Exploring chitosan-plant extract bilayer coatings: Advancements in active food packaging via polypropylene modification.

UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.

Influence of different intraoperative fluid management on postoperative outcome after abdominal tumours resection.

BACKGROUND: Intraoperative fluid management is a crucial aspect of cancer surgery, including colorectal surgery and pancreatoduodenectomy. The study tests if intraoperative multimodal monitoring reduces postoperative morbidity and duration of hospitalisation in patients undergoing major abdominal surgery treated by the same anaesthetic protocols with epidural analgesia. PATIENTS AND METHODS: A prospective study was conducted in 2 parallel groups. High-risk surgical patients undergoing major abdominal surgery were randomly selected in the control group (CG), where standard monitoring was applied (44 patients), and the protocol group (PG), where cerebral oxygenation and extended hemodynamic monitoring were used with the protocol for intraoperative interventions (44 patients). RESULTS: There were no differences in the median length of hospital stay, CG 9 days (interquartile range [IQR] 8 days), PG 9 (5.5), p = 0.851. There was no difference in postoperative renal of cardiac impairment. Procalcitonin was significantly higher (highest postoperative value in the first 3 days) in CG, 0.75 mcg/L (IQR 3.19 mcg/L), than in PG, 0.3 mcg/L (0.88 mcg/L), p = 0.001. PG patients received a larger volume of intraoperative fluid; median intraoperative fluid balance +1300 ml (IQR 1063 ml) than CG; +375 ml (IQR 438 ml), p < 0.001. CONCLUSIONS: There were significant differences in intraoperative fluid management and vasopressor use. The median postoperative value of procalcitonin was significantly higher in CG, suggesting differences in immune response to tissue trauma in different intraoperative fluid status, but there was no difference in postoperative morbidity or hospital stay.

Carboxymethylated and Sulfated Furcellaran from Furcellaria lumbricalis and Its Immobilization on PLA Scaffolds.

This study involved the creation of highly porous PLA scaffolds through the porogen/leaching method, utilizing polyethylene glycol as a porogen with a 75% mass ratio. The outcome achieved a highly interconnected porous structure with a thickness of 25 µm. To activate the scaffold's surface and improve its hydrophilicity, radiofrequency (RF) air plasma treatment was employed. Subsequently, furcellaran subjected to sulfation or carboxymethylation was deposited onto the RF plasma treated surfaces with the intention of improving bioactivity. Surface roughness and water wettability experienced enhancement following the surface modification. The incorporation of sulfate/carboxymethyl group (DS = 0.8; 0.3, respectively) is confirmed by elemental analysis and FT-IR. Successful functionalization of PLA scaffolds was validated by SEM and XPS analysis, showing changes in topography and increases in characteristic elements (N, S, Na) for sulfated (SF) and carboxymethylated (CMF). Cytocompatibility was evaluated by using mouse embryonic fibroblast cells (NIH/3T3).

Recent Progress in Cellulose Hydrophobization by Gaseous Plasma Treatments.

Cellulose is an abundant natural polymer and is thus promising for enforcing biobased plastics. A broader application of cellulose fibers as a filler in polymer composites is limited because of their hydrophilicity and hygroscopicity. The recent scientific literature on plasma methods for the hydrophobization of cellulose materials is reviewed and critically evaluated. All authors focused on the application of plasmas sustained in fluorine or silicon-containing gases, particularly tetrafluoromethane, and hexamethyldisiloxane. The cellulose materials should be pre-treated with another plasma (typically oxygen) for better adhesion of the silicon-containing hydrophobic coating. In contrast, deposition of fluorine-containing coatings does not require pre-treatment, which is explained by mild etching of the cellulose upon treatment with F atoms and ions. The discrepancy between the results reported by different authors is explained by details in the gas phase and surface kinetics, including the heating of samples due to exothermic surface reactions, desorption of water vapor, competition between etching and deposition, the influence of plasma radiation, and formation of dusty plasma. Scientific and technological challenges are highlighted, and the directions for further research are provided.

The Influence of Reaction Conditions on the Properties of Graphene Oxide.

