Open access peer-reviewed chapter - ONLINE FIRST

Ozonation of Non-Woven Ultrathin Fibrous Biomaterials for Medical and Packaging Implementations

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Olga Alexeeva, Valentina Siracusa, Marina L. Konstantinova, Anatoliy A. Olkhov, Alexey L. Iordanskii and Alexandr A. Berlin

Submitted: 27 June 2022 Reviewed: 30 August 2022 Published: 15 November 2022

DOI: 10.5772/intechopen.107508

Ozonation - New Aspects IntechOpen
Ozonation - New Aspects Edited by Murat Eyvaz

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Ozonation - New Aspects [Working Title]

Associate Prof. Murat Eyvaz, Dr. Ahmed Albahnasawi, Dr. Ercan Gürbulak and Prof. Ebubekir Yüksel

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Abstract

Antibiotic resistance of pathogens is among the major concerns in various medical applications. Therefore, the search for the novel antimicrobial agents that could prevent pathogen’s resistance, while maintaining efficient treatment, is one of the most important issues for biomedicine nowadays. One of the relevant methods for the development of functional non-woven materials possessing antimicrobial properties is the use of ozone and ozonolysis products for the modification of fibrous materials. This approach has recently attracted both academic and industrial interest and has found various biomedical applications. Several methods providing antimicrobial properties to textiles using ozone or ozonolysis products were proposed, including encapsulation and/or direct introduction of ozone-generated antimicrobial agents into the fibrous polymer matrix and ozone treatment of non-woven fiber materials. For the latter, the ozonolysis products are uniformly distributed predominantly on the polymer surface but could be also formed inside the polymer bulk due to ozone diffusion through the amorphous areas or defects. It was found that ozone modification of fibrous materials could lead to increase in hydrophilicity and improvement in their functional properties (smoothness, elasticity, strength, antimicrobial activity). In this chapter, various aspects of ozone modification of non-woven fiber materials for biomedical applications are reported and discussed.

Keywords

  • ozone
  • non-woven
  • ultrathin
  • biomaterials
  • packaging
  • health

1. Introduction

Over the past decades, functional nonwoven materials, obtained by modern nanotechnological methods, have been intensively studied at the academic and industrial levels [1, 2, 3]. Commercially available, biodegradable polymers produced as ultrafine fibers are gaining more interest as a result of their high surface/volume ratio, biocompatibility, non-toxicity in the body, and environmental compatibility. Due to their thermoplasticity and the ability to form solutions with bioactive compounds, they can be directly introduced into biomedical or packaging materials to give them new functional properties, including antimicrobial ones [4, 5, 6, 7].

The search for new antimicrobial substances that can simultaneously reduce the resistance of pathogens to antibiotics and maintain high therapeutic activity is one of the most important modern tasks of biomedicine and the packaging industry [8, 9]. The success of the use of bactericidal plastics [10] is based on the absence of the ability to cause allergic reactions and the possibility of implementing controlled biodegradation, as well as on improved mechanical and barrier characteristics that expand the scope of their application [11, 12, 13].

Currently, a number of studies are underway aimed at the use of antimicrobial agents in fibers and nonwovens in medicine. For example, lipid systems containing omega-3 fatty acids or omega-3 fatty acids and liposomes are incorporated into woven, non-woven cotton substrates by impregnation. Also, the use of fibrous materials with a drug already introduced into the biopolymer [14, 15, 16, 17]: dipyridamole and tetraphenylporphyrins is being actively studied. Based on the evaluation of release profiles, textiles are expected to be useful for wound healing and anti-inflammatory applications.

Bactericidal materials providing an effective barrier and selective properties belong to the class of active packages. This is a modern trend in the development of innovative materials for the food, cosmetics, and agriculture industries, in addition to their active functions [18]. The bactericidal properties of barrier materials can be achieved by encapsulating antiseptics/antibiotics in a matrix or on the surface of the packaging material, which leads to the suppression of microbial growth by reducing the population of microorganisms and reducing their growth rate [19]. In this case, the period of active operation of the package and the storage time of the product increase significantly along with an increase in the safety of transportation.

