Construction of composites for medical purpose based on pyrogenic silica with immobilized succinic acid and their properties

The work is aimed at creating new, more effective drugs containing succinic acid. For this purpose, a methodology has been developed for transferring the active substance to a nano-sized state, in which the acid, due to an increase in its outer surface, is in the form of clusters, which, upon contact with the mucous membrane, can be more easily absorbed by the body. A complex of physicochemical methods was used to study the effect of immobilization of Succinic Acid (SA) on the surface of hydrophilic, hydrophobic silica and their mixtures on the existing specific surface area and the state of the adsorption layer. It has been shown that during the joint mechanical grinding of crystalline succinic acid with silicas, composite systems are formed in which it is uniformly distributed in the interparticle gaps of silicas and is in the form of nanosized predominantly amorphous clusters. For silicas and their mixtures, the signal of acid crystallites is also fixed on the X-ray diffraction patterns. Additional mechanical treatment of composites with water practically does not change the ratio of amorphous and crystalline components of succinic acid in the surface layer, which indicates its poor solubility in clustered water. This is also confirmed by liquid NMR data, according to which there is no signal from the methylene groups of succinic acid in the spectra. All composites, regardless of the content of SA, treatment with water, and the ratio of the hydrophobic and hydrophilic components, retain a high adsorption capacity with respect to nitrogen. The BET-specific surface of the composites remains at the level of 150 - 200 m2/g. Hydrated forms of hydrophobic silica AM-1 retain the ability to interact with non-polar substances. Using chloroform as an example, it was shown that even at h = 1 g/g, chloroform displaces part of the water from the interparticle space, which manifests itself in a decrease in the interfacial energy of water due to the formation of surface water clusters with a large radius. The hydrophobic silica surface stabilizes the weakly associated form of water, the amount of which can reach 20 mg/g.