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0SYNTHESIS OF NANOPARTICLES OF Ag/Cu COMPOUNDS ON THE BASIS OF EXOPOLYSACCHARIDE MATRIX OF AZOTOBACTER CHROOCOCCUMXH2018 AND PHYSICAL AND CHEMICAL CHARACTERIZATION
1Rasulov Bakhtiyor Abdugafurovich, 2Pattaeva Mohichehra Abdusattarovna, 3Pattaev
Akmaljon Abdusattarovich
1,2Laboratory of biotechnology and nanotechnology, Institute of Genetics and Plants Experimental Biology, Uzbekistan Academy of Sciences 3Andijan Institute of Agriculture and Agrotechnologies https://doi.org/10.5281/zenodo.11079677
Abstract. In current research it was biofabricated nanobiomaterial with 46.3% Ag-, 9.0% Ag20-, 3.5% AgO-, 20.6% Cu- and 20.6% CmO-nanoparticles or 57.7% Ag, 39.0% Cu or 3.4% O on the basis of exopolysaccharide matrix of Azotobacter chroococcum XH2018. The crystal properties of the nanobiomaterial was characterized with the help of XRD (X-ray diffraction).
Keywords: microorganism, exopolysaccharide, (Ag/Cu) compounds, nanoparticle, spectroscopy, Azotobacter chroococcum.
Introduction
Production of nanoparticles (NP) based on microorganism exopolysaccharide (EPS) matrices is currently one of the most convenient methods for obtaining nano biomaterials [1]. Based on bacterial EPS, a number of NPs, in particular Ag-, AgCl-, Ag/AgCl-NPs, have been synthesized and characterized.
Within the framework of this research, work was also carried out on the creation of nanobiomaterials containing nanoparticles of silver and copper compounds based on the EPS matrix of Azotobacter chroococcum XH2018 strain and their physico-chemical characterization.
Materials and methods
Bacterial strain. In this study, the exopolysaccharide of Azotobacter chroococcum XH2018 strain, studied in previous studies, was used. The strain was grown in conventional liquid Ashby medium (sucrose - 20 g/l; MgSO4-7H2O - 0.2 g/l; KH2PO4 - 0.2 g/l; CaCO3 - 5 g/l; pH - 6.8-7.0) and in solid medium (above 15 g/l agar is added to the nutrient medium) was kept. In order for the strain to intensively produce EPS, it was grown in liquid Ashby medium for 3 days at a temperature of 28-30°C and in a deep method at a speed of 150-180 rpm [1].
Extraction of EPS from culture fluid of A. chroococcum strain XH2018. To isolate EPS samples from strain culture fluids, they were first centrifuged at 4°C at 10,000 rpm for 10 minutes, and the supernatant free of cell biomass was separated. EPS was precipitated by adding 1:2 volume of refrigerated absolute ethanol to the obtained supernatant. After separation, the resulting precipitate was again washed in absolute ethanol. After extracting the ethanol, the samples were dried in a vacuum desiccator for 24 hours [1].
Synthesis of Ag- and Cu-compound nanoparticles based on A. chroococcum XH2018 strain EPS matrix. Synthesis of nanoparticles of Ag+ and Cu+2 compounds based on EPS matrix was carried out in two stages. First, NPs containing Ag compounds was formed on the basis of EPS matrix, then Cu/Cu2O-NPs was impregnated into the same matrix.
Experimental conditions and standards of reagents were developed within the framework of this study. 0.2 g of Cu/Cu2O-NPs and 0.34 g of AgNO3 salt were mixed with 200 ml of A. chroococcum strain XH2018 EPS colloidal solution. The reaction mixture was kept at room temperature until the color changed. The mixture not absorbed into the EPS matrix was filtered off and the filtrate was mixed with absolute ethanol. Ethanol was poured until the precipitate was completely separated. The precipitate formed was separated and washed again with ethyl alcohol. The washed precipitate was dried at room conditions.
X-ray structural analysis (XRD) of nanobiomaterial. X-ray structural analysis of nanobiocomposites was performed on a Bruker D8 advance device. For this purpose, the dried sample was placed on the microscope window and the diffractogram was analyzed in Cu-K a radiation and nickel monochromator filter wave at 40 kV voltage and 30 mA current [1].
Results
Using the EPS macromolecule as both a reducing agent and a stabilizing agent, nanoparticles of silver and its compounds can be formed. In this process, the Ag+ ion is returned to a neutral, i.e., atomic state. Atomic silver is placed in the EPS matrix in nanoscale [3, 4]. Based on this, in order to collect nanoparticles of silver and copper compounds, silver nanoparticles are first synthesized in the EPS matrix. This process is essentially a chemical process. At the same time, Cu/Cu2O-NPs was added to the reaction mixture during the reduction of Ag+ to Ag0 in the EPS matrix.
