Polymer-amino-functionalized silica composites for the sustained-release multiparticulate system

Highlights: • Oral multiparticulate formulation composed of polymer and hybrid silica is tested. • The hybrid silica gel fabricated by the gelation of its precursor in ammonia vapors. • The amine-functionalized silica gel prolongs release of the drug. • The hybrid silica gel plays the role of enteric coating in formulation • Novel strategy for the intestinal diclofenac sodium sustained-release system. - Abstract: This study presents an interesting and promising strategy for producing an oral multiparticulate formulation of the sustained-release of diclofenac sodium (DS) consisting of subunits closed inside hard gelatin capsules (each capsule contains ~ 50 mg of diclofenac sodium). The subunits in the form of beads were produced through the encapsulation of diclofenac sodium dispersed within a nondisintegrating polymer carrier by a silica gel functionalized with the 3-aminopropyl groups. The hybrid silica gel, which plays the role of enteric coating, was fabricated by the gelation of the liquid silica precursors mixture (i.e. tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES)) in the vapor phase of ammonia. The conducted studies reveal that the introduction of the hybrid silica gel into the solid DS dispersion facilitates prolonged release in the neutral environment of the intestine. Since the ability of the multiparticulate formulation to control the release of the drug depends on the properties of its subunits, studies involving the low temperature N₂ sorption, DSC analysis together with spectroscopic techniques (XRD, SEM, ²⁹Si MAS NMR) were conducted.