Novel bioresorbable tricalcium phosphate/polyhydroxyoctanoate (TCP/PHO) composites as scaffolds for bone tissue engineering applications

Development of new composite materials for bone tissue engineering is a constantly growing field of medicine. Therefore there is a continuous need in creating novel materials that can not only regenerate the defected tissue but also nourish it while the healing process progresses. Here we present a novel type of composite material that fulfils these requirements. The study describes creation of a composite with macroporous bioceramic core that is infiltrated with a thin biopolymer layer. The ceramic component, namely tricalcium phosphate (TCP), due to its mechanistic and bioactive properties may promote new bone creation as shown through the in vitro studies. To the best of our knowledge the coating layer was created for the first time from a representative of bacterially derived medium chain length polyhydroxyalkanoate polymers (mcl-PHA), namely polyhydroxyoctanoate (PHO). This polymer layer not only profoundly changed the stress-strain characteristics of the bioceramic foam but also released (R)-3-hydroxyacids and their dimers/trimers to the investigated environment. In the manuscript we have in depth characterised these materials employing a set of basic procedures, through 3D structure reconstruction and finishing with prolonged in vitro experiments

Variable-length contexts for ppm

This is a preprint of an article presented at DCC’04, published i

Efektywna reprezentacja dokumentów XML

Seria : Problemy Współczesnej Nauki, Teoria i Zastosowanie. Badania Operacyjne i SystemoweArtykuł omawia metody efektywnej reprezentacji dokumentów XML. Przedstawiono w nim opracowaną przez autorów transformację przekształcającą dokument XML do skróconej postaci, która następnie może być poddana dalszej kompresji algorytmami ogólnego przeznaczenia. Wyniki kompresji testowego zestawu dokumentów z użyciem transformacji zestawiono z wynikami dotychczas dostępnych algorytmów kompresji XML oraz ogólnego przeznaczenia. Uzyskana średnia poprawa stopnia kompresji wyniosła od 8% w stosunku do jednego z najlepszych znanych algorytmów, XMLPPM, do 38% dla algorytmu zaimplementowanego w programie Zip. Sprawdzono także, jak zastosowanie kompresji, z uwzględnieniem czasu dekompresji, przekłada się na czas oczekiwania na dokument przez użytkownika. Zbadano wpływ poszczególnych składników transformacji na końcowy efekt

Software—Practice and Experience

The innate verbosity of the Extensible Markup Language remains one of its main weaknesses, especially when large XML documents are concerned. This problem can be solved with the aid of XML-specialized compression algorithms. In this work, we describe a fast and fully reversible XML transform which, combined with generally used LZ77-style compression algorithms, allows to attain high compression ratios, comparable to those achieved by the current state-of-the-art XML compressors. The resulting compression scheme is asymmetric in the sense that its decoder is much faster than the coder. This is a desirable practical property as in case of many XML applications data are read much more often than written. The key features of the transform are dictionary-based encoding of both document structure and content, separation of different content types into multiple streams, and dedicated encoding of numbers and dates. The test results show the proposed transform to improve the XML compression efficiency of general purpose compressors on average by 35 % in case of gzip and 17% in case of LZMA. Compared to the current state-of-the-art SCMPPM algorithm, XWRT with LZMA attains over 2 % better compression ratio, being 55 % faster

Silver and silicon doped βTCP scaffolds with gentamicin or ceftazidime loaded P(3HB) coatings as multifunctional biomaterials for bone regeneration

The risk of bacterial infections is a significant challenge faced frequently in the use of implants or scaffolds for bone regeneration. Therefore, this study focusses on the development and characterisation of novel β tricalcium phosphate (βTCP) scaffolds co-doped with silver and silicon, along with composites coated with antibiotic-loaded poly(3-hydroxybutyrate) (P(3HB)) layers. The successful incorporation of silver and silicon dopants while maintaining the formation of βTCP phase was confirmed using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) analysis. The developed materials demonstrated comparable total and open porosity (∼64–70 vol%), suggesting high interconnectivity between pores conducive to nutrient transport and tissue repair. The increase in compressive strength was achieved for both doped (4.73 ± 0.79 MPa) and P(3HB) coated (5.79 ± 0.92 MPa) scaffolds due to the fine bioceramic microstructure and polymeric coating. Silver and silicon-modified βTCP demonstrated enhanced growth inhibition of Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains in vitro compared to the pure βTCP. P(3HB) coatings, enriched with gentamicin or ceftazidime, exhibited burst and sustained release of the antibiotics from the scaffolds up to 120 h further intensifying the bacteria-killing capability, with evident inhibition zones observed in vitro. Moreover, the composites exhibited apatite-forming ability, suggesting their bioactive potential. In vivo evaluation using Caenorhabditis elegans demonstrated the lack of toxicity of the tested materials. The simultaneous incorporation of the dopants and antibiotic-loaded P(3HB) coatings not only offer a dual antibacterial approach but may also facilitate bone regeneration. However, further in vitro and in vivo investigations are needed to assess their potential in clinical application