Antibacterial effect of silver nanoparticles in Pseudomonas aeruginosa

Therapeutic strategies for drug-resistant Pseudomonas aeruginosa: Metal and metal oxide nanoparticles

Pseudomonas aeruginosa (PA) is a widely prevalent opportunistic pathogen. Multiple resistant strains of PA have emerged from excessive or inappropriate use of antibiotics, making their eradication increasingly difficult. Therefore, the search for highly efficient and secure novel antimicrobial agents is crucial. According to reports, there is an increasing exploration of nanometals for antibacterial purposes. The antibacterial mechanisms involving the nanomaterials themselves, the release of ions, and the induced oxidative stress causing leakage and damage to biomolecules are widely accepted. Additionally, the study of the cytotoxicity of metal nanoparticles is crucial for their antibacterial applications. This article summarizes the types of metal nanomaterials and metal oxide nanomaterials that can be used against PA, their respective unique antibacterial mechanisms, cytotoxicity, and efforts made to improve antibacterial performance and reduce toxicity, including combination therapy with other materials and antibiotics, as well as green synthesis approaches.

Green Synthesis of Metallic Nanoparticles from Quercus Bark Extracts: Characterization and Functional Properties

Quercus species are utilized for their durable wood, providing sustenance for wildlife, conserving biodiversity, and contributing ecological, medicinal, and esthetic benefits to ecosystems and landscapes. In this study, we aimed to use the bark of three Quercus species (Q. dalechampi, Q. fraineto, and Q. petraea) for the synthesis of silver and gold nanoparticles (AgNPs and AuNPs). The aqueous extracts from the bark of Quercus sp. acted both as reducing and stabilizing agent, facilitating the rapid synthesis of AuNPs (AuQD, AuQF, and AuQP) and AgNPs (AgQD, AgQF, and AgQP). The obtained nanoparticles were characterized using UV-vis spectroscopy, TEM, DLS, and FTIR. Characterizations revealed that the nanoparticles exhibited a variety of shapes, such as polygonal, triangular, and spherical forms, with sizes ranging between 14 and 24 nm for AuNPs and 45-70 nm for AgNPs. The total phenolic content was assessed through spectroscopic methods, while several individual phenolic compounds were identified and quantified using UPLC-PDA. Furthermore, we assessed the antioxidant, antibacterial, and antifungal capacities of AuNPs, AgNPs, and raw extracts. The highest antioxidant activity was observed for raw extracts, followed by AgNPs and AuNPs, while the most potent antibacterial and antifungal activity was observed in AgQP. Moreover, cytotoxicity was examined in a human keratinocyte cell line (HaCaT). The results indicated no cytotoxic effects for AuNPs, while AgNPs and the raw extracts exhibited cytotoxic effects after 48 h of incubation. This research underscores the multifaceted utility of Quercus bark extracts in the green synthesis of metallic nanoparticles and their subsequent bioactivity assessment, suggesting promising perspectives for their application in various fields while urging cautious consideration of their cytotoxic implications.

Antibiofilm activity of mesoporous silica nanoparticles against the biofilm associated infections

In pharmaceutical industries, various chemical carriers are present which are used for drug delivery to the correct target sites. The most popular and upcoming drug delivery carriers are mesoporous silica nanoparticles (MSN). The main reason for its popularity is its ability to be specific and optimize the drug delivery process in a controlled manner. Nowadays, MSNs are widely used to eradicate various microbial infections, especially the ones related to biofilms. Biofilms are sessile groups of cells that live by forming a consortium and exhibit antibacterial resistance (AMR). They exhibit AMR by extracellular polymeric substances (EPS) and various quorum sensing (QS) signaling molecules. Usually, bacterial and fungal cells are capable of forming biofilms. These biofilms are pathogenic. In the majority of the cases, biofilms cause nosocomial diseases. This review will focus on the antibiofilm activities of MSN, its mechanism of target-specific drug delivery, and its ability to disrupt the bacterial biofilms inhibiting the infection. The review will also discuss various mechanisms for the delivery of pharmaceutical molecules by the MSNs to inhibit the bacterial biofilms, and lastly, we will talk about the different types of MSNs and their antibiofilm activities.

Green synthesis and characterization of polyphenol-coated magnesium-substituted manganese ferrite nanoparticles: Antibacterial and antioxidant properties

Magnesium-substituted manganese ferrite (Mn0.9Mg0.1Fe2O4) nanoparticles were obtained through a wet chemical method and coated with green-extracted polyphenol from Punica granatum peel. The obtained spinel nanocomposite was fully characterized. The X-ray diffraction pattern revealed a single phase with an average crystalline size of 3.33-8.74 nm, confirming the cubic-spinel structure. The FESEM micrograph showed a quasi-spherical shape with nearly uniform particles, indicating mild agglomeration. The mean size of the Mn0.9Mg0.1Fe2O4 was 13.66 nm with a standard deviation of 2.05. The BET isotherms indicated a surface area of 85.45 m2/g. The basic groups attached to the external surface of Mg-doped spinel ferrite were discovered. The resulted superparamagnetic modified doped-nanoferrite particles showed antibacterial activity as well as antioxidant efficiency through studying Catalase (CAT), Glutathione (GSH), and Glutathione Peroxidase (GSH-Px) parameters. The outcomes highlight the promising potential of polyphenol-functionalized Mn0.9Mg0.1Fe2O4 magnetite nanosized particles for the development of novel anti-biofilm agents.

Unleashing the promise of emerging nanomaterials as a sustainable platform to mitigate antimicrobial resistance

The emergence and spread of antibiotic-resistant (AR) bacterial strains and biofilm-associated diseases have heightened concerns about exploring alternative bactericidal methods. The WHO estimates that at least 700 000 deaths yearly are attributable to antimicrobial resistance, and that number could increase to 10 million annual deaths by 2050 if appropriate measures are not taken. Therefore, the increasing threat of AR bacteria and biofilm-related infections has created an urgent demand for scientific research to identify novel antimicrobial therapies. Nanomaterials (NMs) have emerged as a promising alternative due to their unique physicochemical properties, and ongoing research holds great promise for developing effective NMs-based treatments for bacterial and viral infections. This review aims to provide an in-depth analysis of NMs based mechanisms combat bacterial infections, particularly those caused by acquired antibiotic resistance. Furthermore, this review examines NMs design features and attributes that can be optimized to enhance their efficacy as antimicrobial agents. In addition, plant-based NMs have emerged as promising alternatives to traditional antibiotics for treating multidrug-resistant bacterial infections due to their reduced toxicity compared to other NMs. The potential of plant mediated NMs for preventing AR is also discussed. Overall, this review emphasizes the importance of understanding the properties and mechanisms of NMs for the development of effective strategies against antibiotic-resistant bacteria.

Antipathogenic Efficacy of Biogenic Silver Nanoparticles and Antibiofilm Activities Against Multi-drug-Resistant ESKAPE Pathogens

The silver nanoparticles (AgNPs) were produced by employing a biogenic loom and tested for antipathogenic assets against multi-drug-resistant (MDR) ESKAPE bacteria. Biogenically synthesized AgNPs were characterized adopting various high-throughput techniques such as UHRTEM, SEM with EDX, DLS, TGA-DTA, and XRD and spectroscopic analysis showed polydispersion of nanoparticles. In this context, AgNPs with the attribute of spherical-shaped nanoparticles with an average size of 26 nm were successfully synthesized utilizing bacterial supernatant. The antipathogenic activities of AgNPs were assessed against 11 strains of MDR ESKAPE bacteria including Enterococcus faecium; methicillin-resistant Staphylococcus aureus; Klebsiella pneumonia; Acinetobacter baumannii; Pseudomonas aeruginosa; Enterobacter aerogenes; and Enterobacter species. The exposure of biogenic AgNPs in a well diffusion assay showed all the growth inhibitions of ESKAPE bacteria at 200 μg/ml after 18 h of incubation. Growth kinetics demonstrated maximum killing at 60 μg/ml after 4 h of completion. The highest biofilm depletions were found at 100 μg/ml in adhesion assay. Live/dead assays showed effective killing of the ESKAPE bacteria at 10 μg/ml in pre-existing biofilms. The effective inhibitory concentrations of AgNPs were investigated ranging from 10 to 200 μg/ml. The selected pathogens found sensitive to AgNPs are statistically significant (P < 0.05) than that of cefotaxime/AgNO3. Consequently, a broad spectrum of antimicrobial potentials of AgNPs can be alternative to conventional antimicrobial agents for future medicine.

