新型吡咯并嘧啶改性壳聚糖水凝胶：增强电学特性与抗菌活性

• Article
• Open access
• Published: 26 October 2026

• Amina A. Abd El-Gwaad¹,
• T. A. Zidan²,
• Eman A. Karam³ &
• …
• Eman A. Mwafy⁴ 

Scientific Reports volume 16, Article number: 34061 (2026) Cite this article

Abstract

A novel pyrrolopyrimidine-modified chitosan hydrogel (3) is synthesized and charcterized. Pyrrolopyrimidine compound (2) is firstly synthesized and then it is used to chemically modify chitosan through the formation of imine linkage. The synthesized compounds are characteized by Fourier transforms infra red spectroscopy (FTIR), proton and carbon nuclear magnetic resonance (¹HNMR and ¹³CNMR), and Field emission scanning electron microscope (FESEM). The prepared hydrogel undergoes multifunctional studies including electrical properties and antimicrobial activity. This research examines the dielectric and alternating-current conductivity characteristics of the pyrrolopyrimidine-modified chitosan hydrogel across different frequencies and temperatures, compared with the pure chitosan sample. Dielectric and AC conductivity properties of pyrrolopyrimidine-modified chitosan hydrogel are systematically investigated across a frequency range and temperatures from 20–90 °C, benchmarked against pure chitosan networks. Pure chitosan exhibits high low-frequency dielectric loss and permittivity due to pronounced Maxwell–Wagner–Sillars interfacial polarization from mobile ions and trapped charges along polar groups, alongside frequency-dependent AC conductivity governed by ion hopping. Pyrrolopyrimidine modification significantly suppresses dielectric loss while preserving permittivity, introduces a characteristic conductivity minimum at intermediate frequencies indicating restricted long-range ion migration, and yields a thermally stable response with reduced dissipative pathways. These enhancements stem from heteroaromatic cross-linking, π–π interactions, and constrained segmental mobility, which limit charge accumulation and leakage. The tailored dielectric and conduction behavior positions pyrrolopyrimidine-chitosan hydrogels as promising materials for electroactive devices, sensors, and energy storage systems requiring balanced polarization and minimal losses. The synthesized compounds are investigated for their antimicrobial activity. They are examined against two gram-positive bacteria (Bacillus cereus 33,018 and Bacillus subtilis 6633), two gram-negative bacteria (Pseudomonas aeruginosa 9027 and Salmonella typhimurium 14,028), and two yeast-like fungi (Candida albicans 10,231 and Candida tropicalis 750). The antimicrobial activity of the target compounds (1–3) is compared with Amoxicillin for bacteria and clotrimazole for yeast and fungi. The minimum inhibitory concentration for the prepared compounds is detected. The results show that the pyrrolopyrimidine compound (2) has high activity towards both bacterial and fungal strains. The antimicrobial activity of pure chitosan shows low activity. By modification of citosan by pyrropyrimidine compound, the activity increases towards bacterial strains but no activity towards fungal strains. Based on the results, the synthesized pyrrolopyrimidine derivatives and the modified chitosan hydrogel exhibit useful characteristics for biomedical applications, including potential use as antimicrobial wound-care and drug-delivery materials. Furthermore, the results obtained for the dielectric and AC conductivity properties of the modified hydrogel indicate its potential for use in selected sensing, bioelectronic, and electroactive systems where control of dielectric characteristics, minimal dielectric loss, and antimicrobial properties are required.

