Microwave Accelerated Green Synthesis of Stable Silver Nanoparticles with Eucalyptus globulus Leaf Extract and Their Antibacterial and Antibiofilm Activity on Clinical Isolates

Bactericidal and Cytotoxic Properties of Silver Nanoparticles

Silver nanoparticles (AgNPs) can be synthesized from a variety of techniques including physical, chemical and biological routes. They have been widely used as nanomaterials for manufacturing cosmetic and healthcare products, antimicrobial textiles, wound dressings, antitumor drug carriers, etc. due to their excellent antimicrobial properties. Accordingly, AgNPs have gained access into our daily life, and the inevitable human exposure to these nanoparticles has raised concerns about their potential hazards to the environment, health, and safety in recent years. From in vitro cell cultivation tests, AgNPs have been reported to be toxic to several human cell lines including human bronchial epithelial cells, human umbilical vein endothelial cells, red blood cells, human peripheral blood mononuclear cells, immortal human keratinocytes, liver cells, etc. AgNPs induce a dose-, size- and time-dependent cytotoxicity, particularly for those with sizes ≤10 nm. Furthermore, AgNPs can cross the brain blood barrier of mice through the circulation system on the basis of in vivo animal tests. AgNPs tend to accumulate in mice organs such as liver, spleen, kidney and brain following intravenous, intraperitoneal, and intratracheal routes of administration. In this respect, AgNPs are considered a double-edged sword that can eliminate microorganisms but induce cytotoxicity in mammalian cells. This article provides a state-of-the-art review on the synthesis of AgNPs, and their applications in antimicrobial textile fabrics, food packaging films, and wound dressings. Particular attention is paid to the bactericidal activity and cytotoxic effect in mammalian cells.

Green synthesis of silver nanoparticles: biomolecule-nanoparticle organizations targeting antimicrobial activity

Since discovery of the first antibiotic drug, penicillin, in 1928, a variety of antibiotic and antimicrobial agents have been developed and used for both human therapy and industrial applications. However, excess and uncontrolled use of antibiotic agents has caused a significant growth in the number of drug resistant pathogens. Novel therapeutic approaches replacing the inefficient antibiotics are in high demand to overcome increasing microbial multidrug resistance. In the recent years, ongoing research has focused on development of nano-scale objects as efficient antimicrobial therapies. Among the various nanoparticles, silver nanoparticles have gained much attention due to their unique antimicrobial properties. However, concerns about the synthesis of these materials such as use of precursor chemicals and toxic solvents, and generation of toxic byproducts have led to a new alternative approach, green synthesis. This eco-friendly technique incorporates use of biological agents, plants or microbial agents as reducing and capping agents. Silver nanoparticles synthesized by green chemistry offer a novel and potential alternative to chemically synthesized nanoparticles. In this review, we discuss the recent advances in green synthesis of silver nanoparticles, their application as antimicrobial agents and mechanism of antimicrobial mode of action.

Biofilm inhibition and anti-quorum sensing activity of phytosynthesized silver nanoparticles against the nosocomial pathogen Pseudomonas aeruginosa

Quorum sensing (QS), the communication signaling network, regulates biofilm formation and several virulence factors in Pseudomonas aeruginosa PAO1, a nosocomial opportunistic pathogen. QS is considered to be a challenging target for compounds antagonistic to virulent factors. Biologically synthesized silver nanoparticles (AgNPs) are reported as anti-QS and anti-biofilm drugs against bacterial infections. The present study reports on the synthesis and characterization of Piper betle (Pb) mediated AgNPs (Pb-AgNPs). The anti-QS activity of Pb-AgNPs against Chromobacterium violaceum and the potential effect of Pb-AgNPs on QS-regulated phenotypes in PAO1 were studied. FTIR analysis exhibited that Pb-AgNPs had been capped by phytochemical constituents of Pb. Eugenol is one of the active phenolic phytochemicals in Pb leaves, therefore molecular docking of eugenol-conjugated AgNPs on QS regulator proteins (LasR, LasI and MvfR) was performed. Eugenol-conjugated AgNPs showed considerable binding interactions with QS-associated proteins. These results provide novel insights into the development of phytochemically conjugated nanoparticles as promising anti-infective candidates.

