scholarly journals Arsenate reductase from Thermus thermophilus conjugated to polyethylene glycol-stabilized gold nanospheres allow trace sensing and speciation of arsenic ions

2016 ◽  
Vol 13 (123) ◽  
pp. 20160629 ◽  
Author(s):  
Jane Politi ◽  
Jolanda Spadavecchia ◽  
Gabriella Fiorentino ◽  
Immacolata Antonucci ◽  
Luca De Stefano
Keyword(s):  
Gold Nanoparticles ◽  
Polyethylene Glycol ◽  
Environmental Problem ◽  
Thermus Thermophilus ◽  
Arsenate Reductase ◽  
Gold Nanospheres ◽  
Enzyme Adsorption ◽  
Ph Values ◽  
Vis Spectroscopy ◽  
The World

Water sources pollution by arsenic ions is a serious environmental problem all around the world. Arsenate reductase enzyme ( TtArsC ) from Thermus thermophilus extremophile bacterium, naturally binds arsenic ions, As(V) and As (III), in aqueous solutions. In this research, TtArsC enzyme adsorption onto hybrid polyethylene glycol-stabilized gold nanoparticles (AuNPs) was studied at different pH values as an innovative nanobiosystem for metal concentration monitoring. Characterizations were performed by UV/Vis and circular dichroism spectroscopies, TEM images and in terms of surface charge changes. The molecular interaction between arsenic ions and the TtArsC -AuNPs nanobiosystem was also monitored at all pH values considered by UV/Vis spectroscopy. Tests performed revealed high sensitivities and limits of detection equal to 10 ± 3 M −12 and 7.7 ± 0.3 M −12 for As(III) and As(V), respectively.

Seed-mediated synthesis and PEG coating of gold nanoparticles for controlling morphology and sizes

MRS Advances ◽  
2020 ◽  
Vol 5 (63) ◽  
pp. 3353-3360
Author(s):  
Susana Helena Arellano Ramírez ◽  
Perla García Casillas ◽  
Christian Chapa González
Keyword(s):  
Gold Nanoparticles ◽  
Polyethylene Glycol ◽  
Room Temperature ◽  
Colloidal Stability ◽  
Infrared Spectrometry ◽  
Ammonium Bromide ◽  
Chloroauric Acid ◽  
Vis Spectroscopy ◽  
Seed Mediated ◽  
Peg Coating

AbstractA significant area of research is biomedical applications of nanoparticles which involves efforts to control the physicochemical properties through simple and scalable processes. Gold nanoparticles have received considerable attention due to their unique properties that they exhibit based on their morphology. Gold nanospheres (AuNSs) and nanorods (AuNRs) were prepared with a seed-mediated method followed of polyethylene glycol (PEG)-coating. The seeds were prepared with 0.1 M cetyltrimethyl-ammonium bromide (CTAB), 0.005 M chloroauric acid (HAuCl4), and 0.01 M sodium borohydride (NaBH4) solution. Gold nanoparticles with spherical morphology was achieved by growth by aggregation at room temperature, while to achieve the rod morphology 0.1 M silver nitrate (AgNO3) and 0.1 M ascorbic acid solution were added. The gold nanoparticles obtained by the seed-mediated synthesis have spherical or rod shapes, depending on the experimental conditions, and a uniform particle size. Surface functionalization was developed using polyethylene glycol. Morphology, and size distribution of AuNPs were evaluated by Field Emission Scanning Electron Microscopy. The average size of AuNSs, and AuNRs was 7.85nm and 7.96 x 31.47nm respectively. Fourier transform infrared spectrometry was performed to corroborate the presence of PEG in the AuNPs surface. Additionally, suspensions of AuNSs and AuNRs were evaluated by UV-Vis spectroscopy. Gold nanoparticles were stored for several days at room temperature and it was observed that the colloidal stability increased once gold nanoparticles were coated with PEG due to the shield formed in the surface of the NPs and the increase in size which were 9.65±1.90 nm of diameter for AuNSs and for AuNRs were 29.03±5.88 and 8.39±1.02 nm for length and transverse axis, respectively.

