Method of preparing conductive materials with polypyrrole covalently bound by dialdehyde polysaccharides

Abstract

The method involves an environmentally friendly process that uses spontaneous aldol condensation between the aldehyde groups of dialdehyde polysaccharides (DAP) and pyrrole to prepare pyrrole-decorated DAP. This is further used to prepare conductive co-oligomers and copolymers of DAP and pyrrole, formed without the addition of an oxidizing agent by connecting the bound pyrrole cycles at higher temperatures into longer chains by —CH— bridges originating from the aldehyde groups of DAP. The DAP, pyrrole-decorated DAP, and the corresponding co¬ oligomers and copolymers of DAP and pyrrole can be further used to prepare conductive covalently cross-linked hydrogels, covalently bind PPy prepared by other methods, and for the creation of composites suitable especially for biomedical applications.

Description

[0001] METHOD OF PREPARING CONDUCTIVE MATERIALS WITH POLYPYRROLE COVALENTLY BOUND BY DIALDEHYDE POLYSACCHARIDES

[0002] Field of Invention

[0003] The invention relates to a method of preparing conductive co-oligomers, copolymers, composites, and conductive hydrogels based on polypyrrole (PPy) and dialdehyde polysaccharides (DAP) with expected applications in sensors, biomedicine, power industry, and wearable electronics. The basis of the invention is the use of spontaneous formation of covalent bonds between DAP and pyrrole or PPy as a result of a condensation reaction between pyrrole cycles and aldehyde groups of DAP.

[0004] This method allows a) direct decoration of DAP with pyrrole cycles without the need for prior modification of pyrrole or the use of other toxic organic agents and solvents, which are necessary for existing solutions, b) preparation of conductive co-oligomers and copolymers of pyrrole and DAP by increasing the temperature, without the addition of an oxidizing agent or the use of another polymerization method otherwise necessary for the preparation of PPy copolymers, because the poly aldehyde character and structure of DAP function as a template allowing the linking of bound pyrrole cycles by —CH— bridges into higher units, which can be used for the preparation of conductive colloidal particles and conductive fibrous materials, c) incorporation of pyrrole cycles covalently bound to DAP into PPy chains formed during in situ polymerization and subsequent formation of covalently bound conductive composites of DAP and PPy, without the need for the addition of organic agents, linkers, and toxic reactants, in which case the PPy preferentially grow on the oxidized matrix and resistance of the PPy layer to wear is increased compared to matrices not containing DAP, d) preparation of conductive composite materials by anchoring pre-made PPy particles into matrices using a reaction with DAP, e) simultaneously with points a) to d) to use the ability of DAP to react with natural or synthetic hydrophilic polymers carrying -OH, -NH2, or -NH groups such as cellulose, chitosan, polyvinyl alcohol, polyurethane or polyamide, which can be dissolved or undissolved in the form of various hierarchical structures, namely fabrics, fibers or nanofibers, in which case DAP can also serve as a crosslinking agent forming hemiacetal or imine bonds with these polymers, as well as for binding of pyrrole cycles and the associated formation of copolymers or composites with covalently anchored PPy.

[0005] Description of the Prior Art

[0006] Polypyrrole (PPy) is considered one of the most promising conductive polymers with a range of potential industrial uses in the field of sensors, wearable electronics, battery electrodes, and desalination of water, but also in medicine and biology as wound healing material or for preparation of conductive cellular scaffolds. The reason for the popularity of PPy is the ease of its preparation, good stability, low toxicity, and especially high electrical conductivity. The main disadvantages of PPy include its very low solubility in most solvents and limited processability. PPy is usually prepared by electropolymerization or chemical oxidative polymerization using various oxidizing agents, such as FeCh, in the form of thin layers or powder. While electropolymerized thin layers usually have high conductivity and purity, their use is limited by the mechanical properties of pure PPy and its weak interaction with the substrate, which leads to easy cracking or peeling of the PPy layer and reduction of conductivity. The limited size of electrodes usable for electropolymerization also prevents greater industrial applications of this technique.

[0007] Chemical polymerization of pyrrole using various oxidizing agents is a difficult-to-control radical-involving process occurring in an acidic environment. When oxidizing a solution of pyrrole, nucleation of PPy particles occurs by random connection of monomers and oligomers of pyrrole throughout the volume of the solution. The resulting particles usually have a very wide size distribution, and therefore a high polydispersity index (PDI), which can affect their further properties and use. The conductivity of thus prepared PPy powder is given by the amount and extent of contacts between particles and is orders of magnitude lower than that of a homogeneous layer of PPy film deposited on an electrode.

[0008] To expand the application potential, PPy is usually prepared in the form of composites with other materials. The simplest methods of preparing composites are the dispersion of pre- prepared PPy powder into a polymer matrix or the initiation of in situ polymerization of pyrrole directly in the matrix. Both often lead to the formation of a material with inhomogeneous properties, especially due to the different sizes and distribution of PPy particles. The electrical conductivity of such a composite is also significantly lower than that of a homogeneous layer of PPy due to the limited number of interactions between individual conductive particles of PPy. In addition, there may be a gradual leaching or migration of PPy particles from the matrix, resulting in a deterioration of the composite properties. This is particularly problematic in the case of biomedical applications of PPy composites, where released particles can penetrate into the organism and cause undesirable reactions.

[0009] Another possible method of preparing composites is in situ polymerization of pyrrole in the presence of a suitable matrix, which can be, for example, a hierarchically arranged insoluble polymer. If this polymer is capable of swelling, it can be impregnated by a solution of pyrrole, and the growth of PPy grains on its surface is initiated by the addition of an oxidizing agent. Part of the grains of PPy formed in the solution can also be adsorbed onto the surface of the matrix due to weak bonding interactions. If the amount of pyrrole in the reaction mixture is sufficient, the growing grains of PPy can in both cases create a continuous layer on the surface of the matrix. The disadvantage of this method is the absence of strong, preferably covalent, interactions between the deposited layer of PPy and the matrix. In such a case, the PPy layer is bound to the surface only by weak interactions such as hydrogen bridges and Van der Waals forces. This leads to easy detachment of the PPy layer from the matrix and so-called flaking, i.e., peeling of the PPy layer from the matrix under mechanical stress, especially when using a hydrophilic matrix that is only weakly interacting with hydrophobic PPy, see Chinese patent CN107630390A.

[0010] At present, two possible solutions are used to increase the adhesion of the PPy layer to the matrix: a) using electrostatic interaction between the negatively charged matrix and the positively charged PPy, which is described, for example, in US patent US8764938 or Chinese patents CN107630390A, and CN113480774A; b) covalent binding of pyrrole derivatives to the matrix and subsequent in situ polymerization, during which the bound derivatives are incorporated into the PPy layer, which is thus anchored to the surface of the matrix, see Chinese patent CN109880127A, or DOI: 10.1186 / s40824-016-0078-y. Method a) is generally more common, as matrices often contain negatively charged groups either directly or can be relatively easily modified for this purpose, for example by oxidation or binding of suitable compounds carrying a negative charge. For example, in the case of cellulose, this can be achieved by the oxidation of hydroxyl groups to carboxyl groups, see Chinese patent CN111725489A or Japanese patent JP2012219380A. The advantage of this solution is that negatively charged and acidic groups can dope PPy and thus increase and maintain its conductivity. However, such modification of the matrix is not always possible or desirable, and electrostatic interactions may be weakened in a polar environment with high ionic strength.

[0011] The advantage of method b) is the formation of strong and stable covalent bonds between the matrix and PPy during in situ polymerization. This is used, for example, to create hydrogels crosslinked with PPy, see Taiwan patent TW201120104A and Chinese patent CN115246940A. The disadvantage of current solutions is the need to use derivatives of pyrrole modified with various functional groups necessary for binding to a given matrix, or the need to modify the matrix with suitable linkers capable of binding pyrrole, such as aziridine, see Chinese patent CN109880127A. These modifications are then often limited to a specific functional group of the matrix, to which the derivative of pyrrole or linker can be bound. For example, for covalent binding of PPy to hyaluronic acid (see YANG, Jongcheol. Biomaterials Research. 2016, 20), it is necessary to first reduce l-(cyanoethyl)pyrrole to N-(aminopropyl)pyrrole using LiAIHg in diethyl ether. This molecule is then conjugated to the carboxyl group of hyaluronic acid using carbodiimide. Only then is in situ polymerization initiated and PPy is formed. The need to use complex procedures and toxic chemicals to prepare covalently bound PPy composites not only increases the cost of syntheses but has an especially significant impact on the environment and limits the use of the resulting composites in the field of biomedicine due to the release of potentially risky residues.

[0012] Summary of the Invention

[0013] The essence of the invention lies in an environmentally friendly method using spontaneous aldol condensation between aldehyde groups of polysaccharide dialdehydes (DAP) and pyrrole to prepare pyrrole-decorated DAP, conductive co-oligomers, and copolymers of DAP and pyrrole forming at a higher temperature without the addition of an oxidizing agent by linking of bound pyrrole cycles into higher units via —CH— bridges originating from aldehyde groups of DAP, whereby DAP, DAP decorated with pyrrole, and the respective co-oligomers and copolymers of DAP and pyrrole can be further used for the preparation of conductive covalently crosslinked hydrogels, covalent binding of PPy prepared by other methods, and for the formation of composites suitable especially for biomedical applications.

