A novel, multifunctional pyrrolopyrimidine-modified chitosan hydrogel for potential applications with enhanced electrical characteristics and antimicrobial activity

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 ( 1 HNMR and 13 CNMR), 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.