A comprehensive review on Moringa oleifera nanoparticles: importance of polyphenols in nanoparticle synthesis, nanoparticle efficacy and their applications

Moringa oleifera is one of the popular functional foods that has been tremendously exploited for synthesis of a vast majority of metal nanoparticles (NPs). The diverse secondary metabolites present in this plant turn it into a green tool for synthesis of different NPs with various biological activities. In this review, we discussed different types of NPs including silver, gold, titanium oxide, iron oxide, and zinc oxide NPs produced from the extract of different parts of M. oleifera. Different parts of M. oleifera take a role as the reducing, stabilizing, capping agent, and depending on the source of extract, the color of solution changes within NP synthesis. We highlighted the role of polyphenols in the synthesis of NPs among major constituents of M. oleifera extract. The different synthesis methods that could lead to the formation of various sizes and shapes of NPs and play crucial role in biomedical application were critically discussed. We further debated the mechanism of interaction of NPs with various sizes and shapes with the cells, and further their clearance from the body. The application of NPs made from M. oleifera extract as anticancer, antimicrobial, wound healing, and water treatment agent were also discussed. Small NPs show better antimicrobial activity, while they can be easily cleared from the body through the kidney. In contrast, large NPs are taken by the mono nuclear phagocyte system (MPS) cells. In case of shape, the NPs with spherical shape penetrate into the bacteria, and show stronger antibacterial activity compared to the NPs with other shapes. Finally, this review aims to correlate the key characteristics of NPs made from M. oleifera extract, such as size and shape, to their interactions with the cells for designing and engineering them for bio-applications and especially for therapeutic purposes.

Anti-Bacterial Activity of Green Synthesised Silver and Zinc Oxide Nanoparticles against Propionibacterium acnes

Propionibacterium acnes plays a critical role in the development of acne vulgaris. There has been a rise in the number of patients carrying P. acnes strains that are resistant to antibiotics. Thus, alternative anti-microbial agents are required. Zinc oxide (ZnO-NPs) and silver (Ag-NPs) nanoparticles can be used against several antibiotic-resistant bacteria. The impact of Ag-NPs and ZnO-NPs against two clinical strains of P. acnes, P1 and P2, and a reference strain, NCTC747, were investigated in this research. A chemical approach for the green synthesis of Ag-NPs and ZnO-NPs from Peganum harmala was employed. The microtiter plate method was used to examine the effects of NPs on bacterial growth, biofilm development, and biofilm eradication. A broth microdilution process was performed in order to determine minimal inhibitory (MIC) concentrations. Ag-NPs and ZnO-NPs had a spherical shape and average dimensions of 10 and 50 nm, respectively. MIC values for all P. acnes strains for Ag-NPs and ZnO-NPs were 125 µg/mL and 250 µg/mL, respectively. Ag-NP and ZnO-NP concentrations of 3.9- 62.5 µg/mL and 15-62.5 µg/mL significantly inhibited the growth and biofilm formation of all P. acnes strains, respectively. ZnO-NP concentrations of 15-62.5 μg/mL significantly inhibited the growth of NCTC747 and P2 strains. The growth of P1 was impacted by concentrations of 31.25 μg/mL and 62.5 μg/mL. Biofilm formation in the NCTC747 strain was diminished by a ZnO-NP concentration of 15 μg/mL. The clinical strains of P. acnes were only affected by ZnO-NP titres of more than 31.25 μg/mL. Established P. acne biofilm biomass was significantly reduced in all strains at a Ag-NP and ZnO-NP concentration of 62.5 µg/mL. The findings demonstrated that Ag-NPs and ZnO-NPs exert an anti-bacterial effect against P. acnes. Further research is required to determine their potential utility as a treatment option for acne.

Molecular Analysis of Carbapenem and Aminoglycoside Resistance Genes in Carbapenem-Resistant Pseudomonas aeruginosa Clinical Strains: A Challenge for Tertiary Care Hospitals

Carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) strains have become a global threat due to their remarkable capability to survive and disseminate successfully by the acquisition of resistance genes. As a result, the treatment strategies have been severely compromised. Due to the insufficient available data regarding P. aeruginosa resistance from Pakistan, we aimed to investigate the resistance mechanisms of 249 P. aeruginosa strains by antimicrobial susceptibility testing, polymerase chain reaction for the detection of carbapenemases, aminoglycoside resistance genes, extended-spectrum beta-lactamases (ESBLs), sequence typing and plasmid typing. Furthermore, we tested silver nanoparticles (AgNPs) to evaluate their in vitro sensitivity against antimicrobial-resistant P. aeruginosa strains. We observed higher resistance against antimicrobials in the general surgery ward, general medicine ward and wound samples. Phenotypic carbapenemase-producer strains comprised 80.7% (201/249) with 89.0% (179/201) demonstrating genes encoding carbapenemases: blaNDM-1 (32.96%), blaOXA48 (37.43%), blaIMP (7.26%), blaVIM (5.03%), blaKPC-2 (1.12%), blaNDM-1/blaOXA48 (13.97%), blaOXA-48/blaVIM (1.68%) and blaVIM/blaIMP (0.56%). Aminoglycoside-modifying enzyme genes and 16S rRNA methylase variants were detected in 43.8% (109/249) strains: aac(6')-lb (12.8%), aac(3)-lla (12.0%), rmtB (21.1%), rmtC (11.0%), armA (12.8%), rmtD (4.6%), rmtF (6.4%), rmtB/aac(3)-lla (8.2%), rmtB/aac(6')-lla (7.3%) and rmtB/armA (3.6%). In total, 43.0% (77/179) of the strains coharbored carbapenemases and aminoglycoside resistance genes with 83.1% resistant to at least 1 agent in 3 or more classes and 16.9% resistant to every class of antimicrobials tested. Thirteen sequence types (STs) were identified: ST235, ST277, ST234, ST170, ST381, ST175, ST1455, ST1963, ST313, ST207, ST664, ST357 and ST348. Plasmid replicon types IncFI, IncFII, IncA/C, IncL/M, IncN, IncX, IncR and IncFIIK and MOB types F11, F12, H121, P131 and P3 were detected. Meropenem/AgNPs and Amikacin/AgNPs showed enhanced antibacterial activity. We reported the coexistence of carbapenemases and aminoglycoside resistance genes among carbapenem-resistant P. aeruginosa with diverse clonal lineages from Pakistan. Furthermore, we highlighted AgNP's potential role in handling future antimicrobial resistance concerns.

Antimicrobial peptide-conjugated phage-mimicking nanoparticles exhibit potent bactericidal action against Streptococcus pyogenes in murine wound infection models

Streptococcus pyogenes is a causative agent for strep throat, impetigo, and more invasive diseases. The main reason for the treatment failure of streptococcal infections is increased antibiotic resistance. In recent years, infectious diseases caused by pyogenic streptococci resistant to multiple antibiotics have been rising with a significant impact on public health and the veterinary industry. The development of antibiotic resistance and the resulting emergence of multidrug-resistant bacteria have become primary threats to the public health system, commonly leading to nosocomial infections. Many researchers have turned their focus to developing alternative classes of antibacterial agent based on various nanomaterials. We have developed an antibiotic-free nanoparticle system inspired by naturally occurring bacteriophages to fight antibiotic-resistant bacteria. Our phage-mimicking nanoparticles (PhaNPs) display structural mimicry of protein-turret distribution on the head structure of bacteriophages. By mimicking phages, we can take advantage of their evolutionary constant shape and high antibacterial activity while avoiding the immune reactions of the human body experienced by biologically derived phages. We describe the synthesis of hierarchically arranged core-shell nanoparticles, with a silica core conjugated with silver-coated gold nanospheres to which we have chemisorbed the synthetic antimicrobial peptide Syn-71 on the PhaNPs surface, and increased the rapidity of the antibacterial activity of the nanoparticles (PhaNP@Syn71). The antibacterial effect of the PhaNP@Syn71 was tested in vitro and in vivo in mouse wound infection models. In vitro, results showed a dose-dependent complete inhibition of bacterial growth (>99.99%). Cytocompatibility testing on HaCaT human skin keratinocytes showed minimal cytotoxicity of PhaNP@Syn71, being comparable to the vehicle cytotoxicity levels even at higher concentrations, thus proving that our design is biocompatible with human cells. There was a minimum cutoff dosage above which there was no evolution of resistance after prolonged exposure to sub-MIC dosages of PhaNP@Syn71. Application of PhaNP@Syn71 to a mouse wound infection model exhibited high biocompatibility in vivo while showing immediate stabilization of the wound size, and infection free wound healing. Our results suggest the robust utility of antimicrobial peptide-conjugated phage-mimicking nanoparticles as a highly effective antibacterial system that can combat bacterial infections consistently while avoiding the emergence of resistant bacterial strains.