[0014] In the first phase of the method according to the invention, DAP is prepared. Any polysaccharide composed of pyranose cycles carrying at least one vicinal diol in its structure, which can be oxidized using periodate, typically cellulose, alginate, dextran, hyaluronic acid, dextrin, starch, amylose, pectin, schizophyllan, scleroglucan or xanthan, can be used for the preparation of DAP. When such a polysaccharide is oxidized by Nal04, two aldehyde groups are formed in each unit originally carrying a vicinal diol. The resulting DAP is in an aqueous environment present in the form of a geminal diol, see Fig. la. Each oxidized unit in the DAP chain thus carries a pair of reactive aldehyde groups. Hence, DAP can be referred to as oligo or poly aldehyde depending on the number of oxidized units and the length of its chain. By reducing the amount of NalO4 used, the degree of oxidation of the material can be controlled. The degree of oxidation can preferably range between 10 - 100%. A lower degree of oxidation can be used for surface modification of insoluble polysaccharides, preferably cellulose. On the other hand, fully oxidized DAPs are usually well soluble in water or can be solubilized according to known procedures and thus can be used for the formation of colloidal particles, for impregnation or surface modification of other materials, or as crosslinking agents for hydrogels.

[0015] In the next phase of the method according to the invention, DAP is used for the preparation of conductive co-oligomers and copolymers of pyrrole and conductive composites or conductive hydrogels based on them: a) Decoration of DAP with pyrrole and preparation of conductive co-oligomers and copolymers of DAP and pyrrole aa) Decoration of DAP with pyrrole: After exposing DAP to an aqueous solution of pyrrole, both readily react already at 20 °C in an acidic environment of pH 3 - 6.5. The reaction consists of the substitution of hydrogen atoms in the a (2 and 5) position of the pyrrole cycle and the formation of a covalent bond between pyrrole and the aldehyde group of DAP (see Fig. lb). Each aldehyde group can bind up to two pyrrole cycles, which are interconnected by a -CH- bridge originating from former aldehyde group. The product of DAP and pyrrole reaction is further referred to as DAP-py. The reaction proceeds spontaneously, i.e., without catalysts, oxidizing agents, special pyrrole derivatives, or other organic reactants or solvents (see Example 1). The degree of decoration of DAP can be controlled by changing the molar ratio between pyrrole, the npy, and the aldehyde groups in DAP, the ncHo. To achieve the highest possible degree of substitution, npymust be at least in double molar excess to ncHo. Optionally, the degree of substitution can be reduced by using a lower molar ratio of reactants, thus leaving part of the aldehyde groups free for further reactions. The duration of the reaction can be between 3 and 48 hours depending on the ratio of reactants and the type of DAP. The resulting soluble DAP-py is purified by dialysis or, in the case of insoluble matrices, by filtration and washing in water or 0.2M HCI. Subsequently, DAP-py can be isolated by lyophilization, dried, or directly used for further reactions. ab) Preparation of co-oligomers and copolymers of pyrrole and DAP without an oxidizing agent: Heating of an acidic solution of pyrrole at pH 3 - 6.5 in the presence of DAP or DAP-py leads already after a few minutes to color change indicating the formation of higher co- oligomers / copolymers of pyrrole and DAP, collectively referred to as DAP-PPy, without the addition of an oxidizing agent or otherwise induced polymerization of PPy (see Example 2). The scheme of this reaction is shown in Fig. lc. The poly aldehyde character and specific structure of DAP, namely the distance and orientation of -CHO groups in DAP chains, function as a template initiating spontaneous connection of DAP-py units into larger components via -CH- bridges formed from original aldehyde groups, and thus the formation of DAP-PPy. The duration of heating can range from 2 to 72 hours depending on the type of DAP, reaction temperature, and amount of pyrrole in the mixture. The temperature of the reaction mixture preferably ranges between 50 and 75 °C, because the reaction slows down at lower temperatures, and conversely, there is a risk of DAP degradation at higher temperatures. The ratio npy: ncHo can range between 1:1 and 20:1, whereby for optimal progress of the reaction, pyrrole must be at least in double molar excess to ncHo in the reaction mixture. In the case of soluble DAP, conductive colloids of dark color are formed already after 2 hours, without the addition of an oxidizing agent or another method of inducing polymerization of pyrrole, which is otherwise a necessary step in the preparation of polymers and copolymers of pyrrole. The formation of colloids is caused by the decreasing solubility of elongating DAP-PPy chains, which gradually leads to the formation of colloidal particles in the solution. If DAP is present in the form of a suitable hierarchically arranged matrix, whereby the matrix is understood to be either polysaccharide, advantageously cellulose, whose surface is directly oxidized with periodate to DAP (see Example 3) or other natural or synthetic hydrophilic polymer carrying -OH, -NH? or -NH groups impregnated in a DAP solution with which DAP reacts to form hemiacetals or imines, forming a layer on their surface, a hierarchically arranged conductive DAP-PPy material can be prepared, once again without the addition of an oxidizing agent (see Example 4). The described method is therefore not limited to a specific matrix but can be used for a variety of different materials. b) Preparation of covalently bound composites of DAP-PPy with a hierarchical structure. For the preparation of covalently bound composites, hierarchically arranged matrices, whereby the matrix is understood to be either various polysaccharides, advantageously cellulose, whose surface is directly oxidized with periodate to DAP, or other natural or synthetic polymers of hydrophilic nature carrying -OH, -NH? or -NH groups, such as cotton, chitosan, polyurethane, polyamide, in the form of fibers or fabrics, which were impregnated in a DAP solution and with which DAP reacts to form hemiacetals or imines, leading to the modification of their surface with a DAP layer, were first exposed to an aqueous solution of the pyrrole containing 0.1 - 10 times the molar amount of pyrrole relative to the content of ncHo in the matrix for 4 - 24 hours, resulting in the formation of DAP-py. Subsequently, by adding a suitable oxidizing agent, advantageously FeCI? in 1.65 - 3 times the molar amount relative to npy, in situ polymerization of pyrrole to PPy is initiated, which runs for 16 - 24 hours. During polymerization, preferential formation of PPy on the matrix surface occurs, as a result of the incorporation of pyrrole cycles from the DAP-py or DAP-PPy into growing PPy chains, thereby leading to the covalent binding of PPy to the matrix. The scheme of the reaction is shown in Fig. Id, for examples of embodiments see Examples 3 to 6. Compared to currently used procedures, there is no need to use organic solvents, further modifications of the matrix, or special linkers to anchor the PPy layer. This procedure is also not limited by the use of a specific matrix or custom derivative of pyrrole. The presence of covalent bonds between the matrix and PPy increases the resistance of the composite, reduces the peeling of the PPy layer due to mechanical stress, and limits the washing of PPy particles from the composite, which is particularly important for biomedical applications. c) Use of DAP-py for the preparation of conductive hydrogels with dual crosslinking

[0016] Due to the ability of DAP to react with -OH groups to form hemiacetals or with -NH? groups to form imines, DAP or DAP-py can advantageously be used for simultaneous anchoring of the pyrrole and as a crosslinking agent for the preparation of hydrogels. The condition is that free aldehyde groups are still present in DAP-py, which is achieved by using a ratio of npyto ncHo lower than 2:1, preferably 0.5:1, which leaves a part of the aldehyde groups available for further reactions. DAP is then allowed to react with pyrrole at laboratory temperature for at least 3 hours and the solution is then added to a solution of a water-soluble polymer, advantageously polyvinyl alcohol, and left until it crosslinks. The prepared material is then re-immersed in a solution of pyrrole for 72 hours and in situ polymerization of pyrrole is subsequently initiated by adding an excess of an oxidizing agent, advantageously FeCh as in point b). Oxidation runs for 24 hours. During the formation of PPy chains in the hydrogel, pyrrole cycles from DAP-py are incorporated into their structure, which leads to secondary crosslinking of the hydrogel, which also becomes conductive. The resulting PPy chains are thus bound in the hydrogel both physically and chemically and there is homogeneous growth of PPy throughout the volume of the hydrogels. d) Preparation of conductive composite hydrogels

[0017] The preparation of composite conductive hydrogels consists of the addition of pre-prepared colloidal particles of PPy to a solution of a suitable polymer carrying -NH? groups, advantageously chitosan, before the addition of DAP. After adding colloidal particles of PPy to the polymer solution, preferably in an amount of 5 - 10 wt% relative to the amount of dissolved polymer, a solution of DAP is added dropwise, which initiates the crosslinking and the formation of hydrogels, as well as the reaction between aldehyde groups of DAP and terminal units of PPy chains, thus anchoring PPy particles in the hydrogel structure. For the preparation of thin hydrogel films or foils, the prepared solution is then transferred to molds and dried to constant weight, and then re-swollen in water or aqueous solution. The prepared conductive composite hydrogel exhibits the ability to accelerate wound healing at the in vitro level.

[0018] List of Drawings

[0019] To clarify the nature of the invention in greater detail, drawings are enclosed showing:

[0020] Fig. 1: a) Scheme of oxidation of polysaccharides containing vicinal diol by NalO4 and the formation of DAP and its hydrated form (geminal diol), reversibly occurring in aqueous solution; b) Scheme of an aldol condensation reaction between aldehyde groups of DAP, shown in the form of geminal diol, and pyrrole (py) leading to the formation of DAP-py, c) Scheme of co-oligomerization / copolymerization of DAP-py to DAP-PPy without the presence of an oxidizing agent due to linking of DAP-py into larger units upon heating, d) Scheme of DAP-PPy composites preparation from DAP-py and pyrrole in the presence of an oxidizing agent. All reactions take place in an acidic environment.

