Search Results (447)

This study presents the development of a smart packaging material utilizing garlic-derived nitrogen-doped carbon dots (CDs) integrated into a whey protein–starch (WP-S) emulsion. The research aimed to create a real-time, non-invasive biosensor capable of detecting microbial spoilage. The synthesized CDs demonstrated strong pH-sensitive photoluminescence, exhibiting distinct changes in CIE coordinates and fluorescence intensity in response to varying pH values. The WP-S-CDs emulsion was tested against E. coli, S. aureus, and C. albicans. The results showed that the composite film provided a clear colorimetric shift and fluorescence quenching, both of which are directly correlated with microbial metabolic activity. The physical and electronic properties of the composite were investigated to understand the sensing mechanism. Scanning electron microscopy (SEM) of the dried film revealed that the WP-S-CDs system formed a more porous structure with larger pore sizes (3.63–8.18 µm) compared to the control WP-S film (1.62–6.52 µm), which facilitated the rapid diffusion of microbial metabolites. Additionally, density functional theory (DFT) calculations demonstrated that the incorporation of CDs significantly enhanced the composite’s electronic properties by reducing its band gap and increasing its dipole moment, thereby heightening its reactivity and sensitivity to spoilage byproducts. In a practical application on apples, the WP-S-CDs coating produced a visible red spot, confirming its function as a dynamic sensor. The material also showed a dual-action antimicrobial effect, synergistically inhibiting C. albicans while exhibiting an antagonistic effect against bacteria. These findings validate the potential of the WP-S-CDs emulsion as a powerful, multi-faceted intelligent packaging system for food quality monitoring. Full article

Magneto-photoluminescent hybrid materials (MPHMs) were prepared by incorporating cobalt ferrite nanoparticles (CFNs) into the fluorescent polymer poly(terephthalaldehyde-undecan-2-one) (PT2U). The CFNs, with a mean size of 3.95 nm, formed aggregates within the PT2U matrix (650–1042 nm) due to surface and interfacial interactions, modulating aggregate morphology and interparticle coupling. Magnetization studies revealed non-monotonic variations in saturation magnetization (30.3–16.2 emu/g), mean blocking temperature (39.3–43.1 K) and effective magnetic anisotropy energy density (2.14 × 10⁶–1.31 × 10⁶ erg/cm³) with increasing CFN content, consistent with the presence of canted surface spins and enhanced magnetizing interparticle interactions. Photoluminescence exhibited progressive quenching, dominated by collisional mechanisms at low CFN content and by interfacial CFN–PT2U interactions at higher loadings. Under a magnetic field (800 Oe), additional quenching occurred, attributed to magnetically induced polymer-chain rearrangements that disrupted the molecular stacking required for efficient aggregation-induced emission. These results demonstrate tunable magneto-photoluminescent coupling in MPHMs governed by surface and interfacial phenomena, providing insights for the design of functional and responsive hybrid materials. Full article

The inhibitory effects of natural cellulose (NC), microcrystalline cellulose (MC), and soluble fiber dextrin (SC) on amylase activity have been established; however, the underlying mechanisms remain poorly understood. This study employed fluorescence spectroscopy and fluorescence thermodynamics to investigate the quenching parameters, thermodynamic properties, and quenching mechanisms of cellulose interactions with α-amylase and amyloglucosidase. Structural alterations in both enzymes were examined using synchronous fluorescence and UV–visible absorption spectroscopy. The results indicated that NC, MC, and SC primarily induced static quenching of fluorophores in α-amylase and amyloglucosidase. When addition of SC reached 3%, SC reduced the fluorescence intensity of tyrosine and tryptophan residues in α-amylase by 70.9% and 86.8%, and in amyloglucosidase by 43.7% and 46.5%, respectively. Increasing SC levels also decreased hydrophobicity around tyrosine and tryptophan in α-amylase. These findings provide insights into designing cellulose-based amylase inhibitors through structural modulation for developing low-glycemic index (GI) foods. Full article