Silver nanoparticles synthesized with Eucalyptus critriodora ethanol leaf extract stimulate antibacterial activity against clinically multidrug-resistant Acinetobacter baumannii isolated from pneumonia patients

The increasing multidrug resistance of Acinetobacter baumannii has been highlighted as a worldwide therapeutic problem. Despite the wide range of studies on green synthesis of silver nanoparticles, there is currently no alternative treatment for MDR A. baumannii infection. This study investigated the potential of silver nanoparticles synthesized with Eucalyptus critriodora leaf extract as an inhibitor of MDR A. baumannii infection. The results demonstrated that silver nanoparticles synthesized with E. critriodora leaf extract triggered MDR A. baumannii DNA condensation, induced bacterial cell death and had a significant effect on biofilm formation, biofilm-grown cells, bacterial attachment and invasion of human lung cells in a concentration dependent manner. Silver nanoparticles synthesized with E. critriodora leaf extract had no obvious effects on the viability of human lung cells. The synthesized silver nanoparticles inhibited MDR A. baumannii infection by approximately 90% without cytotoxicity with a 50% effective concentration of 0.028 μg/ml. Thus silver nanoparticles with E. critriodora leaf extract had the potential to be a promising anti-MDR A. baumannii agent for effective treatment and they point the way to further development of a wide range of effective biomedical applications.

Green synthesis of silver nanoparticles using Nardostachys jatamansi and evaluation of its anti-biofilm effect against classical colonizers

In this communication, we present the green synthesis of silver nanoparticles (AgNPs) using medicinally important Nardostachys jatamansi rhizome extract in the presence of sunlight. UV-vis spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Transmission electron microscope (TEM) and Energy dispersive X-ray analysis (EDX) were employed to characterize the synthesized AgNPs. UV-visible spectroscopic studies confirmed the presence of biosynthesized AgNPs. Transmission Electron Microscopic studies revealed the structure of spherical AgNPs in the diameter range of 10-15 nm. Energy dispersive X-ray analysis and elemental mapping clearly confirmed the presence of silver in AgNPs samples. Interestingly, biomolecules functionalised AgNPs exhibited a remarkable antioxidant, anti-inflammatory, and anti-biofilm activities and hence biosynthesized AgNPs from N. jatamansi can be used as a promising biomaterial for biomedical applications.

Evaluating microwave-synthesized silver nanoparticles from silver nitrate with life cycle assessment techniques

Silver Nanoparticles (AgNPs) are well known for applications in electronics and as antimicrobial agents because of their unique optical, electrical, cytotoxic and thermal properties. These nanoparticles can be synthesized via a wide variety of techniques; however, they require the use of hazardous solvents which have very high environmental impacts. Nanoscience researchers have attempted novel synthesis routes that reduce resource requirements and use benign chemicals, while maintaining control over their unique properties. The present study evaluates the potential environmental impacts of one such benign method using Life Cycle Assessment (LCA) techniques which are used to assess the environmental impacts of a product's life through all the stages from raw material extraction to disposal/ recycling. This research evaluates AgNPs which were synthesized using glucose as the reducing agent and food grade corn starch as the stabilizing agent in a microwave-assisted reaction system. GaBi 6.0 software was used to carry out the Life Cycle Impact Assessment on a declared unit of 1 kg of 3.0 ± 1.2 nm diameter AgNPs. The results indicate that the impacts are predominantly on acidification (AP), human health particulate air (HHAP) and human toxicity non-cancer (HTNCP) potentials. These impacts are mainly from the production of silver metal and electricity used. The starch and glucose used to produce AgNPs of 3.0 ± 1.2 nm is shown to have negligible environmental impacts and is therefore considered to be environmentally benign.