scholarly journals Reducing Efficiency of Fucoxanthin in Diatom Mediated Biofabrication of Gold Nanoparticles

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4094
Author(s):  
Piya Roychoudhury ◽  
Przemysław Dąbek ◽  
Michał Gloc ◽  
Aleksandra Golubeva ◽  
Renata Dobrucka ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Gold Nanoparticles ◽  
Room Temperature ◽  
Positive Signal ◽  
Gold Nanospheres ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Sem Study ◽  
Strong Positive Signal

In the present investigation, fucoxanthin—one of the major pigments in diatoms—has been extracted from Nanofrustulum shiloi SZCZM1342, and its reducing efficiency in the biogenesis of gold nanoparticles (GNPs) was checked. Fucoxanthin extracted from golden-brown cells of N. shiloi was compared to the healthy, growing biomass of N. shiloi and standard fucoxanthin after separate exposure to 25 mg L−1 aqueous hydrogen tetrachloroaurate solutions at room temperature. Isolated and standard fucoxanthin were found to be able to reduce gold ions within 12 h whereas, the whole biomass turned pink in color after 72 h of reaction. The synthesized particles were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV–vis spectroscopy of purple-colored suspensions showed the absorption band at approximately 520–545 nm, indicating a strong positive signal for GNP synthesis. The SEM study revealed the deposition of GNPs on siliceous frustules of metal-treated diatom cells. The TEM analysis confirmed the GNPs synthesized by whole biomass are triangular, spherical and hexagonal in nature, whereas the particles produced by extracted and standard fucoxanthin are all spherical in nature. This study demonstrates the involvement of fucoxanthin in the reduction of gold ions and subsequent production of gold nanospheres.

Optimization of Gold Nanoparticles Synthesis using Design of Experiments Technique

2017 ◽  
Vol 68 (7) ◽  
pp. 1518-1423
Author(s):  
Adina Turcu Stiolica ◽  
Mariana Popescu ◽  
Maria Viorica Bubulica ◽  
Carmen Nicoleta Oancea ◽  
Claudiu Nicolicescu ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Zeta Potential ◽  
Design Of Experiments ◽  
Process Model ◽  
Sodium Citrate ◽  
Drug Carriers ◽  
Chloroauric Acid ◽  
Gold Colloids ◽  
Citrate Concentration ◽  
Vis Spectroscopy

Gold nanoparticles are considered the newest drug carriers for different diseases. Therefore it is appropriate continuous optimization of their preparation. In this study, gold colloids with an average size of 1 - 26 nm were obtained by the reduction of tetrachloroauric acid with trisodium citrate. The nanomaterials were characterized by UV-Vis spectroscopy and dynamic light scattering technique. In addition, zeta potential was measured for samples synthesized in order to determine the stability of the colloids. A Two-level Full Factorial design was chosen to determine the optimum set of process parameters (chloroauric acid concentration and sodium citrate concentration) and their effect on various gold nanoparticles characteristics (size and zeta potential). These effects were quantified using Design of Experiments (DoE) with 5 runs and 1 centerpoint. The selected objective and process model in this investigation are screening and interaction. Findings from this research show that to obtain particles larger than 35 nm, it is recommended to increase sodium citrate concentration, at low chloroauric acid values. These conditions will help to achieve smaller zeta potential, too.

Is the Acidic pH of the External Auditory Canal Playing a Significant Role in the Treatment of Acute Otitis Externa?

