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FORMATION, STRUCTURE AND MORPHOLOGY OF NANOFIBER MAT ON THE BASE CARBOXYMETHYLCELLULOSE/POLYVINYL-ALCOHOL/SILVER NANOPARTICLES COMPOSITE
Kh.E.Yunusov
doctor of technical sciences, senior researcher, S.Sh.Rashidova doctor of chemical sciences, academician Institute of Polymer chemistry and physics, Academy of sciences of the Republic of Uzbekistan. polymer@academy.uz
Uzbekistan.
The properties of the final nanofiber mat biomaterials depend on the fabrication processing, characteristic initial reagents, and viscosity of the solutions [1]. Electrospinning [2] is a simple, versatile, and cost-effective technique to obtain flexible nano- to microscaled fibers from a wide variety of polymer solutions and polymer melts. However, electrospinning from biopolymers solutions in particular polysaccharides, is difficult because of the high viscosity, the ionic character, and, above all, the tendency to form gels via H-bonding among the polymeric chains [5].
Purified sodium-carboxymethylcellulose (Na-CMC) [6] is widely used in pharmaceuticals and medical practices due to its adhesiveness, biodegradability, biosolubility, and nontoxicity, as well as forming gels, suspensions, microneedles, nanofibers, and films and possessing sorption and stabilizing properties, making it suitable for drug delivery and active substances in the treatment of burn wounds, cancer and hemostatic pharmaceutical devices. Different concentrations of Na-CMC solutions perform a stabilizing function in the synthesis of metal nanoparticles and nanorods, and carboxymethyl groups are allowed to control their sizes and shapes during synthesis [8].
Polyvinyl-alcohol (PVA) is a biocompatible low-cost synthetic polymer with preferable chemical and thermal stability which is approved for use in many medical procedures. PVA can be an effective tool in electrospinning of biopolymers for generating dispersive effects and acting as a fiber formation support [9].
Silver nanoparticles (Ag NPs) have been applied in antibacterial medical textiles, wound dressings, antimicrobial catheters, medical masks, tissue engineering scaffolds, and water purification due to their strong bacteriostatic and bactericidal effects as well as broad-spectrum antimicrobial activities [10]. Ag NPs can be formed
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from their silver salts by via various approaches such as chemical, physical, irradiation, and biological reduction.
The aim of this work is to investigate the formation, structure, and morphology of nanofiber mats based on CMC/PVA/AgNPs and the study their structure, physicochemical characteristics and antimicrobial activity.
The electrospinning process was carried out using an instrument NanoNC eS-robot, Electrospinning/spray system, NanoNC, (Korea) equipped with a high-voltage supply (up to 28 kV), a dosing pump (0 to 60 mL/h feed rate), a syringe (1 mL) with a blunt-tipped needle internal diameter 353 mm which was connected to the positive electrode and an aluminum foil collector which was connected to the negative electrode (Fig. 1). It was found that the solutions of PVA/CMC at 50/50 ratio would yield the most uniform fibers and thus was selected for further experiments. Two routes of nanofibers formation was carried out the Ag NPs integration into the nanofibers.
In the first way, a solution of PVA/CMC/Ag+ was directly subjected to UV irradiation solution before the electrospinning process. In the second step, a solution of PVA/CMC/Ag+ solution was prepared at room temperature then subjected to electrospinning process. of PVA/CMC/Ag0 nanofiber mat were dried in a vacuum oven at a temperature of 30°C for 12 hours.
Various factors such as the Na-CMC, PVA and AgNO3 solutions concentration, irradiation wavelength and time affected the reduction efficiency and stability as well as the shape and size of the Ag NPs and the structure of the nanofibers.
The properties of the polymer solution, such as viscosity, surface tension, and conductivity, play a significant role in nanofiber formation. Higher concentrations typically result in thicker fibers due to increased solution viscosity and stretching behaviour. The choice of solvent or solvent mixture for dissolving the polymer affects its solubility and solution properties. The diameter and morphology of nanofiber obtained from Na-CMC/PVA, CMC/PVA/Ag+ and Na-CMC/PVA/Ag NPs solutions were studied by SEM studies. The nanofiber formed from Na-CMC/PVA solution at volume ratio 50:50 have an average diameter of 80-160±20 nm and smooth surface.
At the electrospinning of CMC/PVA solution containing silver ions (Ag+) the "beaded" nanofibers [12] are formed and an average diameter of nanofiber decreased to 60-110±20 nm.
The reason for this might be that beads are mainly caused by the surface tension which minimizes the surface area. In the case of no surface tension, the jet would be broken down into drops. Lower surface tension tends to form more beads in the
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electrospun products. The average the sizes in diameter of CMC/PVA/Ag NPs nanofiber is 50-130±20 nm.
The reversion of silver ions to silver metal under the action of an electric field in the electrospin process can also cause defect formation in nanofibers. It is advisable
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to conduct deeper scientific research in this direction.
In this study using Na-CMC and PVA as raw materials, deionized water as solvent and silver nitrate as antibacterial agent based on antibacterial nanofiber mates were prepared by electrospinning method. The spinnability of Na-CMC was increased by adding PVA and silver nitrate. The solutions of Na-CMC-/PVA/Ag+ and Na-CMC/PVA/Ag NPs were obtained and studied their physicochemical properties. The possibility of nanofiber formation from Na-CMC-/Ag+/PVA and Na-CMC/PVA/AgNPs solution by the electrospinning has been established.
New dipole-dipole bonds formed between asymmetric and symmetric carboxymethyl and hydroxyl groups of Na-CMC during interaction by Ag+ in the nanofibers of Na-CMC-/Ag+/PVA were detected in the 1601-1589.34 cm"1 range of the FTIR spectra. It was established that the carboxylate groups (COO-) within Na-CMC-/PVA/Ag+ macromolecules could play the role of «nanoreactors» where according to the theory of Mott-Gurney the carboxylic groups of Na-CMC «trap» the silver cations and promote the photostimulated formation of Ag NPs. During the electrospinning of Na-CMC/PVA solution containing silver cations, it was observed the formation of Ag NPs on the surface of beaded nanofibers due to electron irradiation restoration of silver cations. It was found that the formation of Ag NPs in the Na-CMC/PVA nanofiber depends on time of photolysis and content of Ag+. Different ratio of Na-CMC and PVA and their viscosity of solutions defines the sizes and morphology of nanofibers. The morphology and diameters of nanofiber were studied using an AFM and SEM analysis. The result confirmed that from the Na-CMC/PVA/Ag NPs solution, it could be obtained nanofibers with sizes in diameter of 50-130 nm.
The UV-spectroscopy, DLS and XRD analyses investigations has shown the Ag NPs with sizes of 5-26 nm were formed on the structure of nanofibers. The correlation between the sizes of nanofibers and content of Ag NPs immobilized within the nanofibers and their biological activity was established. It is shown that decreasing
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of sizes in diameter of nanofibers and content of Ag NPs enhances their antimicrobial activity. Nanofiber mat containing stable Ag NPs could be used as a bactericidal facemask for air filtration and for the treatment burn wounds.
Note: This work was supported by fundamental project FZ-4721055613 "Fundamental aspects of the formation of nanofibers based on macromolecular systems: conditions, structure formation, properties " for the years 2022-2026 by the Innovative development agency under the ministry of high education, science and innovation of the Republic of Uzbekistan.
Reference:
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