Study of Gelation in Aqueous Solutions of Cysteine and Silver Nitrate

Пахомов, П. М.; Ovchinnikov, M. M.; Khizhnyak, S. D.; Lavrienko, M. V.; Nierling, Wolfgang; Lechner, M. D.

doi:10.1023/b:coll.0000015059.50285.e9

Cited by 29 publications

(18 citation statements)

References 3 publications

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“…The disulfide compound GSSG can bind to nAg surfaces with the -S-S- bond cleavage and may therefore have a similar binding strength as glutathione. Methionine, with sulfur bonded to two methyl groups has a log K f of 6.45 and serine with no sulfur has a log K f of 3.7 50. We also found the addition of 5 µM cysteine or GSH to AgClO 4 solution drives free silver ion to very low values, so re-reduction of silver ion back to Ag 0 may be also contribute to the overall apparent release.…”

Section: Resultsmentioning

confidence: 61%

Controlled Release of Biologically Active Silver from Nanosilver Surfaces

Liu¹,

Sonshine²,

Shervani³

et al. 2010

ACS Nano

965

823

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Major pathways in the antibacterial activity and eukaryotic toxicity of nano-silver involve the silver cation and its soluble complexes, which are well established thiol toxicants. Through these pathways, nano-silver behaves in analogy to a drug delivery system, in which the particle contains a concentrated inventory of an active species, the ion, which is transported to and released near biological target sites. Although the importance of silver ion in the biological response to nano-silver is widely recognized, the drug delivery paradigm has not been well developed for this system, and there is significant potential to improve nano-silver technologies through controlled release formulations. This article applies elements of the drug delivery paradigm to nano-silver dissolution and presents a systematic study of chemical concepts for controlled release. After presenting thermodynamic calculations of silver species partitioning in biological media, the rates of oxidative silver dissolution are measured for nanoparticles and macroscopic foils and used to derive unified area-based release kinetics. A variety of competing chemical approaches are demonstrated for controlling the ion release rate over four orders of magnitude. Release can be systematically slowed by thiol and citrate ligand binding, formation of sulfidic coatings, or the scavenging of peroxy-intermediates. Release can be accelerated by pre-oxidation or particle size reduction, while polymer coatings with complexation sites alter the release profile by storing and release inventories of surface-bound silver. Finally, the ability to tune biological activity is demonstrated through bacterial inhibition zone assay carried out on selected formulations of controlled release nano-silver.

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Section: Resultsmentioning

confidence: 61%

Controlled Release of Biologically Active Silver from Nanosilver Surfaces

Liu¹,

Sonshine²,

Shervani³

et al. 2010

ACS Nano

965

823

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“…We obtained hydrogels using a simple methodology by direct mixing of all components. To prepare 1 mL of CSS according to the procedure, 17,25,26,[28][29][30] 0.3 mL of Cys was added to 0.325 mL of water and 0.375 mL of AgNO 3 ; the concentration of both initial components is 1 Â 10 À2 M. The sample was stirred after addition of each component. Aqueous solutions of all the initial components were prepared using bidistilled water.…”

Section: Preparation and Characterization Of Samples Based On L-cystementioning

confidence: 99%

“…At present, only very few amino acid-based systems gelling at low concentrations of gelators are known. [17][18][19][20] It should be mentioned that cysteine-Ag cluster gels obtained by Y. Cui et al 20 are also classified as low concentration hydrogels, but the authors applied a different method of gel synthesis. Moreover, their gel has concentrations of AgNO 3 and Cys 5-7.5 times those of the respective concentrations of our gel.…”

Section: Introductionmentioning

confidence: 99%

“…Using various research methods, 17,[24][25][26][27][28][29][30] we have achieved a considerable advance in understanding self-assembly processes in CSS before and after adding a gel-initiating salt. To understand the role of each functional group in L-cysteine for the formation of spatial gel networks and elucidate the mechanism of gelation in CSS, we study self-assembly processes in L-cysteine and its derivatives which differ from cysteine by functional groups such as SH, NH, NH 2 , CO, C(O)OH and OH (see Table 1).…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of gelation in low-concentration aqueous solutions of silver nitrate with l-cysteine and its derivatives

