Facile method of preparing silver-embedded polymer beads and their antibacterial effect

Silver nanoparticles (AgNPs) have garnered attention due to their antimicrobial properties and applications in nanomaterials. The objective of this study is to compare the antimicrobial activities of AgNPs synthesized using green and traditional methods with silver ions (Ag+). The characterization of AgNPs was conducted through the utilization of UV-Vis spectroscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, X-ray diffraction, and differential pulse voltammetry (DPV). AgNPs presented quasi-spherical nature and well-dispersed characteristics, with a mean diameter around 10nm and 25nm for the traditional and green methods respectively. DPV measurements showed a decline of the area under the curve from 1.79 μA mm-2 to 0.7679 μA mm-2, indicating limited colloidal stability of green AgNPs. In contrast, traditional AgNPs demonstrated stability over time, maintaining an area under the curve of around 31 μA mm-2 over a 30-day period. The antimicrobial efficacy against Staphylococcus aureus and Escherichia coli was assessed via the broth dilution method. The results indicated that there were similar minimum inhibitory concentrations and minimal bactericidal concentrations (MIC and MBC) for both nanoparticle types and Ag+ against S. aureus (≈ 1 mM). While differences were detected against E. coli: traditional AgNPs evidenced lower MIC and MBC values on day 30 (≈ 0.5 mM) and Ag+ evidenced MIC and MBC values of 0.5 and 0.75 mM on both days 1 and 30. Green AgNPs exhibited heightened antimicrobial activity over time, as evidenced by the planktonic growth of S. aureus and E. coli in days 1 and 30. This observation is concomitant with an increase in Ag⁺ release evidenced by DPV, underscoring the key role of silver ions in mediating antibacterial effects. This research contributes to a more comprehensive understanding of how synthesis method, nanoparticle stability, silver ion release, and testing methodology influence the antimicrobial performance of AgNPs, offering insights critical for their practical application.

Owing to their antimicrobial properties, silver nanoparticles (NPs) are the most commonly used engineered nanomaterial for use in a wide array of consumer and medical applications. Many discussions are currently ongoing as to whether or not exposure of silver NPs to the ecosystem (i.e. plants and animals) may be conceived as harmful or not. Metallic silver, if released into the environment, can undergo chemical and biochemical conversion which strongly influence its availability towards any biological system. During this process, in the presence of moisture, silver can be oxidized resulting in the release of silver ions. To date, it is still debatable as to whether any biological impact of nanosized silver is relative to either its size, or to its ionic constitution. The aim of this review therefore is to provide a comprehensive, interdisciplinary overview--for biologists, chemists, toxicologists as well as physicists--regarding the production of silver NPs, its (as well as in their ionic form) chemical and biochemical behaviours towards/within a multitude of relative and realistic biological environments and also how such interactions may be correlated across a plethora of different biological organisms.

Green synthesis of nanoparticles using Calendula officinalis extract from silver sulfate and their antibacterial effects on Pectobacterium caratovorum

Введение. Проблема лечения инфицированных и длительно не заживающих ран остается актуальной в современной хирургии, вместе с тем количество госпитальных полирезистентных штаммов бактерий, участвующих в раневой инфекции, увеличивается. Одним из вариантов решения этой проблемы является разработка новых средств местного действия, в частности создание новых высокоэффективных раневых покрытий с антибактериальными и репаративными свойствами. С помощью специальной технологии из натурального биополимера хитозана получены нановолокна, обладающие сверхразвитой структурой и высокой сорбционной емкостью, непосредственно в состав которых в качестве антимикробных агентов введены ионы и наночастицы серебра и церия. Цель. Определить антибактериальную активность нановолокон хитозана и его модификаций по отношению к клиническим изолятам микроорганизмов. Материалы и методы. В эксперименте оценены антибактериальные свойства полученных образцов нановолокон хитозана в отношении госпитальных штаммов микроорганизмов методом диффузии в агар и количественным суспензионным методом. Результаты. Доказана высокая антимикробная активность исследуемых образцов. Наиболее высокую антимикробную активность проявили образцы, модифицированные ионами серебра, наночастицами серебра, а также комплексом наночастиц серебра и церия. При оценке антимикробной активности методом диффузии в агар значения зоны задержки роста у этих образцов имели наибольшие размеры в диапазоне от 11 до 18 мм. Это соответствует результатам оценки суспензионным количественным методом. Показатели фактора редукции (RF) указанных образцов превосходили иные и составляли от 4,3 до 5,9 при экспозиции 3 часа и от 4,62 до 5,23 при экспозиции 24 часа. Заключение. Отобраны наиболее перспективные образцы для дальнейшего изучения их лечебной эффективности на модели раневого процесса: нановолокна хитозана, модифицированные ионами серебра, наночастицами серебра и комплексом наночастиц серебра и церия. Introduction. The problem of infected and long-term non-healing wounds treatment remains relevant in modern surgery, while the number of hospital multi-resistant bacterial strains involved in wound infection is increasing. One of the options for resolving this issue is developing new local agents, in particular, new highly effective wound coatings elaboration having antibacterial and reparative properties. Using a special technology, nanofibers with an overdeveloped structure and high sorption capacity were obtained from the natural biopolymer chitosan with silver and cerium ions and nanoparticles introduced directly into their composition as antimicrobial agents. Purpose. To determine the antibacterial activity of chitosan nanofibers and its modifications against clinical isolates of microorganisms. Materials and methods. In the experiment, antibacterial properties of the obtained samples of chitosan nanofibers against hospital microorganism strains were evaluated using agar diffusion and quantitative suspension tests. Results. Proven a high antimicrobial activity of samples tested. The samples modified with silver ions, silver nanoparticles, as well as with a complex of silver and cerium nanoparticles showed the highest antimicrobial activity. When assessing the antimicrobial activity by agar diffusion test method, the growth inhibition zone in these samples had the largest dimensions in the range from 11 to 18 mm. This is consistent with the results of the evaluation by quantitative suspension test method. The reduction factor (RF) values of these samples were superior to the others and ranged from 4.3 to 5.9 at 3 hours exposure and from 4.62 to 5.23 at 24 hours exposure. Conclusion. The most promising samples were selected for further study of their therapeutic efficacy on the wound process model: chitosan nanofibers modified with silver ions, silver nanoparticles and a complex of silver and cerium nanoparticles.

