Improving electrochemical aptasensor sensitivity for Bacillus cereus spore detection in food safety applications

Rapid detection of Bacillus cereus spores is essential for preventing food contamination and spoilage. Many existing methods detect B. cereus vegetative cells rather than spores and cannot be applied directly to foods. Here, we present a combination of aptamers targeting different moieties on the surface of B. cereus spores with rapid electrochemical detection. When DNA aptamers, previously selected for B. cereus spores, were immobilized on screen-printed gold electrodes, they exhibited higher binding capacity than individual aptamers, suggesting a synergistic effect. Additionally, the mixture of rhodamine-labelled aptamers enabled spatial fluorescent visualization of the B. cereus endospore structure, confirming the increased binding efficiency. The electrochemical aptasensor based on three aptamers exhibited a wide dynamic range (102–107 CFU/mL) and low limit of detection (∼1 CFU/mL) using just 15 μL of sample. Validation in spiked salad, using direct spore sensing in rinse water and comparison with the culturing method, confirmed its sensitivity and specificity. These combined aptamer approaches, achieving rapid (15 min) and single-step detection may also be suitable for detecting other foodborne pathogens.Supporting information: [https://cer.ihtm.bg.ac.rs/handle/123456789/9025

Novel N-doped carbon/Co/Co3O4 ternary composites derived by direct carbonization of ZIF-67: Efficient electrocatalysts for oxygen reduction reaction

Cobalt-containing zeolitic imidazole framework ZIF-67 was synthesized in high yield, and directly carbonized by different heating routes at 800 and 900 °C. The products of carbonization, C(ZIF-67)s, were comprehensively characterized in terms of elemental composition (FAAS, EDX, XPS), crystalline (XRD) and molecular structure (FTIR and Raman spectroscopies), morphology (SEM), electrical conductivity, textural (N2 physisorption), and electrochemical properties. It was found that C(ZIF-67)s represent novel meso/microporous ternary composites of the type N-doped carbon/Co/Co3O4, containing metallic Co nanoparticles (NPs) with cubic body-centred crystalline structure, and predominately amorphous Co3O4. They exhibited high electrical conductivity (up to 4.2 S cm−1), notable BET specific surface area (197–265 cm2 g−1), and almost doubled mesopore volume compared to the parent ZIF-67. The effects of carbonization conditions on the structure, physico-chemical properties, and performance of C(ZIF-67)s as electrode materials in electrocatalysis of oxygen reduction reaction (ORR) and charge storage were studied. All C(ZIF-67) composites showed excellent ORR electrocatalytic activity in 0.1 M KOH, with four-electron reduction pathway. The highest ORR activity (the onset potential of −0.13 V vs. SCE) showed the composite produced by gradual heating up to 800 °C followed by holding at that temperature for 3 h. This is attributed to its highest mesopore volume, appropriate meso/micropore structure, high surface content of heteroatom-containing active sites (C–O–C, Co–N, Co–O), high surface Co2+/Co3+ ratio and the presence of Co NPs. The applied direct carbonization of ZIF-67, without additives and post-synthetic modifications, was shown as a simple way to produce meso/microporous electroconducting composites with high potential in energy related applications

COVID-19 ante portas: Empirical formula, growth reactions and thermodynamic properties of biosynthesis and antigen-receptor binding of the Omicron XFG variant of SARS-CoV-2

No one walks alone. In 2019, humanity obtained a permanent companion called SARS-CoV-2. SARS-CoV-2 lives with its human host, adapts to the human host and evolves, in a similar process to that in the human host. The XFG variant is the latest in the sequence of variants that appeared during the process of adaptation. Science has intensively followed the process of evolution of SARS-CoV-2. It was noticed that in accordance with the expectations of the evolution theory, SARS-CoV-2 variants have become less pathogenic and more infective. However, there is a great concern in the general public because of the millions of casualties during the COVID-19 pandemic. In this paper, chemical and thermodynamic characterization was performed: empirical formulas, reactions of biosynthesis, antigen-receptor binding reaction and thermodynamic properties of live matter, biosynthesis and binding were determined, mechanistic model of virus-host interactions was developed and the driving force of biological processes during the life cycle of the virus was determined

