Synthetic Geopolymers for Controlled Delivery of Oxycodone: Adjustable and Nanostructured Porosity Enables Tunable and Sustained Drug Release

In this article we for the first time present a fully synthetic mesoporous geopolymer drug carrier for controlled release of opioids. Nanoparticulate precursor powders with different Al/Si-ratios were synthesized by a sol-gel route and used in the preparation of different geopolymers, which could be structurally tailored by adjusting the Al/Si-ratio and the curing temperatures. In particular, it was shown that the pore sizes of the geopolymers decreased with increasing Al/Si ratio and that completely mesoporous geopolymers could be produced from precursor particles with the Al/Si ratio 2∶1. The mesoporosity was shown to be associated with a sustained and linear in vitro release profile of the opioid oxycodone. A clinically relevant release period of about 12 h was obtained by adjusting the size of the pellets. The easily fabricated and tunable geopolymers presented in this study constitute a novel approach in the development of controlled release formulations, not only for opioids, but whenever the clinical indication is best treated with a constant supply of drugs and when the mechanical stability of the delivery vehicle is crucial

Controlled Architecture of Solids With Micro-porosity and Meso-porosity Obtained By Pillaring of Montmorillonite With An Laniox Binary Oxide

High-surface-area solids containing both micropores and mesopores have been synthesized by intercalation of the heterobinuclear cation of the complex NiLa(fsaen)NO3 between the layers of montmorillonite clay and calcination at 500-degrees-C. The adsorption mechanism of the complex follows an exchange reaction involving up to 2 mmol of complex cations per g of clay. Further amounts of complex are adsorbed in sites other than exchange ones as shown by zeta-potential experiments. The IR spectra of the intercalated complex showed no major alterations of the complex during adsorption and a stabilization effect and enhancement of the parallel orientation of the clay plates. X-Ray diffraction (XRD) measurements at low angles showed that the pillared clay possesses an interlayer distance of 13.4 angstrom at 500-degrees-C. Its BET surface area reaches a maximum of 220 m2 g-1 at this temperature. The a(s) plots showed a maximum microporosity at less-than-or-equal-to 2 mmol g-1 Additional loading results in transformation to a mesoporous delaminated structure. X-Ray photoelectron spectra (XPS) of the composite materials showed that the ratios La/Si and Ni/Si are lower than those determined by chemical analysis, owing to the shielded environment of the LaNiO(x) pillars in the clay. The same method indicated that for a high degree of loading the aggregates seem to be of perovskite origin