Plant-Origin Components: New Players to Combat Antibiotic Resistance in Klebsiella pneumoniae

Klebsiella pneumoniae (Kpn) is an opportunistic pathogen that causes intrahospital complications such as pneumonia, liver abscesses, soft tissue infections, urinary infections, bacteraemia, and, in some cases, death. Since this bacterium has a higher frequency than other Gram-negative pathogens, it has become an important pathogen to the health sector. The adaptative genome of Kpn likely facilitates increased survival of the pathogen in diverse situations. Therefore, several studies have been focused on developing new molecules, synergistic formulations, and biomaterials that make it possible to combat and control infections with and dispersion of this pathogen. Note that the uncontrolled antibiotic administration that occurred during the pandemic led to the emergence of new multidrug-resistant strains, and scientists were challenged to overcome them. This review aims to compile the latest information on Kpn that generates intrahospital infections, specifically their pathogenicity-associated factors. Furthermore, it explains the natural-product-based treatments (extracts and essential oils) developed for Kpn infection and dispersion control.

In Vitro Effects of Silver Nanoparticles on Pathogenic Bacteria and on Metabolic Activity and Viability of Human Mesenchymal Stem Cells

The rapid development of nanotechnology has led to the use of silver nanoparticles (Ag-NPs) in various biomedical fields. However, the effect of Ag-NPs on human mesenchymal stem cells (hMSCs) is not fully understood. Moreover, too frequent an exposure to products containing nanosilver in sublethal amounts raises widespread concerns that it will lead to the development of silver-resistant microorganisms. Therefore, this study aimed to evaluate the mechanism of action of Ag-NPs on hMSCs by analyzing the cellular uptake of Ag-NPs by the cells and its effect on their viability and to assess antimicrobial activity of Ag-NPs against emerging bacterial strains, including multidrug-resistant pathogens. For metabolic activity and viability evaluation, hMSCs were incubated with different concentrations of Ag-NPs (14 μg/mL, 7 μg/mL, and 3.5 μg/mL) for 10 min., 1 h and 24 h and subsequently analyzed for their viability by live-dead staining and metabolic activity by the MTS assay. The effect of Ag-NPs on bacterial pathogens was studied by determining their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). In conclusion, it was observed that exposure of hMSCs to Ag-NPs of size <10 nm has no cytotoxic effect on the metabolic activity of the cells at the concentration of 3.5 μg/mL, with minimal cytotoxic effect being observed at the concentration of 14 μg/mL after 24 h of incubation. Our findings also confirmed that Ag-NPs at the concentration of 4 μg/mL are effective broad-spectrum bactericidal agents, regardless of the antibiotic-resistance mechanism present in bacteria.

Ultraviolet blocking ability, antioxidant and antibacterial properties of newly prepared polyvinyl alcohol-nanocellulose‑silver nanoparticles-ChunJian peel extract composite film

In this work, nanocellulose (CNC) from waste water chestnut (WCT) shell was firstly used for preparing nanocomposite films, by using ChunJian peel extract (CJPE) as a green reducing agent to synthesize silver nanoparticles (AgNPs), and then loading them into polyvinyl alcohol-nanocellulose (PVA-CNC) matrix, a multifunctional nanocomposite material that could be used in food packaging was developed. The prepared films were tested for mechanical strength, barrier properties, thermal properties, antibacterial, antioxidant and biocompatibility through various characterizations. The PVA-CNC-AgNPs-CJPE film had good thermostability, mechanical strength, barrier properties, and biocompatibility. Compared with pure PVA film and PVA-CNC film, PVA-CNC-AgNPs-CJPE could shield over 95 % of the UVB (320-275 nm) spectrum and UVC (275-200 nm) spectrum and most of the UVA (400-320 nm). By disk diffusion analysis, the inhibition zones of PVA-CNC-AgNPs-CJPE film against E. coli, P. aeruginosa, S. aureus and E. faecalis were 22.3 mm, 25.0 mm, 22.0 mm and 19.3 mm, respectively. The milk antibacterial simulation test confirmed that PVA-CNC-AgNPs-CJPE film could effectively limit bacterial reproduction and prolong the shelf life of milk. PVA-CNC-AgNPs-CJPE film had excellent UV barrier properties, good antioxidant properties and high-efficiency antibacterial activity, which is expected to be widely used in sustainable nanocomposite food packaging.

Biomedical Approach of Nanotechnology and Biological Risks: A Mini-Review

Nanotechnology has played a prominent role in biomedical engineering, offering innovative approaches to numerous treatments. Notable advances have been observed in the development of medical devices, contributing to the advancement of modern medicine. This article briefly discusses key applications of nanotechnology in tissue engineering, controlled drug release systems, biosensors and monitoring, and imaging and diagnosis. The particular emphasis on this theme will result in a better understanding, selection, and technical approach to nanomaterials for biomedical purposes, including biological risks, security, and biocompatibility criteria.

Resistance in Pseudomonas aeruginosa: A Narrative Review of Antibiogram Interpretation and Emerging Treatments

Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium renowned for its resilience and adaptability across diverse environments, including clinical settings, where it emerges as a formidable pathogen. Notorious for causing nosocomial infections, P. aeruginosa presents a significant challenge due to its intrinsic and acquired resistance mechanisms. This comprehensive review aims to delve into the intricate resistance mechanisms employed by P. aeruginosa and to discern how these mechanisms can be inferred by analyzing sensitivity patterns displayed in antibiograms, emphasizing the complexities encountered in clinical management. Traditional monotherapies are increasingly overshadowed by the emergence of multidrug-resistant strains, necessitating a paradigm shift towards innovative combination therapies and the exploration of novel antibiotics. The review accentuates the critical role of accurate antibiogram interpretation in guiding judicious antibiotic use, optimizing therapeutic outcomes, and mitigating the propagation of antibiotic resistance. Misinterpretations, it cautions, can inadvertently foster resistance, jeopardizing patient health and amplifying global antibiotic resistance challenges. This paper advocates for enhanced clinician proficiency in interpreting antibiograms, facilitating informed and strategic antibiotic deployment, thereby improving patient prognosis and contributing to global antibiotic stewardship efforts.

Mechanism and antibacterial synergies of poly(Dabco-BBAC) nanoparticles against multi-drug resistant Pseudomonas aeruginosa isolates from human burns

Multi-drug resistant bacteria are a major problem in the treatment of infectious diseases, such as pneumonia, meningitis, or even coronavirus disease 2019 (COVID-19). Cationic nanopolymers are a new type of antimicrobial agent with high efficiency. We synthesized and characterized cationic polymer based on 1,4-diazabicyclo [2.2.2] octane (DABCO) and Bis (bromoacetyl)cystamine (BBAC), named poly (DABCO-BBAC) nanoparticles(NPs), and produced 150 nm diameter NPs. The antibacterial activity of poly (DABCO-BBAC) against eight multi drug resistant (MDR) Pseudomonas aeruginosa isolates from human burns, its possible synergistic effect with gentamicin, and the mechanism of action were examined. Poly(DABCO-BBAC) could effectively inhibit and kill bacterial strains at a very low concentration calculated by minimum inhibitory concentration (MIC) assay. Nevertheless, its synergism index with gentamicin showed an indifferent effect. Moreover, transmission electron microscopy and lipid peroxidation assays showed that poly (DABCO-BBAC) distorted and damaged the bacterial cell wall. These results suggest that the poly (DABCO-BBAC) could be an effective antibacterial agent for MDR clinical pathogens.

Alginate coated biogenic silver nanoparticles for the treatment of Pseudomonas infections in rainbow trout

Pseudomonas species are among the main pathogens causing rainbow trout infections. The present study provides a simple, green, sustainable, and rapid technique to synthesize of biogenic alginate-capped silver nanoparticles (Alg-Ag NPs) suitable for the treatment of Pseudomonas infections. It has been shown that the mechanism (aggregative or autocatalytic) of Alg-Ag NPs formation depended on Alg concentration and the heating approach used. The rate constants and activation energy were calculated. Alg-Ag NPs were characterized by UV-Vis, FTIR, XRD, TEM, AFM, XPS, and DLS. The optimal conditions for the fabrication of spherically-shaped (17-19 nm) and negatively-charged (zeta-potential <-50 mV) Alg-Ag NPs, which are stable during 9 months, included hot-plate assisted synthesis at 100 °C in diluted (1 mg/mL) Alg solutions. In vitro studies showed that Alg-Ag NPs exhibited prominent antimicrobial activity against collection Pseudomonas strains (inhibition zones ranged from 9.0 ± 1.0 to 19.0 ± 1.0 mm), with no significant loss of antibacterial efficacy after 9 months of storage. AFM analysis confirmed that the antibacterial effect of Alg-Ag NPs dealt with the direct nanomechanical disrupting of bacterial cells. The ability of Alg-Ag NPs to inhibit the growth of virulent P.aeruginosa, P.fluorescens and P. putida strains isolated from infected rainbow trout was evaluated. All tested strains were susceptible to Alg(10)-Ag NPs, while Alg(1)-Ag NPs demonstrated a limited strain-specific antibacterial effect. The obtained data displayed the prospects for the application of biogenic Alg-Ag NPs to create novel delivery systems for combating Pseudomonas infections in rainbow trout.