Toxicity assessment of metal oxide nano-pollutants on tomato (Solanum lycopersicon): A study on growth dynamics and plant cell death

The present study for the first time demonstrated the interactions of metal oxide (MO) nano-pollutants (CuO and Al₂O₃-NPs) with tissues and cellular DNA of tomato plants grown in soil sand: silt: clay (667:190:143) and Hoagland-hydroponic system and assessed the hazardous effects of NPs on cell physiology and biochemistry. Results of SEM equipped with EDX revealed attachment of variably shaped CuO-NPs (18 nm) and Al₂O₃-NPs (21 nm) on roots, and internalization followed by translocation in plants by ICP-MS and TEM. Significant variations in foliage surface area, chlorophyll, proteins, LPO, and antioxidant enzymes were recorded. Roots and shoots accumulated 225.8 ± 8.9 and 70.5 ± 4 μgAl g^-1 DW, whereas Cu accumulation was 341.6 ± 14.3 (roots) and 146.9 ± 8.1 μg g^-1 DW (shoots) which was significant (p ≤ 0.0005) as compared to control. The total soluble protein content in roots, shoots, and leaves collected from Al₂O₃-NPs treated plants increased by 120, 80, and 132%, respectively while in CuO-NPs treatments, the increase was 68 (roots), 36 (shoots), and 86% (leaves) over control. The level of antioxidant enzymes in plant tissues was significantly (p ≤ 0.05) higher at 2000 μg ml^-1 of MONPs over control. A dose-dependent increase in reactive oxygen species (ROS), biphasic change of lower and higher fluorescence in mitochondria due to dissipation of mitochondrial membrane potential (ΔΨm) and membrane defects using propidium iodide were observed. Comparatively, CuO-NPs induced higher toxicity than Al₂O₃-NPs. Perceptible changes in proteins (amide-I & II), cellulose, glucose, galactose and other carbohydrates were observed under FT-IR. The binding studies with TmDNA showed fluorescence quenching of EtBr-TmDNA and acridine orange-TmDNA complex only by CuO-NPs with -ΔG and +ΔH and +ΔS values. However, Al₂O₃-NPs induced lesser change in TmDNA conformation. Conclusively, the results are novel in better demonstrating the mechanistic basis of nano-phyto-toxicity and are important which could be used to develop strategies for safe disposal of Al₂O₃-NPs and CuO-NPs.

Phytofunctionalized silver nanoparticles: green biomaterial for biomedical and environmental applications

Variegated physicochemical routes with emerging modifications have been adopted and reported for silver nanoparticle synthesis for centuries. Nano-biotechnology aimed at the synthesis of nanomaterials, including silver nanoparticles, through utilization of biological media has acquired an auspicious role in science for human welfare. Despite recurrent nanoscale researches on physicochemical routes, coeval stages are predominated by greener methods in silver nanoparticle synthesis for the utilization of its inherent toxicity and exceedingly smaller sizes for biological and environmental applications. One of the principles of green routes for silver nanoparticle synthesis is reduction and stabilization via phytochemicals extracted from plants in a one-pot protocol of phytofunctionalization. Plants are preferred for their abundant availability, environmental non-toxicity and economical favorability and chiefly for the ease of aptness, unlike microbial pathways having tedious requirements of cellular culture maintenance conditions. The present work reviewed the most recent milestones set in the selection of types and parts of plants and optimized synthetic conditions employed in the fabrication of silver nanoparticles, in addition to quantitative and qualitative characterization. Furthermore, the use of phytofunctionalized silver nanoparticles for microbial growth inhibition and environmental remediation was also studied. Through the meticulous review of literature, potential applications were highlighted, which can provide researchers with a plethora of avenues for future investigations for remediation of the environment, in terms of both combating pathogenic microbes and environmental detoxification.

Antimicrobial and anticancer activities of silver nanoparticles synthesized from the root hair extract of Phoenix dactylifera

There is a continuous rise in the rate of medicine consumption because of the development of drug resistance by microbial pathogens. In the last one decade, silver nanoparticles (AgNPs) have become a remarkable choice for the development of new drugs due to their excellent broad-spectrum antimicrobial activity. In the current piece of work, we have synthesized AgNPs from the root extract of Phoenix dactylifera to test their antimicrobial and anti-cancer potential. UV-visible spectra showed the surface plasmon resonance peak at 420 nm λ_max corresponding to the formation of silver nanoparticles, FTIR spectra further confirmed the involvement of biological moieties in AgNPs synthesis. Moreover, XRD analysis showed the crystalline nature of AgNPs and predicted the crystallite size of 15 to 40 nm. Electron microscopy analyses confirmed their spherical shape. In addition, synthesized AgNPs was also found to control the growth of C. albicans and E. coli on solid nutrient medium with 20 and 22 mm zone of inhibition, respectively. The 100% potency at 40 μg/ml AgNPs concentration was observed against E. coli and C. albicans after 4 h and 48 h incubation respectively. Importantly, AgNPs were also found to decrease the cell viability of MCF7 cell lines in vitro with IC₅₀ values of 29.6 μg/ml and could act as a controlling agent of human breast cancer. Based on our results, we conclude that biologically synthesized AgNPs exhibited multifunctional properties and could be used against human cancer and other infectious diseases.

