Macrophage activation can be modulated by biomaterial topography according to the biological scale (micrometric and nanometric range). In this study, we investigated the effect of fiber diameter and fiber alignment of electrospun poly(L-lactic) (PLLA) scaffolds on macrophage RAW 264.7 activation and secretion of proinflammatory cytokines and chemokines at 24 h and 7 days. Macrophages were cultured on four different types of fibrous PLLA scaffold (aligned microfibers, aligned nanofibers, random microfibers, and random nanofibers) and on PLLA film (used as a reference). Substrate topography was found to influence the immune response activated by macrophages, especially in the early inflammation stage. Secretion of proinflammatory molecules by macrophage cells was chiefly dependent on fiber diameter. In particular, nanofibrous PLLA scaffolds minimized the inflammatory response when compared with films and microfibrous scaffolds. The histological evaluation demonstrated a higher number of foreign body giant cells on the PLLA film than on the micro- and nanofibrous scaffolds. In summary, our results indicate that the diameter of electrospun PLLA fibers, rather than fiber alignment, plays a relevant role in influencing in vitro macrophage activation and secretion of proinflammatory molecules.

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In this paper we report on the characteristics of a polymer Li-ion battery based on a unique combination of innovative electrode and electrolyte materials. In particular, the electrolytic separator of this system is based on gelled membranes prepared by the electrospinning technique. Electrospinning of polymer fibers is usually realized by applying a strong electric field to a polymer solution in an appropriate solvent. Typical membranes (mats) consist of nanometre size fibers and have porosities of 56-85%. Here we describe the fabrication, physical chemistry and electrochemical properties of PVdF (poly(vinylidene difluoride))-based electrospun membranes and their use as gelled electrolyte in Li-ion battery. Moreover, we describe the performances of a battery formed by sandwiching a gelled membrane with a nanoscale engineered Sn-C based anode and a lithium nickel manganese oxide spinel cathode. The battery so obtained has an appealing performance in terms of energy density, power capability, cycle life and safety.

A novel type of hydrolase was purified from culture fluid of Paucimonas (formerly Pseudomonas) lemoignei. Biochemical characterization revealed an unusual substrate specificity of the purified enzyme for amorphous poly((R)-3-hydroxyalkanoates) (PHA) such as native granules of natural poly((R)-3-hydroxybutyrate) (PHB) or poly((R)-3-hydroxyvalerate) (PHV), artificial cholatecoated granules of natural PHB or PHV, atactic poly((R,S)-3-hydroxybutyrate), and oligomers of (R)-3-hydroxybutyrate (3HB) with six or more 3HB units. The enzyme has the unique property to recognize the physical state of the polymeric substrate by discrimination between amorphous PHA (good substrate) and denatured, partially crystalline PHA (no substrate). The pentamers of 3HB or 3HV were identified as the main products of enzymatic hydrolysis of native PHB or PHV, respectively. No activity was found with any denatured PHA, oligomers of (R)-3HB with five or less 3HB units, poly(6-hydroxyhexanoate), substrates of lipases such as tributyrin or triolein, substrates for amidases/nitrilases, DNA, RNA, casein, N-␣-benzoyl-L-arginine-4-nitranilide, or starch. The purified enzyme (M r 36,209) was remarkably stable and active at high temperature (60°C), high pH (up to 12.0), low ionic strength (distilled water), and in solvents (e.g. n-propyl alcohol). The depolymerase contained no essential SH groups or essential disulfide bridges and was insensitive to high concentrations of ionic (SDS) and nonionic (Triton and Tween) detergents. Characterization of the cloned structural gene (phaZ7) and the DNA-deduced amino acid sequence revealed no homologies to any PHB depolymerase or any other sequence of data banks except for a short sequence related to the active site serine of serine hydrolases. A classification of the enzyme into a new family (family 9) of carboxyesterases (Arpigny, J. L., and Jaeger, K.-E. (1999) Biochem. J. 343, 177-183) is suggested.Poly((R)-3-hydroxyalkanoic acids) (PHAs) 1 are a class of storage compounds that are synthesized during unbalanced growth by many bacteria. PHAs are deposited intracellularly in the form of inclusion bodies ("granules") to levels up to 90% of the cellular dry weight. The subject was reviewed recently (1). Poly((R)-3-hydroxybutyric acid) (PHB) is the most abundant polyester in bacteria. Bacterial copolymers containing randomly distributed (R)-3-hydroxybutyric and (R)-3-hydroxyvaleric units (poly(3HB-co-3HV)) have been commercialized for over a decade under the trade name Biopol ® . Any research on the biodegradation of PHA should clearly distinguish between (i) extracellular PHA degradation and (ii) intracellular PHA degradation. (i) Extracellular degradation is the utilization of an exogenous carbon/energy source by a notnecessarily-accumulating microorganism. The source of this extracellular polymer is PHA-released by accumulating cells after death. The ability to degrade PHA is widely distributed among bacteria and depends on the secretion of specific PHA depolymerases that are carboxyesterases (EC 3.1.1) a...

