Rayna Bryaskova

Synthesis, characterisation and antibacterial activity of PVA/TEOS/Ag-Np hybrid thin films

Novel hybrid material thin films based on polyvinyl alcohol (PVA)/tetraethyl orthosilicate (TEOS) with embedded silver nanoparticles (AgNps) were synthesized using sol-gel method. Two different strategies for the synthesis of silver nanoparticles in PVA/TEOS matrix were applied based on reduction of the silver ions by thermal annealing of the films or by preliminary preparation of silver nanoparticles using PVA as a reducing agent. The successful incorporation of silver nanoparticles ranging from 5 to 7nm in PVA/TEOS matrix was confirmed by TEM and EDX analysis, UV-Vis spectroscopy and XRD analysis. The antibacterial activity of the synthesized hybrid materials against etalon strains of three different groups of bacteria -Staphylococcus aureus (gram-positive bacteria), Escherichia coli (gram-negative bacteria), Pseudomonas aeruginosa (non-ferment gram-negative bacteria) has been studied as they are commonly found in hospital environment. The hybrid materials showed a strong bactericidal effect against E. coli, S. aureus and P. aeruginosa and therefore have potential applications in biotechnology and biomedical science.

A novel pH sensitive water soluble fluorescent nanomicellar sensor for potential biomedical applications

Herein we report on the synthesis and sensor activity of a novel pH sensitive probe designed as highly water-soluble fluorescent micelles by grafting of 1,8-naphthalimide-rhodamine bichromophoric FRET system (RNI) to the PMMA block of a well-defined amphiphilic diblock copolymer-poly(methyl methacrylate)-b-poly(methacrylic acid) (PMMA48-b-PMAA27). The RNI-PMMA48-b-PMAA27 adduct is capable of self-assembling into micelles with a hydrophobic PMMA core, containing the anchored fluorescent probe, and a hydrophilic shell composed of PMAA block. Novel fluorescent micelles are able to serve as a highly sensitive pH probe in water and to internalize successfully HeLa and HEK cells. Furthermore, they showed cell specificity and significantly higher photostability than that of a pure organic dye label such as BODIPY. The valuable properties of the newly prepared fluorescent micelles indicate the high potential of the probe for future biological and biomedical applications.

Antibacterial activity of poly(vinyl alcohol)-b-poly(acrylonitrile) based micelles loaded with silver nanoparticles

A new amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) (PVOH-b-PAN) copolymer obtained by selective hydrolysis of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) copolymer synthesized by cobalt mediated radical polymerization was used for the preparation of PVOH-b-PAN based micelles with embedded silver nanoparticles. The successful formation of silver loaded micelles has been confirmed by UV-vis, DLS and TEM analysis and their antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and spore solution of Bacillus subtilis (B. subtilis) has been studied. PVOH-b-PAN based micelles with embedded silver nanoparticles showed a strong bactericidal effect against E. coli, S. aureus and P. aeruginosa and the minimum bactericidal concentration for each system (MBC) has been determined.

Novel nanosized water soluble fluorescent micelles with embedded perylene diimide fluorophores for potential biomedical applications: Cell permeability, localization and cytotoxicity

Novel biocompatible water-soluble fluorescent micelles with embedded perylene diimides (PDI) for intracellular applications have been prepared by self assembling of amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) (PVA-b-PAN) copolymers in the presence of synthesized fluorophores. Amphiphilic PVA-b-PAN copolymers were obtained by selective hydrolysis of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) (PVAc-b-PAN) copolymer. The preparation of the novel fluorescence micelles consisting of PVA hydrophilic shell and PAN hydrophobic core with incorporated PDI fluorophores has been confirmed by DLS and TEM analysis. The cytotoxicity of the water-soluble fluorophores and their internalization into living cells depending on the micellar concentration have been tested. It was shown that they could successfully enter in living cells without destroying their morphology. The results obtained indicate that the novel water-soluble fluorescent micelles with embedded PDI fluorophores would be suitable for potential intracellular biomedical applications.

Gold-loaded carbon nanoparticles from poly(vinyl alcohol)-b-poly(acrylonitrile) non-shell-cross-linked micelles

Herein we show that a new amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) block copolymer dispersed in water can be easily loaded with gold nanoparticles by addition of chlorauric acid followed by reduction by sodium borohydride. After deposition of the so-loaded micelles onto a silicon wafer, followed by an appropriate thermal treatment, the poly(acrylonitrile) core of the micelles is carbonized, while the poly(vinyl alcohol) shell is completely decomposed and volatilized, leading to gold encapsulated in carbon nanoparticles. The morphology of the micelles is maintained during thermal treatment without requiring shell-cross-linking of the micelles prior to pyrolysis.

Immobilization of Trichosporon Cutaneum R57 on PVA/TEOS/MPTEOS Hybrid Matrices for Removal of Manganese Ions

ABSTRACT New hybrid materials based on polyvinyl alcohol (PVA), 3-mercaptopropyltriethoxysilane (MPTEOS) and tetraethoxysilane (TEOS) were prepared, using a sol-gel process. Thermogravimetric analysis (TGA) was performed to determine the thermal stability of the hybrid materials. MPTEOS, as a precursor, ensured the presence of SH-groups, thus providing additional binding places for cell immobilization. Based on good adhesive behavior, the hybrid materials were tested as matrices for immobilization of Trichosporon cutaneum R57 for removal of manganese ions from aqueous solutions. Maximum Mn2+ removal was achieved by cells immobilized onto materials with higher MPTEOS concentration. The synthesized PVA/TEOS/MPTEOS hybrid materials proved to be efficient for use in biosorption applications.

PVA -based Hybrid Materials for Immobilization of Trichosporon cutaneum R57 Efficient in Removal of Chromium Ions

New hybrid materials based on polyvinyl alcohol (PVA) and γ-aminopropyltriethoxyxilane (APTEOS), 3-mercaptopropyltriethoxysilane (MPTEOS) and tetraethoxysilane (TEOS) were prepared. To determine the thermal stability of the hybrid materials, thermogravimetric analysis (TGA) was performed. The new materials were tested for biofilm formation and biosorption studies. They were tested as matrices for immobilization of Trichosporon cutaneum R57 capable to remove Cr(VI) from aqueous solutions. The use of APTEOS and MPTEOS as precursors, incorporated new NH– and SH– bonds, which ensured additional binding places for cells immobilization. The presence of SH– and NH– groups in the hybrid matrices resulted in apparently higher Cr(VI) sorption capacity of the immobilized Tr. cutaneum R57 cells due to the incorporation of additional adsorption sites in the matrix through the PVA functionalities. The synthesized PVA/APTEOS materials proved efficient for use in biosorption applications.