Rapid and green synthesis of cadmium telluride quantum dots with low toxicity based on a plant-mediated approach after microwave and ultrasonic assisted extraction: Synthesis, characterization, biological potentials and comparison study

Nanomaterial in controlling biofilms and virulence of microbial pathogens

The escalating threat of antimicrobial resistance (AMR) poses a grave concern to global public health, exacerbated by the alarming shortage of effective antibiotics in the pipeline. Biofilms, intricate populations of bacteria encased in self-produced matrices, pose a significant challenge to treatment, as they enhance resistance to antibiotics and contribute to the persistence of organisms. Amid these challenges, nanotechnology emerges as a promising domain in the fight against biofilms. Nanomaterials, with their unique properties at the nanoscale, offer innovative antibacterial modalities not present in traditional defensive mechanisms. This comprehensive review focuses on the potential of nanotechnology in combating biofilms, focusing on green-synthesized nanoparticles and their associated anti-biofilm potential. The review encompasses various aspects of nanoparticle-mediated biofilm inhibition, including mechanisms of action. The diverse mechanisms of action of green-synthesized nanoparticles offer valuable insights into their potential applications in addressing AMR and improving treatment outcomes, highlighting novel strategies in the ongoing battle against infectious diseases.

Green tea waste-derived carbon dots: efficient degradation of RhB dye and selective sensing of Cu2+ ions

Herein, we have synthesized carbon dots (CDs) using a one-step hydrothermal method from green tea waste, a biomass-derived source with high fluorescent properties and excellent solubility in water. The synthesis of CDs was confirmed through a comprehensive range of characterization techniques, including HRTEM (high-resolution transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), and EDX (energy-dispersive X-ray spectroscopy). The optical properties of the synthesized CDs were assessed using UV-Vis spectroscopy and fluorescence (FL) spectroscopy. The CDs displayed exceptional stability across a wide pH range and various concentrations. Moreover, these CDs exhibited a photoluminescence quantum yield (PLQY) of 21.6%, indicating their efficiency in emitting fluorescent light upon excitation. The CDs also showcased their prowess in fluorometrically detecting Cu2+ ions, displaying high sensitivity and selectivity. They presented two distinct linear ranges: 0.02 to 50 µM and 50 to 100 µM, with recovery rates ranging from 94.2 to 104.06%. Moreover, under visible light irradiation, the CDs exhibited significant efficiency in the photocatalytic removal of dyes. Specifically, the CDs achieved degradation rate of 97.89% for Rhodamine B (RhB) within a 30-min irradiation period. In the context of RhB adsorption, it is evident that the experimental data align more closely with the Freundlich isotherm than the Langmuir isotherm. This is substantiated by a higher R2 value (0.97) for the Freundlich isotherm model compared to the Langmuir adsorption isotherm model (0.93). Notably, the adsorption kinetics was effectively described by pseudo first-order kinetics models. Overall, these results highlight the promising potential of CDs in applications such as environmental remediation and waste treatment processes due to their photocatalytic and sensing capabilities.

Sonochemical-assisted synthesis of copper oxide nanoparticles with the plant-mediated approach and comparative evaluation of some biological activities

The present study reported a green approach for the sonochemical-assisted synthesis (SAS) of copper oxide nanoparticles (CuO NPs) by using the aqueous extract of the Ficus johannis plant. The aqueous extract was obtained using ultrasonic-assisted extraction (15 min, 45 °C) and microwave-assisted extraction (15 min, 450 w). Next, the as-prepared extracts were used in a plant-mediated approach for the green synthesis of CuO NPs. The synthesized CuO NPs have been characterized via different techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), ultraviolet-visible absorption, photoluminescence, and Fourier-transformed infrared (FT-IR) spectroscopic techniques. As observed, a broad absorption band around 375 nm clarified the successful synthesis of CuO NPs. From the SEM analysis, the average particle size of the prepared CuO NPs was estimated below 50 nm. In addition, the antimicrobial, antioxidant, and antifungal properties of the aqueous extracts as well as the as-prepared CuO NPs were evaluated by different assays. These included the release of protein, nucleic acids, disk diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and time-killing assays.

