Homogeneous films from amphiphilic hyaluronan and their characterization by confocal microscopy and nanoindentation.

Self-supporting films from amphiphilic hyaluronan are suitable for medical applications like wound dressings or resorbable implants. These films are typically cast from water/alcohol solutions. However, when the mixed solvent evaporates in ambient air, convection flows develop in the solution and become imprinted in the film, potentially compromising its properties. Consequently, we developed a novel film manufacturing method: drying in a closed box under saturated vapour conditions. Using this approach, we prepared a series of optically clear lauroyl-hyaluronan (LHA) films with uniform thickness and compared them to their air-dried counterparts. We first evaluated swelling ratios and elastic moduli for LHA films with varying degrees of substitution. The box-dried films swelled significantly less and were 1-2 orders of magnitude stiffer than air-dried films from the same LHA sample. Confocal microscopy revealed that box-dried films exhibited a regular microstructure, while air-dried films displayed a pore-size gradient and strong microstructure modulation due to convection flows. Local elastic modulus variations arising from these microstructures were assessed using nanoindentation mapping. Importantly, achieving the desired film stiffness requires much lower polymer modification when box-drying is used, enhancing the biological response to the material. These findings have implications for all polysaccharide formulations that utilize mixed solvents.

Enhancing Dental Applications: A Novel Approach for Incorporating Bioactive Substances into Textile Threads.

In the realm of surgical and dental applications, hyaluronic acid (HA) braided threads show significant therapeutic potential due to their incorporation of pharmaceutical active ingredients. This study primarily focuses on resolving the crucial challenge of devising a deposition method that can ensure both precision and uniformity in the content of the active ingredient Octenidine dihydrochloride (OCT) within each segment of the threads. Our objective in this study was to develop a continuous deposition method for OCT onto a braided thread composed of 24 hyaluronic acid-based fibers, aiming for a specific OCT content of 0.125 µg/mm, while maintaining a maximum allowable deviation of ±15% in OCT content. The motivation behind designing this novel method stemmed from the necessity of employing a volatile solvent for the active agent. Conventional wetting methods proved unsuitable due to fluctuations in the solution's concentration during deposition, and alternative methods known to us demanded intricate technical implementations. The newly introduced method offers distinct advantages, including its online processing speed, scalability potential, and cost-efficiency of the active agent solution. Additionally, it minimizes the impact on the natural polymer thread, preserving energy by obviating the need for complete thread saturation. Our research and precise apparatus development resulted in achieving the desired thread properties, with an OCT content of (1.51 ± 0.09) µg per 12 mm thread piece. These findings not only validate the suitability of this innovative method for depositing active agents but also extend its potential applicability beyond dental care.

HIV-positive Ukrainian refugees in the Czech Republic.

OBJECTIVE: Over 480 000 Ukrainian refugees have arrived in the Czech Republic since the Russian invasion of Ukraine in 2022, including over 500 people with HIV. This study describes the demographics, characteristics, and management of Ukrainian refugees with HIV in the Czech Republic. DESIGN: Retrospective, observational, noninterventional study. METHODS: Ukrainian nationals registering at HIV centers in the Czech Republic with war refugee status were included. Data were collected from medical records between 1 March and 31 July 2022. The study was registered with the Czech State Institute for Drug Control, ID number 2301200000. RESULTS: Four hundred and eighty-two patients were included in the study. Most patients were female (69.5%; n  = 335/482) with well-controlled HIV. The median [interquartile range] CD4 + cell count was 597 [397] cells/µl of blood, and 79.3% ( n  = 361/455) of patients had HIV RNA <40 copies/ml. Coinfections of hepatitis C virus, hepatitis B virus, and/or tuberculosis were reported for 17.4% ( n  = 78/449), 9% ( n  = 40/446) and 1.3% ( n  = 6/446) of patients, respectively. In Ukraine, 85.7% ( n  = 384/448) of patients had been receiving an integrase strand transfer inhibitor-based regimen and most (69.7%; n  = 310/445) did not switch therapy upon arrival in the Czech Republic. CONCLUSION: Migration from Ukraine is changing the characteristics of HIV epidemiology in the Czech Republic. Ukrainian refugees with HIV have been provided with a high standard of medical care in the Czech Republic. Improved coordination between medical services within the Czech Republic and between countries in the European Union is necessary to optimize patient care.

Intraperitoneally administered native and lauroyl-modified hyaluronan films: Pharmacokinetic and metabolism studies.

