Multifunctional CMC–Nanographene Oxide Hydrogels Couple Fluorophore-Free Cancer Cell Imaging with Antioxidant and Antimicrobial Activity

Background: The development of sustainable biomaterials that combine imaging capability with complementary biological functions without relying on incorporated drugs or exogenous fluorophores represents an attractive strategy for multifunctional biomedical platforms. Methods: Here, carboxymethyl cellulose (CMC) hydrogels reinforced with nanographene oxide (nGO) were developed by citric acid-mediated crosslinking using nGO contents of up to 3% (w/w) and evaluated for their physicochemical, electrochemical, and biological properties. Results: nGO exhibited a nanosheet morphology, a hydrodynamic diameter of 5.0 ± 0.2 nm, and a specific surface area of approximately 650 m2 g−1. Incorporation of nGO modified the hydrogel structure and reduced water uptake within the tested formulation window. The nanocomposite hydrogels maintained high cytocompatibility, with approximately 100% HeLa cell viability after 24 h. Confocal microscopy and quantitative fluorescence-intensity analysis demonstrated enhanced fluorescence relative to untreated cells, reaching approximately eightfold higher signal intensity and supporting proof-of-concept fluorescence-assisted visualization of HeLa cells without exogenous fluorescent probes. However, because only HeLa cells were evaluated and no cancer-specific targeting ligand was incorporated, these findings do not establish diagnostic specificity. The CMC–nGO hydrogels also exhibited radical-scavenging activity of up to 96.5% and antimicrobial activity against Escherichia coli and Candida albicans, with maximum inhibition zones of 12.9 and 9.2 mm, respectively. In addition, nGO incorporation modified the electrochemical response of graphite electrodes, supporting the multifunctional character of the platform. Conclusions: Overall, CMC–nGO hydrogels provide a sustainable, drug-free, and fluorophore-free biointerface combining fluorescence-assisted cell visualization with antioxidant, antimicrobial, and electrochemical functionalities. Further photophysical characterization, comparison with non-cancerous cervical cells, rheological and mechanical evaluation, and validation in advanced biological models are required to establish their potential for future bioimaging and biosensing applications.