Electrospun nanosized cellulose fibers using ionic liquids at room temperature

Aiming at replacing the noxious solvents commonly employed, ionic-liquid-based solvents have been recently explored as novel non-volatile and non-flammable media for the electrospinning of polymers. In this work, nanosized and biodegradable cellulose fibers were obtained by electrospinning at room temperature using a pure ionic liquid or a binary mixture of two selected ionic liquids. The electrospinning of 8 wt% cellulose in 1-ethyl-3-methylimidazolium acetate medium (a low viscosity and room temperature ionic liquid capable of efficiently dissolving cellulose) showed to produce electrospun fibers with average diameters within (470 ± 110) nm. With the goal of tailoring the surface tension of the spinning dope, a surface active ionic liquid was further added in a 0.10 : 0.90 mole fraction ratio. Electrospun cellulose fibers from the binary mixture composed of 1-ethyl-3-methylimidazolium acetate and 1-decyl-3-methylimidazolium chloride ionic liquids presented average diameters within (120 ± 55) nm. Scanning electron microscopy, X-ray diffraction analysis, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric assays were used as core methods to evaluate the structural integrity, morphology and crystallinity of the raw, electrospun, and regenerated samples of cellulose. Moreover, the photoluminescence spectra of both raw and electrospun fibers were acquired, and compared, indicating that the cellulose emitting centers are not affected by the dissolution of cellulose in ionic liquids. Finally, the use of non-volatile solvents in electrospinning coupled to a water coagulation bath allows the recovery of the ionic fluid, and represents a step forward into the search of environmentally friendly alternatives to the conventional approaches

Carrageenan-based hydrogels for the controlled delivery of PDGF-BB in bone tissue engineering applications

One of the major drawbacks found in most bone tissue engineering approaches developed so far consists in the lack of strategies to promote vascularisation. Some studies have addressed different issues that may enhance vascularisation in tissue engineered constructs, most of them involving the use of growth factors (GFs) that are involved in the restitution of the vascularity in a damaged zone. The use of sustained delivery systems might also play an important role in the re-establishment of angiogenesis. In this study, !-carrageenan, a naturally occurring polymer, was used to develop hydrogel beads with the ability to incorporate GFs with the purpose of establishing an effective angiogenesis mechanism. Some processing parameters were studied and their influence on the final bead properties was evaluated. Platelet derived growth factor (PDGF-BB) was selected as the angiogenic factor to incorporate in the developed beads, and the results demonstrate the achievement of an efficient encapsulation and controlled release profile matching those usually required for the development of a fully functional vascular network. In general, the obtained results demonstrate the potential of these systems for bone tissue engineering applications.This work was supported by the European NoE EXPERTISSUES (NMP3-CT-2004-500283), the European STREP HIPPOCRATES (NMP3-CT-2003-505758), and by the Portuguese Foundation for Science and Technology (FCT) through the project PTDC/FIS/68517/2006 and through the V. Espirito Santo's Ph.D. grant (SFRH/BD/39486/2007)

High throughput methods applied in biomaterial development and discovery

The high throughput discovery of new materials can be achieved by rapidly screening many different materials synthesised by a combinatorial approach to identify the optimal material that fulfils a particular biomedical application. Here we review the literature in this area and conclude that for polymers, this process is best achieved in a microarray format, which enable thousands of cell-material interactions to be monitored on a single chip. Polymer microarrays can be formed by printing pre-synthesised polymers or by printing monomers onto the chip where on-slide polymerisation is initiated. The surface properties of the material can be analysed and correlated to the biological performance using high throughput surface analysis, including time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurements. This approach enables the surface properties responsible for the success of a material to be understood, which in turn provides the foundations of future material design. The high throughput discovery of materials using polymer microarrays has been explored for many cell-based applications including the isolation of specific cells from heterogeneous populations, the attachment and differentiation of stem cells and the controlled transfection of cells. Further development of polymerisation techniques and high throughput biological assays amenable to the polymer microarray format will broaden the combinatorial space and biological phenomenon that polymer microarrays can explore, and increase their efficacy. This will, in turn, result in the discovery of optimised polymeric materials for many biomaterial applications

Understanding the relation between structural and mechanical properties of electrospun fiber mesh through uniaxial tensile testing