The development and production of ultrathin biodegradable fibers by electrospinning made it possible to create new fibrillar materials, the intensive use of which is clearly observed in many interdisciplinary areas [20, 21, 22]. Electrospinning is a technically simple and at the same time universal method for obtaining ultrathin fibers in the micro- and nano-ranges of their diameters, which contributes to the widespread use of this nanotechnology for the design of structural and functional materials with innovative performance characteristics. Fibrillar nanosized materials have high porosity and large specific surface area, which allows them to be used as highly efficient filters and absorbents. In addition, electroformed polymeric materials can be successfully modified with various biologically active compounds, biomolecules, and carbon nanomaterials [23]. The introduced additives should have good compatibility with the polymer and be safe for use in biomedical and environmental issues [24].

The use of ozone and ozonolysis products for fibrous materials modification is one of the innovative approaches to the creation of functional micro- and nanomaterials with antimicrobial properties. Ozone, as an individual gaseous compound, is the strongest oxidizing agent and, therefore, a powerful disinfectant [25, 26]. Based on the analysis of the ozonolysis kinetics, it became possible to accurately dose its concentration and obtain ozonolysis products with the necessary disinfecting properties [27]. For example, when ozonizing vegetable oils, ozone reacts with unsaturated triacylglycerols contained in them (Figure 2) [28]. The oil ozonation product is a non-toxic, biocompatible, and biodegradable material, and is also a promising additive for introduction into the fibrillar matrix through electrospinning [29]. Combining the plasticizing properties of ozone-modified germicidal oils and the specificity of electroformed materials, it is possible to obtain a fundamentally new product with improved characteristics.

Another method of introducing the active agent into the fibrillar matrix is the use of encapsulated antimicrobial agents. Numerous studies have developed and successfully tested microcapsules containing ozonolysis products with antimicrobial properties for the manufacture of fibers and fibrillar materials for medical purposes [30, 31]. So, for example, in the case of bioactive textile material, the task of modern developments is to prevent infections in case of osteotrauma, to promote the healing of wound complications, and the general improvement of the body. Ozonated oil capsules are prepared and encapsulated by a coacervation method using GE and GA (GE (from porcine skin, type A) and GA (from the acacia tree)) as the wall material. Usually, the antimicrobial activity of both the oil and the microcapsules is tested [32].

The third methodical approach is the direct treatment of nonwoven fibrous materials with ozone to form bactericidal ozonolysis products. It has been established that the oxygen-containing functional groups formed as a result of the reaction are rather uniformly distributed over the polymer surface [33]. However, due to gaseous diffusion, ozone reacts not only on the surface of the polymer, but also penetrates into the volume, distributing in its amorphous regions.

This review article focuses on recent advances in the modification of nonwovens with ozone and its derivatives to give them anti-inflammatory, antibacterial, or antifungal properties for medical and packaging applications.

1.1 Antibacterial properties

Ozone can play a role in medicine [34, 35] as well as in other areas due to its antibacterial properties and the continued spread of the phenomenon of antibiotic resistance [36, 37, 38], that is, the inability of antibiotics to effectively fight infections and bacteria, a phenomenon defined by the excessive and often inappropriate use of antibiotics as for people as well as for animals.

The World Health Organization (WHO) estimated that already hundreds of thousands of people are suffering from antibiotic-resistant infections, and many people are at serious risk. The most dangerous situation is associated with Escherichia coli, with a percentage of methicillin resistance of more than 30% [39, 40]. Thus, drug resistance is a serious problem affecting not only public health, but also the development of global progress [41]. The main cause of antibiotic resistance is the mcr-1 gene, which allows bacteria to resist the most potent chemical and pharmaceutical drugs [42, 43]. Bacterial resistance to antibiotics depends on various factors, such as structural changes in the surface membranes of the bacterial cell, which reduce the penetration of the antibiotic. Resistance in Gram-negative bacteria may be related to changes in the protein coat through which many antibiotics penetrate [44].