Hyaluronan is being investigated extensively as a biocompatible and biodegradable material for use in biomedical applications. While the derivatization of hyaluronan broadens its potential therapeutic use, the pharmacokinetics and metabolization of the derivatives must be thoroughly investigated. The fate of intraperitoneally-applied native and lauroyl-modified hyaluronan films with varying degrees of substitution was investigated in-vivo employing an exclusive stable isotope-labelling approach and LC-MS analysis. The materials were gradually degraded in peritoneal fluid, lymphatically absorbed, preferentially metabolized in the liver and eliminated without any observable accumulation in the body. Hyaluronan acylation prolongs its presence in the peritoneal cavity depending on the degree of substitution. The safety of acylated hyaluronan derivatives was confirmed via a metabolic study that revealed its degradation into non-toxic metabolites, i.e. native hyaluronan and free fatty acid. Stable isotope-labelling with LC-MS tracking comprises a high-quality procedure for the investigation of the metabolism and biodegradability of hyaluronan-based medical products in-vivo.

An in vitro model that mimics the foreign body response in the peritoneum: Study of the bioadhesive properties of HA-based materials.

A cascade of reactions known as the foreign body response (FBR) follows the implantation of biomaterials leading to the formation of a fibrotic capsule around the implant and subsequent health complications. The severity of the FBR is driven mostly by the physicochemical characteristics of implanted material, the method and place of implantation, and the degree of immune system activation. Here we present an in vitro model for assessing new materials with respect to their potential to induce a FBR in the peritoneum. The model is based on evaluating protein sorption and cell adhesion on the implanted material. We tested our model on the free-standing films prepared from hyaluronan derivatives with different hydrophobicity, swelling ratio, and rate of solubilization. The proteomic analysis of films incubated in the mouse peritoneum showed that the presence of fibrinogen was driving the cell adhesion. Neither the film surface hydrophobicity/hydrophilicity nor the quantity of adsorbed proteins were decisive for the induction of the long-term cell adhesion leading to the FBR, while the dissolution rate of the material proved to be a crucial factor. Our model thus helps determine the probability of a FBR to materials implanted in the peritoneum while limiting the need for in vivo animal testing.

Water-insoluble fibres, threads, and fabrics from lauroyl derivatives of hyaluronan.

Hyaluronan (HA) is a naturally occurring polysaccharide widely used in medicine and cosmetics. To further broaden its potential, various HA derivatives have been developed with the aim of reducing solubility, slowing degradation, or providing other beneficial properties. However, for most medical applications, these derivatives must be processed into suitable forms. Here we present water-insoluble fibres prepared from lauroyl-modified HA using a wet spinning process. Important properties of the fibres, such as swelling or the degradation rate, can be fine-tuned by adjusting the degree of HA modification. Due to their mechanical properties, the lauroyl HA fibres can be easily processed into threads and subsequently into fabrics of various sizes, shapes, and degrees of porosity. In addition, in vitro cytotoxicity testing of the fibres showed that they were non-cytotoxic. Overall, our results suggest that lauroyl HA fibres are a promising material that could be used to develop a variety of medical devices.

Lauroyl hyaluronan films for local drug delivery: Preparation and factors influencing the release of small molecules.

Lauroyl derivatives of hyaluronan are safe and biodegradable materials that seem promising for application in medicine. However, their potential in the field of drug delivery was not yet explored. We thus prepared lauroyl hyaluronan films loaded with various drugs and studied the effects of lauroyl hyaluronan properties, drug hydrophobicity and medium composition on the drug release. Since biomolecules will always be present in real clinical applications, media supplemented by albumin were also included. The amphiphilic character of lauroyl hyaluronan enabled convenient loading of the films by both hydrophilic and hydrophobic drugs. Dominant factors influencing drug release were drug hydrophobicity and the presence of albumin. Hydrophilic diclofenac was released rapidly in all cases, while triclosan with medium hydrophobicity exhibited slower release sensitive to other parameters, reaching equilibrium values in the used experimental setup. The release of hydrophobic octenidine into pure buffer was almost negligible, but the addition of albumin did promote its release. The strong effect of albumin highlights the importance of considering biomolecules in the design of release experiments.

Insoluble hyaluronan films obtained by heterogeneous crosslinking with iron(III) as resorbable implants.