This study employed deep eutectic solvents (DES) combined with ultrasonic-assisted extraction technology to green and efficiently extract flavonoids from honeysuckle, and systematically evaluated its inhibitory mechanism on α-amylase (α-AMY). Through comparative screening of six DES systems and traditional solvents, DES-4 (Choline chloride–propylene glycol) was identified as the optimal extraction solvent. After single-factor and response surface optimization, the yield of honeysuckle flavonoids (HF) was significantly increased to 9.12 ± 0.08% under the conditions of ultrasonic power 300 W, solid–liquid ratio 1:32 (g/mL), and extraction time 60 min. HPLC-MS analysis revealed that luteolin (4.59 ± 0.09 mg/g) and quercetin (3.05 ± 0.02 mg/g) were the main active components, and they exhibited strong antioxidant activity. Enzyme kinetics and Lineweaver–Burk analysis indicated that the inhibition type of HF on α-AMY was reversible mixed inhibition. Fluorescence spectroscopy, thermodynamic analysis, and molecular docking results further revealed that HF primarily bound to α-AMY through hydrogen bonds and van der Waals forces (ΔH = −63.80 kJ/mol, ΔS = −0.19 J/mol·K), causing static fluorescence quenching and altering its hydrophobic microenvironment and spatial conformation. This study aims to provide new theoretical basis for the green and efficient extraction of HF and its development and application in functional foods and natural medicines. Full article

The desiccation tolerant moss Hedwigia ciliata was investigated to assess its early reaction to water stress in controlled conditions. Thus, various photosynthetic parameters and water contents were studied during a selected time frame within 48 h of two main events, namely water loss after full hydration and activity (preparation for anabiosis) and water uptake after the state of anabiosis. The observations of the changes in the photosynthetic efficiency of Hedwigia ciliata in response to fluctuating relative water contents (RWCs) during rehydration and dehydration periods provide valuable insights into the species’ physiological adaptation mechanisms. Hedwigia ciliata rapidly uptakes water upon anabiosis, and despite being poikilohydric, it is able to retain water for a prolonged period compared to the water availability in its immediate environment. The delayed decrease in relative water content (RWC) corresponds to the photosynthetic parameters and preparation for anabiosis, including the maintenance of photosystems and general cell integrity. The low values of non-photochemical quenching during desiccation imply limited photoinhibition and effective photoprotective regulation. Conversely, the rather high values of the fluorescence decline ratio during rehydration reflect the efficient recovery of photosynthetic performance. The postponed physiological shutdown while drying and photosynthetic activity in the early dehydration phase suggest anticipatory acclimation to desiccation, i.e., non-active phase anabiosis. Hedwigia ciliata is a desiccation-tolerant moss, with anatomical, morphological, and eco-physiological adaptations, making it a useful model species in drought and abiotic stress studies of bryophytes in a rapidly changing environment. Full article

Translating the exceptional luminescent properties of AIEgens into efficient and practical sensing devices has long been a major challenge restricting their practical application. In this work, we demonstrate a novel strategy based on phase separation to fabricate stable, high-surface-area sensing films that address the fluorescence quenching typically associated with conventional nanospheres. Fluorescent polysiloxanes bearing tetraphenylphenyl (TPP) side groups were synthesized and processed into fibrous films via electrospinning. Leveraging the intrinsic incompatibility of the polymer, entropy-driven phase separation generated an “sea–island” morphology. This hierarchical structure significantly enlarged the specific surface area and facilitated analyte diffusion, thereby improving the accessibility of active sites. Molecular dynamics simulations not only predicted the formation of this architecture but also clarified the underlying entropy-driven mechanism. Overall, this work provides a solid foundation and conceptual framework for investigating how quantitative regulation of lumogenic unit density and spatial distribution governs sensing performance. Full article