[0021] Fig. 2: a) FT-IR analysis of source polysaccharides and derivatives prepared by periodate oxidation (DAP); the signal at 1730 cm1corresponds to vibrations of formed carbonyl groups. b) UV-Vis analysis of prepared DAP solutions (10 mg / mL) after iodometric determination of residual oxidizing agents; the absence of iodine absorbance in the wavelength range 400 - 600 nm means that the content of residual oxidizing agents in DAP is below the detection limit of the method. c) XRF analysis of selected DAP solutions (20 mg / mL) focused on the detection of iodine-based oxidizing agents (periodate, iodate); the absence of iodine signals in characteristic areas marked with yellow spectral markers means that the content of residual oxidizing agents in DAP is below the detection limit of the method.

[0022] Fig. 3: a)1H NMR spectrum of DAC-py (D?O, 298 K) with detail of bound pyrrole signals, where a denotes H2 / H5 and (3 H3 / H4 signals of bound pyrrole cycles. b) FT-IR spectra of DAC, pyrrole (py), and DAC-py with marked selected vibrational bands. c)1H NMR spectra of the reaction of DAAL with pyrrole performed directly in the NMR tube (D?O); immediately after mixing (0 h, main spectrum); spectrum showing decrease in intensity of the a pyrrole signal after 8 h at 25 °C (inserted spectrum marked 8 h@ 25°C); spectra showing decrease in intensities of both pyrrole signals during heating to 50 °C for 8 h (inserted spectra marked 8 h@50 °C) as a result of the formation of an insoluble DAAL-PPy colloid visible on the inserted detail of the NMR tube after measurement. d)1H NMR spectra of the reaction of DAH with pyrrole performed directly in the NMR tube (D2O) immediately after mixing (0 h), and spectra showing the subsequent decrease in intensity of pyrrole signals during 8 h at 50 °C (inserted spectra marked 8 h@50 °C) as a result of the formation of an insoluble colloid of DAH-PPy visible on the inserted detail of the NMR tube after measurement.

[0023] Fig. 4: a) UV-Vis spectra of a reference sample containing only a solution of pyrrole at pH 3 measured after 30, 60, and 120 min; the inserted photograph shows the formation of colored solutions in the presence of DAP already after 15 min of heating at 50 °C in comparison with the reference sample (py). b) to e) UV-Vis spectra documenting the formation of DAP-PPy measured after 30, 60, and 120 min in a mixture of pyrrole with b) DAC, c) DAAL, d) DADXA and e) DAH at pH 3. Some of the samples were diluted 2 - 10x due to strong absorption, which is indicated in the individual graphs. Ox in the case of pyrrole indicates that the sample was not diluted. f) Photographs of prepared samples after 24 h from the start of the reaction in a thin layer.

[0024] Fig. 5: FT-IR spectra and photographs of bodies of pure PPy prepared by oxidation of pyrrole with FeCh in UPW and of DAP-PPy prepared without the addition of an oxidizing agent (column 1), their SEM (column 2) and TEM (column 3).

[0025] Fig. 6: Row a) Photographs of suspensions of CNF and CNF-DAC in a solution of pyrrole after 4 h of heating at 75 °C without an oxidizing agent, SEM analysis of CNF, CNF-DAC and CNF-DAC-PPy. Row b) SEM analysis of CNF-DAC / IPPy to CNF-DAC / 8PPy. Row c) SEM analysis of CNF / 2PPy, CNF-DAC / 2PPy, CNF / 8PPy, and CNF-DAC / 8PPy after 30 min of sonication, documenting damage to the PPy layer in samples of the CNF / PPy series; Petri dishes showing samples after sonication for comparison of fragmentation.

[0026] Row d) TGA analysis of pure PPy prepared by oxidation of pyrrole with FeCh, CNF / 2PPy, and CNF- DAC / 2PPy.

[0027] Fig. 7: Row a) SEM analysis of DAC-PPy formed on the surface of textiles impregnated with DAC at various magnifications and inserted photograph of fabric with DAC-PPy after reaction.

[0028] Row b) SEM analysis and photographs of B / 2PPy and B / 8PPy composites of PPy and cotton fabric prepared without impregnation with DAC.

[0029] Row c) SEM analysis and photographs of DAC / 2PPy and DAC / 8PPy composites of PPy and cotton fabric prepared by impregnation in a solution of DAC.

[0030] Row d) SEM analysis and photographs of DAAL / 2PPy and DAAL / 8PPy composites of PPy and cotton fabric prepared by impregnation in a solution of DAAL.

[0031] Fig. 8: Photographs of CHIT-DAC_PPy samples after 15, 30, and 240 minutes from the addition of the oxidizing agent and comparison with the reference sample CHIT_PPy, which is analogous to CHIT-DAC_PPy200, but without impregnation by DAC. The numbers indicate the molar ratio of pyrrole to bound DAC in percentages.

[0032] Fig. 9: SEM analysis of CHIT-DAC_PPyO to CHIT-DAC_PPyl000 samples compared to pure CHIT nanofibers and a reference sample CHIT_PPy, which was not impregnated with DAC.

[0033] Fig. 10: FT-IR spectra of CHIT-DAC_PPyO to CHIT-DAC_PPyl000 samples along with CHIT, CHIT- DAC, pure PPy prepared by oxidizing pyrrole with FeCh, and a reference sample CHIT_PPy prepared without DAC impregnation.

[0034] Fig. 11: Photographs of CHIT-DAP_PPy samples after 15, 30, and 240 minutes since the addition of the oxidizing agent and their FT-IR spectra. Fig. 12: SEM analysis of prepared CHIT-DAP_PPy samples.

[0035] Fig. 13: a - d) FT-IR spectra of nanofibers from PA and PU, and their composites PA-DAC_PPy200 and PU-DAC_PPy200, photographs of reaction mixtures after 4 hours. The bottom part of the figure: SEM photographs of PA and PU nanofibers along with their DAC-PPy200 composites at various magnifications.

[0036] Fig. 14: a) FT-IR spectra of pure PVA and PVA / DAC xerogels (dried hydrogels) with bound pyrrole, b) FT-IR spectra of PVA / DAC_PPy cryogels with a demonstration of hydrogel flexibility. The bottom part of the figure: SEM analysis of brittle fractures of PVA / DACl_PPy, PVA / DAC3_PPy, and PVA / DAC5_PPy samples.

[0037] Fig. 15: Rheological properties of PVA / DAC3_py hydrogels (without oxidation by FeCh, empty marks) and PVA / DACl_PPy to PVA / DACl_PPy hydrogels (after oxidation by FeCh, full marks).

[0038] Fig. 16: a) Photographs of prepared composite hydrogel films and SEM images of their surface with visible PPy particles, b) Raman spectrum of DAC, PPy colloid (PPy), and their mixture (PPy+DAC) in a ratio of 1:10 after 24 hours of reaction, c) Graph of remaining wound area expressing healing speed of the scratch in a cell monolayer (mouse embryonic fibroblasts NIH / 3T3) without the presence of hydrogels (REF), in the presence of CHIT-DAC, CHIT-DAC / PPy5% and CHIT-DAC / PPylO% hydrogels (less is better). c) Images of injury in the cell layer immediately after its creation (0 h) and its healing after 10 h without (REF) and in the presence of CHIT-DAC / PPy5% hydrogel. Preferred embodiments of the invention

[0039] Example 1: Decoration of DAP with pyrrole, proof of the formation of a covalent bond in DAP-py

[0040] To achieve quantitative oxidation, 2,3-dialdehyde cellulose (DAC), 2,3-dialdehyde hyaluronate (DAH), 2,3-dialdehyde alginate (DAAL), and dialdehyde dextran (DADXA) were prepared by oxidizing 1 g of cellulose, hyaluronic acid, sodium alginate, or dextran using sodium periodate (NalO4) in an amount corresponding to 1.2 times the molar amount of vicinal -OH groups of a given polysaccharide (npoiysach) - for periodate weighings see Table 1. These polysaccharides represent both homopolysaccharides with a and (3-glycosidic bonds (dextran, cellulose), as well as acidic homo- and heteropolysaccharides of various compositions (alginate, hyaluronic acid). It can therefore be reasonably assumed that similar polysaccharides of these types can also be oxidized and subsequently used for reactions with pyrrole.

[0041] Table 1: Weight and concentration of the oxidizing agent NalO4 relative to l g of the source polysaccharide used to prepare polysaccharide derivatives.

[0042] Cellulose oxidation was carried out for 72 hours at laboratory temperature in the dark. After the oxidation, the suspension of DAC particles in the reaction mixture was purified using 5 cycles of repeated centrifugation (5 x 15 min at 10,000 RPM, volume V - 800 mL) and mechanical homogenization (10 min at 1,000 RPM). Thus purified suspension of insoluble DAC was heated to 80 °C under reflux for 2 hours. This resulted in the solubilization of DAC, i.e., the conversion of DAC from suspension to a clear solution. This solution was centrifuged at 10,000 RPM for 15 min and filtered to remove residual insoluble DAC. The solution was dialyzed for 72 hours against ultra-pure water (UPW), then for 48 hours against 0.05 M NaCI to completely remove residual periodate / iodate salts, and then against UPW (24 h) for desalination, using a membrane with a molecular weight cut-off (MWCO) of 14 kDa. The purified DAC solution was again filtered (0.45 pm filter) and lyophilized. Oxidation of soluble polysaccharides, i.e., hyaluronic acid, alginate, and dextran, took place over 24 hours, after which these were transferred to dialysis membranes with MWCO - 14 kDa and dialyzed in the same way as for DAC, i.e., 72 h against UPW, 48 h against 0.05 M NaCI, and again 24 h against UPW, followed by filtration (0.45 pm), and lyophilization. The result of the preparation process is DAP of high purity in the form of soluble lyophilizates. Fully oxidized DAPs contain the following amounts of carbonyl groups: DAC - 12.5 mmol / g, DADXA - 12.3 mmol / g, DAH - 5.0 mmol / g, DAAL - 10.2 mmol / g.

