Camelia Ungureanu

Eco-designed biohybrids based on liposomes, mint-nanosilver and carbon nanotubes for antioxidant and antimicrobial coating.

Noncovalent entities (consisting of liposomes, phyto-nanosilver and carbon nanotubes) with interesting properties were constructed by a green bottom-up method. Phytosynthesis of silver nanoparticles using the Mentha piperita extract combines the benefits of this herb with the interesting properties of silver. The obtained silver-based biohybrids showed antioxidant and antimicrobial properties that have been considerable improved in the presence of carbon nanotubes. Thus the eco-designed bioconstructs consisting of cholesterol-containing liposomes, phytonanosilver and carbon nanotubes exhibited high antioxidant activity (AA=90.8%) and have been shown to be strong biocides offering inhibition zone of 25mm against Escherichia coli and 23mm against Staphylococcus aureus and Enterococcus faecalis.

Improved antibacterial behavior of titanium surface with torularhodin–polypyrrole film

The problem of microorganisms attaching and proliferating on implants and medical devices surfaces is still attracting interest in developing research on different coatings based on antibacterial agents. The aim of this work is centered on modifying titanium (Ti) based implants surfaces through incorporation of a natural compound with antimicrobial effect, torularhodin (T), by means of a polypyrrole (PPy) film. This study tested the potential antimicrobial activity of the new coating against a range of standard bacterial strains: Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis and Pseudomonas aeruginosa. The morphology, physical and electrochemical properties of the synthesized films were assessed by SEM, AFM, UV-Vis, FTIR and cyclic voltammetry. In addition, biocompatibility of this new coating was evaluated using L929 mouse fibroblast cells. The results showed that PPy-torularhodin composite film acts as a corrosion protective coating with antibacterial activity and it has no harmful effect on cell viability.

Antimicrobial activity of the surface coatings on TiAlZr implant biomaterial

This study is devoted to antimicrobial activity of new surface coatings on TiAlZr. Ti alloys such as TiAlZr are used as implant biomaterials, but, despite the good behavior of such alloys in simulated conditions, bacterial infections appear after the introduction of an implant into the body. The infections are typically caused by the adherence and colonization of bacteria on the surfaces of the implants. The study presents preparation and surface morphology characterization of coatings obtained via anodizing, as well as biomimetic coatings with hydroxyapatite and silver ions with and without antibiotic. The percentage inhibition of Escherichia coli bacteria growth was evaluated for each of the studied coating, and a Trojan-horse model of silver nanoparticles (nAg) antibacterial activity at interface was proposed. Such coatings could be more important taking into account that antibacterial treatments with antibiotics are becoming less effective due to their intensive use.

Enhancing antimicrobial activity of TiO2/Ti by torularhodin bioinspired surface modification

Implant-associated infections are a major cause of morbidity and mortality. This study was performed using titanium samples coated by anodization with a titanium dioxide (TiO2) shielded nanotube layer. TiO2/Ti surface was modified by simple immersion in torularhodin solution and by using a mussel-inspired method based on polydopamine as bio adhesive for torularhodin immobilization. SEM analysis revealed tubular microstructures of torularhodin and the PDA ability to function as a catchy anchor between torularhodin and TiO2 surface. Corrosion resistance was associated with TiO2 barrier oxide layer and nano-organized oxide layer and the torularhodin surface modification does not bring significant changes in resistance of the oxide layer. Our results demonstrated that the torularhodin modified TiO2/Ti surface could effectively prevent adhesion and proliferation of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa. The new modified titanium surface showed good biocompatibility and well-behaved haemocompatibility. This biomaterial with enhanced antimicrobial activity holds great potential for future biomedical applications.

Centrifugal partition extraction, a new method for direct metabolites recovery from culture broth: case study of torularhodin recovery from Rhodotorula rubra.

Centrifugal partition extraction (CPE), close to centrifugal partition chromatography, put in contact in a continuous way two immiscible liquid phases. This work presents early experiments on CPE use for solid-liquid-liquid extraction. It was applied to the direct treatment of culture broth for metabolites recovery. Torularhodin is one of the carotenoid pigments produced by the yeast Rhodotorula sp., with a terminal carboxylic group considered nowadays as a powerful antioxidant to be included in food and drugs formulations. Torularhodin was extracted from Rhodotorula rubra ICCF 209 cells by CPE. The recovery of torularhodin reaches 74 μg/g of biomass i.e. 294 μg/L of culture medium. The efficiency of the extraction step increased with the operating flow rate. The extraction yield could reach 91% with a contact time lower than 2 min. A 300 mL apparatus allowed a feed at 90 mL/min. The technique is proposed for extraction or sample preparation before analysis.

