Structural and functional characterisation of hydrogels prepared from Porphyridium purpureum under acidic conditions

The red microalgae Porphyridium purpureum exhibits exceptional nutritional properties due to rich protein content, extracellular polysaccharides, polyunsaturated fatty acids, vitamins, and minerals. The coloured and bioactive phycobiliproteins make this microalga a valuable source for developing innovative food products. Herein, we developed a simple procedure to induce the formation of coloured hydrogels (POR) from P. purpureum under acidic conditions (pH 2) by inhibiting the repulsion of charged groups and facilitating polysaccharide chain association. We further investigated the effects of adding alginate at a 0.5 % concentration on the gel structure (POR ALG) and techno-functional properties. The resulting vividly coloured hydrogels were characterised in terms of microstructure (via SEM and confocal microscopy), functional groups (FTIR), rheological behaviour, water uptake and water-holding capacity, digestibility, and antioxidant activity. Alginate addition significantly improved the gel consistency (POR ALG), decreased porosity, and increased the storage modulus by one order of magnitude compared to POR gel. Confocal microscopy revealed that alginate inhibited phycobiliprotein agglomeration, reduced fluorescence, and provided more uniform protein distribution. The water uptake capacity was notably higher in POR ALG hydrogel at pH 2, whereas POR hydrogel had the highest capacity at neutral pH. In vitro digestion studies demonstrated that the hydrogels resisted gastric digestion, while bioactive (chromo)peptides are released in the intestinal phase, thereby preserving their antioxidant activity. Lyophilisation emerged as the preferred drying method, maintaining rehydration potential and structural integrity. The developed P. purpureum-based hydrogels demonstrate significant potential as functional food ingredients, offering bioactive benefits, vibrant colour stability, and protection for sensitive molecules during digestion

Identification of priority sources of potentially hazardous elements from public drinking water fountains in Zaječar/East Serbia

Access to clean drinking water is essential for human health, economic development, and environmental sustainability. To effectively preserve water quality and ensure a safe and stable water supply, it is essential to determine the priority control factors of potentially hazardous elements in water. This study focused on public drinking water fountains in Zaječar City (Serbia), examining water hydrochemistry, quality, potential sources of hazardous elements, and the health risks associated with consumption or dermal exposure. Among all potentially hazardous elements, iron showed a deviation from the limit in drinking water prescribed by the World Health Organization, reaching 631 µg/L. However, all samples were categorized as excellent quality for drinking. Water composition was governed by water-rock interactions, distinguishing Na-HCO3 as the dominant water type. A total of 3.3 % and 6.6 % of samples exceeded the threshold of 1 for non-carcinogenic health risk for adults and children, respectively, with the mean HIa value of 0.35 and the mean HIc value of 0.57. However, the carcinogenic risk was within the allowable limits for children, whereas it surpassed the threshold of 1.0 × 10–4 for adults in 10 % of the samples. The positive matrix factorization model identified four sources responsible for water quality, i.e., natural source, industrial source, sewage source, and agricultural source, with contributions of 37.1 %, 35.0 %, 17.8 %, and 10.1 %, respectively. The Monte Carlo simulation of source-specific health risks revealed that the industrial source was the main contributor to both non-carcinogenic and carcinogenic risks, attributed to its high arsenic load

Viscosity of biodiesel: experiments and modeling

A model has been developed to predict the viscosity of biodiesel fuel. It is based on the extended hard-sphere (EHS) model that assumes conformal viscosity behavior and makes use of the mole average mixing rules. The relevant mixture parameters for unsaturated esters were obtained by means of the effective molecular mass concept, while those for saturated esters were obtained by recourse to previously published correlations. In order to validate the developed model, the density and viscosity of three synthetic biodiesel mixtures, composed of up to five components, were measured at atmospheric pressure at temperatures between (288.15 and 353.15) K. The density was measured by means of a vibrating U-tube densimeter with the combined expanded uncertainty (k ≈ 2) of 2.5 kg⋅m−3. The viscosity was measured with a Stabinger viscometer, with a relative uncertainty of 3.5 %. The data measured in this work, together with the literature viscosity data on both synthetic biodiesel mixtures and real biodiesel fuel was used to validate the developed EHS model. The experimental data, consisting of 84 data points, were represented with the average absolute deviation of 3.5 % and a maximum deviation of 12 %

Tailoring functional properties of gum Arabic and partially hydrolyzed guar gum-based delivery systems for phenylethanoid glycosides from Mountain Germander (Teucrium montanum L.)

