Effect of photoconversion conditions on the spectral and cytotoxic properties of photoconvertible fluorescent polymer markers.

Fluorescence labeling of cells is a versatile tool used to study cell behavior, which is of significant importance in biomedical sciences. Fluorescent photoconvertible markers based on polymer microcapsules have been recently considered as efficient and perspective ones for long-term tracking of individual cells. However, the dependence of photoconversion conditions on the polymeric capsule structure is still not sufficiently clear. Here, we have studied the structural and spectral properties of fluorescent photoconvertible polymeric microcapsules doped with Rhodamine B and irradiated using a pulsed laser in various regimes, and shown the dependence between the photoconversion degree and laser irradiation intensity. The effect of microcapsule composition on the photoconversion process was studied by monitoring structural changes in the initial and photoconverted microcapsules using X-ray diffraction analysis with synchrotron radiation source, and Fourier transform infrared, Raman and fluorescence spectroscopy. We demonstrated good biocompatibility of free-administered initial and photoconverted microcapsules through long-term monitoring of the RAW 264.7 monocyte/macrophage cells with unchanged viability. These data open new perspectives for using the developed markers as safe and precise cell labels with switchable fluorescent properties.

Degradation of Hybrid Drug Delivery Carriers with a Mineral Core and a Protein-Tannin Shell under Proteolytic Hydrolases.

Hybrid carriers with the mineral CaCO3/Fe3O4 core and the protein-tannin shell are attractive for drug delivery applications due to reliable coupling of anticancer drugs with protein-tannin complex and the possibility of remote control over drug localization and delivery by the external magnetic field. This study aims to elucidate the mechanisms of drug release via enzymatic degradation of a protein-tannin carrier shell triggered by proteolytic hydrolases trypsin and pepsin under physiological conditions. To do this, the carriers were incubated with the enzyme solutions in special buffers to maintain the enzyme activity. The time-lapse spectrophotometric and electron microscopy measurements were carried out to evaluate the degradation of the carriers. It was established that the protein-tannin complex demonstrates the different degradation behavior depending on the enzyme type and buffer medium. The incubation in trypsin solution mostly resulted in the protein shell degradation. The incubation in pepsin solution did not affect the protein component; however, the citric buffer stimulates the degradation of the mineral core. The presented results allow for predicting the degradation pathways of the carriers including the release profile of the loaded cargo under physiological conditions. The viability of 4T1 breast cancer cells with mineral magnetic carriers with protein-tannin shells was investigated, and their movement in the fields of action of the permanent magnet was shown.

Synthesis and physico-chemical properties of poly(N-vinyl pyrrolidone)-based hydrogels with titania nanoparticles.

Poly(N-vinyl pyrrolidone) (PVP)-based hydrogels with titania nanoparticles (TN) were synthesized by the sol-gel method for the first time and were characterized in different states (native, freeze-dried, air-dried to constant weight and ground to powder, or swollen to constant weight in H2O or D2O) by various methods such as wide-angle and small-angle X-ray and neutron scattering, neutron spin-echo (NSE) spectroscopy, and scanning electron microscopy. The static (static polymer-polymer correlation length (mesh size), associates of cross-links and PVP microchains) and dynamic (polymer chain relaxation rate, hydrodynamic polymer-polymer correlation length) structural elements were determined. The incorporation of titania nanoparticles into PVP hydrogel slightly increases the size of structural inhomogeneities (an increase in the static and dynamic polymer-polymer correlation length, the formation of associates of cross-links and PVP chains). Titania nanoparticles have an impact on the microstructure of the composite hydrogel and form associates with sizes from 0.5 to 2 µm attached to PVP hydrogel pore walls. The PVP and TN/PVP hydrogels show a high degree of water swelling. Moreover, the presence of titania nanoparticles in TN/PVP increases the number of water adsorption cycles compared to PVP hydrogel. The high swelling degree, bacteria-resistant and antimicrobial properties against Staphylococcus aureus allow considering NT/PVP hydrogels for medical applications as wound coatings.

Effects of Different Stimuli on the Structure of Nano-Anatase and Poly(N-vinylcaprolactam) in the Nano-Anatase/Poly(N-vinylcaprolactam) Composites.

Nanocomposites based on poly(N-vinylcaprolactam) containing functional nano-anatase particles were produced by mixing and mechanical grinding of mixtures of poly(N-vinylcaprolactam) and Hombifine N (nano-anatase) powders in a porcelain mortar (method 1) and by mechanical milling of the same powders using a high-energy planetary ball mill (method 2). Differences in the diffraction patterns of nanocomposites prepared by method 1 (partial crystallization and an amorphization of nano-anatase particles in the nano-anatase/poly(N-vinylcaprolactam) composite) and method 2 (amorphization of nano-anatase particles) were found. An increase in the X-ray intensity was found to cause physical degradation of the polymer in nano-anatase/poly(N-vinylcaprolactam) composites depending on its prehistory. The preparation of nanocomposites by method 2 was shown to increase photocatalytic activity in the degradation of the dye methyl orange under ultraviolet light irradiation.