Dan Eduard Mihaiescu

Inhibitory Activity of

Undesired biofilm development is a major concern in many areas, especially in the medical field. The purpose of the present study was to comparatively investigate the antibiofilm efficacy of usnic acid, in soluble versus nanofluid formulation, in order to highlight the potential use of Fe3O4/oleic acid (FeOA) nanofluid as potential controlled release vehicle of this antibiofilm agent. The (+) -UA loaded into nanofluid exhibited an improved antibiofilm effect on S. aureus biofilm formation, revealed by the drastic decrease of the viable cell counts as well as by confocal laser scanning microscopy images. Our results demonstrate that FeOA nanoparticles could be used as successful coating agents for obtaining antibiofilm pellicles on different medical devices, opening a new perspective for obtaining new antimicrobial and antibiofilm surfaces, based on hybrid functionalized nanostructured biomaterials.

{\rm Fe}_{3} {\rm O}_{4}

Preparation and characterization of CS/Fe(3)O(4)/CMC composite scaffolds including the morphology, crystallinity, and the in vitro efficacy as antibiotic delivery vehicles as well as their influence on the eukaryotic cells are reported. The results demonstrated that the magnetic polymeric composite scaffolds are exhibiting structural and functional properties that recommend them for further applications in the biomedical field. They improve the activity of currently used antibiotics belonging to penicillins, macrolides, aminoglycosides, rifampicines and quinolones classes, representing potential macromolecular carriers for these antimicrobial substances, to achieve extracellular and intracellular targets. The obtained systems are not cytotoxic and do not influence the eukaryotic HCT8 cell cycle, representing potential tools for the delivery of drugs in a safe, effective and less expensive manner.

/Oleic Acid/Usnic Acid—Core/Shell/Extra-Shell Nanofluid on S. aureus Biofilm Development

During the present study, we have evaluated magnetic chitosan as a potential drug delivery device, by specifically determining if chitosan could elute antibiotics in an active form that would be efficacious in inhibiting Staphylococcus aureus and Escherichia coli growth. We have demonstrated that the incorporation of cephalosporins of second, third and fourth generation into magnetic chitosan microspheres can possibly lead to an improved delivery of antibiotics in active forms, probably due to the inherent properties of chitosan.

Synthesis, characterization and in vitro assessment of the magnetic chitosan–carboxymethylcellulose biocomposite interactions with the prokaryotic and eukaryotic cells

The aim of the present study was to demonstrate that Fe3O4/oleic acid core/shell nanostructures could be used as systems for stabilizing the Eugenia carryophyllata essential oil (EO) on catheter surface pellicles, in order to improve their resistance to fungal colonization. EO microwave assisted extraction was performed in a Neo-Clevenger (related) device and its chemical composition was settled by GC-MS analysis. Fe3O4/oleic acid-core/shell nanoparticles (NP) were obtained by a precipitation method under microwave condition. High resolution transmission electron microscopy (HR-TEM) was used as a primary characterization method. The NPs were processed to achieve a core/shell/EO coated-shell nanosystem further used for coating the inner surface of central venous catheter samples. The tested fungal strains have been recently isolated from different clinical specimens. The biofilm architecture was assessed by confocal laser scanning microscopy (CLSM). Our results claim the usage of hybrid nanomaterial (core/shell/coated-shell) for the stabilization of E. carryophyllata EO, which prevented or inhibited the fungal biofilm development on the functionalized catheter, highlighting the opportunity of using these nanosystems to obtain improved, anti-biofilm coatings for biomedical applications.

