Design and characterization of a tuberculostatic hybrid based on interaction of ethambutol with a raw palygorskite

Treatment of tuberculosis (TB) based on ethambutol (ETB) in combination with other tuberculostatic agents has technological challenges due to physical instability and drug incompatibilities. Alternative formulations using clay minerals have been successfully designed. In this study, a hybrid (ETB/Pal) based on ETB and a Brazilian palygorskite (Pal) was prepared and characterized by adsorption study and diverse solid-state techniques. In addition, hygroscopicity study and in vitro release assays of ETB from the nanohybrid were performed and supported by molecular modelling study. The adsorption of ETB on Pal occurred as a spontaneous process, with around 15.9% (w/w) retained in the hybrid. Characterization of the ETB/Pal showed a change in the surface charge of Pal attributed to an electrostatic interaction between ionized amine groups from ETB and the electronegative surface of the silicate. Furthermore, molecular modelling confirmed the obtention of a nanohybrid formed mainly by hydrogen bonds between surface O atoms of Pal and hydrophilic groups of ETB. Microanalysis showed the presence and homogeneous distribution of the drug on the nanohybrid. Elucidation of the interactions between ETB and this raw clay reinforces its viability as a novel carrier to reduce the humidity adsorption by the anti-TB drugs mixture, increasing the physical stability of the formulation. •The adsorption of ETB on Pal has been successful and energetically spontaneous.•The species interacted mainly by hydrogen bonds between SiOH, and NH2 and OH.•ETB/Pal is able to improve the physical stability of TB treatment by reducing the hygroscopicity of anti-TB drugs mixture.