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This paper presents a study of nanostructural features of contacts of bioprinted tissue spheroids with polyurethane dual scale biocompatible scaffold made by three-dimensional printing and electrospinning. Analysis of nanostructural features of cell contacts was carryed out by scanning probe microscopy with use of experimental setup combining ultramicrotome and scanning probe microscope. Measured mean cell volume is 460 ± 104 μm3, mean contact area of cells with scaffold fibers–104.8 μm2 per cell (16.7% of total cell area). Maximum distance of migrating cells from spheroid border at 48 h. is ~200 μm, what corresponds to mean velocity of cell migration more than 4 μm/h. Obtained quantitative characteristics of micro- and nanostructure of human fibroblast cell contacts with elecrospun polyurethane scaffold secure high efficacy of tissue regeneration with its usage for implanted bioprinted dual scale tissue-engineered scaffolds.

The molecular mechanisms of DNA recognition and modification by EcoRII DNA methyltransferase (M.EcoRII) were studied using 14-mer substrate analogs containing 2-aminopurine or 1′,2′-dideoxy-D-ribofuranose in the M.EcoRII recognition site. The efficiency of DNA binding and methylation depended on the position of a modified nucleoside residue in the recognition site. A structural model of M.EcoRII in complex with substrate DNA and the cofactor analog S-adenosyl-L-homocysteine (AdoHcy) was constructed using the available crystal structures of M.Hha and M.HaeIII and the recent Frankenstein’s monster approach. The amino acid residues interacting with DNA were predicted based on the model. In addition, theoretical and experimental findings made it possible to predict the groups of atoms of the heterocyclic bases of the M.EcoRII recognition site that are presumably involved in the interactions with the enzyme.