Introduction

Polymeric materials are virtually used in every part of life because of advances in nanoscience¹. Biodegradable polymeric materials resulting from natural resources can be used to get rid of environmental problems and also improve the properties to be used in different applications^2,3. Chitosan is a versatile amino polysaccharide biopolymer obtained from chitin. Chitin is the second most prevalent polysaccharide in nature, after cellulose. It serves as the major element in marine creatures such as prawns, crabs, shrimps, lobsters, octopuses, squids, and various fish. Additionally, it is found in the exoskeletons of crustaceans, some insects, and the cell walls of fungi. Chitosan is produced by the deacetylation process using an alkaline substance, such as sodium hydroxide (NaOH), as a reagent and water as a solvent at high temperatures⁴. It is classified as a polysaccharide that possesses a multitude of advantageous characteristics, notably its extensive antimicrobial efficacy against diverse pathogenic microorganisms⁵. The antimicrobial attributes of chitosan have been the subject of rigorous investigation and have been shown to be effective against an array of microorganisms, comprising a variety of fungal species and both gram-positive and gram-negative bacteria⁶. Chitosan is a highly important ingredient in a wide range of items, including food, medicines, cosmetics, chemicals, and agricultural commodities, due to its remarkable antibacterial properties⁷. It has attracted considerable interest as a natural substitute for traditional antimicrobial agents, attributable to its biocompatibility, biodegradability, low toxicity, and environmental sustainability. Understanding the mechanisms of action and the variables that affect chitosan's antibacterial activity is crucial⁸. Identifying the underlying mechanisms of chitosan's interaction with microorganisms will help researchers develop ways to increase its effectiveness. Additionally, determining the relevant parameters offers important information for maximizing the antibacterial effectiveness of chitosan in various applications^{9,10,11,12,13}. The most basic mode of action is electrostatic interactions between the negatively charged microbial cell membranes and the positively charged chitosan NH₃⁺ sites. The interaction modifies the permeability of the microbial cell, releasing intracellular substances¹⁴. Chitosan's binding to microbial enzymes and nucleotides has been shown by Chung et al.¹⁵ to damage the cell structure of Staphylococcus aureus and Escherichia coli. It has also been shown that chitosan is useful in changing the calcium concentration in the cell walls¹⁶. In this case, chitosan interacts with peptidoglycan stability and modifies the osmotic equilibrium of the cell membrane to produce its antibacterial activity¹⁷. Erol et al. prepared chitosan/ZnO-hesperidin nanocomposites by adding different ratios of the ZnO-hesperidin to the biodegradable chitosan biopolymer¹⁸. They found that the prepared nanocomposites have a remarkable effect against Escherichia coli and Staphylococcus aureus microorganisms. Artun et al. synthesized poly(2-(3,5-dichloroanilino)-2-oxoethyl 2-methylprop-2-enoate) (PDCOEMA). The blend of PDCOEMA with chitosan (CS) was prepared by the hydrothermal method¹⁹. Antimicrobial, anticancer, cytotoxic, antioxidant, and wound healing properties of the nanocomposites were determined. It was observed that the nanocomposites have good anticancer activity against A549 cells. Khamidov et al. blended poly (pentafluorophenyl)methyl 2-methylprop-2-enoate (PPFOEMA) with CS biopolymer by in situ/hydrothermal method²⁰. Commercial graphene oxide (GO) and biosynthesized silver nanoparticles (AgNP) were incorporated into the CS-PPFOEMA mixture. The antimicrobial, antioxidant, anticancer, and wound healing properties were evaluated. Erol et al. studied the biological activity of green synthesized Ag-containing nanocomposites of a novel chitosan-based blend²¹. They found that the antimicrobial activity increased and the nanocomposites have anticarcinogenic activity. Additionally, chitosan can compromise the membrane's energy stability by interfering with oxygen reduction and the electron transport chain^22,23. Numerous researches have examined the application of chitosan blends with inorganic composites, showing notable improvements in these materials’ electrical characteristics²⁴. These properties, together with the antimicrobial activity of chitosan, may support potential applications in biomedical and pharmaceutical fields, particularly in antimicrobial wound-care and drug-delivery materials, as well as in selected sensing and bioelectronic systems. Abusnina et al. investigated the physical characteristics of chitosan using various methods. The dielectric characteristics, such as the dielectric constant and ac conduction mechanisms, were examined between 305 and 395 K²⁵. For extra investigations, the electronic sensors based on chitosan were the research goal for the use in the environmental protections²⁶. The electrical characteristics of biopolymer electrolytes based on chitosan and PVA for electrochemical devices were investigated by Naveen C. and Muthuvinayagam M.²⁷. Electrochemical impedance spectroscopy investigation revealed that the Chitosan:PVA:MgCl₂ polymer electrolyte has a maximum ionic conductivity of 5.9 × 10⁻⁵ S/cm. The dielectric, optical and morphological characteristics of thin films of chitosan biopolymer produced using spray pyrolysis process were investigated by Saadi et al.²⁸. When applied as a dielectric layer in transistor applications, chitosan demonstrated encouraging outcomes. Chitosan, polyvinyl alcohol, and hydroxyethylcellulose polymer blends doped with varying percentages of 4-(2-pyridylazo)resorcinol monosodium salt hydrate were synthesized and their electrical characteristics investigated by Zainab J. Sweah and Fatima H. Malik²⁹. The produced thin films' current–voltage (I-V) characterization revealed ohmic behavior, and by raising the dopant ratio, which mirrored semiconductor behavior, the electrical conductivity was enhanced. Erol et al. evaluated the dielectric properties of chitosan-based ZnO nanocomposites³⁰. The blend of poly(2-(3,5-dichloroanilino)-2-oxoethyl 2-methyl-prop-2-enoate) (PDCOEMA) with chitosan (CS) was prepared. PDCOEMA-CS/ZnO nanocomposites were prepared by adding different concentrations ZnO nanoparticles. Impedance and dielectric characteristics of PDCOEMA-CS/ZnO nanocomposites were studied. They found that, the dielectric constant (ε′), dielectric loss (ε′′), and loss tan-gent (tanδ) have a frequency-dependent character. Also, the impedance (Z) decreases with increasing both frequency and doping concentration. It was suggested that the nanocomposites can be potential materials for high-frequency electronic devices such as MOS capacitors and MOSFET transistors. The dielectric and biological properties of novel chitosan-styrene-based nanocomposites containing TiO₂ nanowires were investigated by Erol et al.³¹. The results show that TiO₂ NWs impart insulating properties to CS. The produced nanocomposites showed good antibacterial activity and dielectric properties which suggested using these nanocomposites as an alternative to non-biodegradable packaging materials. Erol et al. studied the thermal, dielectric, and antimicrobial properties of fluorinated methacrylate and chitosan-based nanocomposites reinforced with TiO₂ nanowires³². The results proved that the nanocomposites showed enhanced properties. Novel nanocomposites of chitosan-based blend containing LaB₆ are prepared. The dielectric, and biological properties were investigated by Erol et al.³³. LaB₆ NPs increased the dielectric properties of the nanocomposites which suggested using them in electronic devices. The determined biological properties indicate that the CS-based nanocomposites can be used as biomaterials.

Many researchers have been interested in fused pyrimidine derivatives for many years because of its significant biological and chemotherapeutic properties. Numerous biological activities, including antibacterial, analgesic, anti-inflammatory, anticancer, and antitumor properties, have been documented for nitrogen-containing six-membered heterocycles and their fused derivatives, such as pyrimidine^34,35. Pyrimidine and pyrrolorings combine to create planar, stiff, and fused ring structures in a broad class of compounds known as pyrrolopyrimidines (PP)^{36,37,38,39,40,41,42}. Numerous pyrrolopyrimidines are known to have antifungal and antimicrobial properties^43,44,45. The antibacterial activity of pyrrolo[2,3-d]pyrimidine scaffold was investigated by Sun et al. ⁴⁶. New pyrrolo[2,3-d]pyrimidine attached to 1,3,4-oxadiazole–1,2,3-triazole conjugates were created and described by Boddu et al.⁴⁷. They investigated the synthetic chemicals' strong antibacterial properties. By condensing substituted benzaldehydes and 4-aminopyrrolo[2,3-d]pyrimidine using a microwave aided synthesis. Laxman and Bhausaheb created some novel 4-aminopyrrolo[2,3-d]pyrimidine analogues with strong antibacterial activity⁴⁸. The antibacterial activity of Pyrrolo [3,2-d] pyrimidine derivatives against Salmonella, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus bacteria was assessed by Kouhkan et al.⁴⁹. As described above, chitosan compounds showed enhanced biological activity and electrical properties. Also, pyrrolopyrimidine moiety showed improved antimicrobial activity. To the best of our knowledge, no electrical studies have been conducted on pyrrolopyrimidine compounds. So, the main idea behind this project is to design a chitosan-based hydrogel that possesses antibacterial properties and can conduct electricity. Chitosan itself is a biocompatible polymer, making it suitable for creating a hydrogel. Additionally, the incorporation of the pyrrolopyrimidine group provides additional properties and alters the local environment of the polymer chain; thus, this modification affects both the microorganism activity and the conduction process in the gel. Therefore, biodegradability and dielectric properties of the hydrogel can be considered as two sides of the same coin. The biocompatibility of the material defines its functionality, whereas the dielectric property determines the behavior of the constructed hydrogel as an electrical unit. The said concept is significant not only for multifunctional materials used in medicine but also for specific bioengineering applications.

Experimental

Materials

Malononitrile, 3,5-dimethoxy benzaldehyde, and chitosan (medium molecular weight, Mw = 300 KDa, 85% degree of deacetylation) were obtained from Sigma-Aldrich, Egypt. Urea, potassium carbonate and glutraldehyde (25% aqueous solution) were purchased from Merck. Glacial acetic acid and absolute ethanol were analytical grade and provided from Sigma-Aldrich.