Structural characterization, antioxidant and anti-uropathogenic potential of biogenic silver nanoparticles using brown seaweed Turbinaria ornata

Alternative treatment strategies for urinary tract infections (UTIs) are becoming more necessary due to increasing drug resistance patterns in uropathogens. Nanoparticle-based therapeutics is emerging as a way to treat UTIs. In the present study, using Turbinaria ornata extract, silver nanoparticles (AgNPs) were synthesized, characterized, and their anti-uropathogenic activity was evaluated. The stability and formation of synthesized To-AgNPs were confirmed by UV-visible spectroscopy, FTIR, XRD, SEM, and DLS. An FTIR spectrum confirmed the presence of seaweed functional groups in To-AgNPs, a XRD analysis confirmed their crystalline nature, and SEM imaging confirmed their spherical nature with an average size of 73.98 nm with diameters ranging from 64.67 to 81.28 nm. This was confirmed by TEM results. DLS determined that the cumulant hydrodynamic diameter of To-AgNPs was 128.3 nm with a PdI of 0.313 and the zeta potential value were found to be -63.3 mV which indicates the To-AgNPs are negatively charged and more stable. DPPH assays were used to assess the antioxidant activity of biosynthesized To-AgNPs, while an agar well diffusion method was used to test the antibacterial activity against uropathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Klebsiella pneumoniae. The To-AgNPs showed the highest susceptibility to S. aureus (15.75 ± 0.35 mm) and E. coli (15 ± 0.7 mm) with MIC values of 0.0625 and 0.125 mg/ml, respectively in macro broth dilution method and observed considerable membrane damage under CLSM and SEM. To-AgNPs displayed stronger antioxidant and antimicrobial activity, suggesting they may be developed as a new class of antimicrobial agents for treating UTIs.

The efficacy of biosynthesized silver nanoparticles against Pseudomonas aeruginosa isolates from cystic fibrosis patients

The high antibiotic resistance of Pseudomonas aeruginosa (PA) makes it critical to develop alternative antimicrobial agents that are effective and affordable. One of the many applications of silver nanoparticles (Ag NPs) is their use as an antimicrobial agent against bacteria resistant to common antibiotics. The key purpose of this research was to assess the antibacterial and antibiofilm effectiveness of biosynthesized Ag NPs against six biofilm-forming clinically isolated strains of PA and one reference strain (ATCC 27853). Ag NPs were biosynthesized using a seed extract of Peganum harmala as a reducing agent. Ag NPs were characterized by Ultraviolet-visible (UV-Vis) spectroscopy and scanning transmission electron microscopy (STEM). The effect of Ag NPs on biofilm formation and eradication was examined through micro-titer plate assays, and the minimal inhibitory (MIC) and minimum bactericidal (MBC) concentrations determined. In addition, real-time polymerase chain reactions (RT-PCR) were performed to examine the effects of Ag NPs on the expression of seven PA biofilm-encoding genes (LasR, LasI, LssB, rhIR, rhII, pqsA and pqsR). The biosynthesized Ag NPs were spherically-shaped with a mean diameter of 11 nm. The MIC for each PA strain was 15.6 µg/ml, while the MBC was 31.25 µg/ml. All PA strains exposed to Ag NPs at sub-inhibitory concentrations (0.22-7.5 µg/ml) showed significant inhibitory effects on growth and biofilm formation. Biomass and biofilm metabolism were reduced dependent on Ag NP concentration. The expression of the quorum-sensing genes of all strains were significantly reduced at an Ag NP concentration of 7.5 µg/ml. The results demonstrate the extensive in-vitro antibacterial and antibiofilm performance of Ag NPs and their potential in the treatment of PA infection. It is recommended that future studies examine the possible synergy between Ag NPs and antibiotics.

Biofabrication of silver nanoparticles employing biomolecules of Paraclostridium benzoelyticum strain: Its characterization and their in-vitro antibacterial, anti-aging, anti-cancer and other biomedical applications

The current study aims to utilize the bacteria Paraclostridium benzoelyticum strain 5610 to synthesize bio-genic silver nanoparticles (AgNPs). Biogenic AgNPs were thoroughly examined using various characterization techniques such as UV-spectroscopy, XRD, FTIR, SEM, and EDX. Synthesis of AgNPs was confirmed by UV-vis analysis resulting in absorption peak at 448.31 nm wavelength. The SEM analysis indicated the morphological characteristics and size of AgNPs which was 25.29 nm. The face centered cubic (FCC) crystallographic structure was confirmed by XRD. Furthermore, FTIR study affirmed the capping of AgNPs by different compounds found in biomass of the Paraclostridium benzoelyticum strain 5610. Later, EDX was used to determine the elemental composition with respective concentration and distribution. Additionally, in the current study the antibacterial, anti-inflammatory, antioxidant, anti-aging, and anti-cancer ability of AgNPs was assessed. The antibacterial activity of AgNPs was tested against four distinct sinusitis pathogens: Haemophilus in-fluenza, Streptococcus pyogenes, Moraxella catarrhalis and Streptococcus pneumonia. AgNPs shows significant inhibition zone against Streptococcus pyogenes 16.64 ± 0.35 followed by 14.32 ± 071 for Moraxella catarrhalis. Similarly, the antioxidant potential was found maximum (68.37 ± 0.55%) at 400 μg/mL and decrease (5.48 ± 0.65%) at 25 μg/mL, hence the significant antioxidant ability was observed. Furthermore, anti-inflammatory activity of AgNPs shows the strongest inhibitory action (42.68 ± 0.62%) for 15-LOX with lowest inhibition activity for COX-2 (13.16 ± 0.46%). AgNPs have been shown to exhibit significant inhibitory actions against the enzyme elastases AGEs (66.25 ± 0.49%), which are followed by AGEs of visperlysine (63.27 ± 0.69%). Furthermore, the AgNPs show high toxicity against HepG2 cell line which shows 53.543% reduction in the cell viability after 24 h of treatment. The anti-inflammatory activity demonstrated a potent inhibitory effect of the bio-inspired AgNPs. Overall, the biogenic AgNPs have the ability to be served for the treatments of anti-aging and also due to their anti-cancer, antioxidant abilities NPs may be a useful therapy choice for a variety of disorders including cancer, bacterial infections and other inflammatory diseases. Moreover, further studies are required in the future to evaluate their in vivo biomedical applications. HIGHLIGHTS: Biogenic synthesis of AgNPs using Paraclostridium benzoelyticum Strain for the first time. FTIR analysis confirmed capping of potent biomolecules which are of great use in applied field especially Nanomedicines. Notable antimicrobial activity against sinusitis bacteria and cytotoxic potential of synthesized AgNPs on in vitro basis produce a new idea shifting us to treat cancerous cell lines.

Cellulose Hydrogel with Hyaluronic Acid and Silver Nanoparticles: Sustained-Release Formulation with Antibacterial Properties against Pseudomonas aeruginosa

Pathogenic bacteria resistant to conventional antibiotics represent a global challenge and justify the need for new antimicrobials capable of combating bacterial multidrug resistance. This study describes the development of a topical hydrogel in a formulation composed of cellulose, hyaluronic acid (HA), and silver nanoparticles (AgNPs) against strains of Pseudomonas aeruginosa. AgNPs as an antimicrobial agent were synthesized by a new method based on green chemistry, using arginine as a reducing agent and potassium hydroxide as a carrier. Scanning electron microscopy showed the formation of a composite between cellulose and HA in a three-dimensional network of cellulose fibrils, with thickening of the fibrils and filling of spaces by HA with the presence of pores. Ultraviolet-visible spectroscopy (UV-vis) and particle size distribution for dynamic light scattering (DLS) confirmed the formation of AgNPs with peak absorption at ~430 nm and 57.88 nm. AgNPs dispersion showed a minimum inhibitory concentration (MIC) of 1.5 µg/mL. The time-kill assay showed that after 3 h of exposure to the hydrogel containing AgNPs, there were no viable cells, corresponding to a bactericidal efficacy of 99.999% in the 95% confidence level. We obtained a hydrogel that is easy to apply, with sustained release and bactericidal properties against strains of Pseudomonas aeruginosa at low concentrations of the agent.

