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Development of novel osteochondral scaffolds and related in vitro environment with the aid of chemical engineering principles
No full textIn tissue engineering, collaboration among experts from different fields is needed to design appropriate
cell scaffolds and the required 3D environment. Osteochondral tissue engineering is particularly
challenging due to the necessity to provide scaffolds that imitate structural and compositional
differences of two neighboring tissues, articular cartilage and bone, and the required complex
biophysical environments to cultivate such scaffolds. This work focuses on two key objectives: first, to
develop bilayered osteochondral scaffolds based on gellan gum and bioactive glass, and second, to
create a biomimetic environment for scaffold characterization by designing and utilization of novel
dual-medium cultivation bioreactor chambers. Basic chemical engineering principles were utilized to
aid both aims. First, a simple heat transport model based on one-dimensional conduction was applied
as a guideline for bilayered scaffold preparation, leading to the formation of the gelatinous upper part
and a macroporous lower part with a thin, well-integrated interfacial zone. Second, a novel cultivation
chamber was developed to be used in a dynamic compression bioreactor to provide possibilities for
flow of two different media, such as chondrogenic and osteogenic. These chambers were utilized for
characterization of the novel scaffolds regarding bioactivity and stability under dynamic compression
and fluid perfusion during 14 days, while flow distribution under different conditions was analyzed by
a tracer method and residence time distribution analysis.This is the Accepted Manuscript version of an article accepted for publication in Biomedical Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at [https://doi.org/10.1088/1748-605X/ad6ac1]This is the peer-reviewed version of the following article: Zvicer J, Milošević M, Medić A, Novak S, Obradović B. Development of novel osteochondral scaffolds and related in vitro environment with the aid of chemical engineering principles. in
Biomedical Materials. 2024. [https://doi.org/10.1088/1748-605X/ad6ac1]Published version: [https://technorep.tmf.bg.ac.rs/handle/123456789/7614
Design and simulations of a helical oscillatory baffled reactor for biochemical reactions
No full textA helical oscillatory flow reactor with orifice baffles (HOBR) is proposed for use in slow biochemical and pharmaceutical processes. The new reactor geometry with 10 mm diameter was analyzed using the dynamic 3D CFD model and pulse tracer experiments in a 3D printed prototype, for a range of oscillatory and non-oscillatory flowrates (Reo = 25 – 300 and Ren = 20 – 78). Comparison of the HOBR with the classical OBR design using CFD simulations, under the same flow conditions, showed that the new geometry provides near plug flow conditions and notably improves mixing performance. This is due to more complex flow patterns and the enhanced radial mixing, including pairs of Dean vortices, which is related to the baffled tube helical design. A model reduction based on the tanks-in-series approach was examined. The proposed two-parameter correlation can predict the residence time distribution behavior inside of HOBR over the entire range of flow conditions tested
Fabrication of Polycaprolactone-Based Polyurethanes with Enhanced Thermal Stability
No full textThe benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO2 nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO2 NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO2 NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO2 NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO2 NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO2 NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO2 NPs on the thermal stability and aging resistance of PU
Thermal, mechanical, and dielectric properties of radiation sterilized mesomorphic PP: Comparison between gamma and electron beam irradiation modalities
No full textPolypropylene (PP) is widely used in the medical industry to produce syringes, vials, and numerous other single-use biopharmaceutical devices. The need to sterilize these products has led to intensive use of high-energy radiation, even though PP is known to undergo excessive oxidative degradation and deterioration in properties upon irradiation in air. In recent years, a shortage in 60Co supply, as a main source for gamma sterilization, is pushing radiation sterilization of polymeric medical products to electron beam (EB) and/or X-ray modalities as preferable. Some questions related to the equivalence of these methods remain open and are mostly related to changes in the material structure caused by different types of radiation and processing conditions, such as dose rates. This research compares electron beam and gamma irradiation modalities employed on the low crystalline (quenched) PP. In the case of EB irradiation, the typical dose rates are on the order of 104 kGy/h, while in the case of gamma radiation dose rates are lower for three or more orders of magnitude. Since gamma irradiation covers a wide range of dose rates, the difference between samples gamma irradiated with relatively fast (8 kGy/h) and slow (0.08 kGy/h) dose rates was also analyzed in detail. Comparative investigation of crystallinity, oxidative degradation, thermal, dielectric, and mechanical properties provide a clearer picture of the impact of different modalities and dose rates on mesomorphic PP and are of interest in the practical application of ionizing radiation in the sterilization of PP-based medical devices