Instruments

Fourier transforms infrared (FTIR) spectroscopy

The FTIR was recorded using a Japanese Jascow FTIR-430. The data was measured in the spectral region of 4000 to 400 cm⁻¹.

Proton and carbon nuclear magnetic resonance (¹HNMR and ¹³CNMR)

¹HNMR and ¹³CNMR spectra were determined by empolying a JEOL EX-270 NMR Spectrometer.

Field emission scanning electron microscope (FESEM)

Surface images of pyrimidine modified chitosan hydrogel were taken by SEM, Quanta FEG-250.

Dielectric analysis

Dielectric measurements of the prepared samples were performed at room temperature and over the frequency range (50 Hz-5 MHz) using an LCR HiTester (Hioki 3532–50 LCR HiTESTER, Nagano, Japan). The electrode samples, with a surface area of about 2 × 2 cm and a thickness of 0.12 mm, were used for this measurement. The dielectric measurements have been carried out in the described experimental conditions using the prepared samples. Each dielectric spectrum refers to the measurement carried out for the particular sample under the stated frequency and temperature conditions. No replicate measurements were made, and there were no statistical error bars and standard deviations in the dielectric data.

Synthesis of 6-amino-4-(3,5-dimethoxyphenyl)-2-oxo-1,2-dihydropyrimidine-5-carbonitrile(1)

A mixture of 3,5-dimethoxybenzaldehyde (1.6 gm, 0.01 mol), malononitrile (0.6 gm, 0.01 mol), urea (0.6 gm, 0.01 mol), and potassium carbonate (4 gm, 0.03 mol) in absolute ethanol (50 ml) was refluxed for 3 h. The solid product was then filtered, washed several times and recrystallized from ethanol. The obtained pyrimidine compound (1) was characterized by FTIR, and ¹HNMR. Yield (61%). Melting point (Mp) = 126–128 °C. FTIR (KBr, cm⁻¹): 3441 (NH₂), 3345 (NH), 2102(C = N), 1664(C = O). ¹HNMR (DMSO-d₆, ppm): 3.43 (s, 6H, 2OCH₃), 5.6 (s, 1H, NH₂), 6.25–6.75 (m, 3 H, Ar–H),7.12(s, 1H,NH).

Synthesis of 4-(5-amino-4-(3,5-dimethoxyphenyl)-2-oxo-2,7-dihydro-1H-pyrrolo[2,3-d]pyrimidin-6-yl)butanal (2)

A mixture of pyrimidine compound (1) (2.72 gm, 0.01 mol) and glutaraldehyde (1 gm, 0.9 ml, 0.01 mol) in absolute ethanol was refluxed for 2 h and then cooled. After cooling, a precipitate was formed which was then filtered, washed with ethanol and dried to produce a yellow pyrrolopyrimidine compound (2). The synthesized compound was characterized by FTIR, ¹HNMR and ¹³CNMR. Yield (67%). Mp = 199–200 °C. FTIR (KBr, cm⁻¹): 3441 (NH₂), 3347 (NH), 1713(CHO), 1663 (C = O). ¹HNMR (DMSO-d₆, ppm): 1.24(d, 2H, J = 8.4 Hz, –CH₂-CHO), 1.75 (t, 2H, CH_{2 –} CH₂), 3.75 (s, 3H, OCH₃), 3.81 (s, 3H, OCH₃), 5.36 (s,1H,NH), 5.68 (s,2H,NH₂), 6.01–7.07 (m, 3 H, Ar–H),,9.65(t,1H,-CH₂-CHO), 9.92 (s,1H,NH) . ¹³CNMR (DMSO-d6): 32.02 (–CH₂-CHO), 40.51 (CH₂ – CH₂), 55.15, 59.14 (2OCH₃), 88.94 (C), 98.56(C), 104.25(C), 106.51(C), 106.5(C), 120.50(C), 125.41(c), 132.97(C), 152.99(C), 157.59(C), 161.88(CO), 182.45 (CHO).

Synthesis of pyrrolopyrimidine modified chitosan hydrogel (3)

Chitosan (1.5 g) in 0.03% acetic acid aqueous solution was mixed with a solution of pyrrolopyrimidine derivative (2) (1.5 g) in 25 ml of glacial acetic acid. The mixture was stirred at room temperature for 2 h. The obtained hydrogel was then put in a petri dish and let to dry at room temperature. The dried product was treated with a 1% acetic acid solution to remove any unreacted chitosan and then washed with 1% NaOH to neutralize any excess acetic acid. Finally, it was repeatedly washed with distilled water until the washing water had a pH of 7. A yellow product (pyrrolopyrimidine modified chitosan) was obtained in 90% yield. The resulting hydrogel was characterized with FTIR and FESEM.

Antimicrobial assay

Preparation of microbial suspensions

The agar diffusion method was used to assess the sample's antibacterial activity⁵⁰. Freshly prepared Czapek–Dox agar medium was used for the cultivation of fungal strains, whereas nutrient agar medium was used for the cultivation of bacterial strains. Each microbe cell solution was serially diluted while an inoculum of 1 × 10⁵ CFU/mL was adjusted. Petri dishes with a diameter of 10 cm were filled with 50 μl of each inoculum that had been adjusted to the appropriate prepared medium. A filter paper disc with a diameter of one centimeter was filled with twenty microliters of each sample (10 mg/ml). The diameter of the inhibition zone in millimeters shows that diffusion promoted microbial growth after all of the produced discs were placed onto the surface of the inoculated agar plates and the plates were kept at a low temperature of 4 °C for two hours before incubation. Three independent measurements were performed for the inhibition zone assay, and the results are presented as mean ± standard deviation. Clotrimazole (1 mg/ml) was employed in the antifungal tests, whereas amoxicillin trihydrate (10 µg/ml) and Epico (amoxicillin) were the conventional antibacterial agents. For bacteria, the plates were incubated for 24 h at 35 °C. Conversely, yeast and fungal plates were incubated at 30 °C for 24 and 72 h, respectively. The prior conditions were previously recorded⁵¹.

Results and discussion

Synthesis of 6-amino-4-(3,5-dimethoxyphenyl)-2-oxo-1,2-dihydropyrimidine-5-carbonitrile(1)

The synthesized pyrimidine compound (1) is prepared by a condensation reaction of 3,5-dimethoxy benzaldehyde, malononitrile, and urea in absolute ethanol and in presence of potassium carbonate as a base, as represented in Scheme 1. The mechanism of formation of the pyrimidine compound is shown in Scheme 2. The structure of the newly synthesized pyrimidine derivative is characterized by FTIR, and ¹HNMR.

