Formulation, characterisation and in vitro studies of doxorubicin-loaded silica–polydimethylsiloxane granules

The goal was to develop a granule-type formulation, characterised as a long-term, zero-order release delivery system for doxorubicin hydrochloride (DOX) and composed of a sol–gel derived silica–polydimethylsiloxane solid matrix with well-defined microstructures. The preparation of the DOX-loaded granule-type formulation was performed using the sol–gel moulding method. A liquid-form of DOX was added to the sol before moulding. Optical microscopy, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption/desorption studies were employed to characterise the obtained formulation. The influence of different drug loads of DOX per granule (136, 336 and 555 μg) on the release profiles was assessed on a USP Apparatus 4 dissolution and via UV/Vis end analysis. The in vitro mineralisation of these formulations associated with the nucleation of the apatite layer on their surface was also examined. The semi-ellipse shape and micrometer-size of the DOX-loaded granule-type formulation was successfully obtained. These formulations exhibited a mesoporous structure, uniform pore size distribution and good monodispersity. Following an initial burst, the slow drug release from all formulations followed zero order kinetics under infinite sink conditions for over 70 days. Besides the formulation’s potential properties as a carrier, the material was also surface-reactive during in vitro mineralisation.

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