Phytoremediation utilizing woody plants represents a promising approach for mitigating cadmium (Cd) contamination; however, the potential of ornamental species such as Punica granatum L. (pomegranate) remains insufficiently characterized. This study evaluated the growth performance, physiological responses, and Cd accumulation patterns of pomegranate seedlings exposed to increasing Cd concentrations (T1–T6) in a hydroponic system. High Cd levels (≥T4) markedly suppressed plant growth, as evidenced by reductions in biomass, root necrosis, leaf wilting, and chlorosis. Photosynthetic efficiency was severely compromised, indicated by significant declines in chlorophyll content and key chlorophyll fluorescence parameters (Fv/Fm, ΦPSII, and qP). Simultaneously, increases in the chlorophyll a/b ratio, carotenoid content, and non-photochemical quenching (NPQ) reflected the activation of photoprotective mechanisms. A reduction in stomatal conductance (G_s) and net photosynthetic rate (P_n), coupled with elevated intercellular CO₂ concentration (C_i), suggested that non-stomatal limitations were primarily responsible for photosynthetic inhibition. Cd exposure also triggered oxidative stress, as shown by increased levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂). In response, seedlings activated antioxidative and osmotic adjustment pathways, including elevated peroxidase (POD) activity and the accumulation of glutathione (GSH), proline, soluble proteins, and sugars. Notably, pomegranate displayed a root-based Cd sequestration strategy, with high root accumulation (bioconcentration factor, BCF > 271) and minimal translocation to aerial tissues (translocation factor, TF < 0.17). These findings demonstrate that pomegranate seedlings exhibit pronounced tolerance to Cd stress and substantial bioaccumulation capacity, supporting their potential application as ornamental woody species for phytoremediation of Cd-contaminated environments. Full article

The combination of antimicrobial agents with different mechanisms of action is an important step in the fight against drug-resistant microorganisms. In this study, the interaction of the lysozyme enzyme with ampicillin and colistin was investigated. These antibiotics are highly effective against Gram-positive (ampicillin) and Gram-negative (colistin) pathogenic microorganisms. Spectroscopic and kinetic methods and molecular docking were used in the research. The results of the spectroscopic analysis confirmed the intermolecular interaction of lysozyme with ampicillin or colistin. The formation of the lysozyme complex with ampicillin was accompanied by mixed quenching of the enzyme fluorescence and changes in its secondary structure (a slight decrease in the content of α-helices). The interaction of lysozyme with colistin was complemented by dynamic quenching of the enzyme fluorescence. The method of molecular docking established that the interactions of lysozyme with colistin were predominantly van der Waals, while hydrogen bonds predominated in the lysozyme complex with ampicillin. Despite the presence of interactions of ampicillin and colistin with amino acid residues from the active site of lysozyme, this did not affect its ability to cause destruction of bacterial cell walls. The results obtained can be used in the development of antibacterial drugs. Full article

The non-oxidizing antimicrobial 2-Methyl-4-Isothiazolin-3-one (MIT) poses a significant environmental risk given its frequent detection in municipal wastewater. This study showed that the combination of Vacuum UV/UV (VUV/UV) and persulfate (PDS) efficiently achieved the rapid transformation and removal of 10 μM MIT within 90 s, which is much faster than UV, UV/PDS, and VUV/UV. Increasing the PDS dosage improved MIT degradation, whereas changes in pH between 4 and 10 had little effect. Radical quenching experiments showed that 93% of the MIT oxidation was attributable to the hydroxyl radical (•OH) and the sulfate radical (SO₄•⁻). SO₄•⁻ and •OH at concentrations of 8.6 × 10⁻¹² M and 1.5 × 10⁻¹² M accounted for 32% and 61% of the MIT degradation, respectively, and the greater contribution of •OH was attributed to its higher reaction rate constant with MIT compared to SO₄•⁻. Sulfate had a negligible impact on the radical concentrations. Chloride (1 mM) reduced the SO₄•⁻ and •OH concentrations by 61% and 27%, respectively. And the SO₄•⁻ contribution to MIT degradation fell to 19%. Nitrate (5 mM) readily quenched •OH but minimally affected SO₄•⁻. The •OH concentration decreased by 79%, reducing its contribution to 27%. Bicarbonate/carbonate (5 mM) simultaneously reduced the SO₄•⁻ and •OH by 26–30% and had little effect on their contributions. Because of the quenching effect of organic matter and inorganic anions on radicals, secondary effluent inhibited the degradation of MIT. After a 120 s treatment, the total organic carbon, UV₂₅₄, and fluorescence regional integration were reduced by 5%, 8%, and 17–24%, respectively. This study provides a quantitative analysis of how inorganic ions alter the concentrations and contributions of •OH and SO₄•⁻, elucidating the MIT removal mechanisms in VUV/UV/PDS for sustainable wastewater reclamation. Full article