Synergistic action of sumatriptan delivery and targeting magnesium deficiency using green, pH-responsive MgO nanoparticles synthesized from mahua flower extracts

Magnesium oxide (MgO) nanoparticles were green synthesized using mahua (Madhuca longifolia) flower extracts by solvent evaporation and characterized by UV-visible spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and Energy dispersive X-ray analysis (EDX). The drug loading of sumatriptan succinate (SS), an anti-migraine drug, was optimized using MINITAB's response surface methodology (RSM) Box Behnken model (BBD) model. The investigation of drug adsorption and release kinetics was further conducted using the optimized set obtained through RSM. The optimized parameters consisted of 23.53 mg of nanoparticles, a loading time of 6 h, and a pH of 9, yielding the experimental drug loading efficiency ~47%. The primary objective of this study is to investigate the potential of utilizing these green synthesized MgO nanoparticles for a dual purpose. The primary objective of this study is to investigate the viability of utilizing MgO nanoparticles synthesized through green route for the delivery of an anti-migraine medication. Additionally, the study aims to examine the degradation of these nanoparticles at physiological pH levels, with the intention of potentially enhancing cellular absorption. The investigation involved the assessment of drug release kinetics using various mathematical models, with a focus on the release of SS from MgO nanoparticles. This evaluation was conducted at different pH levels, specifically pH 5, 7, and 9. It has been found that the SS release increases as pH decreases, which is attributed to the dissolution of MgO nanoparticles, which therefore exhibits varied behavior at different pHs. The confirmation of the degradation of the green synthesized MgO nanoparticles was achieved through the execution of a degradation study, followed by the analysis of the obtained samples using FESEM and EDS. At neutral, the release data obtained adhered to the Higuchi model, which suggests that the release of the drug is based on diffusion. This finding is particularly advantageous for the controlled release of an anti-migraine drug. The results obtained from the study indicate that MgO nanoparticles have the potential to serve as a significant component in drug delivery systems, specifically as drug carriers. Attachment of SS over MgO nanoparticles to form SS loaded MgO nanoparticles and its possible working mechanism.

Magnetic sporopollenin supported magnesium nanoparticles for removal of tetracycline as an emerging contaminant from water

Since the release of antibiotics as emerging contaminants into the environmental water can cause severe difficulties for human health, their removal from the water is necessary. In this regard, a novel environmentally friendly adsorbent was developed based on green sporopollenin, which was magnetized and modified with magnesium oxide nanoparticles to produce MSP@MgO nanocomposite. The newly developed adsorbent was applied to remove tetracycline antibiotic (TC) from aqueous media. The surface morphology of the MSP@MgO nanocomposite was characterized using FTIR, XRD, EDX, and SEM techniques. The effective parameters of the removal process were studied, and it was confirmed that the chemical structure of TC was highly affected by changes in pH solution due to different pKa; therefore, the results showed that pH 5 was the optimum. Also, the maximum sorption capacity of MSP@MgO for TC for adsorption was obtained at 109.89 mg.g^-1. In addition, the adsorption models were investigated, and the process was fitted with the Langmuir model. Thermodynamic parameters showed that the process was spontaneous (ΔG < 0), endothermic (ΔH > 0) and the adsorption mechanism was following the physisorption mechanism at room temperature.

Current trends in carbon-based quantum dots development from solid wastes and their applications

Urbanization and a massive population boom have immensely increased the solid wastes (SWs) generation and are expected to reach 3.40 billion tons by 2050. In many developed and emerging nations, SWs are prevalent in both major and small cities. As a result, in the current context, the reusability of SWs through various applications has taken on added importance. Carbon-based quantum dots (Cb-QDs) and their many variants are synthesized from SWs in a straightforward and practical method. Cb-QDs are a new type of semiconductor that has attracted the interest of researchers due to their wide range of applications, which include everything from energy storage, chemical sensing, to drug delivery. This review is primarily focused on the conversion of SWs into useful materials, which is an essential aspect of waste management for pollution reduction. In this context, the goal of the current review is to investigate the sustainable synthesis routes of carbon quantum dots (CQDs), graphene quantum dots (GQDs), and graphene oxide quantum dots (GOQDs) from various types SWs. The applications of CQDs, GQDs, and GOQDs in the different areas are also been discussed. Finally, the challenges in implementing the existing synthesis methods and future research directions are highlighted.