The present study focuses on correlations between three parameters: (1) graphite particle size, (2) the ratio of graphite to oxidizing agent (KMnO4), and (3) the ratio of graphite to acid (H2SO4 and H3PO4), with the reaction yield, structure, and properties of graphene oxide (GO). The correlations are a challenge, as these three parameters can hardly be separated from each other due to the variations in the viscosity of the system. The larger the graphite particles, the higher the viscosity of GO. Decreasing the ratio of graphite to KMnO4 from 1:4 to 1:6 generally leads to a higher degree of oxidation and a higher reaction yield. However, the differences are very small. Increasing the graphite-to-acid-volume ratio from 1 g/60 mL to 1 g/80 mL, except for the smallest particles, reduced the degree of oxidation and slightly reduced the reaction yield. However, the reaction yield mainly depends on the extent of purification of GO by water, not on the reaction conditions. The large differences in the thermal decomposition of GO are mainly due to the bulk particle size and less to other parameters.

Loss of Oxygen Atoms on Well-Oxidized Cobalt by Heterogeneous Surface Recombination.

Calorimetry is a commonly used method in plasma characterization, but the accuracy of the method is tied to the accuracy of the recombination coefficient, which in turn depends on a number of surface effects. Surface effects also govern the kinetics in advanced methods such as atomic layer oxidation of inorganic materials and functionalization of organic materials. The flux of the reactive oxygen atoms for the controlled oxidation of such materials depends on the recombination coefficient of materials placed into the reaction chamber, which in turn depends on the surface morphology, temperature, and pressure in the processing chamber. The recombination coefficient of a well-oxidized cobalt surface was studied systematically in a range of temperatures from 300 to 800 K and pressures from 40 to 200 Pa. The coefficient increased monotonously with decreasing pressure and increasing temperature. The lowest value was about 0.05, and the highest was about 0.30. These values were measured for cobalt foils previously oxidized with oxygen plasma at the temperature of 1300 K. The oxidation caused a rich morphology with an average roughness as deduced from atomic force images of 0.9 µm. The results were compared with literature data, and the discrepancy between results reported by different authors was explained by taking into account the peculiarities of their experimental conditions.

Germination and Growth of Plasma-Treated Maize Seeds Planted in Fields and Exposed to Realistic Environmental Conditions.

In this study, we applied an inductively coupled, radio frequency oxygen plasma to maize seeds and investigated its effects on seedling emergence, plant number at tasseling, and crop yield of maize in realistic field conditions. Maize seeds of seven different hybrids were treated over two harvest years. In addition to plasma-treated seeds, a control sample, fungicide-treated seeds, an eco-layer, and a plasma and eco-layer combination, were planted. Seedling emergence, plant number at tasseling (plants/m2), and yield (kg/ha), were recorded. In the first harvest year, results were negatively affected by the presence of an insect pest. In the second harvest year, plant number and yield results were more uniform. In both years, for two and three hybrids, respectively, the highest yield arose from plants from plasma-treated seeds, but the differences were only partially significant. Considering our results, plasma treatment of maize seeds appears to have a positive effect on the yield of the plant.

A Review of Recombination Coefficients of Neutral Oxygen Atoms for Various Materials.

Relevant data on heterogeneous surface recombination of neutral oxygen atoms available in the scientific literature are reviewed and discussed for various materials. The coefficients are determined by placing the samples either in non-equilibrium oxygen plasma or its afterglow. The experimental methods used to determine the coefficients are examined and categorized into calorimetry, actinometry, NO titration, laser-induced fluorescence, and various other methods and their combinations. Some numerical models for recombination coefficient determination are also examined. Correlations are drawn between the experimental parameters and the reported coefficients. Different materials are examined and categorized according to reported recombination coefficients into catalytic, semi-catalytic, and inert materials. Measurements from the literature of the recombination coefficients for some materials are compiled and compared, along with the possible system pressure and material surface temperature dependence of the materials' recombination coefficient. A large scattering of results reported by different authors is discussed, and possible explanations are provided.

Deposition of Chitosan on Plasma-Treated Polymers-A Review.

