Ultra-small gold nanoparticles embedded cyclodextrin metal-organic framework composite membrane to achieve antibacterial and humidity-responsive functions.

Cyclodextrin metal-organic framework (CD-MOF) is an edible and porous material that can serve as a template for synthesizing small-sized metal nanoparticles. However, its highly hydrophilic nature has limited its wider application. Herein, ultra-small gold nanoparticles (U-AuNPs) were loaded into CD-MOF to produce a composite material Au@CD-MOF. The CD-MOF was utilized as a template to control the size of the AuNPs. The synthesized Au@CD-MOF was easily dispersible in aqueous medium and its released U-AuNPs exhibited effective water dispersion stability within 120 days. Additionally, compared to gold nanoparticles prepared using traditional methods (T-AuNPs), the U-AuNPs exhibited superior antibacterial properties. Furthermore, hydrophilic Au@CD-MOF was incorporated into a hydrophobic polydimethylsiloxane (PDMS) matrix (Au@CD-MOF/PDMS) to achieve a humidity-responsive antibacterial function. The composite membrane exhibited remarkable responsiveness to humidity, showing almost no release of U-AuNPs at 0 % humidity. However, it exhibited approximately 89 % release within 1 h, and complete release of U-AuNPs was observed within 4 h under 100 % humidity. These findings highlight the successful preparation of a humidity-responsive antibacterial composite membrane, which has great potential applications in various scenarios, particularly in the field of antibacterial food packaging.

Microbiological and chemical hazards in cultured meat and methods for their detection.

Cultured meat, which involves growing meat in a laboratory rather than breeding animals, offers potential benefits in terms of sustainability, health, and animal welfare compared to conventional meat production. However, the cultured meat production process involves several stages, each with potential hazards requiring careful monitoring and control. Microbial contamination risks exist in the initial cell collection from source animals and the surrounding environment. During cell proliferation, hazards may include chemical residues from media components such as antibiotics and growth factors, as well as microbial issues from improper bioreactor sterilization. In the differentiation stage where cells become muscle tissue, potential hazards include residues from scaffolding materials, microcarriers, and media components. Final maturation and harvesting stages risk environmental contamination from nonsterile conditions, equipment, or worker handling if proper aseptic conditions are not maintained. This review examines the key microbiological and chemical hazards that must be monitored and controlled during the manufacturing process for cultured meats. It describes some conventional and emerging novel techniques that could be applied for the detection of microbial and chemical hazards in cultured meat. The review also outlines the current evolving regulatory landscape around cultured meat and explains how thorough detection and characterization of microbiological and chemical hazards through advanced analytical techniques can provide crucial data to help develop robust, evidence-based food safety regulations specifically tailored for the cultured meat industry. Implementing new digital food safety methods is recommended for further research on the sensitive and effective detection of microbiological and chemical hazards in cultured meat.

Stress response of Salmonella Newport with various sequence types toward plasma-activated water: Viable but nonculturable state formation and outer membrane vesicle production.

This study aims to investigate the response of Salmonella Newport to plasma-activated water (PAW), a novel disinfectant that attracts attention due to its broad-spectrum antimicrobial efficacy and eco-friendliness. In this work, we demonstrated that S. Newport of different sequence types (STs) could be induced into the viable but nonculturable (VBNC) state by PAW treatment. Notably, a remarkable 99.96% of S. Newport ST45 strain entered the VBNC state after a 12-min PAW treatment, which was the fastest observed among the five S. Newport STs (ST31, ST45, ST46, ST166, ST2364). Secretion of outer membrane vesicles was observed in ST45, suggesting a potential strategy against PAW treatment. Genes related to oxidative stress (sodA, katE, trxA), outer membrane proteins (ompA, ompC, ompD, ompF) and virulence (pagC, sipC, sopE2) were upregulated in the PAW-treated S. Newport, especially in ST45. A reduction of 38-65% in intracellular ATP level after PAW treatment was observed, indicating a contributor to the formation of the VBNC state. In addition, a rapid method for detecting the proportion of VBNC cells in food products based on pagC was established. This study contributes to understanding the formation mechanism of the VBNC state in S. Newport under PAW stress and offers insights for controlling microbial risks in the food industry.

