Synthesis and properties of Poly(L-lactide)-b-poly (L-phenylalanine) hybrid copolymers

Hybrid materials constituted by peptides and synthetic polymers have nowadays a great interest since they can combine the properties and functions of each constitutive block, being also possible to modify the final characteristics by using different topologies. Poly(L-lactide-b-L-phenylalanine) copolymers with various block lengths were synthesized by sequential ring-opening polymerization of L-lactide and the N-carboxyanhydride of L-phenylalanine. The resulting block copolymers were characterized by NMR spectrometry, IR spectroscopy, gel permeation chromatography, MALDI-TOF and UV-vis, revealing the successful incorporation of the polyphenylalanine (PPhe) peptide into the previously formed poly(L-lactide) (PLLA) polymer chain. X-ray diffraction and DSC data also suggested that the copolymers were phase-separated in domains containing either crystalline PLLA or PPhe phases. A peculiar thermal behavior was also found by thermogravimetric analysis when polyphenylalanine blocks were incorporated into polylactide.Peer ReviewedPostprint (published version

Smart systems related to polypeptide sequences

Increasing interest for the application of polypeptide-based smart systems in the biomedical field has developed due to the advantages given by the peptidic sequence. This is due to characteristics of these systems, which include: biocompatibility, potential control of degradation, capability to provide a rich repertoire of biologically specific interactions, feasibility to self-assemble, possibility to combine different functionalities, and capability to give an environmentally responsive behavior. Recently, applications concerning the development of these systems are receiving greater attention since a targeted and programmable release of drugs (e.g. anti-cancer agents) can be achieved. Block copolymers are discussed due to their capability to render differently assembled architectures. Hybrid systems based on silica nanoparticles are also discussed. In both cases, the selected systems must be able to undergo fast changes in properties like solubility, shape, and dissociation or swelling capabilities. This review is structured in different chapters which explain the most recent advances on smart systems depending on the stimuli to which they are sensitive. Amphiphilic block copolymers based on polyanionic or polycationic peptides are, for example, typically employed for obtaining pH-responsive systems. Elastin-like polypeptides are usually used as thermoresponsive polymers, but performance can be increased by using techniques which utilize layer-by-layer electrostatic self-assembly. This approach offers a great potential to create multilayered systems, including nanocapsules, with different functionality. Recent strategies developed to get redox-, magnetic-, ultrasound-, enzyme-, light-and electric-responsive systems are extensively discussed. Finally, some indications concerning the possibilities of multi-responsive systems are discussed.Postprint (published version

Injection molding and characterization of microtextures on polycarbonate using laser textured inserts

The purpose of this paper is to demonstrate the easy manufacturing and quick characterization of several microtextured functional surfaces on two transparent thermoplastics of general interest for several industrial sectors. Microtextured polymeric surfaces with special optical, tribological and easy-cleaning properties were manufactured via isothermal injection-molding using laser-microtextured steel mold inserts. For that purpose, conventional injection molding of two chosen amorphous transparent polymers (polycarbonate, PC, and polymethyl methacrylate, PMMA) utilizing laser-microtextured steel inserts was carried out, and a detailed morphological and functional characterization of the injected specimens was conducted later on. We also report on the suitable process conditions for the injection molding of these specimens using design of experiment (DOE) techniques. The analysis of the degree of replication (DR%) on the injected samples shows that mold temperature and injection speed are the most relevant parameters to obtain a successful replication and confirm the viability of conventional injection molding as a processing technique to obtain microtextured functional surfaces in amorphous transparent thermoplastics. The success of the procedure is further checked by the confirmation of the obtained surface functionalities by various standard and self-developed methods.Peer ReviewedPostprint (published version

Electrospun scaffolds of polylactide with a different enantiomeric content and loaded with anti-inflammatory and antibacterial drugs

Polylactide (PLA) electrospun microfibers were prepared and loaded with triclosan (TCS), ketoprofen (KTP), or their combination to obtain multifunctional scaffolds with bactericide and anti-inflammatory properties. Continuous and porous fibers with diameters in the micrometer scale and a unimodal distribution were successfully attained using a dual-electrospinning technique. Dual drug-loaded scaffolds showed a peculiar release that was in contrast to the single drug-loaded systems, which suggested the establishment of intermolecular interactions that delayed TCS and KTP release. Antimicrobial activity of all TCS-loaded electrospun scaffolds was demonstrated against E. coli and M. luteus bacteria; and furthermore, KTP-loaded samples slightly showed bactericide activity. Biocompatibility of scaffolds was evaluated by adhesion and proliferation assays, and interestingly, the dual drug-load systems were able to support high TCS doses without adverse effects.Peer ReviewedPostprint (author's final draft

Copolymers and blends based on 3-Hydroxybutyrate and 3-Hydroxyvalerate Units

This review presents a comprehensive update of the biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), emphasizing its production, properties, and applications. The overall biosynthesis pathway of PHBV is explored in detail, highlighting recent advances in production techniques. The inherent physicochemical properties of PHBV, along with its degradation behavior, are discussed in detail. This review also explores various blends and composites of PHBV, demonstrating their potential for a range of applications. Finally, the versatility of PHBV-based materials in multiple sectors is examined, emphasizing their increasing importance in the field of biodegradable polymers.Peer ReviewedPostprint (published version