Plant-assisted synthesis and characterization of MnO2 nanoparticles for removal of crystal violet dye: an environmental remedial approach

The current study is focused on the use of the Caryota mitis Lour. (Fishtail palm) flower extract as a reducing agent for the preparation of manganese dioxide (MnO₂) nanoparticles. Scanning electron microscopy (SEM), four-phase infrared analysis (FT-IR), and x-ray diffraction (XRD) methods were used to characterize the MnO₂ nanoparticles. The nature of MnO₂ nanoparticles was revealed by an absorption peak at 590 nm in a spectrophotometer (A1000). Then, these MnO₂ nanoparticles were applied to decolorize the crystal violet dye. At 0.004% dye concentration, pH 4, and concentration of MnO₂ nanoparticles of 0.005 g/L at temperatures of 50 °C, the target dye was decolorized by 91.3%. Percent reductions in COD and TOC were found to be 92.1% and 90.6%, respectively. Finally, the dye decolorization pathway was proposed based on the experimental findings.

Photo-catalytic and biomedical applications of one-step, plant extract-mediated green-synthesized cobalt oxide nanoparticles

In the present work, for the first time, green chemically synthesized and stabilized Co₃O₄ nanoparticles were employed for catalytic conversion of isopropyl alcohol to acetone by dehydrogenation of IPA. Plant extract of Rosmarinus officinalis was used as a reducing and stabilizing agent for this synthesis. The biosynthesized Co₃O₄ nanoparticles were annealed at 450℃ followed by their physiochemical characterizations through XRD, SEM, AFM, and FTIR. Size distribution information collected through XRD and AFM back each other, and it was found to be 6.5 nm, having the highest number of nanoparticles in this size range. While SEM confirms the self-arranging property of synthesized nanoparticles due to their magnetic nature, furthermore, the biogenic Co₃O₄ nanoparticles were studied for their catalytic potential to convert isopropyl alcohol to acetone with the help of a UV-Visible spectrophotometer. The highest photocatalytic conversion of 99% was obtained in time period of 48 s. For the first time ever, nanoparticles were used for 5 cycles to evaluate their recyclable nature and conversion fell from 99 to 86% and the end of the 5th cycle. Later anti-bacterial activity against 3 Gram-positive and 3 Gram-negative strains gave the highest inhibition value of 99% against Streptococcus pneumoniae at 500 µg/mL. Finally, a cytotoxicity study on synthesized nanomaterials was carried out by exposing freshly drawn human macrophages to them. It was found that even at the highest concentration of 500 µg/mL, the nanoparticles showed only 28% lysis.

Interaction of a natural compound nanoemulsion with Gram negative and Gram positive bacterial membrane; a mechanism based study using a microfluidic chip and DESI technique

The antibacterial activity of a nanoemulsion prepared from Satureja Khusitanica essential oil against a Gram-negative (Escherichia coli) and a Gram-positive (Bacillus atrophaeus) bacteria evaluated using microfluidic and conventional techniques. The effect of different residence time and concentrations on the antibacterial activity of nanoemulsion was studied by measuring the release of protein, nucleic acids, potassium, and also recording the MIC, MBC and time killing assays. Remarkable intensification was observed by employing microfluidic chip regarding a high-contact surface area between nanodroplets and bacterial membrane. The MIC and MBC values for E. coli and B. atrophaeus in conventional method were 400 and 1600 µg mL^-1, respectively, whereas these values reduced to 11 to 50 µg mL^-1 using microfluidic system. B. atrophaeus seemed to be more resistant than E. coli to the nanoemulsion treatment, perhaps due to different cell wall structures. Bacterial cell wall changes were examined using a desorption electrospray ionization (DESI) technique. It was found that the structural changes were more imminent in Gram negative E. coli by detecting a number of released lipids including phosphatidyl glycerol and phosphatidyl ethanolamines. The DESI spectra of B. atrophaeus revealed no M/Z related lipid release. These findings may help providing novel nano based natural antibacterials.

Sulfide-Doped Magnetic Carbon Nanotubes Developed as Adsorbent for Uptake of Tetracycline and Cefixime from Wastewater

In this study, a magnetic solid-phase extraction method was developed based on multi-wall carbon nanotubes decorated by magnetic nanoparticles (Fe₃O₄) and cadmium sulfide nanoparticles (Fe₃O₄@MWCNT-CdS) for trace extraction of cefixime and tetracycline antibiotics from urine and drug company wastewater. The adsorbent features were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and energy dispersive X-ray analysis (EDX). Various effective parameters on the sorption and desorption cycle, such as sorption time, the mass of adsorbent, pH, salt addition, and material ratio, were investigated and optimized. The data were evaluated using isotherm models, and experimental data were well-fitted to both Langmuir (R² = 0.975) and Freundlich (R² = 0.985) models. Moreover, kinetic of reaction was agreement with pseudo-second-order (R² = 0.999) as compared pseudo-first-order (R² = 0.760). The maximum adsorption capacity for tetracycline and cefixime was achieved at 116.27 and 105.26 mg·g^-1, respectively. Hence, the prepared adsorbent can be used as an alternative material for enhanced determination of pharmaceutical substances in biological fluids.