A review on biosynthesis of silver nanoparticles and their biocidal properties

Use of silver and silver salts is as old as human civilization but the fabrication of silver nanoparticles (Ag NPs) has only recently been recognized. They have been specifically used in agriculture and medicine as antibacterial, antifungal and antioxidants. It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus Candida albicans by binding Ag/Ag+ with the biomolecules present in the microbial cells. It has been suggested that Ag NPs produce reactive oxygen species and free radicals which cause apoptosis leading to cell death preventing their replication. Since Ag NPs are smaller than the microorganisms, they diffuse into cell and rupture the cell wall which has been shown from SEM and TEM images of the suspension containing nanoparticles and pathogens. It has also been shown that smaller nanoparticles are more toxic than the bigger ones. Ag NPs are also used in packaging to prevent damage of food products by pathogens. The toxicity of Ag NPs is dependent on the size, concentration, pH of the medium and exposure time to pathogens.

Broad‐spectrum inhibitory effect of green synthesised silver nanoparticles from Withania somnifera (L.) on microbial growth, biofilm and respiration: a putative mechanistic approach

Multi‐drug resistance in pathogenic bacteria has created immense clinical problem globally. To address these, there is need to develop new therapeutic strategies to combat bacterial infections. Silver nanoparticles (AgNPs) might prove to be next generation nano‐antibiotics. However, improved efficacy and broad‐spectrum activity is still needed to be evaluated and understood. The authors have synthesised AgNPs from Withania somnifera (WS) by green process and characterised. The effect of WS‐AgNPs on growth kinetics, biofilm inhibition as well as eradication of preformed biofilms on both gram‐positive and gram‐negative pathogenic bacteria was evaluated. The authors have demonstrated the inhibitory effect on bacterial respiration and disruption of membrane permeability and integrity. It was found that WS‐AgNPs inhibited growth of pathogenic bacteria even at 16 µg/ml. At sub‐minimum inhibitory concentration concentration, there was approximately 50% inhibition in biofilm formation which was further validated by light and electron microscopy. WS‐AgNPs also eradicated the performed biofilms by varying levels at elevated concentration. The bacterial respiration was also significantly inhibited. Interaction of WS‐AgNPs with test pathogen caused the disruption of cell membrane leading to leakage of cellular content. The production of intracellular reactive oxygen species reveals that WS‐AgNPs exerted oxidative stress inside bacterial cell causing microbial growth inhibition and disrupting cellular functions.

Green Adeptness in the Synthesis and Stabilization of Copper Nanoparticles: Catalytic, Antibacterial, Cytotoxicity, and Antioxidant Activities

Copper nanoparticles (CuNPs) are of great interest due to their extraordinary properties such as high surface-to-volume ratio, high yield strength, ductility, hardness, flexibility, and rigidity. CuNPs show catalytic, antibacterial, antioxidant, and antifungal activities along with cytotoxicity and anticancer properties in many different applications. Many physical and chemical methods have been used to synthesize nanoparticles including laser ablation, microwave-assisted process, sol-gel, co-precipitation, pulsed wire discharge, vacuum vapor deposition, high-energy irradiation, lithography, mechanical milling, photochemical reduction, electrochemistry, electrospray synthesis, hydrothermal reaction, microemulsion, and chemical reduction. Phytosynthesis of nanoparticles has been suggested as a valuable alternative to physical and chemical methods due to low cytotoxicity, economic prospects, environment-friendly, enhanced biocompatibility, and high antioxidant and antimicrobial activities. The review explains characterization techniques, their main role, limitations, and sensitivity used in the preparation of CuNPs. An overview of techniques used in the synthesis of CuNPs, synthesis procedure, reaction parameters which affect the properties of synthesized CuNPs, and a screening analysis which is used to identify phytochemicals in different plants is presented from the recent published literature which has been reviewed and summarized. Hypothetical mechanisms of reduction of the copper ion by quercetin, stabilization of copper nanoparticles by santin, antimicrobial activity, and reduction of 4-nitrophenol with diagrammatic illustrations are given. The main purpose of this review was to summarize the data of plants used for the synthesis of CuNPs and open a new pathway for researchers to investigate those plants which have not been used in the past. Graphical abstract Proposed Mechanism for Antibacterial activity of copper nanoparticles.

