AIM: The primary aim of this study is to evaluate the repeatability of noninvasive break-up time (NIBUT) measurement by keratograph when it is determined from one, two or three partial measurements, and to recommend a suitable methodology for practice. Another goal is to verify that repeated measurements do not affect the measured value. MATERIAL AND METHODS: Thirty-eight healthy volunteers (30 women and 8 men) aged between 19 and 50 years old were included in the study, in which only one eye of each volunteer was measured. The study was designed as a prospective one. Each subject adapted to the local conditions of the laboratory for 15 minutes and subsequently underwent two series of NIBUT measurements (test, retest) on an OCULUS 3 Keratograph. The minimum time interval between the two series was 10 minutes, in which each series contained three partial measurements approximately 3 three measurements in the given series. Repeatability was assessed by a Bland-Altman analysis and expressed as a repeatability coefficient. In every case, only the time of the first break-up of the tear film was monitored. RESULTS: The statistical analysis did not show statistically significant differences both between partial measurements of NIBUT in the individual series (p = 0.92, p = 0.81) and when comparing all six measurements (p = 0.95). The mean values of the partial measurements ranged from 13.6 s to 14.4 s. The repeatability coefficients were found to be 15.0 s, 12.1 s and 10.0 s for methodologies A, B and C, respectively. A supplementary analysis for 12 eyes with low NIBUT (< 10 s) showed statistically significantly better repeatability in this group, with coefficients of 7.0 s (methodology A), 6.0 s (B) and 4.6 s (C). CONCLUSION: Determination of NIBUT from three consecutive measurements (with a sufficient interval of ideally a few minutes) significantly improves repeatability. Such repeated NIBUT measurements do not have a significant effect on the measured value. The mentioned methodology for measuring NIBUT on a keratograph can be recommended for use in practice.
- Klíčová slova
- BUT, NIBUT, break-up time test, dry eye syndrome, repeatability of measurement, tear film,
- MeSH
- diagnostické techniky oftalmologické přístrojové vybavení MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladý dospělý MeSH
- prospektivní studie MeSH
- reprodukovatelnost výsledků MeSH
- rohovka diagnostické zobrazování MeSH
- slzy * chemie MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
The use of polymers for water storage or distribution is closely monitored, especially with regard to the possible contamination with substances coming from the material's surfaces. Different standards are practiced across countries according to type of applied materials and such test methods are prevalently based on constant temperature conditions. However, these polymers systems could be located in diverse environment which does not necessarily provide constant conditions. Experimental findings show that exposure of liquid inside polymeric materials to specific temperature gradients, and consequently to emerging organized flows, can result in an accelerated leaching of undesirable substances from the solid surface. In presented work model steady-state and organized flow conditions are used to compare release of contaminates from polyethylene by measuring of surface tension, UV-Vis spectroscopy, FTIR, scanning electron microscopy and elemental analysis of polymer surfaces and water leachates. The pilot study shows that convective flow generated via temperature gradient significantly affects contaminant release in comparison to a steady state and mixing flow conditions.
- Klíčová slova
- Contaminant, Organized fluid flow, Release, Temperature gradient,
- Publikační typ
- časopisecké články MeSH
This work explores application of phase separation phenomena for structuring of films made from hyaluronan. A time-sequenced dispensing of different solution mixtures was applied under rotation of hyaluronan-covered substrates to generate surface textures. This method is applicable in direct surface modification or cover layer deposition. Changes in the surface topography were characterized by atomic force microscopy, optical microscopy, and contact and non-contact profilometry. The mechanical properties of the surface-modified self-supporting films were compared using a universal testing machine. Experimental results show that diverse hyaluronan-based surface reliefs and self-supporting films with improved mechanical properties can be prepared using a newly designed multi-step phase separation process without the need for sacrificial removable templates or additives.
- Publikační typ
- časopisecké články MeSH
Layered nanoparticles with surface charge are explored as rheological modifiers for extrudable materials, utilizing their ability to induce electrostatic repulsion and create a house-of-cards structure. These nanoparticles provide mechanical support to the polymer matrix, resulting in increased viscosity and storage modulus. Moreover, their advantageous aspect ratio allows for shear-induced orientation and decreased viscosity during flow. In this work, we present a synthesis and liquid-based exfoliation procedure of phenylphosphonate-phosphate particles with enhanced ability to be intercalated by hydrophilic polymers. These layered nanoparticles are then tested as rheological modifiers of sodium alginate. The effective rheological modification is proved as the viscosity increases from 101 up to 103 Pa·s in steady state. Also, shear-thinning behavior is observed. The resulting nanocomposite hydrogels show potential as an extrudable bioink for 3D printing in tissue engineering and other biomedical applications, with good shape fidelity, nontoxicity, and satisfactory cell viability confirmed through encapsulation and printing of mouse fibroblasts.
