Effect of Surface Printing on the Release Kinetics of Gentamicin from Gradient Samples for Bone Applications

The aim of this study was to investigate the release kinetics of gentamicin from a gradient-structured sample intended for bone applications and to assess the influence of surface printing on the antibiotic release profile. The base sample was designed with a spatial gradient of porosity, enabling controlled fluid penetration and gradual release of the active substance. Such a gradient structure was expected to combine an initial therapeutic concentration with a sustained delivery phase. In addition to the base design, selected samples were modified through surface printing with a gentamicin-containing layer. This approach aimed to further prolong drug release by introducing an additional diffusion barrier and altering surface properties. The release studies were carried out under static conditions in phosphate-buffered saline (PBS) at 37 °C to simulate physiological temperature. Gentamicin concentration in the release medium was quantified at predetermined time intervals using a validated spectrophotometric method. The obtained results demonstrated clear differences in release profiles between the unmodified gradient sample and the surface-printed variant. In the surface-printed samples, the initial concentration of the drug in the medium was reduced compared to the base gradient structure, while the subsequent release phase was more uniform and extended over time. These findings indicate that surface printing represents an effective strategy for tailoring drug release kinetics from gradient materials, with potential applications in local bone infection treatment and implant-associated antimicrobial protection.