Polymeric electrospun fibers have the potential to be utilized for a variety of applications such as tissue engineering, filtration, and textiles, owing to their high surface area per unit mass. However, these applications have some form of dependency on the mechanical properties of fiber meshes. Therefore, the current study is aimed at understanding the mechanical behavior of electrospun fiber systems at different length scales in order to establish a correlation between their structure and mechanical properties. Micro-/nano-fiber meshes of polystyrene were fabricated by the process of electrospinning and were subjected to uniaxial tensile testing. High-resolution imaging during tensile testing revealed the macroscopic and microscopic structural evolution of these fibers. Further, the dependence of tensile strength, % elongation, and toughness of fiber meshes on the orientation of the fibers were also experimentally observed. The continuum mechanics simulation studies of fiber meshes with different orientations corroborated well with these experimental studies. Comprehensively, these studies demonstrated the changes in mechanical behavior of electrospun fiber meshes owing to the reorientation and alignment of fibers in meshes at microscopic and macroscopic length scale during tensile testing. Such study can be extrapolate for the design and fabrication of load-bearing tissues scaffolds, and filtration devices. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45012

Appraisal of 1-Butylimidazole-Derived Ionic Liquids as Anthelmintic Agents: An Experimental and In Silico Approach

We have synthesized and characterized 1-butyl-3-alkylimidazolium derived ionic liquids (ILs) functionalized with various alkyl groups (-C2H5, -C4H9, -C6H13, -C8H17, and -C10H21) and counter anions ((Formula presented.)). Further, these ILs were tested for the vermicidal activity and cell-viability study against the Pheretima posthuma (Indian earthworm) and MC3T3-L1 cells, respectively. IL-OH with higher alkyl chains (-C10H21) displayed promising vermicidal activity as compared to other counterparts (IL−Br and IL-BF4). Further, quantitative-structure-activity-relationships (QSAR) modelling was carried out using density functional theory (DFT) derived quantum mechanical descriptors to assess the factors responsible for the biological activities. Based on the QSAR study it was found that LUMO of the anion and polar surface area of the cation possess significant correlation (r2, 0.85; RMSE, 0.06). Also, receptor-binding based molecular docking was carried out to study the binding patterns of the tested IL. Introduction. In past few decades, ionic liquids (ILs) have generated paramount interest in several field of chemistry, i.e., catalysis, electrochemistry,, biotechnology, biomass energy and pharmaceutical applications–, and many others. This wide range of applications are due to their characteristic tunable nature of ILs which facilitate desired biochemical properties via varying their counter anions and alkyl chain length., Subsequent tailoring of biologically active cations or anions can add substantial potential to their therapeutic implication and administration as active pharmaceutical ingredients (APIs)., Efforts are made to probe the effects of various anions, alkyl chains and charge on the quaternary nitrogen atom. It has been articulated that medicinal aspect of ILs is greatly impeded by their toxicity; however, attempts are in the progress to afford a balance between toxicity and biochemical/ biopharmaceutical properties. In particular, the maxim “poison is in the dose”, encouraged to develop ILs as useful therapeutics. Earlier, we have screened the imidazolium derived ILs for their vermicidal activity with varying alkyl chains (R= -C2H5, -C4H9, -C6H13, -C8H17) and Br−/OH− as counter anions

Photoresist derived electrospun carbon nanofibers with tunable morphology and surface properties

A new precursor, SU-8, which is a negative photoresist, was electrospun to produce ultrafine polymeric fibers with a wide range of morphology and wettability characteristics. Electrospun nanofibers of SU-8 were pyrolyzed at 1173 K in an inert atmosphere to give carbon nanofibers. A set of parameters, including electric potential, distance between source and collector, polymer flow rate, and polymer concentration, was optimized for high-viscosity SU-8 photoresist to synthesize long continuous carbon fibers having diameters in the range of 120-600 nm. However, for the same conditions, medium- and lower-viscosity SU-8 yielded beaded fibers and isolated beads, respectively. The wettability of the carbon web was significantly influenced by its surface morphology, as shown by water contact angle measurements. These SU-8-derived carbon nanostructures with tunable surface properties and morphologies could be especially suitable for integration with photoresist-based carbon-MEMS to produce multiscale hierarchal assemblies and could be of potential use in a broad range of applications