Investigating the Antimicrobial Potential of Metallic Based Nanoparticles and their Integration within Biocompatible Polymers

Antimicrobial resistance of pathogenic infections is a rising global issue resulting in less effective antibiotic treatments against infections, thus leading to prolonged hospitalisation, higher mortality rates and increased healthcare costs. Therefore, the aim of this research is to extend the exploration of nanomaterials with antimicrobial activity and utilise them for the development of biomedical devices. In this endeavour, nanoparticles have been found to provide one possible alternative solution to tackle the challenges of antibiotic resistance. Metal nanoparticles, in particularly silver and copper, have shown promising antimicrobial potential for bioengineering and biomedical material applications. However, only a limited number of nanoparticles and their effects on common bacteria from hospital acquired infections (HAI) have been studied. This investigation extends knowledge of the antimicrobial activity of relevant nanoparticles. In this research, a variety of nanoparticles, including mono-metallic, bimetallic and graphene-based materials, were screened against common fungi, Gram-negative and Gram-positive bacteria that were listed by World Health Organisation (WHO) as a priority for the development of new antibiotics due to their multiple antibiotic resistances. Results demonstrated that these metallic based nanoparticles exhibited antimicrobial activity against a wide range of microbes, with elemental silver (Ag), bimetallic silver copper (AgCu) and elemental copper (Cu10) suspension nanoparticles displaying the broadest range of efficacies, with minimal inhibitory concentrations as low as 7.81 µg/ml. Upon the selection of antimicrobial nanoparticles, extended investigations on the antimicrobial activity were performed against E. coli, S. aureus and C. albicans. Based on the antimicrobial range and efficacy results, bimetallic AgCu nanoparticles were selected for further investigation. The properties of AgCu were explored and compared to Cu10 and Ag to help understand the link between the physio-chemical properties and the antimicrobial efficacy. It was found that hydrodynamic size and release of ions contributed the most to the antimicrobial effect of the nanoparticles. With this in mind, the mechanisms of action of the AgCu nanoparticles were investigated. Through observational techniques such as TEM and SEM, it was found that AgCu nanoparticles caused morphological changes to the microbes, including cell membrane damage, shrinkage in cell size by 10-35% and leakage of internal material. Furthermore, physical contact with C. albicans and S. aureus was observed. In bacterial cells, an increase of up 318% in oxidative stress and decrease in deoxyribonucleic acid (DNA) production to less than 13% was measured after incubation with AgCu nanoparticles. The selected nanoparticle, AgCu, was then fabricated into polymers with potential biomedical applications. Firstly, AgCu nanoparticles were incorporated into polydimethylsiloxane (PDMS) films. Films were produced with nanoparticles well dispersed throughout the film as observed via scanning electron microscopy (SEM); however no antimicrobial activity was exhibited. As a result, the films were surface treated with UV lamp, which resulted in an increase of AgCu nanoparticle exposure and ion release, leading to a 9.8% to 71.8% reduction in microbial growth (P = 0.05), depending on the microbial strain. A second application involved incorporating AgCu nanoparticle into polycaprolactone/polyethylene oxide (PCL/PEO) polymers. Through the disk diffusion method, it was found that the AgCu incorporated PCL/PEO films exhibited antimicrobial activity towards E. coli, S. aureus and C. albicans. The films had hydrophilic properties and partly dissolved upon contact with water. This resulted in the exposure and release of AgCu nanoparticles and ions thus leading to antimicrobial activity with zone of inhibition diameters between 1.04 cm to 4.20 cm, depending on microbial strain and AgCu nanoparticle concentration. Additionally, pores were found on the surface of the PCL/PEO polymers which has been suggested to provide benefits as wound dressing applications. However, the toxicity and biocompatibility of these AgCu nanoparticle incorporated PCL/PEO polymers requires investigation and validations with mammalian cells. These experiments have proven that certain nanoparticles provide antimicrobial activity against a wide spectrum of pathogenic species and can be incorporated in to polymers to fabricate antimicrobial films. However, further studies are required to fully elucidate the mechanism of action, the factors that can influence their antimicrobial effectiveness and toxicity as biomedical applications

pH Alteration in Plant-Mediated Green Synthesis and Its Resultant Impact on Antimicrobial Properties of Silver Nanoparticles (AgNPs)

