Plant-mediated green synthesis is a cost-effective and eco-friendly process used to synthesize metallic nanoparticles. Experimental pH is of interest due to its ability to influence nanoparticle size and shape; however, little has been explored in comparison to the influence of this parameter on the therapeutic potential of resultant metallic nanoparticles. Our work investigated the influence of pH alternation on antimicrobial properties of plant-mediated green synthesized (using Spinacia oleracea leaf extract) silver nanoparticles. We further investigated if the antimicrobial activity was sustained at 8 weeks (after initial green synthesis). Antimicrobial properties were evaluated against Escherichia coli, Staphylococcus aureus, and Candida albicans. Our work confirmed that experimental pH in plant-mediated green synthesis of silver nanoparticles influenced their resultant antimicrobial properties. Silver nanoparticles generated at experimental pH 4.5, and nine showed activity against E. coli which was sustained at various levels over 8 weeks. No antimicrobial activity was observed against S. aureus, and weak antimicrobial activity against C. albicans. These interesting findings highlight the importance of experimental pH. Further understanding of the role experimental pH plays on resultant metallic nanoparticle properties as it relates to biological and therapeutic impact is required, which will have an impact on wider applications beyond antimicrobial activity.

Antibiotic resistance is a major threat to public health, which contributes largely to increased mortality rates and costs in hospitals. The severity and widespread nature of antibiotic resistance result in limited treatments to effectively combat antibiotic-resistant pathogens. Nanoparticles have different or enhanced properties in contrast to their bulk material, including antimicrobial efficacy towards a broad range of microorganisms. Their beneficial properties can be utilised in various bioengineering technologies. Thus, antimicrobial nanoparticles may provide an alternative to challenge antibiotic resistance. Currently, nanoparticles have been incorporated into materials, such as fibres, glass and paints. However, more research is required to elucidate the mechanisms of action fully and to advance biomedical applications further. This paper reviews the antimicrobial efficacies and the intrinsic properties of different metallic nanoparticles, their potential mechanisms of action against certain types of harmful pathogens and how these properties may be utilised in biomedical and healthcare products with the aim to reduce cross contaminations, disease transmissions and usage of antibiotics.

With the rise of antibiotic resistance, the drive to discover novel antimicrobial substances and standard testing methods with the aim of controlling transmissive diseases are substantially high. In healthcare sectors and industries, although methods for testing antibiotics and other aqueous-based reagents are well established, methods for testing nanomaterials, non-polar and other particle-based suspensions are still debatable. Hence, utilities of ISO standard validations of such substances have been recalled where corrective actions had to be taken. This paper reports a serial analysis obtained from testing the antimicrobial activities of 10 metallic-based nanomaterials against 10 different pathogens using five different in vitro assays, where the technique, limitation and robustness of each method were evaluated. To confirm antimicrobial activities of metallic-based nanomaterial suspensions, it was found that at least two methods must be used, one being the agar well diffusion method, which was found to be the most reliable method. The agar well diffusion method provided not only information on antimicrobial efficacy through the size of the inhibitory zones, but it also identified antimicrobial ions and synergistic effects released by the test materials. To ascertain the effective inhibitory concentration of nanoparticles, the resazurin broth dilution method is recommended, as MIC can be determined visually without utilising any equipment. This method also overcomes the limit of detection (LoD) and absorbance interference issues, which are often found in the overexpression of cell debris and nanoparticles or quantum dots with optical profiles. In this study, bimetallic AgCu was found to be the most effective antimicrobial nanoparticle tested against across the bacterial (MIC 7 µg/mL) and fungal (MIC 62.5 µg/mL) species.

The recently emerged coronavirus pandemic (COVID-19) has become a worldwide threat affecting millions of people, causing respiratory system related problems that can end up with extremely serious consequences. As the infection rate rises significantly and this is followed by a dramatic increase in mortality, the whole world is struggling to accommodate change and is trying to adapt to new conditions. While a significant amount of effort is focused on developing a vaccine in order to make a game-changing anti-COVID-19 breakthrough, novel coronavirus (SARS-CoV-2) is also developing mutations rapidly as it transmits just like any other virus and there is always a substantial chance of the invented antibodies becoming ineffective as a function of time, thus failing to inhibit virus-to-cell binding efficiency as the spiked protein keeps evolving. Hence, controlling the transmission of the virus is crucial. Therefore, this review summarizes the viability of coronaviruses on inanimate surfaces under different conditions while addressing the current state of known chemical disinfectants for deactivation of the coronaviruses. The review attempts to bring together a wide spectrum of surface–virus–cleaning agent interactions to help identify material selection for inanimate surfaces that have frequent human contact and cleaning procedures for effective prevention of COVID-19 transmission.

