Ondrej Kaspar

Ondrej Kaspar
University of Chemistry and Technology, Prague | VSCHT

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41
Publications
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626
Citations

Publications

Publications (41)
Article
Full-text available
Although allicin has potent antibiotic properties, its low stability, which is responsible for its persistent biological activity, has posed a significant challenge to its practical application in modern medicine. To harness the healing benefits of this phytochemical, known by humans for thousands of years, we propose a controlled in situ synthesis...
Article
Full-text available
Since the outbreak of the COVID-19 pandemic, the use of hand sanitisers has become an inseparable part of our personal hygiene. However, the short-term effect and the need for frequent application are shortcomings that impair the overall protection. Another aspect is that repeated use of some products (typically alcohol-based) may cause skin irrita...
Article
Spray drying is commonly used for producing amorphous solid dispersions to improve drug solubility. The development of such formulations typically relies on comprehensive excipient and composition screening, which requires the preparation of many spray-dried powder samples. This is both labour-intensive and time-consuming when carried out manually....
Patent
The present invention relates to a method for the fast and highly efficient production of multi-component powders by spray drying. The method can be applied to already existing small-scale spray dryers available in the market and enables the production of multiple samples with variable composition in continuous mode. The present invention further r...
Article
Full-text available
Non-deterministic polynomial (NP-) complete problems, whose number of possible solutions grows exponentially with the number of variables, require by necessity massively parallel computation. Because sequential computers, such as solid state-based ones, can solve only small instances of these problems within a reasonable time frame, parallel comput...
Article
Allicin, an organic compound produced via the transformation of biologically inactive alliin by alliinase, an enzyme found in garlic, combines a strong antibacterial effect with suppressed development of bacterial resistance. However, because of the high reactivity and volatility, controlled in-situ production of allicin that mimics the natural syn...
Article
Full-text available
Significance Understanding bacterial movement is crucial for health, agriculture, environment, and industry. Studying the motility of five bacterial species in microfluidic environments showed that bacterial motility behavior is the result of a “tug-of-war” between hydrodynamics and local nanomechanics. In less confining spaces, bacterial motility...
Article
Full-text available
Multiphase flows are a part of many industrial processes, where the bubble motion influences the hydrodynamic behavior of the batch. The current trend is to use numerical solvers that can simulate the movement and mutual interactions of bubbles. The aim of this work was to study how two commercial CFD solvers, COMSOL Multiphysics and Ansys Fluent,...
Article
Full-text available
Garlic is a well-known example of natural self-defence system consisting of an inactive substrate (alliin) and enzyme (alliinase) which, when combined, produce highly antimicrobial allicin. Increase of alliinase stability and its activity are of paramount importance in various applications relying on its use for in-situ synthesis of allicin or its...
Article
Microfluidics allows to accurately control the synthesis of microparticles for specific applications, where size and morphology play an important role. In this work, we introduce microfluidic chip design with dedicated extraction and gelation sections allowing to prepare hydrogel particles in size range of a red blood cell. The influence of the ext...
Article
Full-text available
Microfluidic devices, allowing superior control over the spatial and temporal distribution of chemical substances and high process reproducibility, are nowadays essential in various research areas and industrial fields where the traditional “macroscopic” approach was no longer able to keep up with the increasing demands of high-end applications. In...
Article
Full-text available
Droplet-based microfluidic devices are now more than ever used for the synthesis of nanoparticles with low polydispersity and well-defined properties suitable for various industrial applications. Very small reaction volumes (microlitre to femtolitre) and short diffusion lengths, provide superior mixing efficiency and heat transport. Both play the d...
Chapter
Many bacteria dwell in micro-habitats, e.g., animal or plant tissues, waste matter, and soil. Consequently, bacterial space searching and partitioning is critical to their survival. However, the vast majority of studies regarding the motility of bacteria have been performed in open environments. To fill this gap in knowledge, we studied the behavio...
Article
Full-text available
Significance Many filamentous fungi colonizing animal or plant tissue, waste matter, or soil must find optimal paths through the constraining geometries of their microenvironment. Imaging of live fungal growth in custom-built microfluidics structures revealed the intracellular mechanisms responsible for this remarkable efficiency. In meandering cha...