FTIR

FTIR of the prepared pyrimidine (1) is shown in Fig. 1. As illustrated from the figure, there is a band at 3441 cm⁻¹ corresponding to the stretching vibrations of amino group (-NH₂). The -NH group vibrations appear at 3345 cm⁻¹. The band centered at 3007 cm⁻¹ is related to the stretching vibrations of the unsaturated = CH group. The two bands located at 2965 cm⁻¹ and 2843 cm⁻¹ are attributed to the asymmetric and symmetric stretching vibrations of the saturated -CH group. The nitrile group (CN) stretching vibrations are represented at 2188 cm⁻¹. The band illustrated at 1668 cm⁻¹ is corresponding to the carbonyl group stretching vibrations. The C = C stretching vibration is observed at 1600 cm⁻¹.The band noted at 1529 cm⁻¹ is shown for the stretching vibration of the C = N group of pyrimidine moiety. The phenyl ring stretching vibration is observed at 1456 cm⁻¹. The appearance of these bands proves the correct structure of the formed pyrimidine compound. The obtained data is in well agreement with that obtained by Adam et al.⁵²

¹HNMR

The structure of pyrimidine derivative (1) is proved through ¹HNMR. ¹HNMR shows the presence of the signal of -NH₂ group at 5.6 ppm, and the signal of -NH group at 8.1 ppm. The results obtained from FTIR, and ¹HNMR prove the correct structure of the synthesized pyrimidine compound (1).

Synthesis of 4-(5-amino-4-(3,5-dimethoxyphenyl)-2-oxo-2,7-dihydro-1H-pyrrolo[2,3-d]pyrimidin-6-yl)butanal (2)

The synthesized pyrrolopyrimidine derivative (2) is prepared through reaction of the parent pyrimidine compound (1) with glutraldehyde in absolute ethanol and reflux for 2 h, as illustrated in Scheme 1. The reaction mechanism of the formation of pyrrolopyrimidine compound is represented in Scheme 2. The compound was characterized by FTIR, ¹HNMR and ¹³CNMR.

FTIR

FTIR of the pyrrolopyrimidine compound (2) reveals the presence of a band at 3441 cm⁻¹ corresponding to the -NH₂ group stretching vibration, as shown in Fig. 1. The stretching vibration of the -NH group appears at 3347 cm⁻¹. The unsaturated = CH stretching vibration is observed at 3005 cm⁻¹. The asymmetric and symmetric stretching vibrations of the saturated -CH group are located at 2919 cm⁻¹ and 2841 cm⁻¹, respectively. The band corresponding to the aldehyde group (CHO) stretching vibrations appears at 1713 cm⁻¹, whereas the band appears at 1664 cm⁻¹ is due to the carbonyl group (C = O) stretching vibrations present in the pyrimidine moiety. The C = C stretching vibration is centered at 1608 cm⁻¹.The band at 1539 cm⁻¹ is observed for the stretching vibration of the C = N group of pyrimidine. The band observed at 1471 cm⁻¹ is attributed to the phenyl ring stretching vibration. The figure also illustrated the absence of a band corresponding to the nitrile group (CN) vibration indicating the success of the cyclization reaction and the formation of the pyrrol ring. The appearance of all these bands and the absence of the band of the nitrile group prove the correct structure of the compound. The obtained data is in well agreement with that obtained by Sayed et al.⁵³.

¹HNMR and ¹³CNMR

¹HNMR shows the presence of signals at 1.24 ppm, and 1.75 ppm corresponding to the two methylene (-CH₂) group of glutraldehyde. The signal of -NH group in the five membered ring appears at 5.38 ppm. The amino group signal is present at 5.68 ppm, The aldehyde group proton appears at 9.65 ppm. The signal present at 9.92 ppm is attributed to -NH group present in the six-membered ring.

¹³C NMR (DMSO-d₆): the two carbons of the two methylene groups appear at 32.02 ppm, and 40.51 ppm. The carbonyl (C = O) carbon appears at 161.88 ppm. The aldehyde (CHO) carbon appears at 182.45 ppm. The obtained results prove the correct structure of the prepared compound.

synthesis of pyrrolopyrimidine-modified chitosan hydrogel (3)

Pyrrolopyrimidine derivative (2) reacts with chitosan in an aqueous medium and in presence of glacial acetic acid at room temperature for 2 h as shown in Scheme 1. The reaction mechanism of the formation of pyrrolopyrimidine-modified chitosan hydrogel is illustrated in Scheme 2. . The product pyrrolopyrimidine modified chitosan hydrogel (3) is characterized by both FTIR and FESEM.

FTIR

Figure 1c illustrates the FTIR of pyrrolopyimidine modified chitosan hydrogel (3). As observed from the figure, there is a broad band at 3560 cm⁻¹ corresponding to the stretching vibrations of the hydroxyl groups of chitosan, which is in well agreement with the data obtained by Vijayalakshmi et al.⁵⁴. The band located at 1688 cm^-1 is attributed to the carbonyl group (C = O) of the pyrimidine moiety. The condensation reaction of the aldehyde (CHO) group of pyrroloprimidine derivative (2) and the amino (NH₂) group of chitosan leads to the formation of imino (N = CH) group. The figure reveals the presence of a band at 1640 cm⁻¹ corresponding to the imino group stretching vibration. The band observed at 1577 cm⁻¹ is corresponding to the phenyl ring stretching vibration in the pyrrolopyrimidine moiety. The appearance of these bands indicates that the hydrogel is successfully prepared (Figs. 2, 3, 4).

FESEM

The surface morphology of the prepared pyrrolopyrimidine modified chitosan hydrogel is illustrated in Fig. 5. The images show that the hydrogel has flake-like structure with a uniform size. The surface contains some voids irregularly distributed between the flakes. It has been reported by Sutharsan et al. that the pristine chitosan has flat surface without any voids⁵⁵. The variation in the surface morphology of both pure chitosan and its hydrogel indicates the success of the modification reaction and the formation of the new hydrogel.

