Monika Šupová

Problem of hydroxyapatite dispersion in polymer matrices: a review.

This review summarizes recent work on manufacturing biocomposites suitable for bone tissue engineering. There is a great need to engineer multi-phase (i.e. composite) materials that combine the advantages exhibited by each component of the material, with a structure and composition similar to that of natural bone. The discussion concentrates on the preparation of nanocomposites containing hydroxyapatite particles (one of the most widely used bioceramics materials) with polymer matrices. Special attention is paid to the preparation of nanocomposites with individual (non-aggregated) nanoparticles because this is a key problem in nanotechnology industrialization. Controlling the mixing between so two dissimilar phases is a critical challenge in the design of these inorganic-organic systems. Several approaches that may be applied to overcome this problem will be described in this review.

Support for the initial attachment, growth and differentiation of MG-63 cells: a comparison between nano-size hydroxyapatite and micro-size hydroxyapatite in composites

Hydroxyapatite (HA) is considered to be a bioactive material that favorably influences the adhesion, growth, and osteogenic differentiation of osteoblasts. To optimize the cell response on the hydroxyapatite composite, it is desirable to assess the optimum concentration and also the optimum particle size. The aim of our study was to prepare composite materials made of polydimethylsiloxane, polyamide, and nano-sized (N) or micro-sized (M) HA, with an HA content of 0%, 2%, 5%, 10%, 15%, 20%, 25% (v/v) (referred to as N0–N25 or M0–M25), and to evaluate them in vitro in cultures with human osteoblast-like MG-63 cells. For clinical applications, fast osseointegration of the implant into the bone is essential. We observed the greatest initial cell adhesion on composites M10 and N5. Nano-sized HA supported cell growth, especially during the first 3 days of culture. On composites with micro-size HA (2%–15%), MG-63 cells reached the highest densities on day 7. Samples M20 and M25, however, were toxic for MG-63 cells, although these composites supported the production of osteocalcin in these cells. On N2, a higher concentration of osteopontin was found in MG-63 cells. For biomedical applications, the concentration range of 5%–15% (v/v) nano-size or micro-size HA seems to be optimum.

Dry versus hydrated collagen scaffolds: are dry states representative of hydrated states?

AbstractCollagen composite scaffolds have been used for a number of studies in tissue engineering. The hydration of such highly porous and hydrophilic structures may influence mechanical behaviour and porosity due to swelling. The differences in physical properties following hydration would represent a significant limiting factor for the seeding, growth and differentiation of cells in vitro and the overall applicability of such hydrophilic materials in vivo. Scaffolds based on collagen matrix, poly(DL-lactide) nanofibers, calcium phosphate particles and sodium hyaluronate with 8 different material compositions were characterised in the dry and hydrated states using X-ray microcomputed tomography, compression tests, hydraulic permeability measurement, degradation tests and infrared spectrometry. Hydration, simulating the conditions of cell seeding and cultivation up to 48 h and 576 h, was found to exert a minor effect on the morphological parameters and permeability. Conversely, hydration had a major statistically significant effect on the mechanical behaviour of all the tested scaffolds. The elastic modulus and compressive strength of all the scaffolds decreased by ~95%. The quantitative results provided confirm the importance of analysing scaffolds in the hydrated rather than the dry state since the former more precisely simulates the real environment for which such materials are designed.

The release kinetics, antimicrobial activity and cytocompatibility of differently prepared collagen/hydroxyapatite/vancomycin layers: Microstructure vs. nanostructure

&NA; The aim of this study was to develop an osteo‐inductive resorbable layer allowing the controlled elution of antibiotics to be used as a bone/implant bioactive interface particularly in the case of prosthetic joint infections, or as a preventative procedure with respect to primary joint replacement at a potentially infected site. An evaluation was performed of the vancomycin release kinetics, antimicrobial efficiency and cytocompatibility of collagen/hydroxyapatite layers containing vancomycin prepared employing different hydroxyapatite concentrations. Collagen layers with various levels of porosity and structure were prepared using three different methods: by means of the lyophilisation and electrospinning of dispersions with 0, 5 and 15 wt% of hydroxyapatite and 10 wt% of vancomycin, and by means of the electrospinning of dispersions with 0, 5 and 15 wt% of hydroxyapatite followed by impregnation with 10 wt% of vancomycin. The maximum concentration of the released active form of vancomycin characterised by means of HPLC was achieved via the vancomycin impregnation of the electrospun layers, whereas the lowest concentration was determined for those layers electrospun directly from a collagen solution containing vancomycin. Agar diffusion testing revealed that the electrospun impregnated layers exhibited the highest level of activity. It was determined that modification using hydroxyapatite exerts no strong effect on vancomycin evolution. All the tested samples exhibited sufficient cytocompatibility with no indication of cytotoxic effects using human osteoblastic cells in direct contact with the layers or in 24‐hour infusions thereof. The results herein suggest that nano‐structured collagen‐hydroxyapatite layers impregnated with vancomycin following cross‐linking provide suitable candidates for use as local drug delivery carriers. Graphical abstract Figure. No caption available.

Filamentous Carbon Catalytic Deposition of Coal‐Tar Pitch Fraction on Corundum

Abstract Our work was focused on deposition of volatile hydrocarbons of carbonaceous precursor on corundum wafer, taking advantage of a metallic catalyst incorporated in precursor. Coal tar‐pitch, namely a fraction soluble in toluene, served as precursor material for deposition of filamentous material. The toluene‐soluble fraction of tar‐pitch originally contained metallic particles of iron and nickel. During heat treatment up to 1000°C, metallic particles accompanied the volatile hydrocarbons conducive to forming a filamentous deposit. The deposit obtained demonstrates a semicrystalline material that has an irregular filamentous structure with an average filament diameter of 30 µm. The presence of catalysts after the deposition process was proved in the deposit but catalysts were not found in the residuum.

Comparison of Nanofiber and Particle Form of GELATINE/HA Biocomposites

This report is about composites used for bone grafting. Targets the composites compact of organic chemical compounds (biopolymers) and anorganic chemical compounds (nanoparticles). These composites must be, among others, biocompatible, nontoxic for organism and their mechanical properties must be near to mechanical properties of bone. This report focused on biodegradable composites based on gelatine and nanopowder of hydroxyapatite in nanofiber and particle form.