Agnieszka Tercjak

A multipurpose natural and renewable polymer in medical applications: Bacterial cellulose

Bacterial cellulose (BC) produced by some bacteria, among them Gluconacetobacter xylinum, which secrets an abundant 3D networks fibrils, represents an interesting emerging biocompatible nanomaterial. Since its discovery BC has shown tremendous potential in a wide range of biomedical applications, such as artificial skin, artificial blood vessels and microvessels, wound dressing, among others. BC can be easily manipulated to improve its properties and/or functionalities resulting in several BC based nanocomposites. As example BC/collagen, BC/gelatin, BC/Fibroin, BC/Chitosan, etc. Thus, the aim of this review is to discuss about the applicability in biomedicine by demonstrating a variety of forms of this biopolymer highlighting in detail some qualities of bacterial cellulose. Therefore, various biomedical applications ranging from implants and scaffolds, carriers for drug delivery, wound-dressing materials, etc. that were reported until date will be presented.

Conductive properties of TiO2/bacterial cellulose hybrid fibres

Conductive properties of TiO(2) nanoparticles and TiO(2)/BC hybrid inorganic/organic fibres were investigated by electrostatic force microscopy (EFM). TiO(2)/BC hybrid composites were prepared based on bacterial cellulose produced by Gluconobacterxylinum, being the bacterial cellulose as a hydrophilic substrate for TiO(2) nanoparticles synthesized via sol-gel. Taken into account hydrophilic nature of the cellulose, TiO(2) nanoparticles were located on the surface of the fibres due to hydrogen bonding interactions. EFM was used to determine qualitatively conductive properties of TiO(2) nanoparticles and their TiO(2)/BC hybrid inorganic/organic fibres. Results indicate that TiO(2)/BC hybrid fibres respond to applied bias regardless of the sign of the applied voltage.

Conductive behavior of high TiO2 nanoparticle content of inorganic/organic nanostructured composites.

Amphiphilic polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers with different block ratios were used as templates for the incorporation of a high content of titanium dioxide nanoparticles using the sol-gel method. Confinement of the inorganic part in the PEO block of the block copolymer allows the generation of nanostructured systems with a high nanoparticle content. As successfully demonstrated using tunneling atomic force microscopy, the investigated systems maintained the conductive properties of the TiO(2) nanoparticles. The obtained results confirmed that with increasing TiO(2) nanoparticle content, the local current value increased up to 15 pA, and this conductivity value strongly depended on the amount of the PEO block in the block copolymer template. Moreover, the results indicated that control of the ratio between the sol-gel and the PEO block allows the design of well-dispersed, conductive inorganic/organic hybrids with high inorganic content. These materials can provide attractive strategies in the field of dye-sensitized solar cells.

The effect of thermal and vapor annealing treatments on the self-assembly of TiO2 /PS-b-PMMA nanocomposites generated via the sol–gel process

Polystyrene-block-poly(methyl methacrylate) (SMMA) block copolymer has been used as a structure-directing agent for generating TiO2 /SMMA nanocomposites via the sol-gel process using a hydrophobic surfactant. The aim of the work has been focused on the preparation of well-defined nanostructured composites based on the self-assembling capability of the block copolymer using two different annealing methods: thermal- and solvent-induced microphase separation. The addition of different amounts of nanoparticles caused strong variations in the self-assembled morphology of the TiO2 /SMMA nanocomposites with respect to the block copolymer, as observed by atomic force microscopy (AFM). To verify the confinement of the nanoparticles in the PMMA block 3D AFM images and corresponding AFM profiles have also been reported. UV light irradiation of the nanocomposite films provoked the removal of the organic matrix and consequently led to an array of TiO2 nanoparticles on the substrate surface.

Conductive Photoswitchable Vanadium Oxide Nanopaper based on Bacterial Cellulose

A bacterial cellulose mat was used as a template for the fabrication of conductive photoswitchable hybrid nanopaper by the incorporation of sol-gel synthesized vanadium nanoparticles. The resulting nanopaper, prepared through a green pathway, was able to photoinduce a reversible color change. Conductive properties at the nano- and macroscales were confirmed by electrostatic force microscopy and semiconductor analysis measurements, respectively.

Multifunctional hybrid nanopapers based on bacterial cellulose and sol–gel synthesized titanium/vanadium oxide nanoparticles

The hybrid inorganic/organic nanopapers based on bacterial cellulose and different type of sol–gel synthesized nanoparticles are fabricated. A simple, rapid, low-cost pathway based on a diffusion step of sol–gel nanoparticles into swollen bacterial cellulose membrane via orbital incubator is developed. This alternative pathway allows to keeping intact the 3D network of the bacterial cellulose membrane while sol–gel nanoparticles are formed in situ and anchored on the nanofibers surface. Titanium, vanadium oxide nanoparticles and a mixture of both are used to functionalize bacterial cellulose membrane. Fabricated hybrid inorganic/organic nanopapers are characterized by thermogravimetric analysis, X-ray diffraction spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, MTS mechanical testing, UV–vis spectroscopy, colorimeter and semiconductor analyzer. Synthesized photochromic hybrid nanopapers modified with vanadium and titanium oxide nanoparticles can find potential application as sensitive displays, biosensors and other optical devices.