Inhibition of growth and biofilm formation of clinical bacterial isolates by NiO nanoparticles synthesized from Eucalyptus globulus plants

Nanotechnology based therapeutics has emerged as a promising approach for augmenting the activity of existing antimicrobials due to the unique physical and chemical properties of nanoparticles (NPs). Nickel oxide nanoparticles (NiO-NPs) have been suggested as prospective antibacterial and antitumor agent. In this study, NiO-NPs have been synthesized by a green approach using Eucalyptus globulus leaf extract and assessed for their bactericidal activity. The morphology and purity of synthesized NiO-NPs determined through various spectroscopic techniques like UV-Visible, FT-IR, XRD, EDX and electron microscopy differed considerably. The synthesized NiO-NPs were pleomorphic varying in size between 10 and 20 nm. The XRD analysis revealed the average size of NiO-NPs as 19 nm. The UV-Vis spectroscopic data showed a strong SPR of NiO-NPs with a characteristic spectral peak at 396 nm. The FTIR data revealed various functional moieties like C=C, C-N, C-H and O-H which elucidate the role of leaf biomolecules in capping and dispersal of NiO-NPs. The bioactivity assay revealed the antibacterial and anti-biofilm activity of NiO-NPs against ESβL (+) E. coli, P. aeruginosa, methicillin sensitive and resistant S. aureus. Growth inhibition assay demonstrated time and NiO-NPs concentration dependent decrease in the viability of treated cells. NiO-NPs induced biofilm inhibition was revealed by a sharp increase in characteristic red fluorescence of PI, while SEM images of NiO-NPs treated cells were irregular shrink and distorted with obvious depressions/indentations. The results suggested significant antibacterial and antibiofilm activity of NiO-NPs which may play an important role in the management of infectious diseases affecting human health.

Stable antibacterial silver nanoparticles produced with seed-derived callus extract of Catharanthus roseus

Biocompatibility and ecotoxicity concerns associated with chemically produced metallic nanoparticles have led to an increasing interest in the development of environmentally benign alternatives for nanoparticle synthesis using biological platforms. Herein, we report the utilization of an extract of seed-derived callus of Catharanthus roseus for the production of stable silver nanoparticles (Ag NPs). The bioreduction of silver ions was evident from UV-Vis spectroscopy results: the absorption maxima were observed at 425 nm, indicative of elemental silver. Transmission electron micrographs revealed that the Ag NPs were well-dispersed and predominantly spherical with particle sizes in the range of 2-15 nm. The synthesized Ag NPs exhibited colloidal stability in an aqueous dispersion for a period of 120 days, as indicated by UV-Vis absorbance spectra and zeta potential measurements. Fourier transform infrared spectroscopy revealed the possible utilization of hydroxyl groups and amides in the reduction of silver ions and surface stabilization of the Ag NPs, respectively. Notably, the synthesized Ag NPs showed considerable antibacterial action against Escherichia coli even after 8 weeks of storage under ambient conditions. Thus, cell extracts of cultured callus of Catharanthus roseus could be explored as an ecofriendly platform for the synthesis of stable and functional nanoparticles.

