Electrostatic adsorptive loading of ciprofloxacin and metronidazole on chitosan nanoparticles to prolong the drug delivery process with preserved antibacterial activities: formulation and characterization

This study presents the formulation and evaluation of chitosan-based homogeneous nanoparticles of ciprofloxacin (CP) and metronidazole (MTZ) with improved loading efficiency to enhance the controlled release of drug within the human body as well as for the enhancement of the antibacterial activity. The drug-loaded chitosan nanoparticles (CSNPs) were prepared using deacetylated chitosan extracted from shrimp shells. The characterization of the drug-loaded CSNPs were performed by FTIR, XRD, SEM and TEM analyses. The association efficiencies of the drug-loaded CSNPs were found to be 93% ± 3% and 89% ± 3% for ciprofloxacin and metronidazole, respectively. TEM analysis confirmed the formation of homogeneous nano-sized particles of 0.1-1.0, 0.3-1.3, and 0.4-1.5 nm for CSNPs, CP-CSNPs and MTZ-CSNPs, respectively, which elucidated the adsorptive loading of the drug molecules on the surface of the chitosan nanoparticles. A comparison of the surface charges of the above nanoparticles suggested that the electrostatic adsorption dominated the drug loading process. Both of the drug-loaded CSNPs showed sustained release of drugs after an initial rapid release in the <i>in vitro</i> release kinetic studies. Thus, the adsorption of drugs on the surface of CSNPs resulted in the sustained release of the drugs from CSNPs without encapsulation. Positive results of the antibacterial activities of the CP-loaded CSNPs (CP-CSNPs) against both Gram-positive and Gram-negative bacteria were observed.