Generally, most antibiotics have selective selectivity concern to various strains of bacterial microflora. Therefore, the choice of the most effective antibiotic is a sufficiently common problem. One of the universal antibacterial agents is ozone and its derivatives. Ozone has an oxidizing ability that can kill bacteria by attacking the molecular structure of their protective membranes and altering internal enzymes [45]. This mechanism is very similar to that used by leukocytes in bacterial phagocytosis [46]. It is also extremely effective against viruses, fungi, mold, pesticides, heavy metals, nitrates, nitrites, and other potentially harmful substances [47]. The antibacterial effect of ozone can occur both directly during the treatment of various materials or products with this gas (short-term exposure), and ozone compounds (ozonides) applied to the surface or into the volume of materials (prolonged exposure). The antibacterial effect of ozone can occur both directly during the treatment of various materials or products with this gas (short-term exposure), or ozone derivatives (ozonides) applied to the surface or into the volume of materials (prolonged exposure).

1.2 Ozone obtaining and the ozonolysis process of non-woven materials and oils

Ozone is a triatomic inorganic molecule [48] consisting of three oxygen atoms. It is unstable and under certain conditions, such as pressure and temperature, it decomposes into oxygen atoms with a short life span, due to which it decomposes into its original form after a certain period of time [49].

Since the ozone molecule is unstable, ozone must be used immediately at the point of production. Ozone generators are used to produce ozone. Currently, ozone is produced in industrial conditions in 3 ways:

  • By means of UV irradiation [50]. Air containing oxygen or purified oxygen is passed through a special chamber, where, under the influence of short-wave UV radiation, an oxygen molecule dissociates into two atoms, and then ozone is formed by the fusion of an atom and a whole oxygen molecule.

  • Electrolytic [51]. It is based on electrochemical reactions: when current is passed through electrolyte solutions placed in special cells, water molecules decompose with the formation of atomic oxygen and then ozone.

  • The method of producing ozone by electrosynthesis using a corona discharge [52] is widely used in industry, since it is the most efficient and reliable of all the above. It is distinguished by the optimal ratio of power consumption to the concentration of generated ozone.

The appearance of a corona discharge in a gaseous medium occurs between two high-voltage electrodes separated by a discharge gap and a dielectric in an inhomogeneous electric field, see Figure 1.

Figure 1.

Corona discharge chamber.

Ozone is formed as a result of the dissociation of an oxygen molecule under the action of the energy of electrons moving between the electrodes through the discharge gap (Figure 1). The ozone concentration depends on the magnitude of the voltage, its frequency, thickness and dielectric constant of the dielectric. In addition, important parameters, in this case, are the concentration of oxygen in the supplied gaseous medium, the type of gas forming it, the pressure, and the degree of purification of oxygen and the gaseous medium.

О2+ee+O·+O·E1
O·+2О3+O2E2

Where, e is a high-energy particle, such as an electron, photon, excited buffer gas atom or molecule, impurities, etc.

In all sources of ozone synthesis, along with the reactions of its formation (1) and (2), there is also a group of reactions of its decomposition. The latter can be represented as a sequence of chemical processes (3)(6) [49, 53, 54, 55]:

О3+eO+О2E3
О3+O·О2+O2E4
O·+О3+O2O3+О2E5
О3О·+O2E6

At moderate and low concentrations, the advantage of ozone is its environmental friendliness, which expands the scope of its application as an oxidizing agent, fungicide, deodorizer, and disinfectant. The production and use of ozone does not lead to secondary pollution of the environment, and it does not produce unwanted by-products. Unused ozone, decaying, again turns into gaseous diatomic oxygen.

Ozone has a high oxidizing ability, due to which it is able to act on bacteria, protozoa, viruses, and fungi, breaking the intermolecular bonds of high-molecular compounds and violating the integrity of their shells. Due to these properties, ozone is widely used in various fields of medicine, in particular, as a substitute for antibiotics [56] and medicines, to which resistance has developed in the microbial environment in recent years [57]. Ozone therapy is a medical approach that has become widespread in some regions of Europe and South America [58]. The properties of ozone also have a positive impact in the agricultural sector: in the cultivation and production of plants to replace chemical and pharmaceutical products; in the food, industrial, textile, and paper industries; and in water disinfection, both for drinking water [59] and wastewater treatment [26].