Nano-silver composites with a thermoplastic polyurethane as the matrix were prepared by two different routes. Using the so-called in situ preparation, silver nanoparticles were obtained by a thermal reduction of silver acetate during melt mixing. In addition, a more sophisticated ex situpreparation method was developed. Here, the silver nanoparticles are synthesized in an invertible polyester resulting in much smaller particle sizes. The particles obtained are surrounded by the polyester cage, which stabilizes them with respect to agglomeration. Hence, an incorporation of those particles into a polymer melt with common techniques like extrusion leads to an even distribution. This is due to the fact that the invertible polyester and the polymer matrix are entirely miscible which was proven with DSC measurements. The silver ion release of the composites prepared was measured with anodic stripping voltammetry. At a constant weight percentage of silver in the polymer, the composite with the ex situsilver nanoparticles exhibits a silver ion release which is about two orders of magnitude higher than the release from the composite with the in situsilver nanoparticles. This observation is explained by the higher specific surface area of the smaller particles and a higher coefficient of diffusion for silver ions. A concentration of only 0.07 wt% silver nanoparticles, prepared with the ex situ method, exhibits a high enough release of silver ions to achieve antimicrobial properties.

The objective of this study was to determine the most stable conformation of L-tryptophan (L-Tryp) on gold and silver nanoparticles. Additionally, this work investigated how these parameters were influenced by analyte concentration, nanoparticle size, and pH. The purpose of this study was to establish whether L-Tryp molecules interact with the nanoparticles through the carboxylate end, the amino group end, or both. This research has diverse applications in biophysics and medical diagnostics, potentially opening up new avenues in these fields. Moreover, it may enrich the disciplines of chemistry and nanotechnology by offering innovative approaches for future research. These findings represent a significant advancement in understanding the interactions between L-Tryp and nanoparticles, making a meaningful contribution to biophysics and medical diagnostics. Surface-Enhanced Raman Scattering (SERS) spectra of L-Tryp in the 100–4000 cm−1 spectral range were obtained using a 785 nm laser for excitation. Gold (Au) and silver (Ag) nanoparticles (NPs) were synthesized using the citrate reduction method. The experimental procedure involved the use of electrolytes (such as NaCl) for colloid activation, which resulted in very high SERS signals. Modification of nanoparticle surface charge was achieved by adjusting the pH of Au and Ag colloidal suspensions between 2 and 11. The SERS spectra indicate that small-sized nanoparticles require high concentrations of L-Tryp to achieve high sensitivity, whereas larger nanoparticles perform effectively at lower concentrations. The pronounced enhancement of stretching vibrations in the COO− group in the SERS spectra strongly suggests that the carboxylate group attaches to silver nanoparticles (AgNPs). Conversely, for gold nanoparticles (AuNPs), a new band at approximately 2136 cm−1 was observed, indicating that the amino group of L-Tryp interacts with Au in its neutral form. These analyses were complemented by theoretical modeling, employing Density Functional Theory (DFT) calculations run using the Gaussian program to study molecular models in which L-Tryp interacted with AgNP and AuNP substrates in neutral, cationic, and anionic forms.