2018 ◽  
Vol 69 (8) ◽  
pp. 2304-2305
Author(s):  
Oana Ruxandra Iana ◽  
Dragos Cristian Stefanescu ◽  
Viorel Zainea ◽  
Razvan Hainarosie
Keyword(s):  
External Auditory Canal ◽  
Otitis Externa ◽  
Proton Pumps ◽  
Acidic Ph ◽  
External Ear ◽  
Ph Values ◽  
The World ◽  
Subcutaneous Tissues ◽  
Low Levels ◽  
Value Changes

Variable pH values for skin have been reported in the literature, all within the acidic range, varying from 4.0 up to 7. 0. The origin of the acidic pH remains conjectural, and several factors have been incriminated with this role, such as eccrine and sebaceous secretions as well as proton pumps. Keeping low levels of pH prevents microbial dispersal as well as multiplication. The skin in the external auditory canal is also covered with this acidic mantle with antimicrobial value. Changes of pH in the external ear can lead to acute otitis externa. This condition is defined by the inflammation and infection of the cutaneous and subcutaneous tissues of the external auditory canal. 10% of the world�s population may suffer from acute otitis externa at least once in their lifetime. This paper aims to consolidate the relevance of an acidic pH in the healthy external ear and its relation to the pathogenesis and treatment of otitis externa through a prospective and interventional clinical study on 80 patients who presented to the outpatient department at Prof. Dr D. Hociota ENT Institute in Buch

An Effort to Making a Colorimitric Nano-Biosensor for Vibrio cholera Detection

2020 ◽  
Vol 16 (5) ◽  
pp. 793-804
Author(s):  
Naimeh Mahheidari ◽  
Jamal Rashidiani ◽  
Hamid Kooshki ◽  
Khadijeh Eskandari
Keyword(s):  
Gold Nanoparticles ◽  
Colorimetric Assay ◽  
Au Nanoparticle ◽  
Bacteria Detection ◽  
Great Promise ◽  
Bacterial Cells ◽  
Vibrio Cholera ◽  
Minimum Concentration ◽  
Vis Spectroscopy ◽  
Fast Procedure

Background: Today, nanoparticles hold great promise in biomedical researches and applications including bacteria detection. The rapid and sensitive outcomes of bacteria detection strategies using nanoparticle conjugates become determinative, especially in bacterial outbreaks. In the current research, we focused on detecting V. cholera bacteria and its toxin using a thiocyanate/Au nanoparticle. Thiocyanate adsorbed strongly on the surface of gold nanoparticles and changed the surface by enhancing surface plasmon resonance of gold nanoparticles. Objective: This method is tried to introduce a simple and fast procedure to assay vibrio cholera. So, it is observed by the naked eyes as well. Methods: We used two antibodies (Ab) for V. cholera detection: a) a primary antibody conjugated to magnetic nanoparticles (MNPs) for trapping V. cholera bacterial cells, and b) a secondary Abconjugated thiocyanate-GNPs as a colorimetric detector. Then, an immuno-magnetic separation system connected to a colorimetric assay was designed based on the GNPs. The results were measured by ultraviolet-visible (UV-Vis) spectroscopy. Results: The results showed that gold nanoparticles are an appropriate optical assay for detecting biological samples in a minimum concentration and also it can be easily seen by the naked eyes. The linear range of this biosensor is 3.2×104 to 28×104 cells per ml. Conclusion: In this research, a colorimetric immune assay based on gold nanoparticles was designed to improve the sensitivity of V. cholera detection. Also, this method can be used for the detection of other biological agents.

scholarly journals Protected Gold Nanoparticles with Thioethers and Amines As Surrogate Ligands

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
M. Rafiq H. Siddiqui
Keyword(s):  
Gold Nanoparticles ◽  
Variable Temperature ◽  
Size Control ◽  
Analytical Techniques ◽  
High Resolution Electron Microscopy ◽  
Phase Method ◽  
Two Phase ◽  
H Nmr ◽  
Resolution Electron ◽  
Vis Spectroscopy