Silver nanoparticles affect wheat (Triticum aestivum L.) germination, seedling blight and yield

The aim of the study was to evaluate the effect of two types of negatively charged quasi-spherical silver nanoparticles (AgNPs) at concentrations of 10, 20 and 30mgL-1 and silver ions at a concentration of 30mgL-1 on the growth, selected physiological aspects and yielding of wheat (Triticum aestivum L.) cv. Tybalt, and on plant resistance to seedling blight. Seed germination, α-amylase activity in seeds, morphology and infestation of seedlings by pathogens were assessed in a hydroponic treatment. Growth rate, PSII efficiency, heading and yield of the same plants were then analysed in pot culture. Results showed that the AgNPs and silver ions had a negative effect on roots, but reduced seedling blight and improved leaf area compared to the control. In addition, the AgNPs reduced with sodium borohydride in the presence of trisodium citrate at concentrations of 10 and 20mgL-1 stimulated germination, α-amylase activity and shoot length, which was not observed in the case of silver ions and the AgNPs reduced with sodium hypophosphite in the presence of sodium hexametaphosphate. In a pot experiment, the AgNPs improved plant growth, PSII efficiency, accelerated heading and increased yield-related parameters compared with the control. Results revealed the interaction strength in the following order: TCSB-AgNPs>SHSH-AgNPs>silver ions. TCSB-AgNPs in the lowest concentration had the most favourable effect, indicating their great potential for use in improving wheat cultivation.

Green Synthesis of Silver Nanoparticles from Allium cepa L. Peel Extract, Their Antioxidant, Antipathogenic, and Anticholinesterase Activity

The present work deals with the green synthesis and characterization of silver nanoparticles (AgNPs) using Allium cepa (yellowish peel) and the evaluation of its antimicrobial, antioxidant, and anticholinesterase activities. For the synthesis of AgNPs, peel aqueous extract (200 mL) was treated with a 40 mM AgNO3 solution (200 mL) at room temperature, and a color change was observed. In UV-Visible spectroscopy, an absorption peak formation at ~439 nm was the sign that AgNPs were present in the reaction solution. UV-vis, FE-SEM, TEM, EDX, AFM, XRD, TG/DT analyses, and Zetasizer techniques were used to characterize the biosynthesized nanoparticles. The crystal average size and zeta potential of AC-AgNPs with predominantly spherical shapes were measured as 19.47 ± 1.12 nm and -13.1 mV, respectively. Pathogenic microorganisms Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were used for the Minimum Inhibition Concentration (MIC) test. When compared to tested standard antibiotics, AC-AgNPs demonstrated good growth inhibitory activities on P. aeuruginosa, B. subtilis, and S. aureus strains. In vitro, the antioxidant properties of AC-AgNPs were measured using different spectrophotometric techniques. In the β-Carotene linoleic acid lipid peroxidation assay, AC-AgNPs showed the strongest antioxidant activity with an IC₅₀ value of 116.9 µg/mL, followed by metal-chelating capacity and ABTS cation radical scavenging activity with IC₅₀ values of 120.4 µg/mL and 128.5 µg/mL, respectively. The inhibitory effects of produced AgNPs on the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes were determined using spectrophotometric techniques. This study provides an eco-friendly, inexpensive, and easy method for the synthesis of AgNPs that can be used for biomedical activities and also has other possible industrial applications.

Development of Decellularized Fish Skin Scaffold Decorated with Biosynthesized Silver Nanoparticles for Accelerated Burn Wound Healing

In this study, decellularized fish skin (DFS) scaffold decorated with silver nanoparticles was prepared for accelerating burn wound healing. The silver nanoparticles (AgNPs) synthesized by the green and facile method using Aloe vera leaf at different incubating times were characterized by using X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, and Ultraviolet-Visible Spectroscopy (UV-Vis spectroscopy). The different characterizations confirmed that the sizes of AgNPs prepared by incubating for 6 hours and 12 hours were 29.1 nm and 35.2 nm, respectively. After that, the different concentrations of the smallest AgNPs were used to dope the DFS scaffold to determine the cell viability. Additionally, an agar well diffusion method was used to screen for antimicrobial activity. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were used to correlate the concentration of AgNPs with its bactericidal effect which was seen from 50 μg/ml. Then, the toxicity with human cells was investigated using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay with no significant cell viability from the concentration of 50 μg/ml to 200 μg/ml compared to the cocultured and commercial treatments.

Antifungal Activity of Selenium Nanoparticles Obtained by Plant-Mediated Synthesis

The continuous need to satisfy world food demand has led to the search for new alternatives to combat economic losses in agriculture caused by phytopathogenic fungi. These organisms cause plant diseases, reducing their productivity and decreasing fruit quality. Among the new tools being explored is nanotechnology. Nanoparticles with antimicrobial properties could be an excellent alternative to address this problem. In this work, selenium nanoparticles (SeNPs) were obtained using plant extracts of Amphipterygium glaucum leaves (SeNPs-AGL) and Calendula officinalis flowers (SeNPs-COF). Characterization of the SeNPs was performed and their ability as antifungal agents against two commercially relevant plant pathogenic fungi, Fusarium oxysporum and Colletotrichum gloeosporioides, was evaluated. Assays were performed with different concentrations of SeNPs (0, 0.25, 0.5, 1.0, and 1.7 mg/mL). It was observed that both SeNPs had antifungal activity against both plant pathogens at concentrations of 0.25 mg/mL and above. SeNPs-AGL demonstrated better antifungal activity and smaller size (around 8.0 nm) than SeNPs-COF (134.0 nm). FTIR analysis evidenced the existence of different functional groups that constitute both types of SeNPs. There are factors that have to be considered in the antimicrobial activity of SeNPs such as nanoparticle size and phytochemical composition of the plant extracts used, as these may affect their bioavailability.

Biofabrication of Silver Nanoparticles Using Teucrium Apollinis Extract: Characterization, Stability, and Their Antibacterial Activities

Medical science has paid a great deal of attention to green synthesis silver nanoparticles (AgNPs) because of their remarkable results with multidrug-resistant bacteria. This study was conducted on the preparation of AgNPs, using the teucrium apollinis extract as a reducing agent and a capping ligand. The AgNP produced was stable in room condition up to 10 weeks. The AgNP was characterized using UV-visible absorption spectroscopy (UV-Vis), attenuated Fourier transform infrared (ATR-FTIR), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The study confirms the ability of teucrium apollinis to produce AgNPs with high stability. The influence of pH was studied over a pH range of (2–12) on the stability of synthesized AgNPs. The best value of pH was 7.2, where AgNP showed a good stability with high antibacterial activity against Pseudomonas aeruginosa. AgNP synthesis is confirmed by a strong peak in the UV-Vis due to surface plasmon resonance (SPR) at 379 nm. Based on TEM findings, monodispersed AgNP has a spherical shape with a small size of 16 ± 1.8 nm. In this study, teucrium apollinis extract was used for the first time, which could be a good environmental method for synthesizing AgNP, which offers a possible alternative to chemical AgNPs.

Influence of silver ion release on the inactivation of antibiotic resistant bacteria using light-activated silver nanoparticles

The widespread increase in antibiotic resistance (AR), in an extensive range of microorganisms, demands the development of alternative antimicrobials with novel non-specific low-mutation bacterial targets. Silver nanoparticles (AgNPs) and photosensitizers (PSs) are promising antimicrobial agents with broad-spectrum activity and low tendency for antimicrobial resistance development. Herein, we investigated the light-mediated oxidation of AgNPs for accelerated release of Ag⁺ in the antibacterial synergy of PS-AgNP conjugates using protoporphyrin IX (PpIX) as a PS. Also, the influence of polyethyleneimine (PEI) coated AgNPs in promoting antibacterial activity was examined. We synthesized, characterized and tested the antimicrobial effect of three nanoparticles: AgNPs, PpIX-AgNPs, and PEI-PpIX-AgNPs against a methicillin-resistant Staphylococcus aureus strain (MRSA) and a wild-type multidrug resistant (MDR) E. coli. PpIX-AgNPs were the most effective material achieving >7 log inactivation of MRSA and MDR E. coli. The order of bacterial log inactivation was PpIX-AgNPs > PEI-PpIX-AgNPs > AgNPs. This order correlates with the trend of Ag⁺ concentration released by the NPs (PpIX-AgNPs > PEI-PpIX-AgNPs > AgNPs). Our study confirms a synergistic effect between PpIX and AgNPs in the inactivation of AR pathogens with about 10-fold increase in inactivation of ARB relative to AgNPs only. The concentration of Ag⁺ released from NPs determined the log inactivation of MRSA and MDR E. coli more than either the phototoxic effect or the electrostatic interaction promoted by surface charge of nanoparticles with bacteria cells. All NPs showed negligible cytotoxicity to mammalian cells at the bacterial inhibitory concentration after 24 h exposure. These observations confirm the crucial role of optimized Ag⁺ release for enhanced performance of AgNP-based antimicrobials against AR pathogens.