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)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.Peer reviewe

Surface interactions and viability of coronaviruses

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.Peer reviewe

Applied Methods to Assess the Antimicrobial Activity of Metallic-Based Nanoparticles

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/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.Peer reviewe

Functionalized Copper Nanoparticles with Gold Nanoclusters: Part I. Highly Selective Electrosynthesis of Hydrogen Peroxide

© 2023 The Authors. Published by American Chemical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Copper nanoparticles (CuNPs) and gold nanoclusters (AuNCs) show a high catalytic performance in generating hydrogen peroxide (H2O2), a property that can be exploited to kill disease-causing microbes and to carry carbon-free energy. Some combinations of NPs/NCs can generate synergistic effects to produce stronger antiseptics, such as H2O2 or other reactive oxygen species (ROS). Herein, we demonstrate a novel facile AuNC surface decoration method on the surfaces of CuNPs using galvanic displacement. The Cu–Au bimetallic NPs presented a high selective production of H2O2 via a two-electron (2e–) oxygen reduction reaction (ORR). Their physicochemical analyses were conducted by scanning electron microscopy (SEM), transmitting electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). With the optimized Cu–Au1.5NPs showing their particle sizes averaged in 53.8 nm, their electrochemical analysis indicated that the pristine AuNC structure exhibited the highest 2e– selectivity in ORR, the CuNPs presented the weakest 2e– selectivity, and the optimized Cu–Au1.5NPs exhibited a high 2e– selectivity of 95% for H2O2 production, along with excellent catalytic activity and durability. The optimized Cu–Au1.5NPs demonstrated a novel pathway to balance the cost and catalytic performance through the appropriate combination of metal NPs/NCs.Peer reviewe

Proceedings of Abstracts, School of Physics, Engineering and Computer Science Research Conference 2022

© 2022 The Author(s). This is an open-access work distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. For further details please see https://creativecommons.org/licenses/by/4.0/. Plenary by Prof. Timothy Foat, ‘Indoor dispersion at Dstl and its recent application to COVID-19 transmission’ is © Crown copyright (2022), Dstl. This material is licensed under the terms of the Open Government Licence except where otherwise stated. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: [email protected] present proceedings record the abstracts submitted and accepted for presentation at SPECS 2022, the second edition of the School of Physics, Engineering and Computer Science Research Conference that took place online, the 12th April 2022

Exploitation of antimicrobial nanoparticles and their applications in biomedical engineering

Antibiotic resistance is a major threat to public health which contributes largely to increased mortality rates and costs in hospitals. The severe and wide spread of antibiotic resistance results in limited treatment 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 fully elucidate the mechanisms of action and to further advance for biomedical applications. 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 aims to reduce cross contaminations, disease transmissions and usage of antibiotics.Peer reviewe

Antifungal effect of Pegylated Graphene Oxide and Silver Nanoparticles against Candida albicans

Peer reviewe

Functionalized Copper Nanoparticles with Gold Nanoclusters: Part I. Highly Selective Electrosynthesis of Hydrogen Peroxide

Copper nanoparticles (CuNPs) and gold nanoclusters (AuNCs) show a high catalytic performance in generating hydrogen peroxide (H2O2), a property that can be exploited to kill disease-causing microbes and to carry carbon-free energy. Some combinations of NPs/NCs can generate synergistic effects to produce stronger antiseptics, such as H2O2 or other reactive oxygen species (ROS). Herein, we demonstrate a novel facile AuNC surface decoration method on the surfaces of CuNPs using galvanic displacement. The Cu–Au bimetallic NPs presented a high selective production of H2O2 via a two-electron (2e–) oxygen reduction reaction (ORR). Their physicochemical analyses were conducted by scanning electron microscopy (SEM), transmitting electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). With the optimized Cu–Au1.5NPs showing their particle sizes averaged in 53.8 nm, their electrochemical analysis indicated that the pristine AuNC structure exhibited the highest 2e– selectivity in ORR, the CuNPs presented the weakest 2e– selectivity, and the optimized Cu–Au1.5NPs exhibited a high 2e– selectivity of 95% for H2O2 production, along with excellent catalytic activity and durability. The optimized Cu–Au1.5NPs demonstrated a novel pathway to balance the cost and catalytic performance through the appropriate combination of metal NPs/NCs

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)