Dodecyl sulfide, dodecyl amine, and hexylamine were shown to act as surrogate ligands (L) via metastable gold nanoparticles. By collating analytical and spectroscopic data obtained simultaneously, empirical formula Au24L was assigned. These impurity-free nanoparticles obtained in near quantitative yields showing exceptional gold assays (up to 98%Au) were prepared by a modification of the two-phase method. Replacement reactions on the Au24L showed that Au:L ratios may be increased (up to Au55:L (L= (H25C12)2S)) or decreased (Au12:L (L= H2NC12H25and H2NC6H13)) as desired. This work encompassing the role of analytical techniques used, that is, elemental analysis, variable temperature1H NMR, FAB mass spectrometry, UV-Vis spectroscopy, thin film X-ray diffraction, and high-resolution electron microscopy (HREM) has implications in the study of size control, purity, stability, and metal assays of gold nanoparticles.

scholarly journals Buffer Additives and Packaging Differentially Influence the Stability of Dyes Commonly Used in Chromovitrectomy

2016 ◽  
Vol 1 (3) ◽  
pp. 1-10
Author(s):  
Begoña Parrado Aliod ◽  
Wilfried Kugler ◽  
Tim Häring
Keyword(s):  
Polyethylene Glycol ◽  
Chemical Stability ◽  
Deuterium Oxide ◽  
Oxidative Degradation ◽  
Bromophenol Blue ◽  
Physiological Range ◽  
Vis Spectroscopy ◽  
The Stability ◽  
Acid Violet ◽  
Dye Solutions

Purpose: This study was performed to investigate the chemical stability of different dyes used in chromovitrectomy and the influence of various product parameters on it. Methods: Buffered dye solutions were prepared containing 1.5 g/L acid violet 17, 0.25 g/L brilliant blue G, 1.3 g/L bromophenol blue, and 1.5 g/L trypan blue, combined with deuterium oxide, polyethylene glycol 3350, and D-mannitol as additives. For accelerated storage testing, samples were incubated for 400 h at 80°C corresponding to 2 years according to the Van ‘t Hoff equation. After different incubation times samples were taken for UV/Vis spectroscopy, pH measurement, and osmometry. Results: Depending on dye, additive, and packaging, different solutions exhibit differences in chemical stability and hence shelf life. Packaging in syringes instead of vials increases dye stability. Additives may negatively influence important parameters, e.g. polyethylene glycol 3350 increases osmolality beyond the physiological range. Notably, acid violet 17 is chemically unstable except in D-mannitol-containing buffer, packed in syringes. However, simultaneously, D-mannitol leads to a pH shift below 7.0. Conclusion: In summary, dye solutions filled in syringes should be preferred to vials to slow down oxidative degradation. Especially acid violet 17 solutions should be used with caution because the addition of D-mannitol may contribute to pH values beyond the physiological range.

scholarly journals Effects of Different Surfactant Charges on the Formation of Gold Nanoparticles by the LASiS Method

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2937
Author(s):  
Muhammad Zulfajri ◽  
Wei-Jie Huang ◽  
Genin-Gary Huang ◽  
Hui-Fen Chen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gold Nanoparticles ◽  
Laser System ◽  
Synthesis Process ◽  
Au Nps ◽  
Laser Fluences ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
532 Nm

The laser ablation synthesis in solution (LASiS) method has been widely utilized due to its significant prospects in laser microprocessing of nanomaterials. In this study, the LASiS method with the addition of different surfactant charges (cationic CTAB, nonionic TX-100, and anionic SDS) was used to produce Au NPs. An Nd:YAG laser system at 532 nm excitation with some synthetic parameters, including different laser fluences, ablation times, and surfactant concentrations was performed. The obtained Au NPs were characterized by UV-Vis spectroscopy, transmission electron microscopy, and zeta potential analyzer. The Au NPs exhibited the maximum absorption peak at around 520 nm for all samples. The color of Au NPs was changed from red to reddish by increasing the laser fluence. The surfactant charges also played different roles in the Au NPs’ growth during the synthesis process. The average sizes of Au NPs were found to be 8.5 nm, 5.5 nm, and 15.5 nm with the medium containing CTAB, TX-100, and SDS, respectively. Besides, the different surfactant charges induced different performances to protect Au NPs from agglomeration. Overall, the SDS and CTAB surfactants exhibited higher stability of the Au NPs compared to the Au NPs with TX-100 surfactant.

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