Effects of mycogenic silver nanoparticles on organisms of different trophic levels

Biogenic silver nanoparticles (AgNPs) are considered a promising alternative to their synthetic versions. However, the environmental impact of such nanomaterials is still scarcely understood. Thus, the present study aims at assessing the antimicrobial action and ecotoxicity of AgNPs biosynthesized by the fungus Aspergillus niger IBCLP20 towards three freshwater organisms: Chlorella vulgaris, Daphnia similis, and Danio rerio (zebrafish). AgNPs IBCLP20 showed antibacterial action against Klebsiella pneumoniae between 5 and 100 μg mL^-1, and antifungal action against Trichophyton mentagrophytes in concentrations ranging from 20 to 100 μg mL^-1. The cell density of the microalgae Chlorella vulgaris decreased 40% after 96 h of exposure to AgNPs IBCLP20, at the highest concentration analysed (100 μg L^-1). The 48 h median lethal concentration for Daphnia similis was estimated as 4.06 μg L^-1 (2.29-6.42 μg L^-1). AgNPs IBCLP20 and silver nitrate (AgNO₃) caused no acute toxicity on adult zebrafish, although they did induce several physiological changes. Mycosynthetized AgNPs caused a significant increase (p < 0.05) in oxygen consumption at the highest concentration studied (75 μg L^-1) and an increase in the excretion of ammonia at the lower concentrations, followed by a reduction at the higher concentrations. Such findings are comparable with AgNO₃, which increased the oxygen consumption on low exposure concentrations, followed by a decrease at the high tested concentrations, while impairing the excretion of ammonia in all tested concentrations. The present results show that AgNPs IBCLP20 have biocidal properties. Mycogenic AgNPs induce adverse effects on organisms of different trophic levels and understanding their impact is detrimental to developing countermeasures aimed at preventing any negative environmental effects of such novel materials.

An alternative approach for controlling bacterial pathogens in liquid and solid poultry waste using Calcium hypochlorite Ca(OCl)2 disinfectant-based silver nanoparticles

Inappropriate handling of poultry waste from the beginning to the end of the production cycle could lead to health and environmental hazards. The purpose of this study was to assess the current state of poultry waste management practices as well as to evaluate the efficacy of disinfectants (VIRKON S, Quaternary ammonium compound (QAC), Calcium hypochlorite [Ca(OCl)₂], and nanomaterials (nano-silver particles (Ag NPs), and Ca(OCl)₂-Ag NPs composite) on pathogenic bacteria for use in the disinfection of waste collection areas within poultry operation systems. Two hundred and ten samples were gathered from variant waste types for isolation and identification of pathogenic bacteria. Then, the efficacy of some disinfectants against fifty strains of isolated bacteria was evaluated using a broth micro-dilution assay. Results showed the most predominant bacterial isolates from wastes were E. coli (33.69%), Salmonella spp. (26.09%), followed by K. pneumonae (15.22%) and L. monocytogenes (14.13%). Ca(OCl)₂-Ag NPs had a microbial lethal effect against all pathogenic bacteria (100%) that were isolated from liquid and solid waste. In conclusion, poultry manure waste is collected and dumped on the agricultural land around those chicken farms without any treatment. The Ca(OCl)₂-Ag NPs composite was lethal to all pathogenic microbes isolated from waste and their collected areas at 1.0 mg/L concentration.

Pseudomonas aeruginosa Clusters Toxic Nickel Nanoparticles to Enhance Survival

Microorganisms forming a biofilm might become multidrug-resistant by information exchange. Multi-resistant, biofilm-producing microorganisms are responsible for a major portion of hospital-acquired infections. Additionally, these microorganisms cause considerable damage in the industrial sector. Here, we screened several nanoparticles of transition metals for their antibacterial properties. The nanoparticles sizes of nickel (<300 nm) and nickel oxide (<50 nm) were analyzed with transmission electron microscopy. We could show that the antibacterial efficacy of nickel and nickel oxide nanoparticles on Pseudomonas aeruginosa isolated from household appliances and Staphylococcus aureus was the highest. Interestingly, only P. aeruginosa was able to survive at high concentrations (up to 50 mM) due to clustering toxic nanoparticles out of the medium by biofilm formation. This clustering served to make the medium nearly free of nanoparticles, allowing the bacteria to continue living without contact to the stressor. We observed these clusters by CLSM, SEM, and light microscopy. Moreover, we calculated the volume of NiO particles in the bacterial biofilms based on an estimated thickness of 5 nm from the TEM images as an average volume of 3.5 × 10−6 µm3. These results give us a new perspective on bacterial defense mechanisms and might be useful in industries such as water purification.

Green Extracellular Synthesis of Silver Nanoparticles by Pseudomonas alloputida, Their Growth and Biofilm-Formation Inhibitory Activities and Synergic Behavior with Three Classical Antibiotics

Bacterial resistance to antibiotics is on the rise and hinders the fight against bacterial infections, which are expected to cause millions of deaths by 2050. New antibiotics are difficult to find, so alternatives are needed. One could be metal-based drugs, such as silver nanoparticles (AgNPs). In general, chemical methods for AgNPs' production are potentially toxic, and the physical ones expensive, while green approaches are not. In this paper, we present the green synthesis of AgNPs using two Pseudomonas alloputida B003 UAM culture broths, sampled from their exponential and stationary growth phases. AgNPs were physicochemically characterized by transmission electron microscopy (TEM), total reflection X-ray fluorescence (TXRF), infrared spectroscopy (FTIR), dynamic light scattering (DLS), and X-ray diffraction (XRD), showing differential characteristics depending on the synthesis method used. Antibacterial activity was tested in three assays, and we compared the growth and biofilm-formation inhibition of six test bacteria: Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. We also monitored nanoparticles' synergic behavior through the growth inhibition of E. coli and S. aureus by three classical antibiotics: ampicillin, nalidixic acid, and streptomycin. The results indicate that very good AgNP activity was obtained with particularly low MICs for the three tested strains of P. aeruginosa. A good synergistic effect on streptomycin activity was observed for all the nanoparticles. For ampicillin, a synergic effect was detected only against S. aureus. ROS production was found to be related to the AgNPs' antibacterial activity.

Surface properties-dependent antifungal activity of silver nanoparticles

Silver nanoparticles (AgNPs) exhibit unusual biocidal properties thanks to which they find a wide range of applications in diverse fields of science and industry. Numerous research studies have been devoted to the bactericidal properties of AgNPs while less attention has been focused on their fungicidal activity. Our studies were therefore oriented toward determining the impact of AgNPs characterized by different physicochemical properties on Fusarium avenaceum and Fusarium equiseti. The main hypothesis assumed that the fungicidal properties of AgNPs characterized by comparable morphology can be shaped by stabilizing agent molecules adsorbed on nanoparticle surfaces. Two types of AgNPs were prepared by the reduction of silver ions with sodium borohydride (SB) in the presence of trisodium citrate (TC) or cysteamine hydrochloride (CH). Both types of AgNPs exhibited a quasi-spherical shape. Citrate-stabilized AgNPs (TCSB-AgNPs) of an average size of 15 ± 4 nm were negatively charged. Smaller (12 ± 4 nm), cysteamine-capped AgNPs (CHSB-AgNPs) were characterized by a positive surface charge and higher silver ion release profile. The phytopathogens were exposed to the AgNPs in three doses equal to 2.5, 5 and 10 mg L^-1 over 24 and 240 h. Additionally, the impact of silver ions delivered in the form of silver nitrate and the stabilizing agents of AgNPs on the fungi was also investigated. The response of phytopathogens to these treatments was evaluated by determining mycelial growth, sporulation and changes in the cell morphology. The results of our studies showed that CHSB-AgNPs, especially at a concentration of 10 mg L^-1, strongly limited the vegetative mycelium growth of both species for short and long treatment times. The cell imaging revealed that CHSB-AgNPs damaged the conidia membranes and penetrated into the cells, while TCSB-AgNPs were deposited on their surface. The fungistatic (lethal) effect was demonstrated only for silver ions at the highest concentration for the F. equiseti species in the 240 h treatment. The number of spores of both Fusarium species was significantly reduced independently of the type of silver compounds used. Generally, it was found that the positively charged CHSB-AgNPs were more fungicidal than negatively charged TCSB-AgNPs. Thereby, it was established that the stabilizing agents of AgNPs and surface charge play a crucial role in the shaping of their fungicidal properties.

