Exploring potential of tobramycin complexes for combating biofilms: In silico and In vitro studies

Abstract

Nosocomial infections linked to medical implants, wound infections, and cystic fibrosis infections are mostly caused by biofilms linked to Pseudomonas aeruginosa. The development of biofilms on medical equipment continues to a growing health and financial burden with increased the risk of infections and patient morbidity associated with indwelling medical devices. Pseudomonas aeruginosa exhibited high antibiotic resistance, posing challenges for effective treatment of infections associated with medical implants. Therefore, our objective was to adopt a combinatorial approach for formulating antibiotic complexes for maximum eradication of biofilms associated with medical implants.In this study, we optimized the ratio of Tobramycin (TOB) complexes with complexing agents such as sodium bicarbonate (BC), β-cyclodextrin (β-CD), and ethylenediaminetetraacetic acid (EDTA). Further stability and flexibility of the complexes were examined through molecular docking and dynamics. Subculturing and gram staining were performed for the isolation and identification of Pseudomonas aeruginosa. The antibacterial activity was tested using the broth dilution method and well diffusion method to calculate the MIC (minimum inhibitory concentration) against Pseudomonas aeruginosa planktonic cells and biofilms, respectively. The MIC tests indicated that optimised complexes required a concentration of 8 μg/ml to eradicate both planktonic cells as well as biofilms. However, the TOB-BC-(β-CD)-EDTA complex showed lower optical density (OD) compared to other complexes exhibiting better biofilm inhibition. Subsequently a gel formulation using this optimised (TOB-BC-(β-CD)-EDTA) complex that could be applied to medical equipment or potentially converted into a film using different polymer concentrations was developed. The TOB-BC-(β-CD)-EDTA gel formulation was characterized for pH, viscosity, spread-ability, % yield, moisture content, drug content, in-vitro drug diffusion, and antibacterial efficacy assay. Among all batches, F2 demonstrated the highest % drug diffusion after 24 hours and fit well to the Korsmeyer-Peppas kinetic model. The viscosity of the F2 batch remained within acceptable limits and was stable at 40 ± 0.5 ºC and 75.0 ± 5% RH. The gel efficiently delivered antimicrobial drugs to bacteria within biofilms. In conclusion, tobramycin complex gel showed promising potential for addressing infections related to biofilms on medical implants.