The growing popularity of plant extracts as valuable sources of bioactive compounds is clearly reflected in the investment in technological solutions that ensure stability and more convenient integration into food formulations. The aim of this study was to investigate the effect of secondary polymers - hydrolyzed collagen (COL), kappa-carrageenan (CAR) and carboxymethylcellulose (CMC) on the physico-chemical and functional properties of spray-dried microparticles based on gum Arabic (GA) and partially hydrolyzed guar gum (GG) for the delivery of phenylethanoid glycosides from Mountain Germander extract. The viscoelastic properties of the feed solutions as well as the physico-chemical, bioactive and thermal properties of the MG microparticles were determined for all formulations. Improved electrostatic repulsion was observed for the GA_CAR and GG_CMC formulations. The addition of CMC improved the surface morphology and reduced the wettability of the microparticles, thus providing controlled release of the PhG. The ATR-FTIR spectra revealed high affinity of the PhG to interact with polar functional groups of examined carrier matrices. The introduction of COL into the GA solution as well as CMC into the GG solution significantly (p < 0.05) reduced the encapsulation efficiency by max. 25 %, depending on the PhG compound analyzed. The results of this study reveal the suitability of GA and GG for the retention of PhG as well as the emerging potential of CMC for modifying the functional properties of the hydrophilic carrier matrix

Design of the Multi-Bioactive Graphene-Oxide/Gelatin/Alginate Scaffolds as Dual ECM-Mimetic and Specific Wound Healing Phase-Target Therapeutic Concept for Advanced Wound Healing

To develop and evaluate graphene oxide/gelatin/alginate scaffolds for advanced wound therapy capable of mimicking the native extracellular matrix (ECM) and bio-stimulating all specific phases of the wound healing process, from inflammation and proliferation to the remodeling of damaged skin tissue in three dimensions. Methods: The scaffolds were engineered as interpenetrating polymeric networks by the crosslinking reaction of gelatin in the presence of alginate and characterized by structural, morphological, mechanical, swelling properties, porosity, adhesion to the skin tissue, wettability, and in vitro simultaneous release of the active agents. Biocompatibility of the scaffolds were evaluated in vitro by MTT test on fibroblasts (MRC5 cells) and in vivo using Caenorhabditis elegans assay. Results: The scaffolds exhibited a highly porous interconnected morphology with adjustable porosity (93–96%) and mechanical strength (1.10–2.90 MPa), hydrophilic nature with high capacity to absorb physiological fluids, and stable adhesion to the skin tissue. The obtained results of MRC5 cell viability indicate that the scaffolds are safe for biomedical applications. No mortality was detected among the Caenorhabditis elegans throughout the incubation period, indicating that the scaffolds are not toxic. The results of in vitro release study of allantoin, quercetin, and caffeic acid confirm the scaffolds’ significant potential for simultaneous release. Conclusion: The graphene oxide/gelatin/alginate scaffolds are promising candidates for non-invasive, dual ECM-mimetic, and multi-target wound therapy, offering an innovative strategy to address the complexities of wound healing process

Denture base poly(methyl methacrylate) reinforced with SrTiO3/Y2O3: Structural, morphological and mechanical analysis

This study presented the use of SrTiO3/Y2O3 nanoparticles for the reinforcement of dental poly(methyl methacrylate) (PMMA) to enhance its mechanical properties important for everyday use of denture base materials. The average crystallite size of prepared nanoparticles was 19.9 nm. The influence of 0.5, 1.0, and 1.5 wt% SrTiO3/Y2O3 loading on absorbed impact energy, microhardness and tensile properties was investigated. Scanning electron microscopy of the composite fracture surface revealed multiple toughening mechanisms, with agglomerates directly included in the crack pinning, indicating improvement in mechanical performance. Dynamic mechanical analysis proved that agglomerates improved the elastic behavior of PMMA and confirmed the absence of a residual monomer. After the incorporation of SrTiO3/Y2O3, the mechanical properties of composites showed a high increase compared to neat PMMA. The optimal concentration of nanoparticles was 1 wt%, for which the microhardness, modulus of elasticity, and absorbed impact energy were higher by 218.4%, 65.8% and 135.6%, respectively. With such a high increase, this research showed that SrTiO3/Y2O3 represents an efficient filler which use does not have to be limited to dental materials. Highlights: SrTiO3/Y2O3 hybrid nanoparticles were prepared. PMMA-SrTiO3/Y2O3 composite showed increase in impact resistance up to 135.4%. Elastic behavior of PMMA was improved. With 1 wt% of SrTiO3/Y2O3, microhardness increased by 218.4%

Effectiveness of Household Processing Methods in Reducing Pesticide Residues in Apples