A concise review on implications of silver nanoparticles in bone tissue engineering

Skeletal disorders represent a variety of degenerative diseases that affect bone and cartilage homeostasis. The regenerative capacity of bone is affected in osteoporosis, osteoarthritis, rheumatoid arthritis, bone fractures, congenital defects, and bone cancers. There is no viable, non-invasive treatment option and bone regeneration requires surgical intervention with the implantation of bone grafts. Incorporating nanoparticles in bone grafts have improved fracture healing by providing fine structures for bone tissue engineering. It is currently a revolutionary finding in the field of regenerative medicine. Silver nanoparticles (AgNPs) have garnered particular attention due to their well-known anti-microbial and potential osteoinductive properties. In addition, AgNPs have been demonstrated to regulate the proliferation and differentiation of mesenchymal stem cells (MSCs) involved in bone regeneration. Furthermore, AgNPs have shown toxicity towards cancer cells derived from bone. In the last decade, there have been multiple studies focusing on the effect of nanoparticles on the proliferation and/or differentiation of MSCs and bone cancer cells; however, the specific studies with AgNPs are limited. Although the reported investigations show promising in vitro and in vivo potential of AgNPs for application in bone regeneration, more studies are required to ensure their implications in bone tissue engineering. This review aims to highlight the current advances related to the production of AgNPs and their effect on MSCs and bone cancer cells, which will potentiate their possible implications in orthopedics. Moreover, this review article evaluates the future of AgNPs in bone tissue engineering.

Antibacterial, Antioxidant, and Phytotoxic Potential of Phytosynthesized Silver Nanoparticles Using Elaeagnus umbellata Fruit Extract

Due to its eco-friendliness, cost-effectiveness, ability to be handled safely, and a wide variety of biological activities, the green plant-mediated synthesis of nanoparticles has become increasingly popular. The present work deals with the green synthesis and characterization of silver nanoparticles (AgNPs) using Elaeagnus umbellata (fruit) and the evaluation of its antibacterial, antioxidant, and phytotoxic activities. For the synthesis of AgNPs, fruit extract was treated with a 4 mM AgNO₃ solution at room temperature, and a color change was observed. In UV-Visible spectroscopy, an absorption peak formation at 456 nm was the sign that AgNPs were present in the reaction solution. Scanning electron microscopy and physicochemical X-ray diffraction were used to characterize AgNPs, which revealed that they were crystalline, spherical, and had an average size of 11.94 ± 7.325 nm. The synthesized AgNPs showed excellent antibacterial activity against Klebsiella pneumoniae (14 mm), Staphylococcus aureus (13.5 mm), Proteus mirabilis (13 mm), and Pseudomonas aeruginosa (12.5 mm), as well as considerable antioxidant activity against DPPH with 69% inhibition at an IC₅₀ value of 43.38 µg/mL. AgNPs also exhibited a concentration-dependent effect on rice plants. Root and shoot length were found to be positively impacted at all concentrations, i.e., 12.5 µg/mL, 25 µg/mL, 50 µg/mL, and 100 µg/mL. Among these concentrations, the 50 µg/mL concentration of AgNPs was found to be most effective. The plant biomass decreased at higher AgNP exposure levels (i.e., 100 µg/mL), whereas 50 µg/mL caused a significant increase in plant biomass as compared to the control. This study provides an eco-friendly method for the synthesis of AgNPs which can be used for their antibacterial and antioxidant activities and also as growth promoters of crop plants.

PMMA-Based Nanocomposites for Odontology Applications: A State-of-the-Art

Polymethyl methacrylate (PMMA), a well-known polymer of the methacrylate family, is extensively used in biomedicine, particularly in odontological applications including artificial teeth, dentures and denture bases, obturators, provisional or permanent crowns, and so forth. The exceptional PMMA properties, including aesthetics, inexpensiveness, simple manipulation, low density, and adjustable mechanical properties, make it a perfect candidate in the field of dentistry. However, it presents some deficiencies, including weakness regarding hydrolytic degradation, poor fracture toughness, and a lack of antibacterial activity. To further enhance its properties and solve these drawbacks, different approaches can be performed, including the incorporation of nanofillers. In this regard, different types of metallic nanoparticles, metal oxide nanofillers, and carbon-based nanomaterials have been recently integrated into PMMA matrices with the aim to reduce water absorption and improve their performance, namely their thermal and flexural properties. In this review, recent studies regarding the development of PMMA-based nanocomposites for odontology applications are summarized and future perspectives are highlighted.

Silver Nanoparticle-Based Therapy: Can It Be Useful to Combat Multi-Drug Resistant Bacteria?

The present review focuses on the potential use of silver nanoparticles in the therapy of diseases caused by antibiotic-resistant bacteria. Such bacteria are known as “superbugs”, and the most concerning species are Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus (methicillin and vancomycin-resistant), and some Enterobacteriaceae. According to the World Health Organization (WHO), there is an urgent need for new treatments against these “superbugs”. One of the possible approaches in the treatment of these species is the use of antibacterial nanoparticles. After a short overview of nanoparticle usage, mechanisms of action, and methods of synthesis of nanoparticles, emphasis has been placed on the use of silver nanoparticles (AgNPs) to combat the most relevant emerging resistant bacteria. The toxicological aspects of the AgNPs, both in vitro using cell cultures and in vivo have been reviewed. It was found that toxic activity of AgNPs is dependent on dose, size, shape, and electrical charge. The mechanism of action of AgNPs involves interactions at various levels such as plasma membrane, DNA replication, inactivation of protein/enzymes necessary, and formation of reactive oxygen species (ROS) leading to cell death. Researchers do not always agree in their conclusions on the topic and more work is needed in this field before AgNPs can be effectively applied in clinical therapy to combat multi-drug resistant bacteria.

Green Synthesis of Silver Nanoparticles Using Populi gemmae Extract: Preparation, Physicochemical Characterization, Antimicrobial Potential and In Vitro Antiproliferative Assessment

Green route is an economic, facile and eco-friendly method, employed for the synthesis of various types of nanoparticles, having it as a starting point biological entity, especially as a plant extract. The present study aims to obtain silver nanoparticles (AgNPs) starting from an ethanolic extract of Populi gemmae (Pg), by adjusting the reaction parameters. The morphological and structural characterization exhibited that both the reaction temperature and the concentration of metal salt, contributes to the obtaining of Pg-AgNPs with adjustable size and shape. The newly synthesized nanoparticles exhibited a good antibacterial activity on Gram-positive bacteria as well as antifungal activity. The in vitro antiproliferative activity of Pg-AgNPs was assessed on two different cancer cell lines (breast cancer cells-MCF7 and lung carcinoma epithelial cells-A549). Results have shown that the green-synthetized Pg-AgNPs_S2 (obtained at 60 °C, using AgNO3 of 5 M) induced a substantial decrease in tumor cell viability in a dose-dependent manner with an IC50 ranging from 5.03 to 5.07 µg/mL on A549 cell line and 3.24 to 4.93 µg/mL on MCF7 cell line.

Occurrence of antibiotics and bacterial resistance genes in wastewater: resistance mechanisms and antimicrobial resistance control approaches

Antimicrobial pharmaceuticals are classified as emergent micropollutants of concern, implying that even at low concentrations, long-term exposure to the environment can have significant eco-toxicological effects. There is a lack of a standardized regulatory framework governing the permissible antibiotic content for monitoring environmental water quality standards. Therefore, indiscriminate discharge of antimicrobials at potentially active concentrations into urban wastewater treatment facilities is rampant. Antimicrobials may exert selective pressure on bacteria, leading to resistance development and eventual health consequences. The emergence of clinically important multiple antibiotic-resistant bacteria in untreated hospital effluents and wastewater treatment plants (WWTPs) has been linked to the continuous exposure of bacteria to antimicrobials. The levels of environmental exposure to antibiotics and their correlation to the evolution and spread of resistant bacteria need to be elucidated to help in the formulation of mitigation measures. This review explores frequently detected antimicrobials in wastewater and gives a comprehensive coverage of bacterial resistance mechanisms to different antibiotic classes through the expression of a wide variety of antibiotic resistance genes either inherent and/or exchanged among bacteria or acquired from the reservoir of antibiotic resistance genes (ARGs) in wastewater systems. To complement the removal of antibiotics and ARGs from WWTPs, upscaling the implementation of prospective interventions such as vaccines, phage therapy, and natural compounds as alternatives to widespread antibiotic use provides a multifaceted approach to minimize the spread of antimicrobial resistance.

