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This study presents production and biomimetic characterization of macroporous composite scaffolds based on gellan gum and nanoparticulate bioactive glass (GG-BAG) under conditions relevant for bone tissue engineering. Formation of hydroxyapatite (HAp) within the scaffolds was investigated in the simulated body fluid (SBF) during 14 days in two biomimetic bioreactors: perfusion bioreactor (1.1 ml/min SBF flowrate) and a bioreactor with coupled dynamic compression and SBF perfusion (5% strain, 0.68 Hz, 1 h on/1 h off, 1.1 ml/min SBF flowrate). HAp formation was evaluated by scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS) analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRPD). The superficial SBF velocity of 100 mu m/s in perfusion bioreactors induced the formation of abundant cauliflower-like HAp crystals throughout the scaffold interior and flake-like crystals on external surfaces resulting in improved mechanical properties as compared to the initial scaffolds. The obtained results indicate potentials of macro-porous GG-BAG scaffolds in conjunction with perfusion bioreactors for bone tissue engineering demonstrating high bioactivity suited for cultures of osteogenic cells.

New composites based on Ca-alginate hydrogels were produced that release activated charcoal (AC) particles with adsorbed povidone iodine (PVP-I) as a model antimicrobial substance in a physiological-like environment. Composite beads with different alginate (0.5-1.5% w/w) and AC (1-20% w/w) concentrations were analyzed by FE-SEM and characterized regarding textural parameters, swelling, and AC release kinetics. PVP-I was easily adsorbed onto AC particles within the optimized beads (0.5% w/w alginate, 20% w/w AC) as indicated by UV-vis spectroscopy, EDX and FT-IR analyses. The obtained beads have shown strong bactericidal effects against two standard bacterial strains (Staphylococcus aureus and Pseudomonas aeruginosa) and clinical multi-resistant wound isolates (MRSA, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Proteus mirabilis) and, at the same time, exhibited negligible PVP-I desorption in physiological saline solution. Thus, the obtained composites could provide utilization of potent antiseptics such as iodine, in wound dressings, without the concern of systemic absorption.

In this work, we present a comprehensive approach to evaluation of alginate microbeads with included silver nanoparticles (AgNPs) at the concentration range of 0.3-5 mM for potential biomedical use by combining cytotoxicity, antibacterial activity, and silver release studies. The microbeads were investigated regarding drying and rehydration showing retention of similar to 80-85% of the initial nanoparticles as determined by UV-vis and SEM analyses. Both wet and dry microbeads were shown to release AgNPs and/or ions inducing similar growth delays of Staphylococcus aureus and Escherichia coli at the total released silver concentrations of similar to 10 mu g/ml. On the other hand, these concentrations were highly toxic for bovine chondrocytes in conventional monolayer cultures while nontoxic when cultured in alginate microbeads under biomimetic conditions in 3D perfusion bioreactors. The applied approach outlined directions for further optimization studies demonstrating Ag/alginate microbeads as potentially attractive components of soft tissue implants as well as antimicrobial wound dressings.

In this study, the potential of application of non-aggressive LentiKat (R) technique for brewer's yeast immobilization on polyvinyl alcohol was assessed. High cell loads of about 109 cells/ml were achieved by this procedure and immobilization procedure had no adverse effect on cell viability. The stability and activity of obtained immobilized biocatalyst was tested in the growth studies and fermentations. Immobilized cells exhibited high fermentation activity in both, laboratory and pilot-scale fermentations. In three successive gas-lift reactor fermentations the apparent attenuation of around 80% was reached after only 2 days, indicating good potential of immobilized cells for development of continuous primary beer fermentation. LentiKat (R) particles showed high mechanical and fermentative stability, since they endured 30 days of operating time during 6-month period without significant change of cell activity, particle shape and particle size.

Lipase from Candida rugosa was immobilized on Cuprophane membrane in a hollow-fibre module for possible application for oil hydrolysis. A simple immobilization technique was applied and 154.8 mg m(-2) lipase was immobilized with approximately 40% mass yield. The reactor operating regime was investigated with respect to flow patterns in reactor zones, lipase desorption and hydrolysis rates. Flow pattern studies in the experimental system revealed nearly plug flow with a stagnant region in the reactor lumen and significant flow channeling in the shell zone. Mass transfer limitations were apparent in the lumen zone at flow rates below 15 cm(3) min(-1). Higher flow rates up to 50 cm(3) min(-1) in the lumen zone and in the range 2.5-26 cm(3) min(-1) in the shell side had no apparent influence on hydrolysis rates. At the enzyme load employed in this study, loss of enzyme activity due to desorption had little effect on reactor stability and oil hydrolysis.

Lipase from Candida rugosa was immobilized in alginate beads for possible application in non-aqueous or microaqueous reaction systems. An electrostatic droplet generation technique was used for production of small diameter ( lt 1 mm) lipase-alginate beads. This technique provided negligible loss of the lipase (immobilization efficiencies were 98.2-99.2%). Under optimal immobilization conditions (applied potential 4.9 kV, needle gauge 21, 2% sodium alginate solution) the lipase-alginate beads, 0.65 mm in diameter, retained enzyme activity equivalent to 75% that of free lipase. The activity of the immobilized lipase was verified in the reaction of palm oil hydrolysis in a lecithin/isooctane system. The reaction rate with alginate-immobilized lipase was lower than with the free enzyme but the final conversions were approximately the same (similar to 74%). Immobilized lipase could be used for up to three reaction cycles with little loss of activity.

The structure and function of cartilaginous constructs, engineered in vitro using bovine articular chondrocytes, biodegradable scaffolds and bioreactors, can be modulated by the conditions and duration of tissue cultivation. We hypothesized that the integrative properties of engineered cartilage depend on developmental stage of the construct and the extracellular matrix content of adjacent cartilage, and that some aspects of integration can be studied under controlled in vitro conditions. Disc-shaped constructs (cultured for 5 +/- 1 days or 5 +/- 1 weeks) or explants (untreated or trypsin treated cartilage) were sutured into ring-shaped explants (untreated or trypsin treated cartilage) to form composites that were cultured for an additional 1-8 weeks in bioreactors and evaluated biochemically, histologically and mechanically (compressive stiffness of the central disk, adhesive strength of the integration interface). Immature constructs had poorer mechanical properties but integrated better than either more mature constructs or cartilage explants. Integration of immature constructs involved cell proliferation and the progressive formation of cartilaginous tissue, in contrast to the integration of more mature constructs or native cartilage which involved only the secretion of extracellular matrix components. Integration patterns correlated with the adhesive strength of the disc-ring interface, which was markedly higher for immature constructs than for either more mature constructs or cartilage explants. Trypsin treatment of the adjacent cartilage further enhanced the integration of immature constructs.

The substantial concern with the possible use of immobilized yeast cells for beer production is reduction of internal mass transfer resistance during continuous fermentation. One way to minimise this problem is to use small-diameter beads. The effects of bead diameters in the range 0.3-2.0 mm on yeast cell immobilization and growth over a short-term cultivation were investigated. Bead diameters in the range 0.5-0.6 mm were optimal and provided rapid cell growth and the highest final cell concentration (2.33 x 10(9) cells/ml of beads). Electrostatic droplet generation was investigated as a technique for production of alginate microbeads. The effects of applied potential, internal needle diameter and electrode position on bead diameter were assessed. The results have shown that this method can be used for controlled production of small-size microbeads loaded with yeast. Depending on applied conditions it was possible to produce the beads in the range 250 mum-2.0 mm in diameter.