Daniela Lubasová

Controlled Morphology of Porous Polyvinyl Butyral Nanofibers

A simple and effective method for the fabrication of porous nanofibers based on the solvent evaporation methods in one-step electrospinning process from the commercial polyvinyl butyral (PVB) is presented. The obtained nanofibers are prevalently amorphous with diameters ranging from 150 to 4350 nm and specific surface area of approximately 2–20 m2/g. Pore size with irregular shape of the porous PVB fibers ranged approximately from 50 to 200 nm. The effects of polymer solution concentration, composition of the solvents mixture, and applied voltage on fiber diameter and morphology were investigated. The theoretical approach for the choice of poor and good solvents for PVB was explained by the application Hansen solubility parameter (HSP) and two-dimensional graph. Three basic conditions for the production of porous PVB nanofibers were defined: (i) application of good/poor solvent mixture for spinning solution, (ii) differences of the evaporation rate between good/poor solvent, and (iii) correct ratios of good/poor solvent (v/v). The diameter of prepared porous PVB fibers decreased as the polymer concentration was lowered and with higher applied voltage. These nanofiber sheets with porous PVB fibers could be a good candidate for high-efficiency filter materials in comparison to smooth fibers without pores.

Electrospun Chitosan Based Nanofibers

The new electrospinning technology NanospiderTM, offering a real potential for industrial production of nanofibers, is used for the preparation of nanofiber sheets from aqueous solutions of polymer blends. The nanofiber sheets are prepared from a mixture of chitosan and polyethylenoxide (PEO) and using the novel continual electrospinning process (Jirsak et al., 2005, www.nanospider.cz) affords a network with typical fiber diameters that are less than 500 nm. Effects of solvents, molecular weight of both polymers, monovalent salt, surfactant and composition of chitosan blend on electrospinning are also studied. The optimal conditions for electrospinning by the NanospiderTM technology, including applied high voltage, distance between both electrodes, air temperature and air humidity, are also found. The crosslinking of the nanofiber sheet is achieved by heat treatment. The morphology of electrospun fibers is observed by using a scanning electron microscope (SEM). Chitosan in the nanofiber sheets format has a great potential to be widely used in various applications derived from its biocompatibility and biodegradability.

Multi-layered nanofibrous mucoadhesive films for buccal and sublingual administration of drug-delivery and vaccination nanoparticles - important step towards effective mucosal vaccines

&NA; Nanofibre‐based mucoadhesive films were invented for oromucosal administration of nanocarriers used for delivery of drugs and vaccines. The mucoadhesive film consists of an electrospun nanofibrous reservoir layer, a mucoadhesive film layer and a protective backing layer. The mucoadhesive layer is responsible for tight adhesion of the whole system to the oral mucosa after application. The electrospun nanofibrous reservoir layer is intended to act as a reservoir for polymeric and lipid‐based nanoparticles, liposomes, virosomes, virus‐like particles, dendrimers and the like, plus macromolecular drugs, antigens and/or allergens. The extremely large surface area of nanofibrous reservoir layers allows high levels of nanoparticle loading. Nanoparticles can either be reversibly adsorbed to the surface of nanofibres or they can be deposited in the pores between the nanofibres. After mucosal application, nanofibrous reservoir layers are intended to promote prolonged release of nanoparticles into the submucosal tissue. Reversible adsorption of model nanoparticles as well as sufficient mucoadhesive properties were demonstrated. This novel system appears appropriate for the use in oral mucosa, especially for sublingual and buccal tissues. To prove this concept, trans‐/intramucosal and lymph‐node delivery of PLGA‐PEG nanoparticles was demonstrated in a porcine model. This system can mainly be used for sublingual immunization and the development of “printed vaccine technology”. Graphical abstract Figure. No caption available.

