Silver Nanoparticles Of Different Sizes Research Articles

Controlled release of Ag+ ions to human cancer cells selectively neutralized with silver nanoparticles of different sizes produced by a green synthesis method

We present a facile green method to synthesize silver nanoparticles (AgNPs) with different sizes and uniform size distributions using an extract of Rhododendron mucronulatum flowers. Here, AgNPs were utilized to modify the release of Ag+ ions and selectively annihilate human cancer cells. AgNPs were prepared at ambient temperature (RT-AgNPs) and in higher-temperature water baths at 60 °C (W60-AgNPs) and 70 °C (W70-AgNPs) to modify the diameter and uniformity of the AgNPs. The W60-AgNPs were further treated with acid to modify their size and surface state (named AW60-AgNPs). The water-bath technique enabled an alteration of the relative rates of initial nucleation and growth of nanoparticles in a homogeneous environment, promoting the creation of small AgNPs with a uniform diameter distribution. The acid treatment eroded the surface particles to reduce their diameter and simultaneously introduced functional groups. The Ag+-ion release efficiency of the prepared nanoparticles and the toxicity of Ag+ ions on cancer cells were examined. Among the prepared samples, the AW60-AgNPs released the greatest amount of Ag+ ions and produced the largest amount of reactive oxygen species (O2̇−, ˙OH, and H2O2). All of the AgNP samples were applied to tumor cells (K562 and HT1080) and healthy cells (LO2) in vitro. In the presence of K562 cells, AW60-AgNPs showed the most efficient dose- and time-dependent early and late apoptosis as well as reduced viability. A crystal violet assay showed that the synthesized particles preferentially attack HT1080 cancer cells rather than LO2 normal cells. We found that Ag+ ions release efficiency and selectivity varied with particle size, and that DNA damage in tumor cells was due to the formation of Ag+-coordinated complexes within DNA base pairs.

Particle Size Modulates Silver Nanoparticle Toxicity during Embryogenesis of Urchins Arbacia lixula and Paracentrotus lividus.

Silver nanoparticles represent a threat to biota and have been shown to cause harm through a number of mechanisms, using a wide range of bioassay endpoints. While nanoparticle concentration has been primarily considered, comparison of studies that have used differently sized nanoparticles indicate that nanoparticle diameter may be an important factor that impacts negative outcomes. In considering this, the aim of the present study was to determine if different sizes of silver nanoparticles (AgNPs; 10, 20, 40, 60 and 100 nm) give rise to similar effects during embryogenesis of Mediterranean sea urchins Arbacia lixula and Paracentrotus lividus, or if nanoparticle size is a parameter that can modulate embryotoxicity and spermiotoxicity in these species. Fertilised embryos were exposed to a range of AgNP concentrations (1−1000 µg L−1) and after 48 h larvae were scored. Embryos exposed to 1 and 10 µg L−1 AgNPs (for all tested sizes) showed no negative effect in both sea urchins. The smaller AgNPs (size 10 and 20 nm) caused a decrease in the percentage of normally developed A. lixula larvae at concentrations ≥50 µg L−1 (EC50: 49 and 75 μg L−1, respectively) and at ≥100 µg L−1 (EC50: 67 and 91 μg L−1, respectively) for P. lividus. AgNPs of 40 nm diameter was less harmful in both species ((EC50: 322 and 486 μg L−1, for P. lividus and A. lixula, respectively)). The largest AgNPs (60 and 100 nm) showed a dose-dependent response, with little effect at lower concentrations, while more than 50% of larvae were developmentally delayed at the highest tested concentrations of 500 and 1000 µg L−1 (EC50(100 nm); 662 and 529 μg L−1, for P. lividus and A. lixula, respectively. While AgNPs showed no effect on the fertilisation success of treated sperm, an increase in offspring developmental defects and arrested development was observed in A. lixula larvae for 10 nm AgNPs at concentrations ≥50 μg L−1, and for 20 and 40 nm AgNPs at concentrations >100 μg L−1. Overall, toxicity was mostly ascribed to more rapid oxidative dissolution of smaller nanoparticles, although, in cases, Ag+ ion concentrations alone could not explain high toxicity, indicating a nanoparticle-size effect.