Improved antibacterial activity of cephalosporins loaded in magnetic chitosan microspheres

Abstract The flow-vacuum pyrolyses of 10H-dibenzo[ a,d ]cyclohepten-10-one ( 9 ); 5H-11,12-dihydrodibenzo[ a,d ]cycloocten-10-one ( 10 ) and 11,12-dihydro-6H-dibenzo[ a,e ]cycloocten-5-one ( 11 ) were studied by GC/MS at 1.33 mbar and temperatures between 600 and 900°C. The ketone 9 affords anthracene and small amounts of anthrone. The product distributions of ketones 10 and 11 are very similar: besides anthracene (major product) and 9-methyl-anthracene (minor product) the 5H-10,11-dihydro-dibenzo[ a,d ]cycloheptene ( 2 ) was formed as an isolable intermediate. Trahanovskys pyrolysis mechanism (including spiranes and bridged diradicals) suggested for dibenzosuberones and dibenzocyclooctanes can be extended to ketones 9 – 11 (as well as to hydrocarbon 2 ). Consideration of enantiomeric spiranes as intermediates can conduct to a better understanding of the reaction mechanism.

Hybrid Nanomaterial for Stabilizing the Antibiofilm Activity of Eugenia carryophyllata Essential Oil

The aim of this study was to investigate the effect of different hybrid inorganic-organic micro- and nanomaterials (Fe(3)O(4)/PEG(600), Fe(3)O(4)/C(12), ZSM-5) on the antibacterial activity of different cephalosporins against Gram-positive and Gram-negative bacterial strains. The synergic effect of the studied materials was demonstrated by the increase in the growth inhibition zones diameter. All tested hybrid micro- and nanomaterials increased the activity of cefotaxime against Staphylococcus aureus. ZSM-5 increased the activity of cefotaxime and ceftriaxone and Fe(3)O(4)/C(12) that of ceftriaxone against Pseudomonas aeruginosa and S. aureus. The anti-Pseudomonas, anti-Klebsiella pneumoniae and anti-Bacillus subtilis activity of cefoperazone was increased by Fe(3)O(4)/C(12) nanoparticles, while the ZSM-5 improved its anti-Escherichia coli, K. pneumoniae, S. aureus and B. subtilis activity, whereas Fe(3)O(4)/PEG(600) against K. pneumoniae. The anti-K. pneumoniae activity of cefepime was increased by all tested nanoparticles, whereas its anti-B. subtilis and anti-E. coli activity was improved by Fe(3)O(4)/C(12) and Fe(3)O(4)/PEG(600) nanoparticles. In conclusion, both magnetic Fe(3)O(4) nanoparticles, charged outside as extra-shell with the antibiotic as well as ZSM-5 microparticles carrying the antibiotic inside the pores, significantly and specifically improved cephalosporin efficacy. A probable explanation for the increase in the antibiotic efficiency is the better penetration through the cellular wall of the antibiotic charged nanoparticles.

Flow-vacuum pyrolysis of three dibenzocycloalkanones

A layer-by layer technique was successfully used to obtain collagen/hydroxyapatite-magnetite-cisplatin (COLL/HAn-Fe3O4-CisPt, n=1–7) composite materials with a variable content of hydroxyapatite intended for use in the treatment of bone cancer. The main advantages of this system are the possibility of controlling the rate of delivery of cytostatic agents, the presence of collagen and hydroxyapatite to ensure more rapid healing of the injured bone tissue, and the potential for magnetite to be a passive antitumoral component that can be activated when an appropriate external electromagnetic field is applied. In vitro cytotoxicity assays performed on the COLL/HAn-Fe3O4-CisPt materials obtained using a layer-by layer method confirmed their antitumoral activity. Samples with a higher content of hydroxyapatite had more antitumoral activity because of their better absorption of cisplatin and consequently a higher amount of cisplatin being present in the matrices.

Influence of hybrid inorganic/organic mesoporous and nanostructured materials on the cephalosporins' efficacy on different bacterial strains

“C.D. Nenitzescu” - Institute of Organic Chemistry, Romanian Academy, Splaiul Independentei 202B,71141 Bucharest, RomaniaTel.: (401)-6383665, Fax: (401)-3121601, E-mail: draghici@ccoux.cco.roReceived: 28 January 2000; revised form 21 July 2000 / A ccepted: 1 August 2000 / Published: 9 A ugust 2000Abstract: FVP of the title oxazole (1) at 1000