Gamma rays assisted synthesis of N doped-graphene quantum dots from multiwall carbon nanotubes

Gamma rays are the powerful tool for top-down synthesis of nitrogen doped graphene quantum dots (NGQDs) from multiwall carbon nanotubes. Different doses of gamma rays (100, 200 and 300 kGy) were applied to the multiwall carbon nanotubes suspended in mixture of sulfuric and nitric acid (3:1 ratio). After purification, NGQD were characterized to investigate their structure (morphology, particle size, nanomechanical and nanoelectrical properties, chemical composition, photoluminescence, reactive oxygen species production, antibacterial activity and biocompatibility). Viscoelastic measurements revealed that NGQDs nanoparticles had Young’ modulus of elasticity almost equal to single wall carbon nanotubes (SWCNTs (6,5)). Electrostatic force and scanning tunneling microscopy showed that all types of the NGQDs nanoparticles had negative charge distributed homogeneously. All NGQDs samples produced singlet oxygen and the NGQDs300 sample showed moderate antibacterial activity and good biocompatibility

Comparative study of antimicrobial activity of silica-based nanohybrids functionalized with 5-aminosalicylic acid: toward reduced silver usage

In this study, we report the synthesis, characterization, and antimicrobial evaluation of two silica-based hybrid nanocomposites: SiO2 functionalized with 5-aminosalicylic acid (5-ASA), and its silver-decorated counterpart, SiO2/5-ASA/Ag. The organic ligand 5-ASA was covalently anchored onto the surface of amorphous silica nanoparticles, forming interfacial charge-transfer (ICT) complexes capable of visible-light absorption, as confirmed by UV–Vis diffuse reflectance spectroscopy and supported by DFT/TD-DFT calculations. The subsequent deposition of silver nanoparticles resulted in the formation of plasmonic nanohybrids with enhanced light-harvesting properties. The materials were extensively characterized using FTIR, TGA/DTA, XRD, HRTEM/EDX, and DRS techniques. Their antimicrobial activities were assessed against Escherichia coli, Staphylococcus aureus, and Candida albicans using time-resolved CFU assays at multiple concentrations. Both hybrids demonstrated significant antimicrobial performance; however, notably, the silver-free SiO2/5-ASA sample exhibited potent bactericidal activity, particularly against S. aureus, even at low concentrations. This finding suggests that the presence of –NH2 groups from the 5-ASA ligand contributes to antimicrobial action via interactions with bacterial cell walls, highlighting the potential for silver-free nanomaterials in antimicrobial applications. The results support the development of multifunctional ICT-based nanohybrids with reduced reliance on metallic silver, addressing growing environmental and regulatory concerns

Comparative study on naphthalene degradation by Fe(II)-Activated three different oxidants

Polycyclic aromatic hydrocarbons (PAHs), exemplified by naphthalene (NaP), are prevalent contaminants in mine tailings wastewater owing to their extensive application as flotation reagents in mineral processing. This study systematically investigated the comparative removal efficiency of NaP via Fe(II)-activated oxidants (sodium persulfate (PS), potassium monopersulfate (PMS), and hydrogen peroxide (H2O2)), under optimized reaction conditions. Among the systems research, the Fe(II)/PS system exhibited superior NaP removal efficiency (98.7 %, kobs = 0.0401 min−1) with minimal pH dependence, whereas Fe(II)/PMS and Fe(II)/H2O2 systems showed significant efficiency reduction at higher pH levels. Reactive oxygen species (ROS) type and relative contribution are the primary limitation for NaP removal. And distinct radical species led to divergent degradation pathways: SO4•--dominated systems (Fe(II)/PS and Fe(II)/PMS) favored hydrogen abstraction, while •OH-dominated Fe(II)/H2O2 proceeded via hydroxyl addition. Common anions (Cl− and HCO3−) inhibited degradation across all systems, albeit to varying degrees. All three systems oxidation processes consistently degraded NaP in both ultrapure water and actual mining wastewater, with Fe(II)/PS achieving 96.9 % removal in mine surface water. Additionally, stepwise Fe(II) addition was shown to significantly enhance PS activation and NaP mineralization. In summary, this study provides theoretical insights for Fe(II)/oxidant applications in PAH-contaminated mining wastewater remediation, recommending Fe(II)/PS as a highly efficient and stable approach for NaP degradation