Near field and far field plasmonic enhancements with bilayers of different dimensions AgNPs@DLC for improved current density in silicon solar

The effect of a bilayer of different dimension silver nanoparticles (Ag NPs) on light trapping in silicon solar cells is investigated. Here, we report on the improved performance of silicon solar cells by integrating two layers of silver nanoparticles of different sizes. We experimentally examine the plasmonic near-field and far-field effects of bilayer Ag NPs embedded within an anti-reflective DLC layer on silicon solar cells' optical and electrical characteristics. Field-Emission Scanning Electron Microscopy drove the two-dimensional differences in the size of Ag NPs. The surface plasmon resonance of the two-dimensional nanoparticles was estimated from the absorption optical spectra. External quantum efficiency measurements showed that near-field or far-field plasmonic effects altered with the Ag NPs size. The development of far fields was confirmed by measuring the solar cell performance under AM 1.5 G illumination. The impact of the far-field in the cell containing two layers of Ag NPs, which outer layer is larger dimensions NPs, improves the current density up to 38.4 mA/cm2 (by 70% compared to the bare reference cell).

Probing the structure sensitivity of dimethyl oxalate partial hydrogenation over Ag nanoparticles: A combined experimental and microkinetic study

Silver nanoparticles of different sizes have been synthesized to study their catalytic performance in dimethyl oxalate (DMO) partial hydrogenation to methyl glycolate (MG). Then, a detailed microkinetic analysis based on the results of DFT calculations has been performed to elucidate the origin of the observed size-dependent kinetics, where tabulated thermodynamic properties of gas-phase species are used to ensure the thermodynamic consistency of the reaction. Calculated results show that the turnover frequency for DMO consumption is much higher on Ag(211) than on Ag(111), suggesting the stepped surface dominates the kinetics. The hydrogenation of DMO on the two surfaces occurs along the same dominant reaction pathway, and the rate-determining step for the partial and deep hydrogenation of DMO is DMO and MG dissociation, respectively. The finding that the MG selectivity increases while the DMO hydrogenation activity decreases with the Ag nanoparticle size reveals the structure sensitivity of DMO partial hydrogenation.

Cytotoxic Potential of Bio-Silica Conjugate with Different Sizes of Silver Nanoparticles for Cancer Cell Death

Well-defined silver nanoparticles were doped into bio-based amorphous silica (Ag-b-SiO2) with different silver contents (from 2 to 20 wt%) by a solvent-free procedure. The four as-synthetized samples were hydrogenated at 300 °C to ensure the formation of zero-valent Ag nanoparticles. The prepared samples were characterized by X-ray powder diffraction (XRD), elemental analysis, N2 sorption measurements, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). The characterization data confirmed the formation of well-defined zero-valent silver nanoparticles in the range of 3–10 nm in the low-loading samples, while in high-loading samples, bulky particles of silver in the range of 200–500 nm were formed. The in vitro cytotoxic activities of the Ag-b-SiO2 samples were tested against the tumor cell lines of breast (MCF-7), liver (HepG2), and colon (HCT 116) over a concentration range of 0.01 to 1000 g. The prepared samples exhibited a wide range of cytotoxic activities against cancer cells. An inverse relationship was observed between the silver nanoparticles’ size and the cytotoxic activity, while a direct relationship between the silver nanoparticles’ size and the apoptotic cell death was noticed.

Evaluation of the Effects of Particle Sizes of Silver Nanoparticles on Various Biological Systems.

Seven biological methods were adopted (three bacterial activities of bioluminescence, enzyme, enzyme biosynthetic, algal growth, seed germination, and root and shoot growth) to compare the toxic effects of two different sizes of silver nanoparticles (AgNPs). AgNPs showed a different sensitivity in each bioassay. Overall, the order of inhibitory effects was roughly observed as follows; bacterial bioluminescence activity ≈ root growth > biosynthetic activity of enzymes ≈ algal growth > seed germination ≈ enzymatic activity > shoot growth. For all bacterial activities (bioluminescence, enzyme, and enzyme biosynthesis), the small AgNPs showed statistically significantly higher toxicity than the large ones (p < 0.0036), while no significant differences were observed among other biological activities. The overall effects on the biological activities (except shoot growth) of the small AgNPs were shown to have about 4.3 times lower EC50 (high toxicity) value than the large AgNPs. These results also indicated that the bacterial bioluminescence activity appeared to be an appropriate method among the tested ones in terms of both sensitivity and the discernment of particle sizes of AgNPs.

Facile and Green Route to Silver Nanoparticles Using Aqueous Plant Extract, and their Photocatalytic and Antibacterial Studies

Silver nanoparticles were prepared through an environmental friendly and cost-effective plant-mediated technique, using crude extracts of Welsh onion plant. The synthesized nanoparticles were characterized using UV-vis spectrophotometer, powdered X-ray diffractometer (p-XRD), Fourier transform infra-red (FTIR) spectrophotometer, and transmission electron microscope (TEM). Silver nanoparticles of different sizes and morphologies were obtained by varying some synthesis parameters such as concentrations of AgNO3 (1, 2 and 5 mM) and ratio of the volume of the plant extract to AgNO3 (1:5 and 1:10) at constant reaction temperature of 80 °C. The difference in the reaction conditions showed significant effects on silver nanoparticles obtained. The surface plasmon resonance (SPR) varied with change in concentration of AgNO3 and the ratio of the AgNO3 to the plant extracts. The lowest SPR appeared around 412 nm (2 mM; 1:10), while the largest was achieved around 427 nm (5 mM; 1:10). FTIR results revealed the presence of different characteristic functional groups responsible for the bioreduction of silver ions in Welsh onion extract. Transmission electron microscopy (TEM) showed that the lowest average particle size of the silver nanoparticles was 3.74 nm (2 mM; 1:10), while the highest was 15.72 nm (1 mM; 1:5). Monodispersed spherical shaped nanoparticles were obtained from the 2 mM concentration of the AgNO3, while particles with some degree of agglomeration were obtained from 1 and 5 mM concentration. The p-XRD studies revealed face centred cubic structures. The nanoparticles obtained from 1 and 5 mM (1:5) gave moderate photo-catalytic potentials in the degradation of methyl red dye. However, the photocatalytic property increased with increase in the concentration of the precursor salt (AgNO3) from 1 to 5 mM. Gram positive Staphylococcus aureus and Bacillus cereus and Gram negative Klebsiela pneumonia and Escherichia coli bacteria strains were susceptible to the silver nanoparticles (2 mM). The nanoparticles were most active against E. coli with a minimum inhibitory concentration (MIC) below 0.05 mg/mL. The silver nanoparticles could become potential compounds in the future antibiotic research.

Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites

AbstractNanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC–NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self‐assembly strategy is described for fabrication of complex and well‐defined BC–NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self‐assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near‐field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.

Silver nanoparticle Bacteriostatic activity Assessment against Extended-Spectrum Beta-Lactamase Producing Uropathogenic Klebsiella pneumonia

The aims: Screen for the Extended-Spectrum Beta-Lactamase producing Klebsiella pneumonia from urinary tract infection UTI patients phenotypically and molecularly, also testing different sizes of silver nanoparticles as antibacterial for the resistance isolates. Methodology: Vitek Extended-Spectrum Beta-Lactamase test , molecular confirmed ESBL-producing isolates were checked by PCR for the presence of AmpC and blaCTX-M genes. Flat well microtiter plates were used for packing of antibacterial activity of silver nanoparticles . This study included 85 urine samples were collected from patients that admitted to the "Rizgary Hospital" in Erbil province from 15 June to 15 December 2018. Antibiotic sensitivity test of all isolates to (Ampicillin, Ampicillin/sulbactam Cefazolin, Ceftazidime Ceftriaxone, Cefepime, Imipenem, Nafcillin and Nitrofurantoin )antibiotics were tested by the disc-agar method as standardized by the National Committee for Clinical laboratory Standards (2006).Results: Out of 51 tested isolates of Klebsiella pneumonia, 11 (21.6%) were Extended-Spectrum Beta-Lactamase Producers. Their antibiotic resistance profile showed the rate of resistance isolates was (100%) to Ampicillin, Cefazolin, Ceftazidime and Ceftriaxone and ( 90%) to Cefepime .In addition the susceptibility to Imipenem was (72.7%) of isolates. The bands of the AmpC and bla CTX-M genes was noted in (42.9%) samples and the remain samples (57.1 %)were negative for both genes. The Minimum Inhibitory Concentration during incubation of Non ESBL producer - ESBL producer isolates in series concentrations of silver nanoparticles size (20 nm) was between (625 -2500) µg/ml and for size (90 nm), it was (1250) µg/ml for non ESBL producer and not affected ESBL producer isolates .The increased percentage rates of β-lactamase producing Klebsiella species were seen which was considered as an alarm, due to limitation in treatment options for UTI. It was appeared that Imipenem currently is the main available antibiotic for UTI treatment as a drug of choice. It was noticed that different sizes of silver nanoparticles showed antibacterial activity for ESBL producing isolates.

Bactericidal Effect of Cotton Fabric Treated with Polymer Solution Containing Silver Nanoparticles of Different Sizes and Shapes

Stable silver nanoparticles in solutions of sodium-carboxymethylcellulose (Na-CMC) were synthesized and their structure and physico-chemical properties were evaluated. The form and sizes of silver nanoparticles formed in solutions of CMC and cotton fabrics were studied using UV-VIS spectroscopy, atomic force microscopy and transmission electron microscopy methods. It was found that silver nitrate concentration increase in sodium carboxymethylcellulose solutions, as well as photoirradiation of the hydrogel lead to the changes of the silver nanoparticles size and shape. Investigations have also shown that spherical silver nanoparticles with sizes of 5-35 nm and content of 0.0086 mass% in cotton fabrics possess high bactericidal activity. Stabilization of silver nanoparticles has preserved bactericidal and bacteriostatic activities during the washing of cotton fabrics and textiles on their base.

Antibacterial effect of cotton fabric treated with silver nanoparticles of different sizes and shapes

Stable silver Nanoparticles in solutions of sodium-carboxymethylcellulose (Na-CMC) were synthesized, and their structure and physico-chemical properties were studied. The form and sizes of silver nanoparticles formed in solutions of CMC and cotton fabrics were studied using UV-VIS spectroscopy, atomic force microscopy and transmission electron microscopy methods. It was found that the silver nitrate concentration increase in sodium carboxymethylcellulose solutions, as well as photoirradiation of the hydrogel lead to the changes of the silver nanoparticles size and shape. Investigations have shown that spherical silver nanoparticles with sizes of 5-35nm and content of 0.0086 mass% in cotton fabrics possess high bactericidal activity. Stabilization of silver nanoparticles has preserved bactericidal and bacteriostatic activities during the washing of cotton fabrics and textiles on their base.

Differential lethal and sublethal effects in embryonic zebrafish exposed to different sizes of silver nanoparticles

Various parameters can influence the toxic response to silver nanoparticles (Ag NPs), including the size and surface properties, as well as the exposure environment and the biological site of action. Herein, we assess the intestinal toxicity of three different sizes (10, 40, and 100 nm) of Ag NPs in embryonic zebrafish, and describe the relationship between the properties and behavior of Ag NPs in the exposure medium, and induction of lethal and sublethal effects. We find that the composition of the medium and the size contribute to differential NPs agglomeration, release of Ag ions, and subsequent effects during exposure. The exposure medium causes dramatic reduction in silver dissolution due to the presence of salts and divalent cations, which limits the lethal potential of silver ions. Lethality is observed primarily for embryos exposed to medium sized Ag NPs (40 nm), but not to the supernatant originated from particles, which suggests that the exposure to particulate silver is the main cause of mortality. On the other hand, the exposure to 10 nm and 100 nm NPs, as well as Ag ions, only causes sublethal developmental defects in skeletal muscles and intestine, and induces a nitric oxide imbalance.

Modification of Spectral Behavior of Ketocyanine Dyes by Silver Nanoparticles of Different Sizes

The spectral behavior of two ketocyanine dyes 2,5-di[(E)-1-(4-dimethylaminophenyl) methylidine]-1-cyclopentanone(2,5-DMAPMC) and 2,5-di[(E)-1-(4-diethylaminophenyl) methylidine]-1-cyclopentanone (2,5-DEAPMC) is investigated in the presence of silver nanoparticles (AgNPs) of sizes 32[Formula: see text]nm, 52[Formula: see text]nm and 60[Formula: see text]nm using absorption and fluorescence spectroscopy. The absorption spectral changes of dyes with the addition of AgNPs of different sizes suggest their possible interaction with AgNPs. Fluorescence quenching has been observed for both the dyes with the addition of AgNPs of all the sizes. The possible quenching mechanisms including energy transfer and electron transfer are discussed. The fluorescence quenching rate parameter is found to increase with increase in the size of AgNPs and is explained based on the varying ability of silver AgNPs of different sizes to accommodate dye molecules. The effect of functional groups on quenching rate parameters is also discussed.

Fabrication of silver nanoparticles-embedded antibacterial polymer surface through thermal annealing and soft molding technique

The major challenge faced in biomedical field is the formation of biofilm on polymer devices like catheters. It is important to functionalize the biomedical devices with a bactericidal agent through an easy and safe process in order to protect them from bacterial attack. In this article, the new method of impregnation of silver nanoparticles (AgNPs) into polymer film was proposed and tested against bacterial cells. The different sizes of silver nanoparticles were embedded in polystyrene film using thermal annealing and soft molding technique. Silver films having different thickness were deposited on the highly polished machinable glass ceramic (MACOR) substrate using direct current (DC) sputtering and subjected to at 750 °C for 15 min. After the heat treatment, AgNPs were formed on MACOR sample. It was then characterized using field emission scanning electron microscope (FE-SEM). Image-J software was used to analysed shape, size and distribution of AgNPs. The spin coating method was adopted to coat polystyrene film on to MACOR substrate supported AgNPs and allow it to cure for 24 h. After curing, the polystyrene film was peeled off and finally, AgNPs got transferred to polystyrene film. The AgNPs embedded polystyrene film was analyzed using FE-SEM and atomic force microscopy (AFM). Spread plate (plate counting) method was used to evaluate the bacterial killing potential of modified polystyrene film against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The modified polystyrene film shows effective antibacterial ability against both the types of bacteria compared to the plain polystyrene surface.

Anticancer Activity of Green Silver Nanoparticles against He-La Cervical Cancer Cell Lines

Abstract In the present work, green nanotechnology was used to synthesize silver nanoparticles of different sizes to study their anti-cancer activity against He-La cervical. The synthesis method is easy, simple, environment friendly and does not require any sophisticated labs. This method utilizes principles of green chemistry. Silver nanoparticles were synthesized using electrolytic deposition technique with black tea leaf extract as capping agent. The as-synthesized nanoparticles were characterized using XRD, TEM, and UV-Visible and FTIR spectroscopy techniques. Elemental analysis of the X-ray graphs reveals that highly pure silver nanoparticles are synthesized. Activity of the Ag NPs against cell lines was observed in a dose-dependent manner using MTT assay and it was found that as-synthesized silver nanoparticles inhibited the growth of He-La cervical cancer cell lines almost up to 70-75% respectively. The IC50 value of sample against He-La cervical cancer cell lines were obtained at 30-fold dilutions of concentration of 178 ppm

Synthesis of Silver Nanoparticles with the use of Herbaceous Plant Extracts and Effect of Nanoparticles on Bacteria

The screening of aqueous extracts of herbaceous plants that grow on the territory of the Russian Federation with their subsequent use for the biosynthesis of silver nanoparticles (SNPs) in accordance with the principles of green chemistry has been performed. Extracts from the leaves of three plants (Mentha piperita L., Melilotus officinalis, and Archangelica officinalis) promoted efficient synthesis of SNPs, reducing the silver cation from AgNO3. SNP formation was tested on a spectrophotometer. Atomic force microscopy showed that plant extracts cause the formation of SNPs of different sizes—from 10 to 80 nm. Scanning electron microscopy revealed SNPs with various shapes and sizes; they were most commonly spherical. The obtained nanoparticles had a bactericidal effect on Escherichia coli K-12 and Pseudomonas aeruginosa PA01 (the latter being more resistant), and they suppressed the formation of E. coli biofilms. The obtained data show that the use of extracts from three herbaceous plants provides a readily available and ecologically safe method for the production of SNPs with antimicrobial activity.

Use of spectroscopic and zeta potential techniques to study the interaction between lysozyme and curcumin in the presence of silver nanoparticles at different sizes

This article describes, for the first time, the effect of three different sizes of silver nanoparticles on the binding of curcumin to lysozyme as examined by spectroscopic and zeta potential techniques at physiological conditions. The binding constants of curcumin to lysozyme in the presence of silver nanoparticles were measured. Based on the results of synchronous fluorescence and three-dimensional fluorescence spectroscopy, the presence of the different sizes of silver nanoparticles caused conformational changes in lysozyme during the binding of curcumin. Such changes were also observed when increasing the curcumin concentration. The results of fluorescence resonance energy transfer theory indicated that different sizes of silver nanoparticles could change the binding distance between curcumin and lysozyme. Based on the red edge excitation shift approach, we concluded that the limited mobility around the Trp residues decreased in the presence of silver nanoparticles with bigger size. Under resonance light scattering, the aggregation of curcumin on lysozyme in the presence of silver nanoparticles can play a major role in functional proteins.Communicated by Ramaswamy H. Sarma

Size-dependent skin penetration of silver nanoparticles: effect of penetration enhancers

Penetration enhancers are usually surfactants, and co-surfactants added to dermatological applications (creams) to solubilize lipophilic active principles. They have the potential to alter the lipid integrity within the stratum corneum. Transdermal preparations such as antibiotics are now gaining a lot of interest. The present study evaluates the effect of penetration enhancers and different nanoparticle sizes of silver nanoparticles with respect to their impact on nanoparticle-skin penetration, expressed as the flux (J), the Permeability Coefficient (PC) and Enhancement Ratio (ER). In this study, the modified Franz diffusion glass cell method was adapted to measure the primary skin permeability parameters. Drug delivery depends so much on the ability of vehicles to overcome the skin barrier and deliver their content deeply into tissue layers. Hence the need for the present studies which aims to evaluate the quantity of different sizes of silver nanoparticles permeating the skin per unit time in the presence of penetration enhancers. The observed flux for the different sizes was 26, 18, 30, and 4.2 µg/cm2/h, respectively, for 4.0% Tween 80; 28, 22, 34, and 8 µg/cm2/h, respectively, for 20% Propylene Glycol (PG); 18, 14, 24 and 2.8 µg/cm2/h, respectively, for 20.0% Poly Ethylene Glycol (PEG) and 34, 28, 46 and 12 µg/cm2/h, respectively, for 4.0% sodium lauryl sulfate when compared to an aqueous solution of AgNPs (22 NM). Considering the size of AgNPs and choice of penetration enhancers could pave way for developing an ideal dermatological preparation requiring the use of nanoparticles.

One-Shot Dual-Code Immunotargeting for Ultra-Sensitive Tumor Necrosis Factor-α Nanosensors by 3D Enhanced Dark-Field Super-Resolution Microscopy.

Tumor necrosis factor-α (TNF-α) is a significant mediator of autoimmune diseases and an inflammatory protein biomarker. A novel method for the immunotargeting of TNF-α has been developed using three-dimensional (3D) enhanced dark-field super-resolution microscopy (3D EDF-SRM) based on ultrasensitive dual-code plasmonic nanosensing. Dual-code EDF-based 3D SRM improved the localization precision and sensitivity with a least-cubic algorithm, which provides accurate position information for the immunotargeted site. A dual-view device and digital single-lens reflex (DSLR) camera were used for simultaneous dual confirmable quantitative and qualitative immunoscreening based on enhanced dark-field scattering images. Two different sizes of silver nanoparticles (40- and 80-nm AgNPs) were compared to enhance the scattering signal of the immunotargeted plasmonic nanoprobe for the 3D EDF-SRM system. The standard TNF-α was immunotargeted at a single-molecule level and was quantitatively analyzed by measuring the scattering signals of 80 nm AgNPs on an array chip with gold-nanostages (GNSs) with 100 nm spot diameters. The localization precision in the 80 nm AgNP immunotag on the GNS narrowed to ∼9.5 nm after applying the least-cubic algorithm. The developed nanosensor exhibited a detection limit of 65 zM (1.14 ag/mL; S/N = 3) with a wide dynamic detection range of 65 zM-2.08 pM (1.14 ag/mL-36.4 pg/mL; R = 0.9921). These values are 20-33 400 000 times lower than detection limits obtained using previous methods. In addition, a recovery greater than 98% was achieved by spiking standard TNF-α into human serum samples. This method should facilitate simultaneous improvements in immunotargeting precision and ultrahigh sensitive detection of various disease-related target protein molecules at a single-molecule level.

Size-Dependent Inhibitory Effects of Antibiotic Drug Nanocarriers against Pseudomonas aeruginosa.

Multidrug membrane transporters (efflux pumps) are responsible for multidrug resistance (MDR) and the low efficacy of therapeutic drugs. Noble metal nanoparticles (NPs) possess a high surface-area-to-volume ratio and size-dependent plasmonic optical properties, enabling them to serve both as imaging probes to study sized-dependent MDR and as potential drug carriers to circumvent MDR and enhance therapeutic efficacy. To this end, in this study, we synthesized three different sizes of silver nanoparticles (Ag NPs), 2.4 ± 0.7, 13.0 ± 3.1, and 92.6 ± 4.4 nm, functionalized their surface with a monolayer of 11-amino-1-undecanethiol (AUT), and covalently conjugated them with antibiotics (ofloxacin, Oflx) to prepare antibiotic drug nanocarriers with conjugation ratios of 8.6 × 102, 9.4 × 103, and 6.5 × 105 Oflx molecules per NP, respectively. We purified and characterized the nanocarriers and developed cell culture medium in which the cells grew normally and the nanocarriers were stable (non-aggregated), to quantitatively study the size, dose, and efflux pump (MexAB-OprM) dependent inhibitory effect of the nanocarriers against two strains of Pseudomonas aeruginosa, WT (normal expression of MexAB-OprM) and ΔABM (deletion of MexAB-OprM). We found that the inhibitory effect of these nanocarriers highly depended on the sizes of NPs, the doses of antibiotic, and the expression of MexAB-OprM. The same amount of Oflx on the largest nanocarriers (92.6 ± 4.4 nm) showed the highest inhibitory effect (the lowest minimal inhibitory concentration) against P. aeruginosa. Surprisingly, the smallest nanocarriers (2.4 ± 0.7 nm) exhibited a lower inhibitory effect than free Oflx. The results suggest that size-dependent multivalent effects, the distribution and localization of Oflx (pharmacodynamics), and the efflux of Oflx all play a role in the inhibitory effects. Control experiments using three sizes of AgMUNH2 NPs (absence of Oflx) showed that these NPs do not exhibit any significant inhibitory activity toward both strains. These new findings demonstrate the need for and possibility of designing optimal sized antibiotic nanocarriers to achieve the highest efficacy against P. aeruginosa.