Ozone successfully competes with other disinfectants, such as Cl-derivatives [60], providing, unlike the latter, a safe bactericidal treatment that does not involve the use of chlorine and chlorides and the formation of dioxins. In-resort areas and wellness centers today, most pools and spas use predominantly ozonized water. Ozone practically does not change the characteristics of water, especially its taste and clarity, and drastically reduces the content of harmful by-products.

Ozone has a special effect on vegetable oils. Due to the unsaturated carbon chemical bonds found in their molecular structure, ozone is able to enter into a chemical reaction with the formation of ozonides. These compounds have unique properties that allow the use of these compounds in medicine, cosmetology, and packaging.

1.3 Ozonated oils

Olive oil and its wide range of medicinal properties have been known to mankind for thousands of years. Hippocrates also advised the use of olive juice to treat ulcers and alleviate mental illness. Later, in the Middle Ages, olive oil was used in the treatment of heart disease, gynecological infections, and even fever. It has been demonstrated that it is possible to further improve the properties of oils by treating them with ozone.

Treatment of vegetable oils with ozone is also being actively studied. When treated with ozone, gaseous ozone dissolves in vegetable oils and forms ozonides [61]. For example, when vegetable oils are ozonized, ozone reacts with the unsaturated triacylglycerols contained in them (Figure 2). The ozonation of olefins is usually considered within the framework of the mechanism postulated by Criegee [62]. This mechanism describes the reaction of unsaturated ozone to form the initial unstable primary ozonide molecule (R - C - O3 - C - R’). This primary ozonide readily decomposes to form the zwitterion and the carbonyl groups. These groups can then combine to form a trioxolane compound, which is a non-toxic, biocompatible, and biodegradable material [63, 64], may be a promising additive for introduction into a fibrous matrix.

The ozonides obtained in the process are responsible for the broad biological activity of ozonized vegetable oils. The introduction of ozonized oils in the polymer matrix is possible only if the process is low-temperature, since the formation from the melt may completely decompose the ozonized oil, and all the antibacterial properties necessary for the future product will be lost. One of the possible low-temperature methods for preparing nonwoven mats is electrospinning (Figure 3).

Figure 2.

Chemical structures of ozonated derivatives are formed by the chemical reaction of ozone with unsaturated triglycerides: Trilinoleate (a) and Trioleate (B). The primary ozonides are transient, unstable species that rearrange in the normal, secondary ozonides also known as Criegee ozonides.

1.4 Electrospinning and its basic principles

Electrospinning involves an electrohydrodynamic process during which a drop of liquid is electrified to create a jet, followed by stretching and elongation to form fibers [65]. As shown in Figure 3 (A and B), the basic setup consists of a high voltage AC or DC power supply, a syringe pump, a spinneret, usually a needle, and a conductive collector. During electrospinning, theliquid is squeezed out of the spinneret, forming a suspended drop due to surface tension [66]. Due to the electrostatic repulsion of surface charges of the same sign during electrization, a liquid drop is deformed into a Taylor cone, from which a charged jet is ejected. At first, the jet propagates in a straight line, and then, due to the instability of the bend, it makes energetic movements. As the jet expands to smaller diameters, it rapidly solidifies, resulting in the deposition of hard fibers on the horizontal collector [67].

Figure 3.

Schematic illustration showing the electrospinning process (a) and the process of obtaining ultra-fibrous material (b).

The formation of electrospun fibers and the control of their diameters are largely determined by the applied voltage, fluid flow rate, and the distance between the spinneret tip and the collector.

1.5 Introduction of ozonated oils directly into the non-woven fiber

Combining the plasticizing properties of ozonized oils with active antimicrobial activity and the properties of electroformed mats, we obtain a promising product with improved characteristics.

The authors [29] succeeded in introducing the oil ozonation product, glycerol (9,10-trioxolane) trioleate (ozonide of oleic acid triglyceride (OTOA)), into the electrospinning polymer matrix to obtain highly porous medical fibers. Fundamentally, new non-woven mats based on PLA with the addition of OTOA (1, 3, and 5 wt.%) were obtained. Modified non-woven mats have improved characteristics: improved tissue morphology, thermal, physical-mechanical, and physico-chemical properties compared to unmodified fabrics (Figure 4).

Figure 4.