Biologically synthesized silver nanoparticles as potent antibacterial effective against multidrug-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most worrisome infectious bacteria due to its intrinsic and acquired resistance against several antibiotics and the recalcitrance of its infections; hence, the development of novel antimicrobials effective against multidrug‐resistant P. aeruginosa is mandatory. In this work, silver nanoparticles obtained by green synthesis using a leaf extract and fungi were tested against a battery of clinical strains from cystic fibrosis, pneumonia and burnt patients, some of them with multidrug resistance. Both nanoparticles showed a potent antibacterial effect, causing severe damage to the cell wall, membrane and DNA, and inducing the production of reactive oxygen species. Moreover, the nanoparticles derived from fungi showed synergistic antibacterial effects with the antibiotics meropenem and levofloxacin for some clinical strains and both kinds of nanoparticles were nontoxic for larvae of the moth Galleria mellonella, encouraging further research for their implementation in the treatment of P. aeruginosa infections.

Biological Synthesis of Low Cytotoxicity Silver Nanoparticles (AgNPs) by the Fungus Chaetomium thermophilum—Sustainable Nanotechnology

Fungal biotechnology research has rapidly increased as a result of the growing awareness of sustainable development and the pressing need to explore eco-friendly options. In the nanotechnology field, silver nanoparticles (AgNPs) are currently being studied for application in cancer therapy, tumour detection, drug delivery, and elsewhere. Therefore, synthesising nanoparticles (NPs) with low toxicity has become essential in the biomedical area. The fungus Chaetomium thermophilum (C. thermophilum) was here investigated—to the best of our knowledge, for the first time—for application in the production of AgNPs. Transmission electronic microscopy (TEM) images demonstrated a spherical AgNP shape, with an average size of 8.93 nm. Energy-dispersive X-ray spectrometry (EDX) confirmed the presence of elemental silver. A neutral red uptake (NRU) test evaluated the cytotoxicity of the AgNPs at different inhibitory concentrations (ICs). A half-maximal concentration (IC50 = 119.69 µg/mL) was used to predict a half-maximal lethal dose (LD50 = 624.31 mg/kg), indicating a Global Harmonized System of Classification and Labelling of Chemicals (GHS) acute toxicity estimate (ATE) classification category of 4. The fungus extract showed a non-toxic profile at the IC tested. Additionally, the interaction between the AgNPs and the Balb/c 3T3 NIH cells at an ultrastructural level resulted in preserved cells structures at non-toxic concentrations (IC20 = 91.77 µg/mL), demonstrating their potential as sustainable substitutes for physical and chemically made AgNPs. Nonetheless, at the IC50, the cytoplasm of the cells was damaged and mitochondrial morphological alteration was evident. This fact highlights the fact that dose-dependent phenomena are involved, as well as emphasising the importance of investigating NPs’ effects on mitochondria, as disruption to this organelle can impact health.

First Report on the Phenotypic and Genotypic Susceptibility Profiles to Silver Nitrate in Bacterial Strains Isolated from Infected Leg Ulcers in Romanian Patients

Silver-ion-based antiseptics are widely used in treating chronic leg ulcers and, given the emergence of resistance to such compounds, the investigation of silver susceptibility and resistance profiles of pathogenic strains isolated from this type of wound is a topic of great interest. Therefore, in this study, 125 bacterial strains isolated from 103 patients with venous ulcers were investigated to elucidate their susceptibility to silver-nitrate solutions in planktonic and biofilm growth states, and the associated genetic determinants. The isolated strains, both in the planktonic and biofilm growth phases, showed high sensitivity to the standard concentration of 1/6000 silver-nitrate solution. It was noticed that even at concentrations lower than the clinical one (the first 2–3 binary dilutions in the case of planktonic cultures and the first 6–7 binary dilutions in the case of biofilms), the antiseptic solution proved to maintain its antibacterial activity. The phenotypic results were correlated with the genetic analysis, highlighting the presence of silver-resistance genes (sil operon) in only a few of the tested Staphylococcus sp. (especially in S. aureus) strains, Escherichia coli and Pseudomonas aeruginosa strains. These results demonstrate that despite its large use, this antiseptic remains a viable treatment alternative for the management of chronic leg wounds.

Theragnostic application of nanoparticle and CRISPR against food-borne multi-drug resistant pathogens

Foodborne infection is one of the leading sources of infections spreading across the world. Foodborne pathogens are recognized as multidrug-resistant (MDR) pathogens posing a significant problem in the food industry and healthy consumers resulting in enhanced economic burden, and nosocomial infections. The continued search for enhanced microbial detection tools has piqued the interest of the CRISPR-Cas system and Nanoparticles. CRISPR-Cas system is present in the bacterial genome of some prokaryotes and is repurposed as a theragnostic tool against MDR pathogens. Nanoparticles and composites have also emerged as an efficient tool in theragnostic applications against MDR pathogens. The diagnostic limitations of the CRISPR-Cas system are believed to be overcome by a synergistic combination of the nanoparticles system and CRISPR-Cas using nanoparticles as vehicles. In this review, we have discussed the diagnostic application of CRISPR-Cas technologies along with their potential usage in applications like phage resistance, phage vaccination, strain typing, genome editing, and antimicrobial. we have also elucidated the antimicrobial and detection role of nanoparticles against foodborne MDR pathogens. Moreover, the novel combinatorial approach of CRISPR-Cas and nanoparticles for their synergistic effects in pathogen clearance and drug delivery vehicles has also been discussed.

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Bacterial CRISPR Cas system are repurposed as a thergodiganostic tool against MDR pathogen.

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Combinatorial approach of CRISPR-Cas and Nanoparticle is used as delivery vehicle and clearing pathogens.

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CRISPR-Cas and Nanoparticles is a tool for the food safety profiling of MDR food-borne pathogen.

Biological Synthesis of Monodisperse Uniform-Size Silver Nanoparticles (AgNPs) by Fungal Cell-Free Extracts at Elevated Temperature and pH

Fungi’s ability to convert organic materials into bioactive products offers environmentally friendly solutions for diverse industries. In the nanotechnology field, fungi metabolites have been explored for green nanoparticle synthesis. Silver nanoparticle (AgNP) research has grown rapidly over recent years mainly due to the enhanced optical, antimicrobial and anticancer properties of AgNPs, which make them extremely useful in the biomedicine and biotechnology field. However, the biological synthesis mechanism is still not fully established. Therefore, this study aimed to evaluate the combined effect of time, temperature and pH variation in AgNP synthesis using three different fungi phyla (Ascomycota, Basidiomycota and Zygomycota) represented by six different fungi species: Cladophialophora bantiana (C. bantiana), Penicillium antarcticum (P. antarcticum), Trametes versicolor (T. versicolor), Trichoderma martiale (T. martiale), Umbelopsis isabellina (U. isabellina) and Bjerkandera adusta (B. adusta). Ultraviolet–visible (UV-Vis) spectrophotometry and transmission electron microscopy (TEM) results demonstrated the synthesis of AgNPs of different sizes (3 to 17 nm) and dispersity percentages (25 to 95%, within the same size range) using fungi extracts by changing physicochemical reaction parameters. It was observed that higher temperatures (90 °C) associated with basic pH (9 and 12) favoured the synthesis of monodisperse small AgNPs. Previous studies demonstrated enhanced antibacterial and anticancer properties correlated with smaller nanoparticle sizes. Therefore, the biologically synthesised AgNPs shown in this study have potential as sustainable substitutes for chemically made antibacterial and anticancer products. It was also shown that not all fungi species (B. adusta) secrete metabolites capable of reducing silver nitrate (AgNO3) precursors into AgNPs, demonstrating the importance of fungal screening studies.

Carbon-Based Nanomaterials: Carbon Nanotubes, Graphene and Fullerenes in Control of Burns Infections and Wound Healing

Burn injuries are extremely debilitating, resulting in high morbidity and mortality rates around the world. The risk of infection escalates in correlation with impairment of skin integrity, creating a barrier to healing and possibly leading to sepsis. With its numerous advantages over traditional treatment methods, nanomaterial-based wound healing has immense capability for treating and preventing wound infections. Carbon-based nanomaterials (CNMs) owing to their distinctive physicochemical and biological properties have emerged as promising platform for biomedical applications. Carbon nanotubes, graphene, fullerenes, and their nanocomposites have demonstrated broad antimicrobial activity against invasive bacteria, fungi, and viruses causing burn wound infection. The specific mechanisms that govern the antimicrobial activity of CNMs must be understood in order to ensure the safe and effective incorporation of these structures into biomaterials. However, it is challenging to decouple individual and synergistic contributions of physical, chemical, and electrical effects of CNMs on cells. This review reported on significant advances in the application of CNMs in burn wound infection and wound healing, with brief discussion on the interaction between different families of CNMs and microorganisms to assess antimicrobial performance.