Graphene Nanoplatelets Render Poly(3-Hydroxybutyrate) a Suitable Scaffold to Promote Neuronal Network Development

The use of composite biomaterials as innovative bio-friendly neuronal interfaces has been poorly developed so far. Smart strategies to target neuro-pathologies are currently exploiting the mixed and complementary characteristics of composite materials to better design future neural interfaces. Here we present a polymer-based scaffold that has been rendered suitable for primary neurons by embedding graphene nanoplatelets (GnP). In particular, the growth, network formation, and functionality of primary neurons on poly(3-hydroxybutyrate) [P(3HB)] polymer supports functionalized with various concentrations of GnP were explored. After growing primary cortical neurons onto the supports for 14 days, all specimens were found to be biocompatible, revealing physiological growth and maturation of the neuronal network. When network functionality was investigated by whole patch-clamp measurements, pure P(3HB) led to changes in the action potential waveform and reduction in firing frequency, resulting in decreased neuronal excitability. However, the addition of GnP to the polymer matrix restored the electrophysiological parameters to physiological values. Interestingly, a low concentration of graphene was able to promote firing activity at a low level of injected current. The results indicate that the P(3HB)/GnP composites show great potential for electrical interfacing with primary neurons to eventually target central nervous system disorders.

POLYMERIC SUPPORTS FOR ENZYMES IMMOBILIZATION IN SYNTHESIS OF BIOLOGICALLY ACTIVE COMPOUNDS

The report presents the synthesis of biocatalysts based on horseradish peroxidase immobilized on commercially available polymeric supports: hyper cross-linked polystyrene MN-100 and Sepabeads EC-HA. The immobilization was carried out by covalent crosslinking of the enzyme with the support using glutaraldehyde. The optimal amount of glutaraldehyde for covalent binding of HRP was found to be 0.2 g/l. The peroxidase/MN-100 and peroxidase/Sepabeads EC-HA biocatalysts presented in the work showed good activity in the oxidation of 2-methylnaphthol to 2 methyl-1,4-naphthohydroquinone (vitamin K4). The biocatalyst based on MN-100 showed higher activity compared to the biocatalyst based on Sepabeads EC-HA, which is likely due to the different surface structure of the original polymer supports. The samples retained their activity in ten consecutive reuses. The high reusability of peroxidase/MN-100 and peroxidase/Sepabeads EC-HA is explained by the high sorption ability of commercial polymer supports MN-100 and Sepabeads EC-HA and the formation of strong covalent bonds between the enzyme and the support. The optimal conditions for the oxidation of 2-methylnaphthol to 2-methyl-1,4-naphthohydroquinone using synthesized biocatalytic systems were also selected. The temperature of 40 °C and pH 7.2 were found to be optimal for the oxidation of the proposed substrate. The presented results will undoubtedly make a positive contribution to the development of the chemical and pharmaceutical industry.

Micellar Organocatalysis Using Smart Polymer Supports: Influence of Thermoresponsive Self-Assembly on Catalytic Activity

Micellar catalysts with a switchable core are attractive materials in organic synthesis. However, little is known about the role of the shell forming block on the performance of the catalyst. Thermoresponsive block copolymers based on poly(N-isopropylacrylamide-co-vinyl-4,4-dimethylazlactone) attached to different permanently hydrophilic blocks, namely poly(ethylene glycol), poly(N,N-dimethylacrylamide), and poly(2,3-dihydroxypropyl acrylate), were successfully synthesized via reversible addition/fragmentation chain transfer radical polymerization (RAFT). Post-polymerization attachment of an amino-functionalized L-prolineamide using the azlactone ring-opening reaction afforded functionalized thermoresponsive block copolymers. Temperature-induced aggregation of the functionalized block copolymers was studied using dynamic light scattering. It was shown that the chemical structure of the permanently hydrophilic block significantly affected the size of the polymer self-assemblies. The functionalized block copolymers were subjected to an aldol reaction between p-nitrobenzaldehyde and cyclohexanone in water. Upon temperature-induced aggregation, an increase in conversion was observed. The enantioselectivity of the polymer-bound organocatalyst improved with an increasing hydrophilic/hydrophobic interface as a result of the different stability of the polymer aggregates.

Catalytic Disproportionation of Chlorosilanes Using Imidazolium Ionic Liquids Deposited on Polymer Supports

Highly selective catalytic systems with porous polymer supports immobilized with ionic liquids, which contained acceptor and donor substituents as well as various anions, were developed. Their effect on activity of the catalysts in disproportionation of trichlorosilane was studied. The catalytic activity of systems based on N-methoxy-4-methylimidazole with different counterions was shown to decrease with the growth of chemical activity of the anions from iodine to fluorine.

Biotechnological method of obtaining nanoparticles of silver, cadmium and zinc sulfides. Physico-chemical characteristics. Creation of polymeric nanocomposites

A simple and environmentally safe method for obtaining stable nanoparticles of metal sulfides nanoparticles – NpAg2S, NpCdS and NpZnS was developed using different strains of microorganisms in an aqueous solution of metal salts and sulfur sources at the Research Center "Kurchatov Institute" – GosNIIgenetika. The concentration of nanoparticles is 1–4 mg/ml in aqueous suspensions. Using of the methods of electron microscopy, spectrofluorimetry, dynamic light scattering determined the main characteristics of biogenic nanoparticles: shape, size distribution, crystal structure, effective diameter, luminescent spectrum, zeta potential. According to its characteristics, these nanoparticles are referred to quantum dots. It is established that the stability of nanoparticles in aqueous suspensions is due to protein molecules adsorbed on the surface of nanoparticles, which are supplied by cells of microorganisms. Effective immobilization of biogenic nanoparticles on the surface of various polymer supports has been carried out. Biogenic nanoparticles along with nanoparticles obtained by physico-chemical methods can be used as fluorophores for imaging of biological processes, also as photocatalysts, solar cells and for new nanocomposite materials.

Histopathologic Evaluation of Polymer Supports for Pintucci-Type Keratoprostheses: an Animal Study

Purpose: To report histopathological findings for different types of polymers proposed as support for a Pintucci-type keratoprosthesis. Methods: Six polymers, including three types of polyesters (#1-3), one type of polytetrafluoroethylene (PTFE, #4), polyethylene (#5), and expanded polytetrafluoroethylene (ePTFE, #6) were evaluated. Four samples of each material were placed under the orbicularis oculi muscles of 12 rabbits. After five weeks, the samples were removed and evaluated histopathologically. Fibrovascular tissue ingrowths were investigated in terms of tissue penetration depth into the materials (graded as none, mild, moderate, and intense) and fibrovascular ingrowth area at the ultimate level of tissue penetrance. ImageJ software was used to calculate fibrovascular tissue area between the material fibers, and the mean area values were compared between the materials. Results: Polyester materials #1 and #3 demonstrated intense fibrovascular tissue penetration with a large fibrovascular ingrowth area; no overt tissue ingrowth was observed into material #6. The mean area of penetrated fibrovascular tissues was significantly different between materials (P < 0.001). Materials #2, #4, and #5 showed moderate fibrovascular tissue ingrowth and the area of presented fibrovascular tissue at the paracentral parts of material #4 was significantly smaller than that of materials #1 (P = 0.02) and #3 (P = 0.01). Conclusion: Two polyester materials that had relatively large pore sizes demonstrated a deep and large area of fibrovascular ingrowth. Given that material #3 is thicker and more consistent than material #1, the former can be used as the appropriate material for supporting the Pintucci-type keratoprosthesis.