Lavrova D.G., Kamanina O.A., Arlyapov B.A.

Tula state University, Russia

Effect of structure-controlling agent on 3D-architectureof biohybridmaterialsbased on encapsulated microorganisms in conditions of sol-gel synthesis

Living organisms have developed a variety of mineralized systemsduring the evolution of natural systems. Its most important function is to protect the microorganisms and their genetic material from adverse conditions. Diatoms and Radiolaria are unicellular organisms that have evolved so that they became able to form silicate capsule on its surface, forming exoskeleton to provide mechanical protection. These organisms have inspired researchers to create hybrid biomaterials (biohybrids), the so-called "artificial spores" based on living cells, encapsulated in organic and inorganic membranes.Cells covered with a protective shell can be usedas promising biocatalysts.Biosensors, biofilters, bioreactors, implants, biologics for the degradation of toxic compounds, and others can be createon itsbase. Polymeric structure based on silicon compoundsareof particular interest, as they have several advantages over organic hydrogels: maintaining the physiological activity of living cellsfor a long time, providing of effective protection against thermal, mechanical, biological effects.

Methods of sol-gel chemistry are used for obtaining of structured silicate biohybrid materials, due to the flexibility of the chemical composition of the materials and no need for energy-intensive, expensive equipmentin the preparation process. The most effective way of providing directional control of textural characteristics of silica materials is the sol-gel method using control structure agents.There are some papers devoted to the synthesis of mesoporous silica materials using polyethylene glycol as the structure-controlling agent.They show that the addition of PEG during synthesis results in increased average particle size and the pore diameter of the final gel, and provides the possibility of controlling the particle size and pore structure of the silica materials by modifying it with PEG of different molecular weight [1-3]. Today there is no single common scheme of formation of silica material in the presence of water-soluble nonionic linear polymer as PEG. All studies were aimed at obtaining silica materials without the participation of living organisms. Thus, the study of the effect of PEG on the formation of the biohybrid porous structure in the sol-gel synthesis is important.

Fig. 1. SEM image of encapsulated Ogataea polymorpha BKM Y-2559:

A – PEG-1000, B – PEG-2000, С – PEG-3000, D– PEG-6000

In this work tetraethoxysilane and methyltriethoxysilane were used as the silane precursors, yeast cells Ogataeapolymorpha BKM Y-2559 were used as the biomaterial, the structure-controlling agent was PEG. Study of biohybrids structure obtained using sol-gel technology was performed by scanning electron microscopy. 3D-biohybrid architecture varied depending on the molecular weight of the structure-controllingagent (Figure 1):in the presence of PEG with a molecular weight of 1000 and 2000 Da, the formation of the monolithic organic matrixdominates, but using PEG 2000 and 3000 Da leads toappearance of distinct fractal structures with a particle size of 0.7 to 2 microns.Of greatest interest is the architecture ofhybrid biomaterial obtained with using PEG of molecular weight 3000 Da as structure-controlling agent. Capsules are formed around each cell, wherein the encapsulated cells form a single structure. Further increase in the molecular weight of PEG up to 6000 Da results in the formation of a dense structure around the yeast cell matrix Ogataeapolymorpha BKM Y-2559.

The reported study was funded by the Russian President's grant for state support of young Russian scientists - PhD contract № 14.Z56.16.5425-MC and grant RFBR according to the research project № 16-48-710959 r_a.

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