[0043] The source polysaccharides and prepared DAP were subsequently characterized using FT- IR spectroscopy (Nicolet 6700 FT-IR spectrometer, Thermo Fisher Scientific, USA), where the presence of aldehyde groups was confirmed, see Fig. 2a. The removal of all residual oxidizing agents, which could otherwise cause oxidation of pyrrole to PPy, was confirmed in two ways. First by iodometric titration on starch in combination with UV-Vis spectroscopy (Lambda 1050 spectrometer, PerkinElmer, USA) and also by X-ray fluorescence spectroscopy (ARL Quant'X EDXRF Analyzer, Thermo Scientific, USA) calibrated on aqueous solutions of potassium iodide of known concentrations, see Fig. 2. No periodate or iodate salts, which could cause oxidation of pyrrole, were detected in any of the substances.

[0044] Thus prepared and purified DAPs were then used to prepare DAP-py and DAP-PPy. To prove the aldol condensation between DAP and pyrrole, 25 mg of DAC containing 0.3125 mmol - CHO groups was initially dissolved in 5 mL of UPW. Then, 21 pL of pyrrole corresponding to npy: ncHo ratio 1:1 was added. The reaction ran at laboratory temperature (20 °C) and under constant stirring for 24 hours in the dark. The pH of the reaction mixture was 6.5 and was not further adjusted. Subsequently, unreacted pyrrole was removed by dialysis (5 days against UPW, MWCO 3.5 kDa) and DAC-py was isolated by lyophilization. DAC-py was dissolved in D?O (cone. 15 mg / mL) and a1H NMR spectrum was measured (JEOL 400 MHz, 298K), see Fig. 3a. In the spectrum, signals of bound pyrrole at 6.8 ppm (H2, H5 of the pyrrole cycle, further referred to as a) and between 6.0 - 6.25 ppm (H3, H4 of the pyrrole cycle, further referred to as (3) are clearly visible. The mere presence of these signals is proof of the reaction between DAC and py, as all free pyrrole was removed by dialysis. While in free pyrrole the signals a and P have the same intensity, there should be a reduction in the intensity of the signal a relative to P in DAP-py due to the elimination of hydrogens in positions H2 or H5. If each pyrrole cycle was bound only to one -CHO group, the ratio of intensities of signals a and P should be 1: 2, and the signal a should thus reach 50% of the intensity of the signal P, see Fig. lb. However, the intensity of the signal a in the DAP-py spectrum only reaches 37% of the intensity of the signal P, which is not only proof of the elimination of hydrogen atoms in positions H2 / H5 of the pyrrole cycle due to the condensation reaction with DAC, but also indicates the limited formation of lower co-oligomers of DAP-PPy already at laboratory temperature, see Fig. lc. In other words, some of the pyrrole cycles are bound to DAC in both position 2 and 5. Different chemical environments of pyrrole cycles also cause the splitting of the signal P into three separate signals. The formation of DAC-py is further substantiated by the emergence of a new vibrational band at 1663 cm1in the IR spectrum in Fig. 3b, while the band of carbonyl groups of DAC at 1730 cm1and bands of C=C vibrations of pyrrole at 1533 cm1and 1412 cm1are suppressed or shifted. To confirm that the mentioned reaction is not limited to DAC, a reaction of 10 mg of DAAL dissolved in 0.5 mL of D?O with 6.7 pL of pyrrole, which corresponds to npy: ncHo ratio 1: 1, was performed directly in the NMR tube, see Fig. 3c. After 8 h at 25 °C, the intensity of the signal a at 7.08 ppm decreased by 25% relative to the signal P at 6.4 ppm due to the aldol condensation between the carbonyl groups of DAAL and pyrrole. Subsequent heating of this reaction mixture and the preparation of DAP-PPy, is discussed in Example 2.

[0045] Example 2: Preparation of conductive colloidal particles of DAP-PPy without added oxidizing agent To exclude possible contamination of reaction mixtures by residual oxidizing agents, all reactions were carried out using DAP purified according to Example 1, ultra-pure water (UPW), new and unused reaction vessels and cuvettes washed with UPW, freshly opened chemicals of p.a. purity, and without the addition of an oxidizing agent. The formation of DAP-PPy was monitored using1H NMR for the reaction between pyrrole and DAAL or DAH, prepared according to example 1, directly in the NMR tube, see Fig. 3c, d. 6.7 pL of pyrrole was added to 10 mg of DAAL or DAH dissolved in 0.5 mL of D?O in both cases, which corresponds to a molar ratio of npy: ncHO 1:1 for DAAL (content of — CHO groups 10.2 mmol / g) and 2:1 for DAH (content of — CHO groups 5 mmol / g). The pH of the reaction mixtures was close to 5 due to the presence of acidic groups on both DAPs and was not further adjusted. The tube with DAAL and pyrrole was first left for 8 h at laboratory temperature, resulting in the formation of DAAL-py evidenced by a decrease in the intensity of the a signal, see Example 1 and Fig. 3c. The NMR tube was then heated in the NMR spectrometer to 50 °C,1H NMR spectra were measured every 15 min, and the decrease in intensity of both pyrrole signals due to the formation of colloidal particles of DAAL-PPy was monitored. After 8 h, signals of free pyrrole almost disappeared and a darkly colored colloidal solution was formed, see the photograph of the NMR tube in Fig. 3c. This experiment demonstrates the possibility of using pyrrole-decorated DAAL-py for the preparation of DAAL- PPy. In the case of DAH, the NMR tube was heated to 50 °C immediately after the addition of pyrrole and the decrease in intensity of its signals was monitored for 8 h, again using NMR spectra measured every 15 min, see Fig. 3d. During this time, the intensity of both signals decreased, with the intensity of the a signal decreasing faster and being 25% lower after 8 compared to the (3 signal. This is consistent with the formation of DAH-py by aldol condensation and the gradual transition of DAP-py to insoluble DAH-PPy, which precipitates from the solution and is therefore not visible in NMR spectra. Its presence is however obvious from the typical dark coloration of the solution - see the photograph of the NMR tube after the experiment in Fig. 3d.

[0046] Subsequently, aqueous solutions with a concentration of 5 mg / mL were prepared from DAPs prepared in Example 1, i.e., DAC, DAH, DAAL, and DADXA, and a molar excess of pyrrole was added so that the final concentration of pyrrole in the solution was 0.5 M (total volume 12 mL). Considering the different amounts of aldehyde groups in DAPs, see Example 1, this corresponds to a range of molar ratios npy: ncHO between 8:1 for DAC and 20:1 for DAH. Immediately after the addition of pyrrole, the pH of the reaction mixtures was set to 3.0 (1 M HCI) for all samples. An equally acidified 0.5 M solution of pyrrole without DAP served as a reference sample. The reaction mixtures were then placed in a water bath heated to 50 °C and stirred in the dark for 48 h. Just a few minutes after heating, all samples changed color, which is observable with the naked eye, see Fig. 4a, and is also documented by UV-Vis spectra, which were measured after 30, 60, and 120 min from the start of the reaction, see Fig. 4. The fastest reaction was recorded for DADXA and DAC, which formed green-colored solutions already after a few minutes of heating. A somewhat slower reaction, associated with the formation of purple-blue to black solutions, occurred for DAH and DAAL. The color difference is likely caused by the presence of an acidic carboxyl group in DAH and DAAL. Approximately after two hours, the first colloidal particles begin to appear in DAC-PPy, which is associated with a decrease in the intensity of signals in UV-Vis spectra measured after 120 min compared to those measured after 60 min, see Fig. 4b. After 24 h, the formation of particles in all solutions is apparent, with exception of the neat pyrrole solution which remained clear, see Fig. 4f. The formation of DAP-PPy colloidal solutions is thus clearly associated with the presence of DAP, without which it does not proceed. After 48 h, the samples were cooled to laboratory temperature and dialyzed against 0.2 M HCI for 5 days.

[0047] The prepared DAC-PPy, DAH-PPy, DAAL-PPy, and DADXA-PPy were then lyophilized and further characterized using FT-IR, SEM, and TEM, see Fig. 5. For comparison, spectra, and photographs of PPy prepared by oxidation of pyrrole with a 1.2x molar excess of FeCH in UPW for 24 h are also shown in Fig. 5. All DAP-PPy contained spontaneously formed colloidal particles of typical black color with dimensions between tens (DAH-PPy, DAAL-PPy, and DADXA-PPy) and several hundred nanometers (DAC), which is significantly less than for PPy prepared without DAP by oxidation with FeCh. Lyophilizates of DAC-PPy, DAH-PPy, DAAL-PPy, and DADXA-PPy were then pressed into cylindrical bodies with a diameter of 15 mm intended for conductivity measurement. The conductivity of the samples was measured using a programmable electrometer Keihley 6517B and the samples were pressed between two electrodes. Subsequently, the conductivity was calculated according to equation 1 from the dependence of current on voltage in its linear part (0-10 V), taking into account the thickness (t) and also the area of the samples (S), which was in contact with the electrodes.