We present water-insoluble hyaluronan films crosslinked by trivalent iron developed as potential resorbable implants. The films were crosslinked by sorption of ferric salt into solid HA films in water/2-propanol bath. These heterogeneously crosslinked films (het-FeHA) remained tough and dimensionally stable when rehydrated in saline. In contrast, films prepared by drying the well-known homogeneous ferric hyaluronate gels (hom-FeHA) softened upon rehydration and expanded rapidly. Differences between hom-FeHA and het-FeHA result from polymer network topology (dominant inter- or intra-molecular crosslink, respectively). Moreover, Mössbauer spectroscopy of het-FeHA revealed diiron complexes, while iron in the hom-FeHA was present exclusively as γ-FeOOH nanoparticles or amorphous FeOOH. The biocompatibility tests of het-FeHA did not show any adverse effect and the sample disintegrated within one day when implanted in mice peritoneum. In conclusion, we developed implantable hyaluronan-based free-standing film with minimal swelling that can be resorbed quickly enough to avoid induction of foreign-body reaction.

Nonwoven Textiles from Hyaluronan for Wound Healing Applications.

Nonwoven textiles are used extensively in the field of medicine, including wound healing, but these textiles are mostly from conventional nondegradable materials, e.g., cotton or synthetic polymers such as polypropylene. Therefore, we aimed to develop nonwoven textiles from hyaluronan (HA), a biocompatible, biodegradable and nontoxic polysaccharide naturally present in the human body. For this purpose, we used a process based on wet spinning HA into a nonstationary coagulation bath combined with the wet-laid textile technology. The obtained HA nonwoven textiles are soft, flexible and paper like. Their mechanical properties, handling and hydration depend on the microscale fibre structure, which is tuneable by selected process parameters. Cell viability testing on two relevant cell lines (3T3, HaCaT) demonstrated that the textiles are not cytotoxic, while the monocyte activation test ruled out pyrogenicity. Biocompatibility, biodegradability and their high capacity for moisture absorption make HA nonwoven textiles a promising material for applications in the field of wound healing, both for topical and internal use. The beneficial effect of HA in the process of wound healing is well known and the form of a nonwoven textile should enable convenient handling and application to various types of wounds.

Biodegradable free-standing films from lauroyl derivatives of hyaluronan.

Hyaluronan (HA) films exhibit properties suitable for medical applications, but the solubility of HA limits their use in aqueous environments. This can be overcome by modifying HA with hydrophobic side groups that enable physical cross-linking. In this work, we present water insoluble free-standing films from lauroyl modified HA as novel biomaterials with properties tuneable by the degree of HA substitution. The films are homogeneous, mechanically strong, and flexible and can be sterilized by ethylenoxide. To characterize the films, we measured their thickness, dry mass, content of residual organic solvent, mechanical properties, swelling and enzymatic degradation. The safety and biodegradability of the films were tested both in-vitro and in-vivo, showing that the films are safe and that their degradation can be tailored by the degree of HA substitution.

Nanostructure of hyaluronan acyl-derivatives in the solid state.

Acyl derivatives of hyaluronan (acyl-HA) are promising materials for biomedical applications. Depending on the acyl length and the degree of substitution, these derivatives range from self-assembling water-soluble polymers to materials insoluble in aqueous environments. The behaviour of acyl-HA was studied in solution, but little attention was paid to the solid state, despite its importance for applications such as medical device fabrication. We thus used X-ray scattering and electron microscopy to explore the solid-state nano-structure of acyl-HA. The set of samples included various substituents, substitution degrees and molecular weights. The obtained data showed that all studied acyl-HA materials contained structures with dimensions on the order of nanometres that were not present in unmodified HA. The size of the nanostructures increased with the acyl length, while the degree of substitution and molecular weight had negligible effects. We suggest that the observed nanostructure corresponds to a distribution of hydrophobic domains in a hydrophilic matrix of unmodified HA segments.

Water-insoluble thin films from palmitoyl hyaluronan with tunable properties.

Hyaluronan (HA) films exhibit properties suitable for various biomedical applications, but the solubility of HA limits their use in aqueous environments. Therefore, we developed water insoluble films based on palmitoyl esters of HA (pHA). Films were prepared from pHA samples with various degrees of substitution (DS) and molecular weights and their mechanical properties and swelling were characterized. Additionally, scanning electron microscopy and atomic force microscopy were used for visualization. Despite being prepared by solution casting, the films had a very smooth surface and were homogeneous in thickness. The film properties were in accordance with the polymer DS and molecular weight, enabling to tailor them for future applications by choosing a suitable pHA material. The behavior of the films toward cells was assessed in vitro. All films were non-cytotoxic and showed no adhesion of cells. These results show that the developed films are suitable candidates for various biomedical applications such as tissue engineering or wound healing.