Search

The industrial interest in the patterning of polymeric surfaces at the micro/nanoscale to include new functionalities has considerably increased during the last years. Hierarchical organization of micro/nanometric surface textures yields enhanced functional properties such as hydrophobicity, hydrophilicity, antibacterial activity, and optical or chromatic effects to cite some. While high accuracy methods to pattern hierarchical surfaces at the nanoscale have been developed, only some of them have been applied for high volume manufacturing with limited success, mainly because they rely on the use of expensive machinery and moulds or complicated inserts. Therefore, a method using low cost recyclable tooling and process conditions applicable to high-volume manufacturing is currently missing. In this work, a scalable and low-cost method to replicate hierarchical micro/nanostructured surfaces on plastic films is presented, which can be latter used as inlays for injection moulded parts with standard processing conditions. This method is used to demonstrate the feasibility of replicating three level hierarchical micro/nano textured surfaces using recyclable bio-based polymers (of high relevancy in the current plastic pollution context) achieving replication ratios above 90%, comparing the replication results with those obtained in polypropylene. The presence of the micro/nanotextures substantially increases the contact angle of all the polymers tested, yielding values higher than 90° in all the cases. Also, various mechanical properties of the replicated parts for all the polymers injected are characterized one and thirty days after the samples were manufactured, showing fairly constant values. This highlights the validity of the replicated surfaces, regardless of the biopolymers special crystallization characteristics.

Amorphous molecule-macromolecule mixtures are ubiquitous in polymer technology and are one of the most studied routes for the development of amorphous drug formulations. For these applications it is crucial to understand how the preparation method affects the properties of the mixtures. Here, we employ differential scanning calorimetry and broadband dielectric spectroscopy to investigate dispersions of a small-molecule drug (the Nordazepam anxiolytic) in biodegradable polylactide, both in the form of solvent-cast films and electrospun microfibres. We show that the dispersion of the same small-molecule compound can have opposite (plasticizing or antiplasticizing) effects on the segmental mobility of a biopolymer depending on preparation method, temperature, and polymer enantiomerism. We compare two different chiral forms of the polymer, namely, the enantiomeric pure, semicrystalline L-polymer (PLLA), and a random, fully amorphous copolymer containing both L and D monomers (PDLLA), both of which have lower glass transition temperature (Tg) than the drug. While the drug has a weak antiplasticizing effect on the films, consistent with its higher Tg, we find that it actually acts as a plasticizer for the PLLA microfibres, reducing their Tg by as much as 14 K at 30%-weight drug loading, namely, to a value that is lower than the Tg of fully amorphous films. The structural relaxation time of the samples similarly depends on chemical composition and morphology. Most mixtures displayed a single structural relaxation, as expected for homogeneous samples. In the PLLA microfibres, the presence of crystalline domains increases the structural relaxation time of the amorphous fraction, while the presence of the drug lowers the structural relaxation time of the (partially stretched) chains in the microfibres, increasing chain mobility well above that of the fully amorphous polymer matrix. Even fully amorphous homogeneous mixtures exhibit two distinct Johari–Goldstein relaxation processes, one for each chemical component. Our findings have important implications for the interpretation of the Johari–Goldstein process as well as for the physical stability and mechanical properties of microfibres with small-molecule additives.

Poly(e-caprolactone) (PCL) films reinforced with polylactide (PLA) microfibers were prepared by two methodologies: a) melt pressing of an electrospun PLA mat between two PCL films, and b) melt pressing of a co-electrospun mat composed of PLA microfibers and PCL nanofibers. Electrospinning conditions were selected for each polymer to obtain films loaded with 10, 20 and 30 wt% of PLA. Thermal and mechanical properties varied depending on the preparation method. Thus, PLA crystallinity was higher when films were obtained by the co-electrospinning process, as revealed from DSC and synchrotron X-ray diffraction data since cold crystallization of the highly oriented PLA microfibers was favored in the subsequent heating run when they were in close contact with PCL nanofibers. Samples obtained by co-electrospinning also showed higher mechanical properties (e.g. Young modulus) with increasing PLA load. In this case, fracture surfaces showed significant interactions between fibers and the PCL matrix and decreased fiber pull-out. All fabrics were also loaded with chlorhexidine (CHX) as a hydrophilic bactericide agent. A delayed release was observed when the drug was only loaded into the electrospun PLA microfibers, and diffusion varied with the method of preparation. In all cases, samples had a clear bactericide effect against Gram positive and Gram negative bacteria. Nevertheless, the protective effect was slightly lower when CHX was only loaded in the reinforcing PLA microfibers.

© BME-PT. In this work we present the drug release properties and morphological studies of fibers formed by mixing different ratios of poly(lactic acid) (PLA) and poly(3-thiophene methyl acetate) (P3TMA) loaded with four drugs (ciprofloxacin, chlorhexidine dihydrochloride, triclosan and ibuprofen sodium salt). Thus, the main aim of this study is to prove that the excellent cellular response of PLA-P3TMA biocompatible scaffolds can be successfully combined with essential applications as drug carrier and delivery systems. Atomic force microscopic (AFM) and scanning electron microscopic (SEM) micro-graphs of PLA-P3TMA fibers indicate that the presence of the conducting polymer inside the PLA matrix affects the surface morphology, resulting in a significant increment of the bulk conductivity with respect to PLA fibers. Electrospun hybrid fibers of PLA and P3TMA successfully load both hydrophilic and hydrophobic drugs, the release profiles depending on the release environment (i.e. the release rate increases with the hydrophobicity of the medium). Finally, our results prove that the antibacterial activity of the drugs is not affected by their interactions with the PLA-P3TMA matrix.

We designed a 16S rRNA gene PCR -RFLP scheme to identify all currently described Bartonella spp. The 16S rRNA genes of all Bartonella spp. were in-silico analyzed in order to design a RFLP technique able to discriminate among different species. The restriction enzymes selected were Mae III, Mse I, Sau96 I, Bsa AI, Drd I, Fok I, Bss HII, Bst UI, Alu I, Tsp DTI and Hph I which, according to a decision -making tree, faci litated the differentiation of all the currently described species of Bartonella .The technique was experimentally tested in different species of Bartonella , including human pathogenic B. bacilliformis and B. henselae with a 100% of concordance with the in-silico predicted patterns.This novel RFLP assay could be used to identify both human and non- human pathogenic Bartonella in diagnostic, phylogenetic and epidemiologic studies