- MeSH
- 3D tisk MeSH
- algináty chemie MeSH
- bioprinting * metody MeSH
- hydrogely farmakologie chemie MeSH
- myši MeSH
- organofosfonáty * MeSH
- polymery MeSH
- reologie MeSH
- tkáňové inženýrství metody MeSH
- tkáňové podpůrné struktury chemie MeSH
- vápník MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- algináty MeSH
- hydrogely MeSH
- organofosfonáty * MeSH
- polymery MeSH
- vápník MeSH
Knowledge of mass transport parameters, diffusion, and viscosity of hyaluronic acid (HA) in the presence of cyclodextrins is of considerable importance for areas such as food packaging and drug delivery, among others. Despite a number of studies investigating the functionalization of HA or the corresponding sodium salt by cyclodextrins, only a few studies have reported the effect of cyclodextrins on the mass transport of HA in the presence of these oligosaccharides. Here, we report the tracer binary and ternary interdiffusion coefficients of sodium hyaluronate (NaHy) in water and aqueous β-cyclodextrin solutions. The diffusion behavior of sodium hyaluronate was dependent on the reduced viscosity of NaHy, which, in turn, presented a concave dependence on concentration, with a minimum at approximately 2.5 g dm-3. The significant decrease in the limiting diffusion coefficient of NaHy (at most 45%) at NaHy concentrations below 1 g dm-3 in the presence of β-cyclodextrin, taking water as the reference, allowed us to conclude that NaHy strongly interacted with the cyclodextrin.
- Klíčová slova
- diffusion, diffusion coefficients, salting-in, sodium hyaluronate, transport properties, viscosity, β-cyclodextrin,
- MeSH
- beta-cyklodextriny * MeSH
- cyklodextriny * MeSH
- difuze MeSH
- kyselina hyaluronová MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- beta-cyklodextriny * MeSH
- cyklodextriny * MeSH
- kyselina hyaluronová MeSH
- voda MeSH
Smart hydrogels based on natural polymers present an opportunity to fabricate responsive scaffolds that provide an immediate and reversible reaction to a given stimulus. Modulation of mechanical characteristics is especially interesting in myocyte cultivation, and can be achieved by magnetically controlled stiffening. Here, hyaluronan hydrogels with carbonyl iron particles as a magnetic filler are prepared in a low-toxicity process. Desired mechanical behaviour is achieved using a combination of two cross-linking routes-dynamic Schiff base linkages and ionic cross-linking. We found that gelation time is greatly affected by polymer chain conformation. This factor can surpass the influence of the number of reactive sites, shortening gelation from 5 h to 20 min. Ionic cross-linking efficiency increased with the number of carboxyl groups and led to the storage modulus reaching 103 Pa compared to 101 Pa-102 Pa for gels cross-linked with only Schiff bases. Furthermore, the ability of magnetic particles to induce significant stiffening of the hydrogel through the magnetorheological effect is confirmed, as a 103-times higher storage modulus is achieved in an external magnetic field of 842 kA·m-1. Finally, cytotoxicity testing confirms the ability to produce hydrogels that provide over 75% relative cell viability. Therefore, dual cross-linked hyaluronan-based magneto-responsive hydrogels present a potential material for on-demand mechanically tunable scaffolds usable in myocyte cultivation.
- Klíčová slova
- Schiff base, hyaluronan, hydrodynamic radius, magnetorheology, smart hydrogels, tissue engineering,
- MeSH
- hydrogely * chemie MeSH
- kyselina hyaluronová * MeSH
- polymery MeSH
- polysacharidy MeSH
- reologie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- hydrogely * MeSH
- kyselina hyaluronová * MeSH
- polymery MeSH
- polysacharidy MeSH
Bio-inspired conductive scaffolds composed of sodium hyaluronate containing a colloidal dispersion of water-miscible polyaniline or polypyrrole particles (concentrations of 0.108, 0.054 and 0.036% w/w) were manufactured. For this purpose, either crosslinking with N-(3-dimethylaminopropyl-N-ethylcarbodiimide hydrochloride and N-hydroxysuccinimid or a freeze-thawing process in the presence of poly(vinylalcohol) was used. The scaffolds comprised interconnected pores with prevailing porosity values of ~ 30% and pore sizes enabling the accommodation of cells. A swelling capacity of 92-97% without any sign of disintegration was typical for all samples. The elasticity modulus depended on the composition of the scaffolds, with the highest value of ~ 50 kPa obtained for the sample containing the highest content of polypyrrole particles. The scaffolds did not possess cytotoxicity and allowed cell adhesion and growth on the surface. Using the in vivo-mimicking conditions in a bioreactor, cells were also able to grow into the structure of the scaffolds. The technique of scaffold preparation used here thus overcomes the limitations of conductive polymers (e.g. poor solubility in an aqueous environment, and limited miscibility with other hydrophilic polymer matrices) and moreover leads to the preparation of cytocompatible scaffolds with potentially cell-instructive properties, which may be of advantage in the healing of damaged electro-sensitive tissues.