Dielectric study

Dielectric relaxation and conductivity behavior of pyrrolopyrimidine-modified chitosan hydrogel were investigated as a function of frequency and temperature and compared with the corresponding pure chitosan network. At all temperatures, both the dielectric loss and dielectric constant of pure and modified chitosan decrease sharply with increasing frequency in the low-frequency regime and then approach almost frequency-independent plateaus at higher frequencies, reflecting the transition from electrode/interfacial polarization and space-charge contributions to dipolar and bulk polarization processes within the polysaccharide chains. In pure chitosan, very large values of dielectric loss and permittivity are observed at low frequency, especially at elevated temperatures, indicating strong Maxwell–Wagner–Sillars interfacial polarization associated with trapped charges and mobile ions along the hydroxyl and amino groups of the backbone. Incorporation of the pyrrolopyrimidine moiety markedly reduces the low-frequency dielectric loss but maintains relatively high permittivity, which suggests that the heteroaromatic segment restricts long-range ionic drift while preserving local dipolar orientation originating from polar functional groups in the modified chains. The suppression of dielectric loss in the modified hydrogel becomes more evident at higher temperatures, implying that the new cross-linking environment and possible π–π interactions between pyrrolopyrimidine rings may hinder charge accumulation at interfaces and improve energy-storage behavior by decreasing dissipative pathways^56,57,58,59.

The temperature dependence of the dielectric response shows that increasing temperature enhances both dielectric constant and loss at low frequencies for pure and modified chitosan, consistent with increased segmental mobility, thermal activation of charge carriers, and facilitation of orientational polarization. However, the rate of increase with temperature is less pronounced in the modified hydrogel, reflecting a more constrained network in which thermally activated motion of dipoles and ions is partially suppressed by the pyrrolopyrimidine units. This behavior indicates that the modification introduces additional cross-linking sites and stronger intermolecular interactions that stabilize the hydrogel matrix against thermal disordering. Consequently, the pyrrolopyrimidine-modified chitosan hydrogel exhibits a more thermally stable dielectric response, with reduced dielectric loss and a smoother decay of permittivity over the investigated frequency domain compared with pure chitosan, which is beneficial for applications requiring stable performance over a wide temperature range^60,61.

The ac conductivity spectra of pure and modified chitosan hydrogels, plotted as log conductivity versus log frequency, further clarify the role of the pyrrolopyrimidine modification. For pure chitosan, the conductivity increases monotonically with frequency at all temperatures, displaying the typical behavior of disordered polymer electrolytes where charge transport is dominated by hopping of localized ions and follows a power-law dependence on frequency in the dispersive regime. The magnitude of conductivity is significantly enhanced at high temperatures, reflecting thermally activated motion of charge carriers along the hydrated chitosan chains and through amorphous regions. In contrast, the modified chitosan hydrogel exhibits a characteristic minimum in conductivity at intermediate frequencies, separating a low-frequency regime affected by electrode polarization and blocking of mobile ions from a high-frequency regime where hopping and segmental-assisted transport dominate. The presence of this minimum and the overall lower conductivity values at low and intermediate frequencies indicate that pyrrolopyrimidine groups may introduce localized potential barriers or trapping sites that restrict long-range ion migration, thereby decreasing leakage and improving the insulating character of the hydrogel. At higher frequencies, the conductivity of the modified system increases and approaches values comparable to, or slightly lower than, those of pure chitosan, suggesting that local hopping processes between neighboring sites still occur efficiently within the more rigid network. Overall, the dielectric and conductivity results confirm that pyrrolopyrimidine modification tunes the balance between polarization mechanisms and charge transport in chitosan hydrogels, yielding materials with reduced dielectric loss, controlled conductivity, and enhanced suitability for electro-active, sensing, and energy-storage applications^62,63 (Figs. 6 and 7).

Antimicrobial activity

A panel of microbial strains is used to assess each of the novel compounds as antibacterial and antifungal agents. They are tested against two yeast-like fungi (Candida albicans 10,231 and Candida tropicalis 750), two gram-positive bacteria (Bacillus cereus 33,018 and Bacillus subtilis 6633), and two gram-negative bacteria (Pseudomonas aeruginosa 9027 and Salmonella typhimurium 14,028). Based on the minimum inhibitory concentration (MIC) values in Table 1, the antibacterial activity of the target compounds (1–3) is compared with that of amoxicillin, whose MICs ranged between 6–12 µg/mL against the bacterial strains. It is evident that amino pyrimidine derivative (1) reveals most potent antibacterial activity against Escherichia coli, A. niger and A. flavus. While, it shows equipotent activity to amoxicillin against the other strains. On the other hand, the conversion of (1) to (2) leads to a significant increase in antibacterial activity against most strains with MIC value 12.5 µg/mL than amoxicillin. The antimicrobial activity of pure chitosan shows low activity towards bacterial and fungal strains. By modification of chitosan with pyrrolopyrimidine compound, the antibacterial activity increased towards different bacterial strains, but it shows no activity against fungal strains such as C. albicans, C. tropical, A. niger and A. flavus. Figure 8 shows the inhibition zones formed by the tested compounds. The possible mechanism for inhibition of the microbes is illustrated in Fig. 9. The prepared compounds can resist microorganisms through its hetero-atoms (O and N), which can be well adsorbed and restrict the growth of the microbes. Different actions can be done by the prepared compounds that can disrupt the growth of bacterial and fungal strains⁶⁴. The cell wall and the cell membrane can be damaged causing increasing the permeability of the tested compounds preventing reproduction of the cells. The prepared compounds can inhibit DNA, and proteins through the creation of reactive oxygen species. This can result in destroying the components of the cell leading to death of the cells. The substances may impede vital biochemical functions in the microorganisms by interfering with particular metabolic pathways⁶⁴. However, these mechanisms are proposed based on the literature and were not experimentally validated in the present study. The obtained results indicate that the synthesized hydrogel may have potential applications in biomedical and pharmaceutical fields, particularly in antimicrobial wound-care materials and drug-delivery systems, owing to their antimicrobial activity. Their dielectric properties may also make them of interest for selected sensing and bioelectronic applications.

Conclusion

To summarize, the successful synthesis of the pyrrolopyrimidine-modified chitosan hydrogel via imine formation between the aldehyde-modified pyrrolopyrimidine derivative and the amine groups of chitosan has resulted in a multifunctional material, with changes in its dielectric, alternating-current electrical conductivity, and antimicrobial properties compared to pure chitosan. The pyrrolopyrimidine modification lowers low-frequency dielectric losses and stops long-range charge transfer, while keeping a detectable dielectric response in the tested frequency range and temperature ranges. The modified hydrogel also has improved antimicrobial activity compared to pure chitosan but has low activity against fungi. Apparently, the presence of two functions at the same time—antimicrobial functionality and controllable characteristics of electric and dielectric properties—informs the prospects of the material for further research and application in antimicrobial sensing, bioelectronics, and biomedicine. However, these applications were not tested directly in this work. Evaluation of the hydrogel properties requires conducting more research on its application and properties.