It can be explained that this change consists of two parallel processes. The first is the reduction of silver ions and the deposition of atomic silver in the EPS matrix. The second is the direct absorption of Cu/Cu2O-NPSs into the EPS matrix. As a result of this process, nanoparticles of Ag compounds and Cu/Cu2O-NPS are simultaneously removed from the EPS matrix.
AgNO3 10 nM solution was used as silver source in our experiments. Based on the above process, a nanobiomaterial containing Ag/Ag2O/AgO/Cu/Cu2O-NPs was obtained. Notably, the silver cation in AgNO3 formed Ag2O- and AgO-NPs in the biological matrix in addition to Ag0. It was determined that the crystal structure of the final nanobiomaterial consisted of 46.3% Ag-, 9.0% Ag2O-, 3.5% AgO-, 20.6% Cu- and 20.6% Cu2O-NPs (Table 1). According to the composition of the element, it was observed that it consists of 57.7% Ag, 39.0% Cu and 3.4% O (Table 2).
Table 1
Mass fraction of constituents of Ag/Ag2O/AgO/Cu/CmO-NPs based on A. chroococcum strain
XH2018 EPS matrix
Component Chemical formula Mass fraction, %
Silver Ag 46,3
Silver(I)-oxide Ag2O 9,0
Silver oxide AgO 3,5
Copper Cu 20,6
Copper (II)-oxide Cu2O 20,6
The X-ray structural composition of the resulting nanobiomaterial EPS@Ag/Ag2O/AgO/Cu/Cu2O-NPs showed the presence of peaks characteristic for each component (Fig. 1). It was found that Ag-, AgO-, Cu2O-, Cu-NPs crystals in the nanobiomaterial are cubic, and AgO-NPs crystals are monoclinic. All other parameters of the obtained nanobiomaterial are detailed in Table 3.
Table 2
Elemental composition of Ag/Ag2O/AgO/Cu/Cu2O-NPs based on A. chroococcum XH2018
strain EPS matrix
Element Mass fraction, %
Ag 57.7
Cu 39.0
O 3.4
Table 3.
Some characteristics of the crystal structure of Ag/Ag2O/AgO/Cu/Cu2O-NPs obtained on the basis of A. chroococcum XH2018 strain EPS matrix
№ 26 [°] d [Â] I/I0 (peak height ) Peak surface FWHM
1 29,30 3,0457 41,13 78,44 0,2000
2 32,10 2,7861 34,56 115,33 0,3500
3 36,27 2,4745 179,01 597,46 0,3500
4 37,98 2,3675 1000,00 3337,53 0,3500
5 42,17 2,1410 62,68 388,49 0,6500
6 43,17 2,0937 234,19 781,63 0,3500
7 43,89 2,0641 329,54 942,73 0,3000
8 44,15 2,0497 238,90 1139,07 0,5000
9 46,08 1,9684 27,92 133,10 0,5000
10 50,30 1,8125 57,69 220,03 0,4000
11 61,28 1,5116 27,06 141,90 0,5500
12 64,28 1,4481 248,00 1300,68 0,5500
Fig. 1. X-ray structural spectrum of Ag/Ag2O/AgO/Cu/CmO-NPs based on A. chroococcum
strain XH2018 EPS matrix
It can be concluded from the experiments that nanoparticles of silver and copper compounds, including Ag", Ag2O", AgO", Cu" and Cu2O-NPs, were introduced into a single matrix.
This method makes it possible to combine the synergistic effects of different nanoparticles by summarizing their properties.
In general, our study also proved that bacterial EPS macromolecules serve as a means of assembling nanoparticles into a single matrix. In the next experiments, scientific studies on the introduction of nanoparticles into the matrix in a concentration-dependent manner will help to further fundamental research of this topic.
REFERENCES
1. Bakhtiyor А. Rasulov, Kahramon. D. Davranov, and Li Wen Jun, Formation of Ag/AgCl Nanoparticles in the Matrix of the Exopolysaccharide of a Diazotrophic Strain Azotobacter chroococcum XU1, Microbiology, 2017, 86(2), 1-6.
2. Bakhtiyor A. Rasulov, Parhat Rozi, Mokhichekhra A. Pattaeva, Abulimiti Yili, Haji Akber Aisa, Exopolysaccharide-based bioflocculant matrix of Azotobacter chroococcum XU1 for synthesis of AgCl nanoparticles and its application as novel biocide nanobiomaterial, Materials, 2016, 9, 528.
3. Hebeish A., Hashem M., Abd El-Hady M.M., Sharaf S. Development of CMC hydrogels loaded with silver nanoparticles for medical applications // Carbohydr. Polym.- 2013.-№ 92.-р.407-413.
4. Breitwieser D., Moghaddam M.M., Spirk S., BaghbaNPSadeh M., Pivec T., Fasl H., et al. In situ preparation of silver nanocomposites on cellulosic fiber-semicrowave vs. conventional heating. Carbohydrate Polymers. - 2013.-№ 94(1). р. 677-686.