Synthesis of UiO-66 loaded-caffeic acid and study of its antibacterial mechanism.

The Zirconium-based metal-organic framework (UiO-66) has become important in the field of natural compounds delivery for its high drug loading capacity. Caffeic acid (CA) is a natural compound with unsatisfactory physicochemical stability. CA@UiO-66 improved the stability of CA and inhibited the growth of bacteria. UiO-66 was prepared by water-assisted method for the encapsulation of CA. CA@UiO-66 showed the highest CA loading rate of 56 % and a sustained-release ability of CA of 83 % until 100 h. It destroyed the surface morphology and ultrastructure of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The minimum bactericidal concentration (MBC) for E. coli and S. aureus were 1.0 mg/mL and 2.0 mg/mL, respectively. The 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl-tetrazolium bromide (MTT) colorimetry showed that the CA@UiO-66 had low toxicity or no toxicity to human normal liver cells LO2 at the concentration of MBC. Therefore, CA@UiO-66 has a potential in the field of food microbial safety.

Cyclodextrin metal-organic framework by ultrasound-assisted rapid synthesis for caffeic acid loading and antibacterial application.

Cyclodextrin metal-organic framework by ultrasound-assisted rapid synthesis for caffeic acid (CA) loading and antibacterial application (U-CD-MOF) was successfully studied and this method shortened the preparation time to a few minutes. It was found that the ultrasonic power, reaction time and temperature would affect the morphology and size of the obtained crystal. Under the optimal conditions, U-CD-MOF had a cubic structure with uniform size of 8.60 ± 1.95 µm. U-CD-MOF was used to load the antibacterial natural product CA to form the composite (CA@U-CD-MOF) and the loading rate of CA@U-CD-MOF to CA could reach 19.63 ± 2.53%, which was more than twice that of γ-CD. Various techniques were applied to characterize the synthesized crystal, including Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2 adsorption. In addition, antibacterial tests were performed on the obtained crystal. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CA@U-CD-MOF for Escherichia coli O157: H7 (E. coli O157: H7) were both 25 mg·mL-1, and the MIC for Staphylococcus aureus (S. aureus). was 25 mg·mL-1. The sustained release behavior of CA@U-CD-MOF to CA in ethanol fitted well to Higuchi model and the loading of CA was supported by molecular docking results. In general, U-CD-MOF was successfully achieved by ultrasound-assisted rapid synthesis and the obtained crystal was further evaluated for potential antibacterial application.

Polydimethylsiloxane Membranes Incorporating Metal-Organic Frameworks for the Sustained Release of Antibacterial Agents.

Cyclodextrin metal-organic frameworks (CD-MOFs) possess great potential in environmental applications due to their high specific surface area and good biocompatibility properties. However, the hydrophilicity of the CD-MOF hinders its ability to maintain a sustained release in water as a carrier. In this study, we prepared a CD-MOF that has codelivery ability for both phytochemicals [caffeic acid (CA)] and silver nanoparticles (Ag NPs) and further incorporated this material (CA@Ag@CD-MOF) into the polydimethylsiloxane (PDMS) matrix to construct a hybrid membrane. This hybrid membrane could effectively maintain the release capacity of the CD-MOF in water, while endowing PDMS with swelling ability in water. The hybrid membrane can achieve a sustained release for up to 48 h in water. In addition, the elastic modulus of the hybrid membrane increases by nearly 100%, and the swelling degree of the hybrid membrane in water increases by 42% compared with that of the pure PDMS membrane, indicating better mechanical properties. The hybrid membrane exhibits excellent antibacterial effects on Escherichia coli O157:H7 (E. coli O157:H7) and Staphylococcus aureus (S. aureus). We expect that this work will be beneficial to the delivery research of the CD-MOF in more environmental scenarios, especially in water treatment.

Antibacterial applications of metal-organic frameworks and their composites.