Magnetic Beads of Zero Valent Iron Doped Polyethersolfun Developed for Removal of Arsenic from Apatite-Soil Treated Water

The drop immerses calcium chloride aqueous solution was utilized to prepare the zero valent iron-doped polyethersulfone beads (PES/ZVI) for the efficient removal of arsenic from apatite-soil treated waters. The proposed beads can assist in promoting uptake efficiency by hindering ZVI agglomeration due to a high porosity and different active sites. The PES/ZVI beads were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetism (VSM). The main objective of this study was to investigate the function of new PES/ZVI beads with an increased removal efficiency for the remediation of arsenic ions from the apatite-soil treated waters. A maximum adsorption removal of 82.39% was achieved when the experiment was performed with 80 mg of adsorbent for a contact time of 180 min. Based on the results, a removal efficiency >90% was obtained after 300 min of shaking time with an arsenic concentration of 20 mg·L^-1. The experimental process was fitted with the Langmuir model due to the high R² (0.99) value compared to the Freundlich model (0.91) with an adsorption capacity of 41.32 mg·g^-1. The adsorption process speed was limited by pseudo-second-order (R² = 0.999) and the adsorption mechanism nature was endothermic and physical.

Highly sensitive and selective colorimetric detection of Pb(ii) ions using Michelia tonkinensis seed extract capped gold nanoparticles

In this study, gold nanoparticles (AuNPs) were synthesized via a green and environmentally-friendly approach and applied as a colorimetric probe for detecting Pb2+ ions in aqueous solution. Instead of toxic chemicals, Michelia tonkinensis (MT) seed extract was used for reducing Au3+ and stabilizing the formed AuNPs. The synthesis conditions, including temperature, reaction time, and Au3+ ion concentration, were optimized at 90 °C, 40 min, and 1.25 mM, respectively. The physicochemical properties of the produced MT-AuNPs were assessed by means of transmission electron microscopy, X-ray diffraction, field emission scanning electron microscopy, dynamic light scattering, and Fourier-transform infrared spectroscopy. The characterization results revealed that the MT-AuNPs exhibited a spherical shape with a size of about 15 nm capped by an organic layer. The colorimetric assay based on MT-AuNPs showed excellent sensitivity and selectivity toward Pb2+ ions with the limit of detection value of 0.03 μM and the limit of quantification of 0.09 μM in the linear range of 50-500 μM. The recoveries of inter-day and intra-day tests were 97.84-102.08% and 98.78-102.34%, respectively. The MT-AuNPs probe also demonstrated good and reproducible recoveries (98.71-101.01%) in analyzing Pb2+ in drinking water samples, indicating satisfactory practicability and operability of the proposed method.

Synthesis of sulfhydryl functionalized silicon quantum dots with high quantum yield for imaging of hypochlorite in cells and zebrafish

Sulfhydryl functionalized silicon quantum dots (S-SiQDs) with a fluorescence quantum yield of 38.5% were synthesized using 3-mercaptopropyltrimethoxysilane (MPTMS) and m-phenylenediamine by a simple one-pot method. It is worth noting that by oxidizing the surface sulfhydryl groups and statically quenching, the fluorescence of S-SiQDs at 492 nm (excitation at 383 nm) can be selectively quenched by hypochlorite (ClO^-) in a linear range of 0.05 to 1.8 μM with a low detection limit of 13 nM. The reaction was completed in 10 s with no interference from other ROS, metal ions, anions and reducing species. The silicon source containing sulfhydryl groups was used to synthesize silicon quantum dots for the first time, and the surface of the S-SiQDs was provided with sulfhydryl groups and reacted rapidly and sensitively with ClO^-. The S-SiQDs have good photostability and biocompatibility, and can be further used for ClO^- imaging in MCF-7 cells and zebrafish, showing great promise in biological imaging. The proposed assay demonstrates that 3-mercaptopropyltrimethoxysilane is a good choice to obtain a functionalized fluorescent nanoprobe for redox species.