Non-destructive evaluation of cavitation erosion behavior of alumina-based ceramic materials
No full textNumerous industrial parts, devices, and processes are designed to withstand the conditions that lead to cavitation erosion. Metallic, ceramic, and composite materials used for these conditions must achieve specific mechanical characteristics required to resist cavitation erosion. When molten metal or alloy flows and comes into contact with refractory material or coated furnace linings, cavitation erosion can occur. This phenomenon is particularly expected in metallurgy, especially in casting operations. Alumina-based refractories, specifically low cement castable (ALCC), are often used in furnace lining applications due to their superior properties, such as high refractoriness, thermal stability, and mechanical characteristics. Mullite is another refractory material frequently used in foundry lining applications. It can be utilized as a coating in casting processes, such as the Lost Foam process, which is a novel method for producing high-quality, cost-effective castings. These two refractory materials were chosen to study their behavior under cavitation conditions. An ultrasonic vibratory test with a stationary specimen (ASTM G-32) was used for experimental cavitation determination. The results of mass loss and surface morphological parameters of degradation revealed that ALCC samples eroded predominantly at the surface, while the mullite samples exhibited more significant degradation by depth
Craft Beer Produced by Immobilized Yeast Cells with the Addition of Grape Pomace Seed Powder: Physico-Chemical Characterization and Antioxidant Properties
No full textThe aim of this study was to produce and to characterize craft beer fermented by immobilized yeast cells with the addition of Prokupac grape pomace seed powder (2.5% and 5%), to obtain a
beer enriched with phenolic compounds and improved sensory characteristics. The immobilization
of the yeast cells was performed by electrostatic extrusion, while the obtained calcium alginate beads
were characterized by light and scanning electron microscopy. Phenolic and hop-derived bitter
compounds in beer with or without grape pomace seed powder (GS) phenolics were identified using
UHPLC Q-ToF MS. The results indicated that GS adjunct significantly shortened the fermentation
process of wort and increased the content of phenolic compounds, especially ellagic acid, flavan-3-ols
and pro(antho)cyanidins in the final products compared to the control beer. A total of twenty (iso)-αacids and one prenylflavonoid were identified, although their levels were significantly lower in beers
with GS phenolics compared to the control beer. Beers with GS phenolics showed good antioxidant
properties as measured by the reduction of ferric ions (FRP) and the scavenging of ABTS•+ and
DPPH•
radicals. The concentration of immobilized viable yeast cells was higher than 1 × 108 CFU/g
wet mass after each fermentation without destroying the beads, indicating that they can be reused
for the repeated fermentation of wort. Beers produced with 5% GS added to the wort exhibited the
best sensory properties (acidity, astringency, bitterness intensity, mouthfeel, aftertaste and taste), and
highest overall acceptability by the panelists. The results showed that grape pomace seed powder
present a promising adjunct for the production of innovative craft beer with good sensory properties
and improved functionality
Zn2+/Poly(2-Hydroxyethyl Acrylate/Itaconic Acid) Hydrogels as Potential Antibacterial Wound Dressings
