has emerged as an effective method for producing such scaffolds of nanometer-sized fibers, the influence of solution characteristics on the morphology of the resulting nanofibers depends on each polymer solution system. In this study, gelatin nanofibers and microfibers were prepared via electrospinning using mixtures of water and acetic acid at different ratios as solvents. The viscosities of gelatin solutions before electrospinning were analyzed and two different behaviors were found as a function of the solvent composition, taking into account classic models of polymer science. A power law relationship between viscosity and gelatin concentration was found for each solvent system, and an empirical model including the influence of acetic acid was obtained for aqueous systems. Moreover, a ternary diagram considering gelatin, water, and acetic acid mass fractions was constructed as a tool to establish the electrospinnability domains in terms of fiber occurrence and morphology. Also, the isodiametric curves were defined in the fibers region. Finally, in order to correlate the diameter of electrospun nanofibers and the electrospinnability zones, the Berry number was used. However, as its only allows the range of electrospinnability to be established for a fixed solvent composition, a new dimensionless parameter (Bemod) was suggested to take into account all the acetic acid aqueous solutions as a single solvent.

Effects of needling parameters on some structural and physico-mechanical properties of needle-punched nonwovens

The main objective of this paper is to study the effects of the processing parameters of the needle-punching machine and the interactions between them on some physico-mechanical properties of interest of nonwoven (NW) fabrics. For this purpose, a fractional factorial design has been planned with two levels for each factor: feeding speed, delivery speed, stroke frequency, penetration depth and gap between plates. Sixteen NW fabrics were obtained from polyester fibre and characterized by tensile strength and stiffness for mechanical behaviour and air permeability as physical properties of interest in some technical applications. The results have been subjected to statistical analysis in order to find the effects of the processing variables and the interactions between them on the fabric properties. It was possible to find the effects of the five processing parameters studied on the thickness, fabric mass, stiffness, tensile strength and air permeability of the obtained needle-punched fabrics.

High temperature transformation of electrospun BaZrO3 nanotubes into nanoparticle chains

BaZrO3 nanofibers were electrospun from a 0.25 M metal cation solution containing barium acetate and zirconium 2,4-pentadionate dissolved in glacial acetic acid. Polyvinylpyrrolidone was added to increase the solution viscosity and allow formation of hollow fibers during electrospinning. Microstructural evolution during thermal annealing at temperatures between 600 °C and 1400 °C was studied revealing crystal growth evolution. Strong grain coarsening is observed above 1200 °C, leading to linear and branched nanoparticle chains originating from the finer initial hollow nanofibers. Faceting of the nanoparticles occurs in the low-energy surfaces. On the other hand, grain boundaries are planar and follow the same facet planes as the nanoparticles. High resolution transmission electron microscopy reveals no general epitaxial relationship at the interface with the exception of a minor amount of low angle grain boundaries.

Epitaxial BaZrO3 tracks by electrospinning of metalorganic fibers on single crystals

Electrospinning was used to produce fibers of barium zirconate (BZO) by metalorganic decomposition. Using short deposition times, a low density of randomly distributed fibers were deposited on lanthanum aluminate single crystals with (100) orientation. Then the films were subjected to thermal treatment at 600 °C and 800 °C to decompose the organic matter and crystallize the perovskite phase. X-ray diffraction, field-emission electron and atomic force microscopies were used as characterization tools. Continuous BZO tracks are obtained after removal of organics at 600 °C. At 800 °C, cube-on-cube heteroepitaxy of barium zirconate with respect to the lanthanum aluminate template was detected by synchrotron X-ray diffraction, although a fraction of misoriented BaZrO3 crystals were also detected by grazing incidence X-ray diffraction (GIXRD). For precursor fibers closely attached to the single crystal surface, BaZrO3 grows as epitaxial nanoparticles, which then coarsen and self-organize along the fiber tracks, showing oscillations in the interparticle separation distance. Growth of the coarsened low-aspect ratio crystals follows an anisotropic atomic diffusion mechanism, in which mass transport mainly occurs in the direction of the initially deposited fiber. The misoriented nanoparticles observed by GIXRD are attributed to the fibers deposited on top of those arriving first to the substrate and to the loss of the interfacial epitaxial growth at large crystal thickness. The distribution and morphology of the particles have been further analyzed by means of atomic force microscopy.

Embroidery manufacturing techniques for textile dipole antenna applied to wireless body area network

This paper addresses the design, simulation, manufacturing, and experimental test of textile dipole antennas based on advanced embroidery techniques. The proposed dipoles are intended to operate at the 2.45 GHz industrial scientific and medical radio band for wireless body area network applications. Two medium stitch density embroidery patterns have been studied, satin fill and contour fill, implemented according to the ISO 4915:1991 301 stitch type standard. The impact and viability of these embroidery techniques over the dipole performance in cotton and felt textile substrates are reported. Test results confirm notable antenna parameter results in terms of return loss, radiation pattern, realized gain, and efficiency. In particular, contour pattern has been revealed as the best embroidery manufacturing technique in terms of quality factor and losses, whereas the satin pattern fits the resonance frequency of the antenna with a higher degree of accuracy.

Tissue Compatibility of SN-38-Loaded Anticancer Nanofiber Matrices

Delivery of chemotherapy in the surgical bed has shown preclinical activity to control cancer progression upon subtotal resection of pediatric solid tumors, but whether this new treatment is safe for tumor-adjacent healthy tissues remains unknown. Here, Wistar rats are used to study the anatomic and functional impact of electrospun nanofiber matrices eluting SN-38-a potent chemotherapeutic agent-on several body sites where pediatric tumors such as neuroblastoma, Ewing sarcoma, and rhabdomyosarcoma arise. Blank and SN-38-loaded matrices embracing the femoral neurovascular bundle or in direct contact with abdominal viscera (liver, kidney, urinary bladder, intestine, and uterus) are placed. Foreign body tissue reaction to the implants is observed though no histologic damage in any tissue/organ. Skin healing is normal. Tissue reaction is similar for SN-38-loaded and blank matrices, with the exception of the hepatic capsule that is thicker for the former although within the limits consistent with mild foreign body reaction. Tissue and organ function is completely conserved after local treatments, as assessed by the rotarod test (forelimb function), hematologic tests (liver and renal function), and control of clinical signs. Overall, these findings support the clinical translation of SN-38-loaded nanofiber matrices to improve local control strategies of surgically resected tumors.