[0048] 1 1 a = — us ( '1) '

[0049] The conductivities of individual samples were 0.0024 nS / cm (DAC-PPy), 0.0068 nS / cm (DADXA-PPy), 0.057 nS / cm (DAAL-PPy), and 0.2 nS / cm (DAH-PPy). All DAP-PPy thus exhibited electrical conductivity, even though no oxidizing agent was used for their preparation, and the conductivity of samples prepared using acidic polysaccharides is one to two orders of magnitude higher than those of non-acidic polysaccharides

[0050] Example 3: Preparation of conductive copolymers and composites of PPy using oxidized cellulose nanofibers

[0051] A suspension of cellulose nanofibers (CNF, Cellulose lab, Canada) with a concentration of 0.5 wt% in water was oxidized from 10% to DAC using the addition of NalC>4 in an amount of 0.165 g per 1 g of CNF for 72 hours at 30 °C. The reaction was then stopped by adding ethylene glycol and the suspension was dialyzed for 72 hours against UPW. The prepared CNF-DAC samples were used without further modifications for the synthesis of composites with PPy prepared by in situ polymerization, further referred to as CNF-DAC / PPy. For the preparation of copolymers on the surface of CNF-DAC without the use of an oxidizing agent, i.e., CNF-DAC-PPy, the prepared CNF- DAC suspensions were further purified by repeated centrifugation. They were then dialyzed for 15 days against 0.05 M NaCI and UPW, using a membrane with MWCO 14 kDa, until iodometric titration and XRF measurements confirmed the complete removal of all oxidizing agents.

[0052] For the preparation of CNF-DAC-PPy without an oxidizing agent, 335 pL of pyrrole (final concentration 0.5 M) was added to 10 mL of 0.5 wt% CNF suspension, the mixture was acidified with 1 M HCI to pH - 3.0 and heated in a water bath at 75 °C for 48 hours. Approximately after 4 hours, a gray-green color began to appear in the CNF-DAC sample, gradually turning black, while the control sample containing a suspension of unoxidized CNF in 0.5M pyrrole at pH 3 retained its original yellow color associated with the presence of pyrrole, see Fig. 6a. After the reaction was completed, the suspension was dialyzed for 72 hours against 0.2 M HCI, filtered, and repeatedly washed with 0.2 M HCI, water, and ethanol. SEM analysis confirmed the preservation of the fibrous structure similar to CNF-DAC, see Fig. 6a. The presence of the CNF-DAC-PPy copolymer was also confirmed by measuring the specific conductivity according to Example 2. The conductivity of CNF-DAC-PPy reached 0.77 nS / cm, which is more than 300 times higher than in the case of colloidal DAC-PPy measured by the same method in Example 2. The DAC-PPy copolymer is apparently located on the surface of CNF-DAC fibers in a homogeneous layer, which increases the electrical conductivity compared to the sample prepared from a lyophilized colloidal suspension.

[0053] For the preparation of CNF-DAC / PPy composites with covalent anchoring of PPy using DAC-py, an amount of pyrrole corresponding to molar ratios npy: ncHo 1: 1, 2:1, 4:1, and 8:1 (final concentration of pyrrole 0.013 to 0.1 M) was added to the suspension of CNF-DAC with a concentration of 0.5 wt% in UPW and the suspension was stirred at laboratory temperature for 24 hours to form DAC-py as described in Example 1. Polymerization of PPy was initiated directly in the reaction mixture by adding FeCH as an oxidizing agent in a weight ratio of 1:4 (pyrrole : FeCh), which corresponds to a 1.65 molar excess of FeCH, and the suspension was stirred at laboratory temperature for another 24 hours. The samples were filtered and repeatedly washed with 0.2 M HCI, UPW, and ethanol. SEM analysis revealed the presence of PPy grains on CNF-DAC fibers in all samples, with the amount of deposited PPy increasing with the increasing ratio of npy: ncHo, see Fig. 6b. For further analysis, samples CNF-DAC / 2PPy and CNF-DAC / 8PPy were selected, i.e., those prepared using npy: ncHo 2:1 and 8:1. Since the conductivities of these samples were too high to be determined by a two-electrode method, the conductivity was measured using the van der Pauw four-electrode method (digital electrometer Keithley 6517B; voltage source Keithley 2410; scanner Keithley 7002). The specific conductivity of the CNF-DAC / 2PPy sample was 0.708 mS / cm, while for the 8PPy sample, the conductivity reached 0.91 S / cm, which is due to a larger amount of deposited PPy. To demonstrate the advantages of covalent anchoring of PPy in the composite using DAC-py, composites of PPy and unoxidized CNF (further referred to as CNF / 2PPy and CNF / 8PPy) were synthesized in a manner analogous to the preparation of CNF- DAC / 2PPy and CNF-DAC / 8PPy, but with PPy forming a layer attached only by weak interactions. Filtered, washed, and dried samples were then exposed to mechanical degradation in the form of 30 min sonication using an ultrasonic apparatus Bandelin Sonopuls HD 2070 with MS 73 microtip. In Fig. 6c, clear differences between CNF and CNF-DAC samples can be seen at both the micro and macroscopic levels. While in the case of composites prepared using unoxidized CNF fibers, a significant part of the deposited PPy layer was lost, especially in the case of CNF / 2PPy samples, where the PPy layer is almost completely missing, in the case of CNF-DAC / 2PPy and CNF- DAC / 8PPy samples, the PPy layer is still present. Differences between CNF and CNF-DAC samples are also apparent on a macroscopic scale, where ultrasound caused much lower fragmentation of CNF-DAC samples than in the case of CNF samples, see details of Petri dishes in Fig. 6c. Furthermore, a combined thermogravimetric analysis was performed on samples CNF / 2PPy and CNF-DAC / 2PPy and pure PPy, prepared according to Example 2, see Fig. 6d. In the case of the CNF-DAC / 2PPy sample, there is a lower loss of weight between 300 - 600 °C than in the case of the CNF / 2PPy sample, which indicates a thermally more stable system.

[0054] Example 4: Preparation of conductive textiles impregnated with DAP solutions

[0055] A common white fabric made of 100% cotton was carefully washed and cut into square samples of approximately 1.5 x 1.5 cm, which were impregnated with DAC or DAAL solutions of concentration 5 mg / mL and pH 3.5 overnight. Subsequently, the samples were rinsed with UPW and dried, during which the formation of hemiacetal bonds between DAC or DAAL and hydroxyl groups of cellulose in cotton fibers occurred.

[0056] One of the samples impregnated with DAC was then immersed in a 0.5 M solution of pyrrole at pH 3, and heated to 75 °C for 48 hours without the presence of an oxidizing agent. After rinsing and drying, the sample was characterized by SEM, which revealed the formation of spherical DAC-PPy particles on the surface of the fibers of the impregnated fabric, analogous to those formed in the colloidal form in the DAC solution, see Fig. 7a. The gray-green color of the sample also corresponded to the appearance of DAC-PPy colloids and thus the presence of DAC- PPy particles. Given the absence of contacts between particles on the surface of the fibers, the conductivity of the sample was still measurable by the two-electrode method (see Example 2), but very low at 8.2 x 10-5nS / cm. However, the possibility of preparing conductive fabrics by reaction without an oxidizing agent was confirmed.

[0057] Furthermore, samples of cotton fabric impregnated with DAC or DAAL solutions were used to prepare DAC / PPy and DAAL / PPy composites. First, the samples were immersed in a 0.025M and 0.1M solution of pyrrole for 24 hours under constant stirring to form DAC-py and DAAL-py on their surface. Subsequently, the addition of FeCH in a weight ratio of 4:1 to pyrrole initiated its polymerization. After 24 hours, the fabric samples were removed from the solution, repeatedly rinsed (0.2 M HCI, UPW, and methanol, UPW), sonicated in an ultrasonic bath for 5 minutes to remove unbound PPy, and then dried. Because the composition of the reaction mixture corresponded to the conditions used for CNF-DAC / 2PPy and 8PPy composites in Example 3, these samples are further labeled analogously to those in Example 3, i.e., as DAC / 2PPy, DAAL / 2PPy, DAC / 8PPy, and DAAL / 8PPy. Composites of PPy and unimpregnated cotton fabric were prepared in the same way as DAC / 2PPy, DAAL / 2PPy, DAC / 8PPy, and DAAL / 8PPy samples, and labeled as B / 2PPy and B / 8PPy, where B stands for „blank" as these represent reference samples. SEM analysis, as well as photographs of composite fabric samples, confirms the formation of a PPy layer on the surface of the fibers, see Fig. 7b-d. In the case of DAAL-impregnated fabric, the deposited PPy particles are far smaller and more separated than in samples impregnated with DAC or not impregnated at all (B series). This was also confirmed by the analysis of the specific surface area of the samples using the BET method (Belsorpmini II, BEL Japan Inc., Japan). The specific surface area of the B series samples was 2.93 m2 / g for the B / 2PPy sample and 1.97 m2 / g for B / 8PP. For the series of samples impregnated with DAC, it was 3.89 m2 / g for DAC / 2PPy and 3.57 m2 / g for DAC / 8PPy. The highest values were recorded for samples impregnated with a DAAL solution, being 4.81 m2 / g for DAAL / 2PPy and 5.65 m2 / g for DAAL / 8PPy, which is apparently due to the mentioned presence of smaller and more separated PPy particles. The specific conductivity of the samples was determined using the four-point van der Pauw method, see Example 3. The highest conductivity among 2PPy samples had the DAC-2PPy sample (0.99 mS / cm), followed by the B / 2PPy sample (0.59 mS / cm), while the conductivity of the DAAL / 2PPy sample was significantly lower (2.7 pS / cm), apparently due to the mentioned greater separation of deposited PPy particles. In the 8PPy series, the conductivities of the samples were similar and ranged in the order of tens of mS / cm (B / 8PPy - 43 mS / cm, DAC / 8PPy - 28 mS / cm, DAAL / 8PPy - 14 mS / cm). B / 2PPy and DAC / 2PPy samples were then subjected to repeated washing cycles in the presence of detergent at 60 °C (total 72 hours), followed by 1 hour of sonication using an ultrasonic tip VS 70T (Bandelin Sonopuls HD 2070). BET analysis was then performed again on these samples. While the specific surface area of the B / 2PPy sample increased by 65% to 4.81 m2 / g and the total pore volume by 35% to 1.38 x 10’2cm3 / g, the DAC / 2PPy sample showed an increase in specific surface area by 45% to 5.65 m2 / g and total pore volume by only 9 % to 1.49 x 10-2cm3 / g. Thus, in the case of the B / 2PPy sample, there was a relatively higher disruption of the composite structure, which manifested itself in an increase in porosity, than in the case of DAC / 2PPy, which, similarly to Example 3, indicates a higher stability of composites containing DAP.

