The purpose of the work is to create a scientific basis for the use of hydrophobic silica in medical composites based on nanosilica and hydrophilic biomaterials, such as succinic acid, natural amber, dispersed Amanita mussaria mushrooms, and alginic acid.
The relevance of the work is due to the fact that currently the possibility of creating bionanocomposite systems, which use hydrophobic silicas, has hardly been studied. The issue of combining hydrophobic and hydrophilic materials in one system is of both general scientific and practical interest, since the interaction of hydrophobic and hydrophilic particles in a dry state occurs due to van der Waals bonds. When these composite )hydrophobic-hydrophilic) particles are transferred into an aqueous medium, their hydration processes take place, which from a thermodynamic point of view are governed by the principle of minimizing the free energy of the water-solid body system.
Low-temperature 1HNMR spectroscopy, solid-state NMR spectroscopy, thermogravimetry, TEM and SEM microscopy and IR spectroscopy were chosen as the main methods of further investigation. The wetting-drying method followed by mechanic and chemical activation was used to freeze the samples. This method was effective for both hydrophilic and hydrophobic materials, while air was removed from the interparticle space of hydrophobic materials by dosed mechanical loads in the presence of water.
It is assumed that the composite system AM-1 (A-300)/succinic acid, AM-1/amber and AM-1 (A-300)/Amanita mussaria, which enter the liquid environment of the gastrointestinal tract due to the presence of hydrophobic silica, form an interface layer of clustered water with a partially broken network of hydrogen bonds on the surface of the mucous membrane. This, on the one hand, can affect the complete absorption of bioactive substances, and on the other, determine the speed of their release. In this way, systems of programmed delivery of active substances can be created and their bioavailability can be increased.
It is shown that on the basis of hydrophilic and hydrophobic silicas and their 1/1 mixture, composite systems with succinic acid can be obtained by the method of dosed mechanical loads, in which a significant part of it is distributed in nano-sized interparticle gaps of silicas. Depending on the method of preparation of the composite, such textural parameters as specific surface area and pore volume change.
Water adsorbed by hydrophobic silica has the maximum interfacial energy and is in a clustered state, and the cluster radius does not exceed 10 nm. Probably, the increase in the value of the interfacial energy in the process of creating the methylsilica/H2O composite under the influence of high mechanical loads is due to the transition of water from the bulk to the clustered state. With the same water content, the interfacial energy (S) of methylsilica (AM-1) was 2.5 times higher than for the AM-1/SA/H2O composite created on its basis, which is due to the formation on the surface of AM-1 with immobilized BC of larger water clusters. Thus, the energy of hydrophobic hydration of methylsilica will be higher than when immobilized on its BC surface.
The use of the mushroom Amantia muscaria as part of a nanocomposite system with amorphous, highly dispersed hydrophilic and hydrophobic silica is proposed for medical use. At the same time, it is assumed that the main toxic components, which are bound by enzymes in the fruiting body of the mushroom, will be adsorbed by the surface of silica, which has a high affinity for protein molecules, and will be excreted from body together. It is shown that the water included in the composition of the mushroom or its composite with nanosilicas can be in strongly and weakly associated states, The latter is stabilized by contact with a weakly polar environment that simulates the hydrophobic part of the phospholipid structures of the intestinal mucosa. It is assumed that this effect will increase the bioavailability of active substances desorbed from the composite system in the body.
For hydrated alginic acid, in contrast to other studied systems, the replacement of air with CDCl3 medium is not accompanied by decrease, but an increase in the interaction of water with surface. This is probably due to the formation in the interparticle gaps of a system of water clusters bound to the carboxyl surface groups of acid residues. At the same time, the penetration of chloroform molecules into the interparticle gaps is thermodynamically disadvantageous.
Key words: hydrophobic and hydrophilic silica, amber, succinic acid, Amanita mussaria, composite systems, interphase energy, strongly and weakly bound water, alginic acid.