Biocellulose-based flexible magnetic paper

Biocellulose or bacterial cellulose (BC) is a biocompatible (nano) material produced with a three-dimensional network structure composed of microfibrils having nanometric diameters obtained by the Gluconacetobacter xylinus bacteria. BC membranes present relatively high porosity, allowing the incorporation or synthesis in situ of inorganic nanoparticles for multifunctional applications and have been used as flexible membranes for incorporation of magnetic nanocomposite. In this work, highly stable superparamagnetic iron oxide nanoparticles (SPION), functionalized with polyethylene glycol (PEG), with an average diameter of 5 nm and a saturation magnetization of 41 emu/g at 300 K were prepared. PEG-Fe2O3 hybrid was dispersed by mixing a pristine BC membrane in a stable aqueous dispersion of PEG-SPION. The PEG chains at PEG-SPIONs surface provide a good permeability and strong affinity between the BC chains and SPION through hydrogen-bonding interactions. PEG-SPION also allow the incorporation of higher cont...

Nano- and Macroscale Structural and Mechanical Properties of in Situ Synthesized Bacterial Cellulose/PEO‑b‑PPO‑b‑PEO Biocomposites

Highly transparent biocomposite based on bacterial cellulose (BC) mat modified with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymer (EPE) were fabricated in situ during biosynthesis of bacterial cellulose in a static culture from Gluconacetobacter xylinum. The effect of the addition to the culture medium of water-soluble EPE block copolymer on structure, morphology, crystallinity, and final properties of the novel biocomposites was investigated at nano- and macroscale. High compatibility between components was confirmed by ATR-FTIR indicating hydrogen bond formation between the OH group of BC and the PEO block of EPE block copolymer. Structural properties of EPE/BC biocomposites showed a strong effect of EPE block copolymer on the morphology of the BC mats. Thus, the increase of the EPE block copolymer content lead to the generation of spherulites of PEO block, clearly visualized using AFM and MO technique, changing crystallinity of the final EPE/BC biocomposites investigated by XRD. Generally, EPE/BC biocomposites maintain thermal stability and mechanical properties of the BC mat being 1 wt % EPE/BC biocomposite material with the best properties. Biosynthesis of EPE/BC composites open new strategy to the utilization of water-soluble block copolymers in the preparation of BC mat based biocomposites with tunable properties.

Effect of Poly(ethylene oxide) Homopolymer and Two Different Poly(ethylene oxide-b-poly(propylene oxide)-b-poly(ethylene oxide) Triblock Copolymers on Morphological, Optical, and Mechanical Properties of Nanostructured Unsaturated Polyester

Novel nanostructured unsaturated polyester resin-based thermosets, modified with poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and two poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymers (BCP), were developed and analyzed. The effects of molecular weights, blocks ratio, and curing temperatures on the final morphological, optical, and mechanical properties were reported. The block influence on the BCP miscibility was studied through uncured and cured mixtures of unsaturated polyester (UP) resins with PEO and PPO homopolymers having molecular weights similar to molecular weights of the blocks of BCP. The final morphology of the nanostructured thermosetting systems, containing BCP or homopolymers, was investigated, and multiple mechanisms of nanostructuration were listed and explained. By considering the miscibility of each block before and after curing, it was determined that the formation of the nanostructured matrices followed a self-assembly mechanism or a polymerization-induced phase separation mechanism. The miscibility between PEO or PPO blocks with one of two phases of UP matrix was highlighted due to its importance in the final thermoset properties. Relationships between the final morphology and thermoset optical and mechanical properties were examined. The mechanisms and physics behind the morphologies lead toward the design of highly transparent, nanostructured, and toughened thermosetting UP systems.

Selective confinement of oleylamine capped Au nanoparticles in self-assembled PS-b-PEO diblock copolymer templates

Amphiphilic polystyrene-block-polyethylene oxide (PS-b-PEO) block copolymers (BCPs) have been demonstrated to be effective in directing organization of colloidal Au nanoparticles (NPs). Au NPs have been incorporated into the polymer and the different chemical affinity between the NP surface and the two blocks of the BCP has been used as a driving force of the assembling procedure. The morphology of the nanocomposites, prepared and fabricated as thin films, has been investigated by means of atomic force and scanning electron microscopies as a function of the NP content and BCP molecular weight. NPs have been effectively dispersed in PS-b-PEO hosts at any investigated content (up to 17 wt%) and a clear effect of the BCP properties on the final nanocomposite morphology has been highlighted. Finally, electrostatic force microscopy has demonstrated the conductive properties of the nanocomposite films, showing that the embedded Au NPs effectively convey their conductive properties to the film. The overall investigation has confirmed the selective confinement of the as-prepared surfactant-coated metal NPs in the PS block of PS-b-PEO, thus proposing a very simple and prompt assembling tool for nanopatterning, potentially suitable for optoelectronic, sensing and catalysis applications.