Ciprofloxacin-loaded poly(lactic acid) coating on polyurethane ureteral stents: surface structure, antibacterial...

Surface modification of polyurethane (PU) ureteral stents offers a practical route to limit bacterial colonisation and encrustation. Here, ciprofloxacin (CIP)-loaded poly(lactic acid) (PLA) coatings were deposited on PU ureteral stents by dip coating. Coating morphology, adhesion, antibacterial activity, encrustation resistance and biocompatibility were evaluated. The optimised conditions-5% PLA, 2.5% CIP and a withdrawal speed of 4 mm s^-1-produced a continuous coating approximately 20 µm thick. FTIR spectra showed a CIP-associated absorption near 1620 cm^-1 that increased with nominal CIP content. UV-visible measurements showed daily CIP release in artificial urine and PBS for 14 d, with higher release in acidic artificial urine. After 1 h exposure, CIP-coated stents produced lower viable colony counts than uncoated PU and commercial Ag-coated stents, particularly for Escherichia coli. The 2.5% CIP/PLA coating also reduced crystal deposition during 40 d static artificial-urine immersion and in a calcium oxalate mouse implantation model. HK-2 assays and bladder histology from a separate 20 d normal-mouse implantation cohort indicated good local tissue compatibility. These results link coating formulation and structure with medium-dependent CIP release, antibacterial activity and encrustation resistance, supporting further preclinical evaluation of the coated stent.