Metal-organic frameworks (MOFs) are porous coordination materials composed of multidentate organic ligands and metal ions or metal clusters. MOFs have the great potential to be utilized in antibacterial materials for biological, environmental, and food antimicrobial fields. In recent years, MOFs have been applied to various antibacterial fields due to their sustained release capability, porosity, and structural flexibility in combination with many chemicals and/or materials (such as nanoparticles, antibiotics, phytochemicals, and polymers). This review offers a detailed summary of the antibacterial applications of MOFs and their composites, focusing on the combination types of MOFs composites and the antibacterial effect in different applications. These applications are illustrated by the examples discussed in this review.

A SERS aptasensor for simultaneous multiple pathogens detection using gold decorated PDMS substrate.

An aptamer-based sensitive method was developed here for detection of multiple foodborne pathogens in food matrix by surface-enhanced Raman scattering (SERS) technology. Polydimethylsiloxane (PDMS) film was first prepared and then coated with gold nanoparticles (AuNP) to act as an active substrate for the enhancement of Raman scattering. The as-prepared Au-PDMS film was functionalized with specific pathogen aptamers (Apt) to capture the targets. In addition, aptamers functionalized AuNP integrated with Raman reporters (4-Mercaptobenzoic acid (4-MBA)/Nile blue A (NBA)) were fabricated as pathogen-specific SERS probes. In this scheme, pathogens were first captured by Apt-Au-PDMS film and then bind with SERS probes to allow the formation of a sandwich assay to complete the sensor module for the detection of multiple pathogens. With Vibrio parahaemolyticus and Salmonella typhimurium as model targets, this protocol can selectively detect 18 cfu/mL and 27 cfu/mL, respectively. Furthermore, this platform can be successfully applied to detect pathogens in seafood samples with recoveries ranging from 82.9% to 95.1%.

Surface-enhanced Raman spectroscopic single step detection of Vibrio parahaemolyticus using gold coated polydimethylsiloxane as the active substrate and aptamer modified gold nanoparticles.

A method is described for single-step detection of V. parahaemolyticus in seafood via aptamer-based SERS. A gold-coated polydimethylsiloxane (PDMS) film was used for the enhancement of Raman scattering. The Raman reporter 4-mercaptobenzoic acid was linked to aptamer modified gold nanoparticles (AuNPs) served as a signalling probe. The negatively charged signalling probe was assembled onto the cysteamine-modified Au-PDMS film through electrostatic adsorption. On addition of V. parahaemolyticus, it will be bound by the aptamer as a biorecognition element, and this leads to the dissociation of the signalling probe from the Au-PDMS film. Hence, the Raman signal (at 1592 cm-1) decreases. The assay has a wide linear response that covers the 1.2 × 102 to 1.2 × 106 cfu·mL-1 V. parahaemolyticus concentration range. The detection limit is 12 cfu·mL-1. The method was successfully applied to the determination of V. parahaemolyticus in oyster and salmon samples. Graphical abstract Schematic presentation of a surface-enhanced Raman spectroscopic method for single step detection of Vibrio parahaemolyticus using gold coated polydimethylsiloxane as the active substrate and aptamer modified gold nanoparticles. This solid substrate simplified the analysis procedures and enhanced the sensitivity.

Selection, Identification, and Binding Mechanism Studies of an ssDNA Aptamer Targeted to Different Stages of E. coli O157:H7.

Enterohemorrhagic Escherichia coli O157:H7 ( E. coli O157:H7) is known as an important food-borne pathogen related to public health. In this study, aptamers which could bind to different stages of E. coli O157:H7 (adjustment phase, log phase, and stationary phase) with high affinity and specificity were obtained by the whole cell-SELEX method through 14 selection rounds including three counter-selection rounds. Altogether, 32 sequences were obtained, and nine families were classified to select the optimal aptamer. To analyze affinity and specificity by flow cytometer, an ssDNA aptamer named Apt-5 was picked out as the optimal aptamer that recognizes different stages of E. coli O157:H7 specifically with the Kd value of 9.04 ± 2.80 nM. In addition, in order to study the binding mechanism, target bacteria were treated by proteinase K and trypsin, indicating that the specific binding site is not protein on the cell membrane. Furthermore, when we treated E. coli O157:H7 with EDTA, the result showed that the binding site might be lipopolysaccharide (LPS) on the outer membrane of E. coli O157:H7.