Structural and functional characteristics of β-lactoglobulin/C-phycocyanin/ starch composite gels induced by pressure

High-pressure processing (HPP) has emerged as a key sustainable green alternative for food treatment, effectively preserving food’s sensory and nutritional properties. This study investigated the potential of HPP to develop β-lactoglobulin (BLG) gels in the presence of starch and the bioactive blue protein C-phycocyanin (C-PC). Various compositions of binary (BLG/C-PC and BLG/starch) and ternary (BLG/C-PC/starch) systems were subjected to high-pressure (HP) conditions at 4500 bar. BLG, C-PC, and starch concentrations were maintained at 180, 10, and 5 g/L. HP-induced hydrogels preserve C-PC colour and partial preservation of secondary and tertiary structures, as evidenced by visible absorption and CD spectroscopy. SAXS data at the high-Q range revealed that C-PC induces the unfolding of BLG within binary system gels. In contrast, the ternary system gel maintained the BLG tertiary structure better. C-PC and starch affected the nano and microstructures of BLG HP-induced gels by increasing the pore size, as demonstrated by SAXS (at low Q-range) and SEM analysis. This increase in pore size further influenced the resulting gels’ rheological behaviour and texture profile. C-PC enhanced the protein solubility and antioxidant activity of the HP-induced gels, potentially boosting the bioactive and nutritional value of the developed gels

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

Supporting Information to: "Improving electrochemical aptasensor sensitivity for Bacillus cereus spore detection in food safety applications"

Figure S1. Folded structures for the Apt1, Apt2 and BAS6 aptamers Figure S2. Scanning electron microscopy of B. cereus S51 spores Figure S3. B. cereus spores stained with Textas Red modified aptamers Figure S4. SPGE electrode cleaning with 0.05 M H2SO4 Figure S5. Cyclic Voltammograms recorded in 5 mM ferro/ferricyanide in PBS using SPGEs for each step of electrode functionalization. Figure S6. SEM images of SPGE Figure S7. Spiking Ready-to-Eat salad samples with B. cereus sporesThis is Supporting Information to: Sentic, Milica, Francesco, Rizzotto, Zorica, Novakovic, Aleksandar, Karajic, Brahim, Heddi, Jasmina, Vidic, "Improving electrochemical aptasensor sensitivity for Bacillus cereus spore detection in food safety applications" in Talanta, 299 (2026): 129147, [https://doi.org/10.1016/j.talanta.2025.129147

Electrochemical approaches to glyphosate detection using molecularly imprinted polymer-coated metal-organic frameworks

Glyphosate (GLY) is one of the most commonly used herbicides worldwide. Its widespread use raises significant concerns about public health and ecological integrity, which have led to increased control and oversight of its use, along with a growing demand for rapid and reliable monitoring. This study presents a novel electrochemical sensing platform designed for detecting GLY, utilizing the unique properties of multifunctional rare-earth metal-organic frameworks (RE-MOFs) alongside with the selective recognition capabilities of molecularly imprinted polymer (MIP) technology. The composite formed from yttrium-2-aminoterephthalic acid-based MOF and graphene oxide modifies the surface properties of a glassy carbon electrode (GCE) and serves as a support substrate for the subsequent preparation of the MIP. The crystallinity and flower-like architecture of the resulting composite, were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), while charge-transfer properties and conductivity were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The selection of the appropriate MIP for GLY detection was driven by advanced theoretical calculations, that focused on the interactions between diverse functional monomers and GLY. Theoretical determination of the optimal monomer was followed by experimental optimization of the electropolymerization method for the preparation of MIP/MOF sensors. The resulting sensor demonstrated a wide dynamic linear range (1–16 542 nM) and a subnanomolar detection limit (0.42 nM). It exhibited good specificity and an excellent recovery rate in practical applicability for water samples. The obtained results highlight the potential of the proposed sensing platform for environmental monitoring applications