et al. 2017

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We discuss the results of experimental studies of the processes of gelation in aqueous solutions of silver nitrate with l-cysteine and its derivatives. We focus on understanding what determines if these small molecules will self-assemble in water at their extremely low concentration to form a gel. A mechanism of gel formation in a cysteine-silver solution (CSS) is proposed. The analysis of the results indicates that filamentary aggregates of a gel network are formed via interaction of NH and C(O)O groups that belong to neighboring silver mercaptide (SM) aggregates. In turn, formation of sulphur-silver bonds between silver mercaptide molecules is responsible for self-assembling these molecules into SM aggregates which can be considered as supramonomers. Free polar groups located on the surfaces of the aggregates can form hydrogen bonds with water molecules, which explains the unique ability of CSS hydrogels to trap water at low concentrations of low-molecular-weight hydrogelators.

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“…According to the data of the dynamic light scattering, the average hydrodynamic radius of clusters increases with time. Upon the attainment of a certain size, the clusters interact by the surface groups to form weak donor-acceptor and hydrogen bonds [8].…”

mentioning

confidence: 99%

Rheology of gelating systems

Пахомов

Khiznyak

Ovchinnikov

et al. 2005

J Eng Phys Thermophys

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Two different types of physical gels -thermoreversible gels based on ultrahigh-molecular-weight polyethylene and thixotropic ones based on cysteine and silver nitrate -have been investigated using viscosimetric methods. Structural methods (IR and Raman spectroscopy and dynamic light scattering) have been used in interpretation of the rheological data obtained.Gels, including polymer ones, are widely used in creation of high-strength fibers, supersorbents, and highly filled materials, in immobilization of medicines, etc. Viscosimetric methods are fundamental in identifying and characterizing the gel state of a system. In this connection, the present work seeks to use the viscosimetry method for studying thermoreversible gels based on ultrahigh-molecular-weight polyethylene (UHMWPE) and thixotropic gels based on the aqueous solutions of cysteine silver and nitrate (they differ in the structural character of physical sites). To interpret the rheological data obtained we use such direct structural methods as IR Fourier spectroscopy, low-frequency Raman spectroscopy (LAM technique), and dynamic light scattering.Thermoreversible UHMWPE Gels. Gels represent a space network formed by polymer molecules and filled with solvent. According to De Gennes [1], all polymer gels can be subdivided into physical gels and chemical ones. The presence of the space network imparts the specific properties of a solid body (strength, holding of the shape, and others) to the gel (Fig. 1). The growing interest in physical (thermoreversible) gels (i.e., in gels whose space-network sites have a physical nature) is primarily due to the possibility of producing superstrong fibers from them (gel-technology method).In the rheological tests of UHMWPE physical gels (Carri-Med CSL 100 rotary viscosimeter), it has been established ( Fig. 2) that, with a certain critical concentration of the polymer in the solution C * , we have a significant growth of nearly five orders of magnitude (from 10 to 10 5 Pa) in the shear modulus of the polymer system. This, in turn, points to the process of gelation and the occurrence of a continuous space network in the polymer system. It has turned out that the value of C * substantially depends on the molecular weight of the polymer (see Table 1) and decreases with its growth.Using the IR-spectroscopy method we have been able to show (Fig. 3) [3] that the sites of the space network of a UHMWPE gel are crystalline in character. Beginning from very low concentrations, a characteristic 720/731 cm −1 "crystalline" doublet appears in the IR spectrum of the system. An increase in the gel temperature led to a significant reduction in the intensity of this doublet, which was attributable to the weakening of the crystalline sites and their fusion at 90 o C, when the 731-cm −1 "crystalline" band disappeared, and the gel transformed into the state of a solution. In cooling of the solution, a reverse transition to the gel state occurred, and the IR spectrum regained its initial form. An efficient method of studying the supermolecu...

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Study of Gelation in Aqueous Solutions of Cysteine and Silver Nitrate

Cited by 29 publications

References 3 publications

Controlled Release of Biologically Active Silver from Nanosilver Surfaces

Controlled Release of Biologically Active Silver from Nanosilver Surfaces

Mechanism of gelation in low-concentration aqueous solutions of silver nitrate with l-cysteine and its derivatives

Rheology of gelating systems

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