Biomimetic synthesis and anticancer activity of Eurycoma longifolia branch extract‐mediated silver nanoparticles

In the present study, silver nanoparticles (AgNPs) were synthesised by adding 1 mM Ag nitrate solution to different concentrations (1%, 2.5%, 5%) of branch extracts of Eurycoma longifolia, a well known medicinal plant in South–East Asian countries. Characterisation of AgNPs was carried out using techniques such as ultraviolet–visible spectrophotometry, X‐ray diffractrometry, Fourier transform infrared–attenuated total reflection spectroscopy (FTIR–ATR), scanning electron microscopy. XRD analysis revealed face centre cubic structure of AgNPs and FTIR–ATR showed that primary and secondary amide groups in combination with the protein molecules present in the branch extract were responsible for the reduction and stabilisation of AgNPs. Furthermore, antioxidant [2,2‐diphenyl‐1‐picrylhydrazyl and 2,2′‐Azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid)], antimicrobial and anticancer activities of AgNPs were investigated. The highest bactericidal activity of these biogenic AgNPs was found against Escherichia coli with zone inhibition of 11 mm. AgNPs exhibited significant anticancer activity against human glioma cells (DBTRG and U87) and human breast adenocarcinoma cells (MCF‐7 and MDA‐MB‐231) with IC50 values of 33, 42, 60 and 38 µg/ml.

Evaluation of anti-bacterial effects of nickel nanoparticles on biofilm production by Staphylococcus epidermidis

BACKGROUND AND OBJECTIVES

Staphylococcus epidermidis produces biofilm by extracellular polysaccharides, causing bacterial adherence to different surfaces. Anti-microbial effects of nickel nanoparticles on some bacterial strains such as S. aureus and Escherichia coli have been determined in limited studies. The aim of the present study is to examine the inhibitory effect of nickel nanoparticles on biofilm formation using clinical isolates of S. epidermidis and its hemolytic effect on human red blood cells.

MATERIALS AND METHODS

Twenty two S. epidermidis isolates were collected and identified by standard microbiological methods. Microtiter plate method was used to determine the biofilm production in bacterial isolates. The amounts of biofilm formation by isolates in the presence of 0.01, 0.05, 0.1, and 1 mg/mL concentrations of nickel nanoparticles were measured. Hemolytic activity of different concentrations of nickel nanoparticles was measured on human RBC suspensions.

RESULTS

Twenty isolates were strong, and two isolates were moderate biofilm producers. Biofilm formation significantly decreased in the presence of 0.05, 0.1, and 1 mg/mL of nickel nanoparticles (p<0.05). Although in the presence of 0.01 mg/mL of nickel nanoparticles, decrease in biofilm formation was observed but it was not statistically significant (p=0.448). Slight hemolytic activity was seen in the presence of nickel nanoparticles.

CONCLUSION

In this study, the ability of biofilm production was demonstrated for all clinical isolates of S. epidermidis. On the other hand, the lowering effects of nickel nanoparticles on biofilm formation were observed.

Potential impacts of silver nanoparticles on bacteria in the aquatic environment

It is inevitable that nano-silver will be released into the environment. Therefore, there is an urgent need to better understand the effects of silver nanoparticles (Ag-NPs) on microbes in natural and engineered environments. The most remarkable gap in our knowledge on this lies on the low Ag-NPs dose side. This review summarized studies on the effects of Ag-NPs on bacteria from simple to complicated aquatic systems. A hormetic model with a narrow stimulatory zone has been proposed based on both experimental phenomenon and the potential mechanisms of the observed effects. Spectrum of the stimulating zone depends on Ag-NP properties, bacterial types and environmental conditions tested. This may become a concern in terms of Ag-NP disposal, and further research is required to build a sophisticated toxicity model for Ag-NPs.

Nano-zirconia - Evaluation of its antioxidant and anticancer activity

Bioactivity of nanomaterials largely depends on its size, shape and crystalline nature. In this work, the smaller sized spherical shaped nano-zirconia (ZrO₂ NPs) (of ~9 to 11nm) was fabricated and studied its biological activity especially antioxidant and cytotoxicity against human colon carcinoma (HCT-116) and human lung carcinoma (A-549) cell lines. To have its real applications in biological aspects readily available Eucalyptus globulus (E. globulus) leaf extract was used as an effective capping and reducing agent for its synthesis. The prepared ZrO₂ NPs was characterized by using different sophisticated instrumentations such as UV-visible spectrophotometer, XRD, FTIR, TEM, SAED, EDX, DLS and fluorescence spectroscopy. Cellular mitochondrial activity i.e. cell viability was measured by MTT assay and anti-oxidant activity was determined by DPPH assay. The smaller sized ZrO₂ NPs showed strong antioxidant activity as well as cytotoxicity on human cancer cell lines. Comparative cytotoxic studies were conducted on human cancerous cell lines using different techniques. Results confirmed the efficient anti-cancer activities of the fabricated ZrO₂ NPs towards the tested cell lines as well as efficient anti-oxidant activity. This is the first study in which E. globulus leaf extract was used to synthesize smaller spherical shaped ZrO₂ NPs for improved bioactivity i.e. antioxidant and cytotoxicity.