Composite scaffolds based on silver nanoparticles for biomedical applications

This paper presents the synthesis, characterisation, and in vitro testing of homogenous and heterogeneous materials containing silver nanoparticles (nanoAg). Three types of antiseptic materials based on collagen (COLL), hydroxyapatite (HA), and collagen/hydroxyapatite (COLL/HA) composite materials were obtained. The synthesis of silver nanoparticles was realized by chemical reaction as well as plasma sputtering deposition. The use of chemical reduction allows the synthesis of homogenous materials while the plasma sputtering deposition can be easily used for the synthesis of homogeneous and heterogeneous support. Based on the in vitro assays clear antiseptic activity against Escherichia coli was relieved even at low content of nanoAg (10 ppm).

Green silver nanobioarchitectures with amplified antioxidant and antimicrobial properties

Cornelian silver-based architectures were achieved from liposomes, silver nanoparticles (AgNPs) and single-walled carbon nanotubes (SWCNTs) by a green bottom-up strategy. Liposomes were prepared by a thin film hydration method and labelled with a natural porphyrin extracted from spinach leaves, cholorophyll a (Chla). Due to its strong visible absorption and fluorescence emission, this phytopigment was used as a spectral sensor to monitor any possible changes occurring in lipid membranes caused by the action of various agents. An aqueous extract from Cornus mas L. fruits was used for AgNP phytosynthesis. Addition of appropriate amounts of phytonanosilver particles and SWCNTs to biomimetic membranes resulted in biohybrid material with good physical stability (ZP = -34 mV) and high antioxidant activity (AA = 97.8%). Moreover, they have been shown to be a strong biocide having diameters of inhibition zones of 18.3 mm, 23.8 mm and 21.6 mm against Escherichia coli ATCC 8738, Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212, respectively. Chla rapidly sensed the modifications that occurred in artificial lipid bilayers as a result of interactions with silver nanoparticles and carbon nanotube surfaces indicating the biohybrid formation, and these results were supported by AFM analysis. The bioconstructed hybrid material consisting of biomimetic membranes, phyto-nanosilver and SWCNTs could be applied as an antimicrobial and antioxidant coating.

Multifunctional soft hybrid bio-platforms based on nano-silver and natural compounds.

Novel nanohybrids consisting of nano-Ag, chitosan, lipids and phyto-compounds (chlorophyll a and curcumin) have been achieved through a simple bottom-up strategy, resulting in stable (ZP=-30.9mV) and spherical-shaped nano-entities with size <200nm (estimated by AFM analysis and DLS measurements). The formation of these biohybrids was monitored by absorption and emission spectroscopy, exploiting the spectral fingerprint of chlorophyll a. The bio-performances of these hybrid materials such as: high antioxidant activity (96.63%), strong biocidal properties against Escherichia coli ATCC 8738 (exhibiting an inhibition zone diameter of 32mm), hemocompatibility, in vitro cytotoxicity against HT-29 cancer cells and no toxicity to normal cells (in the biohybrid concentration range of 5.7-17%), make them promising candidates in bio-applications (antimicrobial and antioxidant coating, cancer treatment).

Electrochemical and Antibacterial Performance of CoCrMo Alloy Coated with Hydroxyapatite or Silver Nanoparticles

This paper presents a comparative study of antimicrobial and electrochemical performance of CoCrMo alloy surface treated with hydroxyapatite coating or silver nanoparticles (nAg) in the presence/absence of albumin addition. Nanoparticles dimension was quantified using dynamic light scattering. Antibacterial activity was evaluated by a spread plate method, while electrochemical characterization of CoCrMo samples coated and uncoated was studied by open circuit potential and cyclic polarization experiments. Furthermore, all surface coatings characterization was investigated by transmission electron microscopy, scanning electron spectroscopy, and energy-dispersive x-ray spectroscopy. The highest corrosion rate in simulated body solution (SBF) is for untreated CoCrMo alloy, and the lowest value is for CoCrMo alloy treated with nAg after addition in SBF of 80xa0g/L albumin. Only the surface treated with nAg has antibacterial effect.

Improving Natural Biopolymeric Membranes Based on Chitosan and Collagen for Biomedical Applications Introducing Silver

The aim of this study was to obtain new films based on collagen-chitosan with and without silver for biomedical applications. Membranes with a thin transparent elastic structure were obtained and after immersion in silver nitrate new membranes with silver have been elaborated and their physicochemical properties were assessed using infrared spectroscopy as well as contact angle determinations, and sorption properties. The water absorption has permitted the evaluation of the diffusion coefficient for modified collagen membranes and the values were comparable with diffusion coefficient specific for human cornea. Adsorption and desorption studies of silver ions were investigated based on the concentration of the silver solution. This concentration was determined by an inductively coupled plasma spectrometer. Antimicrobial investigations performed on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria and hemolytic properties assays have been evaluated measuring optical density. The enhancement of antibacterial activity of membranes with silver content was emphasized.