Preparation Of Zirconium Diphosphonate-Phosphites With A Narrow Distribution Of Mesopores

The presence of H3PO3 in the synthesis of zirconium diphosphonates in dimethylsulfoxide, other than the expected dilution of the pillars, which in turn gives rise to a certain degree of microporosity, may also induce the formation of a high percentag. of mesopores. E.g., compounds with high surface area(300–500 m2 /g) of which 60–70% is due to mesopores with diameters 20–40 Å and the remaining is due to micropores, were obtained. It was furthermore found that the distribution of the mesopores was fairly narrow. Compounds with micropores <3 Å and mesopores of 20–30 Å behave in practice as pure and narrow mesoporous solids;they are therefore of great interest as new molecular inorgano-organic sieves.

Zirconium Organic Diphosphate-Diphosphonates With Tilted Rigid Pillars

The H2O3PCH(C6H4)2CH2PO3H2 and H2O3PO(C6H4)2OPO3H2 acids were synthesizedT and used to obtain new pillared zirconium phosphonates and organic phosphates in which the pillars are tilted with respect to the layers. The Zr(O3PCH2(C6H4)2CH2PO3) and Zr(O3PO(C6H4)2OPO3) obtained have a good thermal resistance and the distance between the inorganic α-layers joined by the organic pillars is 14.7 and 13.8 Å, respectively. Structural models suggest that the biphenyl groups in the solids are tilted at 140° and 137° with respect to the perpendicular at the layer plane. Solid solutions of the two derivatives over the whole range of composition have also been obtained; the distance between the α-layers changes from 14.7 to 13.8 Å in a continuous way as the diphosphate groups replace the diphosphonate ones, allowing us to suppose a variation of the tilting angles. Attempts to remove the phosphoester in the mixed derivatives by hydrolytic attack, and to replace some pillars with phosphite groups are described.

Nanohybrids for controlled antibiotic release in topical applications

New polymeric composite materials containing a nanohybrid to be used for the controlled release of an antibiotic molecule, chloramphenicol succinate, have been formulated, prepared and characterised. The nanohybrid consists of a layered double hydroxide of Mg-Al hydrotalcite-type, in which the nitrate anions present in the host galleries were replaced with chloramphenicol succinate anions (CFS(-)) by a simple ion-exchange reaction. Different amounts of the hybrid material were incorporated in polycaprolactone and processed as films of 0.15mm thickness. The composite materials were analysed by X-ray diffractometry and thermogravimetry and their mechanical properties were determined. They showed properties even better than those of the pristine polymer. The release process of the antibiotic molecules was found to be very interesting and promising for tuneable drug delivery. It consists of two stages: an initial stage of a very rapid burst, in which a small fraction of drug is released; and a second stage that is much slower, extending for a longer and longer time. This behaviour is profoundly different and much slower than that of a sample in which the antibiotic molecule is directly incorporated into the polymeric matrix. The parameters influencing drug release have been individuated and discussed.

Anti-inflammatory drug incorporation into polymeric nano-hybrids for local controlled release

In this paper we present the formulation, preparation and characterization of new polymeric composite materials containing a nano-hybrid to be used for the controlled molecular delivery of an anti-inflammatory molecule, Diclofenac. The nano-hybrid consists of a layer of double hydroxide of an Mg-Al hydrotalcite type, in which we replaced the chloride anions present in the host galleries with Diclofenac anions by a simple ion-exchange reaction. Different amounts of the hybrid material were incorporated in polycaprolactone and processed as films of 0.15 mm thickness. The composite materials were analyzed by X-ray diffractometry, thermogravimetry and for their mechanical properties, and showed properties even better than those for the pristine polymer. The release process of the anti-inflammatory molecules was very interesting and promising for tuneable drug delivery. It consists of two stages: a first stage, very rapid as a burst in which a small fraction of the drug is released, and of a second stage that is much slower, extending for longer and longer periods. The parameters influencing the drug release were individuated and discussed.