Blends of synthetic atactic poly(3-hydroxybutyrate) (a-PHB) with a natural bacterial isotactic copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV) containing 10 mol % of 3HV units were prepared using a simple casting procedure. In the range of compositions explored (10−50% a-PHB), blends of bacterial PHBV and synthetic atactic a-PHB were miscible in the melt and solidified with spherulitic morphology. The influence of a-PHB content on the thermal and mechanical properties of the blends was evaluated. The degree of crystallinity decreased with increasing content of a-PHB in the film samples, and the elongation at break for a sample containing 50% of a-PHB was 30-fold that of pure PHBV. Degradation experiments, both hydrolytic (pH = 7.4, T = 70 °C) and enzymatic (PHB-depolymerase A from Pseudomonas lemoignei, Tris-HCl buffer (pH = 8), T = 37 °C), were performed for both polymers and polymer blends. The rate of enzymatic degradation of the blends was higher than that of PHBV and increased with a-PHB content in the blends studied, whereas pure a-PHB did not biodegrade under these conditions. 3-Hydroxybutyric acid and its dimer were identified by HPLC as biodegradation products of both pure PHBV and its blends with a-PHB. Higher oligomers up to heptamer were detected as degradation products of the blends by APCI-MS and ESI-MS.

The crystal structure of poly(ω‐pentadecalactone) (PPDL) synthesized by enzyme‐catalyzed polymerization was determined by full‐profile refinement. A pseudo‐orthorombic monoclinic unit cell with dimensions a = 7.49(1), b = 5.034(9), and c = 20.00(4)Å (fiber axis), and α = 90.06(4)° hosts two monomeric units belonging to polymer chains with opposite orientation, according to the P21 space‐group symmetry. A close similarity to the crystal structure of poly(ϵ‐caprolactone) was evident. However, the even number of backbone atoms in the monomer unit of PPDL leads to a lower crystal symmetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1009–1013, 2003

Over the past six decades, engineered composite materials found wide ranging applications in land, sea and air transport vehicles, space exploration, military equipment and defense, storage, buildings and construction, chemical processing, electrical engineering, healthcare, and general engineering industries. Performance of engineered composites is tailored for an intended application by judiciously selecting the matrix and reinforcement materials, by modifying the fiber–matrix interface, and by controlling the architecture of fibers in the matrix. Most widely used reinforcement fibers are micron size diameter fibers. There is growing need for engineered composites with enhanced structural performance in newer applications as well as existing applications, which are expected to meet higher functional requirements and enhanced safety requirements. Moreover the global movement toward sustainable development is seeking engineered materials which are environmentally benign. Recently the electrospinning process has emerged as a viable industrial process to produce nanofibers from a variety of materials including naturally occurring polymers. This paper illustrates the benefits of using electrospun nanofibers in enhancing the structural performance of engineered composite materials. Copyright © 2010 John Wiley & Sons, Ltd.

Blends of atactic poly[(R,S)-3-hydroxybutyrate], a-PHB, with poly(ε-caprolactone), PCL, and with poly(l-lactic acid), PLLA, were obtained in the form of compression-molded films. The phase behavior of the blends was different:  a-PHB and PCL were totally immiscible, whereas a-PHB/PLLA blends were miscible over the whole composition range. Biodegradation experiments were carried out on the blends and on the plain polymers in a buffered solution of PHB-depolymerase A from Pseudomonas lemoignei (Tris−HCl, pH = 8, T = 37 °C). None of the pure blend components (a-PHB, PCL, PLLA) showed any weight loss upon enzyme exposure. Conversely, both a-PHB/PCL and a-PHB/PLLA blends biodegraded. Analysis of the biodegradation products and of blend composition changes during biodegradation demonstrated that in both blends only the a-PHB component undergoes enzymatic hydrolysis. The results support the hypothesis that the crystalline polyester blended with a-PHB promotes a-PHB enzymatic hydrolysis by providing stable binding sites to the enzyme. The dependence of biodegradation rate on blend composition is different in (immiscible) a-PHB/PCL and (miscible) a-PHB/PLLA blends and can be explained in terms of different phase behavior and morphology.