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

References

1. Wróblewska-Krepsztul, J. et al. Recent progress in biodegradable polymers and nanocomposite based packaging materials for sustainable environment. Int. J. Polym. Anal. Charact. 23, 383–395 (2018).

   Article  Google Scholar 

2. Wróblewska-Krepsztul, J., Rydzkowski, T., Michalska-Pożoga, I. & Thakur, V. K. Biopolymers for biomedical and pharmaceutical applications: Recent advances and overview of alginate electrospinning. Nanomaterials 9, 404 (2019).

   Article  PubMed  PubMed Central  Google Scholar 

3. Prashanth, S. et al. Structural, electrical and dielectric properties of chitosan/polyaniline/vanadium-pentoxide hybrid nanocomposites. J. Mol. Struct. 1267, 133600 (2022).

   Article  Google Scholar 

4. Pal, P., Pal, A., Nakashima, K. & Yadav, B. K. Applications of chitosan in environmental remediation: A review. Chemosphere 266, 128934 (2021).

   Article  PubMed  Google Scholar 

5. Liu, M., Zhou, Y., Zhang, Y., Yu, C. & Cao, S. Physicochemical, mechanical andthermal properties of chitosan films with and without sorbitol. Int. J. Biol. Macromol. 70, 340–346 (2014).

   Article  PubMed  Google Scholar 

6. Yoshida, C. M. P. et al. Effect of chitosan and aloe vera extract concentrations onthe physicochemical properties of chitosan biofilms. Polymers 13, 1187 (2021).

   Article  PubMed  PubMed Central  Google Scholar 

7. Friedman, A. J. et al. Antimicrobial and anti-inflammatoryactivity of chitosan-alginate nanoparticles: A targeted therapy for cutaneouspathogens. J. Invest. Dermatol. 133, 1231–1239 (2013).

   Article  PubMed  Google Scholar 

8. Lopez-Moya, F., Suarez-Fernandez, M. & Lopez-Llorca, L. V. Molecular mechanisms of chitosan interactions with fungi and plants. Int. J. Mol. Sci. 20, 332 (2019).

   Article  PubMed  PubMed Central  Google Scholar 

9. Mujtaba, M. et al. Understanding the effects of copolymerized cellulose nanofibers and diatomitenanocomposite on blend chitosan films. Carbohydr. Polym. 271, 118424 (2021).

   Article  PubMed  Google Scholar 

10. Bagheri, M., Validi, M., Gholipour, A., Makvandi, P. & Sharifi, E. Chitosan nanofiberbiocomposites for potential wound healing applications: Antioxidant activity with synergic antibacterial effect. Bioeng. Transl. Med. 7, e10254 (2021).

    Article  PubMed  PubMed Central  Google Scholar 

11. Sharifi, E. et al. Cell loaded hydrogel containing Ag-dopedbioactive glass–ceramic nanoparticles as skin substitute: Antibacterial properties,immune response, and scarless cutaneous wound regeneration. Bioeng. Transl. Med. 7, e10386 (2022).

    Article  PubMed  PubMed Central  Google Scholar 

12. Zafari, M. et al. Physical and biological properties of blend-electrospun polycaprolactone/chitosan-based wound dressings loaded With N-decyl-N, Ndimethyl-1-decanaminium chloride: An in vitro and in vivo study. Biomed. Mater Res. 108B, 3084–3098 (2020).

    Article  Google Scholar 

13. Nasaj, M. et al. Factors influencing the antimicrobial mechanism of chitosan action and its derivatives: A review. Int. J. Biol. Macromol. 277, 134321 (2024).

    Article  PubMed  Google Scholar 

14. Tsai, G.-J. & Su, W.-H. Antibacterial activity of shrimp chitosan against Escherichia coli. J. Food Prot. 62, 239–243 (1999).

    Article  PubMed  Google Scholar 

15. Chung, Y.-C. & Chen, C.-Y. Antibacterial characteristics and activity of acid-soluble chitosan. Biores. Technol. 99(8), 2806–2814 (2008).

    Article  Google Scholar 

16. Young, D. H. & Kauss, H. Release of calcium from suspension-cultured glycine max cells by chitosan, other polycations, andpolyamines in relation to effects on membrane permeability. Plant physiol. 73, 698–702 (1983).

    Article  PubMed  PubMed Central  Google Scholar 

17. Goy, R. C., de Britto, D. & Assis, O. B. G. A review of the antimicrobial activity of chitosan. Polímeros 19, 241–247 (2009).

    Article  Google Scholar 

18. Erol, I., Hazman, Ö., Aksu, M. & Bulut, E. Synergistic effect of ZnO nanoparticles and hesperidin on the antibacterial properties of chitosan. J. Biomater. Sci. Polym. Ed. 33, 1973–1997 (2022).

    Article  PubMed  Google Scholar 

19. Artun, H., Hazman, Ö., Tillayev, S. & Erol, I. Preparation of nanocomposite based on chitosan-PDCOEMA containing biosynthesized ZnO: Biological and thermal characterization. Int. J. Biol. Macromol. 242(Pt 1), 124753 (2023).

    Article  PubMed  Google Scholar 

20. Khamidov, G., Hazman, Ö., Hasanovich, M. N. & Erol, I. Evaluation of thermal, antimicrobial, antioxidant, anticancer, and wound healing properties of GO-Ag containing nanocomposites based on CS- PPFOEMA blend. J. Drug Deliv. Sci. Technol. 91, 105258 (2024).

    Article  Google Scholar 

21. Erol, I., Hazman, Ö., Khamidov, G. & Savrık, M. Improved physical, thermal, and biological properties of green synthesized Ag-containing nanocomposites of a novel chitosan-based blend. J. Mol. Liq. 392(Part 1), 123506 (2023).

    Article  Google Scholar 

22. Raafat, D., von Bargen, K., Haas, A. & Sahl, H.-G. Insights into the mode of action of chitosan as an antibacterial compound. Appl. Environ. Microbiol. 74(12), 3764–3773 (2008).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

23. Guarnieri, A. et al. Antimicrobial properties of chitosan from different developmental stages of the bioconverter insect Hermetiaillucens. Sci. Rep. 12, 8084 (2022).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

24. Aziz, S. B. & Abidin, Z. H. Z. Ion-transport study in nanocomposite solid polymer electrolytes based on chitosan: Electrical and dielectric analysis. J. Appl. Polym. Sci. 132, app.1774 (2015).

    Article  Google Scholar 

25. Abusnina, H., El-Ghamaz, N. A. & Gaml, E. A. AC electrical properties, thermal analysis and emission spectrum of chitosan polymer. Sci. J. Damietta Fac. Sci. 15, 98–105 (2025).