Metal-organic frameworks (MOFs), a class of crystalline porous materials featuring a high specific surface area, tunable pore structures, and functional surfaces, exhibit remarkable potential in fluorescent sensing. This review systematically summarizes recent advances in the construction strategies, sensing mechanisms, and applications of MOF-based fluorescent sensors. It begins by highlighting the diverse degradation pathways that MOFs encounter in practical applications, including hydrolysis, acid/base attack, ligand displacement by coordinating anions, photodegradation, redox processes, and biofouling, followed by a detailed discussion of corresponding stabilization strategies. Subsequently, the review elaborates on the construction of sensors based on individual MOFs and their composites with metal nanomaterials, MOF-on-MOF heterostructures, covalent organic frameworks (COFs), quantum dots (QDs), and fluorescent dyes, emphasizing the synergistic effects of composite structures in enhancing sensor performance. Furthermore, key sensing mechanisms such as fluorescence quenching, fluorescence enhancement, Stokes shift, and multi-mechanism coupling are thoroughly examined, with examples provided of their application in detecting biological analytes, environmental pollutants, and food contaminants. Finally, future directions for MOF-based fluorescent sensors in food safety, environmental monitoring, and clinical diagnostics are outlined, pointing to the development of high-performance, low-cost MOFs; the integration of multi-technology platforms; and the construction of intelligent sensing systems as key to enabling their practical deployment and commercialization. Full article

This study presents a novel ratiometric fluorescent sensor based on Förster resonance energy transfer (FRET) between glutathione (GSH)-coated CdTe quantum dots (CdTe/GSH QDs) and bovine serum albumin (BSA)-coated Au nanoclusters (AuNCs/BSA) for dopamine (DA) detection. The nanoparticles were characterized using transmission electron microscopy (TEM), zeta potential measurements, Fourier transform infrared (FTIR) spectroscopy, UV-Vis absorption and fluorescence spectroscopy. Key FRET parameters, including energy transfer efficiency (E), donor–acceptor distance (r), Förster distance (R₀), and the overlap integral (J), were determined. The interactions between the CdTe/GSH-AuNCs/BSA conjugate and DA were investigated, revealing a dual mechanism of QDs fluorescence quenching that involves both energy and electron transfer. The average lifetime values and spectral profiles of CdTe/GSH QDs, both in the absence and presence of DA, suggest a dynamic fluorescence quenching process. The variation in the ratiometric signal with increasing DA concentration demonstrated a linear response within the range of 0–250 µM, with a correlation coefficient of 0.9963 and a detection limit of 6.9 nM. This proposed nanosensor exhibited selectivity against potential interfering substances, including urea, glucose, BSA, GSH, citric acid, and metal ions such as Na⁺ and Ca²⁺. The conjugate also demonstrates excellent cytocompatibility and enhances cell proliferation in HeLa epithelial cells, making it suitable for biological applications. It was successfully employed for DA detection in urine samples, achieving recoveries ranging from 99.1% to 104.2%. The sensor is highly sensitive, selective, rapid, and cost-effective, representing a promising alternative for DA detection across various sample types. Full article

Corbicula fluminea protein (CFP) and cyanidin-3-O-glucoside (C3G) are natural nutrient fortifiers. During consumption or processing, they may interact with each other, inducing alternations in their structural and functional properties. However, nothing was known about the mechanism of their interaction and their synergistic antioxidant effect. In this research, C3G was physically mixed with CFP to simulate practical scenarios. The impact of the presence of C3G on the multispectral characteristics, antioxidant activity, and particle properties of CFP was examined and compared to chemically fabricated C3G-CFP covalent conjugates. The results indicate that C3G tended to spontaneously bind to CFP and formed compact non-covalent complex, with hydrophobic forces predominantly governing the interaction. This binding resulted in the statically quenched intrinsic fluorescence of CFP, accompanied by a dynamic model. Moreover, C3G preferentially induced Trp residue in CFP exposed to a more polar microenvironment, yet it exerted nearly no effects on CFP when analyzed using ultraviolet–visible (UV-Vis) spectroscopy and synchronous fluorescence spectroscopy (SFS). Additionally, although the formed non-covalent complex demonstrated strengthened antioxidant capacity, C3G displayed an antagonistic effect with CFP, whereas lower C3G concentrations led to synergistic effects in covalent conjugates. These findings provide new insights into the effective application of C3G and CFP as nutritional antioxidants. Full article