A review on green synthesis of silver nanoparticles and their applications

Development of reliable and eco-accommodating methods for the synthesis of nanoparticles is a vital step in the field of nanotechnology. Silver nanoparticles are important because of their exceptional chemical, physical, and biological properties, and hence applications. In the last decade, numerous efforts were made to develop green methods of synthesis to avoid the hazardous byproducts. This review describes the methods of green synthesis for Ag-NPs and their numerous applications. It also describes the comparison of efficient synthesis methods via green routes over physical and chemical methods, which provide strong evidence for the selection of suitable method for the synthesis of Ag-NPs.

Biopolymers Regulate Silver Nanoparticle under Microwave Irradiation for Effective Antibacterial and Antibiofilm Activities

In the current study, facile synthesis of carboxymethyl cellulose (CMC) and sodium alginate capped silver nanoparticles (AgNPs) was examined using microwave radiation and aniline as a reducing agent. The biopolymer matrix embedded nanoparticles were synthesized under various experimental conditions using different concentrations of biopolymer (0.5, 1, 1.5, 2%), volumes of reducing agent (50, 100, 150 μL), and duration of heat treatment (30 s to 240 s). The synthesized nanoparticles were analyzed by scanning electron microscopy, UV-Vis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy for identification of AgNPs synthesis, crystal nature, shape, size, and type of capping action. In addition, the significant antibacterial efficacy and antibiofilm activity of biopolymer capped AgNPs were demonstrated against different bacterial strains, Staphylococcus aureus MTCC 740 and Escherichia coli MTCC 9492. These results confirmed the potential for production of biopolymer capped AgNPs grown under microwave irradiation, which can be used for industrial and biomedical applications.

Silver Nanocoating Technology in the Prevention of Prosthetic Joint Infection

Prosthetic joint infection (PJI) is a feared complication of total joint arthroplasty associated with increased morbidity and mortality. There is a growing body of evidence that bacterial colonization and biofilm formation are critical pathogenic events in PJI. Thus, the choice of biomaterials for implanted prostheses and their surface modifications may significantly influence the development of PJI. Currently, silver nanoparticle (AgNP) technology is receiving much interest in the field of orthopaedics for its antimicrobial properties and a strong anti-biofilm potential. The great advantage of AgNP surface modification is a minimal release of active substances into the surrounding tissue and a long period of effectiveness. As a result, a controlled release of AgNPs could ensure antibacterial protection throughout the life of the implant. Moreover, the antibacterial effect of AgNPs may be strengthened in combination with conventional antibiotics and other antimicrobial agents. Here, our main attention is devoted to general guidelines for the design of antibacterial biomaterials protected by AgNPs, its benefits, side effects and future perspectives in PJI prevention.

Antimicrobial Drugs in Fighting against Antimicrobial Resistance

The outbreak of antimicrobial resistance, together with the lack of newly developed antimicrobial drugs, represents an alarming signal for both human and animal healthcare worldwide. Selection of rational dosage regimens for traditional antimicrobial drugs based on pharmacokinetic/pharmacodynamic principles as well as development of novel antimicrobials targeting new bacterial targets or resistance mechanisms are key approaches in tackling AMR. In addition to the cellular level resistance (i.e., mutation and horizontal gene transfer of resistance determinants), the community level resistance (i.e., bilofilms and persisters) is also an issue causing antimicrobial therapy difficulties. Therefore, anti-resistance and antibiofilm strategies have currently become research hotspot to combat antimicrobial resistance. Although metallic nanoparticles can both kill bacteria and inhibit biofilm formation, the toxicity is still a big challenge for their clinical applications. In conclusion, rational use of the existing antimicrobials and combinational use of new strategies fighting against antimicrobial resistance are powerful warranties to preserve potent antimicrobial drugs for both humans and animals.