SEM images of nonwoven fiber PLA mats and magnified monofilaments: Pristine PLA (a, b), PLA + 1% OTOA (c, d), PLA + 3% OTOA (e, f), PLA + 5% OTOA (g, h). Distributions of fiber diameters for studied PLA fibrous samples [29].

Fiber diameter measurements for PLA nonwoven fiber mats with different OTOA content showed that the neat PLA fiber mats had an average fiber diameter of 5.7 ± 2.3 μm, while the effect of adding OTOA was to increase the average fiber diameter from 5.7 μm to 8–9 μm, observed for all samples containing OTOA. The PLA fiber material with 3% OTOA showed the most uniform fiber size distribution. Analysis of the surface of pure PLA fibers showed no pores in the high magnification SEM image, while samples of PLA with the addition of OTOA clearly show the presence of mesopores distributed over the entire surface of the fiber. The pores have an arbitrary shape with sizes in the range of 0.2–1 μm.

Аccordingly, an increase in fiber porosity increases its sorption characteristics. Since the medical applications of fibrous materials require contact with various water-containing physiological media, a study was made of the sorption capacity of PLA-OTOA fibrous mats. An unmodified PLA mat and a similar mat with 1% OTOA substance are characterized by a low sorption capacity compared to samples containing 3% OTOA. With an increase in the total porosity of the fiber, its sorption capacity also grows symbatically. The effect of increasing porosity was confirmed by measurements of the specific surface area of ​​PLA fiber mats, which were obtained by nitrogen adsorption. The specific surface of the fibrous material (S, m2/g) increased significantly with the addition of OTОA, reaching a maximum value of 3.1 m2/g at an OTOA content of 3%.

The DSC results demonstrate a significant effect of the amount of OTOA introduced on the degree of crystallinity of the final material. Analyzing the obtained results, we can conclude that the introduction of an OTOA additive into PLA fibers leads to a plasticizing effect, which is expressed in a noticeable decrease in the cold crystallization temperature of 20.5°C, a decrease in the glass transition temperature by 6°C, and a change in the melting temperature of the polymer (−4, 5°C). All these phenomena are unequivocally associated with an increase in PLA segmental mobility due to plasticization. In this case, a decrease in the enthalpy of cold crystallization and the degree of crystallinity of the fibers from 16.3 to 7.3% was observed, which should also be associated with the destruction of a part of the crystal structure under the action of the plasticizer.

Changes in the structure of modified PLA mats have a significant impact on their mechanical characteristics. The PLA fibrous material with 1% OTOK showed a significantly improved tensile strength compared to the original PLA. With the introduction of 1% OTOK, the relative elongation slightly increases compared to the original PLA, however, the addition of 3% OTOK significantly improves the elongation of the material by more than 30%. For the PLA+ OTOA 5% sample, a moderate decrease in elongation is observed. Such a behavior of the mechanical properties of the modified fibers directly indicates the plasticizing effect from the introduction of OTOA, which is directly related to the change in the structural-dynamic state of the amorphous regions of PLA.

The obtained results of the study of electroformed PLA mats modified by OTOA indicate the possibility of controlling the morphology of the obtained materials; their water absorption capacity, as well as thermal and mechanical properties by varying the OTOA content in the PLA matrix. Thus, the nonwoven PLA material with 3% OTOA showed the best functional characteristics among all studied PLA + OTOA samples, providing highly porous surface morphology, increased specific surface area and high water sorption.

The mechanical properties of this material showed increased strength and elasticity of PLA + 3% OTOA. The chemical interaction between the PLA matrix and OTOA is confirmed by the FT-IR results. Analysis of DSC data and mechanical testing indicates an improvement in the thermal and mechanical properties of PLA mats plasticized with OTOA.

However, the interaction of OTOA (5%) with PLA polymer chains leads to a deterioration in the morphological and mechanical properties of the fibrous material due to the difficulty in the segmental movement of the ends of the PLA polymer, the plasticizing effect of OTOA weakens.

The developed modified material PLA + OTOA has optimal physicochemical properties at an additive content of 3%.