No full textAntibacterial hydrogels, as an advanced approach, can create optimal conditions for wound healing, even in the fight against stubborn and difficult-to-treat wound infections. Interestingly, pH is an often neglected clinical parameter, although it has a significant impact on the wound healing process. At different stages of wound healing, the pH in the wound bed changes from slightly alkaline to neutral to acidic. To develop novel pH-sensitive antibacterial hydrogel dressings, Zn2+-loaded poly(2-hydroxyethyl acrylate/itaconic acid) hydrogels are synthesized. The hydrogels exhibit pH-sensitive swelling in the physiologically relevant pH range, with a pronounced swelling ability at neutral pH. The controlled release of Zn2+ occurs in a buffer of pH 7.40 at 37 °C. The liquid transport mechanism and release kinetics are evaluated using the specific kinetic models of Ritger-Peppas and Peppas-Sahlin. The effect of Zn2+ on structural, thermal, swelling, cytocompatibility, and antibacterial properties is evaluated by Fourier transform infrared spectroscopy, differential scanning calorimetry, swelling studies, MTT, and antibacterial tests. The hydrogels show excellent antibacterial activity against Escherichia coli. The research opens new perspectives for efficient wound healing management, and the extension of the study will be orchestrated by optimising the hydrogel composition to achieve improved performance
Cold plasma treatment as green technology in food processing
No full textCold plasma has become an emerging technology in the food industry. It is widely used as a non-thermal sterilization technique due to its antimicrobial activity. Besides direct plasma treatment, plasma-activated water (PAW) also showed potential for increasing fresh food shelf life. This is possible thanks to PAW's ability to inactivate enzymes responsible for food browning. Additionally, cold plasma could modify existing materials or adjust biopolymer properties, making them suitable for functional food packaging. This study aimed to examine the possibility of cold plasma jet utilization both for less studied applications, including isolating lignin from agri-food waste and producing PAW for fresh-cut apple treatment. By combining cold plasma and alkaline treatment on corn stalks, we obtained oxidized lignin micro- and nanoparticles possessing antioxidative activity. These particles were rich in total phenolic content, reaching up to 140±20 μg gallic acid equivalents per mg of lignin. Granny Smith apples were washed, peeled, and diced into 1x1x1 cm cubes, and soaked in differently activated PAW for 20 minutes. After PAW treatment, apples were stored in glass bottles with a screw cap at 4°C, and changes in their appearance were observed. Apples treated with PAW activated for 30 minutes retained a fresh look and bright color even after 7 days. The overall results of this study confirmed that cold plasma could be used in the processing and preservation of fresh-cut products, but its impact on flavor, nutrition, chemical, and textural properties should be further investigated. Cold plasma-based treatments of lignocellulosic biomass open new possibilities for isolating biopolymers, i.e. lignin, cellulose, and hemicellulose, which could be incorporated into active food packaging following circular bioeconomy principles
Effect of pretreatment, lyophilization parameters, and different cryoprotectants on the efficiency of probiotic freeze-drying immobilization process
No full textLyophilization is an excellent process to increase the shelf life of food products. It is also used to
preserve probiotics. Living cells prefer mild conditions and any deviation, such as vacuum, high
or low temperatures, leads to cell damage and death. This paper examined how different
pretreatments, lyophilization time, freezing types, and cryoprotectants affect the survival of
probiotic during the freeze-drying immobilization process using the activated charcoal pad.
Activation of L. plantarum in MRS broth before freezing, in addition to increasing the initial
number of living cells, also affected the survival rate of the entire lyophilization process.
Freezing the culture in liquid nitrogen did not significantly affect the viability of the culture after
lyophilization compared to deep freezing at 80 °C, while incubation culture in a refrigerator for
2h before lyophilization increased the viability of probiotic. Also, the duration of lyophilization
in the period from 5 to 48 hours has a slight impact on probiotic viability. The use of milk
showed a significant increase in culture survival, while different percentages of sucrose, maltose,
and trehalose showed cryoprotectant ability, but significantly lower than milk. The combination
of milk and trehalose as well as the well-known cryoprotectant R18 did not increase the viability
of probiotic compared to milk alone. The highest viability of L. plantarum during lyophilization
shows procedure with MRS incubation for 18h two times before lyophilization, then deep
freezing at 80 °C in milk, and lyophilization for 5h
Inorganic fullerene-like tungsten disulfide nanoparticles strongly modulate the immune response in vitro
No full textTungsten disulfide (WS2) nanoparticles have been extensively investigated in the biomedical field as theranostics due to their specific properties, including good biocompatibility. However, almost nothing is known about their effect on the immune system. This study aimed to investigate the effects of inorganic fullerene-like WS2 (IF- WS2) nanostructures on the immune response in vitro.Special Issue: Abstract Book / 7th European Congress of Immunology ECI 2024, 1-4 September, 2024 Dublin, Irelan