The transmission of pathogenic bioaerosols poses a substantial risk not only to human health but also to animal welfare and agricultural productivity, where the spread of infections can lead to significant economic and public health system burdens. This underscores the importance of developing reliable aerosol sampling techniques that can capture airborne particles.Electrostatic precipitation (ESP) is a promising method for aerosol collection1. However, its dependence on corona discharge to charge particles generates ozone byproducts. The presence of ozone can compromise the integrity of bioaerosols2. This is problematic in applications where preserving the viability of the collected bioaerosols is essential, such as those requiring cultivation. Therefore, to address this limitation whilst keeping the advantages of ESP-based techniques, ozone-free (i.e. corona discharge-free) electrostatic actuation was investigated as a potential alternative.Indium tin oxide (ITO)-coated microscope slides (Diamond Coatings) were electrically connected to four different electrical conditions: negative, positive, grounded, and floating (no connection) in an 8 m3 aerosol test chamber. Voltages between -10kV to +10kV were applied. 1 µm diameter fluorescent polystyrene microspheres (PSL) were used as model aerosolised particles. Four optical particle counters (OPC-N3, Alphasense) were positioned in the vicinity of the slides to continuously monitor aerosol concentration. For each experiment, aerosols were nebulised for 15 minutes, followed by a 10-minute sampling period during which voltages were applied. Afterwards, the chamber was cleaned using an extraction system equipped with HEPA filter, and then the samples were retrieved for imaging using an EVOSM700 fluorescence microscope. Particle counts were obtained using Celeste 6 analysis software and normalised against the chamber concentration. To direct the particle flow towards the slide, aiming to enhance the collection efficiency, a fan-assisted collection device was constructed to direct airflow onto the slide (Fig 1a). Fan speed and spatial placement were varied to optimise collection efficiency.Ozone-free electrostatic collection of PSL particles was successfully demonstrated, with both positive and negative biases collecting up to 17.0 and 8.5 times more PSL particles than the grounded and floating slides, respectively. A correlation was observed between applied voltage and collection performance, as higher voltages generated stronger electric fields, thereby enhancing the electrostatic force and particle capture. The simple fan-driven collection device achieved an initial collection efficiency of 31.5%. Investigation into fan speed and spatial positioning revealed that lower fan speeds and a closer fan-to-collection-medium distance performed better, with the highest collection efficiency at 59.1% at 10.9 L/min air flow rate (lower speed setting) (Fig 1b).These findings demonstrate that ozone-free electrostatic collection is an effective alternative approach to the ESP-based method for aerosol collection, with the potential of maintaining bioaerosol viability, which will be tested in the near future to confirm. Overall, the results establish a foundation for advancing electrically actuated aerosol collection devices and highlight promising future applications in public health surveillance, environmental bioaerosol monitoring, and agricultural biosecurity.This work was supported by Research England-funded Biodetection Technologies Hub and the Engineering and Physical Sciences Research Council [grant number EP/X017591/1].References: [1] Foat et al. (2016), [2] Ouyang et al. (2023).

Bimetallic nanomaterials that couple catalytic reactivity with light-responsive behaviour provide a promising route for multifunctional antimicrobial materials. Here, we report Cu–Au core–nanocluster nanostructures that integrate a cost-effective Cu core with ultrafine Au clusters to form an interface-engineered antimicrobial platform. Density functional theory shows that Cu–Au interfacial sites lower O–O bond dissociation barriers and enhance charge transfer, enabling efficient catalytic generation of reactive oxygen species (ROS). Experimentally, the nanostructures exhibit enhanced Cu2+ release relative to Cu alone, consistent with galvanic coupling, and demonstrate strong antimicrobial activity under dark conditions, confirming a ROS- and ion-mediated mechanism. Under visible-light irradiation, photothermal simulations and measurements show localised heating to ~60 °C at particle densities an order of magnitude lower than conventional Au nanoparticles, enabling material-efficient thermal inactivation. These results establish a structure–property–function relationship in which catalytic oxygen reduction and galvanic Cu dissolution provide continuous dark activity, while plasmonic photothermal effects introduce a controllable light-driven amplification pathway. This multi-mechanistic framework supports the design of scalable antimicrobial coatings and interfaces capable of operating across both illuminated and non-illuminated environments.