[0058] Example 5: Composites ofPPy and chitosan impregnated with DAC, DAAL, DADXA, and DAH

[0059] Chitosan (CHIT) nanofibers were prepared using electrospinning with the following parameters. CHIT with a viscosity average molecular weight Mv- 190-310 kDa and a degree of deacetylation of 75-85% was dissolved at a concentration of 20 mg / mL in 70% acetic acid for 72 hours. Subsequently, polyethylene oxide (PEO) was added to the chitosan solution as a fiberforming additive and the solution was stirred for 24 hours. The prepared solution (dynamic viscosity - 1.65 Pa.s, conductivity - 869 pS / cm) was filtered using a 1 pm glass fiber filter, degassed, and electrospun using a SpinLine 40 device (SPUR a.s., Czech Republic) at a spinning voltage of 60 kV for 60 minutes. Samples weighing 1.9 ± 0.1 mg were cut from the nonwoven fabric of chitosan nanofibers and then impregnated with a DAC solution prepared according to Example 1 (concentration of 2 mg / mL, pH 6.5, 4 hours), resulting in the binding of DAC to the surface of CHIT fibers due to the formation of imine bonds. The prepared CHIT-DAC samples were rinsed with UPW to remove unbound DAC and then inserted into pyrrole solutions containing 0, 10, 50, 200, 500, and 1000 mol% relative to -CHO groups, where they were left overnight (16 hours) to form CHIT-DAC-py according to Example 1. The amount of pyrrole was selected based on the maximum theoretical amount of DAC that can bind to 1.9 mg of CHIT matrix with a degree of deacetylation of 85% containing 9 pmol of -NH? groups, i.e., 0.7 mg of DAC. Such an amount of DAC is theoretically capable of binding up to 1.2 mg of pyrrole assuming npy: ncHo 2:1. This amount of pyrrole was therefore chosen as the reference value, i.e., 100 mol% relative to -CHO groups of DAC in the samples. Next, 1 mL of a solution containing a threefold molar excess of oxidizing agent (FeCh) relative to the amount of pyrrole was added to each sample, and the solutions were left to react for 4 hours. Reference CHIT_PPy sample was prepared similarly, i.e., by exposing 1.9 mg of CHIT nanofibers to a pyrrole solution in an amount corresponding to 200 mol% in CHIT-DAC samples, but without prior impregnation with DAC. Subsequently, the samples were removed from the reaction mixture, purified by rinsing in UPW, 0.2 M HCI, ethanol, and again in UPW, lyophilized, and characterized. The names of the prepared samples refer to the method of their preparation, i.e., CHIT-DAC_PPyO to CHIT-DAC_PPylOOO correspond to samples, for which between 0 and 1000 mol% of pyrrole relative to DAC was used, and the reference sample is labeled as CHIT_PPy. Photographs of reaction mixtures at different times of the reaction are given in Fig. 8. For SEM analysis of CHIT fibers, CHIT-DAC_PPyO to CHIT-DAC_PPyl000 and CHIT_PPy, see Fig. 9. The evidence of a reaction between -CHO groups of DAC and -NH? groups of CHIT, resulting in imine bond formation, is provided by a comparison of FT-IR spectra for pure CHIT and CHIT-DAC in Fig. 10, namely by the disappearance of N-H bending vibration of primary amine of chitosan at 1565 cm1after reaction with DAC and the formation of an imine bond. The presence of the imine bond itself is evidenced by vibrations at 1640 cm1in the CHIT-DAC spectrum, while C=O vibrations at 1730 cm1demonstrate the presence of free -CHO groups, which can subsequently be used to form CHIT-DAC-py.

[0060] The advantage of using CHIT-DAC over CHIT for the preparation of composites is evident from Fig. 8. In the case of CHIT-DAC samples, the action of FeCh leads to the formation of PPy primarily on the surface of the nanofibers due to the presence of CHIT-DAC-py promoting the binding of PPy to the surface of the fibers. This phenomenon is best observable in the CHIT- DAC_PPy200 sample, on the surface of which the formation of a black layer of PPy can be clearly observed already 30 minutes after the start of polymerization, without a visible growth of PPy particles in the surrounding reaction mixture, see Fig. 8. In comparison, the formation of PPy on the surface of the CHIT_PPy sample (reference sample prepared in the same way as CHIT- DAC_PPy200 but without impregnation with DAC) is significantly limited. After 30 minutes of reaction, the presence of PPy is barely noticeable and after 4 hours PPy grows in the the entire volume of the solution, not on the surface of the fibers as is the case with CHIT-DAC_PPy200. Only in the case of CHIT-DAC_PPy500 and CHIT-DAC_PPyl000 samples, where pyrrole is in high excess relative to DAC, PPy is also formed in the reaction mixture outside the CHIT-DAC surface, because the DAC on the sample surface is probably saturated already after 15 minutes. Nevertheless, even after 4 hours, the solution of the CHIT-DAC_PPy500 sample is significantly less clouded than in the case of CHIT_PPy despite a 2.5x higher amount of added pyrrole. The use of DAC thus initiates a preferential coverage of the matrix surface with PPy, thus allowing for a decrease in the amount of reactants for the preparation of composites. Furthermore, the reference CHIT-PPy sample also changes its structure and visibly swells immediately after the addition of FeCH, which lowers the pH of the reaction mixture to ~2, see Fig. 8. This is a direct consequence of the solubility of CHIT in an acidic environment. After the reaction, the CHIT-PPy sample was gel-like, disintegrated during manipulation, completely lost nanofibrous structure, and formed an inhomogeneous matrix with formations similar to PPy grains observable on its surface, see Fig.9. In comparison with the reference sample, none of the prepared CHIT-DAC_PPy samples showed a significant change of properties and all samples retained their original shape and structure, see SEM analysis in Fig. 9.

[0061] FT-IR analysis of CHIT-DAC_PPy200 to CHIT-DAC_PPylOOO samples shows the spectral similarity of these materials with pure PPy, see Fig. 10 c, h, i, and j. The presence of PPy in CHIT- DAC_PPylO and CHIT-DAC_PPy50 samples, which were not colored black, can also be confirmed based on FT-IR spectra, where the band of bound pyrrole around 1530 cm1is evident, see Fig. 10 f, g. On the other hand, the FT-IR spectrum of CHIT_PPy differs from both pure PPy and chitosan, although the band around 1530 cm'1, associated with the formation of PPy, is still noticeable.

[0062] The conducted experiments confirmed that during impregnation, DAC binds covalently to CHIT by imine bonds arising from the reaction between carbonyl groups of DAP and amino groups of CHIT. Due to the excess of DAC and its macromolecular character, free carbonyl groups of DAC are still available after reaction with CHIT, allowing a covalent bonding of pyrrole by aldol condensation reaction as described in Example 1. The resulting CHIT-DAP-py preferentially initiates the formation of PPy on the surface of the impregnated matrix, which increases the efficiency of matrix coverage compared to unimpregnated material and leads to the more efficient synthesis of PPy composites. Another significant benefit of this method is the preservation of the structure of CHIT nanofibers even in the case of a very acidic environment (pH 2), due to the covalent cross-linking of their surface with DAC. The resulting CHIT-DAP is, thanks to imine bonds between CHIT and DAP, significantly more resistant to low pH than CHIT, which is practically impossible to use without impregnation as it dissolves at low pH.

[0063] Based on the preparation of CHIT-DAC_PPy composites, samples of CHIT nanofibers impregnated with DAAL, DAH, and DADXA prepared in Example 1 were manufactured. The methodology for preparation was similar to that of the CHIT-DAC_PPy200 samples, i.e., CHIT bodies (1.9 mg) were inserted for 4 hours into three 2 mg / mL solutions of the aforementioned DAPs with a pH of 6.5 to obtain imine bonds between DAP and CHIT. Subsequently, the CHIT-DAP bodies were removed, purified by washing in UPW to remove unbound DAP, and placed into 5 mL of solution containing 200 mol% of pyrrole relative to the maximum theoretical amount of bound DAP. The CHIT-DAP samples were left in the pyrrole solution for 16 hours. This was followed by the addition of 1 mL of a solution containing FeCH in a threefold molar excess relative to the used pyrrole. The oxidation of pyrrole by FeCh was monitored for 4 hours (see Fig. 11a). After this period, the prepared samples of CHIT-DAAL_PPy200, CHIT-DAH_PPy200, and CHIT- DADXA_PPy200 were rinsed in UPW, 0.2 M HCI, ethanol, and again in UPW, lyophilized and further characterized using FT-IR, see Fig. lib, c, d, and SEM, see Fig. 12.

