Abstract: The invention concerns a system for biocompatible drug release comprising: (i) a polymer matrix; (ii) an inorganic component located inside said matrix and characterized by a lamellar structure with a net positive or negative charge able to intercalate (iii) a pharmacologically active principle into said lamellar structure, by establishing an ionic type of bond with it and thereby obtaining an intercalation compound. The preparation process for the release system comprises the stages of: treating the lamellar solid in such a way as to give it a net positive or negative charge, then combining it with the chosen active principle, also in an ionic form, to obtain an intercalation compound which is then mixed with the polymer matrix. The release system can be employed in making medical devices, like sutures, membranes, osteosynthesis plaques, multilayered devices, gels and drug delivery systems.

Abstract: The invention concerns a system for biocompatible drug release comprising: (i) a polymer matrix; (ii) an inorganic component located inside said matrix and characterized by a lamellar structure with a net positive or negative charge able to intercalate (iii) a pharmacologically active principle into said lamellar structure, by establishing an ionic type of bond with it and thereby obtaining an intercalation compound. The preparation process for the release system comprises the stages of: treating the lamellar solid in such a way as to give it a net positive or negative charge, then combining it with the chosen active principle, also in an ionic form, to obtain an intercalation compound which is then mixed with the polymer matrix. The release system can be employed in making medical devices, like sutures, membranes, osteosynthesis plaques, multilayered devices, gels and drug delivery systems.

Abstract: A tetravalent metal diphosphonate-phosphite composition definable by the following general formula:M(O.sub.3 P--R--PO.sub.3).sub.1-x (HPO.sub.3).sub.2x (I)is described where:M is a tetravalent metal;x varies from 0.5 to 0.66;R is an organic radical of bivalent aromatic type, carrying side groups which increase its steric hindrance.The composition is in the form of a crystalline solid with a type .alpha. layered structure with the diphosphonic groups positioned to join said layers together by a covalent bond (pillared compounds). It has a B.E.T. surface area from 300 to 500 m.sup.2 /g depending on the nature of R in formula (I), and a porosity in the micropore radius range of less than 20 .ANG. (Angstrom), such micropores contributing to the extent of more than 95% of the total area for the most crystalline materials.

Abstract: The present invention discloses a compound comprising a diphosphonate/phosphite of a tetravalent metal:M[(O.sub.3 P--R--PO.sub.3).sub.1-(x+y) (HPO.sub.3).sub.2X (O.sub.3 P--R--PO.sub.3 H.sub.2).sub.2y ](where M, R, x and y have the meaning given in the description), in the form of a crystalline solid with an alpha-type lamellar structure with a distance between layers of 7.4 to 20.ANG. (depending on the dimensions of radical R), a BET surface area of 250 to 400m.sup.2 /g, and porosity within the mesopore range, with at least 50% of the pores measuring 20 to 30.ANG.. The compound, depending on the radical R used, may or may not have microporosity in the region between layers. Such a diphosphonate/phosphite of a tetravalent metal is obtained by reaction between diphosphonic acid, phosphorous acid and an oxyhalide of a tetravalent metal, in a solvent comprising dimethyl-sulphoxide/water containing hydrofluoric acid.

Abstract: Ion exchange inorganic films made up of alpha-type or gamma-type layered structure insoluble acid salts of tetravalent metals or their salt forms, or their intercalated forms or their organic derivatives containing polar groups. A process for the preparation of said films.

Abstract: Mixed phosphorous or arsenic salts of tetravalent metals are provided having the general formula M(HAO.sub.4).sub.2-x (HAO.sub.3).sub.x.nH.sub.2 O, where M is Zr, Ti or Hf, A is phosphorus or arsenic, x is between 0.05 and 1.95, and n is 0 to 6. The salts are highly stable and have wide potential application in the fields of ion exchange, catalysis, intercalation of molecules, solid electrolytes, and chromatography. The salts are prepared by reacting a halide, oxyhalide, nitrate, sulphate, phosphate or oxide of the tetravalent metal, preferably in an aqueous medium, with at least two oxygenated acids of phosphorus and/or arsenic.

Abstract: Inorganic layers, papers and membranes for ion exchange are made of fibrous thorium acid phosphate with a ratio PO.sub.4 /Th in the solid of about 2.