Acid-etched Halloysite nanotubes as superior carriers for ciprofloxacin

Clay minerals have opened new avenues in drug delivery, including antimicrobials, greatly enhancing the stability and efficacy of the active payloads. Among these clay mineral hosts, Halloysite nanotubes (HNT) have emerged as a prominent carrier owing to their intrinsic mesoporous tubular nanostructure and high adsorption capacity. The acidic etching of HNT increases their specific surface area and porosity, consequently enhancing their loading potential. In this work, we show for the first time, that etched HNT (E-HNT) are superior carriers of the potent antibiotic ciprofloxacin (CIP) compared to pristine HNT in terms of loading capacity and antibacterial effect. The loading conditions are optimized within near-physiological conditions to enable future combinations with biomolecules; where CIP loading and release are characterized by UV-Vis measurements and thermogravimetry. Solid-state characterization suggests an adsorptive loading mechanism, involving electrostatic attraction and possible tautomerism. Release experiments show that the loaded CIP exhibits a sustained release profile and maintains its antibacterial potency as confirmed by the broth microdilution (BMD) and zone of inhibition methods. Thus, the facile etching of HNT enhances the nanoclay properties rendering it suitable for future application in drug delivery formulations.

Automated summary

Clay minerals, especially Halloysite nanotubes (HNT), have shown great potential in drug delivery due to their mesoporous tubular nanostructure and high adsorption capacity. Acid etching of HNT increases their loading potential by increasing specific surface area and porosity. This study demonstrates that etched HNT (E-HNT) outperforms pristine HNT in terms of loading capacity and antibacterial effect when used as a carrier for the antibiotic ciprofloxacin (CIP).