Materials for biomedical applications often need to be coated to enhance their performance, such as their biocompatibility, antibacterial, antioxidant, and anti-inflammatory properties, or to assist the regeneration process and influence cell adhesion. Among naturally available substances, chitosan meets the above criteria. Most synthetic polymer materials do not enable the immobilization of the chitosan film. Therefore, their surface should be altered to ensure the interaction between the surface functional groups and the amino or hydroxyl groups in the chitosan chain. Plasma treatment can provide an effective solution to this problem. This work aims to review plasma methods for surface modification of polymers for improved chitosan immobilization. The obtained surface finish is explained in view of the different mechanisms involved in treating polymers with reactive plasma species. The reviewed literature showed that researchers usually use two different approaches: direct immobilization of chitosan on the plasma-treated surface or indirect immobilization by additional chemistry and coupling agents, which are also reviewed. Although plasma treatment leads to remarkably improved surface wettability, this was not the case for chitosan-coated samples, where a wide range of wettability was reported ranging from almost superhydrophilic to hydrophobic, which may have a negative effect on the formation of chitosan-based hydrogels.

Screen-printing of chitosan and cationised cellulose nanofibril coatings for integration into functional face masks with potential antiviral activity.

Masks proved to be necessary protective measure during the COVID-19 pandemic, but they provided a physical barrier rather than inactivating viruses, increasing the risk of cross-infection. In this study, high-molecular weight chitosan and cationised cellulose nanofibrils were screen-printed individually or as a mixture onto the inner surface of the first polypropylene (PP) layer. First, biopolymers were evaluated by various physicochemical methods for their suitability for screen-printing and antiviral activity. Second, the effect of the coatings was evaluated by analysing the morphology, surface chemistry, charge of the modified PP layer, air permeability, water-vapour retention, add-on, contact angle, antiviral activity against the model virus phi6 and cytotoxicity. Finally, the functional PP layers were integrated into face masks, and resulting masks were tested for wettability, air permeability, and viral filtration efficiency (VFE). Air permeability was reduced for modified PP layers (43 % reduction for kat-CNF) and face masks (52 % reduction of kat-CNF layer). The antiviral potential of the modified PP layers against phi6 showed inhibition of 0.08 to 0.97 log (pH 7.5) and cytotoxicity assay showed cell viability above 70 %. VFE of the masks remained the same (~99.9 %), even after applying the biopolymers, confirming that these masks provided high level of protection against viruses.

Probiotic Lactobacillus paragasseri K7 Nanofiber Encapsulation Using Nozzle-Free Electrospinning.

Probiotics are live microorganisms that can have beneficial effects on humans. Encapsulation offers them a better chance of survival. Therefore, nozzle-free electrospinning was introduced for their embedding in nanofibrous material. Probiotic Lactobacillus paragasseri K7 in lyophilized and fresh form, with and without inulin as prebiotic, was added to a polymer solution of sodium alginate (NaAlg) and polyethylene oxide (PEO). Conductivity, viscosity, pH, and surface tension were determined to define the optimal concentration and volume ratio for smooth electrospinning. The success of the formed nanoscale materials was examined by scanning electron microscope (SEM), while the entrapment of probiotics in the nanofibrous mats was detected by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Spontaneous diffusion of bacteria from electrospun samples in PBS buffer pH 7.4 was studied by plate counting on MRS agar. By exposing polymer solutions containing L. paragasseri K7 and inulin to a high electric field, the nanofilm was formed on a polypropylene substrate, used as collecting material. When polymer solutions without inulin were used, the bead-like nanofibers may have become visible. The SEM results suggest that inulin, in addition to K7 strain, additionally lowers the conductivity of spinning macromolecular solution and hinders the nanofiber formation. The results of ATR-FTIR confirmed the presence of L. paragasseri K7 embedded in nanocomposites by the appearance of characteristic peaks. The samples containing the probiotic regardless of its form with inulin had similar surface composition, except that the sodium content was higher in the samples with fresh probiotic, probably due to greater and thus less easy embedding of the bacteria in NaAlg. Within 2 h, the largest amount of probiotic strain K7 was spontaneously released from the electrospun sample containing the inulin and probiotic in freeze-dried form (44%), while the amount released from the nanofibrous sample, which also contained the inulin and probiotic in fresh form, was significantly lower (21%). These preliminary results demonstrate the potential of nozzle-free electrospinning technology for the development of probiotic delivery systems for short-term use, such as feminine hygiene materials (tampons, pads, napkins).

A Method for the Immobilization of Chitosan onto Urinary Catheters.

A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds.

Mechanisms Involved in the Modification of Textiles by Non-Equilibrium Plasma Treatment.