Preparation of antibacterial nanofibre/nanoparticle covered composite yarns

The antibacterial efficiency of nanofibre composite yarns with an immobilized antibacterial agent was tested. This novel type of nanofibrous composite material combines the good mechanical properties of the core yarn with the high specific surface of the nanofibre shell to gain specific targeted qualities. The main advantages of nanofibre covered composite yarns over the standard planar nanofibre membranes include high tensile strength, a high production rate, and their ability to be processed by standard textile techniques. The presented paper describes a study of the immobilization of an antibacterial agent and its interaction with two types of bacterial colonies. The aim of the study is to assess the applicability of the new composite nanomaterial in antibacterial filtration. During the experimental tests copper(II) oxide particles were immobilized in the polyurethane and polyvinyl butyral nanofibre components of a composite yarn. The antibacterial efficiency was evaluated by using both Gram-negative Escherichia coli and Gram-positive Staphylococcus gallinarum bacteria. The results showed that the composite yarn with polyvinyl butyral nanofibres incorporating copper(II) oxide nanoparticles exhibited better antibacterial efficiency compared to the yarn containing the polyurethane nanofibres. The nanofibre/nanoparticle covered composite yarns displayed good antibacterial activity against a number of bacteria.

Hydrogel properties of electrospun polyvinylpyrrolidone and polyvinylpyrrolidone/poly(acrylic acid) blend nanofibers

Hydrogel nanofibers with high water-absorption capacity and excellent biocompatibility offer wide use in biomedical areas. In this study, hydrogel nanofibers from polyvinylpyrrolidone (PVP) and PVP/poly(acrylic acid) (PAA) blend were prepared by electrospinning and by subsequent heat treatment. The effects of post-electrospinning heat treatment and PVP/PAA ratio on hydrogel properties of the nanofibers were examined. Heat treatment at a temperature above 180 °C was found to play a key role in forming insoluble and water-absorbent nanofibers. Both PVP and PVP/PAA nanofibers showed high morphology stability in water and excellent water retention capacity. The swelling ratio of PVP/PAA nanofibers declined with increasing heating temperature and decreasing PVP/PAA unit ratio. In comparison with dense casting films, these nanofiber membranes showed nearly doubled swelling ratio.

Nanofiber Sheets with the Superabsorbent Properties

The new electrospinning technology NanospiderTM offering a realistic potential for industrial production was used for creation of nanofiber sheets from aqueous solutions of partially neutralized poly(acrylic) acid with crosslinking agent. Produced nanofiber sheet was crosslinked by heat treatment. Absorption capacity and rate of absorption were tested and compared with superabsorbent particles and commercial superabsorbent fibers. The morphology of electrospun fibers was observed using a scanning electron microscope (SEM). Possibilities of fiber diameter influence were studied.

POLYAMIDE/POLYESTERAMIDE BASED NANOFIBERS

The formation of novel high aspect ratio nanofibers from polyesteramides based on e-caprolactam and e-caprolactone is reported. Nanofibers were prepared by the electrospinning method from polymer solution. Scanning electron microscopy images of nanofiber layers revealed that the diameter of fibers depended on the nature of the solvent or the mixture of solvents used and especially on the composition of polyesteramides.

Reasons for using polymer blends in the electrospinning process

Polymer blends can be very effective for the processing of nanofibers, especially for the novel electrospinning process of Nanospider™ (Jirsak et al., 2005, www.nanospider.cz), offering the realistic potential for industrial production of nanofiber sheets. Polymer blending is designed to generate materials with optimized chemical, structural, mechanical, morphological and biological properties.

Specific Cell Cultivation on Nanofibrous Layer

Recent advances in the preparation of nanofibre layers, especially using the Nanospider™ technology, allow prepare a sufficiently large area of nanofibrous layer of reproducible thickness and structure. Subsequently, it is possible to employ these layers as cell carriers and evaluate their efficiency in laboratory bioreactors. The construction of the functional hepatal bioreactor is particularly given by the positive response of hepatocyte cells to the used carrier layer as well as by the cell morphology, their viability and biological activity in certain period of time. We compared cell growth on collagen with nanofibres electrospun from selected copolymers of methacrylic esters (HEMA/EOEMA) and from differently prepared polycaprolactone (PCL) layers. The morphology was evaluated using Phaloidin/DAPI staining. On the nanofibres based on methacrylates, the cells survived and showed a common morphology comparing with cells grown on collagen (controls). On the PCL nanofibres, the cells attached well and showed a better growth than cells grown on collagen (controls). The results obtained in laboratory bioreactor proved the biochemical functionality of the studied system.