Development, characterization and evaluation of tetracycline-HCL loaded (Poly-ε-caprolactone) nanoparticles against multidrug resistant Acinetobacter baumannii isolates

One of the most recent approaches against antibiotic resistance is the development of targeted drug molecules with nano-transport systems. In this study, tetracycline-HCl loaded poly-ε-caprolactone (PCL) nanoparticles were synthesised by double emulsion evaporation method to enhance the efficacy of antibiotics against multidrug resistant Acinetobacter baumannnii isolates. The average sizes of the synthesised nanoparticles were measured by dynamic light scattering (DLS), zeta potentials by polydispersity index (PDI) and electrophoretic light scattering (ELS). The encapsulation efficiency of the nanoparticles was determined indirectly by UV-Vis spectrophotometer, while drug loading capacity and response efficiency were determined on a dry weight basis. The surface functional groups of tetracycline-HCl loaded PCL nanoparticles (Tetra-PCL) were evaluated by Fourier transform infrared spectroscopy (FT-IR) and their surface morphology by scanning electron microscopy (SEM). The amount of antibiotic released from Tetra-PCL nanoparticles was determined by in vitro release assay and the antimicrobial activity of the nanoparticles was determined by microdilution technique. The cytotoxic effect of the nanoparticles was determined by the MTT assay using human dermal fibroblast (HDF) cells. As a result of the studies, the encapsulation efficiency of Tetra-PCL nanoparticles was calculated to be 71.70%, the drug loading capacity to be 34.06% and the response efficiency to be 60.14%. The average size, PDI and zeta potential values of the nanoparticles were determined to be 372.2±9.494, 0.568±0.039 and -1.37±0.129 mV, respectively. FT-IR analysis of Tetra-PCL nanoparticles revealed that the surface chemistry was PCL and some tetracycline-HCl was adsorbed on the surface. Morphological analysis of Tetra-PCL nanoparticles by SEM showed that their structures were spherical and the nanoparticles reduced the MIC of isolate A-2 (15.12 µg/mL) by 2-fold and of isolate A-3 (7.56 µg/mL) by 4-fold compared to the free antibiotic. In conclusion, the dose-dependent toxicity of Tetra-PCL nanoparticles was low and the synthesised nanoparticles were more effective against some isolates of A. baumannii than free Tetracycline-HCl.