Treccani, Laura
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Treccani, Laura
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Treccani, Laura
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Item-typ:Veröffentlichung, Antibacterial active open-porous hydroxyapatite/lysozyme scaffolds suitable as bone graft and depot for localised drug deliveryAn engineered synthetic scaffold for bone regeneration should provide temporary structural support and a medium for controlled and localised release of bioavailable medical drugs. In this work, a method is proposed to incorporate biologically active agents without impairing agent activity into open-porous resorbable hydroxyapatite scaffolds. Scaffolds are obtained by a one-pot freeze gelation process and loaded with different amounts of lysozyme, a model macromolecular drug with antibacterial activity. The antibacterial activity is tested by submerging hydroxyapatite scaffolds with 0.5 to 2.5 wt.% lysozyme into two different bacteria stock solutions. A complete dieback of M. luteus bacteria when in contact with the scaffolds is observed. Higher lysozyme amount in the scaffold leads to faster dieback. In contact with scaffolds containing 2.5 wt.% lysozyme after 30 min, no viable bacteria can be observed. An amount of 0.5 wt.% lysozyme in the scaffolds is sufficient to kill all bacteria after a contact time of 24 h. For L. innocua, a bacteriostatic effect is observed. The scaffolds have spongiosa-like stability and are suitable bone implant substitutes. As agents are released from the scaffolds by degrees over a time period of at least 9 days, they are particularly attractive as depot for localised drug delivery of bioactive macromolecular drugs.Wissenschaftlicher ArtikelBand:31Heft:8131 133 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Physisorption of α-chymotrypsin on SiO2 and TiO2: A comparative study via experiments and molecular dynamics simulations(2016-01-13); ; ; ; In order to understand fundamental interactions at the interface between immobilized enzymes and ceramic supports, the authors compare the adsorption features of chymotrypsin on SiO2 and TiO2 colloidal particles by means of a combination of adsorption experiments and molecular dynamics simulations. While the dependency of the adsorption amount on pH is consistent with the trend predicted the Derjaguin-Landau-Verwey-Overbeek theory, other effects can only be rationalized if the atomic-scale details of the water-mediated protein-surface interactions are considered. On both surfaces, a clear driving force for the formation of a double monolayer at the saturation coverage is found. Although nearly equal free energies of adsorption are estimated on the two materials via a Langmuir adsorption analysis, about 50% more proteins per unit of surface can be accommodated on TiO2 than on SiO2. This is probably due to the lower surface diffusion mobility of the adsorbed protein in the latter case. Surface anchoring is realized by a combination of direct ionic interactions between charged proteins and surface sites (more pronounced for SiO2) and distinct structuring of the surface hydration layers in which the contact residues are embedded (more pronounced for TiO2). Finally, normalization of the data with respect to particle surface areas accessible to the proteins, rather than determined by means of the Brunauer-Emmett-Teller nitrogen adsorption isotherm, is crucial for a correct interpretation of the results.Wissenschaftlicher Artikel169 128 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Micromolding of Calcium Carbonate Using a Bio-Inspired, Coacervation-Mediated Process(Wiley, 2013-03-17); ; ; ; Based on a novel approach that takes into account the coacervation of calcium and poly(acrylic acid) (PAA), we were able to biomimetically produce molded micropatterned parts from amorphous calcium carbonate (ACC) particles. We studied the time- and concentration-dependent growth of Ca2+/PAA coacervate droplets using dynamic light scattering (DLS) and turbidity measurements. Applying these results for the generation of high amounts of unstable ACC particles, we were able to produce slurries that could be molded into micropatterned casts. The obtained slurries contained both micrometer sized ACC particles and smaller nano-sized particles. When both types of particles were used for molding, materials with a high surface roughness could be produced, while the micropatterns of the molds could not be reproduced properly. However, by removing the bigger particles from the slurry using only the smaller, unstable, ACC particles, good reproduction of the micropatterns could be achieved, yielding smooth surfaces with a high surface area. The processing route represents a versatile platform for the bottom-up preparation of micropatterned ceramics on the basis of calcium carbonate.Wissenschaftlicher ArtikelBand:96Heft:3115 122 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Mineralization of iron oxide by ferritin homopolymers immobilized on SiO2 nanoparticles(2018-10-25); ; ; ; The iron storage protein ferritin is well known for its ability to mineralize iron oxides in its interior cavity. In this study, the authors investigated the mineralization behavior of H and L ferritin homopolymers assembled from individual subunits. The authors’ approach included molecular dynamics simulations, which suggested that ferritin subunits arrange themselves on silica surfaces with the active side facing away from the interface, although non covalent adsorption interactions might be weak. In experimental studies, the nucleation of iron oxide nuclei could be observed at ferritin homopolymers which were covalently immobilized through the EDC/NHS strategy at the surface of silica nanoparticles. Mineralization was initiated by the addition of ammonium iron (II) sulfate hexahydrate ((NH4)2Fe(SO4)2·6H2O) as the source of iron ions and trimethylamine N-oxide as the oxidant. The results demonstrate that immobilized H and L ferritin homopolymers on silica surfaces are able to induce the formation of a cohesive thin film of magnetic iron oxide crystals (magnetite and/or maghemite).Wissenschaftlicher Artikel94 75 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Multi-loaded ceramic beads/matrix scaffolds obtained by combining ionotropic and freeze gelation for sustained and tuneable vancomycin release(Elsevier, 2016-05-24); ; ; ; For a targeted release against bacteria-associated bone diseases (osteomyelitis) ceramic beads with a high drug loading capacity, loaded with vancomycin as model antibiotic, are synthesized as drug carrier and successfully incorporated in an open porous hydroxyapatite