Latest Trends in Lateral Flow Immunoassay (LFIA) Detection Labels and Conjugation Process

LFIA is one of the most successful analytical methods for various target molecules detection. As a recent example, LFIA tests have played an important role in mitigating the effects of the global pandemic with SARS-COV-2, due to their ability to rapidly detect infected individuals and stop further spreading of the virus. For this reason, researchers around the world have done tremendous efforts to improve their sensibility and specificity. The development of LFIA has many sensitive steps, but some of the most important ones are choosing the proper labeling probes, the functionalization method and the conjugation process. There are a series of labeling probes described in the specialized literature, such as gold nanoparticles (GNP), latex particles (LP), magnetic nanoparticles (MNP), quantum dots (QDs) and more recently carbon, silica and europium nanoparticles. The current review aims to present some of the most recent and promising methods for the functionalization of the labeling probes and the conjugation with biomolecules, such as antibodies and antigens. The last chapter is dedicated to a selection of conjugation protocols, applicable to various types of nanoparticles (GNPs, QDs, magnetic nanoparticles, carbon nanoparticles, silica and europium nanoparticles).

Very rapid synthesis of highly efficient and biocompatible Ag2Se QD phytocatalysts using ultrasonic irradiation for aqueous/sustainable reduction of toxic nitroarenes to anilines with excellent yield/selectivity at room temperature

There are many problems associated with the synthesis of nanocatalysts and catalytic reduction of nitroarenes - e.g., high temperatures, costs, long reaction/synthesis process times, the toxicity of chemicals/solvents, undesirable byproducts, the toxic/harmful wastes, low efficiency/selectivity, etc. This study represents an attempt to overcome these challenges. To this purpose, biocompatible and highly efficient Ag₂Se quantum dots (QDs) catalysts with antibacterial activity were synthesized in a very rapid (30 sec, rt), simple, inexpensive, sustainable/green, and one-pot strategy in water using ultrasonic irradiation. Characterization of the QDs was performed using different techniques. UV-Vis absorption and fluorescence spectroscopic studies showed an absorption peak at 480-550 nm and a maximum emission peak around 675 nm, which confirmed the successful synthesis of Ag₂Se QDs via the applied biosynthetic method. Subsequently, catalytic reduction of nitroarenes by them was carried out under safe conditions (H₂O, rt, air atmosphere) in ∼ 60 min with excellent yield and selectivity (>99%). Their catalytic activity in the reduction of various toxic nitroarenes to aminoarenes under green conditions was investigated. Thus, a rapid and safe ultrasound-based method was employed to prepare stable and green Ag₂Se QDs phyto-catalysts with unique properties, including exquisite monodispersity in shape (orthorhombic) and size (∼7 nm), air-stability, and good purity and crystallinity. Importantly, instead of various toxic chemicals, the plant extract obtained by rapid ultrasonic method (10 min, rt) was used as natural reducing, capping, and stabilizing agents. Moreover, antibacterial assays results showed that Ag₂Se-QDs catalysts at low concentrations (ppm) have high activity against all tested bacteria, especially E. coli (MIC:31.25 ppm, MBC:125 ppm) which were significantly different from those of Fig extract (MIC = MBC:500 ppm). The data reflect the role of these bio-synthesized Ag₂Se-QDs catalysts in the development of versatile and very safe catalysts with biomedical properties.

Emerging Roles of Green-Synthesized Chalcogen and Chalcogenide Nanoparticles in Cancer Theranostics

The last few decades have seen an overwhelming increase in the amount of research carried out on the use of inorganic nanoparticles. More fascinating is the tremendous progress made in the use of chalcogen and chalcogenide nanoparticles in cancer theranostics. These nanomaterials, which were initially synthesized through chemical methods, have now been efficiently produced using different plant materials. The paradigm shift towards the biogenic route of nanoparticle synthesis stems from its superior advantages of biosafety, eco-friendliness, and simplicity, among others. Despite a large number of reviews available on inorganic nanoparticle synthesis through green chemistry, there is currently a dearth of information on the green synthesis of chalcogens and chalcogenides for cancer research. Nanoformulations involving chalcogens such as sulfur, selenium, and tellurium and their respective chalcogenides have recently emerged as promising tools in cancer therapeutics and diagnosis. Similar to other inorganic nanoparticles, chalcogens and chalcogenides have been synthesized using plant extracts and their purified biomolecules. In this review, we provide an up-to-date discussion of the recent progress that has been made in the plant-mediated synthesis of chalcogens and chalcogenides with a special focus on their application in cancer theranostics.

