Petr Mikes

Elastic three-dimensional poly (ε-caprolactone) nanofibre scaffold enhances migration, proliferation and osteogenic differentiation of mesenchymal stem cells

We prepared 3D poly (ε‐caprolactone) (PCL) nanofibre scaffolds and tested their use for seeding, proliferation, differentiation and migration of mesenchymal stem cell (MSCs).

Photoluminescent materials based on PMMA and a highly-emissive octahedral molybdenum metal cluster complex

Materials that combine photoluminescence, optical transparency and facile processability are of high importance in many applications. This article reports on the development of photoluminescent poly(methyl methacrylate) materials based on novel highly emissive anionic molybdenum cluster complex [{Mo6I8}(OTs)6]2- (where OTs- is the p-toluenesulfonate ion). The materials were obtained by both solution and bulk copolymerisation of methyl methacrylate and (dMDAEMA)2[{Mo6I8}(OTs)6], where dMDAEMA+ is the polymerisable cation [2-(methacryloyloxy)ethyl]dimethyl-dodecylammonium. Evaluation of the resultant hybrid materials showed that one could combine the excellent photoluminescent properties of the cluster complex with the transparency and processability of PMMA.

Design of Polycaprolactone Vascular Grafts

A large number of patients suffer from vascular diseases, resulting in the need for bypass surgery. Since there are still limitations in the replacement of small diameter vascular grafts, the need and demand for developing more desirable grafts is increasing day by day. In this study, polycaprolactone small-diameter (6 mm) vascular grafts were produced successfully using custom-designed electrospinning apparatus. Radial fiber orientation was achieved by increasing the rotational speed of the collector. The morphological, structural, mechanical, and biological properties were examined. The results show that oriented scaffolds with 2 µm average fiber diameter provide 1 MPa ultimate tensile strength in the radial direction. The pore size area was found to be adequate in the oriented samples required for cell proliferation and diffusion through the tunica media. In vitro biocompatibility of the grafts was proven with 3T3 mouse fibroblasts. After cell seeding, the oriented fibers serve as a cue for radial cell alignment. An understanding of electrospun material parameters together with knowledge of native blood vessel structures and properties is a considerable part in designing small-diameter vascular grafts.

Comprehensive assessment of electrospun scaffolds hemocompatibility

Biodegradable polyesters, namely polycaprolactone (PCL) and copolymer of polylactide and polycaprolactone (PLCL) were electrospun into various fibrous structures and their hemocompatibility was evaluated in vitro. Firstly, hemolytic effect was evaluated upon incubation with diluted whole blood. The results showed that the degree of hemolysis depended on chemical composition and fibrous morphology. Electrospun polycaprolactone induced slight degree of hemolysis depending on its molecular weight and fibrous morphology; copolymer PLCL did not cause detectable hemolysis. The influence of coagulation pathways was examined by measurement of coagulation times. It was showed that intrinsic coagulation pathway assessed by activated partial thromboplastin time (APTT) was moderately accelerated after incubation with PCL and prolonged after incubation with copolymer PLCL. Extrinsic activation of coagulation tested by prothrombin time (PT) was slightly accelerated after incubation with all tested electrospun samples. Thrombogenicity assessment of fibrous samples revealed high thrombogenic properties of fibrous materials that was comparable to high degree of collagen thrombogenicity. The level of platelet activation was dependent on chemical composition and surface morphology of tested materials.

Electrospinning jets as X-ray sources at atmospheric conditions

Electrospinning jets producing nanofibres from a polymer solution by electrical forces are fine cylindrical electrodes that create extremely high electric-field strength in their vicinity at atmospheric conditions. However, this quality of electrospinning is only scarcely investigated, and the interactions of the electric fields generated by them with ambient gases are nearly unknown. Here we report on the discovery that electrospinning jets generate X-ray beams up to energies of 20 keV at atmospheric conditions. The X-ray nature of the detected radiation is incontrovertibly proved by a spectroscopic experiment. We hypothesize how the field strength increases to gigantic values in the vicinity of charged electrospinning jets, as a consequence of counterion condensation, to accelerate charged particles, at a short distance, comparable with their mean path at atmospheric pressure, up to kinetic energies that give rise to the detection of X-rays. The experimental set-up designed by us for the generation and detection of high-energy electromagnetic radiation from electrospinning is extremely simple.

The effect of ethylene oxide sterilization on electrospun vascular grafts made from biodegradable polyesters

The study describes the detailed examination of the effect of ethylene oxide sterilization on electrospun scaffolds constructed from biodegradable polyesters. Different fibrous layers fabricated from polycaprolactone (PCL) and a copolymer consisting of polylactide and polycaprolactone (PLCL) were investigated for the determination of their mechanical properties, degradation rates and interaction with fibroblasts. It was discovered that the sterilization procedure influenced the mechanical properties of the electrospun PLCL copolymer scaffold to the greatest extent. No effect of ethylene oxide sterilization on degradation behavior was observed. However, a delayed fibroblast proliferation rate was noticed with concern to the ethylene oxide sterilized samples compared to the ethanol sterilization of the materials.

Nanofibrous Composite Materials Integrating Nano/Micro Particlesbetween the Fibres

This article deals with the continual incorporation of particles by the ultrasonic dispersion in situ into a nanofibrous matrix produced by the electrospinning process. The new technology is based on the use of the needleless electrospinning method in combination with the ultrasound-enhanced dispersion of sub-micro or micro particles, which are deposited between nanofibres onto the support material. The main advantage of this technology is the independence of particle-incorporation of the electrospinning process. The particles are trapped between the fibres and they remain uncovered by polymer, thus maintaining all their active properties. Such materials can be cut with scissors without the particles being released. In this paper the authors present figures from scans of the electron microscopy of the newly-designed nanocomposite material and its morphological analysis, such as the particle distribution. The material was used as a sorbent of bis(2-chlorethyl) sulfide (mustard gas) with a sorption time greater than 240 minutes. Such material has been developed to be used for protection against chemical warfare agents; yet, it can be employed for several other applications depending on the powder material dispersed onto the nanofibrous layer.