Plasma methods are often employed for the desired wettability and soaking properties of polymeric textiles, but the exact mechanisms involved in plasma-textile interactions are yet to be discovered. This review presents the fundamentals of plasma penetration into textiles and illustrates mechanisms that lead to the appropriate surface finish of fibers inside the textile. The crucial relations are provided, and the different concepts of low-pressure and atmospheric-pressure discharges useful for the modification of textile's properties are explained. The atmospheric-pressure plasma sustained in the form of numerous stochastical streamers will penetrate textiles of reasonable porosity, so the reactive species useful for the functionalization of fibers deep inside the textile will be created inside the textile. Low-pressure plasmas sustained at reasonable discharge power will not penetrate into the textile, so the depth of the modified textile is limited by the diffusion of reactive species. Since the charged particles neutralize on the textile surface, the neutral species will functionalize the fibers deep inside the textile when low-pressure plasma is chosen for the treatment of textiles.

Effect of Oxygen Plasma Treatment on Wheat Emergence and Yield in the Field.

This paper investigates the effects of an inductively coupled, radio frequency oxygen plasma on the plant emergence and crop yield of wheat in field growth conditions. Wheat seeds of eight different cultivars were plasma-treated using conditions selected based on preliminary experiments. Additionally, a control sample, as well as seeds treated with fungicide, an eco-layer, or a plasma + eco-layer combination, were planted in parallel. Four cultivars per harvest year were used. Plant emergence (plants/m2) and yield (kg/ha) were followed. There was little variation among the control and the various treatments regarding plant emergence. Regarding yield, there were statistically significant differences, but no discernible trend was seen when comparing the individual treatments. In the case of several cultivars, plasma-treated seeds performed as well as the control, but there was a significant increase in yield only in the case of cultivar 88.5 R. In several cases, yield of plants for plasma-treated seeds was also lower than the control. Our results demonstrate that the response of wheat yield to plasma treatment, as well as to other seed treatments, differs depending on the wheat cultivar.

Nanoporous Stainless Steel Materials for Body Implants-Review of Synthesizing Procedures.

Despite the inadequate biocompatibility, medical-grade stainless steel materials have been used as body implants for decades. The desired biological response of surfaces to specific applications in the body is a highly challenging task, and usually not all the requirements of a biomaterial can be achieved. In recent years, nanostructured surfaces have shown intriguing results as cell selectivity can be achieved by specific surface nanofeatures. Nanoporous structures can be fabricated by anodic oxidation, which has been widely studied for titanium and its alloys, while no systematic studies are so far available for stainless steel (SS) materials. This paper reviews the current state of the art in the anodisation of SS; correlations between the parameters of anodic oxidation and the surface morphology are drawn. The results reported by various authors are scattered because of a variety of experimental configurations. A linear correlation between the pores' diameter anodisation voltage was deduced, while no correlation with other processing parameters was found obvious. The analyses of available data indicated a lack of systematic experiments, which are recommended to understand the kinetics of pore formation and develop techniques for optimal biocompatibility of stainless steel.

Crystalloids vs. colloids for fluid optimization in patients undergoing brain tumour surgery.

BACKGROUND: This randomised, double-blinded, single-centre study prospectively investigated the impact of goal directed therapy and fluid optimization with crystalloids or colloids on perioperative complications in patients undergoing brain tumour surgery. Main aim of the study was to investigate the impact of fluid type on postoperative complications. PATIENTS AND METHODS: 80 patients were allocated into two equal groups to be optimised with either crystalloids (n = 40) or colloids (n = 40). Invasive hemodynamic monitoring was used to adjust and maintain mean arterial pressure and cerebral oxygenation within the baseline values (± 20%) and stroke volume variation (SVV) ≤ 10%. Postoperative complications from different organ systems were monitored during the first 15 days after surgery. Hospital stay was also recorded. RESULTS: Crystalloid group received significantly more fluids (p = 0.003) and phenylephrine (p = 0.02) compared to colloid group. This did not have any significant impact on perioperative complications and hospital stay, since no differences between groups were observed. CONCLUSIONS: Either crystalloids or colloids could be used for fluid optimization in brain tumour surgery. If protocolised perioperative haemodynamic management is used, the type of fluid does not have significant impact on the outcome.

Furcellaran Surface Deposition and Its Potential in Biomedical Applications.