    Google Scholar 

26. Saengkaew, P., Chantanachai, K., Cheewajaroen, K. & Nimsiri, W. Characterization and electrical properties of chitosan for waste water treatment. AIP Conf. Proc. 1728, 020031. https://doi.org/10.1063/1.4946081 (2016).

    Article  Google Scholar 

27. Naveen, C. & Muthuvinayagam, M. Studies on electrical properties of chitosan-PVA based biopolymer electrolytes for electrochemical devices. J. Polym. Res. 30, 353 (2023).

    Article  Google Scholar 

28. Saadi, M. et al. Morphological, optical, and dielectric properties of chitosan biopolymer thin films synthesized by spray pyrolysis. ACS Omega 10, 46384–46392 (2025).

    Article  PubMed  PubMed Central  Google Scholar 

29. Sweah, Z. J. & Malik, F. H. Preparation and study the electrical properties of chitosan, hydroxyethylcellulose, and polyvinyl alcohol polymer blend doped with different ratios of 4-(2-pyridylazo)resorcinol monosodium salt hydrate. MJPS 8, 49–56 (2021).

    Article  Google Scholar 

30. Erol, I. et al. Dielectric properties of chitosan-based ZnO nanocomposites for high-frequency electronic devices. Polym. Bull. 82, 1223–1238 (2025).

    Article  Google Scholar 

31. Erol, I., Khamidov, G., Hazman, Ö. & Çifci, C. Hydrothermal synthesis of novel chitosan-styrene-based nanocomposites containing TiO₂ nanowires: Investigation of thermal, dielectric and biological properties. Mater. Today Commun. 41, 110726 (2024).

    Article  Google Scholar 

32. Erol, I., Khamidov, G., Uktamjon, R., Davlat, T. & Tillayev, S. Enhanced thermal, dielectric, and antimicrobial performance of fluorinated methacrylate and chitosan-based nanocomposites reinforced with TiO₂ nanowires. Cellulose 32, 9429–9450 (2025).

    Article  Google Scholar 

33. Erol, I., Hazman, Ö., Aksu, M. & Uygur, I. Novel bionanocomposites of chitosan-based blend containing LaB₆: Thermal, dielectric, and biological properties. Polym. Adv. Technol. 34, 2721–2738 (2023).

    Article  Google Scholar 

34. Chaudhari, N. D. & Shashidhar, B. V. Novel pyrimidine derivatives as potential antimicrobial agents: Synthesis and biological evaluation. Int. J. Pharm. Sci. Res. (IJPSR) 15, 450–454 (2024).

    Google Scholar 

35. Hosny, M. A., Zaki, Y. H., Mokbel, W. A. & Abdelhamid, A. O. Synthesis, characterization, antimicrobial activity and anticancer of some new pyrazolo [1,5-a] pyrimidines and pyrazolo[5,1-c]1,2,4-triazines. Med. Chem. 16, 750–760 (2020).

    Article  PubMed  Google Scholar 

36. Roopashree, R., Swaroop, T. R., Shivaprasad, C. M., Jagadish, S. & Rangappa, K. S. Synthesis and cytotoxic studies of pyrrolopyrimidine derivatives. Asian J. Chem. 33, 1855–1860 (2021).

    Article  Google Scholar 

37. Wang, L. et al. Concise synthesis of pyrrolo[2,3-d]pyrimidine derivatives via the Cu-catalyzed coupling reaction. Green Chem. Lett. Rev. 10, 42–47 (2017).

    Article  Google Scholar 

38. Prieur, V., Heindler, N., Rubio-Martínez, J., Guillaumet, G. & Pujol, M. D. One-pot synthesis of 4-aminated pyrrolo[2,3-d]pyrimidines from alkynylpyrimidines under metal-catalyst-free conditions. Tetrahedron 71, 1207–1214 (2015).

    Article  Google Scholar 

39. Komkov, A. V., Sukhanova, A. A., Menchikov, L. G. & Zavarzin, I. V. o-Aminopyrimidine aldehydes and ketones: Synthesis and use as precursors to fused pyrimidines. Chem Heterocycl Com. 58, 547–566 (2022).

    Article  Google Scholar 

40. Sajadikhah, S. S. & Zare, A. Synthesis of pyrrolo[2,3-d]pyrimidines (microreview). Chem. Heterocycl. Compd. 55, 1168–1170 (2019).

    Article  Google Scholar 

41. Lee, J. H. & Lim, H. S. Solid-phase synthesis of tetrasubstitutedpyrrolo[2,3-d]pyrimidines. Org. Biomol. Chem. 10, 4229–4235 (2012).

    Article  PubMed  Google Scholar 

42. Liu, M. et al. Ligand-enabled. C6-selective C–H arylation of pyrrolo[2,3-d]pyrimidine derivatives with Pd catalysts: An approach to the synthesis of EGFR inhibitor AEE-788. J. Org. Chem. 89, 8023–8034 (2024).

    Article  PubMed  Google Scholar 

43. El-Hameed, R. H. A. et al. Synthesis of novel pyrroles and fused pyrroles as antifungal and antibacterial agents. J. Enzym. Inhib. Med. Ch. 36, 2183–2198 (2021).

    Article  Google Scholar 

44. Hilmy, K. M. H., Khalifa, M. M. A., Hawata, M. A. A., Keshk, R. M. A. & El-Torgman, A. A. Synthesis of new pyrrolo[2,3-d]pyrimidine derivatives as antibacterial and antifungal agents. Eur. J. Med. Chem. 45, 5243–5250 (2010).

    Article  PubMed  Google Scholar 

45. Patel, J. L. et al. Design, synthesis, in vitro, and in silico evaluations of 1,3,4-oxadiazole derivatives linked to the pyrrolo[2,3-d]pyrimidine moieties as potent antimicrobial targets. Chem. Select. 9, e202400117 (2024).

    Google Scholar 

46. Sun, Z. et al. Recent advances in the antimicrobial application of the pyrrolo[2,3-d]pyrimidine scaffold: Innovative synthetic strategies, structural diversification, and bioactivity evaluation. RSC Adv. 15, 29627–29645 (2025).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

47. Boddu, V. B. et al. Unveiling antimicrobial potential of novel pyrrolo[2,3-d]pyrimidine Linked 1,3,4-oxadiazole–1,2,3-triazole conjugates through synthesis, in vitro, and in silico studies. Chem. Select 10, e03569 (2025).