Reuse of waste Myrica rubra for green synthesis of nitrogen-doped carbon dots as an "on-off-on" fluorescent probe for Fe3+ and ascorbic acid detection

As one kind of high nutrition fruits, abandoned Myrica rubra causes great waste due to short storage period. For resource utilization, we herein fabricated the Myrica rubra-based N-doped carbon dots (MN-CDs) by a facile/green hydrothermal method. MN-CDs, fabricated from four regions of China, displayed significant differences in their corresponding fluorescence intensities (FIs). Interestingly, different batches of waxberry samples from the same region (Wenzhou, China) exhibited slight differences in their FIs, and also an excellent anti-photobleaching and anti-salt capacity. Based on Fe³⁺-triggered quenching effect and fluorescent recovery by redox reaction of AA and Fe³⁺, MN-CDs were employed to construct an "on-off-on" switch probe for sequential detection of Fe³⁺ and ascorbic acid (AA). Through Zeta potential, UV spectrum, Stern-Volmer equation, and valence-conduction band theory, the Fe³⁺-triggered quenching belonged to a static quenching process, which resulted from the synergistic contribution of inner filtering effect and photo-induced electron transfer mechanisms. The linear ranges for Fe³⁺ and AA detections were 1-1000 and 0.1-1000 mM. The limits of detection were 0.3 μM for Fe³⁺ in environmental waters, and 0.03 μM for AA in pharmaceutical tablets and fruit juice samples. Under 365-nm UV lamp, the color changes of test papers were easily observed from dark blue and bright blue in the presence of Fe³⁺ and AA, and thus the MN-CDs-based switch probe could be satisfactorily used for visually qualitative detection of Fe³⁺ and AA outdoor with our naked eyes. To sum up, MN-CDs not only realize resource reutilization of abandoned Myrica rubra, but also offer an convenient outdoor approach for qualitative detection of Fe³⁺ and AA in complex matrices.

Current advances in bio-fabricated quantum dots emphasising the study of mechanisms to diversify their catalytic and biomedical applications

Quantum dots (QDs), owing to their single atom-like electronic structure due to quantum confinement, are often referred to as artificial atoms. This unique physical property results in the diverse functions exhibited by QDs. A wide array of applications have been achieved by the surface functionalization of QDs, resulting in exceptional optical, antimicrobial, catalytic, cytotoxic and enzyme inhibition properties. Ordinarily, traditionally prepared QDs are subjected to post synthesis functionalization via a variety of methods, such as ligand exchange or covalent and non-covalent conjugation. Nevertheless, solvent toxicity, combined with the high temperature and pressure conditions during the preparation of QDs and the low product yield due to multiple steps in the functionalization, limit their overall use. This has driven scientists to investigate the development of greener, environmental friendly and cost-effective methods that can circumvent the complexity and strenuousness associated with traditional processes of bio-functionalization. In this review, a detailed analysis of the methods to bio-prepare pre-functionalized QDs, with elucidated mechanisms, and their application in the areas of catalysis and biomedical applications has been conducted. The environmental and health and safety aspects of the bio-derived QDs have been briefly discussed to unveil the future of nano-commercialization.

A microfluidic chip for visual investigation of the interaction of nanoemulsion of Satureja Khuzistanica essential oil and a model gram-negative bacteria

Nanotechnology has provided novel approaches against food born and pathogenic bacteria. Within the present study, the effects of pure and nanoemulsified essential oil derived from Satureja Khuzistanica essential oil (SKEO) on Escherichia coli (E. coli ATCC 25922) as a human pathogen has been studied using a microfluidic chip. The morphology and antibacterial activity of E. coli at disparate residence durations (from 2 to 30 min) and various nanoemulsified or pure essential oil concentrations (8.0-62.5 μg mL^-1) and numerous nanoemulsion's droplet sizes from 32 to 124 nm, have been investigated in the microfluidic system. Also, the quantitative analysis including optical density, time killing assay, protein, nucleic acid and potassium release were employed to confirm the effects of bacterial inhibition taking advantage of the chip apparatus. It was revealed that the prepared nanoemulsion left a considerable destructive effect on E. coli bacterial membrane, confirmed by fast release of cytoplasmic elements including protein, nucleic acid and potassium. However, this process was remarkably intensified for both nanoemulsion and pure essential oil using the microfluidic chip versus the conventional methods. The results also revealed that after 4 min of bacterium treatment by 12.5 μg mL^-1 nanoemulsion with 32 nm mean particle size, the bacterial membrane wall began to degrade rapidly, and bacterial activity was almost completely inhibited in a 20-min period. These findings may have implications in the similarly structured and phospholipid-encapsulated bacteria and viruses, like COVID-19.