- MeSH
- biokompatibilní materiály chemie MeSH
- kyselina hyaluronová MeSH
- polymery * chemie MeSH
- poréznost MeSH
- pyrroly chemie MeSH
- tkáňové inženýrství * metody MeSH
- tkáňové podpůrné struktury chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- biokompatibilní materiály MeSH
- kyselina hyaluronová MeSH
- polymery * MeSH
- pyrroly MeSH
The pseudo 3D hierarchical structure mimicking in vivo microenvironment was prepared by phase separation on tissue culture plastic. For surface treatment, time-sequenced dosing of the solvent mixture with various concentrations of polymer component was used. The experiments showed that hierarchically structured surfaces with macro, meso and micro pores can be prepared with multi-step phase separation processes. Changes in polystyrene surface topography were characterized by atomic force microscopy, scanning electron microscopy and contact profilometry. The cell proliferation and changes in cell morphology were tested on the prepared structured surfaces. Four types of cell lines were used for the determination of impact of the 3D architecture on the cell behavior, namely the mouse embryonic fibroblast, human lung carcinoma, primary human keratinocyte and mouse embryonic stem cells. The increase of proliferation of embryonic stem cells and mouse fibroblasts was the most remarkable. Moreover, the embryonic stem cells express different morphology when cultured on the structured surface. The acquired findings expand the current state of knowledge in the field of cell behavior on structured surfaces and bring new technological procedures leading to their preparation without the use of problematic temporary templates or additives.
- Klíčová slova
- foams, hierarchically structured, line-specific response, phase inversion, phase separations, stem cells, surfaces,
- MeSH
- fibroblasty * MeSH
- mikroskopie atomárních sil MeSH
- mikroskopie elektronová rastrovací MeSH
- myši MeSH
- polymery * chemie MeSH
- povrchové vlastnosti MeSH
- proliferace buněk MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- polymery * MeSH
Essential features of well-designed materials intended for 3D bioprinting via microextrusion are the appropriate rheological behavior and cell-friendly environment. Despite the rapid development, few materials are utilizable as bioinks. The aim of our work was to design a novel cytocompatible material facilitating extrusion-based 3D printing while maintaining a relatively simple and straightforward preparation process without the need for harsh chemicals or radiation. Specifically, hydrogels were prepared from gelatines coming from three sources-bovine, rabbit, and chicken-cross-linked by dextran polyaldehyde. The influence of dextran concentration on the properties of hydrogels was studied. Rheological measurements not only confirmed the strong shear-thinning behavior of prepared inks but were also used for capturing cross-linking reaction kinetics and demonstrated quick achievement of gelation point (in most cases < 3 min). Their viscoelastic properties allowed satisfactory extrusion, forming a self-supported multi-layered uniformly porous structure. All gelatin-based hydrogels were non-cytototoxic. Homogeneous cells distribution within the printed scaffold was confirmed by fluorescence confocal microscopy. In addition, no disruption of cells structure was observed. The results demonstrate the great potential of the presented hydrogels for applications related to 3D bioprinting.
- Klíčová slova
- 3D printing, microextrusion, cell distribution, gelatine-dextran, hydrogel, rheology,
- Publikační typ
- časopisecké články MeSH
A combination of mechanical and chemical treatments was utilized to modify the surface textures of copper and duralumin inserts in order to enhance the adhesion at the metal-polymer interface and provide an adhesive joint with a high loadbearing capacity. Pretreatment of the surfaces with sandblasting was followed by etching with various chemical mixtures. The resulting surface textures were evaluated with a scanning electron microscope (SEM) and an optical confocal microscope. Surface geometry parameters (Sa, Sz, and Sdr) were measured and their relationships to the adhesion joint strength were studied. It was found that the virgin and purely mechanically treated inserts resulted in joints with poor loadbearing capacity, while a hundredfold (duralumin) and ninetyfold (copper) increase in the force to break was observed for some combinations of mechanical and chemical treatments. It was determined that the critical factor is overcoming a certain surface roughness threshold with the mechanical pretreatment to maximize the potential of the mechanical/chemical approach for the particular combination of material and etchant.