matrix scaffold via freeze gelation to prevent bead migration at the implantation site and to extend drug release. We demonstrate that the quantity of loaded drug by the hydroxyapatite and β-tricalcium phosphate beads, produced by ionotropic gelation, as well as drug release can be tuned and controlled by the selected calcium phosphate powder, sintering temperature, and high initial vancomycin concentrations (100mg/ml) used for loading. Bead pore volume up to 68mm(3)/g, with sufficiently large open pores (pore size of up to 650nm with open porosity of 72%) and high surface area (91m(2)/g) account likewise for a maximum drug loading of 236mg/g beads or 26mg/sample. Multi-drug loading of the beads/matrix composite can further increase the maximum loadable amount of vancomycin to 37mg/sample and prolong release and antibacterial activity on Bacillus subtilis up to 5days. The results confirmed that our approach to incorporate ceramic beads as drug carrier for highly increased drug load in freeze-gelated matrix scaffolds is feasible and may lead to a sustained drug release and antibacterial activity.Wissenschaftlicher ArtikelBand:67123 155 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Protein-Mineral Interaction of Purified Nacre Proteins with Calcium Carbonate Crystals(2006-07-26); ; ; Nacre, a fascinating biogenic material consisting of calcium carbonate and organic molecules, presents remarkable mechanical and chemical properties that far exceed those of the pure components. Nacre is created by a self-organizing process guided by organic macromolecules. In particular proteins specifically control and regulate the nucleation and growth of the mineral phase, influencing the crystal morphology and polymorph selection.In this work new strategies to extract and purify proteins from the nacre of Haliotis laevigata in their native and functional state were developed and mechanisms of interaction between native nacre proteins with calcium carbonate in solution and calcium carbonate minerals were investigated. In particular the function of the intracrystalline proteins, a novel group of proteins characterized for the first time in nacre, and perlucin and perlinhibin, two already sequenced nacre proteins, were elucidated. It has been shown that each nacre protein presents a very specific and unique function in terms of calcium carbonate mineralization.Dissertation360 145 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Gel casting of large area micro- and sub-micropatterned thin ceramic tapes(Elsevier {BV}, 2016-01-20); ; ; ; In this study an easy-to-use ceramic processing technique based on temperature-controlled ionotropic gelation of alginate is presented. This method is the breakthrough for simultaneously large scale tape casting and high quality patterning of thin ceramic tapes. Alumina powder (d50¼ 205 nm) is used to cast flexible and on demand shapeable tapes. Compared to conventional ceramic micropatterning, ionotropic gelation combines complexity of the patterned structure over large-scale areas, a high pattern resolution down to sub-mm regime (400 nm) and tape thickness below 300 mm. Obtained green and sintered (1350 1C) micro- and sub-micropatterns are characterized by SEM and quantitative 3D-profilometry focusing on both, pattern quality and pattern aspect ratio. The results show that reproducible thin ceramic tapes featuring positive and negative patterns maintain their aspect ratios after demolding, drying and sintering. This processing route represents a versatile tool for designing tailored ceramics for e.g. microelectromechanical engineered systems, biomaterial or microfluidic applications.Wissenschaftlicher ArtikelBand:42Heft:499 100 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Co-delivery of cisplatin and doxorubicin from calcium phosphate beads / matrix scaffolds for osteosarcoma therapy(Elsevier, 2017-04-03); ; ; ; Bone substitute materials with a controlled drug release ability can fill cavities caused by the resection of bone tumours and thereby combat any leftover bone cancer cells. The combined release of different cytostatics seems to enhance their toxicity. In this study, calcium phosphate beads and matrix scaffolds are combined for a long-term co-delivery of cis-diamminedichloroplatinum (cisplatin, CDDP) and doxorubicin hydrochloride (DOX) as clinical relevant model drugs. Tricalcium phosphate/alginate beads as additional drug carrier are produced by droplet extrusion with ionotropic gelation and incorporated in scaffold matrix by freeze gelation without sintering. CDDP shows a short burst release while DOX has a continuous release measurable over the entire study period of 40days. Drug release from matrix is decreased by ~30% compared to release from beads. Nevertheless, all formulations follow the Korsmeyer-Peppas release kinetic model and show Fickian diffusion. Cytotoxic activity was conducted on MG-63 osteosarcoma cells after 1, 4, and 7days with WST-1 cell viability assay. Co-loaded composites enhance activity towards MG-63 cells up to ~75% toxicity while reducing the released drug quantity. The results suggest that co-loaded beads/matrix scaffolds are highly promising for osteosarcoma therapy due to synergistic effects over a long period of more than a month.Wissenschaftlicher ArtikelBand:7799 129 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Aluminium acetate as alternative cross-linker for temperature controlled gel-casting and joining of ceramics(Elsevier, 2016-01-15); ; ; ; In an earlier established gel-casting process, the biopolymer alginate is cross-linked with Ca2+-ions released through the temperature controlled dissolution of calcium iodate-particles (Ca(IO3)2). In this study, aluminum acetate (AlAc) is compared to Ca(IO3)2 as an alternative temperature controlled cross-linker for an alginate–alumina slurry. Both cross-linkers are characterized regarding gel-forming properties, resulting microstructure, impurities, mechanics of sintered parts and the ability of joining ceramic blocks in the green state via connecting gelation with and without adding slurry. Rheological measurements show that both cross-linker have a similar gelling behavior and lead to gelled blocks of high quality. AlAc-particle create a denser and more homogenous microstructure, while Ca(IO3)2-particles induce pores, abnormal grain growth and lower mechanical values. Nevertheless Ca(IO3)2 shows excellent joining properties which makes it a suitable alternative to pressure joining. In summary, AlAc is an excellent alternative cross-linker but Ca(IO3)2 remains the method of choice for joining gelled bodies.Wissenschaftlicher ArtikelBand:36Heft:5124 127