Evaluation of Phytotoxicity of Bimetallic Ag/Au Nanoparticles Synthesized Using Geum urbanum L

The growing production and wider application of metal nanoparticles gives rise to many concerns about their release to natural ecosystems. It is very important to be aware of the harmful impact of nanoparticles on living organisms, including plants. Therefore, it is of vital significance to explore the impact of metal nanoparticles on plants. This work assessed the phytotoxicity of bimetallic Ag/Au nanoparticles and Geum urbanum L. extract. The obtained bimetallic Ag/Au nanoparticles were characterized by UV–vis spectrophotometry (UV–vis), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The microscopic studies enabled the determination of the size of the obtained nanoparticles, which was 50 nm. The wide range of concentrations evaluated in the course of the study made it possible to observe changes in selected plants (seeds of Lepidium sativum, Linum flavum, Zea mays, Solanum lycopersicum var. Cerasiforme and Salvia hispanica-Chia) caused by a stress factor. The studies showed that the solution of Ag/Au nanoparticles was most toxic to flax (IC50 = 9.83 × 10–6/9.25 × 10–6 mg/ml), and least toxic to lupine (IC50 = 1.23 × 10–3/1.16 × 10–3 mg/ml). Moreover, we studied the toxicity of Geum urbanum extract. The extracts diluted to 0.00875 mg/ml stimulated the growth of lupine, flax and garden cress; extracts diluted to 0.175 mg/ml stimulated the growth of Chia and tomatoes; and extracts diluted to 0.00875 mg/ml stimulated the growth of corn. G. urbanum extract was most toxic to lupine (IC50 = 0.374 mg/ml), and least toxic to corn (IC50 = 4.635 mg/ml).

Synthesis of arylidene hydrazinylpyrido[2,3-d]pyrimidin-4-ones as potent anti-microbial agents

Combination of arylidene hydrazinyl moiety with pyrido[2,3-d]pyrimidin-4-one skeleton in compounds 7‒26 results in the output of unprecedented anti-microbial agents. Arylidene hydrazinyl based on Pyrido[2,3-d]pyrimidin-4-one analoges 7‒26 prepared by the treatment of [2,3-d]pyrimidin-4-ones 6a,b with various aromatic aldehydes. The antimicrobial action for recently synthesized compounds was considered towards gram positive bacterial species (Staphylococcus aurous ATCC- 47077; Bacillus cereus ATCC-12228), gram negative bacterial species (Escherichia coli ATCC-25922; Salmonella typhi ATCC-15566) and Candida albicans ATCC-10231 as fungal strains. The antimicrobial action expanded by expanding the electron donating group in position 2 and 5 for Pyrido[2,3-d]pyrimidin-4-one core. Derivatives 13, 14, 15, 16 and 12; individually appeared hopeful anti-microbial action towards all strains utilized with inhibition zone higher than that of standard reference drug with lowest MIC.

Study of Physico-Chemical Changes of CdTe QDs after Their Exposure to Environmental Conditions

The irradiance of ultraviolet (UV) radiation is a physical parameter that significantly influences biological molecules by affecting their molecular structure. The influence of UV radiation on nanoparticles has not been investigated much. In this work, the ability of cadmium telluride quantum dots (CdTe QDs) to respond to natural UV radiation was examined. The average size of the yellow QDs was 4 nm, and the sizes of green, red and orange QDs were 2 nm. Quantum yield of green CdTe QDs-MSA (mercaptosuccinic acid)-A, yellow CdTe QDs-MSA-B, orange CdTe QDs-MSA-C and red CdTe QDs-MSA-D were 23.0%, 16.0%, 18.0% and 7.0%, respectively. Green, yellow, orange and red CdTe QDs were replaced every day and exposed to daily UV radiation for 12 h for seven consecutive days in summer with UV index signal integration ranging from 1894 to 2970. The rising dose of UV radiation led to the release of cadmium ions and the change in the size of individual QDs. The shifts were evident in absorption signals (shifts of the absorbance maxima of individual CdTe QDs-MSA were in the range of 6–79 nm), sulfhydryl (SH)-group signals (after UV exposure, the largest changes in the differential signal of the SH groups were observed in the orange, green, and yellow QDs, while in red QDs, there were almost no changes), fluorescence, and electrochemical signals. Yellow, orange and green QDs showed a stronger response to UV radiation than red ones.