Such a material can be used in various biomedical applications as a pioneering nonwoven material with pronounced antibacterial activity, for drug delivery, and in tissue engineering, since the plasticizing effect of OTOA leads to a noticeable improvement in the morphology of electrospun materials, their mechanical properties, and an improvement in sorption capacity. The pronounced antimicrobial activity of OTOA [68, 69] suggests its possible use as a functional antibacterial additive.

1.6 Microencapsulation of ozonated oils

Another method of incorporating an active agent into a fibrous biodegradable polymer matrix is the use of encapsulated ozone-generating antimicrobial agents. In the course of numerous studies, microcapsules of ozonized active agents (oils) with antimicrobial activity have been developed and successfully applied for the manufacture of nonwoven materials for medical purposes. Encapsulation is defined as the process by which bioactive oil droplets are coated or embedded in a homogeneous or heterogeneous matrix to form small capsules with many beneficial properties [64, 70, 71]. Encapsulation of oils is an effective approach to improve their stability, non-volatility, and environmental protection. The design goal of any bioactive textile is to prevent infections in the event of injury, promote healing, and improve health. Ozonated oil capsules are prepared and encapsulated by a coacervation method using GE and GA (GE (from porcine skin, type A) and GA (from the acacia tree)) as the wall material. Typically, both the oil and the microcapsules are tested for antimicrobial activity.

Microencapsulation of ozonized red pepper seed oil has been proposed by Özyildiz et al. [30] with application in non-woven fabric for the production of antimicrobial textile material. The ozonated oil was microencapsulated by coacervation using gelatin and gum arabic and materials in the presence of a surfactant. Particle batches with a particle size of 19–37 μm and an oil content of 47–56% were obtained. Antimicrobial activity against E. coli, Pseudomonas aeruginosa, MRSA, Candida. albicans, and vancomycin-resistant Enterococcus faecium showed that the encapsulated ozonated oil retained its efficacy in microcapsule form. It has been established that tissues impregnated with active microcapsules are also very active against antibiotic-resistant test microorganisms. The observed sustained activity is extremely important for the production of functional medical textiles with antimicrobial and wound healing properties.

Such materials are actively studied in the literature (Besen et al.) [72]. For example, St. John’s wort oil and linseed oil were ozonized and then encapsulated by a simple coacervation method. Ozonated oils consistently show high antibacterial activity due to the presence of ozonide structures. The same idea was tried to apply an antibacterial finish to cotton fabrics using the incorporation of ozonated oils into cyclodextrin complexes by Beşen et al. [73]. These complexes provide the molecules with increased solubility and physical-chemical stability. From the results of the TGA evaluation, the authors observed that the thermal stability increased when the ozonated oil was isolated in the inclusion complex. The unpleasant smell of ozonized oil has completely disappeared.

The products of vegetable oils oxidation with ozone in appropriate formulations can be used for the prevention and treatment of local chronic infections. Ozone therapy can be used as an alternative to local antimicrobial agents. The widespread use of topical agents such as mupirocin and fusidic acid has already led to the emergence of bacterial resistance, predominantly in staphylococci [73].

Also, quite an urgent problem is the sterilization of polymeric materials and products before packaging or use. This is particularly important for medical devices and materials and food packaging. During treatment with ozone, the chemical structure of the polymer material in the surface layers usually changes. Oxygen-containing groups are formed, and as a result, the material’s hydrophilicity increases. Longer treatment with ozone results to the destruction of macromolecular chains in the surface layers of the polymer.

1.7 Ozone surface treatment of nonwoven fabrics

Another widely used surface modification strategy is the introduction of reactive groups onto the surface of the nanofiber mat through plasma treatment or special chemical reactions such as with ozone. One of the widely used methods for the introduction of active groups on the surface of nanofibers is the surface treatment of materials in plasma. During processing, polar groups such as -COOH and -OH can form on the surface of polymeric materials. Their concentration depends on the conditions and duration of treatment. For example, by using plasma, the properties of PCL nanofibers, its hydrophilicity and increased bio-efficiency, have been improved [74, 75].

