Magnetically triggered release of amoxicillin from xanthan/Fe₃O₄/albumin patches

This work was motivated by the need of stimuli responsive drug carriers, which can be activated by low cost non-invasive stimuli such as external magnetic field (EMF). Thus, novel antimicrobial materials based on xanthan gum (XG), magnetic nanoparticles (MNP), bovine serum albumin (BSA) and amoxicillin (Amox) were designed in order to promote the release of Amox under magnetic stimuli. Firstly, surfaces with different functionalities were prepared by sequential deposition of thin layers on Si wafers and characterized by means of ellipsometry and atomic force microscopy. Amox adsorbed preferentially onto XG or BSA films. In solution, favorable interactions between Amox and BSA were evidenced by substantial changes in the BSA secondary structure, as revealed by circular dichroism. Patches of XG and XG/MNP/BSA were immersed in 2 g L^-1 Amox, yielding 10 ± 3 and 17 ± 4 μg/cm³ Amox loading, respectively. The inclusion of 0.2 wt% Fe₃O₄ in the patches and their exposure to EMF enabled in vitro release of Amox, at pH 5.5 and 0.02 mol L^-1 NaCl, following the quasi-Fickian behavior. Amox diffused from XG/MNP/BSA patches in agar medium containing Staphylococcus aureus and Escherichia coli, inhibiting their growth. The inhibition of E. coli growth was particularly efficient under EMF.