[0064] The rate of PPy formation on the surface of CHIT-DAP depends on the used DAP, e.g., when using DADXA, there is a very rapid formation of PPy layer exclusively on the surface of the CHIT-DADXA body, similarly to the case of DAC. Conversely, the growth of PPy is significantly slower in the case of DAAL and DAH, resulting in the formation of free colloidal PPy in the solution, especially in the case of DAH. These results reflect the amount of -CHO groups in individual aldehydes. The highest amount of -CHO groups is in DADXA, and the lowest is in DAH, see Example 1. DADXA can thus bind significantly more forming PPy than DAH of the same weight. From the perspective of FT-IR analysis, samples prepared using DAAL, DAH, and DADXA exhibit identical spectral bands as in the case of CHIT-DAC_PPy200. SEM analysis of samples prepared with various DAP confirmed the formation of PPy on the surface of CHIT-DAP nanofibers in all cases, see Fig. 12. For samples prepared using DAAL and DADXA, there was no change in structure. However, when using DAH, partial sintering of nanofibers is visible, probably due to limited stabilization. This is a consequence of the lower formation of imine bonds between CHIT and DAH, likely due to the lower content of -CHO groups in DAH, see Example 1. For selected samples (CHIT- DAC_PPy200 and CHIT-DAAL _PPy200), the following conductivity values were measured using the two-electrode method according to Example 2: CHIT-DAC_PPy200 - 0.23 pS / cm, CHIT- DAAL_PPy200 - 0.13 pS / cm. Example 6: PPy Composites with Polyamide or Polyurethane Impregnated with DAC

[0065] Polyamide (PA) and polyurethane (PU) nanofibers prepared by electrospinning similarly as in Example 5 were impregnated using DAC prepared according to Example 1 and then, using the procedure in Example 5, immersed in a solution containing 200 mol% pyrrole relative to the theoretical amount of bound DAC. After 16 hours, the polymerization of pyrrole was initiated by adding a threefold molar amount of FeCh relative to pyrrole, and the samples were washed. The resulting PA-DAC_PPy and PU-DAC_PPy composites were characterized using FT-IR and SEM analysis, see Fig. 13. As in Example 5, the impregnation of PA or PU nanofibers with DAC led to preferential growth of PPy on the surface of PA-DAC and PU-DAC bodies, see Fig. 13 b, d. The FT- IR spectra of the purified samples in Fig. 13 a-d also contain characteristic spectral bands of PPy, see Example 5. SEM analysis confirms the complete decoration of PA and PU nanofibers with PPy, see Fig. 13. The conductivities of the bodies determined using the two-electrode method according to Example 2 were 6.3 pS / cm for PU-DAC_PPy200 and 2.9 pS / cm for PA-DAC_PPy200.

[0066] Example 7: Conductive PVA / DAC_PPy hydrogels prepared by dual crosslinking

[0067] For the preparation of hydrogels with covalently bound PPy acting as a secondary crosslinker, the aldehyde groups of DAC were first partially saturated by pyrrole, and the remaining free aldehyde groups of DAC were subsequently used for crosslinking PVA. The individual components of the composite were first prepared separately. By dissolving 15 g of PVA (Mowiol 18-88 with an average molecular weight of 130 kDa and a degree of hydrolysis of 88 %) in 210 mL of ultra-pure water for 24 hours at 75°C, a PVA solution was prepared and subsequently divided into 3 aliquots. After complete dissolution, 1.5 mL of 1.33M HCI (catalyst of crosslinking reaction) was added to each solution, and these mixtures were stirred for another 3 hours. Furthermore, three 30 mL solutions containing 0.05, 0.15, and 0.25 g of DAC prepared according to Example 1 were made, which corresponds to 1, 3, and 5 wt% of DAC relative to PVA. Subsequently, pyrrole was added to the DAC solutions in an amount corresponding to ncHo of the used DAC, i.e., 20.3, 60.8, and 101.3 pL. These DAC solutions with pyrrole were then stirred for 3 hours to allow for the aldol condensation of pyrrole and DAC. Subsequently, the solutions containing PVA and HCI were thoroughly mixed with the DAC and pyrrole solutions, poured into molds of 200 x 100 mm, and dried at 35 °C for 96 hours in a ventilated dryer. The resulting thin films were then washed in UPW for 72 hours at 40 °C with regular water exchange. After washing, bodies with a diameter of 15 mm were punched out of the swollen hydrogels and placed into a 2 vol% solution of pyrrole with a total volume of 100 mL, where they were left for 72 hours at 40 °C. During this time, a reaction occurred between pyrrole and any free -CHO groups of DAC, and the structure of the PVA / DAC hydrogels was completely saturated with pyrrole. Subsequently, a solution of FeCh (20 mL containing 69.9 mg of FeCh) was added, and the oxidative reaction between pyrrole and FeCh took place over 24 hours at 40 °C. Afterward, the bodies were removed from the reaction mixture and washed in UPW, 0.2 M HCI, ethanol, and again in UPW. The prepared materials differ in the amount of DAC as the primary crosslinking agent (1, 3, 5 %) and are labeled as PVA / DACl_PPy, PVA / DAC3_PPy, and PVA / DAC5_PPy. Part of the prepared samples was left in a swollen state for measuring rheological properties, network parameters, and conductivity, and part was shock-frozen and lyophilized into cryogels for FT-IR and SEM analysis.

[0068] Figure 14a shows the FT-IR analysis of dried PVA / DAC samples after the reaction with pyrrole but before the oxidative reaction. Absorption bands around 920 and 1050 cm1are clearly visible in the spectra, signaling the presence of DAC-py. These bands can also be seen in the IR spectra of cryogels prepared by lyophilization of PVA / DAC_PPy hydrogels, where a vibrational band of the pyrrole cycles at 1558 cm1is also visible, see Fig. 14b. The figure also includes a photograph of the PVA / DAC5_PPy sample in its swollen form, which forms a stiff, yet flexible hydrogel. The lower part of Fig. 14 then presents examples of SEM analysis of brittle fractures of PVA / DAC_PPy cryogels performed in liquid nitrogen. Here, the differences between samples prepared with varying amounts of crosslinker, and thus DAC-py, are the most evident. The least crosslinked material PVA / DACl_PPy shows almost no porosity and despite the evident black coloring and the presence of I R absorption bands of PPy, there are no visible signs of the presence of typical grains formed by PPy. It can therefore be assumed that chains of PPy and PVA / DAC form what is called an "interpenetrating network," i.e., a highly homogeneous network of mutually intertwined chains. Given the smallest amount of the first crosslinking agent used, this material swells the most (414 ± 7%) and thus can absorb the most water (equilibrium water content EWC - 80.5 ± 0.7%). An increase in DAC concentration to 3 wt% leads to visible changes in the IR spectrum (increase in the intensity of the pyrrole cycle band at 1558 cm-1) and also to a noticeable change in the fracture structure, where spherical PPy grains begin to appear. This material swells to 183 ± 7% and has EWC - 64.7 ± 0.9%. A further increase in the amount of DAC to 5 wt% leads to surprising changes in structure, as this strongly crosslinked sample shows a significant change in the morphology of the brittle fracture, having a clearly visible porous layout. The observed formations sometimes form a columnar structure atypical for PVA-based cryogels. From the perspective of network parameters, this material is capable of limited swelling of 126 ± 2% and EWC - 55.8 ± 0.4%, which is a consequence of a very tightly crosslinked structure.

[0069] The rheological properties of the prepared hydrogels with double crosslinking PVA / DACl_PPy, PVA / DAC3_PPy, and PVA / DAC5_PPy are given in Fig. 15. For comparison, a sample of PVA / DAC3_py was also measured. This sample was prepared analogously to PVA / DAC3_PPy, but the polymerization of pyrrole was not induced. This hydrogel is thus crosslinked only by DAC, instead of interpenetrating networks of DAC and PPy. The results show a significant increase in complex (G*) elastic (G') and loss (G") modules between the samples PVA / DACl_PPy and PVA / DAC3_PPy, i.e., with an increasing amount of crosslinker. In contrast, the PVA / DAC5_PPy sample shows a decrease in values for all modules compared to PVA / DAC3_PPy, presumably due to a different structure of hydrogels, see Fig. 14. The advantages of crosslinking by interpenetrating networks of DAC and PPy are evident from the comparison of the samples PVA / DAC3_py and PVA / DAC3_PPy. In samples with dual crosslinking, the values of G* and G' are almost double compared to PVA / DAC3_py, which indicates higher elasticity of hydrogels and thus a denser hydrogel network. The conductivity of swollen hydrogels determined using the two-electrode method (see Example 2) ranged between 0.088 mS / cm and 0.111 mS / cm depending on the amount of DAC.