Further, other compounds can be grafted onto the active groups obtained as a result of processing: small molecules or large molecules of medicinal substances [76]. For example, radical polymerization has been initiated through functional groups on the surface of nanofibers, leading to the production of heat-sensitive and solvent-resistant nanofibers. Another methodological approach is the direct treatment of nonwoven fibrous materials with ozone to form a bactericidal ozonolysis product. It has been established that the functional groups formed as a result of the reaction are predominantly uniformly distributed over the polymer surface. However, due to gaseous diffusion, ozone reacts not only on the surface of the polymer, but also penetrates into its volume through its imperfections or through the amorphous region of materials.

In [33], the effect of ozone on the supramolecular structure of PHB fibers produced by electrospinning revealed a change in tensile strength as a result of the duration of ozonolysis. At the initial stage of ozonation, a significant increase in tensile strength was found. The highest value was reached by the 7th minute of ozone treatment. Gaseous ozone is a strong oxidant that can significantly affect the morphology of polymers, the structure of macromolecules, and crystallinity [77, 78]. Treatment with ozone has a number of advantages over, for example, oxygen treatment. Thus, in a short period of contact with a polymer material, significant results can be achieved in terms of sterilization of its surface. However, the effect of ozone on the structural and dynamic characteristics of polymers used in packaging and medical materials is different and requires extensive study. Often, under improperly selected conditions for ozone treatment of polymer fibers, the destruction of the polymer chain is observed, which leads to a decrease in the average molecular weight and an increase in segment mobility.

During ozonation, a primary increase in the degree of crystallinity is observed, which is apparently associated with the strengthening of intercrystalline polymer molecules in the amorphous PHB phase. The oxidative process starts from the surface of the material, namely, from the oxidation of the side groups.

It is known from the literature [79] that deep oxidation of a material results in “chemical relaxation” of the most rigid macromolecules in the amorphous polymer phase. The relaxation mechanism proceeds at a faster rate [80, 81]. Further ozonation leads to orientation of PHB chains and an increase in the crystallinity of the material [82]. After that, the PHB chains are partially destroyed. The process stops completely after 10 min of ozonation, and gradual degradation was observed (Figure 5).

Figure 5.

PHB maximum strength versus ozonation time in min(a), crystallinity degree versus ozonation time in min (b).

As can be seen from the above studies, the ozonation of fibrous materials based on PHB leads to the ordering of the supramolecular structure, which has a beneficial effect on the complex of physicomechanical properties. Simultaneously with this, ozone can diffuse into the bulk of the fiber and interact with polymer chains in interfibrillar amorphous regions to form both ozonides and active radicals. In this regard, the question arises: will the non-woven fibrous biopolymer material have bactericidal properties after ozonation and how long will this effect last? There is no answer to this question yet. There are no studies in this area in the literature. However, if it is possible to experimentally establish the presence and duration of the bactericidal effect after ozonation of the material, this would open up the possibility of creating antibacterial packaging, disposable polymeric tableware, and medical items, without adding antibacterial substances to their composition.

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2. Conclusion

On the basis of this review of state-of-the art scientific research, it can be concluded that the study of ozone compounds and the process of ozonolysis of biopolymer materials is promising for various biopolymer applications. Ozone not only has a beneficial effect on the human’s physiological functions, but is also one of the most promising antibacterial agents. Surface properties of the biopolymer materials could change under the influence of ozone. During deep ozonolysis of biopolymer films and fibers, changes also occur in their supramolecular structure, which is reflected in the number physical and mechanical parameters, such as hydrophilicity, smoothness, elasticity, strength, antimicrobial activity. Recent works related to the ozonolysis of vegetable oils and application of the resulting ozonides as antibacterial functional additives in the polymer films and ultrathin fibers are also of particular attention and interest. These materials have good physical and mechanical properties and high antibacterial activity. Biopolymer materials containing ozonides could be widely used in the treatment of infectious (bacterial and viral) diseases, traumatology, orthopedics, cosmetology, and hygiene.

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Conflict of interest

The authors declare no conflict of interest.

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Written By

Olga Alexeeva, Valentina Siracusa, Marina L. Konstantinova, Anatoliy A. Olkhov, Alexey L. Iordanskii and Alexandr A. Berlin

Submitted: 27 June 2022 Reviewed: 30 August 2022 Published: 15 November 2022