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- ItemMultifunctional graphene quantum dots: A therapeutic strategy for neurodegenerative diseases by regulating calcium influx, crossing the blood-brain barrier and inhibiting A-protein aggregation(Elsevier, 2024-02-01) Gomez Perez, Inmaculada Jennifer; Křížková, Petra; Dolečková, Anna; Cardo, Lucia; Wetzl, Cecília; Pizúrová, Naděžda; Prato, Maurizio; Medalová, Jiřina; Zajíčková, LenkaMultifunctional nanoparticles could be the hallmark for the treatment of neurodegenerative diseases. Dissociation of protein aggregates causing neuronal damage and transfer of specific drugs which can downregulate neuronal excitotoxicity by inhibiting glutamatergic N-Methyl-D-Aspartate-receptors (NMDA) and then reducing calcium influx are among the main factors to consider for proper therapy. Here, we present a multiplatform based on nitrogen-doped graphene quantum dots (NGQDs) with such functionalities. The NGQDs were functionalized with Memantine, the clinically used drug, via covalent and non-covalent coupling, and we confirmed that the pharmaceutical activity was not altered. Apart from that, using xCELLigence technology and flow cytometric analysis of ABC transporter function, we uncovered that the ABC transporters of the blood-brain barrier (BBB) do not affect the ability of NGQD to cross BBB. Surprisingly, this study found that NGQDs have an inhibitory effect on NMDA receptors, thus supporting the action of Memantine. Moreover, NGQDs and their derivatives demonstrated the potential to dissociate beta-amyloid aggregates while possessing features suitable for bioimaging in various cell lines.
- ItemSelf-consistent autocorrelation for finite-area bias correction in roughness measurement(IOP Publishing Ltd, 2024-06-01) Nečas, DavidScan line levelling, a ubiquitous and often necessary step in AFM data processing, can cause a severe bias on measured roughness parameters such as mean square roughness or correlation length. Although bias estimates have been formulated, they aimed mainly at assessing the severity of the problem for individual measurements. Practical bias correction methods are still missing. This work exploits the observation that the bias of autocorrelation function (ACF) can be expressed in terms of the function itself, permitting a self-consistent formulation. From this two correction approaches are developed, both with the aim to obtain convenient formulae which can be easily applied in practice. The first modifies standard analytical models of ACF to incorporate, in expectation, the bias and thus actually match the data the models are used to fit. The second inverts the relation between true and estimated ACF to realise a model-free correction. Both are tested using simulated and experimental data and found effective, reducing the total error of roughness parameters several times in the typical cases.
- ItemInsight into peculiar adhesion of cells to plasma-chemically prepared multifunctional "amino-glue" surfaces(Wiley-VCH, 2023-06-01) Janůšová, Martina; Janů, Lucie; Nečas, David; Křížková, Petra; Bartošíková, Jana; Medalová, Jiřina; Kolská, Zdeňka; Hegemann, Dirk; Zajíčková, LenkaPlasma polymers (PPs) can easily modify material surfaces to improve their bio-applicability due to match-made surface-free energy and functionality. However, cell adhesion to PPs typically composed of various functional groups has not yet been fully understood. We explain the origin of strong resistance to trypsin treatment previously noted for nonendothelial cells on amine PPs. It is caused mainly by nonspecific adhesion of negatively charged parts of transmembrane proteins to the positively charged amine PP surface, enabled by thin glycocalyx. However, endothelial cells are bound primarily by their thick, negatively charged glycocalyx and sporadically by integrins in kinetic traps, both cleaved by trypsin. Cell scratching by atomic force microscopy tip confirmed the correlation of trypsin resistance to the strength of cell adhesion.
- ItemEnhanced Adhesion of Electrospun Polycaprolactone Nanofibers to Plasma-Modified Polypropylene Fabric(MDPI, 2023-03-28) Janů, Lucie; Dvořáková, Eva; Polášková, Kateřina; Janůšová, Martina; Ryšánek, Petr; Chlup, Zdeněk; Kruml, Tomáš; Galmiz, Oleksandr; Nečas, David; Zajíčková, LenkaExcellent adhesion of electrospun nanofiber (NF) to textile support is crucial for a broad range of their bioapplications, e.g., wound dressing development. We compared the effect of several low- and atmospheric pressure plasma modifications on the adhesion between two parts of composite-polycaprolactone (PCL) nanofibrous mat (functional part) and polypropylene (PP) spunbond fabric (support). The support fabrics were modified before electrospinning by low-pressure plasma oxygen treatment or amine plasma polymer thin film or treated by atmospheric pressure plasma slit jet (PSJ) in argon or argon/nitrogen. The adhesion was evaluated by tensile test and loop test adapted for thin NF mat measurement and the trends obtained by both tests largely agreed. Although all modifications improved the adhesion significantly (at least twice for PSJ treatments), low-pressure oxygen treatment showed to be the most effective as it strengthened adhesion by a factor of six. The adhesion improvement was ascribed to the synergic effect of high treatment homogeneity with the right ratio of surface functional groups and sufficient wettability. The low-pressure modified fabric also stayed long-term hydrophilic (ten months), even though surfaces usually return to a non-wettable state (hydrophobic recovery). In contrast to XPS, highly surface-sensitive water contact angle measurement proved suitable for monitoring subtle surface changes.
- ItemDepth profiling of thin plasma-polymerized amine films using GDOES in an Ar-O-2 plasma(ELSEVIER, 2022-04-15) Kovač, Janez; Ekar, Jernej; Čekada, Miha; Zajíčková, Lenka; Nečas, David; Janů, Lucie; Wang, Jiang Yong; Mozetič, MiranThin polymer films were deposited on polished stainless-steel samples by PECVD from a cyclopropylamine precursor and characterized by X-ray photoelectron spectroscopy, secondary-ion mass spectrometry and glow discharge optical emission spectroscopy (GDOES) depth profiling. These depth profiles exhibited reasonable agreement. The GDOES involved the erosion of the polymer films in plasma sustained by an asymmetric RF capacitively coupled discharge using both Ar and Ar-O-2 gases. The application of pure Ar caused unwanted effects, such as the broadening of the polymer-film/substrate interface, which were suppressed when using the mixture with oxygen. Another benefit of oxygen was a significant increase in the etching rate by a factor of about 15 as compared to pure argon. The mechanisms involved in the depth profiling using the mixture of gases were elaborated in some detail, taking into account plasma parameters typical for an asymmetric, capacitively coupled RF discharge in a small volume. The main benefit of using the Ar/O-2 GDOES profiling with respect to XPS and SIMS depth profiling is the increased sputtering rate for polymer films. Comparing the GDOES depth profiling with the Ar/O-2 mixture with profiling in pure Ar, the benefits are a higher sputtering rate and better depth resolution at the polymer/substrate interface.