Liana R. Azizova

We employ photo-induced force microscopy, an atomic force microscopy based technique that directly measures forces arising from light-induced polarization in the near-field region, for nanoscale chemical mapping of complex biological systems.

Fatty acids (FA) are the main constituents of lipids and oil crop waste, considered to be a promising 2G biomass that can be converted into ketenes via catalytic pyrolysis. Ketenes are appraised as promising synthons for the pharmaceutical, polymer, and chemical industries. Progress in the thermal conversion of short- and long-chain fatty acids into ketenes requires a deep understanding of their interaction mechanisms with the nanoscale oxide catalysts. In this work, the interactions of fatty acids with silica are investigated using a wide range of experimental and computational techniques (TPD MS, DFT, FTIR, in situ IR, equilibrium adsorption, and thermogravimetry). The adsorption isotherms of linear and branched fatty acids C1-C6 on the silica surface from aqueous solution have been obtained. The relative quantities of different types of surface complexes, as well as kinetic parameters of their decomposition, were calculated. The formation of surface complexes with a coordination bond between the carbonyl oxygens and silicon atoms in the surface-active center, which becomes pentacoordinate, was confirmed by DFT calculations, in good agreement with the IR feature at ∼1680 cm ¹. Interestingly, ketenes release relate to these complexes' decomposition as confirmed by the thermal evolution of the absorption band (1680 cm^-1) synchronously with the TPD peak of the ketene molecular ion. The established regularities of the ketenezation are also observed for the silica-induced pyrolysis of glyceryl trimyristate and real waste, rapeseed meals.

Nitric oxide NO, mediates inflammatory and thrombotic processes and designing biomaterials capable of releasing NO in contact with biological tissues is considered to be a major factor aimed at improving their bio- and haemocompatibility and antibacterial properties. Their NO-releasing capacity however is limited by the amount of the NO-containing substance incorporated in the bulk or immobilised on the surface of a biomaterial. An alternative approach is based on the design of a material generating nitric oxide from endogenous NO bearing metabolites by their catalytic decomposition. It offers, at least in theory, an unlimited source of NO for as long as the material remains in contact with blood and the catalyst maintains its activity. In this paper we studied the catalytic properties of novel nanostructured CuO/SiO₂ catalysts in generating NO by decomposition of S-nitrosoglutathione (GSNO) in vitro. CuO/SiO₂ catalysts with different CuO loadings were synthesized by chemisorption of copper(II) acetylacetonate on fumed nanosilica followed by calcination. CuO content was controlled by a number of chemisorption–calcination cycles. Fourier-transform infrared spectroscopy and thermogravimetric analysis confirmed the formation of CuO/SiO₂ nanoparticles (NPs) with particle size of CuO phase in the range from 71 to 88 nm. Scanning electron microscopy images revealed a uniform distribution of NPs without their sintering or agglomeration. All the materials of the CuO/SiO₂ NP series exhibited NO-generating activity from GSNO confirmed by the Griess assay and by measuring the concentration of nitrite and nitrate anions in model solutions such as phosphate buffered saline and bovine serum. This activity is dependent on the material specific surface area and CuO exposure on the surface rather than CuO bulk content. The rate of NO production increased at higher initial concentration of the NO-bearing substrate studied in the range between 0.01 mM and 1.0 mM RSNO, which covers its physiological level. CuO/SiO₂ NPs can be used to design polymers with NO generating properties at blood-biomaterial interface which are expected to have improved biocompatibility thus enhancing their potential for medical applications such as surgical tubing, peripheral venous catheters, auxiliary blood circulation devices and drug-eluting balloons.

Nitric oxide (NO) generating surfaces are potentially promising for improving haemocompatibility of blood-contacting biomaterials. In the present report, Cu-modified poly(vinyl chloride) (PVC) and polyurethane (PU) were prepared via polydopamine (pDA)-assisted chelation. The copper content on the PVC and PU modified surfaces, assessed by inductively coupled plasma - optical emission spectrometry (ICP-OES), were about 3.86 and 6.04 nmol·cm⁻², respectively. The Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) data suggest that copper is attached to the polymer surface through complex formation with pDA. The cumulative leaching of copper from modified PVC and PU during the five day incubation in phosphate buffered saline (PBS), measured by inductively coupled plasma mass spectrometry (ICP-MS), was about 50.7 ppb and 48 ppb, respectively which is within its physiological level. Modified polymers were tested for their ability to catalytically generate NO by decomposing of endogenous S-nitrosothiol (GSNO). The obtained data show that Cu-modified PVC and PU exhibited the capacity to generate physiological levels of NO which could be a foundation for developing new biocompatible materials with NO-based therapeutics.

In this study, chemical transformations of benzyl ester of О-(phenyl-2-acetamido-2,3-dideoxy-1-thio-β-d-glucopyranoside-3-yl)-d-lactoyl-l-alanyl-d-isoglutamine (SPhMDPOBn) on the fumed silica surface were examined, and the surface complex structure was characterized by temperature-programmed desorption mass spectrometry (TPD-MS), infrared spectroscopy (FTIR) and electrospray ion trap mass spectrometry (ES IT MS). Stages of pyrolysis of SPhMDPOBn in pristine state and on the silica surface have been determined. Probably, hydrogen-bonded complex forms between silanol surface groups and the C = O group of the acetamide moiety NH-(CH3)-C = O…H-O-Si≡. The thermal transformations of such hydrogen-bonded complex result in pyrolysis of SPhMDPOBn immobilized on the silica surface under TPD-MS conditions. The shifts ∆ν of amide I band (measured from 1,626 to 1,639 cm−l for SPhMDPOBn in pristine state) of 33 and 35 cm−l which occurred when SPhMDPOBn was immobilized on the silica surface may be caused by a weakening of the intramolecular hydrogen bonding of the SPhMDPOBn because the interaction with the silica surface as hydrogen bond with silanol groups is weaker than that in associates.