Magnetic activated carbon particles as stimuli-responsive vehicles for methotrexate†

This study investigates porous activated carbon (AC) particles as drug delivery vehicles for methotrexate (MTX). To enhance functionality, magnetic nanoparticles are embedded in AC imparting superparamagnetic properties (MAC composites), making them suitable for controlled transport and localization, as well as for facilitating their response to external fields. The composites are further functionalized with branched low molecular weight polyethyleneimine (PEI) to confer them a positive charge. After characterizing size, composition, and magnetic hysteresis, their potential as MTX carriers is assessed. Electrophoretic mobility and infrared data confirm the presence of magnetite, polymer, and drug molecules. Photothermal therapy (PTT) tests reveal that MAC–PEI particles produce up to 180 W g⁻¹ of specific absorption rate (SAR) under infrared laser radiation. Due to its anisotropy, rotating magnetic fields (RMF) induce particle rotation, offering another external stimulus. Biocompatibility studies with human skin M1 fibroblasts confirm no significant cytotoxicity at concentrations below 700 μg mL⁻¹. The particles adsorb over 80% of MTX from 0.6 mM solutions, with release evaluated at pH 5.8 under PTT and RMF stimuli. Both methods significantly enhance MTX release, achieving twice the drug release compared to passive conditions, demonstrating the particles’ high potential as active vehicles for targeted MTX delivery.