    Google Scholar 

48. Laxman, G. & Bhausaheb, H. Microwave-assisted synthesis and antimicrobial profiling of new pyrrolo-pyrimidine analogues. Asian J. Chem. Int. Peer Rev. Res. J. Chem. 35, 2210–2214 (2023).

    Google Scholar 

49. Kouhkan, M., Javahershenas, R. & Khalafy, J. Biological evaluation of pyrrolo [3, 2-d] pyrimidine derivatives as antibacterial agents against pathogenic bacteria. Biotechnol. Bioprocess. 2, 054 (2021).

    Article  Google Scholar 

50. Wilkins, T. D., Holdeman, J. J., Abramson, I. J. & Moore, W. E. C. Standardized single-disc method for antibiotic susceptibility testing of anaerobic bacteria. Antimicrob. Agents Chemother. 1, 451–459 (1972).

    Article  Google Scholar 

51. Soltan, M. M., Mahfouz, S., Motawe, F. H., Karam, E. A. & El-Hagrassi, A. Insight on olive oil maceration and supercritical CO2 in extracting rosemary essential oil. Sci. Rep. 14, 29730 (2024).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

52. Adam, R. W., Al-Labban, H. M. Y., Kadhim, I. N. & Aljanaby, A. A. J. Synthesis, characterization, and antibacterial activity of some new pyrimidine derivatives from chalcone derivatives. Drug Invent. Today 11, 1732 (2019).

    Google Scholar 

53. Sayed, A. I. et al. Novel pyrrolopyrimidine derivatives: Design, synthesis, molecular docking, molecular simulations and biological evaluations as antioxidant and anti-inflammatory agents. J. Enzyme Inhib. Med. Chem. 37, 1821–1837 (2022).

    Article  PubMed  PubMed Central  Google Scholar 

54. Vijayalakshmi, K., Devi, B. M., Sudha, P. N., Venkatesan, J. & Anil, S. Synthesis, characterization and applications of nanochitosan/sodium alginate/microcrystalline cellulose film. J. Nanomed. Nanotechnol. 7, 1000419 (2016).

    Google Scholar 

55. Sutharsan, J., Boyer, C. A. & Zhao, J. Development and characterization of chitosan edible filmincorporated with epoxy-activated agarose. JSFA Rep. 2, 613–622 (2022).

    Google Scholar 

56. Mostafa, A. M. et al. Nickel oxide nanoparticles embedded in polymer-matrix nanocomposite prepared by nanosecond laser ablation method for optoelectronic applications. Radiat. Phys. Chem. 226, 112262 (2025).

    Article  Google Scholar 

57. Alkallas, F. H. et al. Structural, optical, and dielectric characterization of NiO nanoparticles and their integration into PVA/SA blends for enhanced nanocomposite properties. J. Electron. Mater. 53, 6209–6220 (2024).

    Article  ADS  Google Scholar 

58. Alkallas, F. H. et al. Achieving effective performance of silicon solar cell through electrosprayed MgF2 antireflection coating. Ceram. Int. 50, 28724–28734 (2024).

    Article  Google Scholar 

59. Trabelsi, A. B. G. et al. Effect of CuO nanoparticles on the optical, structural, and electrical properties in the PMMA/PVDF nanocomposite. Micromachines 14, 1195 (2023).

    Article  PubMed  PubMed Central  Google Scholar 

60. Alkallas, F. H. et al. Effect of laser repetition rate parameter in pulsed laser ablation for synthesis Li4Ti5O12 polyether sulfone nanocomposite for optoelectronic applications. Surf. Interfaces 41, 103245 (2023).

    Article  Google Scholar 

61. ElFaham, M. M., Mostafa, A. M. & Mwafy, E. A. The effect of reaction temperature on structural, optical and electrical properties of tunable ZnO nanoparticles synthesized by hydrothermal method. J. Phys. Chem. Solids 154, 110089 (2021).

    Article  Google Scholar 

62. Mostafa, A. M., Lotfy, V. F., Mwafy, E. A. & Basta, A. H. Influence of coating by Cu and Ag nanoparticles via pulsed laser deposition technique on optical, electrical and mechanical properties of cellulose paper. J. Mol. Struct. 1203, 127472 (2020).

    Article  Google Scholar 

63. Mostafa, A. M., Mwafy, E. A., Lotfy, V. F. & Basta, A. H. Optical, electrical and mechanical studies of paper sheets coated by metals (Cu and Ag) via pulsed laser deposition. J. Mol. Struct. 1198, 126927 (2019).

    Article  Google Scholar 

64. Abd El-Gawad, W. M., El-Masry, H. M. & Zidan, T. A. Valorization of novel bifunctional waterborne coatings with UV irradiation resistance and antimicrobial activity. Sci. Rep. 15, 32238 (2025).

    Article  ADS  Google Scholar 

Download references

Funding

Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). There was no funding.

Author information

Authors and Affiliations

1. Therapeutic Chemistry Department, National Research Centre, 33 El Bohouth St., Dokki, Giza, 12622, Egypt

   Amina A. Abd El-Gwaad

2. Polymers and Pigments Department, National Research Centre, 33 El Bohouth St., Dokki, Giza, 12622, Egypt

   T. A. Zidan

3. Microbial Chemistry Department, National Research Centre, 33 El Bohouth St., Dokki, Giza, 12622, Egypt

   Eman A. Karam

4. Physical Chemistry Department, National Research Centre, 33 El Bohouth St., Dokki, Giza, 12622, Egypt

   Eman A. Mwafy

Authors

1. Amina A. Abd El-Gwaad
2. T. A. Zidan
3. Eman A. Karam
4. Eman A. Mwafy

Contributions

Amina A. Abd El-Gwaad helps in methodology, discussion of the results and writing. T.A. Zidan puts the scientific idea, methodology, discussion of the results, writing and publishing the manuscript. Eman A. Karam does the antimicrobial activity work and writes it. Eman A. Mwafy does the electrical studies, discusses it and writing.

Corresponding author

Correspondence to T. A. Zidan.

Ethics declarations

Competing interests

The authors declare that there are no competing interests.

Additional information

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and permissions

About this article

Cite this article

El-Gwaad, A.A.A., Zidan, T.A., Karam, E.A. et al. A novel, multifunctional pyrrolopyrimidine-modified chitosan hydrogel for potential applications with enhanced electrical characteristics and antimicrobial activity. Sci Rep 16, 34061 (2026). https://doi.org/10.1038/s41598-026-73222-2

Download citation

• Received: 13 April 2026

• Accepted: 21 September 2026

• Published: 26 October 2026

• Version of record: 26 October 2026

• DOI: https://doi.org/10.1038/s41598-026-73222-2

Keywords