Antibiotic drug delivery with two new cationic Schiff base-modified chitosan-coated magnetite nanoparticles: A comparative approach

• Two new cationic Schiff bases of chitosan coated magnetite nanoparticles were synthesized and characterized. • The morphology and structure characteristics of the synthesized nanoparticles were investigated. • Drug delivery of ciprofloxacin was investigated under physiological conditions. In this work, we report the synthesis and characterization of two cationic Schiff base-modified chitosan-coated magnetite nanoparticles, featuring either triphenylphosphonium (PPh₃⁺) or triethylammonium (NEt₃⁺) functional groups. The structural, morphological, and compositional properties of the nanocomposites were comprehensively characterized using Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), and Fourier-Transform Infrared Spectroscopy (FT-IR). TEM and SEM analyses revealed uniformly spherical nanoparticles with an average diameter of approximately 36 ± 3 nm, while XRD confirmed the crystalline nature of the Fe₃O₄ core and FT-IR verified successful Schiff base formation. To evaluate their potential for drug delivery applications, ciprofloxacin was loaded into the nanoparticles with a high encapsulation efficiency of 98 % at pH 4.8. In-vitro drug release experiments were performed to evaluate the influence of pH and temperature. The pH-dependent release was assessed at pH = 2, 5, and 7.4 under a constant temperature of 37 °C, while temperature-dependent studies were conducted at 25 °C, 37 °C, and 42 °C. The PPh₃⁺-modified system exhibited a significantly higher cumulative release (64 %) compared to the NEt₃⁺-modified counterpart (29 %) over 120 h. Release kinetics followed a zero-order model, indicating a diffusion-controlled mechanism. These findings suggest that the PPh₃⁺-based nanocarrier is a promising candidate for pH-responsive drug delivery systems, particularly under acidic conditions.