Biodegradable Poly(Ester Amide)s: Synthesis and Applications

Postprint (published version

Degradable Poly(ester amide)s for biomedical aplications

Poly(ester amide)s are an emerging group of biodegradable polymers that may cover both commodity and speciality applications. These polymers have ester and amide groups on their chemical structure which are of a degradable character and provide good thermal and mechanical properties. In this sense, the strong hydrogen‑bonding interactions between amide groups may counter some typical weaknesses of aliphatic polyesters like for example poly(e-caprolactone). Poly(ester amide)s can be prepared from different monomers and following different synthetic methodologies which lead to polymers with random, blocky and ordered microstructures. Properties like hydrophilic/hydrophobic ratio and biodegradability can easily be tuned. During the last decade a great effort has been made to get functionalized poly(ester amide)s by incorporation of a-amino acids with hydroxyl, carboxyl and amine pendant groups and also by incorporation of carbon-carbon double bonds in both the polymer main chain and the side groups. Specific applications of these materials in the biomedical field are just being developed and are reviewed in this work (e.g., controlled drug delivery systems, hydrogels, tissue engineering and other uses like adhesives and smart materials) together with the main families of functionalized poly(ester amide)s that have been developed to date.Peer ReviewedPostprint (published version

Effects of hydroxyapatite (0001) Ca2+/Mg2+ substitution on adsorbed D-ribose ring puckering

Advanced Molecular Dynamics (MD) simulation protocols have been used to assess the ring puckering of cyclic D-ribose when the sugar is adsorbed on the most stable (0001) facet of calcium hydroxyapatite (HAp). In addition, sugar¿mineral interactions, which are crucial for transfection processes and prebiotic chemistry, have been studied for systems in which the Ca2+ ions of the above mentioned HAp facet were totally or partially replaced by Mg2+. The latter replacement is spatially and quantitatively limited and has been found to cause important alterations in the conformational behavior of D-ribose that are similar to those suffered in hairpin RNA from A to B helical structures. Accordingly, replacement of Ca2+ by Mg2+ has a dramatic effect on the functionality of the nucleic acid. These changes have been related to both the substitution site on the surface and the amount of ions. Our results show that when replacement by Mg2+ occurs in OH--coordinated Ca2+ ions, Mg2+¿D-ribose interactions are strong enough to prevent the interactions between the hydroxyl groups of the sugar and the remaining Ca2+ ions.Peer ReviewedPostprint (published version

Temperature induced structural changes in even-odd nylons with long polymethylene segments

Structural transitions of nylons 8 9 and 12 9 heating and cooling processes were investigated using calorimetric, spectroscopic during and real time X-ray diffraction data. These even-odd nylons had three polymorphic forms related to structures where hydrogen bonds were established in two planar directions. Heating processes showed a first structural transition at low temperature where the two strong reflections related to the packing mode of the low temperature structure (form I) disappeared instead of moving together and merging into a single reflection, as observed for conventional even-even nylons. The high temperature structure corresponded to a typical pseudohexagonal packing (form III) attained after the named Brill transition temperature. Structural transitions were not completely reversible since an intermediate structure (form II) became clearly predominant at room temperature in subsequent cooling processes. A single spherulitic morphology with negative birefringence and a flat-on edge-on lamellar disposition was obtained when the two studied polyamides crystallized from the melt state. Kinetic analyses indicated that both nylons crystallized according to a single regime and a thermal nucleation. Results also pointed out a secondary nucleation constant for nylon 12 9 higher than that for nylon 8 9, suggesting greater difficulty in crystallizing when the amide content decreased. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2494–2506Peer ReviewedPostprint (author's final draft

Segmental relaxation and partial crystallization of chain-extended Poly(l-lactic acid) reinforced with carboxylated carbon nanotube

Temperature-modulated differential scanning calorimetry (TMDSC) and broadband dielectric spectroscopy (BDS) were employed to study the glass transition, size of the cooperative rearranging regions (CRRs), crystallization kinetics, and dielectric relaxation response of nanocomposites constituted by chain-extended poly(L-lactide) (PLLA) and carboxylated carbon nanotubes (f-CNTs). The CRR size and the number of relaxing structural units decreased in the presence of crystals during isothermal crystallization. All samples displayed both a primary (a) and secondary (ß) relaxation in BDS spectra. The relaxation dynamics of PLLA chains was barely affected by the presence of the f-CNT. Constrained polymer chains and thickness of interphase (t i) were measured using dielectric spectra in tan d representation. t i values were found to be 46 and 24 nm for sample containing 0.2 and 0.5% weight fraction of f-CNT, respectively. All samples underwent partial crystallization (with roughly 30% of final crystalline fraction) some 15 or 20° above their glass-transition temperature (T g). Crystallization leads to a fragile-to-strong transition in the temperature dependence of the cooperative a relaxation and to the increased visibility of a Maxwell–Wagner–Sillars (MWS) interfacial relaxation, which appears to be present in all samples. The heterogeneity of the polymeric samples was quantified in terms of a new parameter, the heterogeneity index (H).Peer ReviewedPostprint (published version