CdSe quantum dots labeled Staphylococcus aureus for research studies of THP-1 derived macrophage phagocytic behavior

A simple biological strategy to couple intracellular irrelated biochemical reactions of staphylococcus aureus CMCC 26003 (S. aureus) with inorganic metal ions to synthesize cadmium selenide quantum dots (CdSe QDs) was demonstrated. Correspondingly, S. aureus as living matrices are internally generated and labeled with fluorescent QDs by the smart strategy. Several key factors in the process of biosynthesis were systematically evaluated. At the same time, ultraviolet-visible (UV-Vis), photo-luminescence (PL), inverted fluorescence microscopy and transmission electron microscopy (TEM) were utilized to study the characters of the as produced CdSe QDs. In addition, cytotoxicity and photostability of the QDs containing bacteria were also tested and evaluated as a whole. The results showed that intracellular CdSe nanocrystals had successfully formed in S. aureus living cells, which were less toxic, highly fluorescent and photostable. These fluorescent S. aureus bacteria were next applied as invading pathogens as well as fluorescent bioprobes for exploring the phagocytic behavior of THP-1-derived macrophage. Results proved that internal CdSe QDs labeling had no significantly adverse effects compared with the kind of infection reference, fluorescein isothiocyanate (FITC) stained S. aureus pathogen. Assuredly, the methods presented here provide researchers with a useful option to analyze the behavior of S. aureus as a type of infectious pathogen, which would also help understand the complex interplay between host cells and the invading bacteria on molecular level.

Antimicrobial Activity and Mechanism of Functionalized Quantum Dots

An essential characteristic of quantum dots (QDs) is their antimicrobial activity. Compared with conventional antibiotics, QDs not only possess photoluminescence properties for imaging and photodynamic therapy but also have high structural stability. To enhance their antimicrobial efficiency, QDs usually are functionalized by polymers, including poly(ethylene glycol), polyethyleneimine, and poly-l-lysine. Also, QDs conjugated with polymers, such as poly(vinylpyrrolidone) and polyvinylidene fluoride, are prepared as antimicrobial membranes. The main antimicrobial mechanisms of QDs are associated with inducing free radicals, disrupting cell walls/membranes, and arresting gene expression. The different mechanisms from traditional antibiotics allow QDs to play antimicrobial roles in multi-drug-resistant bacteria and fungi. Since the toxicity of the QDs on animal cells is relatively low, they have broad application in antimicrobial research as an effective alternative of traditional antibiotics.

Green and Simple Synthesis of Silver Nanoparticles by Aqueous Extract of Perovskia abrotanoides: Characterization, Optimization and Antimicrobial Activity

BACKGROUND

Herein, we report the biosynthesis procedure to prepare silver nanoparticles as reduction and capping agents with the aqueous plant extract of Perovskia abrotanoides.

METHODS

The therapeutic application of silver nanoparticles entirely depends on the size and shape of the nanoparticles therefore, their control during the synthesis procedure is so important. The effects of synthesis factors, for example, silver ion concentration, the mass of plant extract, reaction time and extraction temperature, on the size of silver particles were considered and optimized. Several analytical methods were used for the characterization of silver NPs including FT-IR and UV-Vis spectrophotometer, XRD and SEM.

RESULTS

The results showed that the mean size of the silver particles was about 51 nm. Moreover, the antibacterial properties of biosynthesized silver NPs were investigated by the minimum inhibitory concentration, minimum bactericidal concentration, and Well-diffusion tests. The minimum inhibitory concentration/ minimum bactericidal concentration values of silver NPs and aqueous plant extract versus Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) and Gram-negative bacteria (E. coli) were 3.03/0.00, 1.20/0.01, 3.06/0.00, 0.98/1.04, 1.00/0.05 and 1.30/0.03 (mg/mL), respectively.

CONCLUSION

The antimicrobial activity study displayed that the synthesized silver nanoparticles by plant extract have better antimicrobial properties compared to aqueous plant extract of Perovskia abrotanoides.

Ultrasonic and microwave assisted extraction as rapid and efficient techniques for plant mediated synthesis of quantum dots: green synthesis, characterization of zinc telluride and comparison study of some biological activities

In this study, a simple, rapid, and efficient plant-mediated green approach was presented for the synthesis of stable and ultra-small zinc telluride quantum dots (ZnTe QDs) using the aqueous extract of the Ficus johannis plant.