Surface coatings of materials by polysaccharide polymers are an acknowledged strategy to modulate interfacial biocompatibility. Polysaccharides from various algal species represent an attractive source of structurally diverse compounds that have found application in the biomedical field. Furcellaran obtained from the red algae Furcellaria lumbricalis is a potential candidate for biomedical applications due to its gelation properties and mechanical strength. In the present study, immobilization of furcellaran onto polyethylene terephthalate surfaces by a multistep approach was studied. In this approach, N-allylmethylamine was grafted onto a functionalized polyethylene terephthalate (PET) surface via air plasma treatment. Furcellaran, as a bioactive agent, was anchored on such substrates. Surface characteristics were measured by means of contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Subsequently, samples were subjected to selected cell interaction assays, such as antibacterial activity, anticoagulant activity, fibroblasts and stem cell cytocompatibility, to investigate the Furcellaran potential in biomedical applications. Based on these results, furcellaran-coated PET films showed significantly improved embryonic stem cell (ESC) proliferation compared to the initial untreated material.

Surface Modifications of Wheat Cultivar Bologna upon Treatment with Non-Equilibrium Gaseous Plasma.

Seeds of wheat cultivar Bologna were treated with a low-pressure, inductively coupled, radio frequency oxygen plasma. E-mode and H-mode plasma at the real powers of 25 and 275 W, respectively, was used at treatment times of 0.1-300 s. Plasma affected seed surface chemistry, determined by XPS, and surface topography, visualized by SEM. The combined effects of functionalization and etching modified seed surface wettability. The water contact angle (WCA) exponentially decreased with treatment time and correlated with the product of discharge power and treatment time well. Super-hydrophilicity was seen at a few 1000 Ws, and the necessary condition was over 35 at.% of surface oxygen. Wettability also correlated well with O-atom dose, where super-hydrophilicity was seen at 1024-1025 m-2. A relatively high germination percentage was seen, up to 1000 Ws (O-atom dose 1023-1024 m-2), while seed viability remained unaffected only up to about 100 Ws. Extensively long treatments decreased germination percentage and viability.

Comparison of Plasma Deposition of Carbon Nanomaterials Using Various Polymer Materials as a Carbon Atom Source.

Carbon nanowalls are promising materials for various electrochemical devices due to their chemical inertness, desirable electrical conductivity, and excellent surface-to-mass ratio. Standard techniques, often based on plasma-assisted deposition using gaseous precursors, enable the synthesis of top-quality carbon nanowalls, but require long deposition times which represents a serious obstacle for mass applications. Here, an alternative deposition technique is presented. The carbon nanowalls were synthesized on titanium substrates using various polymers as solid precursors. A solid precursor and the substrate were mounted into a low-pressure plasma reactor. Plasma was sustained by an inductively coupled radiofrequency discharge in the H-mode at the power of 500 W. Spontaneous growth of carbon nanomaterials was observed for a variety of polymer precursors. The best quality of carbon nanowalls was obtained using aliphatic polyolefins. The highest growth rate of a thin film of carbon nanowalls of about 200 nm/s was observed. The results were explained by different degradation mechanisms of polymers upon plasma treatment and the surface kinetics.

Rapid Functionalization of Polytetrafluorethylene (PTFE) Surfaces with Nitrogen Functional Groups.

The biocompatibility of body implants made from polytetrafluoroethylene (PTFE) is inadequate; therefore, the surface should be grafted with biocompatible molecules. Because PTFE is an inert polymer, the adhesion of the biocompatible film may not be appropriate. Therefore, the PFTE surface should be modified to enable better adhesion, preferably by functionalization with amino groups. A two-step process for functionalization of PTFE surface is described. The first step employs inductively coupled hydrogen plasma in the H-mode and the second ammonia plasma. The evolution of functional groups upon treatment with ammonia plasma in different modes is presented. The surface is saturated with nitrogen groups within a second if ammonia plasma is sustained in the H-mode at the pressure of 35 Pa and forward power of 200 W. The nitrogen-rich surface film persists for several seconds, while prolonged treatment causes etching. The etching is suppressed but not eliminated using pulsed ammonia plasma at 35 Pa and 200 W. Ammonia plasma in the E-mode at the same pressure, but forward power of 25 W, causes more gradual functionalization and etching was not observed even at prolonged treatments up to 100 s. Detailed investigation of the XPS spectra enabled revealing the surface kinetics for all three cases.