The designing of new biodegradable polymer composites is one of the most promising areas of modern orthopedics and regenerative surgery. At present, a number of methods have been proposed for designing and processing biodegradable polymer composites via various 3D printing technologies; however, the homogeneity of filler distribution together with mechanical properties of scaffolds made of such composites are far from those required for clinical use. In this study, the method for producing biodegradable composite material based on poly(l‐lactic acid) (PLLA) solution in organic solvent and hydroxyapatite (HAp) powder was proposed. The influence of HAp weight fraction and additional annealing on PLLA matrix crystallinity was investigated. It was shown that crystallinity of PLLA decreases from 58.84 ± 1.21 to 17.33 ± 1.69 as HAp weight fraction increased from 0 to 50 wt%. However, HAp filler promoted PLLA crystallites growth according to the X‐ray powder diffraction analysis. The results of nanoindentation showed Young's modulus values of the 3D‐printed scaffolds with 50 wt% of HAp at the level of human femur and tibia.

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The influence of the types and amounts of oxygen (O), nitrogen (N), and/or phosphorus (P) heteroatoms on the surface of carbon nanotubes (CNTs) on stability and catalytic activity in the oxygen reduction reaction (ORR) was investigated in alkaline media. It is shown that functionalization of CNTs leads to growth of the electrochemically active surface and to an increase in activity in the ORR. At the same time, a decrease in stability is observed after functionalization of CNTs under accelerated corrosion testing in alkaline media. These results are most significant on CNTs after functionalization in HNO3, due to the formation of a large number of structural defects. However, subsequent doping with N and/or P atoms provides a further activity increase and enhances the corrosion stability of CNTs. Thus, as shown by the studies of characteristic parameters (electrochemical active surface values (SEAS); E1/2; corrosion stability), CNTs doped with N and NP are promising catalytic systems that can be recommended for use as fuel cell cathodes. An important condition for effective doping is the synthesis of carboxyl and carbonyl oxygen-containing groups on the surface of CNTs.

A simple, rapid high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of glycolic acid, lactic acid, glicolide, lactide and ethyacetate in monomers for obtaining biopolymers. The separation was effected on the reversed-phase C18 column 250mm•4.6 mm with particle size 5 [mu] using a mobile phase mixture buffer and acetonitrile in a ratio 88:12 v/v and elution was isocratic at a flow-rate of 1.0 mL/min. The determinations were performed with a UV-Vis detector at 200 nm. The volume of the injected sample was 20 [mu]L. Detection limits for acids and its dimers (glycolic acid, lactic acid, glicolide, lactide) and ethylacetate range between 82 and 182 ng/mL. The analytes are separated in 13 min. Recovery studies showed good results for all solutes (99–102%). The method is linear for all compounds over the concentration range tested, and shows good precision and accuracy, making it suitable for quantitation of acids and its dimers (glycolic acid, lactic acid, glicolide, lactide) and ethyl acetate in monomers