Sunset yellow (SY) is a synthetic azo dye widely used in food and cosmetics. However, concerns have been raised about its potential health risks, including its nephrotoxicity and genotoxicity, when used in excessive amounts. Illegal addition of SY may cause allergic reactions or genetic damage. Therefore, a rapid method for detecting SY is needed. To develop a rapid detection method for sunset yellow (SY) with the aim of preventing its illegal addition in food, this study utilized agricultural waste asparagus peel (AP) as a carbon source and synthesized amino-functionalized carbon quantum dots (AP-CDs) via a green hydrothermal method. A highly sensitive detection platform was established based on the fluorescence quenching mechanism of AP-CDs in the presence of SY. The microstructure of AP-CDs was characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Their optical properties were assessed via ultraviolet–visible absorption spectroscopy (UV-vis) and fluorescence spectroscopy (FS). Furthermore, key experimental parameters affecting SY detection were systematically optimized. Results revealed that the synthesized AP-CDs possessed surface hydrophilic functional groups, including hydroxyl, amide, and carboxyl groups, and were composed of carbon (C), oxygen (O), and nitrogen (N) elements. Optical performance studies demonstrated that AP-CDs exhibited a strong fluorescence emission at 470 nm under 380 nm excitation, with a quantum yield (Φ) of 15.9%. Under the optimized conditions (pH 7.0, 0.5 mg/mL AP-CDs), the fluorescence intensity showed a linear response to the concentration of SY over the range of 0.1 to 100 μM (R² = 0.9929), achieving a detection limit of 0.92 μM. This strategy not only enables sustainable resource utilization but also provides a sensitive and practical approach for food safety monitoring, demonstrating significant potential for real-world applications. Full article

We aimed to investigate the interaction mechanism of transport protein Human serum albumin (HSA) with a synthesized compound, QP-11, with tested antimalarial properties to monitor the changes in the protein because of QP-11 binding. The interaction between the antimalarial compound QP-11 and HSA was thoroughly investigated through a multidimensional approach, utilizing UV-VIS spectroscopy, fluorescence, time-resolved fluorescence, and CD (Circular dichroism), alongside molecular docking techniques. Our findings unveiled a robust 1:1 binding pattern, signifying a strong affinity between QP-11 and HSA. Employing static quenching, evidenced by time-resolved fluorescence spectroscopy, QP-11 was observed to induce fluorescence quenching of HSA, particularly binding to subdomain IIA. Thermodynamic parameters indicated that van der Waals forces and hydrogen bonding predominantly facilitated the binding, with increased temperature compromising complex stability. The 3D fluorescence and CD results demonstrated QP-11-induced conformational changes in HSA. Both experimental and in silico analyses suggested a spontaneous, exothermic binding reaction. The profound impact of the QP-11–HSA interaction underscores the potential for QP-11 in antimalarial drug development, encouraging further exploration for dose design and enhanced pharmacodynamic and pharmacokinetic properties. Full article

In this study, blue fluorescence carbon dots of high quantum yield (42.96%) were successfully synthesized via a one-step hydrothermal method using Pueraria residues as the precursor and urea as the nitrogen source. The preparation process was simple, was environmentally friendly, and did not use toxic chemicals, with the resulting nitrogen-doped Pueraria carbon dots (N-PCDs) exhibiting excellent dispersibility, regular morphology and stable fluorescence performance. Moreover, fluorescence quenching could be induced through electron transfer between N-PCDs and hexavalent chromium (Cr(VI)) in water, which enabled the application of N-PCDs as a fluorescent probe for sensing Cr(VI) in water, with a limit of detection (LOD) and limit of quantitation (LOQ) of 0.078 μM and 0.26 μM, respectively. The effectiveness of the proposed fluorescent probe was also validated in various water matrices, achieving stable recovery rates ranging from 98.7% to 101.5%. Furthermore, experimental investigations and theoretical calculations through density functional theory (DFT) confirmed that the underlying reaction mechanism was photoinduced electron transfer (PET). Above all, this study not only demonstrated the potential of N-PCDs as sensitive probes to sense toxic elements in the environment, but also promotes the green and scalable production of high-value carbon-based products from waste biomass. Full article