[0070] DAC partially decorated with pyrrole oligomers is thus still able to crosslink PVA thanks to the partial availability of free carbonyl groups. After adding an oxidizing agent, chemically and physically anchored PPy chains are formed, creating an "interpenetrating network" structure in hydrogels that, among other things, improves the mechanical properties of hydrogels. Example 8: Preparation of composite CHIT / DAC hydrogel films with anchored colloidal PPy particles

[0071] Colloidal PPy particles stabilized with polyvinylpyrrolidone (PVP) were prepared by dissolving PVP in UPW at a concentration of 2 wt%. Then, 5 mmol of pyrrole was added and the mixture was sonicated for 30 minutes, followed by the addition of an oxidant (FeCh, 5 mmol). The solution was left to react at laboratory temperature for 24 hours, and after the reaction was completed, it was dialyzed against 0.2 M HCI for 14 days. The resulting colloidal particles had a hydrodynamic diameter of 170 ± 3 nm and PDI - 0.27 (DLS analysis, Zetasizer Nano ZS90, Malvern Instruments). For the preparation of composite hydrogel films, 200 mg of chitosan (degree of acetylation 43%) was dissolved in 15 mL of UPW, and then an amount of PPy colloid containing 10 and 20 mg of PPy particles, i.e., 5 or 10 wt% relative to CHIT, was added. After mixing, DAC was added in an amount corresponding to 2 wt% of CHIT. The mixture was then poured into molds and dried at 40 °C. Subsequently, the samples were rinsed for 7 days in UPW at laboratory temperature. The resulting CHIT-DAC / PPy5% and CHIT-DAC / PPyl0% thin films exhibited swelling of 3100 ± 900% and 7700 ± 900%, respectively, and conductivity in the swollen state of 2.7 mS / cm and 5.1 mS / cm according to the two-electrode method, see Example 2. SEM analysis revealed a smooth surface of the hydrogel films with homogeneously dispersed PPy particles anchored in the structure of the hydrogels even after prolonged (1 month) rinsing, see Fig. 16a.

[0072] To obtain a proof of the reaction between colloidal PPy stabilized with PVP and DAC, 0.5 mL of colloid containing 10.1 mg of PPy was mixed with a DAC solution in a weight ratio of PPy: DAC 1:10, and the Raman spectrum was subsequently recorded (Nicolet DXR Raman microscope, excitation laser wavelength 455 nm). The reaction between PPy particles and DAC is evidenced by the disappearance of the DAC carbonyl group signal at 1637 cm1in the Raman spectrum due to a reaction with PPy, while other DAC bands in the 800-1000 cm1region remained intact.

[0073] Subsequently, the hydrogels were tested for their ability to accelerate wound healing using the scratch test (disruption of the fibroblast monolayer, NIH / 3T3 cell line). For this purpose, a CHIT-DAC sample was also prepared in the same way as both previous samples, but without the addition of PPy colloid. Compared to the reference (cells incubated without hydrogels), both samples containing PPy showed significantly faster migration of cells to the disrupted area (acceleration of simulated healing). After 10 hours from the creation of the injury, 84 ± 9% of the area remained unhealed when using the hydrogel without PPy, while after the application of CHIT-DAC / PPy5% it was only 37 ± 2% (p <0.001) and 58 ± 6% (p <0.05) for the CHIT-DAC / PPyl0% sample, see Fig. 16c. Compared to the CHIT-DAC sample without PPy, there was a statistically significant acceleration of healing in the CHIT-DAC / PPy5% sample, Fig. 16d.

Claims

C L A I M S1. A method for preparing conductive co-oligomers and copolymers of pyrrole and conductive composites or conductive hydrogels based on them, characterized by that the polysaccharide with at least one pyranose cycle carrying hydroxyl groups in positions 2 and 3 is at least partially oxidized by the action of an alkali metal periodate to form the dialdehyde of the given polysaccharide, then the residues of the oxidizing agents are completely removed from the dialdehyde polysaccharide by dialysis or repeated centrifugation, and the dialdehyde polysaccharide is isolated by filtration, centrifugation, or lyophilization, after which either a) for the preparation of co-oligomers and copolymers of pyrrole without the use of chemical or electrochemical polymerization, the obtained dialdehyde polysaccharide is exposed to aqueous solution of pyrrole in an amount corresponding to 1 to 20 times the molar amount of aldehyde groups in the dialdehyde polysaccharide for 3 to 48 hours in an acidic environment with a pH between 3 and 6.5, where a condensation reaction occurs between the carbonyl groups of the dialdehyde polysaccharide and pyrrole at laboratory temperature, namely the substitution of hydrogen atom or atoms in the a positions of the pyrrole cycle and the formation of a covalent bond between pyrrole and dialdehyde polysaccharide and thus the decoration of the dialdehyde polysaccharide with pyrrole, with the fact that at elevated temperatures or after subsequent heating, preferably to 50 to 75°C, bound pyrrole cycles are linked by the same condensation reaction into higher units via -CH- bridges formed from the original carbonyl groups of the dialdehyde polysaccharide and the chains of the dialdehyde polysaccharide thus function as a template for the formation of conductive co-oligomers and copolymers of pyrrole with dialdehyde polysaccharide, whereby if the dialdehyde polysaccharide is fully dissolved in water, the co-oligomers and copolymers of dialdehyde polysaccharide and pyrrole take the form of a conductive colloidal solution or dispersion, but if the dialdehyde polysaccharide is in an insoluble form, preferably in the form of surface-oxidized cellulose fibers, or if the dialdehyde polysaccharide is located on the surface of another insoluble polymer of hydrophilicnature carrying -OH, or -NH? groups with which the dialdehyde polysaccharides can react to form hemiacetals or imines, preferably cotton fabric, conductive co-oligomers and copolymers of dialdehyde polysaccharide and pyrrole are formed on the surface of such materials, and these thus become conductive or b) for the preparation of conductive composites, dialdehyde polysaccharide, in the form of fibers, nanofibers, or as a layer on insoluble natural or synthetic hydrophilic polymers, impregnated with dialdehyde polysaccharide solution, found in the form of fibers, nanofibers, or fabrics carrying -OH, -NH?, or -NH groups, with which dialdehyde polysaccharides react to form hemiacetals or imines, further referred to as matrices, is reacted with an aqueous solution of pyrrole in a molar amount corresponding to 0.1 to 10 times the amount of aldehyde groups present in the dialdehyde polysaccharide at laboratory temperature for 16 to 24 hours, during which the dialdehyde polysaccharide is decorated with pyrrole, followed by the initiation of in situ polymerization of the remaining pyrrole into polypyrrole by adding a suitable oxidizing agent, preferably FeCH in a 1.65 to 3 times molar excess relative to the pyrrole, with the reaction running for 4 to 24 hours, during which the pyrrole cycles covalently bound to the dialdehyde polysaccharide are incorporated into the forming polypyrrole chains, which are preferably forming on the surface of the dialdehyde polysaccharide or dialdehyde polysaccharide-impregnated matrices and become covalently connected with them, which leads to more effective coverage of dialdehyde polysaccharide or dialdehyde polysaccharide-impregnated matrices with polypyrrole at the given concentration of pyrrole when compared to unoxidized or unimpregnated matrices and to the increase of the resistance of the deposited polypyrrole layer against peeling from the matrix while maintaining the electrical conductivity of the composites thus prepared or c) for the preparation of conductive hydrogels, pyrrole is first added to the dialdehyde polysaccharide in a molar amount that is lower than the molar amount of aldehydegroups in the dialdehyde polysaccharide, preferably in a molar ratio of 0.5:1 for pyrrole: aldehyde groups in the dialdehyde polysaccharide, the mixture is stirred for at least 3 hours to decorate the dialdehyde polysaccharide with pyrrole, the solution of pyrrole-decorated dialdehyde polysaccharide is subsequently mixed with a solution of a water-soluble polymer carrying -OH, or-NH? groups, preferably polyvinyl alcohol, in an amount sufficient for its crosslinking, preferably 1 to 5 wt% relative to the polymer, poured into molds and left to crosslink during drying, with the resulting materials being washed in water and then again immersed in an excess of pyrrole solution until the formed hydrogel is saturated with pyrrole, preferably for 72 hours, after which the polymerization of pyrrole is initiated using a molar excess of FeCh relative to pyrrole in the solution, during which polypyrrole chains are formed inside the structure of the hydrogel and because these also include cycles from pyrroledecorated dialdehyde polysaccharide, chemical anchoring of polypyrrole molecules in the hydrogel and thus a secondary crosslinking of the hydrogel structure occurs, which improves mechanical properties of the hydrogel and leads to the acquisition of electrical conductivity or d) dialdehyde polysaccharide is used for the preparation of conductive composite hydrogels, where the dialdehyde polysaccharide is first used to crosslink soluble polymers carrying -OH, or -NH? groups, preferably chitosan, in an amount sufficient for its crosslinking, preferably 2 wt% relative to the amount of dissolved polymer, whereby a colloidal solution or suspension of polypyrrole particles, prepared without the presence of dialdehyde polysaccharide using known methods, is added to the polymer solution before its mixing with dialdehyde polysaccharide, preferably in an amount of 5 to 10 wt% relative to the amount of dissolved polymer, and, after mixing of all components, the resulting slowly solidifying solution is transferred into a mold and dried, during which bonds are formed both between the dialdehyde polysaccharide and the polymer and between the dialdehyde polysaccharide and the polypyrrole particles, which chemically anchors them in the structure and limits theirpossible leaching from thus prepared conductive composite hydrogels, which also accelerate wound healing in the form of hydrogel coverings.

2. The method according to claim 1, characterized in that the polysaccharide with at least one pyranose cycle carrying hydroxyl groups in positions 2 and 3 is a polysaccharide from the group including cellulose, dextran, hyaluronic acid, alginate, dextrin, starch, amylose, pectin, schizophyllan, scleroglucan, or xanthan.

3. The method according to claim 1, characterized in that the synthetic polymer of hydrophilic nature in the form of fibers, nanofibers, or fabrics carrying -OH, -NHz, or -NH groups is a polymer from the group including cellulose, chitosan, polyurethane, or polyamide.

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