Glucosamine functionalized multi-walled carbon nanotubes as potential antibacterial molecules.

Abstract

Antibiotic resistance represents a critical global health challenge driven by the widespread misuse of antimicrobials and the rapid evolution of multidrug-resistant pathogens. Conventional antibiotics are increasingly limited by poor stability, low bioavailability, toxicity, and reduced efficacy. This study investigates the potential of carbon nanotube-based nanocarriers to enhance antibiotic delivery and efficacy against resistant bacteria. Multi-walled carbon nanotubes were oxidized and functionalized with glucosamine, followed by loading with two antibiotics, ethacridine lactate and sulfamethoxazole, to form nanoconjugates. Characterization studies confirmed successful functionalization and drug loading. Thermogravimetric analysis indicated distinct weight losses corresponding to surface modifications, while Fourier transform infrared spectra verified amide bond formation and drug-nanocarrier interactions. Scanning electron microscopy revealed increased surface roughness and structural defects after functionalization. UV-Vis spectroscopy demonstrated high encapsulation efficiencies (85.37% for ethacridine lactate and 93.69% for sulfamethoxazole). Dynamic light scattering demonstrated hydrodynamic diameters ranging from 127 to 429 nm, moderate polydispersity, and stable negative zeta potentials (-17 to -23 mV), confirming colloidal stability. Biological evaluation against Gram-negative and Gram-positive bacteria demonstrated that drug-loaded nanoconjugates exhibited significantly enhanced antibacterial activity compared to free drugs and individual nanomaterials. The nanoconjugate EL-GA-OMC achieved complete (100%) bacterial inhibition across all tested bacterial strains, while SMX-GA-OMC showed significantly enhanced antibacterial activity compared to the drugs alone. Half-maximal inhibitory concentration (IC₅₀) analysis further confirmed increased potency, with EL-GA-OMC exhibiting the lowest IC₅₀ value (10.20 ± 0.19 µg/mL) against E. coli K1, and 10.74 ± 0.05 µg/mL against S. pneumoniae, indicating superior efficacy at reduced doses. Cytotoxicity analysis using human endothelial cells (HBEC-5i) revealed that nanoconjugates exhibited low cytotoxicity, in contrast to the significant toxicity observed with drug alone. Overall, these findings demonstrate that glucosamine-functionalized carbon nanotubes represent an effective drug delivery system that enhances antibacterial activity while exhibiting low cytotoxicity. These findings support the potential application of glucosamine-functionalized carbon nanotubes as antibiotic delivery platforms for the treatment of multidrug-resistant bacterial infections.