Intracellular biosynthesis of Au and Ag nanoparticles using ethanolic extract of Brassica oleracea L. and studies on their physicochemical and biological properties

In parallel with the growing use of nanoparticle-containing products, their release into the environment over the coming years is expected to increase significantly. With many large population centers located in near-coastal areas, and increasing evidence that various nanoparticles may be toxic to a range of organisms, biota in estuarine and coastal waters may be particularly vulnerable. While size effects may be important in cases, silver nanoparticles have been found to be toxic in large part due to their release of silver ions. However, there is relatively little data available on how nanoparticle coatings can affect silver ion release in estuarine or marine waters. We have found that albumin, as a model for biocorona-forming macromolecules which nanoparticles may encounter in wastewater streams, stabilizes silver colloids from agglomeration in high salinity marine waters by electrosteric repulsion for long time periods. A minimum mass ratio of about 130 for albumin:silver nanoparticles (40 nm) was required for stable dispersion in seawater. Increasing albumin concentration was also found to reduce dissolution of nanoparticles in seawater with up to 3.3 times lower concentrations of silver ions noted. Persistent colloids and slow sustained ion release may have important consequences for biota in these environmental compartments.

Curious germophobes can rejoice: Researchers have figured out how silver nanoparticles, found in many consumer products, kill bacteria. The culprits are the silver ions the nanoparticles emit, not nanoparticle-specific biological effects (Nano Lett., DOI: 10.1021/nl301934w). Manufacturers add silver nanoparticles to cosmetics and clothing to kill germs. Yet debate rages about how they work. When exposed to air in an aqueous solution, silver nanoparticles release silver ions, which have known antibacterial properties. Researchers have been unable to rule out a role for the nanoparticles themselves. Now, postdoc Zongming Xiu, professors Vicki L. Colvin, and Pedro J. J. Alvarez, and colleagues at Rice University have synthesized and tested silver nanoparticles’ antimicrobial properties under anaerobic conditions, which prevent release of silver ions. In their tests, ionic silver killed Escherichia coli even at concentrations as low as 15 parts per billion. The silver nanoparticles themselves weren’t toxic to...

Comparing ex vivo and in vitro translocation of silver nanoparticles and ions through human nasal epithelium

Получены алюмогели, содержащие наночастицы (НЧ) серебра, и оценено их использование в качестве материалов для одновременного концентрирования пирена и его детектирования методом гигантского комбинационного рассеяния света (ГКР). НЧ серебра предварительно подвергали искусственной агрегации с помощью хлорида натрия. Изучены сорбционные свойства полученных алюмогелей по отношению к пирену, и показано повышение степени извлечения пирена на сорбентах, модифицированных додецилсульфатом натрия (ДДС). Оценена возможность определения пирена, выделенного на сорбенте, методом ГКР-спектроскопии.

The aim of this work was to probe the biodistribution and toxic effects of silver nanoparticles (NPs) with powerful anti-bacterial and anti-virus activities. For this purpose, novel silver NPs with gold nanorod (NR) core and silver shell (Au@Ag NRs) were developed and employed as a model material. The inner gold core provided an excellent internal reference for tracking the NRs in vivo. After subcutaneous injection of Au@Ag NRs, silver and gold contents in the subcutis and organs were examined by inductively coupled plasma mass spectrometry at different time points within 28 days. Histological analysis, physiological function and complement faction 3 (C3) and 5a (C5a) measurement were performed over time to reveal the toxic effect of Au@Ag NRs in vivo. Experimental results showed that majority of the Au@Ag NRs remained in the injection site except for a small amount migrating into the lymph nodes. The silver shell was dissolved in the subcutaneous tissue and released silver ions rapidly, which resulted in detectable silver accumulation in most of the organs. The accumulated silver ions in the kidney not only interacted with the kidney cells membrane but also induced a rapid increase of complement fraction C3 followed by a significant consumption and C3a and C5a production significantly in the serum, which resulted in kidney oxidative damage and eventually led to the morphological changes and filtration function impairment of the glomerulus. The released silver ions also caused oxidative injury of subcutaneous tissue in the injection site.

In the current work, a new antibacterial bandage was proposed where diamond-like carbon with silver nanoparticle (DLC:Ag)-coated synthetic silk tissue was used as a building block. The DLC:Ag structure, the dimensions of nanoparticles, the silver concentration and the silver ion release were studied systematically employing scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic absorption spectroscopy, respectively. Antimicrobial properties were investigated using microbiological tests (disk diffusion method and spread-plate technique). The DLC:Ag layer was stabilized on the surface of the bandage using a thin layer of medical grade gelatin and cellulose. Four different strains of Staphylococcus aureus extracted from humans’ and animals’ infected wounds were used. It is demonstrated that the efficiency of the Ag+ ion release to the aqueous media can be increased by further RF oxygen plasma etching of the nanocomposite. It was obtained that the best antibacterial properties were demonstrated by the plasma-processed DLC:Ag layer having a 3.12 at % Ag surface concentration with the dominating linear dimensions of nanoparticles being 23.7 nm. An extra protective layer made from cellulose and gelatin with agar contributed to the accumulation and efficient release of silver ions to the aqueous media, increasing bandage antimicrobial efficiency up to 50% as compared to the single DLC:Ag layer on textile.

Nano-galvanic coupling for enhanced Ag+ release in ZrCN-Ag films: Antibacterial application

Pulsed laser deposition of Ag nanoparticles on titanium hydroxide/oxide nanobelt arrays for highly sensitive surface-enhanced Raman spectroscopy