Different pests and diseases can seriously affect the production and quality of apples. To ensure yield and quality, intensive pesticide application is commonly practiced during apple growth, which frequently results in the presence of pesticide residues in the final product [1]. Therefore, monitoring and reducing pesticide residues in apples is important for protecting consumer’s health. This study was carried out in order to assess the effectiveness of different household processing methods in reducing pesticide residues presence in apple fruits. The methods examined included immersing the apples in tap water, acetic acid and sodium bicarbonate water solutions, and peeling. Apples analyzed in this study were obtained from local markets in Belgrade. The extraction of pesticide residues was performed by applying the QuEChERS method, followed by analysis with liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) [2]. Multiple pesticide residues were detected in the apple samples, indicating widespread application of plant protection products. The results revealed a variable effectiveness of the applied treatments, depending on the chemical properties and surface affinity of each pesticide. Peeling proved to be the most effective method for removing most residues, suggesting that a significant portion of residues is localized on or near the apple skin. However, this method showed limited efficiency for certain systemic pesticides, such as acetamiprid. These findings provide valuable insight for consumers aiming to reduce dietary exposure to pesticide residues through simple domestic practices

Prisustvo acesulfama u vodi beogradskih reni bunara kao indikatora komunalnog zagađenja

Grad Beograd je jedna od retkih evropskih prestonica koja ne poseduje postrojenje za prečišćavanje komunalnih otpadnih voda, usled čega se velika količina neprečišćenih otpadnih voda ispušta u reke Savu i Dunav. Ove otpadne vode sadrže različite vrste organskih i neorganskih zagađujućih materija, kao i patogenih organizama koji transportom kroz zemljište mogu da dospeju do podzemnih voda i izvora vode za piće. Iz ovog razloga, u okruženju sa velikim komunalnim opterećenjem, za efikasnu kontrolu kvaliteta voda, veoma su važni pouzdani markeri fekalnog zagađenja. Korišćenje bakterijskih indikatora najčešća je metoda u proceni kontaminacije komunalnim otpadnim vodama, međutim ovaj pristup ima svoje nedostatke poput nespecifičnosti za izvor, kratak životni vek u prirodnim vodama i duže vreme potrebno za analizu. Poslednjih godina sve više su u upotrebi hemijski markeri za identifikaciju kanalizacionog zagađenja, koji omogućavaju bržu i pouzdaniju detekciju, imaju veću specifičnost za izvor i otpornost na degradaciju. Među njima, veštački zaslađivači, kao široko korišćeni prehrambeni aditivi, predstavljaju veoma pouzdane i usko specifične markere zagađenja komunalnim otpadnim vodama, zbog njhove metaboličke inertnosti u ljudskom telu i prisutnosti u visokim koncentracijama u otpadnim vodama, kao i velike stabilnosti u životnoj sredini

Necessary Optimality Conditions for Lyapunov-Type Optimization Problem with State Constraints

This paper investigates a Lyapunov-type optimization problem incorporating an inequality integral constraint and a phase inequality constraint, both defined in L∞([0,T],Rn). The problem is approached directly using a theorem of the alternative, assuming differentiability, to derive necessary optimality conditions. Unlike earlier works, such as a nonsmooth convex isoperimetric problem with phase constraints or problems excluding phase constraints, this study focuses on a smooth case of problem. The problem formulation is motivated by the growing interest in continuous-time linear and nonlinear optimization problems, a field originally explored by Bellman (Proc Natl Acad Sci USA, 39:947–951, 1953). Building on prior results where new Karush–Kuhn–Tucker (KKT) conditions were introduced for problems with inequality constraints, this work extends the scope by incorporating an integral constraint into the analysis. The manuscript outlines the problem’s preliminaries, introduces a regularity condition for systems of inequalities, and presents a theorem of the alternative as the foundation for deriving the main results. Necessary optimality conditions are established and illustrated with an example, while the application of computational methods demonstrates how these conditions contribute to finding optimal solutions. By utilizing recent advancements in theorems of the alternative, this paper contributes to the theory of continuous-time programming problems in both finite-dimensional and infinite-dimensional spaces. The findings highlight the importance of integrating analytical and computational approaches to address these increasingly relevant optimization challenges

Optimized UHPLC-MS/MS method for the determination of quaternary ammonium compounds in water

Objective Quaternary ammonium compounds (QACs) are a class of cationic surfactants with potent antimicrobial properties and widespread application in household and industrial disinfectants. Due to their chemical stability and extensive use, QACs are increasingly detected in surface water and wastewater, raising concerns over their potential adverse effects on aquatic ecosystems. This study aimed to develop and validate a sensitive and selective analytical method for the quantification of 14 QACs in water samples using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS)