On the Synergism of Biogenic Gold Nanoparticles and Hydroxyaluminum Phthalocyanines in the Photoeradication of Staphylococcus aureus

Due to the unusual properties of gold nanoparticles, these structures are widely used in medicine and biology. This paper describes for the first time the synthesis of colloidal gold nanoparticles by the cell-free filtrate obtained from the Coriolus versicolor biomass and the use of these biogenic nanostructures to increase the photosensitizing efficiency of di- (AlPcS2) and tetrasulfonated (AlPcS4) hydroxyaluminum phthalocyanines in antibacterial photodynamic therapy. The obtained monodisperse particles were extremely stable, and this remarkable stability was due to the presence of phosphoprotein as a capping agent. The studied gold nanoparticles had a spherical shape, were uniformly distributed, and were characterized by a single plasmon band at wavelength of 514–517 nm. Almost 60% of the gold particles were found to be in the range of 13 to 15 nm. In accordance with the regulations of the American Microbiological Society, indicating that any antimicrobial technique must kill at least 3 log CFU (99.9%) to be accepted as “antimicrobial”, this mortality of Staphylococcus aureus was shown to be achieved in the presence of AlPcS4 + AuNPs mixture and 4.8 J cm−2 light dose compared to AlPcS4 alone, which required a light dose of 24 J cm−2. The best effect of increasing the effectiveness of combating this pathogen was observed in the case of AlPcS2 + AuNPs as a photosensitizing mixture. The light dose of 24 J cm−2 caused a lethal effect of the studied coccus in the planktonic culture.

Lysozyme–AuNPs Interactions: Determination of Binding Free Energy

Investigation and optimization of lysozyme (Lys) adsorption onto gold nanoparticles, AuNPs, were carried out. The purpose of this study is to determine the magnitude of the AuNPs–lysozyme interaction in aqueous media by simple spectrophotometric means, and to obtain the free energy of binding of the system for the first time. In order to explore the possibilities of gold nanoparticles for sensing lysozyme in aqueous media, the stability of the samples and the influence of the gold and nanoparticle concentrations in the detection limit were studied. ζ potential measurements and the shift of the surface plasmon band showed a state of saturation with an average number of 55 Lys per gold nanoparticle. Lysozyme–AuNPs interactions induce aggregation of citrate-stabilized AuNPs at low concentrations by neutering the negative charges of citrate anions; from those aggregation data, the magnitude of the interactions has been measured by using Benesi–Hildebrand plots. However, at higher protein concentrations aggregation has been found to decrease. Although the nanocluster morphology remains unchanged in the presence of Lys, slight conformational changes of the protein occur. The influence of the size of the nanoclusters was also investigated for 5, 10, and 20 nm AuNPs, and 10 nm AuNPs was found the most appropriate.

Synthesis of gold nanorods and their performance in the field of cancer cell imaging and photothermal therapy

Cancer is one of the most common incident in the world, with malignant tumors having a death rate of up to 19%. A new method of treating cancer cells effectively with minimal cytotoxicity is needed. In the field of biomedicine with unique shape-dependent optical properties, gold nanorods (GNRs) have attracted worldwide interest. These nanorods have two distinct plasmon bands. One is transverse plasmon band in the area of visible light, and the other is longitudinal band of plasmons in near infrared region. These specific characters provide promise for the design of new optically active reagents that simultaneously perform light-mediated imaging and photothermal cancer treatment. We begin our review by summarizing the latest developments in gold nanorods synthesis with a focus on seed-mediated growth method. Nanorods spontaneous self-assembly, polymer-based alignment and its applications as a novel agent for simultaneous bioimaging and photothermal cancer therapy are listed in particular.

Phenothiazinium Photosensitizers Associated with Silver Nanoparticles in Enhancement of Antimicrobial Photodynamic Therapy

Antimicrobial photodynamic therapy (APDT) and silver nanoparticles (AgNPs) are known as promising alternatives for the control of microorganisms. This study aims to evaluate the antifungal activity of APDT, particularly by using the association of low concentrations of phenothiazinium photosensitizers (PS) methylene blue (MB), new methylene blue N (NMBN), and new methylene blue N Zinc (NMBN-Zn) in association with biosynthesized AgNPs. The AgNPs were characterized by UV-Vis spectrophotometry, transmission electron microscopy, and the dynamic light scattering method. The minimum inhibitory concentration of compounds in APDT against Candida albicans and Fusarium keratoplasticum was obtained and the Fractional Inhibitory Concentration Index determined the antifungal effect. The toxicity of compounds and associations in APDT were evaluated in Galleria mellonella. The AgNPs presented a surface plasmon band peak at 420 nm, hydrodynamic diameter of 86.72 nm, and zeta potential of −28.6 mV. AgNPs-PS showed a wider and displaced plasmon band peak due to PS ligands on the surface and decreased zeta potential. AgNPs-NMBN and AgNPs-NMBN-Zn associations presented synergistic effect in APDT with 15 J cm−2 against both fungi and did not show toxicity to G. mellonella. Hence, the enhancement of antifungal activity with low concentrations of compounds and absence of toxicity makes APDT with AgNPs-PS a promising therapeutic alternative for fungal infections.

Numerical Modelling of the Optical Properties of Plasmonic and Latex Nanoparticles to Improve the Detection Limit of Immuno-Turbidimetric Assays

Turbidimetric assays with latex nanoparticles are widely applied for the detection of biological analytes, because of their rapidity, low cost, reproducibility, and automatization. However, the detection limit can be lowered only at the price of a reduced dynamic range, due to the rapid saturation of the light scattering signal at high analyte concentration. Here, we use numerical calculations to investigate the possibility of increasing the performance of immuno-turbidimetric assays without compromising the measurement dynamic range, by combining plasmonic (gold, silver) and latex nanoparticles. Our modelling results show that plasmonic nanoparticles are compatible with a large signal change even when small aggregates are formed, i.e., at low analyte concentration. The working principle relies on the remarkable modification of the surface plasmon band when noble metal nanoparticles form oligomers, and also when latex particles are included in the aggregate. At high analyte concentration, when larger aggregates form, the latex particles can provide the required linear response of standard immuno-turbidimetric assays. Thus, the combination of the two components can be a successful strategy to improve the detection limit and the dynamic range, while maintaining all the advantages of the homogeneous immuno-turbidimetric assays.

Study of the Stability of Citrate Capped AgNPs in Several Environmental Water Matrices by Asymmetrical Flow Field Flow Fractionation

Asymmetrical flow field-flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, was tested for stability studies of dispersions of citrate-capped silver nanoparticles (AgNPs) in several water matrices. The main goal is to provide knowledge to understand their possible behavior in the environment for short times since mixturing (up to 180 min). Ultrapure (UPW), bottled (BW1, BW2), tap (TW), transitional (TrW) and sea water (SW) matrices were assayed. Observations were compatible with the aggregation of AgNPs, a change in the plasmon band and a size growth with time were done. Fractograms showed different evolution fingerprints in the function of the waters and batches. The aggregation rate order was BW2, SW, TrW, BW1 and TW, being BW2 the lowest and TW the highest. NP aggregation can be induced by increasing the salt concentration of the medium, however transitional and sea waters did not follow the rule. Both matrices presented a lower aggregation rate in comparison with other aqueous matrices with much lower ionic strength (BW1 and TW), which can be explained by the potential presence of dissolved organic matter and/or the high concentration of halides providing their stabilization and passivation, respectively. AF4 provides relevant information with respect to static DLS and UV-Vis Spectroscopy showing that at least two populations of aggregates with different sizes between them, depending on both, the mixture time for a given matrix and type of water matrix for the same time.

Silver nanoparticles from insect wing extract: Biosynthesis and evaluation for antioxidant and antimicrobial potential

Silver nanoparticles (AgNPs) are among the most widely synthesized and used nanoparticles (NPs). AgNPs have been traditionally synthesized from plant extracts, cobwebs, microorganisms, etc. However, their synthesis from wing extracts of common insect; Mang mao which is abundantly available in most of the Asian countries has not been explored yet. We report the synthesis of AgNPs from M. mao wings extract and its antioxidant and antimicrobial activity. The synthesized AgNPs were spherical, 40–60 nm in size and revealed strong absorption plasmon band around at 430 nm. Highly crystalline nature of these particles as determined by Energy-dispersive X-ray analysis and X-ray diffraction further confirmed the presence of AgNPs. Hydrodynamic size and zeta potential of AgNPs were observed to be 43.9 nm and -7.12 mV, respectively. Fourier-transform infrared spectroscopy analysis revealed the presence of characteristic amide proteins and aromatic functional groups. Thin-layer chromatography (TLC) and Gas chromatography-mass spectroscopy (GC-MS) analysis revealed the presence of fatty acids in the wings extract that may be responsible for biosynthesis and stabilization of AgNPs. Further, SDS-PAGE of the insect wing extract protein showed the molecular weight of 49 kDa. M. mao silver nanoparticles (MMAgNPs) exhibit strong antioxidant, broad-range antibacterial and antifungal activities, (66.8 to 87.0%), broad-range antibacterial and antifungal activities was found with maximum zone of inhibition against Staphylococcus aureus MTCC 96 (35±0.4 mm) and Fusarium oxysporum f. sp. ricini (86.6±0.4) which signifies their biomedical and agricultural potential.

Antibacterial Properties of Silver Nanoparticles Synthesized Using Piper betle L. Leaf Extract

The green synthesis of silver nanoparticles (AgNPs) using herbal plants has gained much attention due to their potential widespread applications, especially in biomedical application to control pathogenic microbes. The aim of our study was to evaluate the antibacterial properties of synthesized AgNPs using aqueous leaf extract of Piper betle L., an important medicinal plant. The AgNPs were identified by UV-Visible spectrometry (UV-Vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FT-IR). The presence of surface plasmon band around 420-460 nm indicated AgNPs formation. Spherical nature, unique size-distribution and crystal structure of the AgNPs with diameter around 10-20 nm were affirmed by TEM and XRD analyses. The FTIR measurements showed the presence of bioactive compounds in the extract responsible for the efficient reduction of silver ions and stabilization of the AgNPs. The results from the antimicrobial assays suggested that the biosynthesized AgNPs were potent against pathogenic bacteria including Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

Hybrid Layers of Donor-Acceptor Copolymers with Homogenous Silver Nanoparticle Coverage for Photonic Applications

Hybrid layers of donor-acceptor (D-A) copolymers containing N,N′-dialkylperylene-3,4,9,10-tetracarboxydiimide electron-acceptor units covered with silver nanoparticles (Ag-NPs) were prepared by electrochemical doping of pristine layers during reduction processes. In situ optical absorption spectra of the layers were recorded during the formation of Ag-NP coverage. The hybrid layers were characterized by absorption spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX). In the absorption spectra of the hybrid layers, a surface plasmon band characteristic of Ag-NPs appeared. Significant improvements in light absorption due to the plasmonic effects of Ag NPs were observed. Stable Ag-NPs with an average diameter of 41–63 nm were formed on the surface, as proven by SEM and XPS. The Ag-NP coverage and size depended on the hybrid layer preparation conditions and on the copolymer composition. The metallic character of the Ag-NPs was proven by XPS. The location in the surface layer was further confirmed by EDX analysis. To the best of our knowledge, this is the first report on such hybrid layers having the potential for a variety of photonic and electronic applications.