Article
Full-text available
One contribution of 10 to a theme issue 'Computation by natural systems'. On-chip network-based computation, using biological agents, is a new hardware embedded approach which attempts to find solutions to combinatorial problems, in principle, in a shorter time than the fast, but sequential electronic computers. This analytical review starts by des...
Preprint
Full-text available
The underlying intracellular mechanisms involved in the fungal growth received considerable attention, but the experimental and theoretical work did not take into account the modulation of these processes by constraining microenvironments similar to many natural fungal habitats. To fill this gap in the scientific knowledge, we used time-lapse live-...
Article
Silica particles with a unique multi-level pore structure have been prepared in order to enable efficient melt-in amorphisation of pharmaceutical substances. The dissolution rate of drugs with a low aqueous solubility can be enhanced by their conversion from a crystalline to an amorphous form. In order to avoid spontaneous re-crystallisation over t...
Article
Despite the wide application interest in mesoporous silica micro- and nano-particles and a number of synthesis routes reported in the literature, the question of chemical engineering scale-up of the synthetic routes has rarely been addressed. The present work reports the results of an experimental and computational study of batch scale-up by a fact...
Article
The actin-myosin system, responsible for muscle contraction, is also the force-generating element in dynamic nanodevices operating with surface-immobilized motor proteins. These devices require materials that are amenable to micro- and nano-fabrication, but also preserve the bioactivity of molecular motors. The complexity of the protein-surface sys...
Article
Micro-patterned surfaces with alternate, hydrophilic, and hydrophobic rectangular areas, effectively confine water droplets down to attolitre volumes. The contact angle, volume, and geometry of the confined droplets as a function of the geometry and physico-chemical properties of the confining surfaces have been determined by phenomenological simul...
Article
Full-text available
Micro-contact printing, μCP, is a well-established soft-lithography technique for printing biomolecules. μCP uses stamps made of Poly(dimethylsiloxane), PDMS, made by replicating a microstructured silicon master fabricated by semiconductor manufacturing processes. One of the problems of the μCP is the difficult control of the printing process, whic...
Article
This work focuses on the content non-homogeneity in granules across size classes in a high shear wet granulation process as a result of powder segregation during dry mixing coupled with preferential wettability of one of the ingredients with the binder fluid.A two component API-excipient system comprised of acetaminophen (APAP) and microcrystalline...
Article
The objective of the current work was to investigate the effect of liquid to solid ratio (L/S), impeller speed and the wet massing time on the critical quality attributes of granules in a high shear wet granulation process for a two component (API and excipient) system. The parameters were evaluated for their effect on granule properties using a de...
Article
The X-ray micro-tomography (micro-CT) technique has been used to visualize the microstructure of granules produced by high shear wet granulation and the dynamic evolution of porosity during granule dissolution. Using acetaminophen (paracetamol) as the active pharmaceutical ingredient (API) and microcrystalline cellulose (Avicel PH-200) as an excipi...
Conference Paper
A mechanistic understanding of the correlation between the properties of the primary powder and granules can lead to enhanced and efficient process development in tablet manufacturing via high-shear wet granulation (HSWG), which is currently the most common route undertaken. Moreover, Quality-by-Design (QbD) in pharmaceutical manufacturing desires...
Article
The effect of processing method on the properties of cross-linked chitosan microparticles and on the enzymatic activity of laccase immobilized in the particles has been investigated. Chitosan has been cross-linked by tri-polyphosphate (TPP) using two methods – the so called ex situ cross-linking whereby the solutions of chitosan, TPP and the enzyme...
Article
Chitosan microparticles cross-linked by tri-polyphosphate (TPP) anions have been prepared by spray drying. Two different cross-linking methods have been employed — ex-situ cross-linking whereby aqueous solution of cross-linked chitosan nanoparticles has been spray-dried by a two-fluid nozzle, and a novel in-situ cross-linking method, whereby soluti...
Article
The design of chitosan microspheres for the encapsulation and release of nanoparticles has been considered. The composite microcarriers have been produced by spray drying and the effect of factors including the chitosan cross-linking ratio (using tri-polyphosphate as the cross-linking agent), nanoparticle loading in the polymer matrix and the inter...

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