Aurelia Vasile

Magnetic α-Fe2O3/MCM-41 nanocomposites: Preparation, characterization, and catalytic activity for methylene blue degradation

Catalysts based on nanosized magnetic iron oxide stabilized inside the pore system of ordered mesoporous silica MCM-41 have been prepared. The obtained materials were characterized by powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and N(2) adsorption-desorption isotherm. XRD analysis showed that the obtained materials consist from the pure hematite crystalline phase (α-Fe(2)O(3)) dispersed within ordered mesoporous silica MCM-41. Magnetic measurements show that the obtained nanocomposites exhibit at room temperature weak ferromagnetic behavior with slender hysteresis. The catalytic activity of the magnetic α-Fe(2)O(3)/MCM-41 nanocomposites was evaluated by the degradation of methylene blue (MB) aqueous solution. For this purpose, an ultrasound-assisted Fenton-like process was used. The effect of solution pH on degradation of MB was investigated. The results indicated that US-H(2)O(2)-α-Fe(2)O(3)/MCM-41 nanocomposite system is effective for the degradation of MB, suggesting its great potential in removal of dyes from wastewater. It was found that the degradation rate of MB increases with decrease in the pH value of the solution.

Investigations on nanoconfinement of low-molecular antineoplastic agents into biocompatible magnetic matrices for drug targeting

Magnetic mesoporous silica nanoparticles are employed as biocompatible matrices to host low-molecular antineoplastic drugs. 5-Fluorouracil is a well-known antimetabolite drug used to treat many malignancies: colon, rectal, breast, head and neck, pancreatic, gastric, esophageal, liver and G-U (bladder, penile, vulva, prostate), skin cancers (basal cell and keratosis). Unfortunately severe gastrointestinal, hematological, neural, cardiac and dermatological toxic effects are often registered due to its cytotoxicity. Thus, this work focuses on development of a magnetic silica nanosystem, capable of hosting high amounts of 5-fluorouracil and delivers it in a targeted manner, under the influence of external magnetic field. There are few reports on nanoconfinement of this particular small molecule antimetabolite on mesoporous silica hosts. Therefore we have investigated different ways to confine high amounts of 5-FU within amino-modified and non-modified mesopores of the silica shell, from water and ethanol, under magnetic stirring and ultrasound irradiation. Also, we have studied the adsorption process from water as a function of pH in order to rationalize drug-support interactions. It is shown that nature of the solvent has great influence on diffusion of small molecules into mesopores, which is slower from alcoholic solutions. More importantly, sonication is proven as an excellent alternative to long adsorption tests, since the time necessary to reach equilibrium is drastically reduced to 1h and higher amounts of drug may be immobilized within the mesopores of amino-modified magnetic silica nanoparticles. These results are highly important for optimization of drug immobilization process in order to attain desired release profile.

Calixarene-modified multi-wall carbon nanotubes

In order to improve the properties of carbon nanotubes, novel calixarene-modified multi-wall carbon nanotubes were prepared by using carbon nanotubes with carboxylic groups and various novel calixarene derivatives. This self-assembling process has allowed us to fabricate carbon nanotubes with functional organic molecules. The properties of the functionalized materials containing carbon nanotubes and calixarene derivatives were studied by using XRD, SEM, FTIR, DRS UV-VIS, and nitrogen adsorption isotherm at 77K.

Inhibition of bcl-2 and cox-2 Protein Expression after Local Application of a New Carmustine-Loaded Clinoptilolite-Based Delivery System in a Chemically Induced Skin Cancer Model in Mice

Our research has focused on in vitro and in vivo evaluations of a new Carmustine (BCNU)-loaded clinoptilolite-based delivery system. Two clinoptilolite ionic forms—hydrogen form (HCLI) and sodium form (NaCLI)—were prepared, allowing a loading degree of about 5–6 mg BCNU/g of zeolite matrix due to the dual porous feature of clinoptilolite. Clinoptilolite-based delivery systems released 35.23% of the load in 12 h for the BCNU@HCLI system and only 10.82% for the BCNU@NaCLI system. The BCNU@HCLI system was chosen to develop gel and cream semisolid dosage forms. The cream (C_BCNU@HCLI) released 29.6% of the loaded BCNU after 12 h in the Nylon synthetic membrane test and 31.6% in the collagen membrane test, higher by comparison to the gel. The new cream was evaluated in vivo in a chemically induced model of skin cancer in mice. Quantitative immunohistochemistry analysis showed stronger inhibition of B-cell lymphoma-2 (bcl-2) and cyclooxygenase 2 (cox-2) protein expression, known markers for cancer survival and aggressiveness, after the treatment with C_BCNU@HCLI by comparison to all the control treatment types, including an off-label magistral formula commercially available Carmustine cream as reference, bringing evidence that a clinoptilolite-based delivery systems could be used as a cancer drug carriers and controlled release systems (skin-targeted topical delivery systems).

Sonochemical Development of Magnetic Nanoporous Therapeutic Systems as Carriers for 5-Fluorouracil

Therapeutic nanosystems based on magnetic mesoporous silica nanoparticles are successfully obtained by a facile, reproducible and time-saving sonochemical method. Hydrophilic citrate-capped magnetite nanoparticles of about 20 nm are firstly prepared by ultrasound-assisted chemical precipitation. Secondly, freshly-dried magnetite nanoparticles are coated with mesoporous silica shell by sonochemically-modified Strober method. The applied procedure provides easily-separable, stable core-shell nanoparticles consisting of superparamagnetic Fe3O4 cores and mesoporous silica shell. SEM micrographs showed that core-shell nanoparticles are smaller than 400 nm, a prerequisite for biomedical applications by intravenous administrations. Further, these sonochemically prepared magnetic nanoparticles are employed as biocompatible matrices to host and deliver 5-fluorouracil, a highly-toxic low-molecular antimetabolite chemotherapeutic drug. For this, drug molecules are confined into unmodified and amino-modified mesopores of the silica shell by adsorption from alcoholic solutions. A detailed study was performed using XRD, N2-sorption measurements, SEM and FTIR spectroscopy with the primary goal of investigating possible structural, textural and morphological modifications aroused after pore-functionalization and drug nanoconfinement. Magnetic behavior of prepared therapeutic nanosystems is visualized using vibrating sample magnetometry (VSM). Finally, the release profile of 5-fluorouracil from the unmodified and amino-modified nanoparticulate magnetic matrices in PBS solution (pH 7.4) is followed by means of liquid chromatographic measurements. The HPLC method used for determination of 5-fluoruracil in releasing media was fully validated in house, in terms of specificity, linearity, precision, LOD and LOQ establishment.